HK40004114B

HK40004114B - Rach conveyance of dl synchronization beam information for various dl-ul correspondence states

Info

Publication number: HK40004114B
Application number: HK19127563.5A
Authority: HK
Inventors: M‧N‧伊斯兰; S‧萨布拉马尼安; J‧李; N‧阿贝迪尼; B‧萨迪格
Original assignee: 高通股份有限公司
Priority date: 2016-08-12
Filing date: 2017-08-11
Publication date: 2022-11-04

Description

RACH conveyance of DL synchronization beam information for various DL-UL correspondence states

Cross-referencing

This patent application claims U.S. patent application No.15/674,214 entitled "RACH Conveyance of DL Synchronization Beam Information For Various DL-UL Correspondence States" filed by Islam et al on 8/10 2017, and U.S. provisional patent application No.62/374,735 entitled "RACH Conveyance of DL Synchronization Beam Information For Various DL-UL Reciprocity States (RACH communication of DL Synchronization Beam Information For Various DL-UL Reciprocity States)" filed by Islam et al on 8/12 2016, and U.S. provisional patent application No.62/374,735 entitled "RACH Conveyance of DL Synchronization Beam Information For Various DL-UL Reciprocity States" filed by Islam et al on 24, and U.S. provisional patent application No.62/379,209 entitled "RACH Conveyance of DL Synchronization Beam Information For Various DL-UL Reciprocity States" filed by Islam et al on 2016 8/24, And U.S. provisional patent application No.62/406,377 entitled "RACH Conveyance of DL Synchronization Beam Information For Various DL-UL Reciprocity States" filed by Islam et al on 10/2016, and U.S. provisional patent application No.62/407,423 entitled "RACH Conveyance of DL Synchronization Beam Information For Various DL-UL Reciprocity States" filed by Islam et al on 10/12/2016, and U.S. provisional patent application No.62/407,423 entitled "RACH Conveyance of DL Synchronization Beam Information For Various DL-UL Reciprocity States" filed by Islam et al on 11/4, and U.S. provisional patent application No.62/418,072 entitled "RACH Conveya of DL Synchronization Beam Information For Various DL-UL Reciprocity States" filed by Islam et al on 4/2016, each of which is assigned to the assignee of the present application.

Technical Field

The following generally relates to wireless communications and more particularly to Random Access Channel (RACH) communication of Downlink (DL) synchronization beam information for various downlink-uplink (DL-UL) correspondence states.

Background

Wireless communication systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be able to support communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, and Orthogonal Frequency Division Multiple Access (OFDMA) systems (e.g., Long Term Evolution (LTE) systems). A wireless multiple-access communication system may include several base stations, each of which simultaneously supports communication for multiple communication devices, which may otherwise be referred to as User Equipment (UE).

Wireless communication systems may operate in the millimeter wave (mmW) frequency range (e.g., 28GHz, 40GHz, 60GHz, etc.). Wireless communication at these frequencies may be associated with increased signal attenuation (e.g., path loss), which may be affected by various factors, such as temperature, barometric pressure, diffraction, and the like. As a result, signal processing techniques (such as beamforming) can be used to coherently combine the energy and overcome the path loss at these frequencies. Due to the increased amount of path loss in mmW communication systems, transmissions from base stations and/or UEs may be beamformed.

Wireless communication between two wireless nodes (e.g., between a base station and a UE) may use beamformed or beamformed signals for transmission and/or reception. The base station may transmit a beamformed synchronization signal on a Downlink (DL) synchronization beam. The UE may receive synchronization signals on one or more of the DL synchronization beams and thus be able to initiate a RACH procedure with the base station. In some instances, the UE may send a message to the base station as part of a RACH procedure, and the base station may assume that the Uplink (UL) beam on which the RACH message was received represents the DL beam that the base station should use in communicating with the UE. In other words, the base station assumes a DL-UL correspondence. However, for various reasons, the correspondence between DL and UL channels may be lost. Thus, the base station assumption may not be correct, which means that the DL beam selected by the base station may not be the most appropriate beam for communicating with the UE.

Disclosure of Invention

The described technology relates to improved methods, systems, devices, or apparatuses (equipment) to support RACH communication of DL beam information for various DL-UL correspondence states. In general, the described techniques provide for a base station to transmit a DL signal to a UE. The DL signal may be transmitted on the DL beam(s). The UE may use a DL beam from among the DL beam(s) that may be used for communication (e.g., DL communication) with the base station. The UE may select a resource and/or a Random Access Channel (RACH) waveform for transmitting a RACH message (e.g., RACH message 1(msg1) or RACH message 3(msg3) to the base station). In some aspects, the UE may select a resource and/or RACH waveform based on the DL beam. The UE may transmit the RACH message to the base station on the selected resource and/or RACH waveform. The base station may receive the RACH message on the resource and/or RACH waveform and identify a DL beam selected by the UE based on the resource and/or RACH waveform. The base station may use the selected DL beam for subsequent communications with the UE.

A method of wireless communication is described. The method can comprise the following steps: the method generally includes receiving a Downlink (DL) signal from a base station on one or more DL beams, identifying characteristics of a correspondence between one or more receive beams at the UE and one or more transmit beams at the UE, identifying a selected DL beam of the one or more DL beams for communication from the base station to the UE, and transmitting a Random Access Channel (RACH) message to the base station using at least one of a resource or a RACH waveform selected based at least in part on the characteristics of the selected DL beam and the correspondence.

An apparatus for wireless communication is described. The apparatus may include: the apparatus generally includes means for receiving a Downlink (DL) signal from a base station on one or more DL beams, means for identifying characteristics of a correspondence between one or more receive beams at the UE and one or more transmit beams at the UE, means for identifying a selected DL beam of the one or more DL beams for communication from the base station to the UE, and means for transmitting a Random Access Channel (RACH) message to the base station using at least one of a resource or a RACH waveform selected based at least in part on the selected DL beam and the characteristics of the correspondence.

Another apparatus for wireless communication is described. The apparatus may include a processor, a memory in electronic communication with the processor, and instructions stored in the memory. The instructions are operable to cause the processor to: the method generally includes receiving a Downlink (DL) signal from a base station on one or more DL beams, identifying characteristics of a correspondence between one or more receive beams at the UE and one or more transmit beams at the UE, identifying a selected DL beam of the one or more DL beams for communication from the base station to the UE, and transmitting a Random Access Channel (RACH) message to the base station using at least one of a resource or a RACH waveform selected based at least in part on the characteristics of the selected DL beam and the correspondence.

A non-transitory computer-readable medium for wireless communication is described. The non-transitory computer-readable medium may include instructions operable to cause a processor to: the method generally includes receiving a Downlink (DL) signal from a base station on one or more DL beams, identifying characteristics of a correspondence between one or more receive beams at the UE and one or more transmit beams at the UE, identifying a selected DL beam of the one or more DL beams for communication from the base station to the UE, and transmitting a Random Access Channel (RACH) message to the base station using at least one of a resource or a RACH waveform selected based at least in part on the characteristics of the selected DL beam and the correspondence.

In some examples of the methods, apparatus, and non-transitory computer-readable media described above, the resource comprises a time resource, a frequency resource, or a time-frequency resource.

In some examples of the above-described methods, apparatus, and non-transitory computer-readable media, the RACH message comprises RACH message 1(msg 1).

In some examples of the methods, apparatuses, and non-transitory computer-readable media described above, the characteristic of the correspondence includes at least one of: a full correspondence, partial correspondence, or correspondence may be missing.

Some examples of the above-described methods, apparatus (devices), and non-transitory computer-readable media may further include processes, features, devices, or instructions for determining that there may be an exact correspondence. Some examples of the above-described methods, apparatus (devices), and non-transitory computer-readable media may further include processes, features, devices, or instructions for selecting a resource or RACH waveform for transmitting a RACH message to a base station based at least in part on the full correspondence, wherein a DL beam is mapped to the resource or the RACH waveform.

Some examples of the above-described methods, apparatus (devices), and non-transitory computer-readable media may further include processes, features, devices, or instructions for determining that there may be partial correspondence or no correspondence. Some examples of the above-described methods, apparatus (devices), and non-transitory computer-readable media may further include processes, features, devices, or instructions for selecting a transmission time for transmitting a RACH waveform of a RACH message to a base station based at least in part on the partial correspondence or no correspondence, wherein the transmission time includes a symbol of a corresponding random access subframe.

Some examples of the above-described methods, apparatus (devices), and non-transitory computer-readable media may further include processes, features, devices, or instructions for determining that partial correspondence may exist. Some examples of the methods, apparatus (devices), and non-transitory computer-readable media described above may further include processes, features, means, or instructions for selecting a transmission time for transmitting a RACH message to a base station based at least in part on the partial correspondence, wherein the transmission time includes a plurality of symbols of a corresponding random access subframe.

Some examples of the above-described methods, apparatus (devices), and non-transitory computer-readable media may further include processes, features, devices, or instructions for determining that there may be partial correspondence or no correspondence. Some examples of the methods, apparatus (devices), and non-transitory computer-readable media described above may further include processes, features, means, or instructions for transmitting multiple instances of the RACH message to a base station based at least in part on the partial correspondence or no correspondence, wherein the multiple instances of the RACH message are transmitted prior to receiving a subsequent message from the base station.

Some examples of the above-described methods, apparatus (devices), and non-transitory computer-readable media may further include processes, features, devices, or instructions for selecting a resource or RACH waveform based at least in part on characteristics of symbols and corresponding relationships associated with DL signals.

Some examples of the above-described methods, apparatus (devices), and non-transitory computer-readable media may further include processes, features, devices, or instructions for selecting one or more of a transmission time, a frequency range, or a RACH preamble for transmitting a RACH message based at least in part on characteristics of the correspondence.

In some examples of the methods, apparatus, and non-transitory computer-readable media described above, the selected resource or RACH waveform includes: selecting the resource or RACH waveform based at least in part on an index of the selected DL beam.

Some examples of the above-described methods, apparatus (devices), and non-transitory computer-readable media may further include processes, features, devices, or instructions for, when a correspondence between one or more receive beams at the UE and one or more transmit beams at the UE may be missing, the missing correspondence being associated with one or more receive beams having different channel propagation characteristics than the one or more transmit beams.

Some examples of the above-described methods, apparatus (devices), and non-transitory computer-readable media may further include processes, features, devices, or instructions for transmitting an indication of a characteristic of the correspondence, including: transmitting on a Physical Uplink Control Channel (PUCCH) or a Physical Uplink Shared Channel (PUSCH) during a first symbol of a first random access subframe and a second symbol of a second random access subframe.

Some examples of the above-described methods, apparatus (devices), and non-transitory computer-readable media may further include processes, features, devices, or instructions for mapping receive beams used for transmitting channel state information reference signals (CSI-RS) to transmit beams used for transmitting Sounding Reference Signals (SRS), or mapping transmit beams used for transmitting SRS to receive beams used for transmitting CSI-RS.

Some examples of the above-described methods, apparatus (devices), and non-transitory computer-readable media may further include processes, features, devices, or instructions for mapping a receive beam used in DL beam training to an UL beam used in UL beam training or mapping an UL beam used in UL beam training to a DL beam used in DL beam training.

Some examples of the above-described methods, apparatus (devices), and non-transitory computer-readable media, the DL signal comprises a synchronization signal or a reference signal.

A method of wireless communication is described. The method can comprise the following steps: the method generally includes identifying a characteristic of a correspondence between one or more receive beams at the UE and one or more transmit beams at the UE, and transmitting a Random Access Channel (RACH) message to a base station based at least in part on the characteristic of the correspondence.

An apparatus for wireless communication is described. The apparatus may include: the apparatus generally includes means for identifying a characteristic of a correspondence between one or more receive beams at the UE and one or more transmit beams at the UE, and means for transmitting a Random Access Channel (RACH) message to a base station based at least in part on the characteristic of the correspondence.

Another apparatus for wireless communication is described. The apparatus may include a processor, a memory in electronic communication with the processor, and instructions stored in the memory. The instructions are operable to cause the processor to: the method generally includes identifying a characteristic of a correspondence between one or more receive beams at the UE and one or more transmit beams at the UE, and transmitting a Random Access Channel (RACH) message to a base station based at least in part on the characteristic of the correspondence.

A non-transitory computer-readable medium for wireless communication is described. The non-transitory computer-readable medium may include instructions operable to cause a processor to: the method generally includes identifying a characteristic of a correspondence between one or more receive beams at the UE and one or more transmit beams at the UE, and transmitting a Random Access Channel (RACH) message to a base station based at least in part on the characteristic of the correspondence.

In some examples of the methods, apparatus, and non-transitory computer-readable media described above, the RACH message comprises RACH message 1(msg1) or RACH message 3(msg3) of a RACH procedure.

In some examples of the methods, apparatuses, and non-transitory computer-readable media described above, the RACH message conveys a characteristic of the correspondence. In some examples of the methods, apparatuses, and non-transitory computer-readable media described above, the characteristic of the correspondence includes at least one of a full correspondence, a partial correspondence, or a possible lack of correspondence.

In some examples of the methods, apparatus (devices), and non-transitory computer-readable media described above, transmitting the RACH message comprises: the RACH message is transmitted during the entire duration of the corresponding random access subframe.

A method of wireless communication is described. The method can comprise the following steps: the method generally includes transmitting a Downlink (DL) signal on one or more DL beams, receiving a Random Access Channel (RACH) message from a User Equipment (UE) on a plurality of Uplink (UL) beams on at least one of a resource or a RACH waveform, identifying a selected DL beam of the one or more DL beams for communication from a base station to the UE based at least in part on the resource or RACH waveform, and transmitting one or more subsequent messages to the UE using the selected DL beam.

An apparatus for wireless communication is described. The apparatus may include: the apparatus generally includes means for transmitting a Downlink (DL) signal on one or more DL beams, means for receiving a Random Access Channel (RACH) message from a User Equipment (UE) on a plurality of Uplink (UL) beams on at least one of a resource or a RACH waveform, means for identifying a selected DL beam of the one or more DL beams for communication from a base station to the UE based at least in part on the resource or RACH waveform, and means for transmitting one or more subsequent messages to the UE using the selected DL beam.

Another apparatus for wireless communication is described. The apparatus may include a processor, a memory in electronic communication with the processor, and instructions stored in the memory. The instructions are operable to cause the processor to: the method generally includes transmitting a Downlink (DL) signal on one or more DL beams, receiving a Random Access Channel (RACH) message from a User Equipment (UE) on a plurality of Uplink (UL) beams on at least one of a resource or a RACH waveform, identifying a selected DL beam of the one or more DL beams for communication from a base station to the UE based at least in part on the resource or RACH waveform, and transmitting one or more subsequent messages to the UE using the selected DL beam.

A non-transitory computer-readable medium for wireless communication is described. The non-transitory computer-readable medium may include instructions operable to cause a processor to: the method generally includes transmitting a Downlink (DL) signal on one or more DL beams, receiving a Random Access Channel (RACH) message from a User Equipment (UE) on a plurality of Uplink (UL) beams on at least one of a resource or a RACH waveform, identifying a selected DL beam of the one or more DL beams for communication from a base station to the UE based at least in part on the resource or RACH waveform, and transmitting one or more subsequent messages to the UE using the selected DL beam.

In some examples of the above methods, apparatus (devices), and non-transitory computer-readable media, the RACH message comprises RACH message 1(msg 1).

In some examples of the above-described methods, apparatuses (devices) and non-transitory computer-readable media, receiving the RACH message comprises: the RACH message is received during the entire duration of the corresponding random access subframe.

Some examples of the above-described methods, apparatus (devices), or non-transitory computer-readable media may further include processes, features, devices, or instructions for measuring the quality of a RACH message received on the plurality of UL beams. Some examples of the methods, apparatuses, and non-transitory computer-readable media described above may further include processes, features, means, or instructions for determining the selected UL beam for communication from the UE to the base station based at least in part on the quality.

A method of wireless communication is described. The method can comprise the following steps: the method generally includes receiving a RACH message from a User Equipment (UE) on a plurality of Uplink (UL) beams, measuring a quality of the RACH message received on the plurality of UL beams, identifying a preferred UL beam of the plurality of UL beams for communication from the UE to the base station based at least in part on the quality of the RACH message received on the plurality of UL beams, and transmitting one or more subsequent messages to the UE, the one or more subsequent messages conveying an indication of the preferred UL beam.

An apparatus for wireless communication is described. The apparatus may include: the apparatus generally includes means for receiving a RACH message from a User Equipment (UE) on a plurality of Uplink (UL) beams, means for measuring a quality of the RACH message received on the plurality of UL beams, means for identifying a preferred UL beam of the plurality of UL beams for communication from the UE to a base station based at least in part on the quality of the RACH message received on the plurality of UL beams, and means for transmitting one or more subsequent messages to the UE, the one or more subsequent messages conveying an indication of the preferred UL beam.

Another apparatus for wireless communication is described. The apparatus may include a processor, a memory in electronic communication with the processor, and instructions stored in the memory. The instructions are operable to cause the processor to: the method generally includes receiving a RACH message from a User Equipment (UE) on a plurality of Uplink (UL) beams, measuring a quality of the RACH message received on the plurality of UL beams, identifying a preferred UL beam of the plurality of UL beams for communication from the UE to the base station based at least in part on the quality of the RACH message received on the plurality of UL beams, and transmitting one or more subsequent messages to the UE, the one or more subsequent messages conveying an indication of the preferred UL beam.

A non-transitory computer-readable medium for wireless communication is described. The non-transitory computer-readable medium may include instructions operable to cause a processor to: the method generally includes receiving a RACH message from a User Equipment (UE) on a plurality of Uplink (UL) beams, measuring a quality of the RACH message received on the plurality of UL beams, identifying a preferred UL beam of the plurality of UL beams for communication from the UE to the base station based at least in part on the quality of the RACH message received on the plurality of UL beams, and transmitting one or more subsequent messages to the UE, the one or more subsequent messages conveying an indication of the preferred UL beam.

Some examples of the above-described methods, apparatus (devices), and non-transitory computer-readable media may further include processes, features, devices, or instructions for: transmitting one or more subsequent messages to the UE includes a RACH message 2(msg2) transmission.

In some examples of the methods, apparatus (devices), and non-transitory computer-readable media described above, receiving the RACH message from the UE comprises: the RACH message is received during a plurality of symbols on the plurality of UL beams.

In some examples of the methods, apparatuses, and non-transitory computer-readable media described above, one or more subsequent messages to the UE include an identification or index of the preferred UL beam.

In some examples of the methods, apparatus, and non-transitory computer-readable media described above, identifying the preferred UL beam includes: associating the resource or the RACH waveform with an index of the preferred UL beam.

In some examples of the methods, apparatus, and non-transitory computer-readable media described above, the index of the preferred UL beam comprises an Orthogonal Cover Code (OCC) index.

Some examples of the above-described methods, apparatus (devices), and non-transitory computer-readable media may further include processes, features, devices, or instructions for identifying the preferred UL beam based at least in part on a signal strength of the UL signal on the one or more UL beams, a signal quality of the UL signal on the one or more UL beams, or a combination thereof.

Drawings

Fig. 1 illustrates an example of a system of wireless communications supporting RACH communication of DL synchronization beam information for various DL-UL reciprocity states, in accordance with aspects of the present disclosure;

fig. 2 illustrates an example of a process flow of RACH communication supporting DL synchronization beam information for various DL-UL reciprocity states, in accordance with aspects of the present disclosure;

fig. 3 illustrates an example of a system of wireless communication supporting RACH communication of DL synchronization beam information for various DL-UL reciprocity states, in accordance with aspects of the present disclosure;

fig. 4A and 4B illustrate examples of aspects of beam subframe mapping configurations supporting RACH conveyance of DL synchronization beam information for various DL-UL reciprocity states, in accordance with aspects of the present disclosure;

fig. 5A and 5B illustrate examples of beam subframe mapping configurations supporting RACH conveyance of DL synchronization beam information for various DL-UL reciprocity states, in accordance with aspects of the present disclosure;

fig. 6A and 6B illustrate examples of beam subframe mapping configurations supporting RACH conveyance of DL synchronization beam information for various DL-UL reciprocity states, in accordance with aspects of the present disclosure;

fig. 7A and 7B illustrate examples of beam subframe mapping configurations supporting RACH conveyance of DL synchronization beam information for various DL-UL reciprocity states, in accordance with aspects of the present disclosure;

fig. 8 to 10 show block diagrams of devices supporting RACH communication of DL synchronization beam information for various DL-UL reciprocity states, in accordance with aspects of the present disclosure;

fig. 11 illustrates a block diagram of a system including a UE supporting RACH communication of DL synchronization beam information for various DL-UL reciprocity states, in accordance with aspects of the present disclosure;

fig. 12 to 14 show block diagrams of devices supporting RACH communication of DL synchronization beam information for various DL-UL reciprocity states, in accordance with aspects of the present disclosure;

fig. 15 illustrates a block diagram of a system including a base station supporting RACH communication of DL synchronization beam information for various DL-UL reciprocity states, in accordance with aspects of the present disclosure; and

fig. 16-19 illustrate methods of RACH communication of DL synchronization beam information for various DL-UL reciprocity states, in accordance with aspects of the present disclosure.

Detailed Description

The free space path loss may increase with carrier frequency. Transmission in millimeter wave (mmW) systems may also be affected by additional non-line-of-sight losses (e.g., diffraction losses, penetration losses, oxygen absorption losses, plant losses, etc.). During initial access, the base station and User Equipment (UE) may attempt to overcome these high path losses to discover or detect each other. Aspects of the present disclosure provide improved initial access in mmW systems.

Aspects of the present disclosure are initially described in the context of a wireless communication system. In general, the described techniques cause a UE to communicate an indication of a selected Downlink (DL) beam to a base station by selecting a corresponding resource and/or Random Access Channel (RACH) waveform for transmission of a RACH message/scheduling request message/beam recovery or beam tracking message. For example, the base station may transmit DL signal(s) on the DL beam(s). The UE may select a DL beam from DL signal(s) that may be used for DL communication (e.g., from a base station to the UE). The UE may select a resource and/or waveform (e.g., a RACH waveform or a scheduling request waveform) for transmitting a RACH message/scheduling request message/beam recovery or beam tracking message to the base station, where the selection is based on the selected DL beam. The UE may then transmit a RACH message/scheduling request message/beam recovery or beam tracking message to the base station using the selected resource and/or RACH waveform. The base station receives a RACH message/scheduling request message/beam recovery or beam tracking message on a selected resource and/or RACH waveform and uses the resource and/or RACH waveform to identify a selected DL beam. In one non-limiting example, the UE may select resources (e.g., channels) corresponding to timing characteristics (e.g., symbols) of the DL signal(s). The base station may then use the selected DL beam for communication from the base station to the UE (e.g., for subsequent DL communication). In some aspects, resources may refer to time resources, frequency resources, time-frequency resources, and the like.

Aspects of the present disclosure are further illustrated by and described with reference to apparatus, system, and flow diagrams related to RACH communication of DL synchronization beam information for various DL-UL correspondence states. In some aspects, the term "correspondence" may refer to reciprocity.

Fig. 1 illustrates an example of a wireless communication system 100 in accordance with various aspects of the present disclosure. The wireless communication system 100 includes base stations 105, UEs 115, and a core network 130. In some examples, the wireless communication system 100 may be an LTE (or LTE-advanced) network.

The base station 105 may communicate wirelessly with the UE 115 via one or more base station antennas. Each base station 105 may provide communication coverage for a respective geographic coverage area 110. The communication link 125 shown in the wireless communication system 100 may include UL transmissions from the UE 115 to the base station 105, or DL transmissions from the base station 105 to the UE 115. UEs 115 may be dispersed throughout the wireless communication system 100, and each UE 115 may be stationary or mobile. UE 115 may also be referred to as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless communication device, a remote device, a mobile subscriber station, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, a user agent, a mobile client, a client, or some other suitable terminology. The UE 115 may also be a cellular phone, a Personal Digital Assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a tablet computer, a laptop computer, a cordless phone, a personal electronic device, a handheld device, a personal computer, a Wireless Local Loop (WLL) station, an internet of things (IoT) device, an internet of everything (IoE) device, a Machine Type Communication (MTC) device, an appliance, an automobile, and so forth.

The base stations 105 may communicate with the core network 130 and with each other. For example, the base station 105 may interface with the core network 130 over a backhaul link 132 (e.g., S1, etc.). The base stations 105 may communicate with each other over a backhaul link 134 (e.g., X2, etc.) either directly or indirectly (e.g., through the core network 130). The base station 105 may perform radio configuration and scheduling for communication with the UE 115, or may operate under the control of a base station controller (not shown). In some examples, the base station 105 may be a macro cell, a small cell, a hot spot, and/or the like. The base station 105 may also be referred to as an evolved node B (eNB) 105.

During an initial access procedure (also referred to as a RACH procedure), the UE 115 may transmit a RACH preamble to the base station 105. This may be referred to as RACH message 1. For example, the RACH preamble may be randomly selected from a set comprising 64 predetermined sequences. This may enable the base station 105 to distinguish between multiple UEs 115 attempting to access the system at the same time. The base station 105 may respond with a Random Access Response (RAR) or RACH message 2 that provides UL resource grants, timing advance, and a temporary cell radio network temporary identity (C-RNTI). The UE 115 may then transmit a Radio Resource Control (RRC) connection request or RACH message 3, as well as a Temporary Mobile Subscriber Identity (TMSI) (in the case where the UE 115 has previously connected to the same wireless network) or a random identifier. The Radio Resource Control (RRC) connection request may also indicate the reason the UE 115 is connecting to the network (e.g., emergency, signaling, data exchange, etc.). The base station 105 may respond to the connection request with a contention resolution message or RACH message 4 addressed to the UE 115, which contention resolution message or RACH message 4 may provide a new C-RNTI. If the UE 115 receives the contention resolution message with the correct identification, the UE 115 may continue with the RRC setup. If the UE 115 does not receive the contention resolution message (e.g., if there is a collision with another UE 115), the UE 115 may repeat the RACH procedure by transmitting a new RACH preamble.

The wireless communication system 100 may operate using a frequency band from 700MHz to 2600MHz (2.6GHz) in the Ultra High Frequency (UHF) frequency region, but the WLAN network may use frequencies up to 4GHz in some cases. Since the wavelengths range from about 1 to 1 centimeter long, this region may also be referred to as the decimeter band. UHF waves may propagate primarily through the line of sight and may be blocked by building and environmental features. However, these waves may penetrate walls sufficiently to provide service to UEs 115 located indoors. UHF-wave transmission is characterized by a smaller antenna and shorter range (e.g., less than 100km) than transmission of smaller frequencies (and longer waves) using the High Frequency (HF) or Very High Frequency (VHF) portion of the spectrum. In some cases, wireless communication system 100 may also utilize the Extremely High Frequency (EHF) portion of the spectrum (e.g., from 30GHz to 300 GHz). Since the wavelength ranges from about 1 millimeter to 1 centimeter long, this region may also be referred to as the millimeter band. Accordingly, the EHF antenna may be even smaller and more closely spaced than the UHF antenna. In some cases, this may facilitate the use of antenna arrays (e.g., for directional beamforming) within the UE 115. However, EHF transmissions may experience even greater atmospheric attenuation and shorter ranges than UHF transmissions.

Specifically, the wireless communication system 100 may operate in a mmW frequency range (e.g., 28GHz, 40GHz, 60GHz, etc.). Wireless communication at these frequencies may be associated with increased signal attenuation (e.g., path loss), which may be affected by various factors, such as temperature, barometric pressure, diffraction, and the like. As a result, signal processing techniques such as beamforming (i.e., directional transmission) can be used to coherently combine the signal energy and overcome the path loss in a particular beam direction. In some cases, a device (such as UE 115) may select a beam direction for communicating with the network by selecting the strongest beam from among several signals transmitted by the base station. In one example, the signal may be a DL synchronization signal (e.g., a primary or secondary synchronization signal) or a DL reference signal (e.g., a channel state information reference signal (CSI-RS)) transmitted from the base station 105 during discovery. The discovery procedure may be cell-specific, e.g., may be directed in incremental directions around the coverage area 110 of the base station 105. In at least certain aspects, a discovery procedure may be used to identify and select beam(s) to be used for beamformed transmissions between the base station 105 and the UE 115.

In some cases, the base station antennas may be located within one or more antenna arrays. One or more base station antennas or antenna arrays may be co-located at an antenna assembly, such as an antenna tower. In some cases, the antennas or antenna arrays associated with the base station 105 may be located at different geographic locations. The base station 105 may use multiple antennas or antenna arrays for beamforming operations for directional communication with the UEs 115.

The wireless communication system 100 may be or may include a multi-carrier mmW wireless communication system. Broadly, aspects of the wireless communication system 100 may include UEs 115 and base stations 105 configured to support RACH communication of DL synchronization beam information for various DL-UL correspondence states. For example, the base station 105 may transmit DL signal(s) on the DL beam(s). The UE 115 may select a DL beam from DL signal(s) that may be used for DL communication (e.g., from the base station 105 to the UE 115). The UE 115 may select a resource and/or RACH waveform for transmitting a RACH message to the base station 105, where the selection is based on the selected DL beam. The UE 115 may then transmit a RACH message to the base station 105 using the selected resources and/or RACH waveform. The base station 105 receives the RACH message on the selected resource and/or RACH waveform and uses these resources and/or RACH waveforms to identify the selected DL beam. In one non-limiting example, the UE 115 can select resources (e.g., channels) corresponding to timing characteristics (e.g., symbols) of the DL synchronization signal(s). The base station 105 may then use the selected DL beam for communication from the base station 105 to the UE 115 (e.g., for subsequent DL communication).

Fig. 2 illustrates an example of a process flow 200 for RACH communication of DL synchronization beam information for various DL-UL correspondence states. Process flow 200 may implement aspects of wireless communication system 100 of fig. 1. Process flow 200 may include UE 115-a and base station 105-a, which may be examples of corresponding devices of fig. 1. The base station 105-a may be a mmW base station and a serving base station for the UE 115-a.

At 205, the base station 105-a may transmit an indication of a correspondence associated with the DL beam at the base station side. In some aspects, the base station 105-a may explicitly indicate the correspondence to the UE 115-a. For example, one bit may be dedicated to conveying a correspondence indication. In other aspects, the base station 105-a may implicitly indicate the correspondence. For example, the UE 115-a may infer from the mapping of DL beams to RACH resources or waveforms whether a correspondence exists or is missing at the base station 105-a. In one example, if Time Division Duplexing (TDD) is used to configure the DL beam and RACH resources, this may indicate that base station 105-a may have a correspondence.

In some cases, base station 105-a may include an indication of the correspondence in a Master Information Block (MIB) (e.g., bits reserved to indicate the correspondence) or a System Information Block (SIB) (e.g., bits reserved to indicate the correspondence) transmitted to UE 115-a. In some examples, the base station may transmit the MIB on a Physical Broadcast Channel (PBCH), and the base station may transmit the SIB on an extended PBCH. In some examples, the indication may be based on preamble formats, where one preamble format may convey an indication of no correspondence, a second preamble format may convey an indication of partial correspondence, and a third preamble format may convey an indication of full correspondence. Based on the indication of correspondence, the UE 115-a may determine whether there is full correspondence, no correspondence, or partial correspondence (e.g., with an uncertainty region of 2 × N +1, where N represents the number of subarrays at the UE 115-a or with an uncertainty of 2 × M +1, where M represents the number of beams transmitted by the base station 105-a). If the UE 115-a determines that the correspondence is missing, the UE 115-a may select a different UL beam than the DL beam used by the base station 105-a (e.g., for communication with the base station 105-a).

Additionally or alternatively, at 205, the UE 115-a may transmit an indication of a correspondence associated with the UL beam at the UE side. For example, the UE 115-a may communicate characteristics of a correspondence between one or more receive DL synchronization beams at the UE and one or more transmit Uplink (UL) beams at the UE, an indication of the correspondence in a RACH message (e.g., RACH message 1(msg1) or RACH message 3(msg3)) or on a Physical Uplink Control Channel (PUCCH) or a Physical Uplink Shared Channel (PUSCH). The base station 105-a may receive an indication of a correspondence at the UE side, and based on the indication, the base station 105-a may determine to map a beam for transmitting a channel state information reference signal (CSI-RS) to a beam for transmitting a Sounding Reference Signal (SRS), and vice versa. Additionally, the base station 105-a may determine to map the beam used in the DL beam training to the beam used in the UL beam training based on the indication, and vice versa.

At 210, the base station 105-a may transmit (and the UE 115-a may receive) a DL synchronization signal to the UE 115-a. The DL synchronization signal may be a beamformed signal transmitted from the base station 105-a on the DL synchronization beam(s). The DL synchronization signal may be associated with an index and/or symbol of a subframe. The DL synchronization signal may be associated with a transmit power condition.

In some aspects, the base station 105-a transmits multiple DL synchronization signals during the synchronization subframe. Each DL synchronization signal may be transmitted in a symbol of the synchronization subframe (e.g., DL synchronization signal 1 may be transmitted during symbol 1, DL synchronization signal 2 may be transmitted during symbol 2, etc.).

At 215, the UE 115-a may identify a selected one of the DL synchronization beams for communication from the base station 105-a to the UE 115-a. The UE 115-a may identify the selected DL beam by identifying a preferred DL beam based on the signal strength and/or signal quality (e.g., high received signal strength and/or low interference level) of the DL synchronization signal. In some aspects, the UE 115-a may identify the selected DL beam by identifying a transmit power condition (e.g., a transmit power above a threshold level) of a DL synchronization signal on the DL synchronization beam.

At 220, UE 115-a may select a resource and/or RACH waveform for transmitting a RACH message to base station 105-a. In at least certain aspects, resources and/or RACH waveforms may be selected based on the selected DL beam (e.g., based on an index of the selected DL beam, based on symbols of a subframe of a DL synchronization signal of the selected DL beam, etc.). The resource and/or RACH waveform may be associated with tone(s) in the component carrier and/or with the component carrier.

At 225, the UE 115-a may transmit a RACH message to the base station 105-a. The RACH message may be transmitted on the selected RACH resource and/or RACH waveform. The RACH message may be transmitted during the entire duration of the corresponding random access subframe (e.g., during each symbol of the random access subframe). In some aspects, a RACH message may be transmitted during the entire duration of a corresponding random access slot, subframe, opportunity, burst, set of bursts, and so forth. In general, these terms may refer to time durations where the gNB sweeps some or all of its receive beams to receive RACH message(s). In some aspects, the UE 115-a may select a RACH waveform for transmitting the RACH message. The RACH waveform may be selected based on the selected DL beam and may include a RACH preamble, cyclic shift, and the like. In some aspects, UE 115-a may transmit RACH messages on multiple UL beams.

At 230, the base station 105-a may identify the selected DL beam. The base station 105-a may identify the selected DL beam based on the resources and/or RACH waveform used for RACH message transmission. In some aspects, the base station 105-a may identify the selected DL beam by associating resources and/or RACH waveforms with an index of the selected DL beam. In some aspects, the base station 105-a may identify the selected DL beam by associating resources and/or RACH waveforms with symbols of a subframe of a DL synchronization signal of the selected DL beam.

In some aspects, the base station 105-a may identify the selected DL beam based on a RACH waveform of a RACH message. For example, the base station 105-a may identify the selected DL beam based on a RACH preamble of a RACH message, a cyclic shift of a RACH message, and so on.

At 235, the base station 105-a may transmit a subsequent message to the UE 115-a using the selected DL beam. In some cases, the selected DL beam is the preferred DL beam. Further, in some aspects, the base station 105-a may determine the selected UL beam for communication from the UE 115-a to the base station 105-a using a RACH message received from the UE 115-a. For example, base station 105-a may measure the quality of RACH messages received on multiple UL beams and determine the selected UL beam based on the measured quality. Measuring the quality of the RACH message may include measuring Reference Signal Received Power (RSRP), Received Signal Strength Indicator (RSSI), Reference Signal Received Quality (RSRQ), signal-to-noise ratio (SNR), signal-to-interference-and-noise ratio (SINR), and the like.

In some cases, UE 115-a may measure RSRP of received signals transmitted over a synchronization signal block (e.g., where a combination of one or more synchronization signals are transmitted together in a certain direction) to identify the best signal. In the case where UE 115-a is unable to determine the strongest port associated with a particular symbol, UE 115-a may use a different spreading code (e.g., Orthogonal Cover Code (OCC)) to indicate or communicate the best SS block index or preferred DL beam to base station 105-a. In some examples, the base station 105-a may transmit one or more additional reference signals (e.g., Beam Reference Signals (BRSs), Mobility Reference Signals (MRSs), etc.) within the symbols used for the synchronization signals 205, and the UE 115-a may identify the best transmission port (e.g., the best downlink transmission beam ID). As a result, the UE 115-a may feed back the optimal downlink transmission beam ID by using a different spreading code.

If the base station 105-a does not have a beam correspondence, the base station 105-a may request the UE 115-a to transmit the RACH in all symbols of the RACH slot. The base station 105-a may then find the best uplink receive beam based on the quality of the received RACH signal. In some examples, when the base station 105-a does not have a transmit/receive beam correspondence, the base station 105-a may configure an association between a downlink signal or downlink channel and a subset of RACH resources and/or a subset of preamble indices (e.g., RACH preamble indices) that may be used to determine a downlink transmission beam (e.g., for sending message 2(Msg 2)). Based on the downlink measurements and corresponding associations of the received signals, UE 115-a may select a subset of RACH resources and/or a subset of RACH preamble indices. In such cases, the preamble index may include a preamble sequence index and an OCC index, such as in the case when OCC is supported. In some examples, the subset of preambles may be indicated by an OCC index.

In some aspects, there may be a lack of correspondence between the DL synchronization beam from the base station 105-a and the UL beam from the UE 115-a. Thus, in some examples, the selected DL beam may be different from the selected UL beam. Aspects of the present disclosure may support partial beam correspondence or no beam correspondence between DL transmission beams and UL reception beams. In the case of partial correspondence, the RACH message transmitted at 225 may be transmitted at the transmission time with the center symbol corresponding to the best (e.g., strongest received signal strength) DL synchronization beam or with the center symbol corresponding to the symbol associated with the best DL synchronization beam. Similarly, UE 115-a may determine the RACH preamble of the RACH message at 225 based on the best DL synchronization beam, and UE 115-a may determine the subcarrier region for RACH message transmission at 225 based on the best DL synchronization beam. This may be applicable to Frequency Division Duplex (FDD) systems where there may not be a full beam correspondence between DL and UL. The amount of partial beam correspondence may vary from scene to scene. In some examples, the missing correspondences may be associated with different channel propagation characteristics (e.g., different transmit power levels, different angles of departure and/or arrival, etc.) for the DL and UL beams.

In some cases, the correspondence may exist at the base station 105-a. In this case, the base station 105-a may transmit different DL synchronization signals at different times, and the base station 105-a may simultaneously receive corresponding RACH resources from the UE 115-a through the digital receiver subsystem, which may not be affected by analog beam constraints. In this case, the base station 105-a may request the UE 115-a to map the DL synchronization signal to a RACH resource or waveform. The base station 105-a may then analyze each receive beam path with a RACH detector.

Aspects of the present disclosure may also support a beam correspondence between DL transmission beams and UL reception beams. In the case where there is a correspondence, the RACH message transmitted at 225 may be transmitted at a transmission time corresponding to the best DL synchronization beam or a symbol corresponding to the best DL synchronization beam.

Fig. 3 illustrates an example of a system 300 for wireless communication supporting RACH communication of DL synchronization beam information for various DL-UL correspondence states. System 300 may be an example of aspects of wireless communication system 100 of fig. 1. System 300 may be a mmW wireless communication system. System 300 may include a UE 115-b and a base station 105-b, which may be examples of corresponding devices of FIGS. 1 and 2. Broadly, the system 300 illustrates aspects of a discovery procedure in which a UE 115-b discovers a base station 105-b based on DL synchronization signals transmitted on DL synchronization beams.

In some examples, the base station 105-b may be a mmW base station that transmits beamformed transmissions to the UE 115-b on an active beam. The transmission from the base station 105-b may be a beamformed transmission or a directional transmission directed toward the UE 115-a.

For example, the base station 105-b may transmit a DL synchronization signal on the DL synchronization beam 305. The base station 105-b may transmit DL synchronization signals in a beamformed manner (e.g., for random access) and sweep through an angular coverage area (e.g., in azimuth and/or elevation). Each DL synchronization beam 305 may be transmitted in a beam sweeping operation in a different direction in order to cover the coverage area of the base station 105-b. For example, the DL synchronization beam 305-a may be transmitted in a first direction, the DL synchronization beam 305-b may be transmitted in a second direction, the DL synchronization beam 305-c may be transmitted in a third direction, and the DL synchronization beam 305-d may be transmitted in a fourth direction. Although system 300 shows four DL synchronization beams 305, it is understood that fewer and/or more DL synchronization beams 305 may be transmitted. Further, the DL synchronization beams 305 may be transmitted at different beamwidths, at different elevation angles, and so on. In some aspects, the DL synchronization beam 305 may be associated with a beam index (e.g., an indicator identifying the beam).

In some aspects, the DL synchronization beam 305 may also be transmitted during different symbol periods of the synchronization subframe. For example, the DL synchronization beam 305-a may be transmitted during a first symbol period (e.g., symbol 0), the DL synchronization beam 305-b may be transmitted during a second symbol period (e.g., symbol 1), the DL synchronization beam 305-c may be transmitted during a third symbol period (e.g., symbol 2), and the DL synchronization beam 305-d may be transmitted during a fourth symbol period (e.g., symbol 3). Additional DL synchronization beams 305 may be transmitted during other symbol periods of the synchronization subframe.

In general, performing a beam sweep operation supports base station 105-b in determining which direction UE 115-b is located (e.g., after receiving a response message from UE 115-b). This supports the transmission of RACH message 2 from base station 105-b. Further, when no correspondence is maintained between DL and UL channels, the beam sweeping operation improves communication, and the UE 115-b may select a frequency region and/or waveform configuration (e.g., resource and/or RACH waveform) for transmitting a random access signal (e.g., RACH message 1, or RACH message 3) based on the index of the best or preferred DL synchronization signal on the DL synchronization beam 305. In some cases, UE 115-a may use an index or identification in RACH message 1 to communicate the best or preferred DL beam. During the random access period, the base station 105-a may find a suitable UL beam by receiving random access signals in a sweeping manner. The base station 105-b may identify the DL beam selected by the UE 115-a from the used resources and/or RACH waveform (e.g., used frequency region and/or waveform configuration) of the RACH message (e.g., RACH message 1 or RACH message 3) containing the random access signal.

Thus, each UE within the coverage area of base station 105-b may receive a DL synchronization signal on DL synchronization beam 305. The UE 115-b may identify which DL synchronization signal is the best (e.g., strongest received signal strength, best channel quality, etc.) and identify it as the selected DL beam. The UE 115-b may then select a resource and/or RACH waveform for transmitting a RACH message based on the selected DL beam (e.g., the preferred DL beam). In one example, the resources and/or RACH waveform used to transmit the RACH message may correspond to the symbols of the selected DL beam. In another example, the RACH message may include an identification or index of the preferred DL beam.

As one non-limiting example, there may be 16 different available DL beams. Thus, the UE 115-b may use 4 bits for communicating DL beam information to the base station 105-b. There may be 4 subcarrier regions (e.g., resources) and 4 different RACH waveforms available for use by the UE 115-b. Accordingly, UE 115-b may transmit these 4 bits by selecting one RACH waveform from among 4 different RACH waveforms and one subcarrier from among four subcarriers. Thus, the UE 115-b may select a combination of resources and RACH waveforms to transmit a RACH message to the base station 105-a.

Thus, in certain aspects, system 300 may support a UE 115-b to select a combination of RACH waveforms and/or resources for its RACH message transmission based on one or more combinations of indices of DL synchronization beams or indices of symbols of DL synchronization subframes. UE 115-b may transmit a random access signal (e.g., RACH message 1, or RACH message 3) during the entire duration of a random access subframe and/or during a portion of a random access subframe.

In some aspects, the base station 105-b may determine the selected DL beam for the UE 115-b from the used frequency region and/or RACH waveform of message 1 containing the random access signal. Base station 105-b may determine the best UL receive beam by measuring the quality of the received signal at the different uplink receiver beams. The signal quality may represent one or more combinations of RSRP, RSSI, RSRQ, SNR, SINR, etc.

In some aspects, the UE 115-b may select the best DL synchronization signal and the frequency region of the RACH and/or the RACH waveform based on the index of the best DL synchronization signal. The UE 115-b may select a DL synchronization beam 305 that satisfies the transmit power condition. The UE 115-b may select the RACH preamble and cyclic shift based in part on the index of the DL synchronization beam 305.

The absence of correspondence may indicate that the best DL beam is not the same as the best UL beam.

In some aspects, if the base station 105-b transmits multiple beams using multiple antenna ports in each symbol of the synchronization subframe, the UE 115-b may select a combination of RACH and resources for transmission of the RACH based on the symbols of the DL synchronization subframe. In some aspects, the resources may represent tones and/or component carriers of a component carrier.

Although the example described with reference to fig. 3 relates to transmitting a RACH message in a RACH subframe, the example is also applicable to transmitting a scheduling request message, a beam recovery message, or a beam tracking message in a RACH subframe. In some cases, the UE 115 may find that the best synchronization beam was transmitted during a particular symbol, and the UE 115 may transmit a scheduling request message, a beam recovery message, or a beam tracking message in a frequency region corresponding to the particular symbol. The frequency regions may be in different resources (or resource blocks) in the RACH subframe. That is, a first portion of resources in a RACH subframe may be allocated for RACH message transmission, a second portion of resources in a RACH subframe may be allocated for scheduling request message transmission, and a third portion of resources in a RACH subframe may be allocated for beam recovery or beam tracking message transmission.

The UE 115-b may receive an indication of a subcarrier region for scheduling request message transmission, or beam recovery or beam tracking message transmission through RRC signaling. In some cases, there may be eight (8) possible subcarrier regions. The UE 115-b may also receive a desired cyclic shift for scheduling request message transmission, or beam recovery or beam tracking message transmission through RRC signaling. In some examples, UE 115-b may use twelve (12) different cyclic shifts to generate a sequence for scheduling request message transmission, or beam recovery or beam tracking message transmission. The number of available cyclic shifts for scheduling request message transmission, or beam recovery or beam tracking message transmission may be greater than the number of available cyclic shifts for RACH message transmission because timing errors may be corrected before the UE 115-b transmits the scheduling request message transmission, or beam recovery or beam tracking message. Further, the transmission of the scheduling request message, or the transmission of the beam recovery or beam tracking message, may span two (2) symbols, which may provide an additional degree of freedom (e.g., 192 degrees of freedom in each symbol pair).

Fig. 4A and 4B illustrate an example of a beam subframe mapping configuration 400 for RACH communication of DL synchronization beam information for various DL-UL correspondence states. Configuration 400 may implement aspects of wireless communication system 100, process flow 200, and/or system 300 of fig. 1 through 3. In some aspects, aspects of the configuration 400 may be implemented by the base station 105 and/or the UE 115 as described with reference to fig. 1-3.

Referring to fig. 4A, the beam subframe mapping configuration 400 may include a plurality of DL synchronization signals transmitted on the DL synchronization beam 405. The base station 105 may transmit DL synchronization signals in a beamformed manner (e.g., for random access) and sweep through an angular coverage area (e.g., in azimuth and/or elevation). Each DL synchronization beam 405 may be transmitted in a beam sweeping operation in a different direction in order to cover the coverage area of the base station 105. For example, the DL synchronization beam 405-a may be transmitted in a first direction, the DL synchronization beam 405-b may be transmitted in a second direction, and so on. In some aspects, the DL synchronization beam 405 may be associated with a beam index (e.g., an indicator identifying the beam).

In some aspects, the DL synchronization beam 405 may also be transmitted during different symbol periods of the synchronization subframe 410. The synchronization subframe 410 may be associated with a time characteristic (e.g., symbol) along a horizontal axis and with a frequency characteristic (e.g., frequency or tone) along a vertical axis. For example, the DL synchronization beam 405-a may be transmitted during a first symbol period (e.g., symbol 0), the DL synchronization beam 405-b may be transmitted during a second symbol period (e.g., symbol 1), and so on until the DL synchronization beam 405-h is transmitted during an eighth symbol period (e.g., symbol 7).

In some aspects, each DL synchronization signal transmitted on the DL synchronization beam 405 may be transmitted on some or all frequencies during a symbol. For example, DL synchronization beam 405-a may be transmitted on frequency or tones 0-7 during symbol 0, DL synchronization beam 405-b may be transmitted on frequency or tones 0-7 during symbol 1, and so on.

Thus, the base station 105 may sweep the DL synchronization beam 405 in eight directions during the eight symbols of the synchronization subframe 410.

Referring to fig. 4B, each UE 115 within the coverage area of the base station 105 may receive a DL synchronization signal on a DL synchronization beam 405. The UE 115 may identify which DL synchronization signal is the best (e.g., strongest received signal strength, best channel quality, etc.) and identify it as the selected DL beam. In the example fig. 4B, the UE 115 has identified the DL synchronization signal transmitted on the DL synchronization beam 405-B as the selected DL beam. As indicated, the DL synchronization beam 405-b is transmitted during the second symbol.

In some aspects, the UE 115 may then select a resource for transmitting the RACH message based on the selected DL beam and during the RACH subframe 415. In one example, the resources used to transmit the RACH message may correspond to the symbols of the selected DL beam. Accordingly, UE 115 may select a second resource 420 (e.g., frequency or tone 1) as the resource for transmitting the RACH message. That is, the UE 115 may select the second resource 420 to convey an indication of a DL synchronization beam to be transmitted during the second symbol as the selected DL beam. As discussed above, the UE 115 may also select a RACH waveform to transmit a RACH message.

Thus, the UE 115 may find that the best synchronization beam was transmitted during the second symbol. The UE 115 may transmit the RACH message in the second frequency region in all time slots (e.g., during all symbols of the RACH subframe 415). The base station 105 may find the best DL transmit beam from the used frequency region (e.g., the second resource 420) of the random access signal (e.g., RACH message). In some examples, the RACH message transmission time unit may be larger than the synchronization subframe time unit, e.g., due to DL-UL power differences.

In some aspects, the base station 105 may sweep the same eight directions during the same eight symbols during the RACH subframe 415. For example, the base station 105 may configure one or more antenna arrays to receive RACH messages according to the same sweep pattern used to transmit DL synchronization signals on the DL synchronization beam 405 during the RACH subframe 415.

The example described above with reference to fig. 4 may be applicable to a situation where there is no correspondence for the selected DL beam at the base station 105. Additionally, this example may apply to situations where there is no correspondence at both the base station 105 and the UE 115. In such cases, the UE 115 may identify a method of transmitting using the selected DL beam based on a link gain associated with the transmission from the UE 115. In some cases, the UE 115 may determine its link gain based on a synchronization signal received from the base station 105. UE 115 may transmit a RACH message in a single RACH subframe if UE 115 has sufficient link gain to meet the link budget. However, if the UE 115 does not have sufficient link gain to meet the link budget, the UE 115 may transmit RACH messages in multiple RACH subframes.

Although the example described with reference to fig. 4A and 4B involves transmitting a RACH message in RACH subframe 415, the example is also applicable to transmitting a scheduling request message, a beam recovery message, or a beam tracking message in RACH subframe 415. In some cases, the UE 115 may find that the best synchronization beam is transmitted during the second symbol, and the UE 115 may transmit a scheduling request message, a beam recovery message, or a beam tracking message in the second frequency region in all time slots. The second frequency region may be in a different resource (or resource block) in the RACH subframe 415. That is, a first portion of the resources in the RACH subframe 415 may be allocated for RACH message transmission, a second portion of the resources in the RACH subframe 415 may be allocated for scheduling request message transmission, and a third portion of the resources in the RACH subframe 415 may be allocated for beam recovery or beam tracking message transmission.

Fig. 5A and 5B illustrate examples of beam subframe mapping configurations 500 for RACH communication of DL synchronization beam information for various DL-UL correspondence states. Configuration 500 may implement aspects of wireless communication system 100, process flow 200, and/or system 300 of fig. 1-3. In some aspects, aspects of the configuration 500 may be implemented by the base station 105 and/or the UE 115 as described with reference to fig. 1-3.

Referring to fig. 5A, a beam subframe mapping configuration 500 may include a plurality of DL synchronization signals transmitted on a DL synchronization beam 505. The base station 105 may transmit DL synchronization signals in a beamformed manner (e.g., for random access) and sweep through an angular coverage area (e.g., in azimuth and/or elevation). Each DL synchronization beam 505 may be transmitted in beam sweeping operations in different directions in order to cover the coverage area of the base station 105. For example, DL synchronization beam 505-a may be transmitted in a first direction, DL synchronization beam 505-b may be transmitted in a second direction, and so on. In some aspects, the DL synchronization beam 505 may be associated with a beam index (e.g., an indicator identifying the beam).

In some aspects, the DL synchronization beam 505 may also be transmitted during different symbol periods of the synchronization subframe 510. The synchronization subframe 510 may be associated with a time characteristic (e.g., symbol) along a horizontal axis and with a frequency characteristic (e.g., frequency or tone) along a vertical axis. In the example fig. 5A, the base station 105 may be configured with four antenna arrays, where the base station 105 sweeps four directions in each symbol. For example, antenna ports 0-3 may be grouped into subgroups 510 and used to transmit DL synchronization beams 505-a through 505-d during the first symbol (e.g., symbol 0) of synchronization subframe 510. Also, antenna ports 0-3 may be grouped into subgroups 515 and used to transmit DL synchronization beams 505-e through 505-h during a second symbol (e.g., symbol 1) of synchronization subframe 510. Thus, the base station 105 may sweep eight directions during two symbols of the synchronization subframe 510.

In some aspects, each DL synchronization signal transmitted on the DL synchronization beam 505 may be transmitted on some or all frequencies during a symbol. For example, DL synchronization beam 505-a may be transmitted on any of frequencies or tones 0-7 during symbol 0, DL synchronization beam 505-b may be transmitted on any of frequencies or tones 0-7 during symbol 1, and so on. In some aspects, the DL synchronization beams 505 transmitted during a symbol may not be transmitted on overlapping frequencies.

Thus, the base station 105 may sweep the DL synchronization beam 505 in eight directions during the eight symbols of the synchronization subframe 510.

Referring to fig. 5B, each UE 115 within the coverage area of the base station 105 may receive a DL synchronization signal on a DL synchronization beam 505. The UE 115 may identify which DL synchronization signal is the best (e.g., strongest received signal strength, best channel quality, etc.) and identify it as the selected DL beam. In the example fig. 5B, the UE 115 has identified the DL synchronization signal transmitted on the DL synchronization beam 505-a as the selected DL beam. As indicated, the DL synchronization beam 505-a is transmitted during the first symbol (e.g., during symbol 0).

In some aspects, UE 115 may then select a resource for transmitting a RACH message based on the selected DL beam and during RACH subframe 515. In one example, the resources used to transmit the RACH message may correspond to the symbols of the selected DL beam. Accordingly, UE 115 may select a first resource 520 (e.g., frequency or tone 0) as the resource for transmitting the RACH message. That is, the UE 115 may select the first resource 520 to convey an indication of a DL synchronization beam to be transmitted during the first symbol as the selected DL beam.

Thus, the UE 115 may find that the best synchronization beam was transmitted during the first symbol. UE 115 may transmit a RACH message in a first frequency region in all time slots (e.g., during all symbols of RACH subframe 515). The base station 105 may find the best UL received beam by measuring the quality of the received signal during different time slots (e.g., during different symbols). In some aspects, the base station 105 may find the best route DL beam from the used frequency region (e.g., the first resource 520) of the random access signal (e.g., RACH message).

In some aspects, the base station 105 may sweep the same eight directions during the same eight symbols during RACH subframe 515. For example, the base station 105 may configure one or more antenna arrays to receive RACH messages according to the same sweep pattern used to transmit DL synchronization signals on the DL synchronization beam 505 during the synchronization subframe 510.

Fig. 6A and 6B illustrate examples of beam subframe mapping configurations 600 for RACH communication of DL synchronization beam information for various DL-UL correspondence states. Configuration 600 may implement aspects of wireless communication system 100, process flow 200, and/or system 300 in fig. 1-3. In some aspects, aspects of the configuration 600 may be implemented by the base station 105 and/or the UE 115 as described with reference to fig. 1-3.

Referring to fig. 6A, a beam subframe mapping configuration 600 may include a plurality of DL synchronization signals transmitted on a DL synchronization beam 605. The base station 105 may transmit DL synchronization signals in a beamformed manner (e.g., for random access) and sweep through an angular coverage area (e.g., in azimuth and/or elevation). Each DL synchronization beam 605 may be transmitted in beam sweeping operations in different directions in order to cover the coverage area of the base station 105. For example, DL synchronization beams 605-a may be transmitted in a first direction, DL synchronization beams 605-b may be transmitted in a second direction, and so on. In some aspects, the DL synchronization beam 605 may be associated with a beam index (e.g., an indicator identifying the beam).

In some aspects, the DL synchronization beam 605 may also be transmitted during different symbol periods of the synchronization subframe 610. The synchronization subframe 610 may be associated with a time characteristic (e.g., symbol) along a horizontal axis and with a frequency characteristic (e.g., frequency or tone) along a vertical axis. For example, the DL synchronization beam 605-a may be transmitted during a first symbol period (e.g., symbol 0), the DL synchronization beam 605-b may be transmitted during a second symbol period (e.g., symbol 1), and so on until the DL synchronization beam 605-h is transmitted during an eighth symbol period (e.g., symbol 7).

In some aspects, each DL synchronization signal transmitted on the DL synchronization beam 605 may be transmitted on some or all frequencies during a symbol. For example, DL synchronization beam 605-a may be transmitted on frequency or tones 0-7 during symbol 0, DL synchronization beam 605-b may be transmitted on frequency or tones 0-7 during symbol 1, and so on.

Thus, the base station 105 may sweep the DL synchronization beam 605 in eight directions during the eight symbols of the synchronization subframe 610.

Referring to fig. 6B, each UE 115 within the coverage area of the base station 105 may receive a DL synchronization signal on a DL synchronization beam 605. The UE 115 may identify which DL synchronization signal is the best (e.g., strongest received signal strength, best channel quality, etc.) and identify it as the selected DL beam. In the example fig. 6B, the UE 115 has identified the DL synchronization signal transmitted on the DL synchronization beam 605-B as the selected DL beam. As indicated, the DL synchronization beam 605-b is transmitted during the second symbol.

In some aspects, the DL synchronization beams 605-b may have full correspondence at the base station 105 and the UE 115. That is, the DL synchronization beams 605-b may be used for transmission and reception at both the base station 105 and the UE 115. Thus, the UE 115 may select the DL synchronization beam 605-b to transmit a RACH message to the base station 105. In some cases, UE 115 may randomly select a subcarrier region for transmitting RACH messages to provide diversity when multiple UEs are present. In the example fig. 6B, UE 115 has selected subcarrier 3 for transmitting the RACH message.

In other aspects, the DL synchronization beams 605-b may have full correspondence at the base station 105 and no correspondence at the UE 115. That is, the DL synchronization beam 605-b may be used for transmission and reception at the base station 105, but transmissions from the UE 115 on the DL synchronization beam 605-b may be noisy. In such cases, the UE 115 may identify a method of transmitting using the selected DL beam based on a link gain associated with the transmission from the UE 115. In some cases, the UE 115 may determine its link gain based on a synchronization signal received from the base station 105. UE 115 may transmit a RACH message in a single RACH subframe if UE 115 has sufficient link gain to meet the link budget. However, if the UE 115 does not have sufficient link gain to meet the link budget, the UE 115 may transmit RACH messages in multiple RACH subframes.

Although the example described with reference to fig. 6A and 6B involves transmitting a RACH message in RACH subframe 615, the example is also applicable to transmitting a scheduling request message, a beam recovery message, or a beam tracking message in RACH subframe 615. In some cases, the UE 115 may find that the best synchronization beam is transmitted during the second symbol, and the UE 115 may transmit a scheduling request message, a beam recovery message, or a beam tracking message in the second frequency region in all time slots. The second frequency region may be in a different resource (or resource block) in the second symbol. That is, a first portion of the resources in RACH subframe 615 may be allocated for RACH message transmission, a second portion of the resources in RACH subframe 615 may be allocated for scheduling request message transmission, and/or a third portion of the resources in RACH subframe 615 may be allocated for beam recovery or beam tracking message transmission.

Fig. 7A and 7B illustrate an example of a beam subframe mapping configuration 700 for RACH communication of DL synchronization beam information for various DL-UL correspondence states. Configuration 700 may implement aspects of wireless communication system 100, process flow 200, and/or system 300 in fig. 1-3. In some aspects, aspects of the configuration 700 may be implemented by the base station 105 and/or the UE 115 as described with reference to fig. 1-3.

Referring to fig. 7A, a beam subframe mapping configuration 700 may include a plurality of DL synchronization signals transmitted on a DL synchronization beam 705. The base station 105 may transmit DL synchronization signals in a beamformed manner (e.g., for random access) and sweep through an angular coverage area (e.g., in azimuth and/or elevation). Each DL synchronization beam 705 may be transmitted in a beam sweeping operation in different directions in order to cover the coverage area of the base station 105. For example, the DL synchronization beam 705-a may be transmitted in a first direction, the DL synchronization beam 705-b may be transmitted in a second direction, and so on. In some aspects, the DL synchronization beam 705 may be associated with a beam index (e.g., an indicator identifying the beam).

In some aspects, the DL synchronization beam 705 may also be transmitted during different symbol periods of the synchronization subframe 710. The synchronization subframe 710 may be associated with a time characteristic (e.g., symbol) along a horizontal axis and with a frequency characteristic (e.g., frequency or tone) along a vertical axis. For example, the DL synchronization beam 705-a may be transmitted during a first symbol period (e.g., symbol 0), the DL synchronization beam 705-b may be transmitted during a second symbol period (e.g., symbol 1), and so on until the DL synchronization beam 705-h is transmitted during an eighth symbol period (e.g., symbol 7).

In some aspects, each DL synchronization signal transmitted on the DL synchronization beam 705 may be transmitted on some or all frequencies during a symbol. For example, the DL synchronization beam 705-a may be transmitted on frequency or tones 0-7 during symbol 0, the DL synchronization beam 705-b may be transmitted on frequency or tones 0-7 during symbol 1, and so on.

Thus, the base station 105 may sweep the DL synchronization beam 705 in eight directions during the eight symbols of the synchronization subframe 710.

Referring to fig. 7B, each UE 115 within the coverage area of the base station 105 may receive a DL synchronization signal on a DL synchronization beam 705. The UE 115 may identify which DL synchronization signal is the best (e.g., strongest received signal strength, best channel quality, etc.) and identify it as the selected DL beam. In the example fig. 7B, the UE 115 has identified the DL synchronization signal transmitted on the DL synchronization beam 705-B as the selected DL beam. As indicated, the DL synchronization beam 705-b is transmitted during the second symbol.

In some aspects, the DL synchronization beam 705-b may have a partial correspondence at the base station 105 and the UE 115. That is, the DL synchronization beam 705-b may be used for transmission and reception with less noise at both the base station 105 and the UE 115. However, it may be desirable for the UE 115 to identify a better beam (e.g., stronger signal strength) for uplink transmission. Thus, the UE 115 may transmit RACH messages on symbols of the selected DL beam and symbols of each adjacent DL beam (e.g., DL synchronization beams 705-a and 705-c). To receive uplink transmissions, the base station 105 may sweep a portion of the eight directions during symbols 0, 1, and 2 in RACH subframe 715.

The UE 115 may then select resources for transmitting the RACH message based on the selected DL beam and during the RACH subframe 415. In one example, the resources used to transmit the RACH message may correspond to the symbols of the selected DL beam. Accordingly, UE 115 may select a second resource 720 (e.g., frequency or tone 1) as the resource for transmitting the RACH message. That is, the UE 115 may select the second resource 720 to convey an indication of a DL synchronization beam to be transmitted during the second symbol as the selected DL beam. As discussed above, the UE 115 may also select a RACH waveform to transmit a RACH message.

Thus, the UE 115 may find that the best synchronization beam is transmitted during the second symbol. The UE 115 may transmit the RACH message in the second frequency region during a portion of all time slots (e.g., during a portion of each symbol of the RACH subframe 715). The base station 105 may find the best DL transmit beam from the used frequency region (e.g., the second resource 720) of the random access signal (e.g., RACH message). In some examples, the RACH message transmission time unit may be larger than the synchronization subframe time unit, e.g., due to DL-UL power differences.

Although the example described with reference to fig. 7A and 7B involves transmitting a RACH message in RACH subframe 715, the example is also applicable to transmitting a scheduling request message, a beam recovery message, or a beam tracking message in RACH subframe 715. In some cases, the UE 115 may find that the best synchronization beam was transmitted during the second symbol, and the UE 115 may transmit a scheduling request message, a beam recovery message, or a beam tracking message in the second frequency region in a portion of each symbol. The second frequency region may be in a different resource (or resource block) in RACH subframe 715. That is, a first portion of the resources in the RACH subframe 715 may be allocated for RACH message transmission, a second portion of the resources in the RACH subframe 715 may be allocated for scheduling request message transmission, and/or a third portion of the resources in the RACH subframe 715 may be allocated for beam recovery or beam tracking message transmission.

Fig. 8 illustrates a block diagram 800 of a wireless device 805 that supports RACH communication of DL synchronization beam information for various DL-UL correspondence states, in accordance with various aspects of the present disclosure. The wireless device 805 may be an example of aspects of the UE 115 as described with reference to fig. 1. The wireless device 805 may include a receiver 810, a UE synchronization manager 815, and a transmitter 820. The wireless device 805 may also include a processor. Each of these components may be in communication with each other (e.g., via one or more buses).

Receiver 810 can receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to RACH communication of DL synchronization beam information for various DL-UL correspondence states, etc.). Information may be passed to other components of the device. The receiver 810 may be an example of aspects of the transceiver 1135 described with reference to fig. 11.

The UE synchronization manager 815 may be an example of aspects of the UE synchronization manager 1115 described with reference to fig. 11. The UE synchronization manager 815 may receive a DL synchronization signal from a base station on one or more DL synchronization beams and identify a selected DL beam of the one or more DL synchronization beams for communication from the base station to the UE.

The transmitter 820 may transmit signals generated by other components of the device. In some examples, the transmitter 820 may be co-located with the receiver 810 in a transceiver module. For example, the transmitter 820 may be an example of aspects of the transceiver 1135 described with reference to fig. 11. The transmitter 820 may include a single antenna, or it may include a set of antennas. The transmitter 820 may also transmit a RACH message/scheduling request message/beam recovery or beam tracking message to the base station using at least one of a selected resource or RACH waveform based at least in part on the selected DL beam. In some cases, transmitting the RACH message/scheduling request message/beam recovery or beam tracking message includes: the RACH message/scheduling request message/beam recovery or beam tracking message is transmitted during the entire duration of the corresponding random access subframe.

Fig. 9 illustrates a block diagram 900 of a wireless device 905 supporting RACH communication of DL synchronization beam information for various DL-UL correspondence states in accordance with various aspects of the present disclosure. The wireless device 905 may be an example of aspects of the wireless device 805 or UE 115 as described with reference to fig. 1 and 8. The wireless device 905 may include a receiver 910, a UE synchronization manager 915, and a transmitter 920. The wireless device 905 may also include a processor. Each of these components may be in communication with each other (e.g., via one or more buses).

Receiver 910 can receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to RACH communication of DL synchronization beam information for various DL-UL correspondence states, etc.). Information may be passed to other components of the device. The receiver 910 may be an example of aspects of the transceiver 1135 described with reference to fig. 11.

UE synchronization manager 915 may be an example of aspects of UE synchronization manager 1115 described with reference to fig. 11. UE synchronization manager 915 may also include a synchronization signal component 925, a beam selection component 930, and a resource selection component 935.

The synchronization signal component 925 may receive a DL synchronization signal from the base station on one or more DL synchronization beams. In some cases, the correspondence between one or more DL synchronization beams from the base station and one or more UL receive beams at the base station is absent. In some cases, the one or more DL synchronization beams are within a single symbol of a synchronization subframe, wherein selecting resources and/or RACH waveforms for transmission of RACH messages/scheduling request messages/beam recovery or beam tracking messages comprises: the resources and/or RACH waveform are selected based on the symbols of the selected DL beam.

The beam selection component 930 may identify a selected DL beam of the one or more DL synchronization beams for communication from the base station to the UE. In some cases, identifying the selected DL beam includes: the DL beams are identified based on the DL synchronization signals on the one or more DL synchronization beams satisfying a transmit power condition. In some cases, the selected DL beam from the base station is different from the selected UL beam from the UE. In some cases, the base station may identify a preferred UL beam based on the quality of the received RACH message. The base station may also transmit one or more subsequent messages to the UE, the one or more subsequent messages conveying an indication of a preferred UL beam.

Resource selection component 935 may select a resource and/or RACH waveform for transmission of a RACH message/scheduling request message/beam recovery or beam tracking message to a base station, the resource and/or RACH waveform selected based on the selected DL beam. In some cases, selecting a resource and/or RACH waveform includes: the resources and/or RACH waveform are selected based on the index of the selected DL beam. In some cases, selecting a resource and/or RACH waveform includes: the resources and/or RACH waveform are selected based on symbols of a subframe of the DL synchronization signal of the selected DL beam. In some cases, a resource is associated with one or more tones in a component carrier. In some cases, the resources are associated with component carriers.

Transmitter 920 may transmit signals generated by other components of the device. In some examples, the transmitter 920 may be co-located with the receiver 910 in a transceiver module. For example, the transmitter 920 may be an example of aspects of the transceiver 1135 described with reference to fig. 11. Transmitter 920 may include a single antenna, or it may include a set of antennas.

Fig. 10 illustrates a block diagram 1000 of a UE synchronization manager 1015 supporting RACH communication of DL synchronization beam information for various DL-UL correspondence states in accordance with various aspects of the present disclosure. The UE synchronization manager 1015 may be an example of aspects of the UE synchronization manager 815, the UE synchronization manager 915, or the UE synchronization manager 1115 described with reference to fig. 8, 9, and 11. The UE synchronization manager 1015 may include a synchronization signal component 1020, a beam selection component 1025, a resource selection component 1030, a preferred beam component 1035, a RACH waveform component 1040, and a correspondence management component 1045. Each of these modules may communicate with each other directly or indirectly (e.g., via one or more buses).

Synchronization signal component 1020 may receive a DL synchronization signal from a base station on one or more DL synchronization beams. The beam selection component 1025 may identify a selected DL beam of the one or more DL synchronization beams for communication from the base station to the UE. Resource selecting component 1030 may select a resource and/or RACH waveform for transmitting a RACH message/scheduling request message/beam recovery or beam tracking message to a base station, the resource and/or RACH waveform being selected based on a selected DL beam. In some cases, resource selecting component 1030 may select a resource and/or RACH waveform for transmitting a RACH message/scheduling request message/beam recovery or beam tracking message to a base station based on an indication that a correspondence between one or more DL synchronization beams from the base station and one or more UL receive beams at the base station is missing.

The preferred beam component 1035 may identify a preferred beam from among several beams transmitted by the base station. In some cases, identifying the selected DL beam includes: the preferred DL beam is identified based on a signal strength of the DL synchronization signal on the one or more DL synchronization beams, a signal quality of the DL synchronization signal on the one or more DL synchronization beams, or a combination thereof. The RACH waveform component 1040 may select a RACH waveform for transmission of a RACH message/scheduling request message/beam recovery or beam tracking message to the base station, the RACH waveform selected based on the selected DL beam. In some cases, selecting a RACH waveform includes: a RACH preamble, cyclic shift, or a combination thereof is selected based on the index of the selected DL beam.

Correspondence management component 1045 may receive an indication that a correspondence between one or more DL synchronization beams from a base station and one or more UL receive beams at the base station is missing. In some cases, correspondence management component 1045 may transmit a RACH message/scheduling request message/beam recovery or beam tracking message to the base station during an entire duration of a RACH subframe based at least in part on the indication of the missing correspondence. In some cases, correspondence management component 1045 may receive the indication in the MIB or SIB. In some cases, correspondence management component 1045 may transmit an indication that a correspondence between one or more DL synchronization beams from a base station and one or more UL receive beams at the base station is missing. In some cases, correspondence management component 1045 may transmit a RACH message/scheduling request message/beam recovery or beam tracking message to the base station during a first symbol of the first random access subframe and a second symbol of the second random access subframe. In some cases, correspondence management component 1045 may communicate an indication of the missing correspondence for the UE in RACH message 3, PUCCH, or PUSCH.

In some cases, correspondence management component 1045 may receive an indication of a characteristic of a correspondence between one or more DL synchronization beams from a base station and one or more UL beams from a UE. In some cases, the characteristic of the correspondence corresponds to one of: a full correspondence, a partial correspondence, or no correspondence. In some cases, correspondence management component 1045 may determine that a correspondence exists and select a transmission time for transmitting a RACH message/scheduling request message/beam recovery or beam tracking message to the base station based on the existence of the correspondence. In some cases, the transmission time includes a symbol of a corresponding random access subframe. In some cases, correspondence management component 1045 may determine that a partial correspondence exists and select a transmission time for transmitting a RACH message/scheduling request message/beam recovery or beam tracking message to the base station based on the partial correspondence. In some cases, a transmission time includes a plurality of symbols of a corresponding random access subframe. In some cases, the UE may transmit multiple RACH messages if there is no beam correspondence at the UE.

In some cases, the correspondence management component 1045 may select a transmission time, a frequency range, and a RACH preamble for transmitting the RACH message based on characteristics of the correspondence. In some cases, correspondence management component 1045 may select a resource or RACH waveform based at least in part on a symbol associated with the DL synchronization signal and an indication of a characteristic of the correspondence. In some cases, correspondence management component 1045 may receive an indication of characteristics of a correspondence on a PBCH or ePBCH. In some cases, correspondence management component 1045 may receive an indication of the characteristics of the correspondence in the MIB or SIB.

Fig. 11 illustrates a diagram of a system 1000 including a device 1105 supporting RACH communication of DL synchronization beam information for various DL-UL correspondence states in accordance with various aspects of the present disclosure. Device 1105 may be an example of or include components of wireless device 805, wireless device 905, or UE 115, e.g., as described above with reference to fig. 1, 8, and 9. The device 1105 may include components for two-way voice and data communications, including components for transmitting and receiving communications, including a UE synchronization manager 1115, a processor 1120, a memory 1125, software 1130, a transceiver 1135, an antenna 1140, and an I/O controller 1145. These components may be in electronic communication via one or more buses, such as bus 1110. The device 1105 may communicate wirelessly with one or more base stations 105.

Processor 1120 may include intelligent hardware devices (e.g., a general purpose processor, a Digital Signal Processor (DSP), a Central Processing Unit (CPU), a microcontroller, an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), a programmable logic device, discrete gate or transistor logic components, discrete hardware components, or any combination thereof). In some cases, the processor 1120 may be configured to operate a memory array using a memory controller. In other cases, the memory controller may be integrated into the processor 1120. The processor 1120 may be configured to execute computer-readable instructions stored in the memory to perform various functions (e.g., functions or tasks to support RACH communication of DL synchronization beam information for various DL-UL correspondence states).

Memory 1125 may include Random Access Memory (RAM) and Read Only Memory (ROM). Memory 1125 may store computer-readable, computer-executable software 1130 comprising instructions that, when executed, cause the processor to perform various functions described herein. In some cases, memory 1125 may contain, among other things, a basic input/output system (BIOS) that may control basic hardware and/or software operations, such as interaction with peripheral components or devices.

Software 1130 may include code for implementing aspects of the present disclosure, including code for supporting RACH communication of DL synchronization beam information for various DL-UL correspondence states. The software 1130 may be stored in a non-transitory computer readable medium, such as a system memory or other memory. In some cases, the software 1130 may not be directly executable by the processor, but may (e.g., when compiled and executed) cause the computer to perform the functions described herein.

The transceiver 1135 may communicate bi-directionally via one or more antennas, wired or wireless links, as described above. For example, the transceiver 1135 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 1135 may also include a modem to modulate packets and provide the modulated packets to the antennas for transmission, as well as demodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 1140. However, in some cases, the device may have more than one antenna 1140, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

I/O controller 1145 may manage input and output signals of device 1105. The I/O controller 1145 may also manage peripheral devices that are not integrated into the device 1105. In some cases, I/O controller 1145 may represent a physical connection or port to an external peripheral device. In some cases, I/O controller 1145 may utilize an operating system, such asMS-MS-OS/Or another known operating system.

Fig. 12 illustrates a block diagram 1200 of a wireless device 1205 that supports RACH communication of DL synchronization beam information for various DL-UL correspondence states in accordance with various aspects of the present disclosure. The wireless device 1205 may be an example of aspects of the base station 105 as described with reference to fig. 1. The wireless device 1205 may include a receiver 1210, a base station synchronization manager 1215, and a transmitter 1220. The wireless device 1205 may also include a processor. Each of these components may be in communication with each other (e.g., via one or more buses).

Receiver 1210 can receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to RACH communication of DL synchronization beam information for various DL-UL correspondence states, etc.). Information may be passed to other components of the device. The receiver 1210 may be an example of aspects of the transceiver 1535 described with reference to fig. 15.

The base station synchronization manager 1215 may be an example of aspects of the base station synchronization manager 1515 described with reference to fig. 15. The base station synchronization manager 1215 may transmit a DL synchronization signal on one or more DL synchronization beams, receive a RACH message/scheduling request message/beam recovery or beam tracking message from a UE on at least one of a resource or a RACH waveform, and identify a selected DL beam of the one or more DL synchronization beams for communication from the base station to the UE based on the resource and/or RACH waveform.

Transmitter 1220 may transmit signals generated by other components of the device. In some examples, the transmitter 1220 may be co-located with the receiver 1210 in a transceiver module. For example, the transmitter 1220 may be an example of aspects of the transceiver 1535 described with reference to fig. 15. The transmitter 1220 may include a single antenna, or it may include a set of antennas. The transmitter 1220 may also transmit one or more subsequent messages to the UE using the selected DL beam.

Fig. 13 illustrates a block diagram 1305 of a wireless device 1300 that supports RACH communication of DL synchronization beam information for various DL-UL correspondence states in accordance with various aspects of the present disclosure. The wireless device 1305 may be an example of aspects of the wireless device 1205 or the base station 105 as described with reference to fig. 1 and 12. Wireless device 1305 may include a receiver 1310, a base station synchronization manager 1315, and a transmitter 1320. The wireless device 1305 may also include a processor. Each of these components may be in communication with each other (e.g., via one or more buses).

Receiver 1310 can receive information such as packets, user data, or control information associated with various information channels (e.g., control channels, data channels, and information related to RACH communication of DL synchronization beam information for various DL-UL correspondence states, etc.). Information may be passed to other components of the device. The receiver 1310 may be an example of aspects of the transceiver 1535 described with reference to fig. 15.

The base station synchronization manager 1315 may be an example of aspects of the base station synchronization manager 1515 described with reference to fig. 15. Base station synchronization manager 1315 may also include a synchronization signal component 1325, a RACH component 1330, and a selected beam component 1335.

Synchronization signal component 1325 can transmit a DL synchronization signal on one or more DL synchronization beams. In some cases, the correspondence between one or more DL synchronization beams from the base station and one or more UL receive beams at the base station is missing.

RACH component 1330 may receive a RACH message/scheduling request message/beam recovery or beam tracking message from a UE on a resource and/or RACH waveform. In some cases, receiving the RACH message/scheduling request message/beam recovery or beam tracking message includes: receiving a RACH message/scheduling request message/beam recovery or beam tracking message during an entire duration of a corresponding random access subframe. In some cases, receiving the RACH message/scheduling request message/beam recovery or beam tracking message includes: a RACH message/scheduling request message/beam recovery or beam tracking message is received on a set of UL beams. In some cases, a resource is associated with one or more tones in a component carrier. In some cases, the resources are associated with component carriers.

A selected beam component 1335 may identify a selected DL beam of the one or more DL synchronization beams for communication from the base station to the UE based on the resources and/or RACH waveform. In some cases, identifying the selected DL beam includes: the resources and/or RACH waveforms are associated with the index of the selected DL beam. In some cases, identifying the selected DL beam includes: the resources and/or RACH waveforms are associated with symbols of a subframe of the DL synchronization signal of the selected DL beam. In some cases, identifying the selected DL beam further comprises: the selected DL beam is identified based on the RACH waveform of the RACH message/scheduling request message/beam recovery or beam tracking message. In some cases, identifying the selected DL beam includes: the selected DL beam is identified based on a RACH preamble of a RACH message, a cyclic shift of a RACH message, or a combination thereof. In some cases, the selected DL beam from the base station is different from the selected UL beam from the UE.

Transmitter 1320 may transmit signals generated by other components of the device. In some examples, the transmitter 1320 may be co-located with the receiver 1310 in a transceiver module. For example, the transmitter 1320 may be an example of aspects of the transceiver 1535 described with reference to fig. 15. The transmitter 1320 may include a single antenna, or it may include a set of antennas.

Fig. 14 illustrates a block diagram 1400 of a base station synchronization manager 1415 that supports RACH communication of DL synchronization beam information for various DL-UL correspondence states, in accordance with various aspects of the present disclosure. The base station synchronization manager 1415 may be an example of aspects of the base station synchronization manager 1515 described with reference to fig. 12, 13, and 15. Base station synchronization manager 1415 can include a synchronization signal component 1420, a RACH component 1425, a selected beam component 1430, a quality measurement component 1435, a UL beam component 1440, and a correspondence management component 1445. Each of these modules may communicate with each other directly or indirectly (e.g., via one or more buses).

Synchronization signal component 1420 may transmit a DL synchronization signal on one or more DL synchronization beams. The RACH component 1425 may receive a RACH message/scheduling request message/beam recovery or beam tracking message from the UE on at least one of a resource or a RACH waveform. The selected beam component 1430 may identify a selected DL beam of the one or more DL synchronization beams for communication from the base station to the UE based on the resource and/or RACH waveform.

Quality measuring component 1435 may measure the quality of RACH messages/scheduling request messages/beam recovery or beam tracking messages received on a set of UL beams. In some cases, measuring the quality of the RACH message/scheduling request message/beam recovery or beam tracking message includes: one or more of a Reference Signal Received Power (RSRP), a Received Signal Strength Indicator (RSSI), a Reference Signal Received Quality (RSRQ), a signal-to-noise ratio (SNR), or a signal-to-interference-plus-noise ratio (SINR) is measured. UL beam component 1440 may determine a selected UL beam to use for communication from the UE to the base station based on the quality.

Correspondence management component 1445 may transmit an indication that a correspondence between one or more DL synchronization beams from a base station and one or more UL receive beams at the base station is missing. In some cases, correspondence management component 1445 may transmit the indication in a MIB or SIB. In some cases, correspondence management component 1445 may receive an indication that a correspondence between one or more DL synchronization beams from a base station and one or more UL receive beams at the base station is missing and map DL beams used for transmitting CSI-RS to UL beams used for transmitting SRS or map UL beams used for transmitting SRS to DL beams used for transmitting CSI-RS. In some cases, correspondence management component 1445 may receive an indication that a correspondence between one or more DL synchronization beams from a base station and one or more UL receive beams at the base station is missing and map DL beams used in DL beam training to UL beams used in UL beam training or map UL beams used in UL beam training to DL beams used in DL beam training.

Fig. 15 illustrates a diagram of a system 1500 including a device 1505 that supports RACH communication of DL synchronization beam information for various DL-UL correspondence states in accordance with various aspects of the present disclosure. The device 1505 may be an example of or include the components of the base station 105 described above with reference to fig. 1, for example. The device 1505 may include components for two-way voice and data communications, including components for transmitting and receiving communications, including a base station synchronization manager 1515, a processor 1520, a memory 1525, software 1530, a transceiver 1535, an antenna 1540, a network communications manager 1545, and a base station communications manager 1550. These components may be in electronic communication via one or more buses, such as bus 1510. The device 1505 may communicate wirelessly with one or more UEs 115.

The processor 1520 may include intelligent hardware devices (e.g., a general purpose processor, a DSP, a CPU, a microcontroller, an ASIC, an FPGA, a programmable logic device, discrete gate or transistor logic components, discrete hardware components, or any combination thereof). In some cases, the processor 1520 may be configured to operate the memory array using a memory controller. In other cases, the memory controller may be integrated into the processor 1520. The processor 1520 may be configured to execute computer-readable instructions stored in the memory to perform various functions (e.g., functions or tasks to support RACH communication of DL synchronization beam information for various DL-UL correspondence states).

The memory 1525 may include RAM and ROM. The memory 1525 may store computer-readable, computer-executable software 1530 that includes instructions that, when executed, cause the processor to perform various functions described herein. In some cases, memory 1525 may contain, among other things, a BIOS, which may control basic hardware and/or software operations, such as interaction with peripheral components or devices.

Software 1530 may include code for implementing aspects of the present disclosure, including code for supporting RACH communication of DL synchronization beam information for various DL-UL correspondence states. The software 1530 may be stored in a non-transitory computer readable medium, such as system memory or other memory. In some cases, the software 1530 may not be directly executable by the processor, but may (e.g., when compiled and executed) cause the computer to perform the functions described herein.

The transceiver 1535 may communicate bi-directionally via one or more antennas, wired or wireless links, as described above. For example, the transceiver 1535 may represent a wireless transceiver and may communicate bi-directionally with another wireless transceiver. The transceiver 1535 may also include a modem to modulate packets and provide the modulated packets to the antennas for transmission, and to demodulate packets received from the antennas.

In some cases, the wireless device may include a single antenna 1540. However, in some cases, the device may have more than one antenna 1540, which may be capable of concurrently transmitting or receiving multiple wireless transmissions.

The network communications manager 1545 may manage communications with the core network (e.g., via one or more wired backhaul links). For example, the network communication manager 1545 may manage transmission of data communications for client devices (such as one or more UEs 115).

The base station communications manager 1550 may manage communications with other base stations 105 and may include a controller or scheduler for controlling communications with the UE 115 in cooperation with the other base stations 105. For example, the base station communication manager 1550 may coordinate scheduling of transmissions to the UE 115 for various interference mitigation techniques, such as beamforming or joint transmission. In some examples, the base station communications manager 1550 may provide an X2 interface within a Long Term Evolution (LTE)/LTE-a wireless communications network technology to provide communications between base stations 105.

Fig. 16 shows a flow diagram illustrating a method 1600 of RACH communication of DL synchronization beam information for various DL-UL correspondence states, in accordance with various aspects of the present disclosure. The operations of method 1600 may be implemented by UE 115 or components thereof as described herein. For example, the operations of method 1600 may be performed by a UE synchronization manager as described with reference to fig. 8 through 11. In some examples, the UE 115 may execute a set of codes to control the functional elements of the device to perform the functions described below. Additionally or alternatively, the UE 115 may use dedicated hardware to perform aspects of the functions described below.

At block 1605, the UE 115 may receive a DL synchronization signal from the base station on one or more DL synchronization beams. The operations of block 1605 may be performed in accordance with the methods described with reference to fig. 1-5. In some examples, aspects of the operations of block 1605 may be performed by the synchronization signal component as described with reference to fig. 8-11.

At block 1610, the UE 115 may identify a selected DL beam of the one or more DL synchronization beams for communication from the base station to the UE. The operations of block 1610 may be performed according to the methods described with reference to fig. 1-5. In some examples, aspects of the operations of block 1610 may be performed by a beam selection component as described with reference to fig. 8-11.

At block 1615, the UE 115 may transmit a RACH message/scheduling request message/beam recovery or beam tracking message to the base station using at least one of a selected resource or RACH waveform based at least in part on the selected DL beam. The operations of block 1615 may be performed according to the methods described with reference to fig. 1-5. In some examples, aspects of the operations of block 1615 may be performed by a transmitter as described with reference to fig. 8 through 11.

Fig. 17 shows a flow diagram illustrating a method 1700 of RACH communication of DL synchronization beam information for various DL-UL correspondence states, in accordance with various aspects of the present disclosure. The operations of method 1700 may be implemented by a UE 115 or components thereof as described herein. For example, the operations of method 1700 may be performed by a UE synchronization manager as described with reference to fig. 8 through 11. In some examples, the UE 115 may execute a set of codes to control the functional elements of the device to perform the functions described below. Additionally or alternatively, the UE 115 may use dedicated hardware to perform aspects of the functions described below.

At block 1705, the UE 115 may receive a DL synchronization signal from a base station on one or more DL synchronization beams. The operations of block 1705 may be performed according to the methods described with reference to fig. 1 through 5. In some examples, aspects of the operations of block 1705 may be performed by a synchronization signal component as described with reference to fig. 8 through 11.

At block 1710, the UE 115 may identify a selected DL beam of the one or more DL synchronization beams for communication from the base station to the UE. The operations of block 1710 may be performed according to the methods described with reference to fig. 1-5. In some examples, aspects of the operations of block 1710 may be performed by a beam selection component as described with reference to fig. 8-11.

At block 1715, the UE 115 may transmit a RACH message/scheduling request message/beam recovery or beam tracking message to the base station using at least one of a resource or RACH waveform selected based at least in part on the selected DL beam, which may also be selected based on the index of the selected DL beam. The operations of block 1715 may be performed according to the methods described with reference to fig. 1 through 5. In some examples, aspects of the operations of block 1715 may be performed by a transmitter as described with reference to fig. 8 through 11.

Fig. 18 shows a flow diagram illustrating a method 1800 of RACH communication of DL synchronization beam information for various DL-UL correspondence states, in accordance with various aspects of the present disclosure. The operations of method 1800 may be implemented by a base station 105 or components thereof as described herein. For example, the operations of method 1800 may be performed by a base station synchronization manager as described with reference to fig. 12-15. In some examples, the base station 105 may execute a set of codes for controlling the functional elements of the apparatus to perform the functions described below. Additionally or alternatively, the base station 105 may use dedicated hardware to perform aspects of the functions described below.

At block 1805, the base station 105 may transmit a DL synchronization signal on one or more DL synchronization beams. The operations of block 1805 may be performed in accordance with the methods described with reference to fig. 1 through 5. In certain examples, aspects of the operations of block 1805 may be performed by a synchronization signal component as described with reference to fig. 12-15.

At block 1810, the base station 105 may receive a RACH message/scheduling request message/beam recovery or beam tracking message from the UE on at least one of a resource or a RACH waveform. The operations of block 1810 may be performed according to the methods described with reference to fig. 1-5. In certain examples, aspects of the operations of block 1810 may be performed by the RACH assembly as described with reference to fig. 12-15.

At block 1815, the base station 105 may identify a selected DL beam of the one or more DL synchronization beams for communication from the base station to the UE based at least in part on the resource or RACH waveform. The operations of block 1815 may be performed according to the methods described with reference to fig. 1-5. In certain examples, aspects of the operations of block 1815 may be performed by the selected beam component as described with reference to fig. 12 to 15.

At block 1820, the base station 105 may transmit one or more subsequent messages to the UE using the selected DL beam. The operations of block 1820 may be performed according to the methods described with reference to fig. 1-5. In certain examples, aspects of the operations of block 1820 may be performed by a transmitter as described with reference to fig. 12-15.

Fig. 19 shows a flow diagram illustrating a method 1900 of RACH communication of DL synchronization beam information for various DL-UL correspondence states, in accordance with various aspects of the present disclosure. The operations of method 1900 may be implemented by a base station 105 or components thereof as described herein. For example, the operations of method 1900 may be performed by a base station synchronization manager as described with reference to fig. 12-15. In some examples, the base station 105 may execute a set of codes for controlling the functional elements of the apparatus to perform the functions described below. Additionally or alternatively, the base station 105 may use dedicated hardware to perform aspects of the functions described below.

At block 1905, the base station 105 may receive a RACH message/scheduling request message/beam recovery or beam tracking message from the UE on multiple UL beams on at least one of the resources or RACH waveform. The operations of block 1905 may be performed in accordance with the methods described with reference to fig. 1-5. In certain examples, aspects of the operations of block 1905 may be performed by a RACH assembly as described with reference to fig. 12-15.

At block 1910, the base station 105 may measure the quality of RACH messages/scheduling request messages/beam recovery or beam tracking messages received on multiple UL beams. The operations of block 1910 may be performed according to the methods described with reference to fig. 1-5. In certain examples, aspects of the operations of block 1910 may be performed by a quality measurement component as described with reference to fig. 12-15.

At block 1915, the base station 105 may determine or identify a selected UL beam (e.g., a preferred UL beam) for communication from the UE to the base station based at least in part on the measured quality of the RACH message. The base station may also transmit one or more subsequent messages to the UE, e.g., in RACH message 2, which convey an indication of a preferred UL beam. One or more subsequent messages to the UE may include an identification or index of the preferred UL beam (e.g., an OCC index). The operations of block 1915 may be performed according to the methods described with reference to fig. 1-5. In certain examples, aspects of the operations of block 1915 may be performed by the UL beam component as described with reference to fig. 12-15.

In some cases, receiving the RACH message/scheduling request message/beam recovery or beam tracking message includes: RACH messages/scheduling request messages/beam recovery or beam tracking messages are received on multiple UL beams.

It should be noted that the above method describes possible implementations, and that the operations and steps may be rearranged or otherwise modified and other implementations are possible. Further, aspects from two or more methods may be combined.

The techniques described herein may be used for various wireless communication systems such as Code Division Multiple Access (CDMA), Time Division Multiple Access (TDMA), Frequency Division Multiple Access (FDMA), Orthogonal Frequency Division Multiple Access (OFDMA), single carrier frequency division multiple access (SC-FDMA), and others. The terms "system" and "network" are often used interchangeably. Code Division Multiple Access (CDMA) systems may implement radio technologies such as CDMA2000, Universal Terrestrial Radio Access (UTRA), and the like. CDMA2000 covers IS2000, IS-95 and IS-856 standards. The IS-2000 version may often be referred to as CDMA 20001X, 1X, etc. IS-856(TIA-856) IS often referred to as CDMA 20001 xEV-DO, High Rate Packet Data (HRPD), etc. UTRA includes wideband CDMA (wcdma) and other CDMA variants. Time Division Multiple Access (TDMA) systems may implement radio technologies such as global system for mobile communications (GSM).

Orthogonal Frequency Division Multiple Access (OFDMA) systems may implement techniques such as Ultra Mobile Broadband (UMB), evolved UTRA (E-UTRA), Institute of Electrical and Electronics Engineers (IEEE)802.11(WiFi), IEEE 802.16(WiMAX), IEEE 802.20, Flash-OFDM^TMAnd so on. UTRA and E-UTRA are genericPart of a mobile telecommunications system (UMTS). 3GPP Long Term Evolution (LTE) and LTE-advanced (LTE-A) are new Universal Mobile Telecommunications System (UMTS) releases that use E-UTRA. UTRA, E-UTRA, UMTS, LTE-A, and Global System for Mobile communications (GSM) are described in literature from an organization named "third Generation partnership project" (3 GPP). CDMA2000 and UMB are described in documents from an organization named "third generation partnership project 2" (3GPP 2). The techniques described herein may be used for both the above-mentioned systems and radio technologies, as well as for other systems and radio technologies. Although aspects of the LTE system may be described for exemplary purposes, and LTE terminology is used in much of the description above, the techniques described herein may also be applied to applications other than LTE applications.

In LTE/LTE-a networks, including such networks described herein, the term evolved node B (eNB) may be used generically to describe a base station. One or more wireless communication systems described herein may include heterogeneous LTE/LTE-a networks, where different types of enbs provide coverage for various geographic regions. For example, each eNB or base station may provide communication coverage for a macro cell, a small cell, or other type of cell. The term "cell" may be used to describe a base station, a carrier or component carrier associated with a base station, or a coverage area (e.g., sector, etc.) of a carrier or base station, depending on the context.

A base station may include, or may be referred to by those skilled in the art as, a base transceiver station, a radio base station, an access point, a radio transceiver, a node B, an evolved node B (eNB), a home node B, a home evolved node B, or some other suitable terminology. The geographic coverage area of a base station may be partitioned into sectors that form only a portion of the coverage area. One or several wireless communication systems described herein may include different types of base stations (e.g., macro or small cell base stations). The UEs described herein may be capable of communicating with various types of base stations and network equipment, including macro enbs, small cell enbs, relay base stations, and the like. There may be overlapping geographic coverage areas of different technologies.

A macro cell generally covers a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs with service subscriptions with the network provider. Small cells are low power base stations that may operate in the same or different (e.g., licensed, unlicensed, etc.) frequency bands as macro cells as compared to macro cells. According to various examples, a small cell may include a picocell, a femtocell, and a microcell. Picocells, for example, may cover a small geographic area and may allow unrestricted access by UEs with service subscriptions with the network provider. A femtocell may also cover a smaller geographic area (e.g., a residence) and may be provided access restricted by UEs associated with the femtocell (e.g., UEs in a Closed Subscriber Group (CSG), UEs of users in the residence, etc.). The eNB for a macro cell may be referred to as a macro eNB. An eNB for a small cell may be referred to as a small cell eNB, pico eNB, femto eNB, or home eNB. An eNB may support one or more (e.g., two, three, four, etc.) cells (e.g., component carriers). The UE may be capable of communicating with various types of base stations and network equipment, including macro enbs, small cell enbs, relay base stations, and the like.

One or more of the wireless communication systems described herein may support synchronous or asynchronous operation. For synchronous operation, each base station may have similar frame timing, and transmissions from different base stations may be approximately aligned in time. For asynchronous operation, each base station may have different frame timing, and transmissions from different base stations may not be aligned in time. The techniques described herein may be used for synchronous or asynchronous operations.

The downlink transmissions described herein may also be referred to as forward link transmissions, while the uplink transmissions may also be referred to as reverse link transmissions. Each of the communication links described herein, including, for example, the wireless communication systems 100 and 200 of fig. 1 and 2, may include one or more carriers, where each carrier may be a signal (e.g., a waveform signal of a different frequency) made up of a plurality of subcarriers.

The illustrations set forth herein in connection with the figures describe example configurations and are not intended to represent all examples that may be implemented or fall within the scope of the claims. The term "exemplary" as used herein means "serving as an example, instance, or illustration," and does not mean "preferred" or "advantageous over other examples. The detailed description includes specific details to provide an understanding of the described technology. However, the techniques may be practiced without these specific details. In some instances, well-known structures and devices are shown in block diagram form in order to avoid obscuring the concepts of the described examples.

In the drawings, similar components or features may have the same reference numerals. Further, various components of the same type may be distinguished by following the reference label by a dash and a second label that distinguishes among the similar components. If only the first reference label is used in the specification, the description is applicable to any one of the similar components having the same first reference label irrespective of the second reference label.

Information and signals described herein may be represented using any of a variety of different technologies and techniques. For example, data, instructions, commands, information, signals, bits, symbols, and chips that may be referenced throughout the above description may be represented by voltages, currents, electromagnetic waves, magnetic fields or particles, optical fields or particles, or any combination thereof.

The various illustrative blocks and modules described in connection with the disclosure herein may be implemented or performed with a general purpose processor, a DSP, an ASIC, an FPGA or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices (e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration).

The functions described herein may be implemented in hardware, software executed by a processor, firmware, or any combination thereof. If implemented in software executed by a processor, the functions may be stored on or transmitted over as one or more instructions or code on a computer-readable medium. Other examples and implementations are within the scope of the disclosure and the following claims. For example, due to the nature of software, the functions described above may be implemented using software executed by a processor, hardware, firmware, hard wiring, or any combination thereof. Features that implement functions may also be physically located at various locations, including being distributed such that portions of functions are implemented at different physical locations. In addition, as used herein, including in the claims, "or" as used in a list of items (e.g., a list of items accompanied by a phrase such as "at least one of" or "one or more of") indicates an inclusive list, such that, for example, a list of at least one of A, B or C means a or B or C or AB or AC or BC or ABC (i.e., a and B and C). Also, as used herein, the phrase "based on" should not be read as referring to a closed condition set. For example, an exemplary step described as "based on condition a" may be based on both condition a and condition B without departing from the scope of the present disclosure. In other words, the phrase "based on," as used herein, should be interpreted in the same manner as the phrase "based, at least in part, on.

Computer-readable media includes both non-transitory computer storage media and communication media, including any medium that facilitates transfer of a computer program from one place to another. Non-transitory storage media may be any available media that can be accessed by a general purpose or special purpose computer. By way of example, and not limitation, non-transitory computer-readable media can comprise RAM, ROM, electrically erasable programmable read-only memory (EEPROM), Compact Disk (CD) ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other non-transitory medium that can be used to carry or store desired program code means in the form of instructions or data structures and that can be accessed by a general-purpose or special-purpose computer, or a general-purpose or special-purpose processor. Any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a web site, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL), or wireless technologies such as infrared, radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL), or wireless technologies such as infrared, radio, and microwave are included in the definition of medium. Disk (disk) and disc (disc), as used herein, includes CD, laser disc, optical disc, Digital Versatile Disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above are also included within the scope of computer-readable media.

The description herein is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to the disclosure will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the scope of the disclosure. Thus, the disclosure is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for wireless communication at a User Equipment (UE), comprising:

receiving a Downlink (DL) signal from a base station on one or more DL beams of the base station;

identifying characteristics of beam correspondence between one or more receive beams at the UE and one or more transmit beams at the UE;

identifying a selected DL beam of the one or more DL beams of the base station for communication from the base station to the UE; and

transmitting a message to the base station indicating characteristics of the beam correspondence, wherein the message is transmitted based at least in part on the selected DL beam of the base station and characteristics of the beam correspondence between one or more receive beams at the UE and one or more transmit beams at the UE.

2. The method of claim 1, further comprising:

selecting resources for transmitting the message to the base station, wherein the resources comprise time resources, frequency resources, or time-frequency resources.

3. The method of claim 1, wherein the message comprises a RACH message 1(msg 1).

4. The method of claim 1, wherein the characteristics of the beam correspondence comprise at least one of: a full correspondence, partial correspondence, or correspondence is missing.

5. The method of claim 4, further comprising:

determining that a complete correspondence exists; and

selecting a resource or RACH waveform for transmitting the message to the base station based on the full correspondence, wherein a DL beam is mapped to the resource or the RACH waveform.

6. The method of claim 4, further comprising:

determining that a partial correspondence exists or no correspondence exists; and

selecting a transmission time or RACH waveform for transmitting the message to the base station based on the partial correspondence or no correspondence, wherein the transmission time comprises a symbol of a corresponding random access subframe.

7. The method of claim 4, further comprising:

determining that a partial correspondence exists; and

selecting a transmission time for transmitting the message to the base station based on the partial correspondence, wherein the transmission time comprises a plurality of symbols of a corresponding random access subframe.

8. The method of claim 4, further comprising:

transmitting a plurality of instances of the message to the base station based at least in part on the partial correspondence or no correspondence, wherein the plurality of instances of the message are transmitted prior to receiving a subsequent message from the base station.

9. The method of claim 4, further comprising:

selecting a resource or RACH waveform based at least in part on a symbol associated with the DL signal and a characteristic of the beam correspondence.

10. The method of claim 1, further comprising:

selecting one or more of a transmission time, a frequency range, and a RACH preamble for transmitting the message based at least in part on a characteristic of the beam correspondence.

11. The method of claim 1, further comprising:

selecting a resource or RACH waveform based at least in part on the index of the selected DL beam.

12. The method of claim 1, wherein when the characteristic of the beam correspondence between the one or more receive beams at the UE and the one or more transmit beams at the UE is missing, the missing beam correspondence is associated with the one or more receive beams having a different channel propagation characteristic than the one or more transmit beams.

13. The method of claim 1, further comprising:

mapping a reception beam for transmitting a channel state information reference signal (CSI-RS) to a transmission beam for transmitting a Sounding Reference Signal (SRS), or mapping a transmission beam for transmitting an SRS to a reception beam for transmitting the CSI-RS.

14. The method of claim 1, further comprising:

mapping a receive beam used in DL beam training to an Uplink (UL) beam used in UL beam training or mapping the UL beam used in the UL beam training to the DL beam used in the DL beam training.

15. The method of claim 1, wherein the DL signal comprises a synchronization signal or a reference signal.

16. A method for wireless communication at a User Equipment (UE), comprising:

identifying a characteristic of a beam correspondence between one or more receive beams at the UE and one or more transmit beams at the UE based at least in part on one or more signals received on one or more downlink beams of a base station; and

transmitting a Random Access Channel (RACH) message to the base station based at least in part on the characteristic of the beam correspondence, wherein a resource or RACH waveform of the RACH message conveys the characteristic of the beam correspondence.

17. The method of claim 16, wherein the RACH message comprises RACH message 1(msg1) or RACH message 3(msg3) of a RACH procedure.

18. The method of claim 16, wherein the RACH message conveys a characteristic of the beam correspondence.

19. The method of claim 16, wherein the characteristics of the beam correspondence comprise at least one of: a full correspondence, partial correspondence, or correspondence is missing.

20. The method of claim 16, wherein transmitting the RACH message comprises:

the RACH message is transmitted during the entire duration of the corresponding random access subframe.

21. A method for wireless communications at a base station, comprising:

transmitting a Downlink (DL) signal to a User Equipment (UE) on one or more DL beams of the base station;

receiving a Random Access Channel (RACH) message from the UE on a plurality of Uplink (UL) beams on at least one of a resource or a RACH waveform, wherein the at least one of the resource or RACH waveform is based at least in part on characteristics of a beam correspondence between at least one of the UL beams at the UE and one or more receive beams at the UE, wherein the resource or the RACH waveform of the RACH message conveys characteristics of the beam correspondence;

identifying a selected DL beam of the one or more DL beams for communication from the base station to the UE based at least in part on the resource or the RACH waveform; and

transmitting one or more subsequent messages to the UE using the selected DL beam.

22. The method of claim 21, wherein the RACH message comprises a RACH message 1(msg 1).

23. The method of claim 21, wherein receiving the RACH message comprises: receiving the RACH message during an entire duration of a corresponding random access subframe.

24. The method of claim 21, further comprising:

measuring a quality of the RACH message received on the plurality of UL beams; and

determining a selected UL beam for communication from the UE to the base station based at least in part on the quality.

25. An apparatus for wireless communication at a User Equipment (UE), comprising:

means for receiving Downlink (DL) signals from a base station on one or more DL beams of the base station;

means for identifying characteristics of beam correspondence between one or more receive beams at the UE and one or more transmit beams at the UE;

means for identifying a selected DL beam of the one or more DL beams of the base station for communication from the base station to the UE; and

means for transmitting a message to the base station indicating characteristics of the beam correspondence, wherein the message is transmitted based at least in part on the selected DL beam of the base station and characteristics of the beam correspondence between one or more receive beams at the UE and one or more transmit beams at the UE.

26. The apparatus of claim 25, wherein the characteristics of the beam correspondence comprise at least one of: a full correspondence, partial correspondence, or correspondence is missing.

27. The apparatus of claim 26, further comprising:

means for determining that there is a full correspondence; and

means for selecting a resource or RACH waveform for transmitting the message to the base station based on the full correspondence, wherein a DL beam is mapped to the resource or the RACH waveform.

28. The apparatus of claim 26, further comprising:

means for determining that there is a partial correspondence or no correspondence; and

means for selecting a transmission time or RACH waveform for transmitting the message to the base station based on the partial correspondence or no correspondence, wherein the transmission time comprises a symbol of a corresponding random access subframe.

29. The apparatus of claim 26, further comprising:

means for determining that a partial correspondence exists; and

means for selecting a transmission time for transmitting the message to the base station based on the partial correspondence, wherein the transmission time comprises a plurality of symbols of a corresponding random access subframe.

30. The apparatus of claim 26, further comprising:

means for transmitting a plurality of instances of the message to the base station based at least in part on the partial correspondence or no correspondence, wherein the plurality of instances of the message are transmitted prior to receiving a subsequent message from the base station.

31. The apparatus of claim 26, further comprising:

means for selecting a resource or RACH waveform based at least in part on a symbol associated with the DL signal and a characteristic of the beam correspondence.

32. The apparatus of claim 25, further comprising:

means for selecting one or more of a transmission time, a frequency range, and a RACH preamble for transmitting the message based at least in part on a characteristic of the beam correspondence.

33. The apparatus of claim 25, further comprising:

means for selecting a resource or RACH waveform based at least in part on an index of the selected DL beam.

34. The apparatus of claim 25, further comprising:

means for mapping a receive beam for transmitting a channel state information reference signal (CSI-RS) to a transmit beam for transmitting a Sounding Reference Signal (SRS), or mapping a transmit beam for transmitting an SRS to a receive beam for transmitting a CSI-RS.

35. The apparatus of claim 25, further comprising:

means for mapping a receive beam used in DL beam training to an Uplink (UL) beam used in UL beam training or mapping the UL beam used in the UL beam training to the DL beam used in the DL beam training.

36. An apparatus for wireless communication at a User Equipment (UE), comprising:

means for identifying a characteristic of a beam correspondence between one or more receive beams at the UE and one or more transmit beams at the UE based at least in part on one or more signals received on one or more downlink beams of a base station; and

means for transmitting a Random Access Channel (RACH) message to the base station based at least in part on the characteristic of the beam correspondence, wherein a resource or RACH waveform of the RACH message conveys the characteristic of the beam correspondence.

37. The apparatus of claim 36, wherein transmitting the RACH message comprises:

means for transmitting the RACH message during an entire duration of a corresponding random access subframe.

38. An apparatus for wireless communication at a base station, comprising:

means for transmitting Downlink (DL) signals on one or more DL beams of the base station to a User Equipment (UE);

means for receiving a Random Access Channel (RACH) message from the UE on a plurality of Uplink (UL) beams on at least one of a resource or a RACH waveform, wherein the at least one of the resource or RACH waveform is based at least in part on characteristics of beam correspondence between at least one of the UL beams at the UE and one or more receive beams at the UE, wherein the resource or the RACH waveform of the RACH message conveys characteristics of the beam correspondence;

means for identifying a selected DL beam of the one or more DL beams for communication from the base station to the UE based at least in part on the resource or the RACH waveform; and

means for transmitting one or more subsequent messages to the UE using the selected DL beam.

39. The apparatus of claim 38, wherein the means for receiving the RACH message comprises: means for receiving the RACH message during an entire duration of a corresponding random access subframe.

40. The apparatus of claim 38, further comprising:

means for measuring a quality of the RACH message received on the plurality of UL beams; and

means for determining a selected UL beam for communication from the UE to the base station based at least in part on the quality.