WO2022010595A1

WO2022010595A1 - Inter-radio access technology channel estimation

Info

Publication number: WO2022010595A1
Application number: PCT/US2021/035019
Authority: WO
Inventors: Jibing Wang; Erik Richard Stauffer
Original assignee: Google LLC
Current assignee: Google LLC
Priority date: 2020-07-06
Filing date: 2021-05-28
Publication date: 2022-01-13
Anticipated expiration: 2023-01-06

Abstract

This document describes techniques of inter-radio access technology channel estimation for using Quasi Co-Location, QCL, to improve channel estimates for signals of a second radio access technology, RAT, by using the results of a channel estimate for signals of a first RAT. A second base station (123) receives a pilot signal configuration for a first antenna port for a first RAT from a first base station (122). The second base station (123) determines QCL information for a second antenna port for a second RAT based on the received pilot signal configuration for the first RAT. The second base station (123) transmits the QCL information to a user equipment (111), the transmitting directing the user equipment (111) to use the QCL information to estimate a channel condition for the second RAT and the second base station (123) transmits a downlink channel to the user equipment (111) using the second RAT.

Description

INTER-RADIO ACCESS TECHNOLOGY CHANNEL ESTIMATION

BACKGROUND

[0001] The evolution of wireless communication to fifth generation (5G) and sixth generation (6G) standards and technologies provides higher data rates and greater capacity with improved reliability and lower latency which enhances mobile broadband services. 5G and 6G technologies also provide new classes of services for vehicular networking, fixed wireless broadband, and the Internet of Things (IoT).

[0002] A unified air interface, which utilizes licensed, unlicensed, and shared license radio spectrum in multiple frequency bands is one aspect of enabling the capabilities of 5G and 6G systems. The unified air interface utilizes radio spectrum in bands below 1 GHz (sub-gigahertz), below 6 GHz (sub-6 GHz), and above 6 GHz. Radio spectrum above 6 GHz includes millimeter wave (mmWave) frequency bands that provide wide channel bandwidths to support higher data rates for wireless broadband. In some radio spectrum bands, existing Long Term Evolution (LTE) systems share the radio spectrum with 5G and 6G systems by using orthogonal resource partitioning based on time, space (antenna beam), or bandwidth parts to divide the radio resources between the different radio access technologies (RATs).

[0003] Within a single RAT, a user equipment can use quasi co-location (QCL) to improve channel estimates by using a channel estimate for first signal from a first antenna port to improve the channel estimate for a second signal from a second antenna port. However, in systems with orthogonalized spectrum sharing, there is an opportunity to employ QCL across two different RATs.

SUMMARY

[0004] This summary introduces simplified concepts of inter-radio access technology channel estimation. The simplified concepts are further described below in the Detailed Description. This summary is not intended to identify essential features of the claimed subject matter, nor is it intended for use in determining the scope of the claimed subject matter.

[0005] In aspects, methods, devices, systems, and means for coordinating channel estimation are described in which a second base station receives a pilot signal configuration for a first antenna port for a first radio access technology (RAT) from a first base station. The second base station determines quasi co-location (QCL) information for a second antenna port for a second RAT based on the received pilot signal configuration for the first RAT. The second base station transmits the QCL information to a user equipment, the transmitting directing the user equipment to use the QCL information to estimate a channel condition for the second RAT and the second base station transmits a downlink channel to the user equipment using the second RAT, the downlink channel being decodable by the UE using the estimated channel condition for the second RAT.

[0006] In other aspects, methods, devices, systems, and means for estimating a channel by a user equipment are described in which the user equipment receives quasi co-location (QCL) information from a second base station for a second radio access technology (RAT) based on a pilot signal configuration for a first RAT. The user equipment receives one or more pilot signals from a first base station using the first RAT and receives downlink signals from the second base station using the second RAT. The user equipment estimates a channel between the first base station and the UE based on the received one or more pilot signals and the QCL information and based on the estimating the channel between the first base station and the UE, decodes the received downlink signals from the second base station.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] Aspects of inter-radio access technology channel estimation are described with reference to the following drawings. The same numbers are used throughout the drawings to reference like features and components:

FIG. 1 illustrates an example wireless network environment in which various aspects of inter-radio access technology channel estimation can be implemented.

FIG. 2 illustrates an example device diagram that can implement various aspects of inter-radio access technology channel estimation.

FIG. 3 illustrates an air interface resource that extends between a user equipment and a base station and with which various aspects of inter-radio access technology channel estimation techniques can be implemented.

FIG. 4 illustrates example details of data and control transactions between devices of inter-radio access technology channel estimation in accordance with aspects of the techniques described herein.

FIG. 5 illustrates an example method of inter-radio access technology channel estimation as generally related to as generally related to coordinating channel estimation between a first radio access technology and a second radio access technology by a base station in accordance with aspects of the techniques described herein.

FIG. 6 illustrates an example method of inter-radio access technology channel estimation as generally related to estimating a channel by a user equipment in accordance with aspects of the techniques described herein. DETAILED DESCRIPTION

Overview

[0008] This document describes techniques of inter-radio access technology channel estimation for using quasi co-location (QCL) to improve channel estimates for signals of a second radio access technology (RAT) by using the results of a channel estimate for signals of a first RAT. A second base station receives a pilot signal configuration for a first antenna port for a first radio access technology from a first base station. The second base station determines quasi co- location information for a second antenna port for a second RAT based on the received pilot signal configuration for the first RAT. The second base station transmits the quasi co-location information to a user equipment, the transmitting directing the user equipment to use the quasi co- location information to estimate a channel condition for the second RAT and the second base station transmits a downlink channel to the user equipment using the second RAT.

[0009] In deploying a newer radio access technology, a network operator can deploy the newer RAT in the same portion of radio spectrum as a previous generation RAT. For example, a network operator can deploy a Fifth Generation New Radio (5GNR) RAT in radio spectrum where the network operator has previously deployed 3rd Generation Partnership Project Long- Term Evolution (3 GPP LTE) or in future evolutions, the network operator may deploy a sixth generation RAT in radio spectrum with a 5GNR RAT deployment.

[0010] One approach to deploying a newer RAT and a previous-generation RAT in the same radio spectrum utilizes an orthogonal allocation of air interface resources between the two RATs. The RATs share the radio spectrum using a time-based or frequency -based partitioning of the air interface resources between the two RATs. These partitionings typically provide a static partitioning of resources that can lead to an inefficient utilization of the radio spectrum.

[0011] Within a single RAT, user equipment can use quasi co-location (QCL) information to improve channel estimates by taking a channel estimate for a first signal from a first antenna port of a base station downlink to improve the channel estimate for a second signal from a second antenna port of the base station. In systems with orthogonalized spectrum sharing between two RATs, channel estimates for signals of one RAT cannot use intra-RAT QCL to improve channel estimates for signals in the second RAT. In aspects, in wireless networks that employ non- orthogonal sharing of air interface resources between two RATs, a user equipment connected using the second RAT can use the pilot signals (reference signals) from the first RAT to enhance time and frequency tracking as well as channel and interference estimation for downlink signals in the second RAT.

[0012] While features and concepts of the described systems and methods for inter-radio access technology channel estimation can be implemented in any number of different environments, systems, devices, and/or various configurations, aspects of inter-radio access technology channel estimation are described in the context of the following example devices, systems, and configurations.

Example Environment

[0013] FIG. 1 illustrates an example environment 100, which includes multiple user equipment 110 (UE 110), illustrated as UE 111, UE 112, and UE 113. Each UE 110 can communicate with base stations 120 (illustrated as base stations 121, 122, 123, and 124) through one or more wireless communication links 130 (wireless link 130), illustrated as wireless links 131 and 132. For simplicity, the UE 110 is implemented as a smartphone but may be implemented as any suitable computing or electronic device, such as a mobile communication device, modem, cellular phone, gaming device, navigation device, media device, laptop computer, desktop computer, tablet computer, smart appliance, vehicle-based communication system, or an Intemet- of-Things (IoT) device such as a sensor or an actuator. The base stations 120 (e.g., an Evolved Universal Terrestrial Radio Access Network Node B, E-UTRAN Node B, evolved Node B, eNodeB, eNB, Next Generation Node B, gNode B, gNB, ng-eNB, or the like) may be implemented in a macrocell, microcell, small cell, picocell, distributed base station, or the like, or any combination or future evolution thereof.

[0014] The base stations 120 communicate with the UE 110 using the wireless links 131 and 132, which may be implemented as any suitable type of wireless link. The wireless links 131 and 132 include control and data communication, such as downlink of data and control information communicated from the base stations 120 to the UE 110, uplink of other data and control information communicated from the UE 110 to the base stations 120, or both. The wireless links 130 may include one or more wireless links (e.g., radio links) or bearers implemented using any suitable communication protocol or standard, or combination of communication protocols or standards, for example 3rd Generation Partnership Project Long-Term Evolution (3GPP LTE), Fifth Generation New Radio (5GNR), and future evolutions. Multiple wireless links 130 may be aggregated in a carrier aggregation or multi-connectivity to provide a higher data rate for the UE 110. Multiple wireless links 130 from multiple base stations 120 may be configured for Coordinated Multipoint (CoMP) communication with the UE 110.

[0015] The base stations 120 are collectively a Radio Access Network 140 (e.g., RAN, Evolved Universal Terrestrial Radio Access Network, E-UTRAN, 5GNR RAN or NR RAN). The RANs 140 are illustrated as an NR RAN 141 and an E-UTRAN 142. The base stations 121 and 123 in the NR RAN 141 are connected to a Fifth Generation Core 150 (5GC 150) network. The base stations 122 and 124 in the E-UTRAN 142 are connected to an Evolved Packet Core 160 (EPC 160). Optionally or additionally, the base station 122 may connect to both the 5GC 150 and EPC 160 networks.

[0016] The base stations 121 and 123 connect, at 102 and 104 respectively, to the 5GC 150 through an NG2 interface for control-plane signaling and using an NG3 interface for user- plane data communications. The base stations 122 and 124 connect, at 106 and 108 respectively, to the EPC 160 using an SI interface for control-plane signaling and user-plane data communications. Optionally or additionally, if the base station 122 connects to the 5GC 150 and EPC 160 networks, the base station 122 connects to the 5GC 150 using an NG2 interface for control -plane signaling and through an NG3 interface for user-plane data communications, at 180.

[0017] In addition to connections to core networks, the base stations 120 may communicate with each other. For example, the base stations 121 and 123 communicate using an Xn Application Protocol (XnAP) through an Xn interface at 103, the base stations 122 and 123 communicate through an Xn interface at 105, and the base stations 122 and 124 communicate through an X2 interface at 107.

[0018] The 5GC 150 includes an Access and Mobility Management Function 152 (AMF 152), which provides control-plane functions, such as registration and authentication of multiple UE 110, authorization, and mobility management in the 5GNR network. The EPC 160 includes a Mobility Management Entity 162 (MME 162), which provides control-plane functions, such as registration and authentication of multiple UE 110, authorization, or mobility management in the E-UTRA network. The AMF 152 and the MME 162 communicate with the base stations 120 in the RANs 140 and also communicate with multiple UE 110, using the base stations 120.

Example Devices

[0019] FIG. 2 illustrates an example device diagram 200 of the user equipment 110 and the base stations 120. The user equipment 110 and the base stations 120 may include additional functions and interfaces that are omitted from FIG. 2 for the sake of clarity. The user equipment 110 includes antennas 202, a radio frequency front end 204 (RF front end 204), an LTE transceiver 206, and a 5G NR transceiver 208 for communicating with base stations 120 in the RAN 140. The RF front end 204 of the user equipment 110 can couple or connect the LTE transceiver 206, and the 5GNR transceiver 208 to the antennas 202 to facilitate various types of wireless communication. The antennas 202 of the user equipment 110 may include an array of multiple antennas that are configured similar to or differently from each other. The antennas 202 and the RF front end 204 can be tuned to, and/or be tunable to, one or more frequency bands defined by the 3GPP LTE and 5GNR communication standards and implemented by the LTE transceiver 206, and/or the 5G NR transceiver 208. Additionally, the antennas 202, the RF front end 204, the LTE transceiver 206, and/or the 5GNR transceiver 208 may be configured to support beamforming for the transmission and reception of communications with the base stations 120. By way of example and not limitation, the antennas 202 and the RF front end 204 can be implemented for operation in sub-gigahertz bands, sub-6 GHZ bands, and/or above 6 GHz bands that are defined by the 3GPP LTE and 5GNR communication standards.

[0020] The user equipment 110 also includes processor(s) 210 and computer-readable storage media 212 (CRM 212). The processor 210 may be a single core processor or a multiple core processor composed of a variety of materials, such as silicon, polysilicon, high-K dielectric, copper, and so on. The computer-readable storage media described herein excludes propagating signals. CRM 212 may include any suitable memory or storage device such as random-access memory (RAM), static RAM (SRAM), dynamic RAM (DRAM), non-volatile RAM (NVRAM), read-only memory (ROM), or Flash memory useable to store device data 214 of the user equipment 110. The device data 214 includes user data, multimedia data, beamforming codebooks, applications, and/or an operating system of the user equipment 110, which are executable by processor(s) 210 to enable user-plane communication, control-plane signaling, and user interaction with the user equipment 110.

[0021] In some implementations, the CRM 212 may also include a channel estimator 216. Alternately or additionally, the channel estimator 216 may be implemented in whole or part as hardware logic or circuitry integrated with or separate from other components of the user equipment 110. The channel estimator 216 can communicate with the antennas 202, the RF front end 204, the LTE transceiver 206, and/or the 5G NR transceiver 208 to implement techniques for inter-radio access technology channel estimation described herein.

[0022] One or more codebooks are shared between the UE 110 and the base station 120. The codebooks 218 can include a codebook that includes precoding matrices for beamforming with an index value (e.g., a precoding matrix indicator or PMI) associated with each precoding matrix. The codebooks 218 may also include an inter-RAT codebook that includes relative phase difference between the antenna ports of a first RAT pilot channel and antenna ports of a second RAT pilot channel or data channel, such that the first RAT pilot signals can be used to derive a channel estimation for second RAT downlink. The CRM 212 of the user equipment 110 and the CRM 262 of the base station 120 can store the codebook(s) 218.

[0023] The device diagram for the base stations 120, shown in FIG. 2, includes a single network node (e.g., a gNode B). The functionality of the base stations 120 may be distributed across multiple network nodes or devices and may be distributed in any fashion suitable to perform the functions described herein. The base stations 120 include antennas 252, a radio frequency front end 254 (RF front end 254), one or more LTE transceivers 256, and/or one or more 5GNR transceivers 258 for communicating with the UE 110. The RF front end 254 of the base stations 120 can couple or connect the LTE transceivers 256 and the 5GNR transceivers 258 to the antennas 252 to facilitate various types of wireless communication. The antennas 252 of the base stations 120 may include an array of multiple antennas that are configured similar to or differently from each other. The antennas 252 and the RF front end 254 can be tuned to, and/or be tunable to, one or more frequency bands defined by the 3GPP LTE and 5G NR communication standards and implemented by the LTE transceivers 256, and/or the 5G NR transceivers 258. Additionally, the antennas 252, the RF front end 254, the LTE transceivers 256, and/or the 5G NR transceivers 258 may be configured to support beamforming, such as Massive-MIMO, for the transmission and reception of communications with the UE 110. In some aspects, a base station 120 that supports LTE and 5G NR spectrum sharing may employ common antennas, common amplifiers, common baseband circuitry, and/or other common components for both LTE and 5GNR.

[0024] The base stations 120 also include processor(s) 260 and computer-readable storage media 262 (CRM 262). The processor 260 may be a single core processor or a multiple core processor composed of a variety of materials, such as silicon, polysilicon, high-K dielectric, copper, and so on. CRM 262 may include any suitable memory or storage device such as random- access memory (RAM), static RAM (SRAM), dynamic RAM (DRAM), non-volatile RAM (NVRAM), read-only memory (ROM), or Flash memory useable to store device data 264 of the base stations 120. The device data 264 includes network scheduling data, radio resource management data, beamforming codebooks, applications, and/or an operating system of the base stations 120, which are executable by processor(s) 260 to enable communication with the user equipment 110.

[0025] CRM 262 also includes a base station manager 266. Alternately or additionally, the base station manager 266 may be implemented in whole or part as hardware logic or circuitry integrated with or separate from other components of the base stations 120. In at least some aspects, the base station manager 266 configures the LTE transceivers 256 and the 5GNR transceivers 258 for communication with the user equipment 110, as well as communication with a core network, such as the core network 150. The base station manager 266 can implement the techniques for inter-radio access technology channel estimation described herein.

[0026] The base stations 120 include an inter-base station interface 268, such as an Xn and/or X2 interface, which the base station manager 266 configures to exchange user-plane and control -plane data between other base stations 120, to manage the communication of the base stations 120 with the user equipment 110. The base stations 120 include a core network interface 270 that the base station manager 266 configures to exchange user-plane and control-plane data with core network functions and/or entities. Air Interface Resources

[0027] FIG. 3 illustrates an air interface resource that extends between a user equipment and a base station and with which various aspects of inter-radio access technology channel estimation can be implemented. The air interface resource 302 can be divided into resource units 304, each of which occupies some intersection of frequency spectrum and elapsed time. A portion of the air interface resource 302 is illustrated graphically in a grid or matrix having multiple resource blocks 310, including example resource blocks 311, 312, 313, 314. An example of a resource unit 304 therefore includes at least one resource block 310. As shown, time is depicted along the horizontal dimension as the abscissa axis, and frequency is depicted along the vertical dimension as the ordinate axis. The air interface resource 302, as defined by a given communication protocol or standard, may span any suitable specified frequency range, and/or may be divided into intervals of any specified duration. Increments of time can correspond to, for example, milliseconds (mSec). Increments of frequency can correspond to, for example, megahertz (MHz).

[0028] In example operations generally, the base stations 120 allocate portions (e.g., the resource units 304) of the air interface resource 302 for uplink and downlink communications. Each resource block 310 of network access resources may be allocated to support respective wireless communication links 130 of multiple user equipment 110. In the lower left comer of the grid, the resource block 311 may span, as defined by a given communication protocol, a specified frequency range 306 and comprise multiple subcarriers or frequency sub-bands. The resource block 311 may include any suitable number of subcarriers (e.g., 12) that each correspond to a respective portion (e.g., 15 kHz) of the specified frequency range 306 (e.g., 180 kHz). The resource block 311 may also span, as defined by the given communication protocol, a specified time interval 308 or time slot (e.g. , lasting approximately one-half millisecond or seven orthogonal frequency-division multiplexing (OFDM) symbols). The time interval 308 includes subintervals that may each correspond to a symbol, such as an OFDM symbol. As shown in FIG. 3, each resource block 310 may include multiple resource elements 320 (REs) that correspond to, or are defined by, a subcarrier of the frequency range 306 and a subinterval (or symbol) of the time interval 308. Alternatively, a given resource element 320 may span more than one frequency subcarrier or symbol. Thus, a resource unit 304 may include at least one resource block 310, at least one resource element 320, and so forth.

[0029] In example implementations, multiple user equipment 110 (one of which is shown) are communicating with the base stations 120 (one of which is shown) through access provided by portions of the air interface resource 302. The base station manager 266 (shown in FIG. 2) may determine a respective data-rate, type of information, or amount of information (e.g., data or control information) to be communicated (e.g., transmitted) by the user equipment 110. The base station manager 266 then allocates one or more resource blocks 310 to each user equipment 110 based on the determined data rate or amount of information.

[0030] Additionally, or in the alternative to block-level resource grants, the base station manager 266 may allocate resource units at an element-level. Thus, the base station manager 266 may allocate one or more resource elements 320 or individual subcarriers to different user equipment 110. By so doing, one resource block 310 can be allocated to facilitate network access for multiple user equipment 110. Accordingly, the base station manager 266 may allocate, at various granularities, one or up to all subcarriers or resource elements 320 of a resource block 310 to one user equipment 110 or divided across multiple user equipment 110, thereby enabling higher network utilization or increased spectrum efficiency.

[0031] The base station manager 266 can therefore allocate air interface resource 302 by resource unit 304, resource block 310, frequency carrier, time interval, resource element 320, frequency subcarrier, time subinterval, symbol, spreading code, some combination thereof, and so forth. Based on respective allocations of resource units 304, the base station manager 266 can transmit respective messages to the multiple user equipment 110 indicating the respective allocation of resource units 304 to each user equipment 110. Each message may enable a respective user equipment 110 to queue the information or configure the LTE transceiver 206 and/or 5GNR transceiver 208 to communicate via the allocated resource units 304 of the air interface resource 302.

Inter-Radio Access Technology Channel Estimation

[0032] FIG. 4 illustrates data and control transactions between a user equipment 111, a first RAT base station 122, and a second RAT base station 123, which can implement various aspects of inter-radio access technology channel estimation. In aspects, a base station (e.g., the base station 123) can determine the quasi co-location (QCL) between an antenna port of a first RAT (e.g., the RAT of RAN 142, RATI) and an antenna port of a second RAT (e.g., the RAT of RAN 141, RAT2) and send QCL information to a user equipment (e.g., the UE 111) using the second RAT. The UE 111 can then use the QCL information and received signals from the base station 122 using the first RAT to improve the channel estimate for downlink signals from the base station 123 using the second RAT. In some implementations, the first RAT is 4G-LTE and the second RAT is 5G-NR. In some implementations, the RATI base station is a NR base station and the RAT2 base station is an E-UTRA base station. In some implementations the first RAT is 5GNR and the second RAT is 6G. In some implementations the RATI base station and the RAT2 base station share an antenna structure. In some implementations, the RAT2 base station provides a Pcell and the RATI base station provides an Scell or a PScell. In some implementations, the RAT2 base station provides a master mode (MN) and the RATI base station provides a secondary node (SN).

[0033] At 405, the RATI base station 122 sends a pilot signal (reference signal) configuration for an antenna port to the RAT2 base station 123. For example, the RATI base station 122 sends the configuration of its own pilot signals (e.g., Demodulation Reference Signals (DM-RS), Channel State Information Reference Signal (CSI-RS), Phase Tracking Reference Signal (PTRS), Tracking Reference Signal (PTRS), LTE Cell Specific Reference Signal (CRS), Primary Synchronization Signals (PSS), Secondary Synchronization Signals (SSS), Synchronization Signals (SS) transmitted on a Physical Broadcast Channel (PBCH), SS/PBCH, or the like) for the antenna port through a wired or wireless interface (e.g. , the Xn interface 105) to the RAT2 base station 123. In an alternative example, the RAT2 base station 123 can receive the pilot signals over the air from the RATI base station 122 and demodulate the pilot signals to determine the configuration of the pilot signals transmitted by the RATI base station 122. In a further example, the RATI base station and the RAT2 base station may be collocated and share hardware, for example shared baseband circuitry. For such collocated base stations, the RATI base station 122 and the RAT2 base station 123 can share the pilot signal configuration for an antenna port using inter-processor communication or any other suitable hardware interface between the components of the RATI base station 122 and the RAT2 base station 123.

[0034] At 410, the RAT2 base station 123 determines the CQL of the RAT2 downlink channel with respect to the RATI pilot signals. For example, because QCL depends on the location of antenna ports of the base stations, the RATI base station 122 and the RAT2 base station 123 share a common delay spread and/or Doppler spread when the RATI base station 122 and the RAT2 base station 123 share a common antenna. In another example, when the RATI base station

122 and the RAT2 base station 123 can communicate the phases used for an antenna port, the RAT2 base station 123 can determine if the RATI base station 122 and the RAT2 base station

123 share the same spatial properties (e.g., the same spatial reception parameter). The RAT2 base station 123 can specify the QCL in terms of one or more QCL parameters. The QCL parameters include a Doppler shift, a Doppler spread, an average delay, a delay spread, or a Spatial reception (Rx) parameter. For example, as described in 3GPP TS 38.214 V16.1.0 (2020-03) and illustrated in Table 1, the RAT2 base station 123 can group one or more QCL parameters into a QCL Type:

Table 1.

[0035] In some deployments, the RATI base station 122 and the RAT2 base station 123 are physically co-located and may share the same antenna(s) that results in a closer match in spread (e.g., delay spread and/or Doppler spread) due to having extremely similar channel conditions when signals for both the first RAT and the second RAT use the same frequency and have the same physical antenna port properties and location(s) at overlapping times. In other deployments, where the RATI base station 122 and the RAT2 base station 123 are not physically co-located or do not share the same antenna structure, the physical location-based channel conditions are less similar compared to when physically collocated and sharing the same antenna array, but QCL information may still be useful.

[0036] At 415, the RAT2 base station 123 sends the RATI pilot signal configuration and the QCL information, for the RAT2 channel with respect to the RATI pilot signals, to the UE 111. The QCL information specifies the quasi-collocation of aRAT2 channel (for example, a downlink control channel, a physical downlink control channel (PDCCH), a downlink data channel, a physical downlink shared channel (PDSCH), a downlink pilot channel, a Channel State Information Reference Signal (CSI-RS), a synchronization channel, Synchronization Signals (SS) transmitted on a Physical Broadcast Channel (PBCH), SS/PBCH) with respect to the RATI pilot signals. For example, the RAT2 base station 123 sends the RATI pilot signal configuration and the QCL information in one or more Radio Resource Control (RRC) messages or a Media Access Control (MAC) Control Element (CE) to the UE 111. In another example, the RAT2 base station 123 sends the QCL information as additional bits in a Transmission Configuration Indicator (TCI).

[0037] In aspects, the RAT2 base station 123 can include additional parameters in the QCL information sent to the UE 111 in order for the UE 111 to use the RATI pilot signals to improve channel estimation and/or time or frequency tracking. For example, the RAT2 base station 123 can include the cell-ID of the RATI base station 122 that is used to generate the RATI pilot sequence. In another example, the RAT2 base station 123 can include the power level of the RATI pilot signals in the event that the RATI base station 122 uses a different power level than channels used in RAT2. For example, the message at 405 can include the power level of the RATI pilot signals. Subsequently, the RAT2 base station 123 communicates at 415 the difference in power levels to the UE 111, for example, as a ratio of the RATI pilot signal power level received at 405 to the power level of a RAT2 channel. Other relative and absolute mechanisms can be used to communicate the power level of the RATI pilot signal transmission and the RAT2 data and control signal transmissions.

[0038] In a further aspect, the RAT2 base station 123 can signal a RAT2 precoding vector that is correlated with the RATI pilot signals. In one example, the beam used by the RAT2 channel could differ from a beam used to transmit the RATI pilot signals. When using different beams, the UE 111 can still use the RATI pilot signal channel delay spread and/or doppler spread to assist in estimating the RAT2 channel. When the RATI base station 122 and the RAT2 base station 123 share the same antennas, the underlying MIMO spatial channel from the RATI base station 122 to the UE 111 and from the RAT2 base station 123 to the UE 111 are the same.

[0039] In another aspect, the RAT2 base station 123 can indicate to the UE 111 a relative phase difference of the RATI pilot channel with respect to the RAT2 pilot channel, data channel, or control channel, such that the UE 111 can derive the channel estimation used for RAT2 signals from the RATI pilot signals . In one example, relative phase differences between the antenna ports of a first RAT pilot channel and antenna ports of a second RAT pilot channel or data channel can be indexed into an inter-RAT codebook with the RAT2 base station 123 and the UE 111 each having a copy of the inter-RAT codebook. The RAT2 base station 123 communicates the relative phase difference to the UE 111 by communicating the index value for the inter-RAT codebook to the UE 111 with the QCL information.

[0040] At 420, the RATI base station 122 transmits RATI pilot signals on the RATI pilot channel. At 425, the RAT2 base station 123 transmits data on a data channel or control information on a control channel. At 430, the UE 111 uses the RATI pilot signals and QCL, or the results of a channel estimate based on the RATI pilot signals and QCL, to estimate the channel for the RAT2 downlink data or control channel.

[0041] In a first aspect, as illustrated at 420 and 425, the RATI pilot signals and the RAT2 downlink data or control channel can be transmitted using orthogonal spectrum sharing by transmitting at different times (e.g., in different time slots). In another aspect, the transmission of the RAT2 downlink data or control channel at 425 can be superpositioned on the transmission of the RATI pilot signals at 420 (e.g., during overlapping time slots). For example, the RAT2 base station 123 can include an indication of the superpositioned transmission with the QCL information signaled in an RRC message from the RAT2 base station 123 to the UE 111. The RAT2 base station 123 can include the power level used for transmission of the RAT2 data or control channel that is superpositioned with the RATI reference signals. The power level of the RATI pilot signals can also be used, if it was received earlier (e.g., at 405), in a RATTRAT2 power ratio indication as an example. The RAT2 base station 123 can include an indication of the wireless resource elements where the superposition of the RAT2 data or control channel and RATI reference signal occurs. The UE 111 estimates RATI pilot signals based on the QCL information provided by RAT2 base station 123, and then UE 111 can use the superpositioning indication to subtract the estimated RATI pilot signals from the received RAT2 downlink data or control channels.

Example Methods

[0042] Example methods 500 and 600 are described with reference to FIGs. 5 and 6 in accordance with one or more aspects of inter-radio access technology channel estimation. FIG. 5 illustrates example method(s) 500 of inter-radio access technology channel estimation as generally related to coordinating channel estimation between a first RAT and a second RAT by the base station 123. At block 502, a second base station (e.g., the base station 123) receives, from a first base station (e.g., the base station 122), a pilot signal configuration for a first radio access technology. The pilot signal configuration can include one or more of Demodulation Reference Signals (DM-RS), Channel State Information Reference Signal (CSI-RS), Phase Tracking Reference Signal (PTRS), Tracking Reference Signal (PTRS), LTE Cell Specific Reference Signal (CRS), Primary Synchronization Signals (PSS), Secondary Synchronization Signals (SSS), Synchronization Signals (SS) transmitted on a Physical Broadcast Channel (PBCH), SS/PBCH, or the like. For example, the base station 123 receives an indication of the pilot signals and the resource elements used for the pilot signals from the base station 122 using the Xn interface 105. Additionally, the pilot signal configuration information can include antenna port information and/or pilot signal transmission power information.

[0043] At block 504, the second base station determines quasi co-location information of an antenna port for a second RAT based on the received pilot signal configuration for the first RAT. For example, the base station 123 determines QCL information of an antenna port for the second RAT with respect to an antenna port of the first RAT including one or more of: a Doppler shift, a Doppler spread, an average delay, a delay spread, or a spatial Rx parameter.

[0044] At block 506, the second base station transmits, using the second RAT, the QCL information to a user equipment (e.g., the UE 111), the transmitting directing the UE to use the QCL information to estimate a channel condition for the second RAT. For example, the base station 123 transmits, using the second RAT, the QCL information and the configuration of the RATI pilot signals to the UE 111 that enables the UE 111 to estimate a channel for the first RAT from the base station 122 and in turn use that channel estimate to estimate a channel for the second RAT from the base station 123. Alternatively, the UE 111 may use the channel estimate for the first RAT for reception of downlink signals of the second RAT without further estimating the channel for the second RAT.

[0045] At block 508, the second base station transmits a downlink channel to the UE using the second RAT, the downlink channel being decodable by the UE using the estimated channel condition for the second RAT calculated at block 506. For example, the base station transmits a downlink channel to the UE 111. The downlink channel may be a downlink control channel, a PDCCH, a downlink data channel, a PDSCH, a downlink pilot channel, a CSI-RS, a synchronization channel, or an SS/PBCH.

[0046] FIG. 6 illustrates example method(s) 600 of inter-radio access technology channel estimation as generally related to estimating a channel by a user equipment. At block 602, a user equipment (e.g., the UE 111) receives quasi co-location information from a second base station (e.g., the base station 123) for a second radio access technology based on a pilot signal configuration for a first RAT. For example, the UE 111 receives QCL information in an RRC message from the base station 123. The QCL information may include one or more of: a Doppler shift, a Doppler spread, an average delay, a delay spread, or a spatial Rx parameter. The QCL information may also include a cell-ID of a first base station (e.g., the base station 122) that transmits the pilot signals using the first RAT.

[0047] At block 604, the user equipment receives one or more pilot signals from a first base station (e.g. , the base station 122) using the first RAT. For example, the UE 111 uses a pilot signal configuration for RATI to receive pilot signals from the base station 122.

[0048] At block 606, the user equipment receives downlink signals from the second base station using the second RAT. For example, the UE 111 receives signals for a downlink channel from the base station 123 using RAT2. The downlink channel may be a downlink data channel, a downlink control channel, a downlink pilot channel, or a synchronization channel.

[0049] At block 608, the user equipment estimates a channel between the first base station and the UE based on the received one or more pilot signals and the QCL information. For example, using the pilot signal configuration for RATI and a cell-ID for the base station 122 that was received from the base station 123, the UE 111 estimates the channel for the downlink from the base station 122 to the UE 111. The UE111 can use the channel estimate for the downlink from the base station 122 using RATI to estimate channel conditions for the reception of downlink signals from the second base station 123 using RAT2.

[0050] Optionally or additionally at block 610, the user equipment estimates a channel between the second base station and the UE based on the estimated channel conditions between the first base station and the UE. For example, the UE 111 uses the result of the channel estimate for the channel between the base station 122 and the UE 111 for the RATI to estimate the channel between the base station 123 and the UE 111 for RAT2. The UE may receive parameters indicating similarities in channel conditions (e.g., via QCL information) if the first base station and the second base station share an antenna array, use similar antenna beams, or use the same antenna ports, when the RATI pilot signal and the RAT2 control or data signal share a frequency band or bandwidth part, and/or when a RATI pilot signal and a RAT2 downlink signal occur at overlapping times. The UE can apply these parameters when the time, frequency, and/or spatial characteristics of a wireless communication channel from a first base station to the UE is expected to coincide with the time, frequency, and/or spatial characteristics of another wireless communication channel from a second base station to the UE. This allows a UE to apply the estimate of channel conditions for one BS to the decoding process of signals for a different BS.

[0051] The order in which the method blocks of methods 500 and 600 are described are not intended to be construed as a limitation, and any number of the described method blocks can be skipped or combined in any order to implement a method or an alternate method. Generally, any of the components, modules, methods, and operations described herein can be implemented using software, firmware, hardware (e.g., fixed logic circuitry), manual processing, or any combination thereof. Some operations of the example methods may be described in the general context of executable instructions stored on computer-readable storage memory that is local and/or remote to a computer processing system, and implementations can include software applications, programs, functions, and the like. Alternatively or in addition, any of the functionality described herein can be performed, at least in part, by one or more hardware logic components, such as, and without limitation, Field-programmable Gate Arrays (FPGAs), Application-specific Integrated Circuits (ASICs), Application-specific Standard Products (ASSPs), System-on-a-chip systems (SoCs), Complex Programmable Logic Devices (CPLDs), and the like.

[0052] In the following some examples are described:

Example 1 : A method for coordinating channel estimation, the method comprising a second base station using a second radio access technology, RAT: receiving, from a first base station, a pilot signal configuration for a first antenna port for a first RAT; determining quasi co-location, QCL, information for a second antenna port for the second RAT based on the received pilot signal configuration for the first RAT; transmitting the QCL information to a user equipment, UE, the transmitting directing the UE to use the QCL information to estimate a channel condition for the second RAT; and transmitting downlink signals on a downlink channel to the UE using the second RAT, the downlink signals being decodable by the UE using the estimated channel condition for the second RAT. Example 2: The method of example 1, wherein the QCL information includes one or more of: a Doppler shift; a Doppler spread; an average delay; a delay spread; or a spatial reception parameter.

Example 3: The method of example 1 or example 2, wherein the receiving a pilot signal configuration for a first antenna port for a first RAT.

Example 4: The method of any one of the preceding examples, wherein the transmitting the QCL information to a UE includes: transmitting an index for an inter-RAT codebook, the index being usable by the UE to retrieve a relative phase difference between the first RAT pilot signals and the second RAT downlink channel.

Example 5: The method of any of the preceding examples, wherein the QCL information includes a cell-ID of the first base station, the cell-ID of the first base station being usable by the UE to decode the first RAT pilot signals.

Example 6: The method of any of the preceding examples, wherein transmitting the QCL information comprises the second base station: transmitting the QCL information to the UE in a Radio Resource Control, RRC, message; transmitting the QCL information to the UE in a Media Access Control, MAC, Control Element, CE; or transmitting the QCL information to the UE in a Transmission Configuration Indicator,

TCI.

Example 7: The method of any of the preceding examples, the transmitting the downlink signals on the downlink channel comprising the second base station: transmitting downlink signals for a downlink data channel; transmitting downlink signals for a downlink control channel; transmitting downlink signals for a downlink pilot channel; or transmitting downlink signals for a synchronization channel. Example 8: The method of any of the preceding examples, wherein the transmitting the downlink channel comprises the second base station: superpositioning the transmitting of the downlink channel using the second RAT on pilot signals transmitted by the first base station using the first RAT.

Example 9: The method of any of the preceding examples, wherein the receiving the pilot signal configuration comprises the second base station: receiving the pilot signal configuration from the first base station using an Xn interface.

Example 10: The method of any one of examples 1 to 8, wherein the receiving the pilot signal configuration comprises the second base station: receiving the pilot signals over-the-air from the first base station; decoding the received pilot signals; and determining the pilot signal configuration from the decoded pilot signals.

Example 11 : The method of any of the preceding examples, wherein the transmitting the QCL information to the UE comprises: transmitting the QCL information to the UE using the second RAT.

Example 12. The method of any of the preceding examples, wherein the pilot signal configuration for the first antenna port for the first RAT includes one or more of:

Demodulation Reference Signals, DM-RS; a Channel State Information Reference Signal, CSI-RS; a Phase Tracking Reference Signal, PTRS; a Tracking Reference Signal, PTRS; an LTE Cell Specific Reference Signal, CRS;

Primary Synchronization Signals, PSS;

Secondary Synchronization Signals, SSS.

Example 13: The method of any of the preceding examples, wherein the first RAT is a 3rd Generation Partnership Project Long-Term Evolution, 3GPP LTE, RAT, and wherein the second RAT is a Fifth Generation New Radio, 5GNR, RAT.

Example 14: A first base station comprising: a wireless transceiver; an inter-base station interface; a processor; and memory comprising instructions for a base station manager application that are executable by the processor to configure the base station to perform the method of any of the preceding examples.

Example 15: The base station of example 14 comprising: an antenna array shared by a second base station.

Example 16. The base station of example 14 comprising: baseband circuitry shared with the second base station; and wherein the first base station shares the pilot signal configuration for the antenna port with the second base station using a hardware interface.

Example 17: A method of estimating a channel by a user equipment, UE, the method comprising the UE: receiving quasi co-location, QCL, information from a second base station for a second radio access technology, RAT, based on a pilot signal configuration for a first RAT; receiving one or more pilot signals from a first base station using the first RAT according to the pilot signal configuration; receiving downlink signals from the second base station using the second RAT; estimating a channel between the second base station and the UE based on the received one or more pilot signals and the QCL information; and based on the estimating the channel between the second base station and the UE, decoding the received downlink signals from the second base station.

Example 18: The method of example 17, wherein the estimating a channel between the second base station and the UE produces a second channel estimate and comprises the UE: estimating a first channel between the first base station and the UE based on the received one or more pilot signals and the pilot signal configuration for the first RAT; and calculating the second channel estimate based on the first channel estimate and the QCL information, wherein the decoding the received downlink signals from the second base station is based on the second channel estimate. Example 19: The method of example 17 or example 18, wherein the QCL information includes one or more of: a Doppler shift; a Doppler spread; an average delay; a delay spread; or a spatial reception parameter.

Example 20: The method of any one of examples 17 to 19, wherein the QCL information includes: an indication of a transmit power level of the first RAT pilot signals; and wherein the estimating the channel between the second base station and the UE comprises the UE: estimating the channel between the second base station and the UE using the indication of the transmit power level of the first RAT pilot signals.

Example 21: The method of any one of examples 17 to 20, wherein the downlink signals from the second base station using the second RAT are superpositioned on the one or more pilot signals from a first base station using the first RAT; the method further comprising the user equipment: using the QCL information to subtract an estimation of the one or more pilot signals from the first base station from the superpositioned downlink signals of the second RAT.

Example 22: The method of any one of examples 17 to 21, the downlink signals comprising signals of: a downlink data channel; a downlink control channel; a downlink pilot channel; or a synchronization channel.

Example 23: The method of any one of examples 17 to 22, wherein the QCL information includes an index for an inter-RAT codebook; the method further comprising the UE: using the index to retrieve a relative phase difference between the first RAT pilot signals and the second RAT downlink channel from the inter-RAT codebook; and using the retrieved relative phase difference to estimate the channel between the second base station and the UE. Example 24: The method of any of examples 17 to 23, wherein the QCL information includes a cell-ID of the first base station, the receiving one or more pilot signals from the first base station using the first RAT comprising the UE: using the cell-ID to decode the one or more pilot signals from the first base station.

Example 25: The method of any of examples 17 to 24, wherein receiving the QCL information comprises the UE: receiving the QCL information from the second base station in a Radio Resource Control, RRC, message; receiving the QCL information from the second base station in a Media Access Control, MAC, Control Element, CE; or receiving the QCL information from the second base station in a Transmission Configuration Indicator, TCI.

Example 26: The method of any of examples 17 to 25, wherein the receiving the QCL information from the second base station comprises the UE: receiving the QCL information from the second base station using the second RAT.

Example 27: The method of any one of examples 17 to 26, wherein the first RAT is a 3rd Generation Partnership Project Long-Term Evolution, 3GPP LTE, RAT, and wherein the second RAT is a Fifth Generation New Radio, 5GNR, RAT.

Example 28: The method of any one of examples 17 to 27, wherein pilot signal configuration for a first RAT includes antenna port information.

Example 29: A user equipment comprising: a radio frequency transceiver; a processor; and memory comprising instructions for a channel estimator application that is executable to configure the user equipment to perform any one of the methods of examples 17 to 28.

Example 30: A computer-readable medium comprising instructions that, when executed by a processor, cause an apparatus comprising the processor to perform any of the methods of examples 1 to 13 or 17 to 28. [0053] Although aspects of inter-radio access technology channel estimation have been described in language specific to features and/or methods, the subject of the appended claims is not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed as example implementations of inter-radio access technology channel estimation, and other equivalent features and methods are intended to be within the scope of the appended claims. Further, various different aspects are described, and it is to be appreciated that each described aspect can be implemented independently or in connection with one or more other described aspects.

Claims

1. A method for coordinating channel estimation, the method comprising a second base station using a second radio access technology, RAT: receiving, from a first base station, a pilot signal configuration for a first antenna port for a first RAT; determining quasi co-location, QCL, information for a second antenna port for the second RAT based on the received pilot signal configuration for the first RAT; transmitting the QCL information to a user equipment, UE, the transmitting directing the UE to use the QCL information to estimate a channel condition for the second RAT; and transmitting downlink signals on a downlink channel to the UE using the second RAT, the downlink signals being decodable by the UE using the estimated channel condition for the second RAT.

2. The method of claim 1, wherein the QCL information includes one or more of: a Doppler shift; a Doppler spread; an average delay; a delay spread; or a spatial reception parameter.

3. The method of claim 1 or claim 2, wherein the receiving a pilot signal configuration for a first antenna port for a first RAT includes: receiving an indication of a transmit power level of first RAT pilot signals.

4. The method of any one of the preceding claims, wherein the transmitting the QCL information to a UE includes: transmitting an index for an inter-RAT codebook, the index being usable by the UE to retrieve a relative phase difference between the first RAT pilot signals and the second RAT downlink channel.

5. The method of any of the preceding claims, wherein the QCL information includes a cell-ID of the first base station, the cell-ID of the first base station being usable by the UE to decode the first RAT pilot signals.

6. The method of any of the preceding claims, wherein transmitting the QCL information comprises the second base station: transmitting the QCL information to the UE in a Radio Resource Control, RRC, message; transmitting the QCL information to the UE in a Media Access Control, MAC, Control Element, CE; or transmitting the QCL information to the UE in a Transmission Configuration Indicator,

TCI.

7. The method of any of the preceding claims, the transmitting the downlink signals on the downlink channel comprising the second base station: transmitting downlink signals for a downlink data channel; transmitting downlink signals for a downlink control channel; transmitting downlink signals for a downlink pilot channel; or transmitting downlink signals for a synchronization channel.

8. The method of any of the preceding claims, wherein the transmitting the downlink channel comprises the second base station: superpositioning the transmitting of the downlink channel using the second RAT on pilot signals transmitted by the first base station using the first RAT.

9. The method of any of the preceding claims, wherein the receiving the pilot signal configuration comprises the second base station: receiving the pilot signal configuration from the first base station using an Xn interface.

10. The method of any one of claims 1 to 8, wherein the receiving the pilot signal configuration comprises the second base station: receiving the pilot signals over-the-air from the first base station; decoding the received pilot signals; and determining the pilot signal configuration from the decoded pilot signals.

11. The method of any of the preceding claims, wherein the transmitting the QCL information to the UE comprises: transmitting the QCL information to the UE using the second RAT.

12. The method of any of the preceding claims, wherein the pilot signal configuration for the first antenna port for the first RAT includes one or more of:

Primary Synchronization Signals, PSS;

Secondary Synchronization Signals, SSS.

13. A first base station comprising: a wireless transceiver; an inter-base station interface; a processor; and memory comprising instructions for a base station manager application that are executable by the processor to configure the base station to perform any of the preceding methods.

14. The base station of claim 13 comprising: an antenna array shared by a second base station.

15. The base station of claim 14 comprising: baseband circuitry shared with the second base station; and wherein the first base station shares the pilot signal configuration for the antenna port with the second base station using a hardware interface.