HK1188052B - Method and apparatus for rate matching with muting - Google Patents

Description

Method and apparatus for rate matching with muting

Claiming priority based on 35U.S.C. § 119

This patent application claims priority from U.S. provisional application No.61/409,486 entitled "interactive nopdschresourcemappingcsi-rsinllte-a" filed on day 2, 2010 and U.S. provisional application No.61/411,421 entitled "interactive nopdschresourcemappingcsi-RSINLTE-a" filed on day 8, 11, 2010, both of which have been assigned to the assignee of the present application and are hereby expressly incorporated herein by reference.

Technical Field

The present disclosure relates generally to communication systems, and more specifically to techniques for blind decoding an interfering cell Physical Downlink Control Channel (PDCCH) to obtain interfering cell Physical Downlink Shared Channel (PDSCH) transmission information.

Background

Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, and broadcasting. Typical wireless communication systems may employ multiple-access techniques capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth, transmit power). Examples of such multiple-access techniques include Code Division Multiple Access (CDMA) systems, Time Division Multiple Access (TDMA) systems, Frequency Division Multiple Access (FDMA) systems, Orthogonal Frequency Division Multiple Access (OFDMA) systems, single carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems.

These multiple access techniques have been employed in various telecommunications standards to provide a common protocol that enables different wireless devices to communicate on a city, country, region, and even global level. One example of an emerging telecommunications standard is Long Term Evolution (LTE). LTE is an enhanced set of Universal Mobile Telecommunications System (UMTS) mobile standards promulgated by the third generation partnership project (3 GPP). It is designed to: better support mobile broadband internet access by improving spectral efficiency, reducing costs, improving services, using new spectrum, and better integrating with other open standards using SC-FDMA on the Uplink (UL) and multiple-input multiple-output (MIMO) antenna technology using OFDMA on the Downlink (DL). However, as the demand for mobile broadband access continues to increase, further improvements in LTE technology are needed. Preferably, these improvements should be applicable to other multiple access techniques and telecommunications standards using these techniques.

Disclosure of Invention

Certain aspects of the present disclosure provide a method for wireless communication. The method generally comprises: determining, by a base station, a period of ambiguity in which the base station lacks a determination regarding a user equipment (UE)'s ability to support configuration of resources reserved for a special purpose; and excluding the resources reserved for the special purpose when performing rate matching when transmitting a Physical Downlink Shared Channel (PDSCH) to the UE in a resource block during the ambiguity period.

Certain aspects of the present disclosure provide a method for wireless communication. The method generally comprises: determining, by a User Equipment (UE), an ambiguity period in which the base station lacks a determination regarding a UE's ability to support a configuration of resources reserved for a special purpose in a subframe; and processing the subframe under the following assumptions: the base station has excluded the resources reserved for special purposes when performing rate matching when transmitting a Physical Downlink Shared Channel (PDSCH) to the UE in the subframe during the ambiguity period.

Certain aspects of the present disclosure provide an apparatus for wireless communication. The apparatus generally comprises: means for determining, by a base station, an ambiguity period in which the base station lacks a determination regarding a user equipment (UE)'s ability to support a configuration of resources reserved for a special purpose in a subframe; and means for excluding the resources reserved for special purposes when performing rate matching when transmitting a Physical Downlink Shared Channel (PDSCH) to the UE in the subframe during the ambiguity period.

Certain aspects of the present disclosure provide an apparatus for wireless communication. The apparatus generally comprises: means for determining, by a User Equipment (UE), a period of ambiguity in which a base station lacks a determination regarding the UE's ability to support a configuration of resources reserved for a special purpose in a subframe; and means for processing the subframe under the following assumptions: the base station has excluded the resources reserved for special purposes when performing rate matching when transmitting a Physical Downlink Shared Channel (PDSCH) to the UE in the subframe during the ambiguity period.

Certain aspects of the present disclosure provide an apparatus for wireless communication. The apparatus generally comprises: at least one processor configured to: determining, by a base station, an ambiguity period in which the base station lacks a determination regarding a user equipment (UE)'s ability to support a configuration of resources reserved for a special purpose in a subframe, and excluding resources reserved for a special purpose when performing rate matching when transmitting a Physical Downlink Shared Channel (PDSCH) to the UE in the subframe during the ambiguity period; and a memory coupled with the at least one processor.

Certain aspects of the present disclosure provide an apparatus for wireless communication. The apparatus generally comprises: at least one processor configured to: determining, by a User Equipment (UE), an ambiguity period in which the base station lacks a determination regarding the UE's ability to support a configuration of resources reserved for a special purpose in a subframe, and processing the subframe under the following assumption: when transmitting a Physical Downlink Shared Channel (PDSCH) to the UE in the subframe during the ambiguity period, the base station having excluded the resources reserved for the special purpose when performing rate matching; and a memory coupled with the at least one processor.

Certain aspects of the present disclosure provide a computer program product comprising a computer-readable medium having instructions stored thereon. The instructions are generally executable by one or more processors for: determining, by a base station, an ambiguity period in which the base station lacks a determination regarding a user equipment (UE)'s ability to support a configuration of resources reserved for a special purpose in a subframe; and excluding the resources reserved for the special purpose when performing rate matching when transmitting a Physical Downlink Shared Channel (PDSCH) to the UE in the subframe during the ambiguity period.

Certain aspects of the present disclosure provide a computer program product comprising a computer-readable medium having instructions stored thereon. The instructions are generally executable by one or more processors for: determining, by a User Equipment (UE), an ambiguity period in which the base station lacks a determination regarding a UE's ability to support a configuration of resources reserved for a special purpose in a subframe; and processing the subframe under the following assumptions: the base station has excluded the resources reserved for special purposes when performing rate matching when transmitting a Physical Downlink Shared Channel (PDSCH) to the UE in the subframe during the ambiguity period.

Drawings

Fig. 1 is a schematic diagram illustrating an example of a network architecture.

Fig. 2 is a schematic diagram illustrating an example of an access network.

Fig. 3 is a diagram showing an example of a DL frame structure in LTE.

Fig. 4 is a diagram showing an example of a UL frame structure in LTE.

Fig. 5 is a schematic diagram illustrating an example of a radio protocol architecture for the user plane and the control plane.

Fig. 6 is a schematic diagram illustrating an example of an evolved node B and user equipment in an access network.

Fig. 7 illustrates an example of resource mapping in accordance with certain aspects of the present disclosure.

Fig. 8 illustrates an example resource map with CSI-RS and muting in accordance with certain aspects of the present disclosure.

Fig. 9 illustrates example operations in accordance with certain aspects of the present disclosure.

Fig. 10 is a schematic diagram illustrating an example of a data flow in accordance with certain aspects of the present disclosure.

Fig. 11 is a schematic diagram illustrating an example of a hardware implementation of an apparatus using a processing system in accordance with certain aspects of the present disclosure.

Detailed Description

The detailed description set forth below in connection with the appended drawings is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein may be implemented. The detailed description includes specific details for the purpose of providing a thorough understanding of the various concepts. It will be apparent, however, to one skilled in the art that the concepts may be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form in order to avoid obscuring such concepts.

Several aspects of a telecommunications system will now be presented with reference to various apparatus and methods. These apparatus and methods are described in the following detailed description and illustrated in the accompanying drawings by various blocks, modules, components, circuits, steps, processes, algorithms, etc. (collectively referred to as "elements"). These elements may be implemented using electronic hardware, computer software, or any combination thereof. Whether such elements are implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system.

For example, an element or any portion of an element or any combination of elements may be implemented with a "processing system" that includes one or more processors. Examples of processors include microprocessors, microcontrollers, Digital Signal Processors (DSPs), Field Programmable Gate Arrays (FPGAs), Programmable Logic Devices (PLDs), state machines, gated logic, discrete hardware circuits, and other suitable hardware configured to perform the various functions described throughout this disclosure. One or more processors in the processing system may execute software. Software shall be construed broadly to mean instructions, instruction sets, code segments, program code, programs, subroutines, software modules, applications, software packages, routines, subroutines, objects, executables, threads of execution, procedures, functions, etc., whether referred to as software, firmware, middleware, microcode, hardware description language, or by other names.

Accordingly, in one or more exemplary embodiments, the functions described may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or encoded on a computer-readable medium as one or more instructions or code. Computer readable media includes computer storage media. A storage media may be any available media that can be accessed by a computer. By way of example, and not limitation, such computer-readable media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to carry or store desired program code in the form of instructions or data structures and that can be accessed by a computer. Disk and disc, as used herein, includes Compact Disc (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 should also be included within the scope of computer-readable media.

Fig. 1 is a schematic diagram illustrating an LTE network architecture 100. The LTE network architecture 100 may be referred to as an Evolved Packet System (EPS) 100. The EPS100 may include one or more User Equipment (UE) 102, an evolved UMTS terrestrial radio access network (E-UTRAN) 104, an Evolved Packet Core (EPC) 110, a Home Subscriber Server (HSS) 120, and operator IP services 122. The EPS can interconnect with other access networks, although those entities/interfaces are not shown for simplicity. As shown, the EPS provides packet switched services, however, those skilled in the art will readily appreciate that the various concepts presented throughout this disclosure may be extended to networks providing circuit switched services.

The E-UTRAN includes evolved node Bs (eNBs) 106 and other eNBs 108. The eNB106 provides user plane and control plane protocol terminations toward the UE 102. eNB106 may be connected to other enbs 108 via an X2 interface (e.g., a backhaul). The eNB106 may also be referred to as a base station, a base station transceiver, a radio base station, a radio transceiver, a transceiver function, a Basic Service Set (BSS), an Extended Service Set (ESS), or some other suitable terminology. eNB106 provides an access point for UE102 to EPC 110. Examples of UEs 102 include cellular phones, smart phones, Session Initiation Protocol (SIP) phones, laptops, Personal Digital Assistants (PDAs), satellite radios, global positioning systems, multimedia devices, video devices, digital audio players (e.g., MP3 players), cameras, game consoles, or any other similar functioning devices. UE102 may also be referred to by those skilled in the art as a mobile station, a subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a mobile device, a wireless communications 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.

eNB106 connects to EPC110 through the S1 interface. EPC110 includes Mobility Management Entity (MME) 112, other MMEs 114, serving gateway 116, and Packet Data Network (PDN) gateway 118. MME112 is a control node that handles signaling between UE102 and EPC 110. Generally, the MME112 provides bearer and connection management. All user IP packets are transmitted through the serving gateway 116, which serving gateway 116 itself connects to the PDN gateway 118. The PDN gateway 118 provides ue ip address allocation as well as other functions. The PDN gateway 118 connects to the operator's IP service 122. The operator's IP services 122 may include the internet, intranets, IP Multimedia Subsystem (IMS), and PS streaming services (PSs).

Fig. 2 is a schematic diagram illustrating an example of an access network 200 in an LTE network architecture. In this example, the access network 200 is divided into a plurality of cellular regions (cells) 202. One or more lower power class enbs 208 may have cellular regions 210 that overlap with one or more of cells 202. The lower power class eNB208 may be referred to as a Remote Radio Head (RRH). The lower power class eNB208 may be a femto cell (e.g., a home eNB (henb)), pico cell, or micro cell. Each macro eNB204 is assigned to a respective cell 202, and each macro eNB204 is configured to provide an access point to EPC110 for all UEs 206 in cell 202. There is no centralized controller in this example of the access network 200, but a centralized controller may be used in alternative configurations. The eNB204 is responsible for all radio related functions including radio bearer control, admission control, mobility management, scheduling, security, and connectivity to the serving gateway 116.

The modulation and multiple access schemes used by the access network 200 may vary depending on the particular telecommunications standard deployed. In LTE applications, OFDM is used on the DL and SC-FDMA is used on the UL to support both Frequency Division Duplex (FDD) and Time Division Duplex (TDD). As will be readily apparent to those skilled in the art from the following detailed description, the various concepts presented herein are well suited for LTE applications. However, these concepts can be readily extended to other telecommunications standards using other modulation and multiple access techniques. For example, these concepts may be extended to evolution data optimized (EV-DO) or ultra-mobile broadband (UWB). EV-DO and UWB are air interface standards promulgated by the third generation partnership project 2 (3 GPP 2) as part of the CDMA2000 family of standards and use CDMA to provide broadband internet access to mobile stations. These concepts may also be extended to Universal Terrestrial Radio Access (UTRA) using wideband CDMA (W-CDMA) and other variants of CDMA, such as TD-SCDMA, global system for mobile communications (GSM) using TDMA, and evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE802.11 (Wi-Fi), IEEE802.16 (WiMAX), IEEE802.20, and flash OFDM using OFDMA. UTRA, E-UTRA, UMTS, LTE, and GSM are described in documents from the 3GPP organization. CDMA2000 and UMB are described in documents from the 3GPP2 organization. The actual wireless communication standard and multiple access technique used will depend on the particular application and the overall design constraints imposed on the system.

The eNB204 may have multiple antennas supporting MIMO technology. The use of MIMO technology enables eNB204 to utilize the spatial domain to support spatial multiplexing, beamforming, and transmit diversity. Spatial multiplexing may be used to transmit different data streams simultaneously on the same frequency. The data stream may be sent to a single UE206 to increase the data rate or to multiple UEs 206 to increase the overall system capacity. This is achieved by spatially precoding each data stream (i.e., applying adjustments to amplitude and phase) and then transmitting each spatially precoded stream over multiple transmit antennas on the DL. The spatially precoded data streams arrive at UEs 206 with different spatial signatures, which enable each of the UEs 206 to recover one or more data streams destined for that UE 206. On the UL, each UE206 transmits a spatially precoded data stream, which enables the eNB204 to identify the source of each spatially precoded data stream.

Spatial multiplexing is typically used when channel conditions are good. Beamforming may be used to concentrate the transmission energy in one or more directions when the channel conditions are poor. This may be achieved by spatially precoding data transmitted over multiple antennas. To obtain good coverage at the cell edge, single stream beamforming transmission may be used in combination with transmit diversity.

In the detailed description that follows, various aspects of the access network will be described with reference to a MIMO system supporting OFDM on the DL. OFDM is a spread spectrum technique that modulates data over multiple carriers within an OFDM symbol. The subcarriers are spaced apart at precise frequencies. This spacing provides "orthogonality" that enables the receiver to recover the data from the subcarriers. In the time domain, a guard interval (e.g., cyclic prefix) may be added to each OFDM symbol to combat OFDM inter-symbol interference. The UL may use SC-FDMA in the form of DFT-spread OFDM signals to compensate for high peak-to-average power ratio (PAPR).

Fig. 3 is a diagram 300 illustrating an example of a DL frame structure in LTE. One frame (10 ms) may be divided into 10 equally sized subframes. Each subframe may include two consecutive slots. One resource grid may be used to represent two slots, each slot comprising a resource block. The resource grid is divided into a plurality of resource elements. In LTE, one resource block contains 12 consecutive subcarriers in the frequency domain, and, for a normal cyclic prefix in each OFDM symbol, one resource block contains 7 consecutive OFDM symbols in the time domain or 84 resource elements. For an extended cyclic prefix, one resource block contains 6 consecutive OFDM symbols in the time domain and has 72 resource elements. Some of the resource elements (as indicated as R302, 304) include DL reference signals (DL-RS). The DL-RS includes cell-specific RS (crs) (sometimes also referred to as common RS) 302 and UE-specific RS (UE-RS) 304. The UE-RS304 is transmitted only on the resource blocks on which the corresponding Physical DL Shared Channel (PDSCH) is mapped. The number of bits carried by each resource element depends on the modulation scheme. Thus, the more resource blocks the UE receives and the higher the modulation scheme, the higher the data rate of the UE.

Fig. 4 is a diagram 400 illustrating an example of a UL frame structure in LTE. The available resource blocks of the UL may be divided into a data portion and a control portion. The control portion may be formed at both edges of the system bandwidth and may have a configurable size. The resource blocks in the control portion may be allocated to the UE for transmission of control information. The data portion may include all resource blocks not included in the control portion. The UL frame structure is such that the data portion includes contiguous subcarriers, which may allow all of the contiguous subcarriers in the data portion to be allocated to a single UE.

The resource blocks 410a, 410b in the control portion may be allocated to the UE to transmit control information to the eNB. Resource blocks 420a, 420b in the data portion may also be allocated to the UE to transmit data to the eNB. The UE may send control information in a Physical UL Control Channel (PUCCH) on resource blocks in the allocated control portion. The UE may transmit only data or both data and control information in a Physical UL Shared Channel (PUSCH) on resource blocks in the allocated data portion. The UL transmission may span both slots of a subframe and may hop between frequencies.

A set of resource blocks may be used to perform initial system access and to obtain UL synchronization in a Physical Random Access Channel (PRACH) 430. The PRACH430 carries a random sequence and cannot carry any UL data/signaling. Each random access preamble occupies a bandwidth corresponding to six consecutive resource blocks. The starting frequency is specified by the network. That is, the transmission of the random access preamble is restricted to certain time and frequency resources. There is no frequency hopping for PRACH. The PRACH attempt is made in a single subframe (1 ms) or in a sequence of several consecutive subframes, and the UE can only make one PRACH attempt per frame (10 ms).

Fig. 5 is a diagram 500 illustrating an example of a radio protocol architecture for the user plane and the control plane in LTE. The radio protocol architecture for the UE and eNB is represented in three layers: layer 1, layer 2 and layer 3. Layer 1 (L1 layer) is the lowest layer and implements various physical layer signal processing functions. The L1 layer will be referred to herein as the physical layer 506. Layer 2 (L2 layer) 508 is above the physical layer 506 and is responsible for the link between the UE and the eNB over the physical layer 506.

In the user plane, the L2 layer 508 includes a Medium Access Control (MAC) sublayer 510, a Radio Link Control (RLC) sublayer 512, and a Packet Data Convergence Protocol (PDCP) 514 sublayer, terminating at the eNB on the network side. Although not shown, the UE may have several upper layers above the L2 layer 508, including a network layer (e.g., IP layer) that terminates at the PDN gateway 118 on the network side and an application layer that terminates at the other end of the connection (e.g., far end UE, server, etc.).

The PDCP sublayer 514 provides multiplexing between different radio bearers and logical channels. The PDCP sublayer 514 also provides header compression for upper layer data packets to reduce radio transmission overhead, security by ciphering the data packets, and handover support for UEs between enbs. The RLC sublayer 512 provides segmentation and reassembly of upper layer data packets, retransmission of lost data packets, and reordering of data packets to compensate for out-of-order reception due to hybrid automatic repeat request (HARQ). The MAC sublayer 510 provides multiplexing between logical channels and transport channels. The MAC sublayer 510 is also responsible for allocating various radio resources (e.g., resource blocks) in one cell among the UEs. The MAC sublayer 510 is also responsible for HARQ operations.

In the control plane, the radio protocol architecture for the UE and eNB is substantially the same for the physical layer 506 and the L2 layer 508, except that there is no header compression for the control plane. The control plane also includes a Radio Resource Control (RRC) sublayer 516 in layer 3 (layer L3). The RRC sublayer 516 is responsible for acquiring radio resources (e.g., radio bearers) and for configuring lower layers using RRC signaling between the eNB and the UE.

Fig. 6 is a block diagram of an eNB610 in an access network in communication with a UE 650. In the DL, upper layer packets from the core network are provided to a controller/processor 675. The controller/processor 675 implements the functionality of the L2 layer. In the DL, the controller/processor 675 provides header compression, ciphering, packet segmentation and reordering, multiplexing between logical and transport channels, and radio resource allocation to the UE650 based on various priority metrics. The controller/processor 675 is also responsible for HARQ operations, retransmission of lost packets, and signaling to the UE 650.

TX processor 616 performs various signal processing functions for the L1 layer (i.e., the physical layer). The signal processing functions include coding and interleaving to facilitate Forward Error Correction (FEC) at the UE650, and mapping to signal constellations based on various modulation schemes (e.g., binary phase-shift keying (BPSK), quadrature phase-shift keying (QPSK), M-phase-shift keying (M-PSK), M-quadrature amplitude modulation (M-QAM)). The coded and modulated symbols are then split into parallel streams. Each stream is then mapped to OFDM subcarriers, multiplexed with reference signals (e.g., pilots) in the time and/or frequency domain, and then combined together using an Inverse Fast Fourier Transform (IFFT) to produce a physical channel carrying a time domain OFDM symbol stream. The OFDM streams are spatially precoded to produce a plurality of spatial streams. The channel estimates from channel estimator 674 may be used to determine coding and modulation schemes and for spatial processing. The channel estimates may be obtained from the reference signals and/or channel condition feedback sent by the UE 650. Each spatial stream is then provided to a different antenna 620 via a respective transmitter 618 TX. Each transmitter 618TX modulates an RF carrier with a respective spatial stream for transmission.

At the UE650, each receiver 654RX receives a signal through its respective antenna 652. Each receiver 654RX recovers information modulated onto an RF carrier and provides the information to a Receiver (RX) processor 656. The RX processor 656 performs various signal processing functions at the L1 layer. The RX processor 656 performs spatial processing on the information to recover any spatial streams destined for the UE 650. If multiple spatial streams are destined for the UE650, the RX processor 656 can combine them into a single OFDM symbol stream. The RX processor 656 then transforms the OFDM symbol stream from the time-domain to the frequency domain using a Fast Fourier Transform (FFT). The frequency domain signal comprises a separate OFDM symbol stream for each subcarrier of the OFDM signal. The symbols on each subcarrier, as well as the reference signal, are recovered and demodulated by determining the most likely signal constellation points transmitted by the eNB 610. These soft decisions may be based on channel estimates computed by the channel estimator 658. The soft decisions are then decoded and deinterleaved to recover the data and control signals that were originally transmitted by the eNB610 on the physical channel. The data and control signals are then provided to the controller/processor 659.

The controller/processor 659 implements the L2 layer. The controller/processor can be associated with a memory 660 that stores program codes and data. The memory 660 may be referred to as a computer-readable medium. In the UL, the controller/processor 659 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer packets from the core network. The upper layer packets are then provided to a data sink 662, which represents all protocol layers above the L2 layer. Various control signals may also be provided to a data sink 662 for processing by L3. The controller/processor 659 is also responsible for error detection using Acknowledgement (ACK) and/or Negative Acknowledgement (NACK) protocols to support HARQ operations.

In the UL, a data source 667 is used to provide upper layer packets to the controller/processor 659. The data source 667 represents all protocol layers above the L2 layer. Similar to the functionality described in connection with the DL transmission performed by the eNB610, the controller/processor 659 implements the L2 layer for the user plane and the control plane by providing header compression, ciphering, packet segmentation and reordering, and multiplexing between logical and transport channels based on radio resource allocation by the eNB 610. The controller/processor 659 is also responsible for HARQ operations, retransmission of lost packets, and signaling to the eNB 610.

The channel estimates obtained by a channel estimator 658 from a reference signal or feedback transmitted by the eNB610 may be used by the TX processor 668 to select the appropriate coding and modulation schemes and to facilitate spatial processing. The spatial streams generated by the TX processor 668 are provided to different antenna 652 via respective transmitters 654 TX. Each transmitter 654TX modulates an RF carrier with a respective spatial stream for transmission.

At the eNB610, the UL transmissions are processed in a manner similar to that described in connection with the receiver functionality at the UE 650. Each receiver 618RX receives a signal through its respective antenna 620. Each receiver 618RX recovers information modulated onto an RF carrier and provides the information to an RX processor 670. RX processor 670 may implement the L1 layer.

The controller/processor 675 implements the L2 layer. The controller/processor 675 can be associated with a memory 676 that stores program codes and data. The memory 676 may be referred to as a computer-readable medium. In the UL, the controller/processor 675 provides demultiplexing between transport and logical channels, packet reassembly, deciphering, header decompression, control signal processing to recover upper layer packets from the UE 650. Upper layer packets from the controller/processor 675 may be provided to the core network. The controller/processor 675 is also responsible for error detection using ACK and/or NACK protocols to support HARQ operations.

Certain aspects of the present disclosure provide techniques that may help resolve ambiguities between a base station and a User Equipment (UE), which relate to the ability of the UE to handle resources reserved for a particular purpose. One example of this ambiguity is that the base station does not determine whether the UE can properly process the subframe in case of REs for CSI-RS or REs in which PDSCH muting is performed.

In lte rel-8/9/10, data transmission via PDSCH may be dynamically scheduled or semi-persistently scheduled. The PDCCH may be used to dynamically schedule PDSCH or to activate/deactivate semi-persistent PDSCH transmissions. Each UE120 may be semi-statically configured to operate in a Downlink (DL) Transmission (TX) mode. In each dl tx mode, UE120 may need to monitor two different Downlink Control Information (DCI) sizes from two or more DCI formats (depending on whether the DCI is located in a common search space or a UE-specific search space).

For example, in a common search space, DCI formats 1A/0/3/3a (which have the same size) and 1C may be received. Furthermore, in the common search space, up to 6 PDCCH decoding candidates (4 with aggregation level 4 and 2 with aggregation level 8) may need to be processed. In general, aggregation level N has N Control Channel Elements (CCEs), each CCE has 36 Resource Elements (REs), and each RE is one frequency-time unit.

In the UE-specific search space, DCI formats 1A/0 (which have the same size) and other DLTX mode-related formats (e.g., 1B, 1D, 2A, 2B, 2C, etc.) may be received. In the UE-specific search space, up to 16 PDCCH decoding candidates may need to be processed (6 with aggregation level 1, 6 with aggregation level 2, 2 with aggregation level 4, and 2 with aggregation level 8).

Broadcast transmissions (e.g., system information, paging, RACH response, group power control, etc.) may always use the PDCCH in the common search space. UE-specific transmission may use PDCCH in UE-specific search spaces as well as common search spaces (e.g., if DCI format 1A/0 is used).

One purpose of having DCI format 1A in all DL transmission modes is for so-called "fallback operation". As used herein, the term fallback operation generally refers to a need for an eNB to have a way to communicate with a UE regardless of the operating state of the wireless network. For example, various periods of ambiguity may occur in a wireless network in which the eNB and UE are not synchronized with respect to the capability and/or configuration of the UE.

For example, during RRC (layer 3) reconfiguration of a UE from one DL transmission mode to another, there may be a period during which the eNB may not be certain whether a given UE is still in the old mode or has switched to the new mode. If the eNB needs to send DL data to the UE during this operation ambiguity period, DCI format 1A and its associated DL transmission scheme (e.g., transmit diversity) may be used. As a result, communication between the eNB and the UE can be performed without any interruption.

Another example of operational ambiguity can occur when the antenna port to the RE assigned to reference signal transmission changes. When the mapping changes, the number of muted REs (as understood by the eNB and UE) may be different during a certain time period. In some designs, the operational ambiguity may exist for about 5 to 10 subframes (milliseconds).

The mode-related DCI formats (1, 1B, 1D, 2A, 2B, 2C, etc.) are typically associated with a particular PDSCH transmission scheme (e.g., CRS-based open-loop spatial multiplexing, CRS-based closed-loop spatial multiplexing, DM-RS based spatial multiplexing, rank 1 beamforming, etc.).

Example PDSCH resource mapping

In Rel-8/9/10, PDSCH resource mapping is conventionally performed first in frequency and then in time, as shown in the example resource map 700 of fig. 7. The resource map 700 shows the order in which PDSCH resources are allocated. In the depicted resource diagram 700, region 702 represents resource elements allocated to control messages and region 704 represents resource elements allocated to data transmissions. The PDSCH is the resource allocated first from the lowest frequency to the highest frequency in the same time slot (line 706), followed by the next time slot (line 708) in which the resource is allocated again starting from the lowest available frequency to the highest available frequency.

In LTE-a, the number of configured support antennas has increased from a maximum of 4 × 4 to 8 × 8 with respect to previous LTE releases, which presents a challenge for RS overhead with 8Tx antennas. The solution adopted is to decouple the RS for channel feedback and the RS for demodulation, i.e. the CSI-RS (channel state information reference signal) for channel feedback and the DM-RS for demodulation.

Similar to CRS, CSI-RS is also a reference signal shared by UEs in the same cell. The CSI-RS is not precoded, the CSI-RS is sparse in frequency and time and not correlated with CRS antenna ports. The CSI-RS has the following characteristics: the CSI-RS density is 1 RE per port per PRB; the number of CSI-RS ports has values of 1, 2, 4 and 8; signaling the number of CSI-RS ports with 2 bits; the CSI-RS configuration is cell-specific and signaled by 5 bits via a higher layer; and if the CSI-RS is not configured, it does not occur in the cell.

A Rel-10UE may assume PDSCH rate matching around CSI-rse for all unicast PDSCH transmissions in any transmission mode (e.g., after the eNB knows the UE's capabilities (i.e., its version)).

To be further compatible, especially for CoMP (coordinated multipoint transmission) operation, support for PDSCH muting in lte rel-10 is agreed. The PDSCH muting configuration may be UE-specific and signaled via higher layers and performed on a bandwidth following the same rules as CSI-RS. The position within the subframe of the muted resource elements is indicated by a 16-bit bitmap, where each bit corresponds to a 4-port CSI-RS configuration, all REs used in the CSI-RS configuration are muted (zero power assumed at the UE) except for the CSI-rse belonging to the 4-port CSI-RS configuration set to 1, and the signaling is common for FDD and TDDCSI-RS configurations.

When muting of PDSCHRE is configured, the Rel-10UE may assume PDSCH rate matching around muted REs for all unicast PDSCH transmissions in any transmission mode (e.g., after eNB110 knows the capability of the UE (i.e., its version)). However, a "legacy" UE (e.g., Rel-10 or earlier) may not support muting and/or CSI-RS. Therefore, there may be periods of ambiguity when the base station lacks information about the release standard release supported by the UE.

A single value of subframe offset for all muted resource elements and duty cycle may be signaled using the same coding as for subframe offset and duty cycle of CSI-RS. In some designs, the muted REs may not be located in subframes that do not have CSI-RS. In other designs, the muted REs may be located in subframes that do not have CSI-RS, and in this case, the CSI-RS duty cycle is an integer multiple of the muted RE duty cycle.

Example interaction of PDSCH resource mapping, CSI-RS, and muting

Fig. 8 illustrates an example resource map 800, the resource map 800 illustrating possible rate matching scenarios within RBs when PDSCH muting is configured. The following configuration may be signaled to the UE: resource Elements (REs) reserved for special purposes are identified (e.g., reference signals used for measuring channel feedback (e.g., CSI-RS) and/or PDSCH muting).

In the example shown in fig. 8, a given cell has 8 REs reserved for special purposes. Specifically, diagram 800 has 4 CSI-RS ports occupying 4 REs (labeled "C") that are not available for PDSCH and 4 additional REs (labeled "M"), which are also not available for PDSCH. These 4 additionally muted REs may provide protection for CSI-rse of neighboring cells and, thus, may facilitate dl comp operations.

When performing PDSCHRE mapping, it may be desirable not to map these 8 REs for CSI-RS and muting (i.e., rate matching may be performed around these 8 REs). However, for legacy UEs (referring to UEs that are not capable of processing CSI-RS or muting) or UEs that are not aware of such muting, the 4 muted REs should be part of the PDSCHRE mapping operation.

However, this gives a potentially ambiguous period, for example, when the UE is exchanging messages with the eNB in an attempt to access the network. In some designs, unicast PDSCH transmissions sent before the UE communicates its version information to the eNB may not exclude REs signaled by the eNB for PDSCH muting operations. For example, message 4 (Msg 4) is an example message, which is more commonly referred to as a collision resolution message from the eNB to the UE.

When a UE attempts to access a lte eNB using a Physical Random Access Channel (PRACH), there are typically 4 messages exchanged between the eNB and the UE. Message 4 is the last message during the access procedure, which is sent from the eNB to the UE. Since eNB110 is not expected to know the version of UE120 (e.g., Rel-8 or Rel-10) at message 4, in some designs, PDSCH muting operation may not be performed for message 4 even though the eNB broadcasts support for PDSCH muting operation. Otherwise, the UE may not receive message 4 correctly.

Thus, for message 4, PDSCH muting operations may not be performed for message 4, in accordance with certain aspects of the present disclosure. That is, PDSCH rate matching for message 4 may not exclude REs signaled by the eNB for PDSCH muting operation. Note that the eNB may choose to mute or not mute these REs signaled for PDSCH muting operation, but PDSCH rate matching for message 4 may always include these REs.

The ambiguity period may not exist for a UE in connected mode. For example, for a UE in connected mode, there is downlink data arrival, which triggers a RACH procedure at the UE. In this case, the UE includes its MAC-ID in message 3 (Msg 3). In this case, the eNB uses the MAC-ID message to identify the version information of the UE so that when the eNB transmits the PDSCH to the UE, it can determine whether to perform rate matching around the muted tones.

It should be noted that when a UE attempts to decode a unicast PDSCH, it typically relies on its version information (rel-10 UE or rel-8/9 UE) and eNB version information to determine whether to assume that the PDSCH has rate matching around the mute tones. The eNB version information is indicated by whether or not muting is supported in system information transmitted by the eNB.

During handover, the target eNB may communicate such information to the source eNB, and, in turn, the source eNB may communicate such information to the UE in a handover message.

The ambiguity period may also occur when there is any reconfiguration of the CSI-RS ports and/or any reconfiguration of PDSCH muting operations. In this case, there may be certain periods of ambiguity during which the eNB and UE in the cell may not be aligned with respect to the actual CSI-RS port and/or PDSCH muting operation used.

During this period of ambiguity, it is possible for the UE to perform blind detection according to different assumptions. For example, it may assume that PDSCH rate matching is performed based on a previous configuration (before reconfiguration). As an alternative, PDSCH rate matching may be based on the new configuration. However, in some cases, such blind detection may not be optimal due to associated processing overhead.

In some cases, the eNB may choose to transmit to the UE during the ambiguity period only in subframes that do not have CSI-RS and PDSCH muting. However, such limitations may be severe, especially in heterogeneous networks where some UEs monitor only a limited set of subframes. Furthermore, since the CSI-RS/muting configuration may be broadcast, a large number of UEs may be affected at the same time.

Regardless of the configuration of CSI-RS and/or PDSCH muting operations, certain aspects of the present disclosure may help maintain an uninterrupted connection between an eNB and a UE.

Fig. 9 illustrates example operations 900 that an eNB may perform even in an ambiguous period to help maintain an uninterrupted connection between the eNB and a UE. As illustrated, at 902, when an eNB determines an ambiguity period in which a base station lacks a determination regarding a user equipment (UE)'s ability to support a configuration of resources reserved for a special purpose, at 904, when the eNB transmits a Physical Downlink Shared Channel (PDSCH) in a resource block to the UE during the ambiguity period, the resources reserved for the special purpose may be excluded when the eNB performs rate matching.

According to certain aspects, a "non-legacy" UE may perform operations that are complementary to those illustrated in fig. 9. For example, during a determined period of ambiguity in which the base station lacks the capability of the UE to support the configuration of resources reserved for a special purpose in a subframe, the UE may process the subframe under the following assumptions: when transmitting a Physical Downlink Shared Channel (PDSCH), the base station has excluded resources reserved for a special purpose when performing rate matching.

In some cases, whether REs for a particular purpose are excluded from rate matching may depend on whether one or more particular conditions are met during the ambiguity period. For example, in some cases, for PDSCH transmission, when PDSCH transmission is scheduled using DCI format 1A, the corresponding PDSCH rate matching may not exclude REs reserved for special purposes (e.g., REs reserved for CSI-RS and/or REs reserved for muting).

This may imply that if the UE is configured using a certain downlink transmission mode, the PDSCH rate matching operation for transmissions scheduled via DCI format 1A and the PDSCH rate matching operation for transmissions scheduled via mode-dependent DCI formats (1, 1B, 1D, 2A, 2B, 2C, etc.) may be performed differently.

For example, in case of DCI format 1A, PDSCH rate matching may not subtract (cancel) CSI-RSRE and/or signaled muted REs. Otherwise, PDSCH rate matching may subtract CSI-RSRE and/or signaled muted REs.

Since rollback operations are expected to occur frequently, the above rules may be improved by introducing additional conditions. For example, in some cases, whether or not REs for a special purpose are excluded from rate matching may depend on a DCI format.

For example, in the case of DCI format 1A in the common search space, then PDSCH rate matching may not subtract CSI-RSRE and/or signaled muted REs. On the other hand, if message format 1A is in the UE-specific search space, then PDSCH rate matching may subtract CSI-rse and/or signaled muted REs.

For DCI formats related to a mode, PDSCH rate matching may subtract CSI-rse and/or signaled muted REs.

Further improvements based on search space characteristics are also necessary. For example, in some cases, these improvements are necessary (or at least desirable) when the common search space overlaps with the UE-specific search space. This is particularly true when the control region is relatively small and another period of ambiguity may arise.

For example, if the UE receives a unicast PDSCH with PDCCH format 1A using PDCCH decoding candidates from overlapping search regions, the UE may not know whether the PDSCH is scheduled from the common search space or from the UE-specific search space, and therefore, whether it should apply rate matching by deducting CSI-RSRE and/or signaled muted REs.

One possible approach to address this ambiguity is to allow only transmissions from the common search space or only transmissions from the UE-specific search space.

In some cases, it may be preferable to allow transmissions from a common search space. By doing so, whenever the UE receives a unicast PDSCH with PDCCH format 1A using overlapping search spaces, the UE may assume it is from the common search space and CSI-REs and/or signaled muted REs may not be subtracted from PDSCH rate matching. From the eNB side, the eNB may take measures to ensure that the same operation is done in such a case.

The present disclosure addresses problems arising in the interaction of CSI-RS and PDSCH muting operations with respect to PDSCH resource mapping. In particular, some problems may arise from fallback operations during message 4 (MSG 4) transmission and reconfiguration, and certain aspects of the present disclosure may help address these problems.

It will be appreciated that certain aspects of the present disclosure provide techniques for detecting an ambiguous situation and operating when an ambiguous situation is detected. In some designs, the CSI-RS is selectively deducted during rate matching operations based on knowledge of a version number of the UE.

It will also be appreciated that a rollback operation is disclosed. Using the fallback operation, the eNB can maintain communication with the UE by communicating using a predetermined message format regardless of the version number of the UE. In some designs, puncturing is performed only on REs and no rate matching is performed around the punctured REs.

It will also be appreciated that the techniques presented herein may be particularly useful during operation of a wireless network when REs allocated to CSI-RSs change due to changes in antenna port-to-RE mapping (e.g., antenna port number changes). During this time, there may be ambiguity as to how many REs to mute (e.g., to avoid interfering with CSI-RS transmissions of neighboring cells).

In some cases, the eNB may perform muting on resource elements reserved for PDSCH muting operations, although these resource elements are excluded when performing rate matching.

Fig. 10 is a conceptual dataflow diagram 1000 that illustrates the flow of data between different modules/components within an exemplary apparatus 1010 that is capable of performing the operations described herein (and is shown in fig. 9). The apparatus 1010 includes a module 1002 for determining, by a base station, an ambiguity period in which the base station lacks a determination regarding a user equipment (UE)'s ability to support a configuration of resources reserved for a special purpose, and a module 1004 for excluding resources reserved for the special purpose when performing rate matching when transmitting a Physical Downlink Shared Channel (PDSCH) to the UE in a resource block during the ambiguity period. The apparatus 1010 may further include a sending module 1008 and a receiving module 1006.

These modules may be one or more hardware components specifically configured to execute the processes/algorithms, implemented by a processor configured to execute the processes/algorithms, stored within a computer-readable medium, implemented by a processor, or some combination thereof.

Fig. 11 is a schematic diagram illustrating an example of a hardware implementation of an apparatus 1110 using a processing system 1114. The processing system 1114 may be implemented with a bus architecture, represented generally by the bus 1106. The bus 1106 may include any number of interconnecting buses and bridges depending on the specific application of the processing system 1114 and the overall design constraints. The bus 1106 links together various circuits including one or more processors and/or hardware modules, represented generally by the processor 1120, as well as the modules 1102, 1104 and the computer-readable medium 1122. The bus 1106 may also link together various other circuits such as timing sources, peripherals, voltage regulators, and power management circuits, which are known in the art, and therefore, will not be described any further.

The processing system 1114 is coupled to a transceiver 1130. The transceiver 1130 is coupled to one or more antennas 1132. The transceiver 1130 provides a means for communicating with various other apparatus over a transmission medium. The processing system 1114 includes a processor 1120 coupled to a computer-readable medium 1122. The processor 1120 may also be responsible for general processing, including the execution of software stored on the computer-readable medium 1122. When the processor 1120 executes software (e.g., instructions), the software causes the processing system 1114 to perform the various functions described above for any particular apparatus. The computer-readable medium 1122 may also be used for storing data that is manipulated by the processor 1120 when executing software. The processing system also includes modules 1102 and 1104. The modules may be software modules running in the processor 1120 located/stored in the computer-readable medium 1122, one or more hardware modules coupled to the processor 1120, or some combination thereof. The processing system 1114 may be a component of the UE650 and may include the memory 660 and/or at least one of the TX processor 668, the RX processor 656, and the controller/processor 659 shown in fig. 6.

In one configuration, an apparatus for wireless communication includes means for performing each of the operations shown in fig. 9. The modules may be one or more of the modules of the apparatus 1010 and/or the processing system 1114 of the apparatus 1110 configured to perform the functions recited by the modules. As described supra, the processing system 1114 may include the TX processor 668, the RX processor 656, and the controller/processor 659. Thus, in one configuration, the modules may be the TX processor 668, the RX processor 656, and the controller/processor 659 configured to perform the functions recited by the modules.

It should be understood that the specific order or hierarchy of steps in the processes disclosed is an illustration of exemplary approaches. It should be understood that the particular order or hierarchy of steps in the processes may be rearranged based on design preferences. Further, some steps may be combined or omitted. The accompanying method claims present elements of the various steps in a sample order, and are not meant to be limited to the specific order or hierarchy presented.

The previous description is provided to enable any person skilled in the art to practice the various aspects described herein. Various modifications to these aspects will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other aspects. Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language claims, wherein reference to an element in the singular is not intended to mean "one and only one" unless specifically so stated, but rather "one or more. The term "some" means one or more unless explicitly stated otherwise. All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Furthermore, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. Unless the phrase "module for … …" is used to explicitly recite the element, the element must not be interpreted as a functional module architecture.

Claims (31)

1. A method of wireless communication, comprising:

determining, by a base station, an ambiguity period in which the base station lacks a determination regarding a user equipment, UE, ability to support a configuration of resources reserved for a special purpose in a subframe, wherein the configuration identifies resource elements reserved for reference signals used for measuring channel feedback and/or the configuration identifies resource elements reserved for PDSCH muting operation; and

excluding the resources reserved for special purposes when performing rate matching when transmitting a physical downlink shared channel, PDSCH, to the UE in the subframe during the ambiguity period.

2. The method of claim 1, wherein the excluding is performed after signaling the configuration of the resources reserved for the special purpose.

3. The method of claim 1, wherein the period of ambiguity comprises a period during which the base station lacks information about a release version of a standard supported by the UE.

4. The method of claim 3, wherein the period of ambiguity comprises a period during which the UE is attempting to access the base station but before the UE transmits message information regarding a release version of a standard supported by the UE.

5. The method of claim 1, further comprising:

muting is performed on the resource elements reserved for PDSCH muting operation, although the resource elements reserved for PDSCH muting operation are excluded when performing rate matching.

6. The method of claim 1, wherein the period of ambiguity follows a reconfiguration of resources of the subframe to be used for a special purpose.

7. The method of claim 6, wherein the excluding comprises excluding only if one or more conditions are satisfied during the period of ambiguity.

8. The method of claim 7, wherein whether the one or more conditions are met depends on a format of Downlink Control Information (DCI) used to schedule the PDSCH.

9. The method of claim 8, wherein whether the one or more conditions are met depends on whether DCI format 1A is used to schedule the PDSCH.

10. The method of claim 9, wherein whether the one or more conditions are met depends on whether the PDSCH is transmitted in a common search space or a UE-specific search space.

11. The method of claim 9, wherein whether the one or more conditions are met depends on whether the PDSCH is transmitted in a common search space that overlaps a UE-specific search space.

12. A method of wireless communication, comprising:

determining, by a user equipment, UE, an ambiguity period in which a base station lacks a determination regarding the UE's ability to support a configuration of resources reserved for special purposes in a subframe, wherein the configuration identifies resource elements reserved for reference signals used for measuring channel feedback and/or the configuration identifies resource elements reserved for PDSCH muting operation; and

processing the subframes under the following assumptions: when transmitting a physical downlink shared channel, PDSCH, to the UE in the subframe during the ambiguity period, the base station has excluded the resources reserved for special purposes when performing rate matching.

13. The method of claim 12, wherein the period of ambiguity comprises a period during which the base station lacks information about a release version of a standard supported by the UE.

14. The method of claim 13, wherein the period of ambiguity comprises a period during which the UE is attempting to access the base station but before the UE transmits message information regarding a release version of a standard supported by the UE.

15. The method of claim 12, wherein the period of ambiguity follows a reconfiguration of resources of the subframe to be used for a special purpose.

16. The method of claim 15, wherein whether or not it is assumed that excluding is performed depends on a format of Downlink Control Information (DCI) used to schedule the PDSCH.

17. The method of claim 16, wherein whether or not it is assumed that exclusion is performed depends on whether DCI format 1A is used to schedule the PDSCH.

18. The method of claim 16, wherein whether or not it is assumed that exclusion is performed depends on whether the PDSCH is transmitted in a common search space or a UE-specific search space.

19. The method of claim 16, wherein whether the excluding is performed depends on whether the PDSCH is transmitted in a common search space that overlaps a UE-specific search space.

20. An apparatus for wireless communication, comprising:

means for determining, by a base station, an ambiguity period in which the base station lacks a determination regarding a user equipment, UE, ability to support a configuration of resources reserved for special purposes in a subframe, wherein the configuration identifies resource elements reserved for reference signals used for measuring channel feedback and/or the configuration identifies resource elements reserved for PDSCH muting operation; and

means for excluding the resources reserved for special purposes when performing rate matching when transmitting a Physical Downlink Shared Channel (PDSCH) to the UE in the subframe during the ambiguity period.

21. The apparatus of claim 20, wherein the period of ambiguity comprises a period during which the UE is attempting to access the base station but before the UE transmits message information regarding a release version of a standard supported by the UE.

22. The apparatus of claim 20, wherein the period of ambiguity follows a reconfiguration of resources of the subframe to be used for a special purpose.

23. The apparatus of claim 22, wherein the means for excluding the resources reserved for special purposes comprises means for excluding only if one or more conditions are met during the period of ambiguity.

24. The apparatus of claim 23, wherein whether the one or more conditions are met depends on a format of Downlink Control Information (DCI) used to schedule the PDSCH.

25. An apparatus for wireless communication, comprising:

means for determining, by a User Equipment (UE), an ambiguity period in which a base station lacks a determination regarding the UE's ability to support a configuration of resources reserved for special purposes in a subframe, wherein the configuration identifies resource elements reserved for reference signals used to measure channel feedback and/or the configuration identifies resource elements reserved for PDSCH muting operation; and

means for processing the subframe under the following assumptions: when transmitting a physical downlink shared channel, PDSCH, to the UE in the subframe during the ambiguity period, the base station has excluded the resources reserved for special purposes when performing rate matching.

26. The apparatus of claim 25, wherein the period of ambiguity comprises a period during which the UE is attempting to access the base station but before the UE transmits message information regarding a release version of a standard supported by the UE.

27. The apparatus of claim 25, wherein the period of ambiguity follows a reconfiguration of resources of a subframe to be used for a special purpose.

28. The apparatus of claim 27, wherein the means for processing the subframe is configured to assume exclusion only if one or more conditions are satisfied during the period of ambiguity.

29. The apparatus of claim 28, wherein whether the one or more conditions are met depends on a format of Downlink Control Information (DCI) used to schedule the PDSCH.

30. An apparatus for wireless communication, comprising:

at least one processor configured to: determining, by a base station, an ambiguity period in which the base station lacks a determination regarding a user equipment, UE, ability to support a configuration of resources reserved for a special purpose in a subframe and excludes the resources reserved for a special purpose when performing rate matching when transmitting a physical downlink shared channel, PDSCH, to the UE in the subframe during the ambiguity period, wherein the configuration identifies resource elements reserved for reference signals used for measuring channel feedback and/or the configuration identifies resource elements reserved for PDSCH muting operation; and

a memory coupled with the at least one processor.

31. An apparatus for wireless communication, comprising:

at least one processor configured to: determining, by a user equipment, UE, an ambiguity period in which a base station lacks a determination regarding the UE's ability to support a configuration of resources reserved in a subframe for a special purpose, and processing the subframe under the following assumption: when transmitting a physical downlink shared channel, PDSCH, to the UE in the subframe during the ambiguity period, the base station has excluded the resources reserved for special purposes when performing rate matching, wherein the configuration identifies resource elements reserved for reference signals used for measuring channel feedback and/or the configuration identifies resource elements reserved for PDSCH muting operation; and

a memory coupled with the at least one processor.