Method and apparatus for configuring, measuring, and reporting channel status information for LTE TDD with dynamic UL / DL configuration

Abstract

A method and apparatus for configuring, measuring, and reporting channel state information for a Long Term Evolution (LTE) TDD system with dynamic uplink-downlink (UL / DL) configuration is provided. [Solution] A method for operating a time division duplex (TDD) wireless communication system, in which a base station (eNB) 720 establishes communication with a user equipment (UE) 700, determines and transmits a subframe configuration including static subframes and flexible subframes to the UE 700, and receives a channel state information (CSI) report from the UE 700 in response to the subframe configuration.

Description

[Technical Field]

[0001] This application relates in general to wireless communication systems, and more particularly to the operation of a time-division duplex communication system that includes dynamic reconfiguration of downlink (DL) time slots and uplink (UL) time slots in which user equipment (UE) communicates with one or more base stations. [Background technology]

[0002] In orthogonal frequency division multiplexing (OFDM), multiple symbols are transmitted on multiple carriers spaced apart to provide orthogonality. An OFDM modulator typically inputs data symbols into a serial-parallel converter, the output of which is frequency-domain data symbols. Frequency-domain tones at both ends of the bandwidth can be set to zero and are called guard tones. These guard tones can help fit the OFDM signal to a suitable spectral mask. Some of the frequency-domain tones are set to values ​​that may be known at the receiver. These include the cell-specific reference signal (CRS), the channel-state information reference signal (CSI-RS), and the demodulation reference signal (DMRS). These reference signals are useful for channel and interference measurements at the receiver. The cell-specific reference signal and the channel-state information reference signal are not pre-encoded and are generated by a pseudo-random sequence generator as a function of the physical cell ID. In Releases 8-10 of the Long-Term Evolution (LTE) of the Universal Mobile Telecommunications System (UMTS), designed for conventional point-to-point communication, the cell ID is not explicitly signaled by the base station (referred to as the eNB), but is implicitly derived by the UE as a function of the primary synchronization signal (PSS) and secondary synchronization signal (SSS). To connect to the wireless network, the UE performs a downlink cell search to synchronize to the best cell. The cell search is performed by detecting the PSS and SSS of each available cell, such as in terms of reference signal received power (RSRP), and comparing their respective signal quality. After the cell search is performed, the UE establishes a connection with the best cell by deriving the relevant system information for that cell. Similarly, in LTE Release 11, the UE performs an initial cell search to connect to the best cell. To enable multipoint CoMP operations, connected cells constitute the UE with a higher layer of signaling, each with a virtual cell ID for each CSI-RS resource associated with each base station involved in the multipoint CoMP operation.The UE generates a pseudo-random sequence for each CSI-RS resource as a function of the virtual cell ID.

[0003] Conventional cellular communication systems operate using a point-to-point single-cell transmission scheme, in which a user terminal or device (UE) is uniquely connected to and served by a single cellular base station (eNB or eNodeB) at a given time. An example of such a system is 3GPP Long Term Evolution Release 8. Advanced cellular systems are intended to further improve data rates and performance by employing multi-point-to-point or coordinated multi-point (CoMP) communication, where multiple base stations can coordinate to design downlink transmissions to serve UEs simultaneously. An example of such a system is the 3GPP LTE Advanced System. This significantly improves the received signal strength at each UE by transmitting the same signal from different base stations to each UE. This is particularly beneficial for cell edge UEs that experience strong interference from neighboring base stations.

[0004] Figure 1 shows an exemplary wireless telecommunications network 100 including base stations 101, 102, and 103. In operation, the network 100 includes more base stations. Each of base stations 101, 102, and 103 (eNB) is capable of operating across corresponding coverage areas 104, 105, and 106. Each base station's coverage area is further divided into cells. In the exemplary network, each base station's coverage area is divided into three cells. A handset or other user equipment (UE) 109 is shown in cell A108. Cell A108 is located within base station 101's coverage area 104. Base station 101 transmits a transmission to UE 109 and receives it from UE 109. As UE 109 moves out of cell A108 into cell B107, UE 109 may be handed over to base station 102. Since UE109 is synchronized with base station 101, UE109 can use asynchronous random access for handover to base station 102. UE109 also uses asynchronous random access to request the allocation of time, frequency, or code resources on uplink 111. When UE109 has data ready for transmission (which could be user data, measurement reports, or tracking area updates), UE109 may transmit a random access signal on uplink 111. This random access signal notifies base station 101 that UE109 is requesting the uplink resource to transmit UE data. Base station 101 responds by transmitting a message to UE109 via downlink 110 containing the parameters of the resource allocated for UE109 uplink transmission, along with any timing error corrections that may occur. After receiving resource allocation and any timing warning messages transmitted by base station 101 over downlink 110, UE 109 optionally adjusts its transmission timing and uses this allocated resource to transmit data over uplink 111 for a predetermined time interval. Base station 101 constructs UE 109 for periodic uplink sounding reference signal (SRS) transmission.Base station 101 estimates uplink channel quality information (CQI) from this SRS transmission.

[0005] Conventional wireless communication systems operate in either frequency division duplex (FDD) mode or time division duplex (TDD) mode. In FDD mode, a pair of radio frequency (RF) carriers are assigned to the downlink and uplink directions of the communication system, respectively. In contrast, TDD systems operate on the same RF carrier with time-multiplexed uplink and downlink transmissions within fixed time intervals. The ratio of UL and DL transmissions within fixed time intervals can be selected according to the UL / DL data traffic pattern or to support the coexistence of different TDD wireless systems. User equipment in a TDD system operates in half-duplex mode, so that user equipment can receive from or transmit to a base station at any given time, but not transmit / receive simultaneously.

[0006] Figure 2 shows the Long-Term Evolution (LTE) TDD system. A 10-millisecond (ms) radio frame is divided into 1-ms subframes, and each subframe set is either a downlink (D), uplink (U), or special subframe (S). Seven uplink-downlink (UL / DL) configurations have different uplink, downlink, and special subframe patterns. The eNB selects one of these seven UL / DL configurations for the cell under its control and broadcasts the configuration in the system information. User equipment served by the eNB decodes the cell's system information to determine the correct uplink / downlink subframe configuration for that cell.

[0007] Figure 3 shows a diagram of downlink subframes in LTE. Each subframe set contains 12 OFDM symbols with an Extended Cyclic Prefix (CP) or 14 OFDM symbols with a Normal Cyclic Prefix (CP). The system bandwidth 315 consists of several L physical resource blocks (PRBs), each PRB consisting of 12 OFDM tones called subcarriers. PRBs are minimum time frequency resource allocation units in LTE, and data transmission to users is scheduled on one or more PRBs. Different PRBs in a single subframe set 301 are allocated for data transmission to different users. Also, the set of PRBs on which a user receives downlink data transmission can change from one subframe set to another.

[0008] Figure 4 shows a diagram of a special subframe in an LTE TDD system. The special subframe 400 consists of a downlink pilot time slot (DwPTS) 401, a guard period 402, and an uplink pilot time slot (UpPTS) 403. The guard period (GP) 402 allows the user equipment to switch from receive mode to transmit mode. The GP period can be dimensioned to support coexistence between different TDD systems, such as coexistence between LTE TDD and Time Division Synchronous Code Division Multiple Access (TD-SCDMA). Downlink data transmission can occur in the DwPTS area 401, which supports 3 and 12 OFDM symbols. The UpPTS area 403 consists of 1 or 2 OFDM symbols and can be used for either transmission over a physical random access channel or transmission of SRS to an eNB.

[0009] In addition to downlink data, the base station also transmits control information to mobile users. This includes both common control information and user-specific control information. Common control information is transmitted to all users in a cell to maintain user connectivity to the network, to page users into idle mode when a call arrives, to schedule random access responses, and to indicate critical system information changes in the cell. User-specific control information is transmitted to each scheduled user to indicate the frequency resources on which the UE is expected to receive downlink data or transmit uplink data, etc. Referring to Figure 3, each LTE subframe is divided into a legacy control area 306 for downlink control information transmission and a data area 307 for downlink data transmission. The legacy control area 306 includes OFDM symbols 1-3 when the system bandwidth is greater than 10PRB, and OFDM symbols 2-4 otherwise. The exact size of the legacy control area is signaled on the Physical Downlink Control Format Indicator Channel (PCFICH). The data channel area 307 is located after the legacy control channel area 306 and is allocated to each physical resource block (PRB). The legacy control channel area 306 is the area to which the physical downlink control channel (PDCCH) is mapped. The data channel area 307 is the area to which the physical downlink shared channel (PDSCH) is mapped and carries downlink data transmission to mobile users. Furthermore, the extended physical downlink control channels EPDCCH Set 1 309 and EPDCCH Set 2 313 are frequency multiplexed on the data channel (PDSCH) 311 for transmission to the UE. Thus, EPDCCH Set 1 309 and EPDCCH Set 2 313 are mapped to the data channel area 307 together with PDSCH 311. The legacy control channel area is placed at the beginning of the subframe so that the UE first receives the PDCCH allocated to the legacy control channel area 306 in order to recognize the presence of PDSCH transmission.After the presence of a PDSCH transmission is recognized, the UE can determine whether or not to perform a PDSCH receive operation. If there are no PDCCHs being transmitted to the UE, it is not necessary to receive the PDSCH mapped to the data channel area 307. Thus, the UE can conserve power consumed in the PDSCH receive operation. On the other hand, the UE may receive PDCCHs located in the control channel area earlier than PDSCH 311 to reduce scheduling delays. However, interference control is impossible because PDCCHs are transmitted across the entire system bandwidth.

[0010] The legacy control channel region 306 may not be modified in its frequency multiplexing structure to maintain compatibility with existing or legacy UEs. However, if the eNodeB does not allocate the corresponding region of the data channel region 307 to an earlier LTE version UE, the earlier LTE version UE will not receive the resources mapped to the corresponding data channel region 307. Therefore, the eNodeB may transmit the EPDCCH to the new LTE version UE in the data channel region 307 that has not been allocated to the UE. For example, the EPDCCH, which is the control channel for the new LTE version UE, may have a structure that is multiplexed with the PDSCH.

[0011] Figure 5 shows a diagram of physical resource block (PRB) pairs. An eNB can consist of 1, 2, 4, or 8 PRB pairs for transmission to the UE. However, each PRB pair is a replica, and only one PRB pair is shown for illustrative purposes. Each column in the subframe diagram corresponds to 12 subcarriers or tones in the OFDM symbol. There are 14 OFDM symbols in the subframe with a normal cyclic prefix (CP). The three OFDM symbols on the left side of the subframe contain resource elements (REs) for the transmission of legacy physical downlink control channels (PDCCH) and legacy cell-specific reference signals (CRS). These three OFDM symbols are provided for backward compatibility with previous wireless standards. The 11 OFDM symbols on the right contain resource elements (REs) for the transmission of extended physical downlink control channels (EPDCCH), demodulated reference signals (DMRS), cell-specific reference signals (CRS), and orphans, or unused REs. Since the UE assumes that 24 REs are reserved for DMRS transmission in the PRB pair configured for EPDCCH transmission, orphan REs may exist.

[0012] The aforementioned approach provides a stable improvement in interference measurement and channel status information reporting for wireless communications, but further improvements are possible. [Overview of the Initiative]

[0013] In the example described, communication is established using a remote transceiver to operate a time-division duplex (TDD) wireless communication system. A subframe configuration, including static and flexible subframes, is determined and transmitted to the remote transceiver. In response to the subframe configuration, a channel status information (CSI) report is received from the remote transceiver. [Brief explanation of the drawing]

[0014] [Figure 1] This is a diagram of a conventional wireless communication system.

[0015] [Figure 2] Table of a conventional LTE TDD uplink / downlink configuration.

[0016] [Figure 3] Figure of a conventional LTE downlink subframe.

[0017] [Figure 4] Figure of a conventional LTE special subframe.

[0018] [Figure 5] Figure of a pair of physical resource blocks (PRBs) according to an exemplary embodiment.

[0019] [Figure 6] Block diagram showing the operation of a user equipment and a base station according to an exemplary embodiment.

[0020] [Figure 7] Figure showing an LTE TDD fixed and flexible subframe configuration according to an exemplary embodiment.

Mode for Carrying Out the Invention

[0021] In a conventional homogeneous TDD network with macrocell deployment, the UL and DL traffic patterns can be substantially static or quasi-static. Thus, the same TDD UL / DL configuration can be used for a time interval in the range of at least several hundred milliseconds (ms) or several hundred seconds. However, in a heterogeneous network (het-net) with small cell deployment, the UL and DL traffic patterns can be even more dynamic in nature. Also, the proximity of neighboring small cells can introduce more variability (dynamism) into inter-cell interference, which can affect system performance and / or capacity. Thus, the wireless system performance can be significantly improved by more rapid adaptation of the TDD UL / DL configuration in response to the dynamic traffic and interference patterns in a het-net. TDD Extended Interference Mitigation and Traffic Adaptation (eIMTA) is a feature of LTE Release 12 that introduces rapid adaptation of the TDD UL / DL configuration by dynamically signaling reconfiguration commands on the PDCCH or EPDCCH. The rate of adaptation can be made as fast as on the order of a 10 ms LTE radio frame. However, the dynamic reconfiguration of the TDD UL / DL configuration may not be applicable to UEs of previous LTE releases such as LTE Release 8 - 11. Thus, while a first UE can be configured to monitor the downlink control channel for changes in the TDD UL / DL configuration, a second UE of a previous release can follow the quasi-static configured TDD UL / DL configuration signaled in the System Information Block Type 1 (SIB1). Different from a conventional LTE TDD system where neighboring cells of the same cellular operator use the same TDD UL / DL configuration, neighboring cells that utilize the eIMTA feature can configure different TDD UL / DL configurations in the same radio frame. This difference can result in inter-cell interference in both UL-DL and DL-UL.

[0022] Channel status information (CSI) is critical to the eNB for scheduling downlink or uplink data transmission to or from user equipment. Therefore, the exemplary embodiment includes a method for configuring, measuring, and reporting CSI to the eNB for dynamic adaptation of the cell's TDD UL / DL configuration.

[0023] Some of the following abbreviations will be used throughout this specification. CCE (Control Channel Element) CQI (Channel Quality Indicator) CRS (Cell-specific Reference Signal) CSI (Channel State Information) CSI-IM (Channel State Information Interference Measurement) CSI-RS (Channel State Information Reference Signal) DCI (Downlink Control Information) DL (Downlink) DMRS (Demodulation Reference Signal) eICIC (Enhanced Inter-Cell Interference Coordination) eIMTA (Enhanced Interference Mitigation and Traffic Adaptation) eNB (E-UTRAN Node B or base station or evolved Node B) EPDCCH (Enhanced Physical Downlink Control Channel) E-UTRAN (Evolved Universal Terrestrial Radio Access Network) feICIC (Further Enhanced Inter-Cell Interference Coordination) HARQ (Hybrid Automatic Repeat Request) ICIC (Inter-Cell Interference Coordination) LTE (Long Term Evolution) MIMO (Multi-Input Multi-Output) PCFICH (Physical Control Format Indicator Channel) PDCCH (Physical Downlink Control Channel) PDSCH (Physical Downlink Shared Channel) PMI (Precoding Matrix Indicator) PRB (Physical Resource Block) PUCCH (Physical Uplink Control Channel) PUSCH (Physical Uplink Shared Channel) RE (Resource Element) RI (Rank Indicator) RRC (Radio Resource Control) SIB1 (System Information Block Type 1) SNR (Signal-to-Noise Ratio) SRS (Sounding Reference Signal) TDD (Time Division Duplex) UE (User Equipment) UL (UpLink) ZP-CSI-RS (Zero-Power Channel State Information Reference Signal)

[0024] Scheduling in wireless networks is achieved by base stations (eNBs in LTE) that transmit downlink control information to mobile terminals (UEs in LTE). In cellular wireless networks, base stations may need to schedule transmissions to multiple mobile users simultaneously, and therefore, base stations need to transmit downlink control information to different users at the same time. Furthermore, base stations may simultaneously transmit different types of control information to UEs, such as common control information and UE-specific control information.

[0025] In LTE, downlink control information bits are carried in Downlink Control Information (DCI) format. DCI is channel-coded, modulated, and transmitted over a specific physical transmission channel via the air interface. In legacy systems, the DCI format is transmitted via the Physical Downlink Control Channel (PDCCH). The PDCCH is transmitted in the legacy PDCCH domain. Different DCI formats are used for different scheduling purposes. DCI can be used to transmit common control information to all users in a cell, UE-specific downlink control information to schedule PDCCH data transmission to the UE, or UE-specific downlink control information to schedule uplink data transmission from the UE to the eNB.

[0026] Table 1 below shows the relationship between the DCI format and the corresponding downlink transmission mode. The DCI format is UE-specific, monitored by the UE, and scrambled by C-RTI.

[0027] In LTE Release 11, a new physical channel, referred to as the Extended Physical Downlink Control Channel (EPDCCH), is defined for transmitting downlink control information within a cell. Referring to Figure 3, as an additional physical resource for control information, the EPDCCH is transmitted in a subset of Physical Resource Blocks (PRBs) in the data domain 307 and outside the legacy PDCCH control domain 306. An eNB may constitute multiple EPDCCH sets in the downlink. Each EPDCCH set includes a subset of PRBs, which are quasi-statically configured by Radio Resource Control (RRC) higher-order signals. In each UE, the configured EPDCCH sets may be orthogonal or partially overlapping. The EPDCCH sets are configured in a UE-specific manner and may be identical or different for different users.

[0028] Figure 5 shows a physical resource block (PRB) pair according to the first embodiment. The eNB can consist of 1, 2, 4, or 8 PRB pairs for transmission to the UE. However, each PRB pair is a replica, and only one PRB pair is shown for illustrative purposes. Each column in the subframe diagram corresponds to 12 subcarriers or tones in the OFDM symbol. There are 14 OFDM symbols in the subframe with a normal cyclic prefix (CP). The three OFDM symbols on the left side of the subframe contain resource elements (RE) for the transmission of legacy physical downlink control channels (PDCCH) and legacy cell-specific reference signals (CRS). These three OFDM symbols are provided for backward compatibility with previous wireless standards. The 11 OFDM symbols on the right contain resource elements (RE) for the transmission of extended physical downlink control channels (EPDCCH), demodulated reference signals (DMRS), cell-specific reference signals (CRS), and orphan signals, or unused REs. The UE assumes that 24 REs are reserved for DMRS transmission in PRB pairs configured for EPDCCH transmission, so orphan REs may exist. Subframes are also divided into extended resource element groups (eREGs). eREGs are used to form extended control channel elements (eCCEs), regardless of whether they belong to localized or distributed EPDCCH candidates. In the example in Figure 3, a single low or tone of a PRB may form one eREG, so there are 12 eREGs in each subframe set for each PRB configured for EPDCCH transmission.

[0029] To facilitate optimal scheduling of downlink data, the UE may be configured to measure and report channel status information to the eNB. The eNB constitutes the UE with a time-frequency CSI reference resource. The frequency portion of the CSI reference resource consists of a set of PRBs for which CSI reporting is enabled. The time component refers to subframes that the UE may receive with a virtual transmission of data carrier blocks at most 10% block error rate. Periodic and / or aperiodic CSI reporting may be configured for the UE, with periodic reports transmitted via PUCCH and aperiodic reports transmitted via PUSCH.

[0030] CSI measurement is a function of SNR observed by the UE. In LTE transmission modes 1-8, the UE measures the channel and interference components of the CSI report from the transmitted cell-specific reference signal (CRS). In LTE transmission modes 9 and 10, the UE may be configured to measure the channel portion based on a channel state information reference signal (CSI-RS). Additionally, a UE operating in transmission mode 10 may be configured to measure the interference portion based on interference measurement resources included in a zero-power CSI-RS configuration.

[0031] In the exemplary embodiment, a combination of legacy LTE (Release 8-11) and an eIMTA-enabled UE may be served by an eNB in ​​the same cell. The legacy UE determines the UL / DL / Special subframe pattern according to the UL / DL subframe configuration signaled in SIB1. The eIMTA-enabled UE may be configured to monitor a PDCCH or EPDCCH carrying DCI packets, including dynamic reconfiguration of the UL / DL subframe configuration. The valid UL / DL configuration received in the detected DCI in the PDCCH or EPDCCH should be one of the seven LTE UL / DL configurations (Figure 2). The UE determines the UL / DL / Special subframe pattern for all radio frames within the reconfiguration time period based on the UL / DL configuration received in the detected DCI. Under TDD-Enhanced Interference Mitigation (eIMTA), DL subframes can be static (always DL) or flexible. A certain subframe has a common direction of either UL or DL ​​across all possible UL / DL configurations. The table in Figure 6 shows that subframe 610 has a static DL direction, subframe 614 has a fixed UL direction, and subframe 612 has a fixed Special subframe. Subframes 616 are relatively static in the context of scheduling DL data transmission because they are either DL or Special subframes. Subframes 618 are flexible subframes because they are either DL or UL depending on the signaled UL / DL configuration.

[0032] Figure 7 shows a diagram of communication between a user device (UE) 700 and a base station (eNB) 720 according to an exemplary embodiment. The UE 700 may be a mobile phone, computer, or other wireless network device. The UE 700 includes a memory 704 and a processor 706 coupled to a transceiver 710. The processor 706 may include several processors adapted to various operational tasks of the UE, including signal processing and channel measurement and arithmetic. The memory stores application software that the processor can execute as instructed by the user, and operational instructions for the UE. The processor 706 is also coupled to an input / output (I / O) circuit element 708, which may include a microphone, speaker, display, and associated software. The transceiver 710 includes a receiver 712 and a transmitter 714 suitable for wireless communication with the eNB 720. The transceiver 710 typically communicates with the eNB 720 over various communication channels. For example, transceiver 710 sends uplink information to eNB720 via the physical uplink control channel PUCCH and the physical uplink shared channel PUSCH. Correspondingly, transceiver 710 receives downlink information from eNB720 via the physical downlink control channel PDCCH and the physical downlink shared channel PDSCH.

[0033] The base station 720 includes a processor 726, which is coupled via a bus 736 to a memory 724, a symbolic processing circuit 728, and a transceiver 730. The processor 726 and the symbolic processing circuit 728 may include several processors adapted to various operational tasks, including signal processing and channel measurement and arithmetic. The memory stores application software that the processor can execute for a particular user, and operational instructions for the eNB 720. The transceiver 730 includes a receiver 732 and a transmitter 734, suitable for wireless communication with the UE 700. The transceiver 730 typically communicates with the UE 700 via various communication channels. For example, the transceiver 730 sends downlink information to the UE 700 via the physical downlink control channel PDCCH and the physical downlink shared channel PDSCH. Correspondingly, the transceiver 730 receives uplink information from the UE 700 via the physical uplink control channel PUCCH and the physical uplink shared channel PUSCH.

[0034] After communication is established using eNB720, transceiver 710 receives an uplink (UL) grant in the downlink (DL) subframe. Transceiver 710 uses CRS or CSI-RS in one or more DL subframes to create a CSI measurement report that is transmitted to eNB720 in the subsequent UL subframe. Static and flexible DL subframes encounter different interference conditions. In flexible subframes, inter-cell interference consists of DL-UL and UL-DL interference, depending on the current UL / DL configuration of neighboring cells. Therefore, to maximize DL or UL throughput, it is advantageous to provide separate CSI interference reports to eNB720 corresponding to each respective subframe set type. In the CSI configuration and reporting by the UE configured for eIMTA operation, a set of DL subframes may be subdivided into two CSI measurement subframe sets, indicated as CSI set 0 and CSI set 1. In one embodiment, CSI set 0 may consist of static subframes 610 as shown in Figure 6, and CSI set 1 may consist of flexible subframes 618 as shown in Figure 6. Since the eNB can configure any subset of subframes in the wireless frame into CSI set 0 or 1, other configurations of CSI subframe sets are not excluded.

[0035] The exemplary embodiment provides the eNB720 with improved CSI interference reporting for both static and flexible DL subframes. CSI measurements for eIMTA operation are performed in DL subframes as determined by either the UL / DL configuration signaled in the SIB1 system information, or the UL / DL configuration dynamically signaled in the PDCCH or EPDCCH. Therefore, if a DL subframe in one radio frame is dynamically signaled to become a UL subframe in a subsequent radio frame, the UE may not perform CSI measurements in the subframe of the subsequent radio frame. In contrast, legacy UEs measure CSI based on CRS and / or CSI-RS only in DL subframes of UL / DL configurations signaled by SIB1. Therefore, to support backward compatibility, DL subframes of SIB1-signaled UL / DL configurations may not be dynamically changed to UL subframes. The static DL subframe set includes DL subframes common to all active LTE TDD UL / DL configurations, and DL subframes according to the SIB1-signaled UL / DL configuration. The advantage of this constraint is that the timing of HARQ-ACK feedback to the UE configured for eIMTA operations in response to previous UL transmissions on the push may follow the UL HARQ timing determined by the SIB1-signaled UL / DL configuration, similar to previous LTE releases. Also, UL grant scheduling transmissions on the push may only be transmitted in static DL subframes (such as CSI subframe set 0). Therefore, it may not be possible to trigger CSI reports for flexible DL subframes that are consistent with legacy CSI timing.

[0036] Several solutions are possible to this problem. In the first solution, the UE700 can provide CSI reports for both static and flexible DL subframes whenever two CSI measurement sets are configured. This may be undesirable as it always requires maximum feedback overhead and significantly increases complexity for the UE700. In the second solution, the DL subframe location can be used to determine which CSI measurement set should be reported. For example, each DL subframe in which a UL grant is transmitted is associated with one of two CSI subframe measurement sets. Alternatively, each UL subframe in which aperiodic CSI is reported is associated with one of two CSI subframe measurement sets. The second solution may also be undesirable as it imposes additional scheduler constraints. In the third solution, additional information can be included in the CSI request field of each UL grant to indicate which CSI subframe measurement set should be reported. This can also be a constraint, as the eNB720 can only trigger one CSI report with one UL grant at a time.

[0037] According to the first embodiment, higher-order signaling from the Radio Resource Control (RRC) layer constitutes a set of CSI subframe measurements to be reported for each state of an existing CSI request field contained in a UL grant. The CSI request field in a UL grant transmitted to the UE may consist of 1 bit when the UE is configured for a single-cell operation, or 2 bits when the UE is configured for either carrier aggregation or CoMP operation. In one exemplary embodiment, the eNB may be configured by RRC signaling to receive a UL grant with a 2-bit CSI field, where "00" indicates no CSI transmission, "01" indicates an aperiodic CSI request for CSI subframe set 0, "10" indicates an aperiodic CSI request for CSI subframe set 1, and "11" indicates an aperiodic CSI request for both CSI subframe sets 0 and 1. Other mapping arrangements of CSI reports for CSI fields in UL grants are not excluded, as flexible CSI reporting configurations may be enabled by RRC signaling. This embodiment advantageously avoids additional UE complexity, scheduler constraints, and CSI reporting constraints. The significance of this embodiment lies in the fact that the CSI reference resource is no longer tied to the subframe carrying the UL grant indicating an aperiodic CSI request. In legacy LTE systems, the DL subframe carrying the UL grant containing an aperiodic CSI request is typically the CSI reference resource, and has an interval of at least 4 ms, including UE processing time, before the associated UL transmission. According to this embodiment, when a CSI report is triggered for a set of subframes, the corresponding CSI reference resource in the time domain is the most recent valid DL subframe before and up to the subframe carrying the UL grant, and is in the subframe set from which the aperiodic CSI report is triggered.If two CSI reports are triggered for two subframe sets by aperiodic CSI requests in the same UL grant, the relevant CSI reference resource for each aperiodic CSI report in the time domain is the most recent valid DL subframe before and up to the subframe carrying the UL grant, and is located in the subframe set from which the aperiodic CSI report is triggered. For example, the CSI reference resource for two aperiodic CSI reports transmitted in a single UL subframe may correspond to two different DL subframes and two different subframe set types (static and flexible). For example, one DL subframe may belong to a set of DL subframes determined by a SIB1-signaled TDD UL / DL configuration, and the other DL subframe may belong to a set of DL subframes of a dynamically signaled TDD UL / DL configuration in PDCCH or EPDCCH.

[0038] In legacy LTE systems, a CSI process is associated with one CSI-RS resource for channel measurement and one Channel State Information Interference Measurement (CSI-IM) resource for interference measurement. According to a second embodiment, a CSI process for eIMTA is associated with one CSI-RS resource and two CSI-IM resources. In one example of this embodiment, each CSI-IM resource may be configured to measure interference observed in static (CSI subframeset 0) and flexible DL subframes (CSI subframeset 1), respectively. The reporting periodicity and subframe offset of each CSI-IM resource are preferably configured by RRC signaling to match the time domain pattern of each subframeset. Thus, CSI-IM 0 is used for interference measurement of CSI subframeset 0, and CSI-IM 1 is used for interference measurement of CSI subframeset 1. In transmission modes in which the UE may be configured with multiple CSI processes, another embodiment supports interference measurements for both static and flexible subframes for each CSI process. In this case, the CSI processing time budget in the UE needs to be increased accordingly. The CSI reference resources also need to be n CQI,ref ≥n threshold This can satisfy a threshold that guarantees a sufficient CSI processing time, where n threshold The threshold is ≥4ms. This processing threshold may be a function of the SIB1 signaled or dynamically signaled TDD UL / DL configuration and / or the number of CSI processes configured.

[0039] In legacy LTE systems, a single CSI process is associated with one non-zero-power CSI-RS resource for channel measurement and one CSI-IM resource for corresponding interference measurement. Furthermore, the frequency domain components of the CSI-IM resource consist of resource elements, which are a subset of resource elements identified by the zero-power CSI-RS configuration. In one embodiment, the UE equipment performs interference measurement using the resource elements of the CSI-IM resource contained within the subframeset. Different alternatives are possible to support two CSI subframesets in eIMTA operation. In one alternative, the configured CSI-IM resource within the subframeset belonging to the CSI reference resource is used to elicit interference measurement. In a different embodiment, the CSI-RS process consists of one CSI-RS resource and two CSI-IM resources associated with CSI subframesets 0 and 1, respectively. The periodicity and subframe offset of each of these CSI-IM resources can be individually configured by RRC signaling to match the pattern of each CSI subframeset. Therefore, CSI measurements for CSI subframeset 0 use CSI-IM 0, and CSI measurements for subframeset 1 use CSI-IM 1. If a single CSI-IM is not sufficiently present in the corresponding subframeset (for example, CSI-IM 0 occurs in some subframes of CSI subframeset 1), then CSI measurements for subframeset 0 (or 1) may use CSI-IM 0 (or CSI-IM 1) only in CSI subframeset 0 (or set 1).

[0040] In periodic CSI feedback on PUCCH, the PUCCH is a narrowband channel with a small payload. In a legacy LTE system, only one CSI report can be transmitted on PUCCH in a subframe. When the UE is configured for eIMTA operation, it is also desirable to support periodic CSI reports of two CSI subframe sets. The CSI report periodicity and subframe offset for each CSI subframe set are independently configured by RRC signaling. In transmission modes 1 to 9, the CSI reference resource associated with PUCCH transmission in subframe n is such that n CQI,ref is the smallest value greater than n threshold = 4 and it is a valid DL subframe and is in the CSI subframe set corresponding to the requested periodic CSI report, the subframe n - n CQI,ref is. In transmission mode 10, the CSI reference resource associated with PUCCH transmission in subframe n is such that n CQI,ref is the smallest value greater than or equal to n threshold = 4 and it is a valid DL subframe and is in the CSI subframe set corresponding to the requested periodic CSI report, the subframe n - n CQI,ref is. Also, the exact value of the threshold n threshold is a function of the number of CSI processes configured for the UE.

[0041] Due to the independent configuration of periodic CSI reports in eIMTA operations, collisions can occur within the same UL subframe, in which case the UE is configured to report CSI measurements for both sets of CSI subframes on the PUCCH. Since only one report can be transmitted in a subframe, a collision handling mechanism is desirable. An exemplary embodiment is configured via an RRC that signals different priorities for different sets of subframes. When CSI reports from different sets of subframes collide within the same UL subframe, the CSI from the higher-priority subframe set is reported, while the lower-priority set of CSI subframes is not transmitted. In legacy LTE TDD systems, priority rules are obtained based on the CSI type (rank vs. CQI / PMI information), and the UE serves an index or CSI process index when configured for carrier aggregation or with multiple CSI processes, respectively.

[0042] Several priority rules are illustrated in the illustrative examples. In the first alternative example, CSI reports are prioritized according to a quasi-static prioritization of CSI subframe sets. For example, if CSI subframe set 0 contains only static DL subframes, it may be given a higher priority than CSI subframe set 1, which contains flexible subframes. Subsequently, tie-breaking rules for collisions may follow, secondly, the CSI type, thirdly, the serving cell index, and finally, the CSI process index.

[0043] Other combinations of this prioritization / tie-breaking rule among the four categories—namely, CSI subframeset, CSI type, serving cell index, and CSI process index—are not excluded. For example, prioritizing spatial multiplexed transmissions may be advantageous in assigning the highest priority according to the CSI type. Thus, the following prioritization rules may be constructed, where the categories in each rule follow a descending priority level. 1. CSI Subframeset Priority - CSI Type - Serving Cell Index - CSI Process Index 2. CSI Type - CSI Subframeset Priority - Serving Cell Index - CSI Process Index 3. CSI Type - Serving Cell Index - CSI Subframeset Priority - CSI Process Index 4. CSI Type - CSI Process Index - Serving Cell Index - CSI Subframeset Priority

[0044] Within the scope of the claims of the present invention, modifications can be made to the exemplary embodiments described, and many other embodiments are possible.

Claims

1. A method for operating a time-division duplex (TDD) communication device, Determining a subframe configuration including static subframes and flexible subframes, wherein the static subframes are signaled by radio resource control (RRC) and the flexible subframes are signaled by downlink control information (DCI) packets, Transmitting the aforementioned subframe configuration, Receiving a Channel Status Information (CSI) report in subframe n, Includes, The CSI reports are selected in descending order of priority, the priority is determined based on the CSI type, CSI process index, serving cell index and CSI subframeset priority, and at least the CSI subframeset priority is configured by the TDD communication device via RRC signaling. The aforementioned CSI report is subframe n-n ＣＱＩ，ｒｅｆ Determined based on the CSI standard resource in n ＣＱＩ，ｒｅｆ gan ｔｈｒｅｓｈｏｌｄ An integer greater than or equal to, n ｔｈｒｅｓｈｏｌｄ However, the method is a function of the number of CSI processes configured for user equipment (UE).

2. The method according to claim 1, A method further comprising transmitting multiple bits in an uplink grant to indicate which subframe is used for the CSI report.

3. The method according to claim 1, The CSI report further includes transmitting a plurality of bits in the uplink grant to indicate whether it is determined from the static subframe, the flexible subframe, or both of these subframes. A method wherein the CSI report includes at least one aperiodic CSI report triggered by the plurality of bits in the uplink grant.

4. The method according to claim 1, A method by which the CSI report is determined in response to a channel state information reference signal (CSI-RS) resource and at least two channel state information interference measurement (CSI-IM) resources.

5. The method according to claim 4, A method in which a first CSI-IM resource determines static subframe interference, and a second CSI-IM resource determines flexible subframe interference.

6. The method according to claim 1, Methods that further include receiving periodic CSI reports.

7. The method according to claim 1, A method further comprising receiving the CSI report in descending order of priority according to the CSI subframeset priority and CSI type, serving cell index and CSI process index.

8. A method for operating a time-division duplex (TDD) communication device, Receiving a subframe configuration including a static subframe and a flexible subframe, wherein the static subframe is signaled by Radio Resource Control (RRC) and the flexible subframe is signaled by Downlink Control Information (DCI) packets, To generate a channel status information (CSI) report in response to the aforementioned subframe configuration, In subframe n, the CSI report is transmitted, Includes, The CSI reports are selected in descending order of priority, the priority is determined based on the CSI type, CSI process index, serving cell index and CSI subframeset priority, and at least the CSI subframeset priority is configured by the TDD communication device via RRC signaling. The aforementioned CSI report is subframe n-n ＣＱＩ，ｒｅｆ Includes at least one non-periodic CSI report determined based on CSI criteria resources in n ＣＱＩ，ｒｅｆ gan ｔｈｒｅｓｈｏｌｄ An integer greater than or equal to, n ｔｈｒｅｓｈｏｌｄ However, the method is a function of the number of CSI processes configured for user equipment (UE).

9. The method according to claim 8, A method further comprising receiving multiple bits in the uplink grant to indicate which subframe is to be used for the CSI report.

10. The method according to claim 8, The uplink grant further includes receiving a plurality of bits to indicate whether the CSI report is determined from the static subframe, the flexible subframe, or both of these subframes. A method wherein the CSI report is triggered by the plurality of bits in the uplink grant.

11. The method according to claim 8, A method wherein the CSI report is generated based on a CSI process, the CSI process comprising a channel state information reference signal (CSI-RS) resource and at least two channel state information interference measurement (CSI-IM) resources.

12. The method according to claim 11, A method in which a first CSI-IM signal determines static subframe interference, and a second CSI-IM signal determines flexible subframe interference.

13. The method according to claim 8, A method further comprising generating a channel status information (CSI) report for one of the static subframe and the flexible subframe.

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