WO2013099284A1 - Procédé de rétroaction de données d'état de canal pour la coordination d'une pluralité de stations de base et équipement d'utilisateur - Google Patents

Procédé de rétroaction de données d'état de canal pour la coordination d'une pluralité de stations de base et équipement d'utilisateur Download PDF

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WO2013099284A1
WO2013099284A1 PCT/JP2012/008428 JP2012008428W WO2013099284A1 WO 2013099284 A1 WO2013099284 A1 WO 2013099284A1 JP 2012008428 W JP2012008428 W JP 2012008428W WO 2013099284 A1 WO2013099284 A1 WO 2013099284A1
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feedback
serving
sub
pmi
type
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PCT/JP2012/008428
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Ming Ding
Zeng YANG
Lei Huang
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Sharp Kabushiki Kaisha
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W16/00—Network planning, e.g. coverage or traffic planning tools; Network deployment, e.g. resource partitioning or cells structures
    • H04W16/24—Cell structures
    • H04W16/28—Cell structures using beam steering
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/0413—MIMO systems
    • H04B7/0456—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0617—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal for beam forming
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B7/00—Radio transmission systems, i.e. using radiation field
    • H04B7/02—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas
    • H04B7/04—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas
    • H04B7/06—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station
    • H04B7/0613—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission
    • H04B7/0615—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal
    • H04B7/0619—Diversity systems; Multi-antenna system, i.e. transmission or reception using multiple antennas using two or more spaced independent antennas at the transmitting station using simultaneous transmission of weighted versions of same signal using feedback from receiving side
    • H04B7/0621—Feedback content
    • H04B7/0626—Channel coefficients, e.g. channel state information [CSI]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/0001—Systems modifying transmission characteristics according to link quality, e.g. power backoff
    • H04L1/0023—Systems modifying transmission characteristics according to link quality, e.g. power backoff characterised by the signalling
    • H04L1/0026—Transmission of channel quality indication
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/02—Arrangements for detecting or preventing errors in the information received by diversity reception
    • H04L1/06—Arrangements for detecting or preventing errors in the information received by diversity reception using space diversity
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0032—Distributed allocation, i.e. involving a plurality of allocating devices, each making partial allocation
    • H04L5/0035—Resource allocation in a cooperative multipoint environment
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0053—Allocation of signaling, i.e. of overhead other than pilot signals
    • H04L5/0057—Physical resource allocation for CQI

Definitions

  • the present invention relates to communication technology, and more particularly, to a method for feeding back Channel State Information (CSI) in a multi-Base station (multi-BS) coordination mode and a user equipment corresponding thereto.
  • CSI Channel State Information
  • MIMO wireless transmission technique can achieve spatial multiplex gain and spatial diversity gain by deploying a plurality of antennas at both the transmitter and the receiver and utilizing the spatial resources in wireless transmission.
  • Researches on information theory have shown that the capacity of a MIMO system grows linearly with the minimum of the number of transmitting antennas and the number of receiving antennas.
  • Fig. 1 shows a schematic diagram of a MIMO system. As shown in Fig. 1, a plurality of antennas at the transmitter and a plurality of antennas at each of the receivers constitute a multi-antenna wireless channel containing spatial domain information.
  • Orthogonal Frequency Division Multiplexing (OFDM) technique has a strong anti-fading capability and high frequency utilization and is thus suitable for high speed data transmission in a multi-path and fading environment.
  • the MIMO-OFDM technique in which MIMO and OFDM are combined, has become a core technique for a new generation of mobile communication.
  • the 3 rd Generation Partnership Project (3GPP) organization is an international organization in mobile communication field and plays an important role in standardization of 3G cellular communication technologies. Since the second half of the year 2004, the 3GPP organization has initiated a so-called Long Term Evolution (LTE) project for designing Evolved UMTS Terrestrial Radio Access (EUTRA) and Evolved UMTS Terrestrial Radio Access Network (EUTRAN).
  • LTE Long Term Evolution
  • EUTRA Evolved UMTS Terrestrial Radio Access
  • EUTRAN Evolved UMTS Terrestrial Radio Access Network
  • the MIMO-OFDM technique is employed in the downlink of the LTE system.
  • LTE-A systems 4G cellular communication systems
  • multi-antenna multi-BS coordination gets extensive attention and support. Its core idea is that multiple BSs can provide communication services for one or more user equipments (UEs) simultaneously, so as to improve data transmission rate for a UE located at the edge of a cell.
  • UEs user equipments
  • Non Patent Literature 1 3GPP, TR 36.814 V9.0.0 (2010-03), "Further advancements for E-UTRA physical layer aspects (Release 9)", which can be outlined as follows:
  • a UE In a multi-antenna multi-BS service, a UE needs to report channel state/statistical information of a link between the UE and each BS/cell in a set of cells. This set of cells is referred to as a measurement set for multi-antenna multi-BS transmission.
  • the set of BSs/cells for which the UE actually performs information feedback can be a subset of the measurement set and is referred to as a coordination set for multi-antenna multi-BS transmission.
  • the coordination set for multi-antenna multi-BS transmission can be the same as the measurement set for multi-antenna multi-BS transmission.
  • a BS/cell in the coordination set for multi-antenna multi-BS transmission participates in Physical Downlink Shared Channel (PDSCH) transmission for the UE, either directly or indirectly.
  • PDSCH Physical Downlink Shared Channel
  • the Physical Downlink Shared Channel is the data channel of the UE.
  • JP Joint Processing
  • the JP scheme needs to share PDSCH signal of the UE among the multiple BSs participating the coordination and can be divided into two approaches.
  • One is referred to as Joint Transmission (JT) in which the multiple BSs transmit their PDSCH signals to the UE simultaneously.
  • the other one is referred to as Dynamic Cell Selection (DCS) in which at any time only one of the BSs which has the strongest signal link is selected to transmit its PDSCH signal to the UE.
  • T Joint Transmission
  • DCS Dynamic Cell Selection
  • the DCS shall be understood in an extended sense of "Transmission Point" (TP), rather than in a limited sense of "cell”.
  • TP Transmission Point
  • transmission point refers to a set of a plurality of transmission ports corresponding to a downlink Reference Signal pattern (CSI-RS Pattern).
  • CSI-RS Pattern downlink Reference Signal pattern
  • CB/CS Coordinated Beamforming/Coordinated Scheduling
  • information feedback is mainly carried out separately for each BS and is transmitted over the uplink resources of the serving BS.
  • the term "information feedback” mainly refers to a process in which a UE feeds back CSI to a BS such that the BS can perform corresponding operations such as radio resource management.
  • CSI feedback There are primarily the following three CSI feedback approaches in the prior art.
  • the UE quantizes all elements in a transceiver channel matrix and feeds back each of the elements to the BS.
  • the UE can analogously modulate all elements in the transceiver channel matrix and feeds back them to the BS.
  • the UE can obtain a transient covariance matrix for the transceiver channel matrix, quantizes all elements in the covariance matrix and feeds back each of the elements to the BS.
  • the BS can reconstruct an accurate channel from the channel quantization information fed back from the UE.
  • This approach is described in detail in Non Patent Literature 2: 3GPP, R1-093720, "CoMP email summary", Qualcomm and its implementation is illustrated in Fig. 2.
  • the UE applies a statistical process on a transceiver channel matrix, e.g., calculating a covariance matrix thereof, quantizes the statistical information and then feeds back it to the BS.
  • the BS can obtain statistical state information of the channel based on the feedback from the UE.
  • This approach is described in detail in Non Patent Literature 2: 3GPP, R1-093720, "CoMP email summary", Qualcomm and its implementation is illustrated in Fig. 3.
  • a finite set of CSI is predefined by the UE and the BS (i.e., codebook space, common codebook spaces including channel rank and/or precoding matrix and/or channel quality indication, etc.).
  • the UE Upon detection of a transceiver channel matrix, the UE searches in the codebook space for an element best matching the CSI of the current channel matrix and feeds back the index of the element to the BS.
  • the BS looks up the predefined codebook space based on the index to obtain rough CSI.
  • the complete CSI feedback has the best performance, but is impractical to be applied to actual system due to the highest feedback overhead.
  • its feedback overhead grows in proportional to the increase of the number of BSs and it is even more impractical.
  • the CSI feedback based on codebook space search has the lowest feedback overhead, but is worst in terms of performance since it cannot accurately describe the channel state such that the transmitter cannot make full use of channel characteristics and cannot perform transmission accordingly.
  • it is extremely simple to implement and can typically accomplish feedback with a few bits.
  • the statistic-based CSI feedback achieves a good tradeoff between these two approaches.
  • this approach can accurately describe the channel state with a relatively small amount of feedback, thereby achieving a relatively ideal performance.
  • the CSI feedback based on codebook space search is employed in a single cell transmission mode.
  • this CSI feedback based on codebook space search will continue to be used.
  • the PUCCH Physical Uplink Control CHannel
  • PUSCH Physical Uplink Shared CHannel
  • the PUCCH is configured for transmission of periodic, basic CSI with low payload; while PUSCH is configured for transmission of bursty, extended CSI with high payload.
  • a complete CSI is composed of various feedback contents which are transmitted in different sub-frames.
  • PUSCH on the other hand, a complete CSI is transmitted within one sub-frame.
  • the feedback contents can be divided into three categories: Channel Quality Index (CQI), Precoding Matrix Index (PMI) and Rank Index (RI), all of which are bit quantized feedbacks.
  • CQI typically corresponds to a transmission format having a packet error rate no more than 0.1.
  • Multi-user MIMO There are multiple UEs simultaneously participating in the downlink communication of the MIMO system on the same frequency.
  • Beam forming transmission The beam forming technique is employed in the MIMO system.
  • a dedicated reference signal is used for data demodulation at UE. Only one single layer of data is transmitted using the MIMO system.
  • the PMI feedback from UE is not required.
  • the UE can be configured to feed back PMI and RI, or not to feed back PMI and RI.
  • the above eight types of transmission approaches may be retained and/or cancelled.
  • a new type of transmission approach type 9 dynamic MIMO switching, can be added.
  • the BS can dynamically adjust the MIMO mode in which the UE operates.
  • Each MIMO transmission approach corresponds to a number of CSI feedback modes, as detailed in the following.
  • Type 1 one preferred sub-band location in a Band Part (BP, which is a subset of the set of communication spectrum resources S and has a size dependent on the size of the Set S) and a CQI for the sub-band.
  • the respective overheads are L bits for the sub-band location, 4 bits for the CQI of the first codeword and 3 bits for the CQI of the possible second codeword which is differentially coded with respect to the CQI of the first codeword.
  • Type 2 wideband CQI and PMI.
  • the respective overheads are 4 bits for the CQI of the first codeword, 3 bits for the CQI of the possible second codeword which is differentially coded with respect to the CQI of the first codeword and 1, 2 or 4 bits for PMI depending on the antenna configuration at BS.
  • Type 3 RI.
  • the overhead for RI is 1 bit for two antennas, or 2 bits for four antennas, depending on the antenna configuration at BS.
  • Type 4 wideband CQI.
  • the overhead is constantly 4 bits.
  • the UE feeds back different information to the BS in correspondence with the above different types.
  • the Mode 1-0 is a combination of Type 3 and Type 4. That is, the feedbacks of Type 3 and Type 4 are carried out at different periods and/or with different sub-frame offsets, which means that the wideband CQI of the first codeword in the Set S and possibly the RI information are fed back.
  • the Mode 1-1 is a combination of Type 3 and Type 2. That is, the feedbacks of Type 3 and Type 2 are carried out at different periods and/or with different sub-frame offsets, which means that the wideband PMI of the Set S, the wideband CQIs for the individual codewords and possibly the RI information are fed back.
  • the Mode 2-0 is a combination of Type 3, Type 4 and Type 1. That is, the feedbacks of Type 3, Type 4 and Type 1 are carried out at different periods and/or with different sub-frame offsets, which means that the wideband CQI of the first codeword in the Set S, possibly the RI information as well as one preferred sub-band location in the BP and the CQI for the sub-band are fed back.
  • the Mode 2-1 is a combination of Type 3, Type 2 and Type 1. That is, the feedbacks of Type 3, Type 2 and Type 1 are carried out at different periods and/or with different sub-frame offsets, which means that the wideband PMI of the Set S, the wideband CQIs for the individual codewords and possibly the RI information, as well as one preferred sub-band location in the BP and the CQI for the sub-band are fed back.
  • MIMO transmission approach 2 Mode 1-0 and Mode 2-0;
  • MIMO transmission approach 4 Mode 1-1 and Mode 2-1;
  • MIMO transmission approach 5 Mode 1-1 and Mode 2-1;
  • MIMO transmission approach 8 Mode 1-1 and Mode 2-1, with PMI/RI feedback from UE; or Mode 1-0 and Mode 2-0, without PMI/RI feedback from UE.
  • CQI, PMI and RI are primary feedback contents in the single BS transmission approach of the LTE-A system.
  • the Mode 1-1 and Mode 2-1 in the LTE-A system are optimized for a scenario where a BS is equipped with 8 transmission antennas. That is, a PMI is collectively determined from two channel precoding matrix indices W1 and W2, with W1 indicating wideband/long-term channel characteristics and W2 indicating sub-band/short-term channel characteristics.
  • Mode 1-1 is sub-divided into two sub-modes: Mode 1-1 (sub-mode 1) and Mode 1-1 (sub-mode 2). Also, the original Mode 2-1 is modified.
  • Type 1a one preferred sub-band location in a Band Part (BP, which is a subset of the set of communication spectrum resources S and has a size dependent on the size of the Set S) and a CQI for the sub-band, as well as a W2 for another sub-band.
  • the overhead for the sub-band location is L bits
  • Type 2a W1.
  • Type 2b wideband W2 and wideband CQI.
  • Type 2c wideband CQI, W1 and wideband W2.
  • Type 5 RI and W1.
  • the total overhead for the RI and the WI is 4 bits (in the case of 8 antennae and 2-layer data multiplexing) or 5 bits (in the case of 8 antennae and 4/8-layer data multiplexing).
  • the W1 takes values from an incomplete set (i.e., subset) of values, which is obtained by down-sampling all possible values of the W1.
  • Type 6 RI and Precoding Type Indicator (PTI).
  • the overhead for PTI is 1 bit, indicating the type of precoding.
  • the total overhead for the RI and the PTI is 2 bits (in the case of 8 antennae and 2-layer data multiplexing), 3 bits (in the case of 8 antennae and 3-layer data multiplexing), or 4 bits (in the case of 8 antennae and 8-layer data multiplexing).
  • W2 when used alone refers to “sub-band W2", while “wideband W2” is referred to by their full expressions.
  • Mode 1-1 (sub-mode 1) is a combination of Type 5 and Type 2b. That is, the feedbacks of Type 5 and Type 2b are carried out at different periods and/or with different sub-frame offsets.
  • Mode 1-1 (sub-mode 2) is a combination of Type 3 and Type 2/2c
  • the Mode 1-1 (sub-mode 2) is composed of Type 3 and Type 2. That is, the feedbacks of Type 3 and Type 2 are carried out at different periods and/or with different sub-frame offsets.
  • the Mode 1-1 (sub-mode 2) is composed of Type 3 and Type 2c. That is, the feedbacks of Type 3 and Type 2c are carried out at different periods and/or with different sub-frame offsets.
  • the new Mode 2-1 is specific to the MIMO transmission approach of type 9), and is a combination of Type 6, Type 2b and Type 2a/1a,
  • the new Mode 2-1 is composed of Type 6, Type 2b and Type 2a. That is, the feedbacks of Type 6, Type 2b and Type 2a are carried out at different periods and/or with different sub-frame offsets.
  • the new Mode 2-1 is composed of Type 6, Type 2b and Type 1a. That is, the feedbacks of Type 6, Type 2b and Type 1a are carried out at different periods and/or with different sub-frame offsets.
  • Non Patent Literature 4 The minutes of the 3GPP TSG-RAN WG1 meeting #63bis held in Dublin, Ireland in January 2011.
  • the general concept is that the feedback contents involve CSI based on codebook space search, such as CQI, PMI and RI, and the information feedback is mainly carried out separately to each BS and is assisted with transmission of CSI (such as phase information) between BSs.
  • codebook space search such as CQI, PMI and RI
  • the information feedback is mainly carried out separately to each BS and is assisted with transmission of CSI (such as phase information) between BSs.
  • schemes such as JT, DPS, CS/CB, can be dynamically supported in a unified CSI feedback framework, according to Non Patent Literature 5:
  • BSs are typically required to have the same RI, so that precoded data of the BSs can be phase weighted and then added up.
  • a cooperating TP does not have an independent RI but uses the same RI as a serving TP
  • BSs are typically required to have independent RIs, so that CSI for each BS can be fed back to the BS more accurately.
  • each TP has an independent RI (see Non Patent Literature 7: 3GPP, R1-113728, "CSI feedback to support CoMP transmission” proposed at TSG-RAN WG1 meeting #67, CATT).
  • NPL 1 3GPP, TR 36.814 V9.0.0 (2010-03), "Further advancements for E-UTRA physical layer aspects (Release 9)”.
  • NPL 2 3GPP R1-093720, "CoMP email summary", Qualcomm.
  • NPL 3 3GPP, R1-083546, "Per-cell precoding methods for downlink joint processing CoMP", ETRI.
  • NPL 4 The minutes of the 3GPP TSG-RAN WG1 meeting #63bis held in Dublin, Ireland in January 2011.
  • NPL 5 The minutes of the 3GPP TSG-RAN WG1 meeting #66bis held in Zhuhai, China in October 2011.
  • NPL 6 3GPP, R1-114258, "CSI Feedback for DL CoMP” proposed at TSG-RAN WG1 meeting #67, Ericsson.
  • NPL 7 3GPP, R1-113728, "CSI feedback to support CoMP transmission” proposed at TSG-RAN WG1 meeting #67, CATT.
  • NPL 8 3GPP, R1-092427, "CSI-RS Design for Virtualized LTE Antenna in LTE-A System", Fujitsu.
  • a User Equipment which comprises: a Transmission Point (TP) set acquiring unit configured to acquire a set of TPs from a serving Base Station (BS); a channel Rank Index (RI) determining unit configured to determine an RI for Joint Transmission (JT); a sub channel Precoding Matrix Index (sub-PMI) determining unit configured to determine a sub-PMI for the JT; and a Channel State Information (CSI) feedback unit configured to feed back CSI to the serving BS, wherein if the serving BS determines the RI for the JT and/or the sub-PMI for the JT based on feedback, the CSI fed back by the CSI feedback unit contains the RI for the JT determined by the RI determining unit and/or the sub-PMI for the JT determined by the sub-PMI determining unit.
  • TP Transmission Point
  • RI Rank Index
  • JT Joint Transmission
  • sub-PMI sub channel Precoding Matrix Index
  • CSI Channel State Information
  • the set of TPs are determined by the serving BS, and semi-statically configured to the UE via Radio Resource Control (RRC) signalings or Media Access Control (MAC) layer signalings.
  • RRC Radio Resource Control
  • MAC Media Access Control
  • the first TP in the set of TPs is a serving TP.
  • the set of TPs contains a serving TP corresponding to the serving BS.
  • the UE according to the first aspect of the present invention further comprises a TP selecting unit configured to select a cooperating TP from the set of TPs, and wherein the CSI fed back by the CSI feedback unit contains index information identifying the selected cooperating TP.
  • the CSI feedback unit feeds back the CSI containing a Point Selection Index (PSI) to the serving BS in a periodic feedback manner.
  • PSI Point Selection Index
  • the PSI has a number of bits fitted to a size of the set of TPs, such that the PSI is adequate to indicate the cooperating TP selected by TP selecting unit from the set of TPs, and wherein in an LTE-A system, if the selected cooperating TP has an independent RI, the PSI is fed back by defining feedback of the PSI as a new type of feedback whose feedback period is an integer multiple of a feedback period of a feedback Type 5 and whose feedback time slot offset is the same as that of the feedback Type 5, defining the feedback of the PSI as a new type of feedback whose feedback period is an integer multiple of a feedback period of a feedback Type 3 and whose feedback time slot offset is the same as that of the feedback Type 3, or defining the feedback of the PSI as a new type of feedback whose feedback period is an integer multiple of a feedback period of a feedback Type 6 and whose feedback time slot offset is the same as that of the feedback Type 6.
  • the PSI has a number of bits fitted to a size of the set of TPs, such that the PSI is adequate to indicate the cooperating TP selected by TP selecting unit from the set of TPs, and wherein in an LTE-A system, if the selected cooperating TP does not has an independent RI, the PSI is fed back by replacing an RI of an former feedback type 5 with the PSI, replacing an RI of an former feedback type 3 with the PSI, or replacing an RI of an former feedback type 6 with the PSI.
  • the serving BS does not determine the RI for the JT based on feedback, and wherein when a cooperating TP has an independent RI, the serving BS determines the largest one of all TPs' RIs as the RI for the JT.
  • the serving BS does not determine the RI for the JT based on feedback, and wherein when a cooperating TP does have an independent RI, the serving BS determines an RI of a serving TP as the RI for the JT.
  • the serving BS determines the RI for the JT based on feedback, and wherein in an LTE-A system, the RI for the JT determined by the RI determining unit is fed back in a format according to a feedback Type 5, a feedback Type 3 or a feedback Type 6.
  • the serving BS does not determine the sub-PMI for the JT based on feedback, and wherein if an RI of a TP (L TP ) is larger than the RI for the JT (L JT ), at the serving BS, a sub-precoding matrix for the JT is one of the following: a matrix obtained by deleting the first L TP -L JT column vectors of a precoding matrix of the TP, a matrix obtained by deleting the last L TP -L JT column vectors of a precoding matrix of the TP, or in a case where a codebook of the precoding matrix is in a form of a two-dimension table with one dimension representing RI and the other dimension representing PMI, a codeword obtained by looking up the two-dimension table based on a PMI of the TP and the RI for the JT.
  • the serving BS does not determine the sub-PMI for the JT based on feedback, and wherein if an RI of a TP (L TP ) is smaller than the RI for the JT (L JT ), at the serving BS, a sub-precoding matrix for the JT is one of the following: in a case where a codebook of a precoding matrix of is in a form of a two-dimension table with one dimension representing RI and the other dimension representing PMI, a codeword obtained by looking up the two-dimension table based on a PMI of the TP and the RI for the JT, a matrix obtained by multiplying the precoding matrix of the TP by predefined matrix, or a matrix obtained by performing nonlinear transformation on the precoding matrix of the TP with a predefined nonlinear function.
  • the serving BS determines the sub-PMI for the JT based on feedback, and wherein if an RI of a TP (L TP ) is larger than the RI for the JT (L JT ), the fed back sub-PMI is used to identify: which column vectors are selected from a precoding matrix of the TP to generate a sub-precoding matrix for the JT, or among methods pre-configured to the UE via RRC signalings or configured to the UE statically, which one is used to generate the sub-precoding matrix for the JT based on the precoding matrix of the TP.
  • the serving BS determines the sub-PMI for the JT based on feedback, and wherein if an RI of a TP (L TP ) is smaller than the RI for the JT (L JT ), the sub-PMI for the JT determined by the sub-PMI determining unit is used to identify: among candidate matrices pre-configured to the UE via RRC signalings or configured to the UE statically, which one is multiplied by a precoding matrix of the TP to generate a sub-precoding matrix for the JT, or a value to be determined for a parameter of a nonlinear function, the nonlinear function being used to perform nonlinear transformation on the precoding matrix of the TP to generate the sub-precoding matrix for the JT.
  • a CSI feedback method comprises: acquiring a set of TPs from a serving BS; determining an RI for JT; determining a sub-PMI for the JT; and feeding back CSI to the serving BS, wherein if the serving BS determines the RI for the JT and/or the sub-PMI for the JT based on feedback, the fed back CSI contains the determined RI for the JT and/or the determined sub-PMI for the JT.
  • the sixth aspect of the present invention further comprises selecting a cooperating TP from the set of TPs, and wherein the fed back CSI contains index information identifying the selected cooperating TP.
  • the CSI feedback method and user equipment according to the present invention have the advantages of dynamically supporting JT and DCS transmission, simple implementation and low signalling overhead.
  • Fig. 1 is a schematic diagram of a MIMO system.
  • Fig. 2 is a schematic diagram of complete CSI feedback.
  • Fig. 3 is a schematic diagram of statistic-based CSI feedback.
  • Fig. 4 is a schematic diagram of CSI feedback based on codebook space search.
  • Fig. 5 is a schematic diagram of a multi-cell cellular communication system.
  • Fig. 6 is a flowchart illustrating a CSI feedback method according to the present invention.
  • Fig. 7 is a schematic block diagram of a UE according to the present invention.
  • Fig. 8 is a schematic diagram illustrating example 1 of periodic feedback.
  • Fig. 9 is a schematic diagram illustrating example 2 of the periodic feedback.
  • Fig. 10 is a schematic diagram illustrating example 3 of the periodic feedback.
  • serving BS refers to a BS which can transmit control signalings directly to a MS.
  • serving BS refers to a BS which can transmit control signalings directly to a MS.
  • the term “cooperating BS” is used in a manner different from that familiar to those skilled in the art. Specifically, although those skilled in the art commonly use the term to refer to all BSs participating in coordination transmission, the term “cooperating BS” used herein refers in particular to other BSs participating in the coordination transmission than the serving BS.
  • cooperating BS set refers to a set of such "cooperating BSs". Obviously, there is no “serving BS” included in the cooperating BS set. Moreover, as described in the background with respect to the concept of "TP”, “serving BS” and “cooperating BS” shall be interpreted as “serving TP” and “cooperating TP” extendedly, rather than as a single BS infrastructure conventionally.
  • TP refers to a set of a plurality of transmission ports corresponding to a downlink Reference Signal pattern (CSI-RS Pattern).
  • Fig. 5 is a schematic diagram of a multi-cell cellular communication system.
  • the cellular system divides a service coverage area into a number of adjacent wireless coverage areas, i.e., cells.
  • the entire service area is formed by cells 100, 102 and 104, each being illustratively shown as a hexagon.
  • Base Stations (BSs) 200, 202 and 204 are associated with the cells 100, 102 and 104, respectively.
  • each of the BSs 200-204 includes at least a transmitter and a receiver.
  • a BS which is generally a serving node in a cell
  • each of the BSs 200-204 is located in a particular area of the corresponding one of the cells 100-104 and is equipped with an omni-directional antenna.
  • each of the BSs 200-204 can also be equipped with a directional antenna for directionally covering a partial area of the corresponding one of the cells 100-104, which is commonly referred to as a sector.
  • a directional antenna for directionally covering a partial area of the corresponding one of the cells 100-104, which is commonly referred to as a sector.
  • the BSs 200, 202 and 204 are connected with each other via X2 interfaces 300, 302 and 304.
  • a three-layer node network architecture including base station, radio network control unit and core network is simplified into a two-layer node architecture in which the function of the radio network control unit is assigned to the base station and a wired interface named "X2" is defined for coordination and communication between base stations.
  • the BSs 200, 202 and 204 are also connected with each other via air interfaces, A1 interfaces, 310, 312 and 314.
  • A1 interfaces A1 interfaces
  • Relay nodes are connected with each other via wireless interfaces and a base station can be considered as a special relay node.
  • a wireless interface named "A1" can then be used for coordination and communication between base stations.
  • an upper layer entity 220 of the BSs 200, 202 and 204 is also shown in Fig. 5, which can be a gateway or another network entity such as mobility management entity.
  • the upper layer entity 220 is connected to the BSs 200, 202 and 204 via S1 interfaces 320, 322 and 324, respectively.
  • S1 a wired interface named "S1" is defined for coordination and communication between the upper layer entity and the base station.
  • a number of User Equipments (UEs) 400, 402 ... 430 are distributed over the cells 100, 102 and 104, as shown in Fig. 5.
  • each of the UEs 400-430 includes a transmitter, a receiver and a mobile terminal control unit.
  • Each of the UEs can access the cellular communication system via its serving BS (one of the BSs 200, 202 and 204). It should be understood that while only 16 UEs are illustratively shown in Fig. 5, there may be a large number of UEs in practice. In this sense, the description of the UEs in Fig. 5 is also for illustrative purpose only.
  • Each of the UEs can access the cellular communication network via its serving BS.
  • the BS transmitting control signalings directly to a certain UE is referred to as the serving BS for that UE, while other BSs are referred to non-serving BSs for that UE.
  • the non-serving BSs can function as cooperating BSs which cooperate with the serving BS to provide communication service to the UE.
  • the UE 416 is considered.
  • the UE 416 operates in a multi-BS coordination mode, has BS 202 as its serving BS and has BSs 200 and 204 as its cooperating BSs. It is to be noted that, although focus is placed on the UE 416, this does not imply that the present invention is only applicable to one UE scenario. Rather, the present invention works well for multi-UE scenario.
  • the inventive method can be applied to the UEs 408, 410, 430 and the like as shown in Fig. 5.
  • the UE 416 operating in a multi-BS coordination mode has BS 202 as its serving BS, and has BSs 200 and 204 as its cooperating BSs (non-serving BSs).
  • each of the BS 200 and the BS 202 is equipped with 8 transmitting antennae and uses 8 transmission ports
  • the BS 204 is equipped with 4 transmitting antennae and uses 4 transmission ports.
  • the UE 416 can be a single-antenna or multi-antenna device.
  • any other UE e.g., any one of UEs 400-430
  • the transmitting antennae and the transmission ports of a BS are not necessarily in one-to-one correspondence, although typically the number of the BS's transmitting antennae is equal to the number of transmission ports.
  • a plurality of transmitting antennae of a BS can be mapped to a single transmission port by combining the plurality of transmitting antennae in a weighted manner (see Non Patent Literature 8: 3GPP, R1-092427, "CSI-RS Design for Virtualized LTE Antenna in LTE-A System", Fujitsu).
  • the CSI feedback method 600 begins with step S601.
  • step S601 a UE acquires a set of TPs participating in multi-antenna multi-BS coordination from a serving BS.
  • the UE may periodically report to the serving BS (e.g., serving BS 202) path loss information of paths from the UE to its adjacent BSs.
  • the serving BS can estimate the geographic location of the UE from the report, determine the set of TPs participating in the multi-antenna multi-BS coordination based on the estimated geographic location, and semi-statically configure the set of TPs for the UE via upper layer signalings, such as Radio Resource Control (RRC) signalings, or Media Acccess Control (MAC) layer signalings.
  • RRC Radio Resource Control
  • MAC Media Acccess Control
  • the TP set includes 2 to 8 TPs, respectively.
  • the TP set which the serving BS 202 configures for the UE 416 includes 2 TPs, so that the UE 416 can use 1 bit to feed back the result of choosing one from two opinions.
  • the 2 TPs may include: 1) a TP composed of a total of 8 ports, including ports 0 to 7 of the BS 202; and 2) a TP composed of a total of 8 ports, including ports 0 to 3 of the BS 202, ports 0 and 1 of the BS 200, and ports 2 and 3 of the BS 204.
  • the TP set which the serving BS 202 configures for the UE 416 includes 3 TPs, so that the UE 416 can use 2 bit to feed back the result of choosing one from three opinions.
  • the 3 TPs may include: 1) a TP composed of a total of 8 ports, including ports 0 to 7 of the BS 202; 2) a TP composed of a total of 8 ports, including ports 0 to 3 of the BS 202, ports 0 and 1 of the BS 200, and ports 2 and 3 of the BS 204; and 3) a TP composed of a total of 8 ports, including ports 0 to 3 of the BS 202, ports 3 and 4 of the BS 200, and ports 0 and 1 of the BS 204.
  • the TP set which the serving BS 202 configures for the UE 416 includes 4 TPs, so that the UE 416 can use 2 bit to feed back the result of choosing one from four opinions.
  • the 4 TPs may include: 1) a TP composed of a total of 8 ports, including ports 0 to 7 of the BS 202; 2) a TP composed of a total of 8 ports, including ports 0 to 3 of the BS 202, ports 0 and 1 of the BS 200, and ports 2 and 3 of the BS 204; 3) a TP composed of a total of 8 ports, including ports 0 to 3 of the BS 202, ports 3 and 4 of the BS 200, and ports 0 and 1 of the BS 204; and 4) a TP composed of a total of 4 ports, including ports 0 to 3 of the BS 204.
  • the UE chooses the fourth TP, the UE chooses the entire BS 204 equivalently. That is, the DPS transmission approach is implemented.
  • a TP corresponding to the DPS transmission may be involved in all illustrative configurations of the set of TPs participating in the multi-antenna multi-BS coordination.
  • the TP set which the serving BS 202 configures for the UE 416 includes 5 TPs, so that the UE 416 can use 3 bit to feed back the result of choosing one from five opinions.
  • the 5 TPs may include: 1) a TP composed of a total of 8 ports, including ports 0 to 7 of the BS 202; 2) a TP composed of a total of 8 ports, including ports 0 to 3 of the BS 202, ports 0 and 1 of the BS 200, and ports 2 and 3 of the BS 204; 3) a TP composed of a total of 8 ports, including ports 0 to 3 of the BS 202, ports 3 and 4 of the BS 200, and ports 0 and 1 of the BS 204; 4) a TP composed of a total of 4 ports, including ports 0 to 3 of the BS 204; and 5) a TP composed of a total of 4 ports, including ports 4 to 7 of the BS 200.
  • the number of ports of the fourth and fifth TPs may be different from that of the first three TPs, because different TPs have configurations independent of each other.
  • such TPs having different numbers of ports may be involved in all illustrative configurations of the set of APs participating in the multi-antenna multi-BS coordination.
  • the TP set which the serving BS 202 configures for the UE 416 includes 6 TPs, so that the UE 416 can use 3 bit to feed back the result of choosing one from six opinions.
  • the 6 TPs may include: 1) a TP composed of a total of 8 ports, including ports 0 to 7 of the BS 202; 2) a TP composed of a total of 8 ports, including ports 0 to 3 of the BS 202, ports 0 and 1 of the BS 200, and ports 2 and 3 of the BS 204; 3) a TP composed of a total of 8 ports, including ports 0 to 3 of the BS 202, ports 3 and 4 of the BS 200, and ports 0 and 1 of the BS 204; 4) a TP composed of a total of 4 ports, including ports 0 to 3 of the BS 204; 5) a TP composed of a total of 4 ports, including ports 4 to 7 of the BS 200; and 6) a TP composed of a total of 6
  • the sixth TP is composed of all ports of the BS 204 as well as part (or all) of the ports of another BS. This corresponds to the JT transmission approach.
  • a TP may be involved in all illustrative configurations of the set of APs participating in the multi-antenna multi-BS coordination.
  • the TP set which the serving BS 202 configures for the UE 416 includes 7 TPs, so that the UE 416 can use 3 bit to feed back the result of choosing one from seven opinions.
  • the 7 TPs may include: 1) a TP composed of a total of 8 ports, including ports 0 to 7 of the BS 202; 2) a TP composed of a total of 8 ports, including ports 0 to 3 of the BS 202, ports 0 and 1 of the BS 200, and ports 2 and 3 of the BS 204; 3) a TP composed of a total of 8 ports, including ports 0 to 3 of the BS 202, ports 3 and 4 of the BS 200, and ports 0 and 1 of the BS 204; 4) a TP composed of a total of 4 ports, including ports 0 to 3 of the BS 204; 5) a TP composed of a total of 4 ports, including ports 4 to 7 of the BS 200; 6) a TP composed of a total of 6 ports
  • the TP set which the serving BS 202 configures for the UE 416 includes 8 TPs, so that the UE 416 can use 3 bit to feed back the result of choosing one from eight opinions.
  • the 8 TPs may include: 1) a TP composed of a total of 8 ports, including ports 0 to 7 of the BS 202; 2) a TP composed of a total of 8 ports, including ports 0 to 3 of the BS 202, ports 0 and 1 of the BS 200, and ports 2 and 3 of the BS 204; 3) a TP composed of a total of 8 ports, including ports 0 to 3 of the BS 202, ports 3 and 4 of the BS 200, and ports 0 and 1 of the BS 204; 4) a TP composed of a total of 4 ports, including ports 0 to 3 of the BS 204; 5) a TP composed of a total of 4 ports, including ports 4 to 7 of the BS 200; 6) a TP composed of a total of 6 ports
  • the first TP is a TP composed of a total of 8 ports, including ports 0 to 7 of the BS 202. This is because the serving BS typically acts as a TP participating in multi-BS coordination. Of course, it is not necessary to have such a limitation.
  • the first TP in the set of TPs participating in the multi-antenna multi-BS coordination is a serving TP, which preferably corresponds to the serving BS.
  • step S602 the UE selects a TP from the set of TPs. If step S602 is executed, the UE feeds back CSI containing TP index information to the serving BS for identifying the TP selected at step S602. For the sake of coherence, description will be given on how to feed back the TP index information (i.e, part of step S605 in Fig .6).
  • Example 1 where the serving BS 202 configures the feedback mode of the UE 416 as Mode 1-1 (sub-mode 1) and each TP has an independent RI.
  • a new type (type 7) of feedback containing dynamic TP selection information referred to as Point Selection Index (PSI)
  • PSI Point Selection Index
  • the PSI uses 1, 2 or 3 bits to indicate the TP selected by the UE from the set of TPs.
  • the feedback period of type 7 is an integer multiple of the feedback period of Type 5, and the time slot offset of type 7 is the same as that of Type 5.
  • the technical principle behind such a design is that: among all CSI information of Mode 1-1 (sub-mode 1), the dynamic TP selection information changes most slowly, and thus shall has the longest feed period.
  • TTI Transmission Time Interval
  • the feedback of type 7 is carried out while the feedback of type 5 is not carried out.
  • Example 1 of the periodic feedback is illustratively shown in Fig. 8.
  • Example 2 where the serving BS 202 configures the feedback mode of the UE 416 as Mode 1-1 (sub-mode 2) and each TP has an independent RI.
  • a new type (type 7) of feedback containing PSI is defined for the CSI information feeding back the selected TP.
  • the PSI uses 1, 2 or 3 bits to indicate the TP selected by the UE from the set of TPs.
  • the feedback period of type 7 is an integer multiple of the feedback period of Type 3, and the time slot offset of type 7 is the same as that of Type 3.
  • the technical principle behind such a design is that: among all CSI information of Mode 1-1 (sub-mode 2), the dynamic TP selection information changes most slowly, and thus shall has the longest feed period. When there is a conflict between type 7 and Type 3, the feedback of type 7 is carried out while the feedback of Type 3 is not carried out.
  • Example 2 of the periodic feedback is illustratively shown in Fig. 9.
  • Example 3 where the serving BS 202 configures the feedback mode of the UE 416 as Mode 2-1 and each TP has an independent RI.
  • a new type (type 7) of feedback containing PSI is defined for the CSI information feeding back the selected TP.
  • the PSI uses 1, 2 or 3 bits to indicate the TP selected by the UE from the set of TPs.
  • the feedback period of type 7 is an integer multiple of the feedback period of Type 6, and the time slot offset of type 7 is the same as that of Type 6.
  • the technical principle behind such a design is that: among all CSI information of Mode 2-1, the dynamic TP selection information changes most slowly, and thus shall has the longest feed period. When there is a conflict between type 7 and Type 6, the feedback of type 7 is carried out while the feedback of Type 6 is not carried out.
  • Example 3 of the periodic feedback is illustratively shown in Fig. 10.
  • the serving TP has an RI and the cooperating TP does not have an independent RI
  • Example 1 where the serving BS 202 configures the feedback mode of the UE 416 as Mode 1-1 (sub-mode 1), the serving TP has an RI, and the cooperating TP does not have an independent RI.
  • PSI Point Selection Index
  • the PSI uses 1, 2 or 3 bits to indicate the TP selected by the UE from the set of TPs.
  • the PSI is fed back by replacing the RI of type 5 to form a new type 5 wherein the PSI and the W1 are jointly coded.
  • the technical principle behind such a design is that: the PSI can be fed back in a format similar to that of type 5, because RI needs not to be fed back to the serving TP and the payload of PSI is similar to that of RI.
  • Example 2 where the serving BS 202 configures the feedback mode of the UE 416 as Mode 1-1 (sub-mode 2), the serving TP has an RI, and the cooperating TP does not have an independent RI.
  • PSI Point Selection Index
  • the PSI uses 1, 2 or 3 bits to indicate the TP selected by the UE from the set of TPs.
  • the PSI is fed back by replacing the RI of type 3 to form a new type 3.
  • the technical principle behind such a design is that: the PSI can be fed back in a format similar to that of type 3, because RI needs not to be fed back to the serving TP and the payload of PSI is similar to that of RI.
  • Example 3 where the serving BS 202 configures the feedback mode of the UE 416 as a new Mode 2-1, the serving TP has an RI, and the cooperating TP does not have an independent RI.
  • PSI Point Selection Index
  • the PSI uses 1, 2 or 3 bits to indicate the TP selected by the UE from the set of TPs.
  • the PSI is fed back by replacing the RI of type 6 to form a new type 5 wherein the PSI and the PTI are jointly coded.
  • the technical principle behind such a design is that: the PSI can be fed back in a format similar to that of type 6, because RI needs not to be fed back to the serving TP and the payload of PSI is similar to that of RI.
  • step S603 the UE determines an RI for the JT.
  • Specific implementations include but not limited to the following prior art approaches: (1) calculating RIs of individual TPs, and then determining the RI for the JT by performing mathematical operations on the RIs of TPs (for example, determining the maximum, the minimum, or the average of all TPs' RIs as the RI for the JT); or (2) determining the equivalent channel for the JT, and then calculating the RI for the JT directly based on the determined equivalent channel for the JT.
  • the serving BS 202 determines the RI for the JT in the following manners.
  • the RI for the JT is the largest one of all TPs' RIs.
  • the serving BS 202 may derive the RI for the JT from TPs' RIs and the UE needs not to feed back the RI for the JT.
  • the technical principle behind such a design is that: the channel for the JT is formed by individual TPs' sub-channels which are less correlated, and therefore the RI for the JT tends to be large.
  • the RI for the JT is equal to the RI of the serving TP.
  • the serving BS 202 may derive the RI for the JT from the RI of the serving TP and the UE needs not to feed back the RI for the JT.
  • the technical principle behind such a design is that: the serving TP's CSI is usually of a good quality, and therefore its RI may be used to reduce feedback overhead and achieve a relatively good performance.
  • the UE When the UE needs to feed back the RI for the JT to the serving BS 202, the UE feeds back the determined RI for the JT to the serving BS. For the sake of coherence, description will be given on how to feed back the RI for the JT (i.e, part of step S605 in Fig .6).
  • Example 1 where, for the JT operation with respect to the UE 416, there is additionally added an aggregation feedback mode (reflecting the effect of multi-TP joint transmission) which is configured by the serving BS 202 as Mode 1-1 (sub-mode 1).
  • an aggregation feedback mode (reflecting the effect of multi-TP joint transmission) which is configured by the serving BS 202 as Mode 1-1 (sub-mode 1).
  • the RI for the JT is fed back in a format according to type 5.
  • the technical principle behind such a design is that: the JT operation may be regarded as a technical effect brought about by a virtual TP, for which feedback may be performed in a manner similar to that employed for an ordinary TP, and the RI for the JT may therefore be fed back in a format similar to that of type 5.
  • Example 2 where, for the JT operation with respect to the UE 416, there is additionally added an aggregation feedback mode (reflecting the effect of multi-TP joint transmission) which is configured by the serving BS 202 as Mode 1-1 (sub-mode 2).
  • an aggregation feedback mode (reflecting the effect of multi-TP joint transmission) which is configured by the serving BS 202 as Mode 1-1 (sub-mode 2).
  • the RI for the JT is fed back in a format according to type 3.
  • the technical principle behind such a design is that: the JT operation may be regarded as a technical effect brought about by a virtual TP, for which feedback may be performed in a manner similar to that employed for an ordinary TP, and the RI for the JT may therefore be fed back in a format similar to that of type 3.
  • Example 3 where, for the JT operation with respect to the UE 416, there is additionally added an aggregation feedback mode (reflecting the effect of multi-TP joint transmission) which is configured by the serving BS 202 as Mode 2-1.
  • the RI for the JT is fed back in a format according to type 6.
  • the technical principle behind such a design is that: the JT operation may be regarded as a technical effect brought about by a virtual TP, for which feedback may be performed in a manner similar to that employed for an ordinary TP, and the RI for the JT may therefore be fed back in a format similar to that of type 6.
  • step S604 the UE determines sub-PMIs for the JT.
  • sub-PMIs refers to individual PMIs of the TPs participating in the JT.
  • the TP's PMI can be certainly used as the sub-PMI for the JT.
  • the number of columns of the TP's PMI i.e., the TP's RI
  • the RI for the JT the number of columns of the sub-PMI for the JT
  • the RI for the JT the number of columns of the sub-PMI for the JT
  • Example 1 where the precoding matrix corresponding to the PMI of the cooperating BS 204 is assumed to be
  • f i denotes a column vector of the matrix F 204
  • L 204 denotes the RI of the cooperating BS 204
  • the cooperating BS 204 is assumed to be a TP, and the RI of the cooperating BS 204, L 204 , is larger than the RI for the JT, L JT ;
  • the first (L 204 -L JT ) column vectors of F 204 are deleted so as to generate the desired
  • the UE needs not to feed back the sub-PMI for the JT.
  • F 204 would be a 4*3 matrix.
  • a 4*2 matrix can be obtained as
  • Example 2 where the precoding matrix corresponding to the PMI of the cooperating BS 204 is assumed to be
  • f i denotes a column vector of the matrix F 204
  • L 204 denotes the RI of the cooperating BS 204
  • the cooperating BS 204 is assumed to be a TP, and the RI of the cooperating BS 204, L 204 , is larger than the RI for the JT, L JT ;
  • the last (L 204 -L JT ) column vectors of F 204 are deleted so as to generate the desired
  • the UE needs not to feed back the sub-PMI for the JT.
  • F 204 would be a 4*3 matrix.
  • a 4*2 matrix can be obtained as
  • Example 3 where the precoding matrix corresponding to the PMI of the cooperating BS 204 is assumed to be
  • f i denotes a column vector of the matrix F 204
  • L 204 denotes the RI of the cooperating BS 204
  • the cooperating BS 204 is assumed to be a TP, and the RI of the cooperating BS 204, L 204 , is larger than the RI for the JT, L JT ;
  • the codebook of the precoding matrix is in a form of a simple two-dimension table wherein the Number of Layers along the horizontal axis denotes RI and the Codebook index along the vertical axis denotes PMI
  • the codeword corresponding to the PMI of F 204 and the RI may be taken as
  • Example 4 where the precoding matrix corresponding to the PMI of the cooperating BS 204 is assumed to be
  • f i denotes a column vector of the matrix F 204
  • L 204 denotes the RI of the cooperating BS 204
  • the cooperating BS 204 is assumed to be a TP, and the RI of the cooperating BS 204, L 204 , is larger than the RI for the JT, L JT ;
  • L JT column vectors are selected from F 204 to generate the desired
  • the UE needs to feed back selection information, identifying which column vectors are selected from F 204 as the column vectors of
  • F 204 would be a 4*3 matrix.
  • a 4*2 matrix can be obtained as
  • Example 5 where the precoding matrix corresponding to the PMI of the cooperating BS 204 is assumed to be
  • f i denotes a column vector of the matrix F 204
  • L 204 denotes the RI of the cooperating BS 204
  • the cooperating BS 204 is assumed to be a TP, and the RI of the cooperating BS 204, L 204 , is larger than the RI for the JT, L JT ;
  • F 204 are pre-configured via RRC signalings or statically defined, and the UE feeds back the index number of the method as the sub-PMI of the JT.
  • the methods known in advance are determinate and unambiguous methods, such as
  • F 204 would be a 4*3 matrix.
  • taking the second and third columns of F 204 and taking the first and second columns of F 204 are pre-figured via RRC signalings or statically defined as candidate methods for generating
  • the UE only needs to use one bit to inform the serving BS 202 as to which method is used to obtain
  • Example 1 where the precoding matrix corresponding to the PMI of the cooperating BS 204 is assumed to be
  • f i denotes a column vector of the matrix F 204
  • L 204 denotes the RI of the cooperating BS 204
  • the cooperating BS 204 is assumed to be a TP, and the RI of the cooperating BS 204, L 204 , is smaller than the RI for the JT, L JT ;
  • the codebook of the precoding matrix is in a form of a simple two-dimension table wherein RI is denoted along the horizontal axis and PMI is denoted along the vertical axis
  • the codeword corresponding to the PMI of F 204 and the RI (L JT ) may be taken as
  • Example 2 where the precoding matrix corresponding to the PMI of the cooperating BS 204 is assumed to be
  • f i denotes a column vector of the matrix F 204
  • L 204 denotes the RI of the cooperating BS 204
  • the cooperating BS 204 is assumed to be a TP, and the RI of the cooperating BS 204, L 204 , is smaller than the RI for the JT, L JT ;
  • the matrix A is a predefined complex matrix.
  • the UE needs not to feed back the matrix A to the serving BS 202.
  • F 204 would be a 4*2 matrix
  • Example 3 where the precoding matrix corresponding to the PMI of the cooperating BS 204 is assumed to be
  • f i denotes a column vector of the matrix F 204
  • L 204 denotes the RI of the cooperating BS 204
  • the cooperating BS 204 is assumed to be a TP, and the RI of the cooperating BS 204, L 204 , is smaller than the RI for the JT, L JT ;
  • the matrix A is selected from a number of complex matrices that are pre-configured via RRC signalings or statically defined.
  • the UE needs to feed back the index number of the matrix A to the serving BS 202.
  • F 204 would be a 4*2 matrix
  • the UE only needs to use one bit to inform the serving BS 202 as to which matrix is used as the matrix A to calculate
  • Example 4 where the precoding matrix corresponding to the PMI of the cooperating BS 204 is assumed to be
  • f i denotes a column vector of the matrix F 204
  • L 204 denotes the RI of the cooperating BS 204
  • the cooperating BS 204 is assumed to be a TP, and the RI of the cooperating BS 204, L 204 , is smaller than the RI for the JT, L JT ;
  • the UE needs to feed back
  • F 204 would be a 4*2 matrix
  • Example 5 where the precoding matrix corresponding to the PMI of the cooperating BS 204 is assumed to be
  • f i denotes a column vector of the matrix F 204
  • L 204 denotes the RI of the cooperating BS 204
  • the cooperating BS 204 is assumed to be a TP, and the RI of the cooperating BS 204, L 204 , is smaller than the RI for the JT, L JT ;
  • F 204 would be a 4*2 matrix
  • the UE needs to use a number of bits to inform the serving BS 202 of the specific values of
  • step S605 the UE feeds back the CSI to the serving BS.
  • the UE needs to feed back the sub-PMI for the JT to the serving BS 202 as described with respect to step S604, the UE feeds back the determined sub-PMI for the JT to the serving BS at step S605.
  • a UE 700 enabling the implementation of the above CSI feedback methods is also provided.
  • Fig. 7 is a schematic block diagram of the UE 700 according to the present invention.
  • the UE 700 comprises: a TP set acquiring unit 710 configured to acquire a set of TPs from a serving BS; a channel RI determining unit 720 configured to determine an RI for JT; a sub-PMI determining unit 730 configured to determine a sub-PMI for the JT; and a CSI feedback unit 740 configured to feed back CSI to the serving BS.
  • the UE 700 may further comprise a TP selecting unit 750 configured to select a cooperating TP from the set of TPs.
  • the solution of the present invention has been described above by a way of example only.
  • the present invention is not limited to the above steps and element structures. It is possible to adjust, add and remove the steps and elements structures depending on actual requirements. Thus, some of the steps and elements are not essential for achieving the general inventive concept of the present invention. Therefore, the features necessary for the present invention is only limited to a minimum requirement for achieving the general inventive concept of the present invention, rather than the above specific examples.

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Abstract

La présente invention se rapporte à un procédé de rétroaction de données d'état de canal (CSI) et à un équipement d'utilisateur (UE). Le procédé de rétroaction de CSI selon l'invention consiste : à acquérir un ensemble de points de transmission (TP), d'une station de base de desserte (BS) ; à déterminer un indice de rang (RI) pour une transmission conjointe (JT) ; à déterminer un indice de matrice de précodage de sous-canal (PMI de sous-canal) pour la JT ; et à retourner les CSI à la BS de desserte. Si la BS de desserte détermine le RI pour la JT et/ou le PMI de sous-canal pour la JT sur la base de la rétroaction, les CSI retournées contiennent le RI déterminé pour la JT et/ou le PMI de sous-canal déterminé pour la JT.
PCT/JP2012/008428 2011-12-29 2012-12-28 Procédé de rétroaction de données d'état de canal pour la coordination d'une pluralité de stations de base et équipement d'utilisateur WO2013099284A1 (fr)

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