WO2017008731A1 - 一种下行预编码方法及基站 - Google Patents

一种下行预编码方法及基站 Download PDF

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Publication number
WO2017008731A1
WO2017008731A1 PCT/CN2016/089767 CN2016089767W WO2017008731A1 WO 2017008731 A1 WO2017008731 A1 WO 2017008731A1 CN 2016089767 W CN2016089767 W CN 2016089767W WO 2017008731 A1 WO2017008731 A1 WO 2017008731A1
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user
precoding
precoding matrix
resource
allocated
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PCT/CN2016/089767
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English (en)
French (fr)
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兰洋
李安新
蒋惠玲
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株式会社Ntt都科摩
都科摩（北京）通信技术研究中心有限公司
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Priority to EP16823878.0A priority Critical patent/EP3324551A4/en
Priority to US15/744,117 priority patent/US10211894B2/en
Priority to JP2018501368A priority patent/JP6595694B2/ja
Priority to CN201680037314.6A priority patent/CN107710638B/zh
Publication of WO2017008731A1 publication Critical patent/WO2017008731A1/zh

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    • 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
    • H04B7/022—Site diversity; Macro-diversity
    • H04B7/024—Co-operative use of antennas of several sites, e.g. in co-ordinated multipoint or co-operative multiple-input multiple-output [MIMO] systems
    • 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
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B17/00—Monitoring; Testing
    • H04B17/30—Monitoring; Testing of propagation channels
    • H04B17/309—Measuring or estimating channel quality parameters
    • 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
    • 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
    • H04B7/0452—Multi-user MIMO systems
    • 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
    • H04B7/0619—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
    • H04B7/0632—Channel quality parameters, e.g. channel quality indicator [CQI]
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W72/00—Local resource management
    • H04W72/12—Wireless traffic scheduling
    • H04W72/1263—Mapping of traffic onto schedule, e.g. scheduled allocation or multiplexing of flows
    • H04W72/1273—Mapping of traffic onto schedule, e.g. scheduled allocation or multiplexing of flows of downlink data flows

Definitions

  • the present invention relates to mobile communication technologies, and in particular, to a downlink precoding method and a base station.
  • the base station when scheduling the downlink transmission, the base station needs the user equipment (UE) to estimate the signal to interference and noise ratio (SINR) of the received signal, determine the channel quality indicator (CQI), and then feed back the CQI through the uplink resource.
  • UE user equipment
  • SINR signal to interference and noise ratio
  • CQI channel quality indicator
  • the base station determines scheduling information such as a radio resource used in downlink transmission and a modulation and coding scheme according to the received CQI.
  • the embodiments of the present invention provide a downlink precoding method and a base station, which are intended to improve the accuracy of downlink scheduling.
  • system throughput and user throughput can also be improved to some extent.
  • a downlink precoding method includes:
  • the first precoding mode records information of a precoding matrix specified for an alternate user of the first cell on a resource to be allocated;
  • a base station comprising:
  • a setting module configured to preset a first precoding mode for the first cell, where the first precoding mode records information about a precoding matrix specified by an alternate user of the first cell on a resource to be allocated;
  • a scheduling module configured to select, from the candidate users, a scheduling user for each resource to be allocated according to the first precoding mode
  • a precoding module configured to precode the channel estimation signal and the downlink data of the scheduling user by using a precoding matrix of the scheduling user
  • a sending module configured to send the pre-coded channel estimation signal and the downlink data to the scheduling user.
  • a base station comprising:
  • One or more processors are One or more processors;
  • One or more instruction units executed by one or more processors are stored in the memory, and the instruction units include a setting module, a scheduling module, a precoding module, and a transmitting module, where
  • the setting module is configured to preset a first precoding mode for the first cell, where the first precoding mode records information about a precoding matrix specified by an candidate user of the first cell on a resource to be allocated. ;
  • the scheduling module is configured to select, from the candidate users, a scheduling user for each resource to be allocated according to the first precoding mode
  • the precoding module is configured to precode the channel estimation signal and the downlink data of the scheduling user by using a precoding matrix of the scheduling user;
  • the sending module is configured to send a pre-coded channel estimation signal and downlink data to the scheduling user.
  • FIG. 1 is a schematic flowchart of a downlink precoding method according to an embodiment of the present invention
  • FIG. 2 is a schematic flowchart of a downlink precoding method according to another embodiment of the present invention.
  • FIG. 3 is a schematic structural diagram of a base station according to an embodiment of the present invention.
  • FIG. 4 is a schematic structural diagram of a base station according to another embodiment of the present invention.
  • FIG. 5 is a schematic diagram of an implementation environment according to an embodiment of the present invention.
  • FIG. 6 is a schematic diagram of comparison between a downlink precoding method according to an embodiment of the present invention and a SINR estimation deviation when not used;
  • FIG. 7 is a schematic diagram of comparison of user throughput when a downlink precoding method according to an embodiment of the present invention is used.
  • FIG. 8 is a schematic diagram of performance comparison when a downlink precoding method according to another embodiment of the present invention is used.
  • FIG. 9 is a schematic structural diagram of a base station according to still another embodiment of the present invention.
  • the UE cannot accurately know the inter-cell interference (ICI) from other cells during the actual downlink data transmission when determining the CQI, the accuracy of the downlink scheduling performed by the base station according to the fed back CQI is not high, for example, the modulation estimated according to the CQI fed back by the UE.
  • the coding scheme is quite different from the ideal modulation and coding scheme that the UE can adopt in actual downlink data transmission, so that the throughput of the cell and the spectrum utilization rate of the user are reduced.
  • FIG. 1 is a schematic flowchart of a downlink precoding method according to an embodiment of the present invention, including the following steps.
  • Step 101 Set a first precoding mode for the first cell in advance, where the first precoding mode records information of a precoding matrix specified by the candidate user of the first cell on the resource to be allocated.
  • the resource to be allocated may be a time-frequency resource unit, for example, a resource block (RB) or a sub-band in a Long Term Evolution (LTE) system.
  • the information of the precoding matrix may be an index of a precoding matrix in a preset codebook as a PMI.
  • the PMI may be specified for a single candidate user on each resource to be allocated, for example, a single user between the base station of the first cell and the user.
  • Multi-antenna (SU-MIMO) transmission; or, multiple PMIs may be specified for multiple candidate users (ie, user groups) on a resource to be allocated, for example, between a base station of a first cell and multiple candidate users.
  • the first precoding mode can be characterized by establishing a PMI mapping table.
  • Table 1 shows a PMI mapping table with PMIs assigned to one or more alternate users on each subband.
  • the subband index is from 1 to 8; the candidate users (groups) include three: user pair UE1 and UE2, single user UE1, and single user UE2.
  • the information of the precoding matrix includes two PMIs: PMI1 and PMI2, which specify the sequence numbers of the two PMIs in the codebook preset at the base station of the first cell.
  • UE1 is pre-set on subband 1 to use PMI1 using PMI1 and UE2, or UE2 is pre-set on subband 1 to use PMI2; UE1 and UE2 are preset on subband 2 Both use PMI2, or pre-set UE1 to use PMI2 on sub-band 2, or pre-set UE2 to use PMI2 on sub-band 2, and so on.
  • Step 102 Select a scheduling user for each resource to be allocated from the candidate users according to the first precoding mode.
  • the first precoding mode specifies all possible users or groups of users on each resource to be allocated, and the scheduling user can be determined according to some optimization criterion, and the precoding matrix used by the scheduling user is also determined by the first precoding mode. .
  • the optimization criteria may include polling, maximum carrier-to-interference ratio (C/I), and ratio A flat (PF) algorithm or the like is used to complete the scheduling.
  • C/I maximum carrier-to-interference ratio
  • PF ratio A flat
  • Step 103 Precoding the channel estimation signal and the downlink data of the scheduling user by using a precoding matrix of the scheduling user, and transmitting the precoded channel estimation signal and the downlink data to the scheduling user.
  • the base station of the first cell sends the pre-coded channel estimation signal to the scheduling user, and after receiving the CQI fed back by the scheduling user according to the received channel estimation signal, the pre-coded downlink data is sent to the scheduling user.
  • the MIMO signal model can be expressed as
  • H(t) is channel state information (CSI) between the scheduling user and the serving base station
  • w(t) is a linear precoding matrix
  • s(t) is a channel estimation signal or a downlink data signal
  • t represents a signal transmission.
  • n(t) is a noise signal
  • y(t) is a reception signal on the UE side.
  • the UE calculates the SINR on each resource block according to the received reference signal, and feeds back the CQI to the base station; After receiving the CQI fed back by the UE, downlink data transmission is performed, that is, the pre-coded downlink data is sent to the scheduling user at the second moment.
  • the base station may determine a modulation and coding scheme used by the downlink data according to the CQI fed back by the UE, and may also serve as a basis for subsequently updating the first precoding mode.
  • the UE may select the feedback PMI and/or RI according to the received reference signal, for example, For codebook-based precoding, PMI and RI may be fed back to the base station by selecting a PMI and an RI that best match the current channel conditions from the codebook according to some optimization criterion.
  • the base station After receiving the information (ie, CQI, PMI/RI) fed back by the UE, the base station precodes the downlink data by using the precoding matrix corresponding to the scheduling user in the first precoding mode, and sends the downlink data at the second time.
  • the base station may determine the modulation and coding scheme used by the downlink data according to the CQI fed back by the UE, and may also use the PMI/RI fed back by the UE for the update of the subsequent first precoding mode.
  • the first precoding mode records information of a precoding matrix specified for an candidate user of the first cell on the to-be-allocated resource, and selects a scheduling user for each resource to be allocated from the candidate users according to the first precoding mode, and uses the scheduling.
  • the precoding matrix of the user precodes the channel estimation signal and the downlink data of the scheduling user, and sends the precoded channel estimation signal and the downlink data to the scheduling user, so that the UE can not feed back the PMI, which reduces the feedback overhead, and the base station is
  • the same precoding matrix is used to ensure that the UE is consistent in ICI from the neighboring cell when estimating the CQI and receiving the downlink data, thereby effectively improving the accuracy of the CQI estimation, so that the base station can Based on the CQI, a more accurate modulation and coding scheme and the number of resource blocks that need to be scheduled can be determined, thereby improving system throughput and user throughput.
  • FIG. 2 is a schematic flowchart of a downlink precoding method according to another embodiment of the present invention, including the following steps.
  • Step 201 Set a first precoding mode for the first cell in advance, where the first precoding mode records information of a precoding matrix specified by the candidate user of the first cell on the to-be-allocated resource.
  • the first cell is a serving cell
  • setting the first precoding mode for the first cell in advance includes: determining a statistical channel feature of each candidate user on each resource to be allocated, where, The channel characteristic may be an average value of instantaneous CSI between the UE and the base station of the first cell within a predetermined time period; the precoding matrix is specified for the corresponding candidate user according to the statistical channel feature; the information of the precoding matrix is recorded in the first In precoding mode.
  • the base station may average the statistical channel characteristics according to the channel state information fed back by each candidate user in the previous time slot, and then according to the statistical channel of each candidate user in the preset codebook.
  • the feature selects a matching PMI, and the matching criterion can be a channel capacity maximization criterion.
  • the base station may recalculate the statistical channel characteristics for a predetermined period of time and then update the first precoding mode.
  • Step 202 Receive a second precoding mode sent by the neighboring cell, where the second precoding mode records information of a precoding matrix used by the neighboring cell on the resource to be allocated.
  • multiple cells participate in coordinated transmission, and the base stations of the cell share Pre-set precoding mode on the common band resource and the codebook used.
  • the base station of the first cell receives the second precoding mode sent by the base station of the neighboring cell, and can obtain the PMI used on each resource.
  • the information interaction between the base stations can be implemented by means of wired transmission.
  • the second precoding mode may adopt a PMI mapping table shown in Table 1, that is, PMI information used by an alternate user (group) in a neighboring cell on a resource to be allocated is specified.
  • the base station of the first cell sends the first precoding mode to the base stations of other neighboring cells, and then the base station of the neighboring cell learns after receiving the first precoding mode: in the subbands 1, 3, 5, and 7 In PMB1 and PMI2; PMI2 is used in subbands 2 and 4; PMI1 is used in subbands 6 and 8.
  • the second precoding mode may adopt a simplified PMI mapping table, that is, only specify the PMI information used on the resource to be allocated.
  • the simplified PMI mapping table is shown in Table 2. Among them, the PMI index used is listed on each subband.
  • the multiple base stations participating in the cell coordination send the updated precoding mode to other base stations participating in the cell cooperation for subsequent scheduling.
  • Step 203 Select a scheduling user for each resource to be allocated from the candidate users according to the first precoding mode and the second precoding mode.
  • the resource to be allocated may be calculated according to the first precoding matrix and the second precoding matrix.
  • the SINR of the user is preset to characterize the throughput. Specifically, calculating received signal power of the candidate user according to the first precoding matrix; calculating inter-cell interference power between the first cell and the neighboring cell according to the first precoding matrix and the second precoding matrix; according to the received signal The power and inter-cell interference power is calculated as the signal to interference and noise ratio.
  • the SINR is calculated as follows:
  • SINR k (t) is the SINR obtained by the UE at time t and the kth subband
  • K is the total number of subbands
  • P S (t) represents the received signal power
  • P Int (t) is the inter-cell interference power, ie The sum of the powers of the downlink interference signals transmitted by the neighboring cells received on the resources to be allocated
  • P N is the noise power.
  • the candidate user specified in the first precoding mode for the to-be-allocated resource is divided into multiple user groups, and the user group may include one or more users; for each user group, Determining a first precoding matrix of each candidate user of the user group recorded in the first precoding mode, that is, each user group may correspond to one or more first precoding matrices; using the first precoding matrix and The second precoding matrix calculates a throughput of the candidate user on the to-be-allocated resource; sums the throughputs of all candidate users in the user group as the throughput of the user group on the to-be-allocated resource; The user group with the highest throughput is determined as the scheduled user on the resource to be allocated.
  • the alternate users are divided into 3 user groups on each subband.
  • the SINR calculation method shown in the above formula (2) can be further expressed as:
  • H(t) k, 0 is the downlink channel matrix between the serving base station and the UE of the first cell on the kth subband at time t;
  • H(t) k, i is at time t, the kth subband a downlink channel matrix between the i-th interfering base station and the UE of the neighboring cell;
  • w(t) k, 0 is a precoding matrix specified by the serving base station of the first cell at the time t and the kth subband for the UE , that is, the first precoding matrix;
  • w(t) k, i is a precoding matrix used by the ith interfering base station of the neighboring cell on the kth subband at time t, that is, the second precoding matrix; a set of neighboring cells;
  • () * indicates a conjugate transpose operation.
  • the method for determining the second precoding matrix is as follows: searching for at least one precoding matrix preset for the resource to be allocated in the second precoding mode, and weighting and summing the at least one precoding matrix Second precoding matrix.
  • the specific value of ⁇ 1 and ⁇ 2 may be preset by the base station of the first cell, and is not specifically limited in the present invention.
  • the SINR k of each user j in the user group can be calculated by referring to formula (3) . j (t), then the total SINR on the kth subband is the sum of the SINRs of all candidate users in the user group, expressed as:
  • M is the total number of candidate users in the user group.
  • Step 204 Precoding the channel estimation signal by using a precoding matrix of the scheduling user, and transmitting the precoded channel estimation signal to the scheduling user at the first moment.
  • the channel estimation signal can be a reference signal, and the reference signal is precoded using a precoding matrix of the scheduling user.
  • Step 205 Perform precoding on the downlink data of the scheduling user by using the precoding matrix of the scheduling user, and send the precoded downlink data to the scheduling user at the second moment, where the second moment is after the first moment.
  • the first time and the second time are identified by the sequence numbers of the downlink subframes, which are respectively n1 and n2.
  • n2 n1 + 4.
  • the specific values of the first time and the second time are not specifically limited in the embodiment of the present invention.
  • the base station may explicitly indicate the information of the PMI used by the base station in the downlink control signaling, such as the index of the PMI; or the base station sends the dedicated pilot to the UE to learn the PMI used, as in the above formula (1).
  • the base station transmits a dedicated pilot to the UE to learn the equivalent channel information, that is, the pre-coded channel state information, such as H(t)w(t) in the above formula (1).
  • the sharing of the precoding mode between the coordinated cells enables the base station of the first cell to learn the second precoding matrix used in the two times of transmitting the reference signal and the downlink data transmission, thereby further improving the accuracy of estimating the SINR during scheduling, thereby Improve system throughput and user throughput.
  • FIG. 3 is a schematic structural diagram of a base station 300 according to an embodiment of the present invention, including:
  • the setting module 310 is configured to preset a first precoding mode for the first cell, where the first precoding mode records information about a precoding matrix specified by the candidate user of the first cell on the to-be-allocated resource;
  • the scheduling module 320 is configured to select a scheduling user for each resource to be allocated from the candidate users according to the first precoding mode set by the setting module 310.
  • the precoding module 330 is configured to precode the channel estimation signal and the downlink data of the scheduling user selected by the scheduling module 320 by using the precoding matrix of the scheduling user selected by the scheduling module 320.
  • the sending module 340 is configured to send, to the scheduling user, the channel estimation signal and the downlink data precoded by the precoding module 330.
  • FIG. 4 is a schematic structural diagram of a base station 400 according to an embodiment of the present invention. Based on the base station 300 shown in FIG. 3, the base station 400 further includes:
  • the receiving module 350 is configured to receive a second precoding mode sent by the neighboring cell, where the second precoding mode records information about a precoding matrix used by the neighboring cell on the to-be-allocated resource;
  • the scheduling module 320 includes:
  • a determining unit 321, configured to determine, according to the first precoding mode set by the setting module 310, an candidate user on the to-be-allocated resource and a first pre-coding matrix specified for the candidate user for each resource to be allocated;
  • the second precoding mode received by the module 350 determines that the neighboring cell is in the to-be-allocated resource a second precoding matrix used on;
  • the calculating unit 322 is configured to calculate, according to the first precoding matrix and the second precoding matrix determined by the determining unit 321, the throughput of the candidate user on the to-be-allocated resource;
  • the scheduling unit 323 is configured to determine, as the scheduled user on the to-be-allocated resource, an candidate user that maximizes the throughput calculated by the computing unit 322.
  • the determining unit 321 is configured to: divide an candidate user specified for the to-be-allocated resource in the first pre-coding mode into a plurality of user groups; and determine, in each user group, the first pre-coding a first precoding matrix of each candidate user of the user group recorded in the mode;
  • the calculating unit 322 is configured to: calculate, by using the first precoding matrix and the second precoding matrix, a throughput of the candidate user on the to-be-allocated resource; add the throughputs of all candidate users in the user group, as The throughput of the user group on the resource to be allocated;
  • the scheduling unit 323 is configured to: determine a user group with the largest throughput as the scheduled user on the to-be-allocated resource.
  • the determining unit 321 is configured to: search for at least one precoding matrix preset for the to-be-allocated resource in the second pre-coding mode, and weight and sumat the at least one pre-coding matrix to obtain a second pre-coding. matrix.
  • the calculating unit 322 is configured to: calculate received signal power of the candidate user according to the first precoding matrix; calculate the first cell and the neighboring cell according to the first precoding matrix and the second precoding matrix.
  • Inter-cell interference power calculation of signal to interference and noise ratio SINR based on received signal power and inter-cell interference power.
  • the setting module 310 is configured to: determine a statistical channel feature of each candidate user on each resource to be allocated; specify a precoding matrix for the corresponding candidate user according to the statistical channel feature; and the precoding matrix The information is recorded in the first precoding mode.
  • the sending module 340 is configured to: send a pre-coded channel estimation signal to a scheduling user; and send a scheduled channel quality indication CQI according to the received channel estimation signal, and send the message to the scheduling user. Down-coded data after precoding.
  • FIG. 5 is a schematic diagram of an implementation environment in an embodiment of the present invention.
  • the base station has two antennas, and performs SU-MIMO transmission with UE#1 and UE#2, respectively. Since the channel quality difference between the UE#1 and the UE#2 is large, the base station can also use the NOMA transmission in the downlink scheduling, that is, the transmission signals of the UE#1 and the UE#2 are superimposed, and the channel quality difference between the two can be converted into The multiplexing gain, the UE uses the serial interference cancellation technology for demultiplexing. In NOMA transmission, the power used for SU-MIMO transmission on the two links is different, UE#1 uses the power defined by power level 1, and UE#2 uses the power defined by power level 2.
  • the transmission mode (TM) related to precoding includes a plurality of types.
  • the UE in the third transmission mode (TM3), the UE does not need to report the PMI, and only needs to report the CQI and the rank of the channel (RI).
  • the choice of the coding matrix is pre-set and can be understood as a blind precoding method.
  • the first precoding mode shown in Table 1 can be used to determine the PMIs used by the possible users or groups of users on each subband.
  • the performance of the downlink precoding method provided by the embodiment of the present invention and the downlink precoding provided by the embodiment of the present invention are compared by simulation.
  • Table 3 shows the system level parameters used in the simulation.
  • the method for determining a precoding matrix for downlink data transmission based on the user feedback PMI in the existing LTE system is simply referred to as a “feedback based method”.
  • FIG. 6 is a schematic diagram of comparison of a downlink precoding method according to an embodiment of the present invention and an SINR estimation deviation when not used.
  • the SINR estimation deviation is a difference between a SINR estimated by the scheduled user and a real SINR when the downlink estimated data is sent by the scheduled user, and the cumulative distribution function (CDF) curve of the SINR estimation deviation is The SINR estimation deviation is effectively reduced by using the downlink precoding method provided by the embodiment of the present invention.
  • CDF cumulative distribution function
  • FIG. 7 is a schematic diagram of comparison of user throughput when a downlink precoding method according to an embodiment of the present invention is used and when not used. It can be seen from the CDF curve of the user that the downlink precoding method provided by the embodiment of the present invention is used, and the user throughput is obviously improved.
  • FIG. 8 is a schematic diagram of performance comparison when a downlink precoding method according to another embodiment of the present invention is used and when not used. Performance includes cell average throughput and cell edge user throughput. It can be seen that the downlink precoding method provided by the embodiment of the present invention is used, and both parameters have a throughput gain of about 10%.
  • FIG. 9 is a schematic structural diagram of a base station according to still another embodiment of the present invention.
  • the base station includes one or more processors 901, memory 902, and one or more instruction units 903 stored on memory 902 for execution by one or more processors 901.
  • the instruction unit 903 may include a setting module 310, a scheduling module 320, a precoding module 330, a transmitting module 340, and a receiving module 350.
  • These virtual modules include instructions for implementing the respective functions such that when the processor 901 and the memory 902 communicate, read and execute the instructions, the base station can implement the corresponding functions.
  • the first precoding mode is set for the first cell in advance, and the first precoding mode records a precoding matrix specified for the candidate user of the first cell on the resource to be allocated.
  • the information allows the UE to not feed back the PMI, reducing feedback overhead.
  • the second precoding mode sent by the neighboring cell is received, and the scheduling user is selected from the candidate users for each resource to be allocated according to the first precoding mode and the second precoding mode, so that the inter-cell coordinated transmission is performed.
  • the base station can learn the precoding matrix used by the neighboring cell, and then calculate the SINR more accurately when the user is scheduled; and the base station uses the precoding matrix of the scheduling user to precode the channel estimation signal and the downlink data of the scheduling user, so that the UE estimates
  • the CQI is consistent with the ICI received from the neighboring cell when receiving the downlink data, thereby effectively improving the accuracy of the CQI estimation, so that the base station can determine a more accurate modulation and coding scheme and the number of resource blocks to be scheduled based on the CQI, thereby Improve the accuracy of downlink scheduling. Simulation results show that system throughput and user throughput are improved to some extent.

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Abstract

本发明公开了一种下行预编码的方法及基站。该方法的过程包括：预先为第一小区设置第一预编码模式，第一预编码模式记录有在待分配资源上为第一小区的备选用户指定的预编码矩阵的信息；根据第一预编码模式从备选用户中为每个待分配资源选出调度用户；及，使用调度用户的预编码矩阵对信道估计信号和调度用户的下行数据进行预编码，并向调度用户发送预编码后的信道估计信号和下行数据。本发明的这种方法及基站，能够减少用户的反馈开销，有效改善信道质量指示CQI估计的准确性，提高系统吞吐量以及用户吞吐量。

Description

一种下行预编码方法及基站
本申请要求于2015年7月14日提交中国专利局、申请号为201510412104.8、申请名称为“一种下行预编码方法及基站”的中国专利申请的优先权，其全部内容通过引用结合在本申请中。
技术领域
本发明涉及移动通信技术，特别涉及一种下行预编码方法及基站。
背景技术
在无线通信系统中，基站在为下行传输进行调度时，需要用户设备(UE)估算出接收信号的信干噪比(SINR)，确定信道质量指示(CQI)，再通过上行资源将CQI反馈给基站。基站根据接收的CQI来确定下行传输使用的无线资源、调制编码方案等调度信息。
发明内容
有鉴于此，本发明实施例提供了一种下行预编码方法及基站，旨在提高下行调度的准确性。相应地，系统吞吐量以及用户吞吐量在一定程度上也能得到提高。
具体地，本发明实施例的技术方案是这样实现的：
一种下行预编码方法，包括：
预先为第一小区设置第一预编码模式，所述第一预编码模式记录有在待分配资源上为所述第一小区的备选用户指定的预编码矩阵的信息；
根据所述第一预编码模式从所述备选用户中为每个待分配资源选出调度用户；及，
使用所述调度用户的预编码矩阵对信道估计信号和所述调度用户的下行数据进行预编码，并向所述调度用户发送预编码后的信道估计信号和下行数据。
一种基站，包括：
设置模块，用于预先为第一小区设置第一预编码模式，所述第一预编码模式记录有在待分配资源上为所述第一小区的备选用户指定的预编码矩阵的信息；
调度模块，用于根据所述第一预编码模式从所述备选用户中为每个待分配资源选出调度用户；
预编码模块，用于使用所述调度用户的预编码矩阵对信道估计信号和所述调度用户的下行数据进行预编码；及，
发送模块，用于向所述调度用户发送预编码后的信道估计信号和下行数据。
一种基站，其特征在于，包括：
存储器；
一个或多个处理器；以及
存储器中存储有由一个或多个处理器来执行的一个或多个指令单元，所述指令单元包括设置模块、调度模块、预编码模块和发送模块，其中，
所述设置模块，用于预先为第一小区设置第一预编码模式，所述第一预编码模式记录有在待分配资源上为所述第一小区的备选用户指定的预编码矩阵的信息；
所述调度模块，用于根据所述第一预编码模式从所述备选用户中为每个待分配资源选出调度用户；
所述预编码模块，用于使用所述调度用户的预编码矩阵对信道估计信号和所述调度用户的下行数据进行预编码；及，
所述发送模块，用于向所述调度用户发送预编码后的信道估计信号和下行数据。
附图说明
图1为本发明一实施例中下行预编码方法的流程示意图；
图2为本发明另一实施例中下行预编码方法的流程示意图；
图3为本发明一实施例中基站的结构示意图；
图4为本发明另一实施例中基站的结构示意图；
图5为本发明一实施例的实施环境示意图；
图6为采用本发明一实施例提供的下行预编码方法和未采用时的SINR估计偏差的比较示意图；
图7为采用本发明一实施例提供的下行预编码方法和未采用时的用户吞吐量比较示意图；
图8为采用本发明另一实施例提供的下行预编码方法和未采用时的性能比较示意图；
图9为本发明又一实施例中基站的结构示意图。
具体实施方式
为使本发明的目的、技术方案及优点更加清楚明白，以下参照附图并举实施例，对本发明进一步详细说明。
由于UE在确定CQI时无法准确获知实际下行数据传输时来自其他小区的小区间干扰(ICI)，导致基站根据反馈的CQI进行下行调度的准确度不高，例如根据UE反馈的CQI估计出的调制编码方案与实际下行数据传输时UE可采用的理想的调制编码方案相差较大，从而使得小区的吞吐量以及用户的频谱利用率降低。
图1为本发明一实施例中下行预编码方法的流程示意图，包括以下步骤。
步骤101，预先为第一小区设置第一预编码模式，第一预编码模式记录有在待分配资源上为第一小区的备选用户指定的预编码矩阵的信息。
在本步骤中，待分配资源可以为一个时频资源单位，例如，长期演进(LTE)系统中的资源块(RB)或者子带(subband)。预编码矩阵的信息可以为在预先设置的码本中预编码矩阵的索引作为PMI。其中，在每一待分配资源上，可以为单个备选用户指定PMI，例如第一小区的基站和用户之间进行单用户 多天线(SU-MIMO)传输；或者，也可以在待分配资源上为多个备选用户(即用户组)逐一指定多个PMI，例如第一小区的基站和多个备选用户之间进行多用户多天线(MU-MIMO)传输或者非正交多址接入(NOMA)传输。
在本发明一实施例中，第一预编码模式可以通过建立PMI映射表来表征。表1示出一种PMI映射表，在每个子带上为一个或多个备选用户指定PMI。如表1所示，子带索引从1到8；备选用户(组)包括3个：用户对UE1和UE2、单个用户UE1和单个用户UE2。预编码矩阵的信息包括两个PMI：PMI1和PMI2，其指定了在第一小区的基站处预先设置的码本中两个PMI的序号。
在表1所示的第一预编码模式中，在子带1上预先设置UE1使用PMI1和UE2使用PMI2，或者在子带1上预先设置UE2使用PMI2；在子带2上预先设置UE1和UE2都使用PMI2，或者在子带2上预先设置UE1使用PMI2，或者在子带2上预先设置UE2使用PMI2，等等。
Figure PCTCN2016089767-appb-000001
表1 第一预编码模式-PMI映射表
步骤102，根据第一预编码模式从备选用户中为每个待分配资源选出调度用户。
第一预编码模式指定了每个待分配资源上所有可能的用户或用户组，可以根据某种优化准则确定调度用户，同时由第一预编码模式也就确定了该调度用户使用的预编码矩阵。
在具体应用中，该优化准则可以包括轮询、最大载干比(C/I)、比例公 平(PF)算法等来完成调度。
步骤103，使用调度用户的预编码矩阵对信道估计信号和调度用户的下行数据进行预编码，并向调度用户发送预编码后的信道估计信号和下行数据。
在本步骤中，第一小区的基站向调度用户发送预编码后的信道估计信号，在接收到调度用户根据接收到的信道估计信号反馈的CQI后，向调度用户发送预编码后的下行数据。例如，若使用线性预编码算法，在经过线性预编码之后，MIMO信号模型可以表示为
y(t)＝H(t)w(t)s(t)+n(t)          (1)
其中，H(t)为调度用户和服务基站之间的信道状态信息(CSI)，w(t)为线性预编码矩阵，s(t)为信道估计信号或下行数据信号，t代表信号发送的时刻，n(t)为噪声信号，y(t)为UE侧的接收信号。
在本发明一实施例中，基站在第一时刻向调度用户发送预编码后的参考信号后，UE根据接收到的参考信号，计算得到每个资源块上的SINR，向基站反馈CQI；基站在接收到UE反馈的CQI后，进行下行数据传输，即在第二时刻向调度用户发送预编码后的下行数据。基站可以根据UE反馈的CQI确定下行数据所使用的调制编码方案，并且还可以作为后续更新第一预编码模式的依据。
在本发明另一实施例中，基站在第一时刻向调度用户发送预编码后的参考信号后，UE根据接收到的参考信号，除了反馈CQI，也可以选择反馈PMI和/或RI，例如，对于基于码本的预编码，可以按照某种优化准则从码本中选择与当前信道条件最为匹配的PMI以及RI，向基站反馈PMI和/或RI。基站在接收到UE反馈的信息(即CQI、PMI/RI)后，使用第一预编码模式中该调度用户对应的预编码矩阵对下行数据进行预编码，并在第二时刻发出。基站可以根据UE反馈的CQI确定下行数据所使用的调制编码方案，并且还可以根据UE反馈的PMI/RI用于后续第一预编码模式的更新。
在本发明的实施例中，通过预先为第一小区设置第一预编码模式，第一 预编码模式记录有在待分配资源上为第一小区的备选用户指定的预编码矩阵的信息，根据第一预编码模式从备选用户中为每个待分配资源选出调度用户，使用调度用户的预编码矩阵对信道估计信号和调度用户的下行数据进行预编码，并向调度用户发送预编码后的信道估计信号和下行数据，使得UE可以不反馈PMI，减少了反馈开销，并且基站在发送信道估计信号和下行数据时使用相同的预编码矩阵，能够保证UE在估计CQI和接收下行数据时所受到来自相邻小区的ICI是一致的，从而有效改善CQI估计的准确性，使得基站可以基于该CQI能够确定更加准确的调制编码方案以及需要调度的资源块数量，从而提高系统吞吐量以及用户吞吐量。
图2为本发明另一实施例中下行预编码方法的流程示意图，包括以下步骤。
步骤201，预先为第一小区设置第一预编码模式，第一预编码模式记录有在待分配资源上为第一小区的备选用户指定的预编码矩阵的信息。
在本发明一实施例中，第一小区为服务小区，预先为该第一小区设置第一预编码模式包括：确定每个待分配资源上的每个备选用户的统计信道特征，其中，统计信道特征可以为在预定时间段内UE和第一小区的基站之间的瞬时CSI的平均值；根据统计信道特征为相应的备选用户指定预编码矩阵；将预编码矩阵的信息记录在第一预编码模式中。
具体而言，在LTE系统中，基站可以根据每个备选用户在之前时隙中反馈的信道状态信息进行平均得到统计信道特征，然后在预设码本中根据每个备选用户的统计信道特征选择一个匹配的PMI，匹配的准则可以为信道容量最大化准则。此外，基站可以以预定时间段为周期重新计算统计信道特征，然后更新第一预编码模式。
步骤202，接收相邻小区发送的第二预编码模式，第二预编码模式记录有相邻小区在待分配资源上使用的预编码矩阵的信息。
在本发明一实施例中，多个小区参与协同传输，小区的基站之间共享在 共同的频带资源上预先设置的预编码模式以及所使用的码本。第一小区的基站接收到相邻小区的基站发送的第二预编码模式，能够从中获知每个资源上所使用的PMI。基站之间的信息交互可以采用有线传输的方式来实现。
在本发明一实施例中，第二预编码模式可以采用表1所示的PMI映射表，即指定了在待分配资源上相邻小区中的备选用户(组)所使用的PMI信息。同样地，第一小区的基站将第一预编码模式发送给其他相邻小区的基站，那么相邻小区的基站在接收到第一预编码模式后获知：在子带1、3、5和7中，使用PMI1和PMI2；在子带2和4中，使用PMI2；在子带6和8中，使用PMI1。
在本发明另一实施例中，第二预编码模式可以采用一个简化的PMI映射表，即仅指定在待分配资源上所使用的PMI信息。对应表1，简化的PMI映射表如表2所示。其中，在每个子带上列出了所使用的PMI索引。
Figure PCTCN2016089767-appb-000002
表2 第二预编码模式-简化的PMI映射表
此外，参与小区协同的多个基站在更新预编码模式后，将更新后的预编码模式发送给参与小区协同的其他基站，以用于后续调度。
步骤203，根据第一预编码模式和第二预编码模式从备选用户中为每个待分配资源选出调度用户。
在本步骤中，针对每个待分配资源，根据第一预编码模式确定在该待分配资源上的备选用户以及为备选用户指定的第一预编码矩阵；根据第二预编码模式确定相邻小区在该待分配资源上使用的第二预编码矩阵；根据第一预编码矩阵和第二预编码矩阵计算在该待分配资源上的备选用户的吞吐量；将吞吐量最大的备选用户确定为该待分配资源上的调度用户。
其中，可以根据第一预编码矩阵和第二预编码矩阵计算在该待分配资源 上预先设置的用户的SINR来表征吞吐量。具体而言，根据第一预编码矩阵计算备选用户的接收信号功率；根据第一预编码矩阵和第二预编码矩阵计算第一小区和相邻小区之间的小区间干扰功率；根据接收信号功率和小区间干扰功率计算信干噪比。
例如，在经过线性预编码后，SINR的计算方式如下：
Figure PCTCN2016089767-appb-000003
其中，SINRk(t)为UE在t时刻、第k个子带上得到的SINR，K为子带总数，PS(t)表示接收信号功率，PInt(t)为小区间干扰功率，即待分配资源上所接收的相邻小区所发送下行干扰信号的功率之和，PN为噪声功率。
在本发明一实施例中，将第一预编码模式中为该待分配资源指定的备选用户划分为多个用户组，该用户组内可以包括一个或多个用户；针对每个用户组，确定在第一预编码模式中记录的该用户组的每个备选用户的第一预编码矩阵，即每个用户组可以对应一个或多个第一预编码矩阵；利用第一预编码矩阵和第二预编码矩阵计算在该待分配资源上该备选用户的吞吐量；将该用户组中所有备选用户的吞吐量相加，作为在该待分配资源上的用户组的吞吐量；将吞吐量最大的用户组确定为该待分配资源上的调度用户
参照表1所示的第一预编码模式，在每个子带上备选用户被分为3个用户组。当用户组内包括一个用户，对应一个第一预编码矩阵时，上述公式(2)所示的SINR计算方式可以进一步表示为：
Figure PCTCN2016089767-appb-000004
其中，H(t)k，0为在t时刻、第k个子带上第一小区的服务基站与UE之间的下行信道矩阵；H(t)k，i为在t时刻、第k个子带上相邻小区的第i个干扰基站与UE之间的下行信道矩阵；w(t)k，0为在t时刻、第k个子带上第一小区的服务基站为UE所指定的预编码矩阵，即第一预编码矩阵；w(t)k，i为在t时刻、第k个子带上相邻小区的第i个干扰基站所使用的预编码矩阵，即第二预编 码矩阵；Φ为相邻小区集合；()*表示共轭转置操作。
在本发明一实施例中，第二预编码矩阵的确定方法如下：查找第二预编码模式中为该待分配资源预先设置的至少一个预编码矩阵，并将至少一个预编码矩阵加权求和得到第二预编码矩阵。例如，参照表2所示的第二预编码模式，在子带1上使用PMI1所表示的预编码矩阵ω1和PMI2所表示的预编码矩阵ω2，那么第二预编码矩阵w(t)k，i＝β1ω1+β2ω2，其中，β1和β2分别表示两个预定权重，且β1+β2＝1。其中，β1和β2的具体取值可以由第一小区的基站预先设定，本发明不做具体限定。
参照表1所示的第一预编码模式，当用户组内包括两个用户，对应两个第一预编码矩阵时，可以参照公式(3)计算得到用户组中每一个用户j的SINRk，j(t)，然后在第k个子带上的总SINR为用户组中所有备选用户的SINR之和，表示为：
Figure PCTCN2016089767-appb-000005
其中，M为用户组中备选用户总数。
步骤204，使用调度用户的预编码矩阵对信道估计信号进行预编码，并在第一时刻向调度用户发送预编码后的信道估计信号。
该信道估计信号可以为参考信号，使用调度用户的预编码矩阵对参考信号进行预编码。
步骤205，使用调度用户的预编码矩阵对调度用户的下行数据进行预编码，并在第二时刻向调度用户发送预编码后的下行数据，其中，第二时刻在第一时刻之后。
例如，在LTE系统中，第一时刻和第二时刻由下行子帧的序号来标识，分别为n1和n2。在时分复用(TDD)系统中，n2＝n1+4。对于第一时刻和第二时刻的具体取值，本发明实施例不做具体限定。
此外，考虑到基站在传输下行数据时使用的PMI可能与UE上报的PMI不一致，为了保证UE能够获知预编码后的等效信道并对下行数据进行相干 解调，基站可以在下行控制信令中明确指示其所用的PMI的信息，例如PMI的索引；或者，基站向UE发送专用导频使其获知所使用的PMI，如上述公式(1)中的w(t)；或者，基站向UE发送专用导频使其获知等效的信道信息，即预编码后的信道状态信息，如上述公式(1)中的H(t)w(t)。
在上述实施例中，通过接收相邻小区发送的第二预编码模式，根据第一预编码模式和第二预编码模式从备选用户中为每个待分配资源选出调度用户，实现了多个协同小区之间预编码模式的共享，使得第一小区的基站获知在发送参考信号和下行数据传输两个时刻所使用的第二预编码矩阵，进一步提高了调度时估计SINR的准确性，从而提高系统吞吐量以及用户吞吐量。
图3为本发明一实施例中基站300的结构示意图，包括：
设置模块310，用于预先为第一小区设置第一预编码模式，第一预编码模式记录有在待分配资源上为第一小区的备选用户指定的预编码矩阵的信息；
调度模块320，用于根据设置模块310设置的第一预编码模式从备选用户中为每个待分配资源选出调度用户；
预编码模块330，用于使用调度模块320选出的调度用户的预编码矩阵对信道估计信号和调度模块320选出的调度用户的下行数据进行预编码；
发送模块340，用于向调度用户发送预编码模块330预编码后的信道估计信号和下行数据。
图4为本发明一实施例中基站400的结构示意图。在图3所示的基站300的基础上，基站400还包括：
接收模块350，用于接收相邻小区发送的第二预编码模式，第二预编码模式记录有相邻小区在待分配资源上使用的预编码矩阵的信息；
相应地，调度模块320包括：
确定单元321，用于针对每个待分配资源，根据设置模块310设置的第一预编码模式确定在该待分配资源上的备选用户以及为备选用户指定的第一预编码矩阵；根据接收模块350接收的第二预编码模式确定相邻小区在该待分配资源 上使用的第二预编码矩阵；
计算单元322，用于根据确定单元321确定的第一预编码矩阵和第二预编码矩阵计算在该待分配资源上的备选用户的吞吐量；
调度单元323，用于将计算单元322所计算的吞吐量最大的备选用户确定为该待分配资源上的调度用户。
在本发明一实施例中，确定单元321用于：将第一预编码模式中为该待分配资源指定的备选用户划分为多个用户组；针对每个用户组，确定在第一预编码模式中记录的该用户组的每个备选用户的第一预编码矩阵；
计算单元322用于：利用第一预编码矩阵和第二预编码矩阵计算在该待分配资源上该备选用户的吞吐量；将该用户组中所有备选用户的吞吐量相加，作为在该待分配资源上的用户组的吞吐量；
调度单元323用于：将吞吐量最大的用户组确定为该待分配资源上的调度用户。
在本发明一实施例中，确定单元321用于：查找第二预编码模式中为该待分配资源预先设置的至少一个预编码矩阵，并将至少一个预编码矩阵加权求和得到第二预编码矩阵。
在本发明一实施例中，计算单元322用于：根据第一预编码矩阵计算备选用户的接收信号功率；根据第一预编码矩阵和第二预编码矩阵计算第一小区和相邻小区之间的小区间干扰功率；根据接收信号功率和小区间干扰功率计算信干噪比SINR。
在本发明一实施例中，设置模块310用于：确定每个待分配资源上每个备选用户的统计信道特征；根据统计信道特征为相应的备选用户指定预编码矩阵；将预编码矩阵的信息记录在第一预编码模式中。
在本发明一实施例中，发送模块340用于：向调度用户发送预编码后的信道估计信号；在接收到调度用户根据接收到的信道估计信号反馈的信道质量指示CQI后，向调度用户发送预编码后的下行数据。
图5为本发明一实施例中的实施环境示意图。其中，基站有两根天线，分别与UE#1和UE#2进行SU-MIMO传输。由于UE#1和UE#2的信道质量差异较大，基站在下行调度时还可以采用NOMA传输，即将UE#1和UE#2的发射信号进行叠加，可以将二者的信道质量差异转换为复用增益，UE采用串行干扰删除技术进行解复用。在NOMA传输中，两个链路上进行SU-MIMO传输使用的功率不同，UE#1使用由功率级别1所限定的功率，UE#2使用由功率级别2所限定的功率。
在LTE规范中，与预编码相关的传输模式(TM)包括多种，例如在第3种传输模式(TM3)中，UE不需要上报PMI，只需要上报CQI和信道的秩(RI)，预编码矩阵的选择是预先设定的，可理解为一种盲预编码方式。在该传输模式下，可以使用表1所示出的第一预编码模式来确定每个子带上可能的用户或者用户组所使用的PMI。
通过仿真对采用本发明实施例提供的下行预编码方法和未采用本发明实施例提供的下行预编码时的性能进行比较，表3示出仿真中使用到的系统级参数。其中，未采用本发明实施例提供的下行预编码时，是采用现有LTE系统中基于用户反馈的PMI确定下行数据传输时的预编码矩阵的方法，简称为“基于反馈的方法”。
Figure PCTCN2016089767-appb-000006
Figure PCTCN2016089767-appb-000007
表3 仿真参数
图6为采用本发明一实施例提供的下行预编码方法和未采用时的SINR估计偏差的比较示意图。其中，SINR估计偏差是指向调度用户发送预编码后的信道估计信号所估计的SINR和下行数据时的真实SINR之间的差值，从SINR估计偏差的累积分布函数(CDF)曲线可以看出，使用了本发明实施例所提供的下行预编码方法，SINR估计偏差被有效减小。
图7为采用本发明一实施例提供的下行预编码方法和未采用时的用户吞吐量比较示意图。其中，从用户吞吐的CDF曲线可以看出，使用了本发明实施例所提供的下行预编码方法，用户吞吐有了明显的提高。
图8为采用本发明另一实施例提供的下行预编码方法和未采用时的性能比较示意图。性能包括小区平均吞吐和小区边缘用户吞吐。可见，使用了本发明实施例所提供的下行预编码方法，这两种参数都有大约10％的吞吐增益。
图9为本发明又一实施例中基站的结构示意图。如图9所示，该基站包括一个或多个处理器901、存储器902以及存储在存储器902上用来由一个或多个处理器901来执行的一个或多个指令单元903。指令单元903可以包括设置模块310、调度模块320、预编码模块330、发送模块340和接收模块350。这些虚拟模块包括了用于实现各自功能的指令，这样当处理器901和存储器902进行通信，读取并执行指令时，基站可以实现相应的功能。
根据本发明实施例提供的下行预编码方法，通过预先为第一小区设置第一预编码模式，第一预编码模式记录有在待分配资源上为第一小区的备选用户指定的预编码矩阵的信息，使得UE可以不反馈PMI，减少了反馈开销。进一步地，接收相邻小区发送的第二预编码模式，根据第一预编码模式和第二预编码模式从备选用户中为每个待分配资源选出调度用户，使得通过小区间协同传输，基站能够获知相邻小区所使用的预编码矩阵，那么在调度用户时计算SINR更准确；并且基站使用调度用户的预编码矩阵对信道估计信号和调度用户的下行数据进行预编码，使得UE在估计CQI和接收下行数据时所受到来自相邻小区的ICI是一致的，从而有效改善CQI估计的准确性，使得基站可以基于该CQI能够确定更加准确的调制编码方案以及需要调度的资源块数量，从而提高下行调度的准确性。仿真结果显示，系统吞吐量以及用户吞吐量在一定程度上得到提高。
以上所述仅为本发明的较佳实施例而已，并不用以限制本发明，凡在本发明的精神和原则之内，所作的任何修改、等同替换、改进等，均应包含在本发明的保护范围之内。

Claims (15)

  1. 一种下行预编码方法，其特征在于，包括：
    预先为第一小区设置第一预编码模式，所述第一预编码模式记录有在待分配资源上为所述第一小区的备选用户指定的预编码矩阵的信息；
    根据所述第一预编码模式从所述备选用户中为每个待分配资源选出调度用户；及，
    使用所述调度用户的预编码矩阵对信道估计信号和所述调度用户的下行数据进行预编码，并向所述调度用户发送预编码后的信道估计信号和下行数据。
  2. 根据权利要求1所述的方法，其特征在于，进一步包括：
    接收相邻小区发送的第二预编码模式，所述第二预编码模式记录有所述相邻小区在待分配资源上使用的预编码矩阵的信息；
    所述根据所述第一预编码模式从所述备选用户中为每个待分配资源选出调度用户包括：
    针对每个待分配资源，根据所述第一预编码模式确定在该待分配资源上的备选用户以及为该备选用户指定的第一预编码矩阵；
    根据所述第二预编码模式确定所述相邻小区在该待分配资源上使用的第二预编码矩阵；
    根据所述第一预编码矩阵和所述第二预编码矩阵计算在该待分配资源上的备选用户的吞吐量；
    将吞吐量最大的备选用户确定为该待分配资源上的调度用户。
  3. 根据权利要求2所述的方法，其特征在于，所述根据所述第一预编码矩阵和所述第二预编码矩阵计算在该待分配资源上的备选用户的吞吐量，将吞吐量最大的备选用户确定为该待分配资源上的调度用户包括：
    将所述第一预编码模式中为该待分配资源指定的备选用户划分为多个用户组；
    针对每个用户组，确定在所述第一预编码模式中记录的该用户组的每个备选 用户的第一预编码矩阵；
    利用所述第一预编码矩阵和所述第二预编码矩阵计算在该待分配资源上该备选用户的吞吐量；
    将该用户组中所有备选用户的吞吐量相加，作为在该待分配资源上的用户组的吞吐量；
    将吞吐量最大的用户组确定为该待分配资源上的调度用户。
  4. 根据权利要求2所述的方法，其特征在于，所述根据该第二预编码模式确定所述相邻小区在该待分配资源上使用的第二预编码矩阵包括：
    查找所述第二预编码模式中为该待分配资源预先设置的至少一个预编码矩阵，并将所述至少一个预编码矩阵加权求和得到所述第二预编码矩阵。
  5. 根据权利要求2所述的方法，其特征在于，所述根据所述第一预编码矩阵和所述第二预编码矩阵计算在该待分配资源上的备选用户的吞吐量包括：
    根据所述第一预编码矩阵计算所述备选用户的接收信号功率；
    根据所述第一预编码矩阵和所述第二预编码矩阵计算所述第一小区和所述相邻小区之间的小区间干扰功率；
    根据所述接收信号功率和所述小区间干扰功率计算信干噪比。
  6. 根据权利要求1至5中任一项所述的方法，其特征在于，所述预先为第一小区设置第一预编码模式包括：
    确定每个待分配资源上每个备选用户的统计信道特征；
    根据所述统计信道特征为相应的备选用户指定预编码矩阵；
    将所述预编码矩阵的信息记录在所述第一预编码模式中。
  7. 根据权利要求1至5中任一项所述的方法，其特征在于，所述向所述调度用户发送预编码后的信道估计信号和下行数据包括：
    向所述调度用户发送预编码后的信道估计信号；
    在接收到所述调度用户根据接收到的信道估计信号反馈的信道质量指示后，向所述调度用户发送预编码后的下行数据。
  8. 一种基站，其特征在于，包括：
    设置模块，用于预先为第一小区设置第一预编码模式，所述第一预编码模式记录有在待分配资源上为所述第一小区的备选用户指定的预编码矩阵的信息；
    调度模块，用于根据所述第一预编码模式从所述备选用户中为每个待分配资源选出调度用户；
    预编码模块，用于使用所述调度用户的预编码矩阵对信道估计信号和所述调度用户的下行数据进行预编码；及，
    发送模块，用于向所述调度用户发送预编码后的信道估计信号和下行数据。
  9. 根据权利要求8所述的基站，其特征在于，进一步包括：
    接收模块，用于接收相邻小区发送的第二预编码模式，所述第二预编码模式记录有所述相邻小区在待分配资源上使用的预编码矩阵的信息；
    所述调度模块包括：
    确定单元，用于针对每个待分配资源，根据所述第一预编码模式确定在该待分配资源上的备选用户以及为该备选用户指定的第一预编码矩阵；根据所述第二预编码模式确定所述相邻小区在该待分配资源上使用的第二预编码矩阵；
    计算单元，用于根据所述第一预编码矩阵和所述第二预编码矩阵计算在该待分配资源上的备选用户的吞吐量；
    调度单元，用于将吞吐量最大的备选用户确定为该待分配资源上的调度用户。
  10. 根据权利要求9所述的基站，其特征在于，所述确定单元用于：将所述第一预编码模式中为该待分配资源指定的备选用户划分为多个用户组；针对每个用户组，确定在所述第一预编码模式中记录的该用户组的每个备选用户的第一预编码矩阵；
    所述计算单元用于：利用所述第一预编码矩阵和所述第二预编码矩阵计算在该待分配资源上该备选用户的吞吐量；将该用户组中所有备选用户的吞吐量相加，作为在该待分配资源上的用户组的吞吐量；
    所述调度单元用于：将吞吐量最大的用户组确定为该待分配资源上的调度用 尸。
  11. 根据权利要求9所述的基站，其特征在于，所述确定单元用于：查找所述第二预编码模式中为该待分配资源预先设置的至少一个预编码矩阵，并将所述至少一个预编码矩阵加权求和得到所述第二预编码矩阵。
  12. 根据权利要求9所述的基站，其特征在于，所述计算单元用于：根据所述第一预编码矩阵计算所述备选用户的接收信号功率；根据所述第一预编码矩阵和所述第二预编码矩阵计算所述第一小区和所述相邻小区之间的小区间干扰功率；根据所述接收信号功率和所述小区间干扰功率计算信干噪比。
  13. 根据权利要求8至12中任一项所述的基站，其特征在于，所述设置模块用于：确定每个待分配资源上每个备选用户的统计信道特征；根据所述统计信道特征为相应的备选用户指定预编码矩阵；将所述预编码矩阵的信息记录在所述第一预编码模式中。
  14. 根据权利要求8至12中任一项所述的基站，其特征在于，所述发送模块用于：向所述调度用户发送预编码后的信道估计信号；在接收到所述调度用户根据接收到的信道估计信号反馈的信道质量指示后，向所述调度用户发送预编码后的下行数据。
  15. 一种基站，其特征在于，包括：
    存储器；
    一个或多个处理器；以及
    存储器中存储有由一个或多个处理器来执行的一个或多个指令单元，所述指令单元包括设置模块、调度模块、预编码模块和发送模块，其中，
    所述设置模块，用于预先为第一小区设置第一预编码模式，所述第一预编码模式记录有在待分配资源上为所述第一小区的备选用户指定的预编码矩阵的信息；
    所述调度模块，用于根据所述第一预编码模式从所述备选用户中为每个待分配资源选出调度用户；
    所述预编码模块，用于使用所述调度用户的预编码矩阵对信道估计信号和所述调度用户的下行数据进行预编码；及，
    所述发送模块，用于向所述调度用户发送预编码后的信道估计信号和下行数据。
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