WO2012055131A1 - 一种频分双工系统下行多用户多径波束赋形方法及装置 - Google Patents

一种频分双工系统下行多用户多径波束赋形方法及装置 Download PDF

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Publication number
WO2012055131A1
WO2012055131A1 PCT/CN2010/079715 CN2010079715W WO2012055131A1 WO 2012055131 A1 WO2012055131 A1 WO 2012055131A1 CN 2010079715 W CN2010079715 W CN 2010079715W WO 2012055131 A1 WO2012055131 A1 WO 2012055131A1
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user
paths
path
data transmission
base station
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PCT/CN2010/079715
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English (en)
French (fr)
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郭阳
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中兴通讯股份有限公司
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Classifications

    • 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
    • H04B7/046—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting taking physical layer constraints into account
    • H04B7/0473—Selection of precoding matrices or codebooks, e.g. using matrices antenna weighting taking physical layer constraints into account taking constraints in layer or codeword to antenna mapping into account
    • 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
    • H04B7/063—Parameters other than those covered in groups H04B7/0623 - H04B7/0634, e.g. channel matrix rank or transmit mode selection

Definitions

  • the present invention relates to the field of smart antenna beamforming technology, and more particularly to a FDD (Frequency Division Duplexing) system downlink multi-user multipath beamforming method and apparatus.
  • FDD Frequency Division Duplexing
  • MIMO Multiple Input and Multiple Output
  • LTE Long Term Evolution
  • LTE+ Long Term Evolution
  • multiple data streams can be simultaneously transmitted through multiple layers by designing appropriate weight vector of the transmitting antenna and the receiving antenna, and data of multiple layers can be transmitted in parallel, and the layer is removed. Interference.
  • the direction of the shaped beam can be designed by designing appropriate weight vectors of the transmitting antenna and the receiving antenna to distinguish multi-user signals and remove inter-user interference.
  • the method of beamforming distinguishes users by the orientation of the user, so that multiple users can reuse the same time and frequency resources. For small antenna spacing (0.5 ⁇ ), it is beneficial to control beam pointing, which is more suitable for applying beamforming technology. At the same time, the beamforming technique can also transmit the strongest directions of the same user's signal to take advantage of the strongest paths in the multipath channel environment.
  • the beamforming technology works mainly by controlling the beam direction, and is more suitable for suburban scenes that are used in the air. Beamforming can achieve significant beam energy gains that can extend cell coverage. At the same time, the beamforming technology can also be applied to complex urban environments.
  • the beam direction algorithm can utilize the direction of several strongest paths, and the channel matrix decomposition algorithm can use several paths with the best channel capacity.
  • Beamforming technology can obtain beam with characteristic direction by using antenna array structure, so obvious beam energy gain can be obtained, which can improve cell coverage and system capacity, and reduce system interference and Increasing system capacity, improving link reliability, and increasing peak rate, beamforming technology can effectively improve edge user performance.
  • existing single-stream beamforming techniques can be extended to multi-stream beamforming. Technology, still applicable to single users, thereby increasing user throughput.
  • the number of antennas on the base station side will be expanded to more than 8 and the number of antennas on the terminal side will be expanded to more than 4.
  • the number of layers used for beamforming and thereby utilizing spatial channel resources sufficiently and reasonably becomes an important issue.
  • the object of the present invention is to provide a downlink multi-user multipath beamforming method and device for a frequency division duplex system, which implements a multi-user multipath beamforming transmission technology in an FDD system, which can simultaneously transmit multiple users for multiple users. Data flow, enhancing user and system throughput.
  • the present invention provides a downlink multi-user multipath beamforming method for a frequency division duplex system, including:
  • the base station estimates multiple paths according to the uplink signal of each user, and determines a path that each user can use for data transmission according to a preset decision criterion;
  • the base station selects an optimal W path from all the paths that all users can use for data transmission according to the maximum transmission layer number W of each user, and performs each user on the selected W paths.
  • the maximum number of transmission layers W can be a small value between the number of transmitting antennas on the base station side and the number of receiving antennas.
  • the optimal W path may refer to the W paths with the largest gain multiple of the downlink signal reaching the receiving end.
  • the uplink signal may include: an uplink sounding RS pilot (SRS pilot); the preset decision criterion may be: if the signal-to-noise ratio of the receiving end of the downlink data of one path is greater than or equal to a preset threshold, determining the The path passed the test.
  • SRS pilot uplink sounding RS pilot
  • the preset decision criterion may be: if the signal-to-noise ratio of the receiving end of the downlink data of one path is greater than or equal to a preset threshold, determining the The path passed the test.
  • the determined number of paths that each user can use for data transmission may be less than or equal to the number of transmitting antennas on the base station side, and is less than or equal to the user receiving.
  • the feature vectors corresponding to the W paths may be respectively selected as the transmission weights used by the data streams of each path.
  • the present invention also provides a frequency division duplex system downlink multi-user multipath beamforming device, which is applied to a base station, and the device includes:
  • a decision module configured to respectively obtain a plurality of paths according to an uplink signal of each user, and determine a path that each user can use for data transmission according to a preset decision criterion
  • the multipath transmitting module is configured to select an optimal w path from all the paths available for data transmission of all users according to the maximum transmission layer number W of each user, and use the selected W paths Data transmission is performed for each user; where W is a positive integer, and W is a small value between the number of transmitting antennas on the base station side and the number of receiving antennas of the user.
  • the multipath transmitting module can be set to select the W paths with the largest gain multiple of the downlink signal reaching the receiving end as the optimal W paths.
  • the decision module may be configured to obtain k paths according to the uplink SRS pilot estimation of each user, and determine the path that each user can use for data transmission according to the following decision criterion: if the SNR of the receiving end of the downlink data of one path is greater than If it is equal to a preset threshold, it is determined that the path is a path that can be used for data transmission;
  • k is a positive integer
  • k is less than or equal to the number of transmitting antennas on the base station side, and is less than or equal to the number of antennas received by the user.
  • the multipath transmitting module may be further configured to select the feature vector corresponding to the W paths as the transmission right used by the data stream of each path when data transmission is performed for each user using the selected W paths. value.
  • the scheme can simultaneously transmit multiple data streams for multiple users, and utilize DOA of multipath signals in an FDD system.
  • FIG. 1 is a schematic diagram showing the principle of a multi-user beamforming method for an FDD system according to an embodiment of the present invention
  • FIG. 2 is a flow chart showing a multi-user beamforming method of an FDD system according to an embodiment of the present invention. Preferred embodiment of the invention
  • the uplink channel and the downlink channel are in different frequency bands, the uplink channel and the downlink channel do not have reciprocity, and the downlink channel information cannot be directly obtained through the uplink channel information, that is, the information of the downlink channel matrix cannot be obtained by the base station side.
  • the present invention proposes a downlink multi-user beamforming strategy scheme suitable for an FDD system.
  • the main idea of the scheme is that, in view of the limitations of the above-mentioned characteristics of the FDD system, the present invention considers the use of angle classes.
  • the beamforming method that is, the eNB (evolved Node B) estimates the signal peaks from multiple angles according to the uplink signal of each user, and the signals from multiple angles can be understood as multiple paths from the space. Signal, and according to the information such as the gain of these multiple paths, the path for each user to be used for data transmission is detected; finally, the required number of paths with the largest gain multiple is selected from all the paths of all users to perform data. Transmission, which realizes multi-path beamforming downlink signal transmission for multiple users.
  • the present invention provides a downlink multi-user multipath beamforming method for a frequency division duplex system, which specifically uses the following technical solutions:
  • the base station estimates multiple paths according to the uplink signal of each user, and determines a path that each user can use for data transmission according to a preset decision criterion;
  • the base station selects an optimal W path from all the paths that all users can use for data transmission according to the maximum transmission layer number W of each user, and uses the W paths to count each user. According to transmission; where W is a positive integer.
  • the maximum transmission layer number W is a small value between the number of base station side transmit antennas and the number of user receive antennas.
  • the optimal path refers to the path with the largest gain multiplier of the downlink signal reaching the receiving end.
  • the base station estimates multiple power peaks of the uplink signal by using a MUSIC (Multiple Signal Classification) algorithm or a CAPON algorithm, and obtains corresponding multiple paths.
  • MUSIC Multiple Signal Classification
  • CAPON CAPON
  • the uplink signal includes: an uplink sounding RS pilot (SRS pilot).
  • SRS pilot uplink sounding RS pilot
  • the decision criterion is: if the signal-to-noise ratio of the receiver after the arrival of the data of one path reaches the receiving end is greater than a preset threshold, it is determined that the path passes the check.
  • the feature vectors corresponding to the W paths are respectively selected as the transmission weights used by the data streams of each path.
  • SNR TX Transmitting side signal to noise ratio
  • the gain multiple of the signal of the first path estimated by the uplink signal reaches the receiving end is ⁇ ⁇ ; the gain multiple of the signal of the second path reaches the receiving end is ⁇ 2 ; the gain multiple of the signal of the f-th path reaches the receiving end is ⁇ /.
  • the signal-to-noise ratio of the data of layer 1 after reaching the receiving end is SNR TX "
  • the signal-to-noise ratio of the data of layer 2 after reaching the receiving end is SNR.
  • the signal-to-noise ratio of the data of the TX layer f reaches the receiving end is SNR. TX .
  • the decision criterion for determining whether a layer (path) can be used for data transmission is: whether the signal to noise ratio of the layer data after reaching the receiving end is greater than the threshold value SMfe, that is, when a layer of data arrives at the receiving end If the signal-to-noise ratio after the end is greater than the threshold SN fe, the data of this layer can be considered. Can be decoded normally, this layer can be transmitted. When the signal-to-noise ratio of the data of the k layers reaches the receiving end is greater than the threshold SNRRX, a total of k layers are simultaneously transmitted.
  • the data transmission may be performed by selecting the largest multiple of the W gains ⁇ , and the feature vector corresponding to the largest diameter of the W gains ⁇ is used as the transmission weight used by the data stream of each path. That is, each path corresponds to a unique angle, and each angle corresponds to a unique transmission weight, such as an angle of +30 degrees, and the corresponding weight is [1 j -1 -j].
  • FIG. 1 is a schematic diagram of a transmission link involved in the solution of the present invention.
  • the data of the W layers are hierarchically scheduled, and mapping between multiple users and data streams is performed, and each data stream is added with a dedicated pilot. Then multiply by the transmission weight vector and map to multiple transmit antennas, and then reach the multiple user equipments through the spatial channel.
  • FIG. 2 is a schematic flow chart of a downlink multi-user multipath beamforming scheme of a frequency division duplex system according to an embodiment of the present invention, and the specific implementation steps are as follows:
  • Step 1 The eNB can estimate the DOA angle of the user's path according to the uplink sounding RS pilot (SRS pilot), where it is necessary to estimate the angles of multiple paths from the user's uplink signal power peak. Degree, and record multiple angles as DOAl, DOA2, —DOAf. Algorithms such as the MUSIC algorithm and the CAPON algorithm can be used here.
  • SRS pilot uplink sounding RS pilot
  • Step 2 Estimate the peaks of signals from multiple angles.
  • Signals from multiple angles can be understood as signals from multiple paths in space. At the same time, the signal strength from each path is detected and estimated at each path. The multiple of the gain of the downstream signal of the direction after reaching the receiving end. ⁇ , . ⁇
  • the k paths of data transmission are made to determine the k direction angles DOAl, DOA2, ... DOAk for which data transmission is possible.
  • Step 4 Integrate all users to determine which path data can be transmitted. From all the paths of all users, select W paths for data transmission.
  • the data of the multiple gains of ⁇ can be selected from all the paths of all users for the data transmission, and the feature vector corresponding to the W gains is selected as the transmission weight used by the data stream of this layer.
  • Step 5 According to DOA1 DOA2 ... DOAw, the W-row transmission weights W1 W2 ... Ww can be obtained respectively, and the beam direction corresponding to the Wl weight vector is DOA1, and the beam direction corresponding to the W2 weight vector is DOA2, Ww weight The beam direction corresponding to the value vector is DOAw.
  • Step 6 Perform orthogonalization on Wl, W2, ... Ww, and then normalize to obtain transmission weights Wl, W2', - Ww' which are mutually orthogonal and have a modulus value of 1.
  • the directions of the beams corresponding to W2, - Ww' and W2... Ww are basically the same, and the performance is similar.
  • the advantage of orthogonalization is that Wl, W2', - Ww' are orthogonal to each other, reducing the interference between the two data streams, so W2, - Ww' is used instead of W2, ... Ww First
  • the data streams from 2 to W paths are weighted.
  • Step 7 Encode and modulate the data stream with the transmission direction of DOAl ⁇ DOAw.
  • Step 8 Load the Dedicated Reference Signal (DRS) of each layer corresponding to each path in the data stream with the transmission direction of DOAl ⁇ DOAw.
  • DRS Dedicated Reference Signal
  • Step 9 Multiply the data stream with the transmit direction DOAl ⁇ DOAw by the corresponding transmit weight, that is, multiply the corresponding transmit weight Wl W2, - Ww' to map the data to the transmit antenna and pass through the antenna.
  • the spatial signal is transmitted to complete the beamforming process.
  • Step 10 Each receiving end, that is, the User Equipment (UE) side, performs signal demodulation according to the dedicated pilot.
  • UE User Equipment
  • the embodiment of the present invention further provides a downlink multi-user multipath beamforming device for a frequency division duplex system, which is applied to a base station, and the device mainly includes the following functional modules:
  • a decision module configured to respectively obtain a plurality of paths according to an uplink signal of each user, and determine a path that each user can use for data transmission according to a preset decision criterion
  • a multipath transmitting module which is configured to select an optimal w paths from all the paths available for data transmission of all users according to the maximum transmission layer number W of each user, and use the W path pairs The user performs data transmission; where W is a positive integer, and W is a small value between the number of transmitting antennas on the base station side and the number of receiving antennas of the user.
  • the optimal W path selected by the multipath transmitting module refers to the W paths with the largest gain multiple of the downlink signal reaching the receiving end.
  • the determining module is configured to obtain k paths according to the uplink SRS pilot estimation of the user, and determine the path that the user can use for data transmission according to the following decision criterion: if the downlink data of one path If the SNR of the receiving end is greater than or equal to a preset threshold, it is determined that the path is a path that can be used for data transmission;
  • k is a positive integer
  • k is less than or equal to the number of base station side transmit antennas, and is less than or equal to the number of user receive antennas.
  • the multipath transmitting module is further configured to select feature vectors corresponding to the W paths as data of each path when data transmission is performed on each user by using the W paths.
  • the emission weight used by the stream is further configured to select feature vectors corresponding to the W paths as data of each path when data transmission is performed on each user by using the W paths.
  • modules or steps of the present invention may be Implemented by a general-purpose computing device, which may be centralized on a single computing device or distributed over a network of computing devices, optionally, they may be implemented by program code executable by the computing device, such that They may be stored in a storage device by a computing device, and in some cases, the steps shown or described may be performed in an order different than that herein, or separately fabricated into individual integrated circuit modules. Alternatively, multiple modules or steps of them can be implemented as a single integrated circuit module. Thus, the invention is not limited to any specific combination of hardware and software.
  • the present invention can simultaneously transmit multiple data streams for multiple users, and multi-stream transmission using the DOA angle of the multipath signal in the FDD system, increasing the throughput of users and systems. .

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Description

一种频分双工系统下行多用户多径波束赋形方法及装置
技术领域
本发明涉及智能天线波束赋形技术领域， 更具体地， 涉及一种 FDD ( Frequency Division Duplexing, 频分双工） 系统下行多用户多径波束赋形方 法及装置。 背景技术
MIMO ( Multiple Input and Multiple Output, 多输入多输出） 系统由于其 能够有效提高信道容量而成为 LTE ( Long Term Evolution, 长期演进 )、 LTE+ 的研究中一项倍受人们关注的技术。
在单用户 MIMO模式中， 可以通过设计合适的发射天线和接收天线的权 值矢量来对多个数据流通过多个层同时进行传输， 并可以使多个层的数据之 间并行传输， 去除层间干扰。
在多用户 MIMO模式中， 可以通过设计合适的发射天线和接收天线的权 值矢量来设计赋形波束的方向， 区分多用户的信号， 去除用户间干扰。
波束赋形的方法通过用户所在方位来区分用户， 从而可以实现多个用户 复用相同的时间、 频率资源。 对于小天线间距（0.5λ ) 情况有利于控制波束 指向， 更加适合于应用波束赋形 （Beamforming )技术。 同时波束赋形技术也 可以对同一个用户的信号最强的几个方向进行传输， 以利用多径信道环境中 最强的几条径。
波束赋形技术主要是通过控制波束方向来进行工作的， 比较适合用于空 旷的郊区场景。 波束赋形可以获得明显的波束能量增益， 可以扩大小区的覆 盖。 同时波束赋形技术也可以用于复杂的城区环境， 利用波束方向类的算法 可以利用信号最强的几个径的方向， 利用信道矩阵分解类的算法可以使用信 道容量最好的几条径。
波束赋形技术利用天线阵列结构可以获得特征方向的波束， 因此可以获 得明显的波束能量增益， 这可以完善小区覆盖和系统容量， 减小系统干扰和 增加系统容量， 提高链路可靠性， 提高峰值速率， 波束赋形技术可以有效的 改善边沿用户的性能，对于 LTE+系统来说，可以将现有的单流波束赋形技术 扩展至多流波束赋形技术， 仍然适用于单用户， 从而提高用户的吞吐量。
对于即将开始制定的 3GPP ( Third Generation Partnership Project, 第三代 合作伙伴计划） Rel-10标准来说， 基站侧天线数目将会扩展至 8个以上， 终 端侧天线数目将会扩展至 4个以上， 对于未来的波束赋形技术来说， 控制波 束赋形所使用的层数并从而充分并合理得利用空间信道资源成为重要的课 题。 发明内容
本发明的目的是提供一种频分双工系统下行多用户多径波束赋形方法及 装置， 在 FDD系统中实现多用户的多径波束赋形传输技术， 能够为多个用户 同时发送多个数据流， 增强用户及系统的吞吐量。
为解决上述技术问题， 本发明提供了一种频分双工系统下行多用户多径 波束赋形方法， 包括：
基站分别根据每个用户的上行信号估计得到多个径， 并根据预先设定的 判决准则确定各用户可以用于数据传输的径；
所述基站根据每个用户的最大传输层数 W, 从所有用户的所有可以用于 数据传输的径中选出最优的 W个径， 并使用所选出的 W个径对每个用户进 行数据传输； 其中， W为正整数。
最大传输层数 W 可以为基站侧发射天线数与用户接收天线数之间的较 小值。
最优的 W个径可以是指下行信号到达接收端的增益倍数最大的 W个径。 上行信号可以包括： 上行 sounding RS导频（SRS导频）； 预先设定的判 决准则可以为： 若一个径的下行数据的接收端信噪比大于等于预先设定的门 限值， 则判定该径通过检验。
基站在确定各用户可以用于数据传输的径时， 确定的每个用户可以用于 数据传输的径的个数可以小于等于基站侧发射天线数， 且小于等于用户接收 基站使用所选出的 W个径对每个用户进行数据传输时，可分别选择所述 W个径所对应的特征向量作为每个径的数据流所使用的发射权值。
本发明还提供了一种频分双工系统下行多用户多径波束赋形装置， 应用 于基站， 所述装置包括：
判决模块， 其设置成分别根据每个用户的上行信号估计得到多个径， 并 根据预先设定的判决准则确定各用户可以用于数据传输的径；
多径发射模块， 其设置成根据每个用户的最大传输层数 W, 从所有用户 的所有可以用于数据传输的径中选出最优的 w个径， 并使用所选出的 W个 径对每个用户进行数据传输； 其中， W为正整数， 且 W为基站侧发射天线数 与用户接收天线数之间的较小值。
多径发射模块可设置成选择下行信号到达接收端的增益倍数最大的 W 个径作为最优的 W个径。
判决模块可设置成根据每个用户的上行 SRS导频估计得到 k个径， 并可 根据以下判决准则确定各用户可以用于数据传输的径： 若一个径的下行数据 的接收端信噪比大于等于预先设定的门限值， 则判定该径为可以用于数据传 输的径；
其中， k为正整数， k小于等于基站侧发射天线数， 且小于等于用户接收 天线数。
多径发射模块还可设置成在使用所选出的 W个径对每个用户进行数据 传输时，分别选择所述 W个径所对应的特征向量作为每个径的数据流所使用 的发射权值。
与现有技术相比， 本发明提供的上述方案至少具有如下有益效果： 该方 案可以为多个用户同时发送多个数据流，在 FDD系统中利用多径信号的 DOA
( Direction of Arrival , 波达方向） 角而进行多数据流传输， 增加了用户和系 统的吞吐量。
附图概述 此处所说明的附图用来提供对本发明的进一步理解， 构成本申请的一部 分， 本发明的示意性实施例及其说明用于解释本发明， 并不构成对本发明的 不当限定。 在附图中：
图 1 为依据本发明实施例的 FDD 系统多用户波束赋形方法的原理示意 图；
图 2为依据本发明实施例的 FDD 系统多用户波束赋形方法的流程示意 图。 本发明的较佳实施方式
在 FDD系统中， 由于上行信道与下行信道所处不同的频段， 上行信道与 下行信道不具有互易性， 无法通过上行信道信息直接获得下行信道信息， 即 基站侧无法获得下行信道矩阵的信息， 无法使用信道矩阵做特征值分解而得 到波束赋形发射权值的方法。 即无法使用这种最优的、 最大限度利用信道容 量的方法。
针对现有技术存在的上述问题，本发明提出一种适用于 FDD系统的下行 多用户波束赋形策略方案， 该方案的主要思想在于， 鉴于 FDD系统具有上述 特性的限制，本发明考虑使用角度类的波束赋形方法，即： eNB ( evolved Node B,演进型基站）根据每一个用户的上行信号估计得到来自多个角度的信号峰 值， 而来自多个角度的信号可以理解为来自空间多个径的信号， 并根据这些 多个径的增益等信息， 检测出每个用户适用于进行数据传输的径； 最后从所 有用户的所有径中选出增益倍数最大的所需个数的径来进行数据传输， 实现 对多用户进行多径波束赋形下行信号的传输。
基于上述思想， 本发明提供一种频分双工系统下行多用户多径波束赋形 方法， 具体釆用如下技术方案：
基站分别根据每个用户的上行信号估计得到多个径， 并根据预先设定的 判决准则确定各用户可以用于数据传输的径；
所述基站根据每个用户的最大传输层数 W, 从所有用户的所有可以用于 数据传输的径中选出最优的 W个径， 并使用所述 W个径对每个用户进行数 据传输； 其中， W为正整数。 其中，所述最大传输层数 W为基站侧发射天线数与用户接收天线数之间 的较小值。
其中， 最优的径是指下行信号到达接收端的增益倍数最大的径。
进一步地， 所述基站通过 MUSIC ( Multiple Signal Classification, 多重信 号分类）算法或 CAPON算法估计出所述上行信号的多个功率峰值， 并得出 相应的多个径。
进一步地， 所述上行信号包括： 上行 sounding RS导频（ SRS导频） 。 进一步地， 所述判决准则为： 若一个径的数据到达接收端后的接收端信 噪比大于预先设定的门限值， 则判定该径通过检验。
进一步地， 基站使用所述 W个径对所述每个用户进行数据传输时， 分别 选择所述 W个径所对应的特征向量作为每个径的数据流所使用的发射权值。
本发明上述方案中涉及如下几个参量。
1 )发射侧信噪比： SNRTX, 该值为发射端的已知值。
2 )使得接收正确块率（即 1-BLER (误块率） ）达到 P ( P的优选值为 70% ) 时的接收信噪比： SNRRX, SN fe即为接收误块率达到 P的信噪比门限 值， 该门限值通常也为已知值。
3 )通过上行信号估计得到的第一条径的信号到达接收端的增益倍数为 λι ; 第二条径的信号到达接收端的增益倍数为 λ2; 第 f条径的信号到达接收端 的增益倍数为 λ/。
根据以上参量， 层 1的数据到达接收端后的信噪比为 SNRTX" , 层 2的 数据到达接收端后的信噪比为 SNRTX 层 f 的数据到达接收端后的信噪比 为 SNRTX 。
根据以上方案， 判决一层（径）是否通过检验能够用于数据传输的判决 准则为： 层的数据到达接收端后的信噪比是否大于门限值 SMfe, 即当某一 层的数据到达接收端后的信噪比大于门限值 SN fe时， 则可认为此层的数据 可以正常解码， 这一层可以进行传输。 当有 k个层的数据到达接收端后的信 噪比大于门限值 SNRRX时， 则共有 k个层同时进行传输。
然后， 综合所有用户决定哪些径（层） 的数据可以进行传输。 对于每一 个用户而言， 已经决定了有 k个层可以进行传输， 但是当所有用户的传输层 数加起来大于 W时， 就会有数据流难以解码， 这是因为用户之间的干扰所导 致的。
通常来说， 每个用户的数据流数目之和需要小于基站侧发射天线数与每 个用户接收天线数之间的较小值。 假设基站侧发射天线数目为 N, 每个用户 的接收天线数目为 M。 则 W的优选值为 f, f=min ( M, N ) , 即 f为 M与 N 的较小值。
因此， 只需要从所有用户的所有径中， 共选出 W个最优的径用于数据传 输。 优选地， 可以选取 W个增益的倍数 λ最大的径进行数据传输， 并使用这 W个增益的倍数 λ最大的径所对应的特征向量作为每个径的数据流所使用的 发射权值。 即， 每个径对应唯一的角度， 每个角度对应唯一的发射权值， 比 如 +30度的角度， 对应的权值就是【1 j -1 -j】 。
为了便于阐述本发明， 以下将结合附图及具体实施例对本发明技术方案 的实施作进一步详细描述。 需要说明的是， 在不冲突的情况下， 本申请中的 实施例及实施例中的特征可以相互任意组合。
图 1示出了本发明方案所涉及的发射链路的示意图， W个层的数据经过 高层调度， 进行多个用户与数据流之间的映射， 每个数据流加上各自的专用 导频， 再分别乘以发射权值矢量后映射至多根发射天线， 通过空间信道后到 达多个用户设备。
图 2示出了本发明实施例的频分双工系统下行多用户多径波束赋形方案 的流程示意图， 其具体实施步骤描述如下：
第一步： eNB可以根据上行 sounding RS导频（ SRS导频）估计用户的径 的 DOA角度，这里需要估计得到来自用户的上行信号功率峰值的多个径的角 度， 并将多个角度分别记为 DOAl、 DOA2、 —DOAf。 这里可以使用 MUSIC 算法、 CAPON算法等算法。
第二步： 估计得到来自多个角度的信号峰值， 来自多个角度的信号可以 理解为来自空间多个径的信号， 同时检测得到来自每个径的信号强度， 从而 估计得到在每条径的方向的下行信号到达接收端后的增益的倍数 . λ^ , .λ^ 第三步： 使用判决准则 （层的数据到达接收端后的信噪比是否大于门限 值 SNRRX ")得到可以用来做数据传输的 k个径， 从而确定出可以进行数据传 输的 k个方向角 DOAl、 DOA2、 ...DOAk。
第四步： 综合所有用户决定哪些径的数据可以进行传输， 从所有用户的 所有径中， 共选出 W个径用于数据传输。
可以从所有用户的所有径中选取 W个增益的倍数 λ最大的径进行数据传 输，选择这 W个增益 所对应的特征向量作为这个层的数据流所使用的发射 权值。
第五步： 根据 DOA1 DOA2 ... DOAw可以分别得到 W列发射权值 W1 W2 ... Ww , Wl权值矢量对应的波束方向为 DOA1 , W2权值矢量对应的波 束方向为 DOA2 , Ww权值矢量对应的波束方向为 DOAw。
第六步： 对 Wl、 W2、 ... Ww进行正交化处理， 再进行归一化， 得到相 互正交的且模值为 1的发射权值 Wl、 W2' 、 - Ww' 。
其中， W2， - Ww' 与 W2... Ww所对应的波束的方向基本相同， 性能 相近。 进行正交化处理的优势在于 Wl、 W2' 、 - Ww' 之间两两相互正交， 减少了两个数据流间的干扰， 因此用 W2， 、 - Ww' 代替 W2、 ... Ww对第
2个至第 W个径的数据流进行加权。
第七步： 对发射方向为 DOAl~DOAw的数据流进行编码、 调制。
第八步：对发射方向为 DOAl~DOAw的数据流分别加载每个径所对应层 各自的专用导频（ Dedicated Reference Signal, 简称为 DRS ) 。
第九步： 对发射方向为 DOAl~DOAw 的数据流分别乘以相应的发射权 值， 即乘以相应的发射权值 Wl W2， - Ww' ，从而将数据映射至发射天线， 并通过天线进行空间信号发送， 完成波束赋形过程。 第十步： 每个接收端即用户设备 ( User Equipment , 简称为 UE )侧根据 专用导频进行信号解调。
此外， 本发明实施例中还提供了一种频分双工系统下行多用户多径波束 赋形装置， 应用于基站， 该装置主要包括以下功能模块：
判决模块， 其设置成分别根据每个用户的上行信号估计得到多个径， 并 根据预先设定的判决准则确定各用户可以用于数据传输的径；
多径发射模块， 其设置成根据每个用户的最大传输层数 W, 从所有用户 的所有可以用于数据传输的径中选出最优的 w个径， 并使用所述 W个径对 每个用户进行数据传输； 其中， W为正整数， 且 W为基站侧发射天线数与用 户接收天线数之间的较小值。
进一步地， 所述多径发射模块选出的最优的 W个径， 是指下行信号到达 接收端的增益倍数最大的 W个径。
进一步地， 所述判决模块是设置成根据所述用户的上行 SRS导频估计得 到 k个径， 并才艮据以下判决准则确定所述用户可以用于数据传输的径： 若一 个径的下行数据的接收端信噪比大于等于预先设定的门限值， 则判定该径为 可以用于数据传输的径；
其中， k为正整数， k小于等于基站侧发射天线的个数， 且小于等于用户 接收天线的个数。
进一步地，所述多径发射模块还设置成在使用所述 W个径对所述每个用 户进行数据传输时，分别选择所述 W个径所对应的特征向量作为所述每个径 的数据流所使用的发射权值。
以上仅为本发明的优选实施案例而已， 并不用于限制本发明， 本发明还 可有其他多种实施例， 在不背离本发明精神及其实质的情况下， 熟悉本领域 的技术人员可根据本发明做出各种相应的改变和变形， 但这些相应的改变和 变形都应属于本发明所附的权利要求的保护范围。
显然， 本领域的技术人员应该明白， 上述的本发明的各模块或各步骤可 以用通用的计算装置来实现， 它们可以集中在单个的计算装置上， 或者分布 在多个计算装置所组成的网络上， 可选地， 它们可以用计算装置可执行的程 序代码来实现， 从而， 可以将它们存储在存储装置中由计算装置来执行， 并 且在某些情况下， 可以以不同于此处的顺序执行所示出或描述的步骤， 或者 将它们分别制作成各个集成电路模块， 或者将它们中的多个模块或步骤制作 成单个集成电路模块来实现。 这样， 本发明不限制于任何特定的硬件和软件 结合。
工业实用性 与现有技术相比， 本发明可以为多个用户同时发送多个数据流， 在 FDD 系统中利用多径信号的 DOA角而进行多数据流传输，增加了用户和系统的吞 吐量。

Claims

权 利 要 求 书
1、 一种频分双工系统下行多用户多径波束赋形方法， 包括：
基站分别根据每个用户的上行信号估计得到多个径， 并根据预先设定的 判决准则确定各用户可以用于数据传输的径；
所述基站根据每个用户的最大传输层数 W, 从所有用户的所有可以用于 数据传输的径中选出最优的 W个径， 并使用所选出的 W个径对每个用户进 行数据传输； 其中， W为正整数。
2、 如权利要求 1所述的方法， 其中，
所述最大传输层数 W为基站侧发射天线数与用户接收天线数中的较小 值。
3、 如权利要求 1所述的方法， 其中，
所述最优的 W个径是指下行信号到达接收端的增益倍数最大的 W个径。
4、 如权利要求 1所述的方法， 其中，
所述上行信号包括： 上行 Sounding RS导频；
所述预先设定的判决准则为： 若一个径的下行数据的接收端信噪比大于 等于预先设定的门限值， 则判定该径通过检验。
5、 如权利要求 2所述的方法， 其中，
确定各用户可以用于数据传输的径的步骤中， 确定的每个用户可以用于 数据传输的径的个数小于等于基站侧发射天线数， 且小于等于所述用户接收 天线数。
6、 如权利要求 1、 2、 3或 4所述的方法， 其中，
使用所选出的 W个径对每个用户进行数据传输的步骤中，所述基站分别 选择所述 W个径所对应的特征向量作为每个径的数据流所使用的发射权值。
7、 一种频分双工系统下行多用户多径波束赋形装置， 其特征在于， 所述 装置应用于基站， 所述装置包括：
判决模块， 其设置成分别根据每个用户的上行信号估计得到多个径， 并 根据预先设定的判决准则确定各用户可以用于数据传输的径； 多径发射模块， 其设置成根据每个用户的最大传输层数 W, 从所有用户 的所有可以用于数据传输的径中选出最优的 w个径， 并使用所选出的 W个 径对每个用户进行数据传输； 其中， W为正整数， 且 W为基站侧发射天线数 与用户接收天线数之间的较小值。
8、 如权利要求 7所述的装置， 其中，
所述多径发射模块是设置成选出下行信号到达接收端的增益倍数最大的 W个径作为所述最优的 W个径。
9、 如权利要求 7所述的装置， 其中，
所述判决模块是设置成根据每个用户的上行 Sounding RS导频估计得到 k 个径， 并根据以下判决准则确定所述各用户可以用于数据传输的径： 若一个 径的下行数据的接收端信噪比大于等于预先设定的门限值， 则判定该径为可 以用于数据传输的径；
其中， k为正整数， k小于等于基站侧发射天线数， 且小于等于所述用户 接收天线数。
10、 如权利要求 7、 8或 9所述的装置， 其中，
所述多径发射模块还设置成在使用所选出的 W个径对每个用户进行数 据传输时，分别选择所述 W个径所对应的特征向量作为每个径的数据流所使 用的发射权值。
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