CN102938666B

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Info

Publication number: CN102938666B
Application number: CN201210454981.8A
Authority: CN
Inventors: 王燕敏; 肖立民; 冯伟; 许希斌; 周世东; 赵明
Original assignee: Tsinghua University
Current assignee: Tsinghua University
Priority date: 2012-11-13
Filing date: 2012-11-13
Publication date: 2015-02-18
Anticipated expiration: 2032-11-13
Also published as: CN102938666A

Abstract

本发明提供一种下行多小区联合波束成形方法，该方法包括：各个用户根据接收到的信号估计自身的信道状态信息，并将信道状态信息反馈给本小区的中心处理器，所述信道状态信息包括本小区内各个分布式放置的天线单元到用户自身的即时信道状态信息和其他小区分布式放置的天线单元到用户自身的大尺度信道状态信息；各个小区的中心处理器将收到的信道状态信息转发给集中处理节点；基于接收到的信道状态信息，集中处理节点按照选定的优化目标，优化计算出小区中各个用户的发送波束成形向量。本发明提出的基于部分信道状态信息的下行多小区波束成形方法可以在提高系统性能的同时有效降低导频开销、信道估计开销以及反馈开销。

The present invention provides a downlink multi-cell joint beamforming method. The method includes: each user estimates its own channel state information according to the received signal, and feeds back the channel state information to the central processor of the cell. The channel state information Including the real-time channel state information from each distributed antenna unit in the cell to the user itself and the large-scale channel state information from the distributed antenna units in other cells to the user itself; the channel state information received by the central processor of each cell The information is forwarded to the centralized processing node; based on the received channel state information, the centralized processing node optimizes and calculates the transmit beamforming vector of each user in the cell according to the selected optimization objective. The downlink multi-cell beamforming method based on partial channel state information proposed by the present invention can effectively reduce pilot overhead, channel estimation overhead and feedback overhead while improving system performance.

Description

Translated fromChinese

一种下行多小区联合波束成形方法A downlink multi-cell joint beamforming method

技术领域technical field

本发明涉及本发明属于无线数据传输技术领域，特别涉及一种基于部分信道状态信息的下行多小区联合波束成形方法。The present invention relates to the technical field of wireless data transmission, and in particular to a downlink multi-cell joint beamforming method based on partial channel state information.

背景技术Background technique

在第二代以及第三代无线通信系统中，蜂窝技术被广泛采用。为了提高蜂窝系统中小区边缘用户的性能，分布式天线系统（DistributedAntenna System，DAS）、基站协作系统、分布式无线通信系统（Distributed Wireless Communication System，DWCS）等新型网络架构技术以及多点协作（Coordinated Multi-Point，CoMP）技术被相继提出。这些技术体现了未来无线通信系统的重要特征：“分布式天线放置”和“协作信号处理”。In the second and third generation wireless communication systems, cellular technology is widely used. In order to improve the performance of cell edge users in the cellular system, new network architecture technologies such as distributed antenna system (Distributed Antenna System, DAS), base station cooperation system, distributed wireless communication system (Distributed Wireless Communication System, DWCS) and coordinated multi-point (Coordinated Multi-Point, CoMP) technology has been proposed one after another. These techniques embody important features of future wireless communication systems: "distributed antenna placement" and "cooperative signal processing".

由于复杂度过高，全系统的全局联合信号处理在实际中很难实现。一种比较可行的架构是将系统中分布式放置的天线单元分成一个个的广义小区，每个小区内部各个天线的信号在本小区的中心处理器中联合处理，而不同小区间采用相对简单的协作方式，如协同资源分配等。对于下行链路，多小区联合波束成形可以有效降低小区间干扰，提高系统性能。在多小区联合波束成形方案的设计中，发送端的信道状态信息（Channel State Information，CSI）起着非常重要的作用，发送端CSI数量的不同对系统的性能有着很大的影响。Due to the high complexity, the global joint signal processing of the whole system is difficult to realize in practice. A more feasible architecture is to divide the distributed antenna units in the system into generalized cells. The signals of each antenna in each cell are jointly processed in the central processor of the cell, and a relatively simple method is used between different cells. Collaboration methods, such as collaborative resource allocation, etc. For the downlink, multi-cell joint beamforming can effectively reduce inter-cell interference and improve system performance. In the design of the multi-cell joint beamforming scheme, the channel state information (Channel State Information, CSI) at the sending end plays a very important role, and the difference in the number of CSI at the sending end has a great impact on the performance of the system.

一般而言，我们可以认为无线信道的衰落包括两部分：一是大尺度衰落，包括路径损耗和阴影衰落；二是小尺度衰落，即瑞利衰落。小尺度衰落变化快，难以实时跟踪，而大尺度衰落变化缓慢，比较容易获取。在实际系统中，特别是系统规模比较大时，在发送端获取全部即时CSI（包括大尺度CSI和小尺度CSI）会给系统带来相当大的导频开销、信道估计开销以及反馈开销。Generally speaking, we can think that the fading of wireless channels includes two parts: one is large-scale fading, including path loss and shadow fading; the other is small-scale fading, namely Rayleigh fading. Small-scale fading changes quickly and is difficult to track in real time, while large-scale fading changes slowly and is relatively easy to obtain. In an actual system, especially when the system scale is relatively large, obtaining all real-time CSI (including large-scale CSI and small-scale CSI) at the transmitter will bring considerable pilot overhead, channel estimation overhead, and feedback overhead to the system.

发明内容Contents of the invention

（一）所要解决的技术问题(1) Technical problems to be solved

本发明目的是提供一种下行多小区联合波束成形方法，解决系统导频开销、信道估计开销以及反馈开销相当大的问题。The purpose of the present invention is to provide a downlink multi-cell joint beamforming method to solve the problem that the system pilot overhead, channel estimation overhead and feedback overhead are quite large.

（二）技术方案(2) Technical solutions

本发明提供一种下行多小区联合波束成形方法，该方法包括：The present invention provides a downlink multi-cell joint beamforming method, the method comprising:

S1、各个用户根据接收到的信号估计自身的信道状态信息，并将信道状态信息反馈给本小区的中心处理器；所述信道状态信息包括本小区内各个分布式放置的天线单元到用户自身的即时信道状态信息和其他小区分布式放置的天线单元到用户自身的大尺度信道状态信息；S1. Each user estimates its own channel state information according to the received signal, and feeds the channel state information back to the central processor of the cell; the channel state information includes the distributed antenna units in the cell to the user itself Real-time channel state information and large-scale channel state information from antenna units distributed in other cells to the user itself;

S2、各个小区的中心处理器将收到的信道状态信息转发给集中处理节点；S2. The central processors of each cell forward the received channel state information to the centralized processing node;

S3、基于接收到的信道状态信息，集中处理节点按照预定的优化目标，优化计算出小区中各个用户的发送波束成形向量。S3. Based on the received channel state information, the centralized processing node optimizes and calculates the transmit beamforming vector of each user in the cell according to a predetermined optimization goal.

可选的，该方法还包括集中处理节点将计算出的波束成形向量分发给各个小区的中心处理器，各个小区的中心处理器对相应用户的波束成形向量进行预处理的步骤。Optionally, the method further includes a step in which the centralized processing node distributes the calculated beamforming vectors to the central processors of each cell, and the central processors of each cell preprocess the beamforming vectors of corresponding users.

（三）有益效果(3) Beneficial effects

本发明的目的在于提出一种基于部分信道状态信息的下行多小区联合波束成形方法，适用于每小区有多个分布式放置的远端天线单元以及多个用户的多小区无线通信系统，可以在提高系统性能的同时有效降低导频开销、信道估计开销以及反馈开销。The purpose of the present invention is to propose a downlink multi-cell joint beamforming method based on partial channel state information, which is applicable to a multi-cell wireless communication system with multiple distributed remote antenna units and multiple users in each cell, and can be used in While improving system performance, it effectively reduces pilot overhead, channel estimation overhead, and feedback overhead.

附图说明Description of drawings

图1为本发明的步骤流程图；Fig. 1 is a flow chart of steps of the present invention;

图2为有3个小区的DWCS系统示意图。Fig. 2 is a schematic diagram of a DWCS system with 3 cells.

具体实施方式Detailed ways

本发明的目的在于提供一种基于发送端部分CSI—各个小区内部即时CSI和小区间大尺度CSI—的下行多小区联合波束成形方法，适用于每小区有多个分布式放置的远端天线单元且每小区有多个用户的多小区无线通信系统。如图1所示该方法包括：The purpose of the present invention is to provide a downlink multi-cell joint beamforming method based on partial CSI at the transmitting end—instantaneous CSI inside each cell and large-scale CSI between cells—applicable to multiple distributed remote antenna units in each cell And each cell has a multi-cell wireless communication system with multiple users. As shown in Figure 1, the method includes:

S3、基于接收到的信道状态信息，集中处理节点按照选定的优化目标，优化计算出小区中各个用户的发送波束成形向量。S3. Based on the received channel state information, the centralized processing node optimizes and calculates the transmit beamforming vector of each user in the cell according to the selected optimization target.

其中信道状态信息估计分为：The channel state information estimation is divided into:

1）对应于小区内即时信道状态信息的导频插入周期和信道估计周期短，要足以跟踪即时信道状态信息的快速变化；1) The pilot insertion period and channel estimation period corresponding to the real-time channel state information in the cell are short, which is enough to track the rapid changes of the real-time channel state information;

2）对应于小区间大尺度信道状态信息的导频插入周期和信道估计周期较长，只要能跟踪大尺度信道状态信息的变化即可。2) The pilot insertion period and channel estimation period corresponding to large-scale channel state information between cells are relatively long, as long as the changes of large-scale channel state information can be tracked.

其中信道状态信息反馈分为：The channel state information feedback is divided into:

1）小区内即时信道状体信息反馈周期短，要足以跟踪即时信道状态信息的快速变化；1) The real-time channel state information feedback period in the cell is short, which is enough to track the rapid changes of real-time channel state information;

2）小区间大尺度信道状态反馈周期较长，只要能跟踪大尺度信道状态信息的变化即可2) The large-scale channel state feedback cycle between cells is relatively long, as long as the changes in large-scale channel state information can be tracked

由于大尺度CSI变化比较缓慢，用于估计大尺度CSI的导频插入周期可以延长，信道估计周期和反馈周期也可以适当延长。从而导频开销、信道估计开销和反馈开销都可以有效得到降低。Since the large-scale CSI changes slowly, the pilot insertion period for estimating the large-scale CSI can be extended, and the channel estimation period and feedback period can also be appropriately extended. Therefore, pilot overhead, channel estimation overhead and feedback overhead can all be effectively reduced.

其中，该方法还包括集中处理节点将计算出的波束成形向量分发给各个小区的中心处理器，各个小区的中心处理器对相应用户的波束成形向量进行预处理的步骤。Wherein, the method further includes a step in which the centralized processing node distributes the calculated beamforming vectors to the central processors of each cell, and the central processors of each cell preprocess the beamforming vectors of corresponding users.

具体的：specific:

考虑一个广义小区的DWCS系统，系统中有K个小区，其中第k个小区内有N_k个分布式天线单元、U_k个单天线的用户和一个中心处理器，各个小区的中心处理器通过有线链路连接到一个集中处理节点。各个小区内的分布式天线单元通过光纤连接到各自小区的中心处理器，同一个小区内各个分布式天线单元的发送和接收信号都在相应的中心处理器中联合处理。如图2所示，是一个有3个小区的DWCS系统。Consider a DWCS system of a generalized cell. There are K cells in the system, and the kth cell has N_k distributed antenna units, U_k single-antenna users and a central processor. The central processors of each cell pass Wired links connect to a centralized processing node. The distributed antenna units in each cell are connected to the central processor of each cell through optical fibers, and the sending and receiving signals of each distributed antenna unit in the same cell are jointly processed in the corresponding central processor. As shown in Figure 2, it is a DWCS system with 3 cells.

S1、在下行链路中第k个小区内第u个用户接收到的信号表示为S1. In the downlink, the signal received by the uth user in the kth cell is expressed as

${y the y}_{u u}^{((k k))} = = {h h}_{u u}^{((k k,, k k))} {w w}_{u u}^{((k k))} {x x}_{u u}^{((k k))} + + {Σ Σ}_{l l = = 11}^{K K} {Σ Σ}_{j j = = 11,, ((l l,, j j)) &NotEqual; &NotEqual; ((k k,, u u))}^{{U u}_{l l}} {h h}_{u u}^{((k k,, l l))} {w w}_{j j}^{((l l))} {x x}_{j j}^{((l l))} + + {n no}_{u u}^{((k k))},, - - - - - - ((11))$

其中是一个1×N_l的复向量，表示第l个小区的各个分布式天线到第k个小区中第u个用户的信道，是第l个小区中第j个用户的波束成形向量，是第l个小区中第j个用户的发送信号，是复高斯白噪声，服从复高斯分布in is a complex vector of 1×N_l , representing the channel from each distributed antenna of the lth cell to the uth user in the kth cell, is the beamforming vector of the jth user in the lth cell, is the transmitted signal of the jth user in the lth cell, is complex Gaussian white noise, obeying complex Gaussian distribution

依据表达式1，可以表示为According to expression 1, It can be expressed as

${h h}_{u u}^{((k k,, l l))} = = {g g}_{u u}^{((k k,, l l))} {L L}_{u u}^{((k k,, l l))} - - - - - - ((22))$

其中是一个1×N_l的复向量，它的每个元素服从CN(0,1)分布，表示小尺度衰落，即瑞利衰落；是一个对角阵，表示大尺度衰落，包括路径损耗和阴影衰落。是第l个小区第n个分布式天线单元到第k个小区中第u个用户的距离，是两者之间的阴影衰落，γ是路径损耗因子。在此系统中，各小区内部即时CSI为：in Is a complex vector of 1×N_l , each element of which obeys CN(0,1) distribution, representing small-scale fading, that is, Rayleigh fading; is a diagonal matrix representing large-scale fading, including path loss and shadow fading. is the distance from the nth distributed antenna unit in the lth cell to the uth user in the kth cell, is the shadow fading between the two, and γ is the path loss factor. In this system, the real-time CSI inside each cell is:

${{{h h}_{u u}^{((k k,, k k))} = = {g g}_{u u}^{((k k,, k k))} {L L}_{u u}^{((k k,, k k))} | | k k = = 11,, . . . . . .,, K K,, u u = = 11,, . . . . . .,, {U u}_{k k}}} - - - - - - ((33))$

小区间大尺度CSI为：The large-scale CSI between cells is:

${{{h h}_{u u}^{((k k,, l l))} = = {g g}_{u u}^{((k k,, l l))} {L L}_{u u}^{((k k,, l l))} | | k k,, l l = = 11,, . . . . . .,, K K,, k k &NotEqual; &NotEqual; l l,, u u = = 11,, . . . . . .,, {U u}_{k k}}} - - - - - - ((44))$

将所有信道状态信息反馈给本小区的中心处理器；若U_k＝U,N_k＝N，则各小区内部CSI涵盖NUK条单发单收信道，小区间CSI涵盖(K-1)NUK条单发单收信道，可见小区间CSI占全部CSI的当小区数K比较大，系统中的用户仅估计和反馈小区内部即时CSI和小区间大尺度CSI，可以大大降低导频、信道估计以及反馈开销。Feedback all channel state information to the central processor of the cell; if U_k = U, N_k = N, the internal CSI of each cell covers NUK single-send-single-receive channels, and the inter-cell CSI covers (K-1) NUK channels Single-send and single-receive channels, it can be seen that the CSI between cells accounts for all CSI When the number of cells K is relatively large, users in the system only estimate and feed back real-time CSI within the cell and large-scale CSI between cells, which can greatly reduce pilot frequency, channel estimation, and feedback overhead.

S2、各个小区的中心处理器收到各个用户反馈的CSI后将其转发给集中处理节点S2. After receiving the CSI fed back by each user, the central processor of each cell forwards it to the centralized processing node

S3、基于收到的CSI，集中处理节点根据选定的优化目标采用一定的优化方法计算系统中各个用户的发送波束成形向量S3. Based on the received CSI, the centralized processing node uses a certain optimization method to calculate the transmit beamforming vector of each user in the system according to the selected optimization goal

S4、集中处理节点将计算出的波束成形向量分发给各个小区的中心处理器，使各中心处理器对相应用户的数据进行预处理。S4. The centralized processing node distributes the calculated beamforming vectors to the central processors of each cell, so that each central processor performs preprocessing on data of corresponding users.

若DWCS系统中的各个用户的业务对时延不敏感，且不同的用户优先级不同，则可以选取系统的加权和速率为优化目标。由于对于小区间的信道发送端仅知道大尺度CSI，基于用户接收到的干扰加噪声服从高斯分布的假设，第k个小区内第u个用户接收到的干扰加噪声的功率If the service of each user in the DWCS system is not sensitive to delay, and different users have different priorities, then the weight and rate of the system can be selected as the optimization target. Since the transmitter only knows the large-scale CSI for the inter-cell channel, based on the assumption that the interference plus noise received by the user obeys the Gaussian distribution, the power of the interference plus noise received by the uth user in the kth cell

${I I}_{k k,, u u}^{22} ((w w)) = = {Σ Σ}_{l l = = 11}^{K K} {Σ Σ}_{j j = = 11,, ((l l,, j j)) &NotEqual; &NotEqual; ((k k,, u u))}^{{U u}_{l l}} {| | {h h}_{u u}^{((k k,, l l))} {w w}_{j j}^{((l l))} | |}^{22} + + {σ σ}_{k k,, u u}^{22} - - - - - - ((55))$

可以近似表示为can be approximated as

${J J}_{k k,, u u}^{22} ((w w)) = = {E E.}_{{{{g g}_{u u}^{((k k,, l l))} | | l l = = 11,, . . . . . .,, K K,, l l &NotEqual; &NotEqual; k k}}} (({I I}_{k k,, u u}^{22} ((w w)))) = = {Σ Σ}_{i i = = 11,, i i &NotEqual; &NotEqual; u u}^{{U u}_{k k}} {| | {h h}_{u u}^{((k k,, k k))} {w w}_{i i}^{((k k))} | |}^{22} + + {Σ Σ}_{l l = = 11,, l l &NotEqual; &NotEqual; k k}^{K K} {Σ Σ}_{j j = = 11}^{{U u}_{l l}} {| | | | {L L}_{u u}^{((k k,, l l))} {w w}_{j j}^{((l l))} | | | |}_{22}^{22} + + {σ σ}_{k k,, u u}^{22} - - - - - - ((66))$

假设第k个小区第u个用户的加权系数为第k小区的所有分布式天线单元的总发送功率约束为P^(k)，则多小区联合波束成形问题可以写为Assume that the weighting coefficient of the uth user in the kth cell is The total transmit power of all distributed antenna units in the k-th cell is constrained by P^(k) , then the multi-cell joint beamforming problem can be written as

$\underset{{{{w w}_{u u}^{((k k))} | | k k = = 11,, . . . . . .,, K K,, u u = = 11,, . . . . . .,, {U u}_{k k}}}}{max max} {Σ Σ}_{k k = = 11}^{K K} {Σ Σ}_{u u = = 11}^{{U u}_{k k}} {α α}_{u u}^{((k k))} {log log}_{22} ((11 + + \frac{{| | {h h}_{u u}^{((k k,, k k))} {w w}_{u u}^{((k k))} | |}^{22}}{{J J}_{k k,, u u}^{22} ((w w))})) - - - - - - ((77))$

s.t. $Σ_{u = 1}^{U_{k}} {| | w_{u}^{(k)} | |}_{2}^{2} \leq P^{(k)}, k = 1, . . ., K .$ st $Σ_{u = 1}^{u_{k}} {| | w_{u}^{(k)} | |}_{2}^{2} \leq P^{(k)}, k = 1, . . ., K .$

要计算各个用户的发送波束成形向量，集中处理节点只需要采用一定的算法求出该问题的解即可。To calculate the transmit beamforming vector of each user, the centralized processing node only needs to use a certain algorithm to find the solution of the problem.

以上所述仅是本发明的优选实施方式，应当指出，对于本技术领域的普通技术人员来说，在不脱离本发明技术原理的前提下，还可以做出若干改进和替换，这些改进和替换也应视为本发明的保护范围。The above is only a preferred embodiment of the present invention, it should be pointed out that for those of ordinary skill in the art, without departing from the technical principle of the present invention, some improvements and replacements can also be made, these improvements and replacements It should also be regarded as the protection scope of the present invention.

Claims

Translated fromChinese

1.一种下行多小区联合波束成形方法，其特征在于，该方法包括：1. A downlink multi-cell joint beamforming method, characterized in that the method comprises:

S3、基于接收到的信道状态信息，集中处理节点按照预定的优化目标，优化计算出小区中各个用户的发送波束成形向量；S3. Based on the received channel state information, the centralized processing node optimizes and calculates the transmit beamforming vector of each user in the cell according to the predetermined optimization goal;