无线中继网络中的协作方案与传输技术研究

【作者】 张彬；

【导师】 吴伟陵；

【作者基本信息】 北京邮电大学 ， 信号与信息处理， 2010， 博士

【摘要】 理论和实验证明,无线中继技术可以提高无线链路的吞吐率及传输可靠性,并且可以增加系统的覆盖范围和系统的鲁棒性,近年来受到越来越多的关注并已成为3GPP LTE-Advanced无线通信标准的重要候选技术之一。MIMO中继技术结合了多天线系统和中继技术的优点,进一步提高了中继系统的频谱效率。本文主要对MIMO中继网络中的协作方案和传输技术进行了研究。主要包括以下几个方面：1.针对存在多个中继节点的多用户MIMO中继网络,研究了基于交织多址接入的多中继异步协作传输方案,并给出目的节点接收端的迭代检测算法。该方案结合了IDMA和延迟分集技术,系统为每个源节点分配不同的交织器,多个中继节点在转发阶段采用延迟分集,使接收端可以通过迭代检测分离出经过不同中继转发的同一信号并进行最大比合并,获得相应的分集增益。本方案的优点在于不要求多个中继节点同步传输,对网络中源节点的数目和中继节点的数目没有限制,而且中继节点不需要获得任何信道状态信息。2.研究了两跳非再生MIMO中继网络中的线性收发机联合设计问题。首先,假设所有信道状态信息是理想的,利用最小均方误差准则对源节点、中继节点和目的节点的信号处理矩阵进行联合设计,并提出一种迭代算法用来计算这三个矩阵。其次,假设信道估计存在误差,将这种迭代算法推广到非理想信道状态信息的情况下。为了降低迭代算法的计算复杂度,我们还提出了一种分块优化的方法来设计源节点发送矩阵、中继处理矩阵和目的节点接收矩阵。和迭代算法相比,这种分块优化的方法可以大大降低复杂度而只付出较小的性能增益损失,因此更具有实用性。3.针对多用户MIMO中继系统的下行信道,借助中继的转发,基站和多个用户同时进行通信,研究了鲁棒的中继预编码。假设每个用户和中继之间存在有限反馈链路,用户通过此链路将各自的信道方向信息反馈给中继,用于中继的预编码操作。考虑到由于反馈比特数有限,在码字映射过程中会产生误差。为了对误差进行一定的预补偿,我们提出了鲁棒的迫零预编码方案和鲁棒的最小均方误差预编码方案并分析了在这两种方案中用户接收端的信干噪比特性。与传统的线性预编码相比,文中提出的鲁棒预编码能够降低系统的平均误码率。更多还原

【Abstract】 It has been proved that the wireless relay network can significantly en-hance the throughput and increase the reliability of wireless link, and can en-large the coverage and improve the robustness of the systems. Relay technol-ogy has attracted increasing attention in recent years and is has been become an important candidate technology for 3GPP LTE-Advanced. MIMO relay chan-nels,which combines the multiple antenna system and the relay,can improve the spectral efficiency of relay network. In this dissertation,we focus on the co-operative transmission technologies in MIMO relay systems.Detailed contents are listed as:1. Investigation is made upon the asynchronous cooperative transmission scheme based on interleave-division multiple access (IDMA) in the multi-user MIMO relay system with multiple relays. This system combines IDMA and delay diversity (DD),in which every user is assigned a dif-ferent interleaver and the relays forward the signal after a random delay. By using a turbo-type MIMO IDMA receiver with low complexity incor-porating with an efficient soft MIMO multi-user detector, the destination node can distinguish the signals corresponding to the same information from multiple relays and implement maximal ratio combining (MRC) to exploit diversity gain. This scheme does not need synchronous transmis-sion, has no restriction on the number of users and relays, and all the relays need no channel state information (CSI).2. Investigation is made upon the joint linear transceiver design in two-hop non-regenerative MIMO relay network. Firstly, we joint design the signal processing matrics of the source, relay and destination based on the min-imum mean square error (MMSE) criterion under the assumption of per-fect channel state information (CSI). An iterative algorithm is proposed to get the signal processing matrics. Secondly, we extend this algorithm to the system with channel estimation errors. In order to reduce the com-putational complexity of the iterative algorithm, we also propose a block-optimization method to compute the transmission matrix of the source, relay processing matrix and the receive matrix of the destination. The block-optimization method can achieve a similar performance to the it-erative algorithm with a much lower complexity, which is much more practical in realistic relay systems.3. Investigation is made upon the robust relay precoding in the downlink channel of multi-user MIMO relay system, where multiple mobile users are served by the base station (BS) simultaneously through a single relay station (RS). Assuming that there is a limited feedback link between each user and the RS, every mobile user feeds back its channel direction infor-mation (CDI) by B bits to RS in order to implement the relay precoding. Taking into account the effect of codeword mapping errors, we proposed a robust zero forcing (ZF) precoding scheme as well as a robust MMSE precoding scheme. We also analysis the signal to interference plus noise ratio (SINR) properties of the precoding schemes. Compared to the con-ventional linear precoding techniques, the proposed robust precoders can reduce the average bit error rate (BER) of the system.更多还原