Cooperative Multiplexing: Toward Higher Spectral Efficiency in Multi-antenna Relay Networks
Cooperative Multiplexing: Toward Higher Spectral Efficiency in Multi-antenna Relay Networks
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发表时间：
2009-03
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通讯作者：
Yijia Fan;Chao Wang;H. Poor;J. Thompson
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作者：
Yijia Fan;Chao Wang;H. Poor;J. Thompson
以前关于合作通信的工作主要集中在这种技术的分集益处上。相反，本文考虑的是协作通信的多路复用好处。首先，对多天线中继网络中传输速率和中断概率之间的基本权衡给出了新的解释。结果表明，在全双工多天线中继网络中，可以在任意有限的信噪比下获得多路复用增益。因此，中继不仅可以提供更强的链路可靠性，而且还可以提供更高的频谱效率。具体而言，将应用解码转发协议，并考虑具有一个源、一个目的地和多个中继站的网络。此外，还考虑了中继端的接收功率增益，它反映了网络的大范围衰落特性。结果表明，对于任何有限的SNR值，这种功率增益都会显著影响系统的分集-复接折衷。提出了几种中继协议，在给定一定的信噪比和中继处的接收功率增益的情况下，这些协议被证明提供了几乎相同的中断概率，就像在源和中继器(S)处的发射天线位于同一位置一样。因此，如果目的地具有比源更多的天线，则可以获得比直接链路更高的多路复用增益。文中的大部分分析对于任意的信道衰落统计是有效的。这些结果表明，将中继网络视为提供更高频谱效率的一种手段，而不仅仅是链路可靠性。
Previous work on cooperative communications has concentrated primarily on the diversity benefits of such techniques. This paper, instead, considers the multiplexing benefits of cooperative communications. First, a new interpretation on the fundamental tradeoff between the transmission rate and outage probability in multi-antenna relay networks is given. It follows that multiplexing gains can be obtained at any finite SNR, in full-duplex multi-antenna relay networks. Thus relaying can offer not only stronger link reliability, but also higher spectral efficiency. Specifically, the decode-and-forward protocol is applied and networks that have one source, one destination, and multiple relays are considered. A receive power gain at the relays, which captures the network large scale fading characteristics, is also considered. It is shown that this power gain can significantly affect the system diversity-multiplexing tradeoff for any finite SNR value. Several relaying protocols are proposed and are shown to offer nearly the same outage probability as if the transmit antennas at the source and the relay(s) were co-located, given certain SNR and receive power gains at the relays. Thus a higher multiplexing gain than that of the direct link can be obtained if the destination has more antennas than the source. Much of the analysis in the paper is valid for arbitrary channel fading statistics. These results point to a view of relay networks as a means for providing higher spectral efficiency, rather than only link reliability.