采用多天线技术是对抗无线信道衰落的有效手段,但在无线通信系统的用户终端上实现多天线技术较为困难。在单天线的用户间通过协作,共享天线,可以实现虚拟的多天线。利用LDPC编码码字内码元间的相关性,通过在用户间进行协作,对编码码字的一部分进行空时编码,并由多个用户的天线进行发送,可以实现虚拟的MIMO系统,从而获得分集增益。仿真结果显示,在不增加系统带宽和发射功率的条件下,编码协作能显著地提高快衰落和慢衰落信道下系统的性能。
Cooperative communication allows the sharing of antennas among single antenna wireless terminals, and thus can create a virtual multi-antenna system. Because of the strong coherence among the symbols of the LDPC code word, a virtual multiple input multiple output (MIMO) system can be created to obtain space diversity gain by encoding the parts of the symbols of a LDPC code word using space-time code and transmitting them via different users' antennas. By using such a code cooperation method, the system performance can be improved effectively without increasing the transmitting bandwidth or power.