It is known that interference alignment (IA) plays an important role in improving the degree of freedom (DoF) of multi-input and multi-output (MIMO) systems. However, most of the traditional IA schemes suffer from the high computational complexity and require the global and instantaneous channel state information (CSI), both of which make them difficult to be extended to cellular MIMO systems. To handle these issues, two new interference alignment schemes, i.e., the retrospective interference regeneration (RIR) scheme and the beamforming based distributed retrospective interference alignment (B-DRIA) scheme, are proposed for cellular K-user MIMO downlink networks. For the RIR scheme, it adopts interference elimination algorithm to erase redundant symbols in inter-cell interference (ICI) signals, and then uses interference regeneration algorithm to avoid secondary interference. The RIR scheme obtains greater DoF gain than the retrospective interference alignment (RIA) scheme, but incurs performance degradation when the transceiver antennas ratio (TAR) approaches 1. Therefore, the B-DRIA scheme is further proposed. For the B-DRIA scheme, the cellular beamforming matrix is introduced to eliminate the ICI, and meanwhile distributed retrospective interference alignment algorithm is adopted to align inter-user interference (IUI). The simulation results show that the B-DRIA scheme obtains larger DoF than the RIR scheme locally. Specifically, when TAR approaches 1, two schemes obtain the same DoF. While TAR approaches 2, the DoF of the B-DRIA scheme is superior than the RIR scheme.
翻译:众所周知,干预调整(IA)在提高多投入和多产出(MIMO)系统的自由度(DoF)方面发挥着重要作用,然而,大多数传统的IA计划都具有很高的计算复杂性,需要全球和即时频道国家信息(CSI),这使得难以将其扩展至蜂窝IMIMO系统;要处理这些问题,两个新的干预调整计划,即回溯干扰再生(RIR)计划和基于信号的分布式回溯干扰调整(B-DRIA)计划,是为蜂窝K用户MIMO下行连接网络提出的。对于RIR计划,采用干扰消除算法来消除细胞间干扰信号(ICI)信号中的冗余符号,然后使用干扰再恢复算法来避免二次干扰。RIR计划比追溯干扰调整(RI)计划获得更大的收益,但在转盘天线比率(TAR)接近1时,B-DRIA计划进一步提出。对于B-RIA计划而言,蜂窝-IMIMIMIMO的干扰调整计划比RRRA系统得到的更精确的版本。