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自由度(DOF)是一个空间复用概念,是在多天线系统中引入的,体现了无线信道对空间资源的利用效率。在认知无线电中,由于主、次网络会相互干扰,从而会降低DOF。本文主要研究的是2×2 X信道(XC)和点对点(PTP)信道并存时网络的DOF。研究结论也适合于XC优先于PTP信道的情况。在已知发送端信道状态(CSI)信息的前提下,基于符号扩展模型,利用渐进干扰对齐方法给出了对应的信号处理方案,并证明当n趋于无穷大时,自由度内界可达5/3。利用传播时延模型示范了其可达性。此外,分析了DOF上界。
DOF (DOF) is a concept of spatial multiplexing introduced in multi-antenna systems, which reflects the utilization efficiency of wireless channels in space resources. In cognitive radio, DOF is reduced because the primary and secondary networks interfere with each other. This paper mainly studies the DOF of 2 × 2 X-channel (XC) and point-to-point (PTP) channels co-existing in the network. The conclusion is also suitable for the situation that XC takes precedence over PTP channel. On the premise of known channel state information (CSI), the signal processing scheme is given based on the symbolic extension model and using the method of progressive interference alignment. It is proved that when n reaches infinity, the inner bound of the degree of freedom can reach 5 / 3. The propagation delay model is used to demonstrate its reachability. In addition, DOF upper bounds are analyzed.