Diversity and Multiplexing in Cooperative Wireless Cellular Networks

In wireless cellular systems, capacity can be increased if both in-cell and out-of-cell cochannel interference (CCI) is properly handled. Moreover, spatial multiplexing has been proved to be much effective in multiuser MIMO systems. The authors propose a cross-layer approach to opportunistic interference management and spatial multiplexing, by using a random beamforming strategy and a smart scheduler assuming a certain degree of cooperation between transmitters. In this paper, we recall the resource allocation algorithm, we derive the PDF and CDF of the SINR of a simplified cooperative multiuser MIMO system and we discuss some numerical results. In particular, we examine the tradeoff between spatial diversity and multiplexing as a function of the out-of-cell CCI level. Numerical results show that, for high out-of-cell interference, a larger throughput is achieved if at most one user is scheduled at a time in each cell. Otherwise, spatial multiplexing must be used to improve the system overall throughput. The CCI threshold value strongly depends on the receivers complexity (e.g., MISO or MIMO).