Transmission Capacity Scaling of SDMA in Wireless Ad Hoc Networks

We consider an uncoordinated ad hoc network in which each multi-antenna transmitter sends multiple independent streams to different receivers in a Poisson field of interferers. We provide exact and approximate outage probability expressions and transmission capacity scaling laws, aiming at investigating the fundamental limits of Space Division Multiple Access (SDMA). We first show that superlinear capacity scaling with the number of receive/transmit antennas can be achieved using dirty paper precoding. Nevertheless, the potential benefits of multi-stream and multi-antenna communications fall off quickly if linear precoding is employed, leading even to sublinear capacity growth for single-antenna receivers. Our results indicate that receive antenna array processing is of prime importance in SDMA ad hoc networks, as a means to cancel the increased residual interference and boost the signal power through diversity.