Concurrent link capacity of MIMO ad-hoc networks with QoS constraint

MIMO based MANET has received a great deal of attention in the past decade, resulting in a number of MAC layer protocols that aim to utilize the inherent capabilities afforded by multi-antenna enabled nodes. Many of these MAC protocols look to improve on the total number of concurrent links within the network. In this paper, we present a theoretical approach for identifying the maximum number of concurrent links (MNCL) in a MIMO enabled MANET, subject to the constraint that all links provide a minimum QoS measured in terms of signal to interference and noise ratio (SINR). We assume that each receiver uses an MMSE based detector which provides a balance between completely nulling of neighboring interference and hardware complexity. As a byproduct of the MNCL, the solution will provide the optimum power allocation for the nodes as well as the optimum concurrent link allocation. The proposed approach is readily applicable to MIMO systems using Receive Diversity, Transmit Beamforming, and Space Time Block Coding (STBC). The results show that the MNCL can be improved significantly by exploiting multi-user diversity and increasing the number of receiver antennas. But the improvement from allowing higher transmit power is not significant. The derived MNCL capacity can be used to highlight theoretical insights for practical designs.