Quality of service implications of power control and multiuser detection-based cross-layer design

In order to allow for dense spatial reuse in wireless ad hoc networks, multiple access interference must be dealt with. This calls for advanced physical layer techniques, such as multiuser detection or power control. However, these techniques can only be efficiently applied to ad hoc networks when they are part of a joint PHY/MAC cross-layer design. In order to better understand both, the potential but also the limits of handling interference by means of multiuser detection and power control, respectively, in this paper we provide a comprehensive comparison between multiuser detection based and power control based cross layer designs. We study the behavior of both approaches in terms of throughput, delay, as well as fairness in scenarios with high and low user densities, respectively. To provide more detailed insight in the interaction between MAC and PHY, we separate for each approach the throughput results into gains achieved solely by the MAC layer and by the PHY layer, respectively. These results highlight, among other aspects, some fundamental disadvantage of power control in distributed environments. We conclude that multiuser based approaches are significantly more beneficial in ad hoc scenarios than power control based schemes.