Use of congestion-aware routing to spatially separate TCP connections in wireless ad hoc networks

Spatially separating TCP sessions such that they inflict much lower interference effects on each other may provide gains in performance. We first investigate the possibilities of achieving such gains by considering a centralized, ideal, and unrealistic congestion aware routing approach. We then consider the implementation of a distributed routing protocol to achieve the aforementioned spatial separation benefits. We find that due to practicalities such as the need for the exchange of congestion state, the existence of stale congestion information and the creation of sub-optimal paths, the benefits due to spatial separation are considerably undermined. We perform both macroscopic simulations and microscopic studies of specific constructed examples to understand the reasons and quantify the various effects with both the centralized and the distributed approaches. Our studies suggest that achieving noteworthy performance gains by spatially separating TCP sessions may be extremely difficult if not impossible in ad hoc networks.