Channel assignment for ifying the critically exposed node problem in ad hoc wireless networks

We define and analyze a special case of exposed node problem that causes severe throughput degradation, which we term as the "critically exposed node problem." In a simple chain setup, we show that the reduction of throughput due to this problem is up to a factor of 14 compared to the ideal condition. There are practically very few suggestions in the literature to tackle the exposed node problem and none address the critically exposed node problem. We show by simulation how the critically exposed node problem affects capacity. We then explore a cluster-based channel assignment approach that can be used along with a multi-channel MAC protocol, called primary channel assignment based MAC (PCAM), to solve the problem. Using theoretical analysis, we work out the minimal number of channels required using an ideal, overlapped-clustering scheme and the multi-channel MAC protocol. Finally, we propose a distributed sub-optimal heuristics-based channel assignment protocol to address this issue.