Making the Case for Random Access Scheduling in Wireless Multi-hop Networks

This paper formally establishes that random access scheduling schemes, and, more specifically CSMA-CA, yields exceptionally good performance in the context of wireless multihop networks. While it is believed that CSMA-CA performs significantly worse than optimal, this belief is usually based on experiments that use rate allocation mechanisms which grossly underutilize the available capacity that random access provides. To establish our thesis we compare the max-min rate allocation achieved by CSMA-CA and optimal in multi-hop topologies and find that: (i) CSMA-CA is never worse than 16% of the optimal when ignoring physical layer constraints, (ii) in any realistic topology with geometric constraints due to the physical layer, CSMA-CA is never worse than 30% of the optimal. Considering that maximal scheduling achieves much lower bounds than the above, and greedy maximal scheduling, which is one of the best known distributed approximation of an optimal scheduler, achieves similar worst case bounds, CSMA-CA is surprisingly efficient.