Level the buffer wall: Fair channel assignment in wireless sensor networks

In this paper, we study the trade-off between network throughput and fairness in a multi-channel enabled wireless sensor network (WSN). Traditional approaches attempt to solve the two problems in an isolated manner without a joint design. Our empirical studies show that solutions to these two problems cannot be simply combined. Away from the traditional belief, the number of channels in WSNs with Telosb sensor nodes operating at 2.4 GHz band can be up to 83 and the orthogonal channels can be up to 27. The switching overhead in terms of time and energy cost is relatively small. Furthermore, we observe a buffer wall phenomenon which is one of the main reasons causing network throughput degradation and unfairness. To strike a better trade-off between the network throughput and fairness, we design a novel multi-channel assignment algorithm, targeting at maximizing the minimal data sending rate. The key idea of the proposed algorithm is to level down the buffer wall so that the buffer usage of nodes can be evenly distributed. As such, the bandwidth of bottleneck nodes can be fully utilized and the unfairness due to the node locality can be removed. We prove that the achieved data sending rate is no less than 4/9 of the optimal rate in theory. Our experimental results show that the minimal data sending rate can be improved by up to 100% comparing with the existing work TMCP.