Design of Non-orthogonal Multi-channel Sensor Networks

A critical issue in wireless sensor networks (WSNs) is represented by the network throughput. To meet the throughput requirement, researchers propose multi-channel design in 802.15.4 networks to better utilize the wireless medium and avoid the co-channel interference. However, traditional orthogonal channel design restricts the number of channels and limits the throughput performance. We argue that the orthogonality is not necessary for multi-channel design in WSNs. In this paper, we investigate the feasibility of non-orthogonal channel design. In our experiment, we observe that with nonorthogonal transmission, the effect of interference comes from co-channel and inter-channel is different. More specifically, the inter-channel interference is tolerable with certain channel center frequency distance (CFD). According to that, we propose a novel scheme DCN (Dynamic CCA-threshold for Non-orthogonal transmission) which adjusts the CCA-threshold to enable the concurrent transmissions on adjacent non-orthogonal channels and thus improve the overall network throughput performance. Through comprehensive experiments on our testbed, we verify that our DCN achieves about 38.4% ~ 55.7% throughput improvement in general network configurations comparing to the default ZigBee design.