Multi-code SS-CSMA/CA for cluster-tree wireless ad hoc networks

Multi-hop delay and packet error due to packet collision are serious issues for realizing large-scale wireless ad hoc networks. A cluster-tree network can reduce multi-hop delay by limiting hop counts. However, the network suffers from bottleneck at a network sink node and it limits data throughput. Also, hidden terminals bring packet collision issues when using CSMA/CA. In this paper, spread spectrum multiple access (SSMA) employing multicode reception and CSMA/CA are combined as a new MAC protocol for solving the issues. A carrier sense method after despreading and a double-spreading code assignment method for the network are also proposed for improving the performance. Throughput and data delivery ratio for the proposed method are analyzed via simulations based on the IEEE 802.15.4/ZigBee. Simulation results show that the throughput is remarkably improved and the bottleneck at a network coordinator is mitigated with the proposed method.