Distributed CDMA code assignment for wireless sensor networks

Wireless sensor networks are deployed for many collaborative tasks such as monitoring, target tracking and surveillance. They communicate via multi-hops to one or more sinks over a shared wireless medium. Code division multiple access (CDMA) allows many sensor nodes to transmit simultaneously over the common shared medium without excessive collisions that often result in packet loss and lowered throughput. However, this requires the proper assignment of orthogonal codes to the sensor nodes to minimize interference among adjacent neighbors. Due to the distributed and autonomous nature of sensor networks, CDMA codes cannot be assigned in the same way as cellular networks. We propose a distributed methodology of assigning CDMA codes to the nodes, which has low message overheads, allows for spatial reuse of the channel and does not depend on the availability of neighbor information. Our approach is also able to handle topological changes that could be induced by nodes entering or leaving the network. We study the effectiveness of our algorithm through simulations and analysis.