Medium Access Control in Large Scale Clusters for Wireless Sensor Networks

One of the main advantages of clustering algorithms is the ability to allow networks to be physically divided into smaller regions, thereby increasing the theoretical maximum number of nodes connected in the network. However, the physical limitations in bandwidth and number of nodes are drawbacks to this approach. While reducing the number of clusters can reduce the network complexity, it will increase the intra-cluster management. This paper analyses the different medium access schemes that can be used and discusses what influence they bring to the overall performance in terms of bandwidth usage, energy consumption and latency. Two novel approaches are also proposed. The first one refers to the limitation in the transmission period and the request for each node within the cluster to transmit once within that period. The second innovation compromises two of the access mechanisms described: the first divides the period in two different parts, while the second takes different bias during the slot selection process, so it can have theoretical advantage over the re-transmission procedure. The results show that there is a significant advantages in listening to the channel prior to the transmission, as well as in re-trying to transmit only once.