Interconnecting 802.15.4 clusters in slotted CSMA-CA mode

Performance of collision-based MAC algorithms such as CSMA-CA, as used in networks compliant with IEEE 802.15.4 standard, rapidly deteriorates with the increase of the number of nodes. A promising remedy to this problem is hierarchical partitioning, in which the parent cluster communicates with its child clusters through bridge nodes. The network sink is the coordinator of the parent cluster, while the bridges act as coordinators for their respective child clusters. In this paper, we investigate the performance of the simplest network with two clusters, both of which operate in beacon enabled, slotted CSMA-CA regime, using discrete event simulation. We examine the impact of different traffic and network parameters and identify the conditions that lead to saturation. We show that non-acknowledged transfers offer much better performance in a wide range of traffic and network parameters.