Performance analysis of IEEE 802.15.4 based wireless sensor networks

This thesis investigates performance of the IEEE 802.15.4 standard in the context of wireless sensor networks (WSNs) deployed in pervasive monitoring. IEEE 802.15.4 has been widely acknowledged as the standard physical (PHY) and medium access control (MAC) layer specifcations for WSNs due to its simple protocol stack and low power operation. Mathematical models and computer simulations were devised to analyse the IEEE 802.15.4 MAC protocol and to improve its performance under different applications and operational conditions. First, the beacon-enabled mode of the protocol with acknowledgments (ACKs) was analysed using a discrete time Markov chain (DTMC). The proposed model provides a generalised platform to evaluate the impact of different network and MAC layer parameters and erroneous channel conditions on the performance of the protocol. Second, performance of the non-beacon-enabled mode of the protocol was investigated both with and without ACKs. The outcomes of these analyses were then used to compare and contrast the performance of two operational modes. Third, impact of the presence of hidden nodes on the performance of IEEE 802.15.4 based networks was examined. Using a DTMC model and network simulations, it was shown that the throughput of the protocol is severely reduced due to increased transmission failures caused by hidden nodes. Finally, a new hybrid MAC mechanism was proposed to improve the performance of the IEEE 802.15.4 standard in the context of recently emerged hybrid monitoring applications. Simulation based experiments show that the proposed hybrid protocol not only outperforms the standard protocol, but also provides a reliable, energy effcient and delay limited transmission mechanism for hybrid monitoring WSNs. This thesis has provided a platform for further studies on the performance analysis and application specific tailoring of the IEEE 802.15.4 standard in the context of WSNs