Performance Analysis of Zigbee Wireless Sensor Networks with Relaying

In wireless sensor networks, transmitting information from sensors to a far access point (AP), out of direct transmission range, might make the use of relaying crucial. The goal of this chapter is to study the impact of relaying in Zigbee wireless sensor networks. In particular, we focus on Zigbee wireless sensor networks and analyze scenarios where the sensors transmit to an AP (or coordinator) (i) directly, (ii) through a relay node (or router), or (iii) through two relays. We study how the network performance (in terms of delay, transmission rate, and throughput) is influenced by the number of sensors, the traffic load, and the use of ACKnowledgment (ACK) messages. This performance analysis is carried out with simulations, analytical considerations, and experimental measurements. Our results show that the use of one or two relays, combined with the use of ACK messages (not efficiently managed by the upper layers of the network protocol stack), may cause a significant performance degradation. On the opposite, if ACK messages are not used, then the performance improves significantly. In addition, we also consider the impact of the network lifetime on the network transmission rate.