Accurate analysis of IEEE 802.15.4 slotted CSMA/CA over a real-time wireless sensor network

Abstract

Here, we present the collision probability of the IEEE 802.15.4 slotted Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) mechanism over a real-time wireless sensor network (RT-WSN), also called a synchronous network system. The "backoff," the random delay of CSMA/CA, can be used to create a probability model and to determine the average packet delay over RT-WSN. The proposed theoretical analysis model was nearly consistent with the simulation and with experimental results. This suggests that the slotted CSMA/CA mechanism cannot be applied effectively to RT-WSN because it cannot avoid a high collision rate with RT-WSN application requirements and, therefore, may waste a great deal of system bandwidth. We found that the packet collision rate increased up to 731% compared to an ideal model with more than 10 users within an RT-WSN. Without improvements in methodology, the high collision rate makes this slotted CSMA/CA mechanism unsuitable for RT-WSN applications. © 2009 Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering.