A Priority-Based Adaptive Service -Differentiation Scheme for IEEE 802.15.4 Sensor Networks

The IEEE 802.15.4 standard uses carrier sense multiple access with collision avoidance (CSMA/CA) algorithm as the medium access mechanism, which employs a binary exponential backoff (BEB) mechanism to control the access of nodes to the wireless medium. One of the main drawbacks of this algorithm is that it does not support network self-adaptivity. It updates the length of the backoff period in a deterministic manner without taking into consideration the actual status of the communication channel. The other drawback is that it does not support differentiated services. All the nodes are treated the same and each node has the same opportunity to access the medium. It seems to be quite fair when the nodes have the same priority level, but if service differentiation is considered, this method should be adjusted to overcome this shortcoming. We address these problems by proposing an adaptive priority-based service-differentiation CSMA/CA algorithm (APB-CSMA/CA) for differentiated services for IEEE 802.15.4. The proposed algorithm includes two mechanisms, 1) adaptive backoff mechanism. The nodes can dynamically adjust the backoff period according to the actual status of current network. 2) priority-based servicedifferentiation mechanism. In this mechanism, different parameters are given to different classes of services to provide multi-levels differentiated services. The results of OMnet++ simulation indicate that the proposed mechanism has a good result in mean end-to-end delay and collision probability.