Enhancement of IEEE 802.15.4 MAC layer to combat correlated channel errors

摘要

In indoor environment, the IEEE 802.15.4 low-rate, low-power packet transmissions experience statistical correlation between channel errors due to interference and multipath fading. The 802.15.4 MAC layer implements an ARQ (Automatic Repeat-Request) mechanism for error recovery. In this work, we investigate the impact of correlated errors on the ARQ mechanism. The MAC layer back-off strategy employs a uniform random distribution to choose back-off values; which often reduces retransmission resolution time when packets confront collisions or transmission errors. We therefore propose the application of non-uniform (skewed) distribution which improves the system performance. Furthermore, an adaptive back off strategy, fastEI-slowED is developed for IEEE 802.15.4 MAC protocol to combat channel errors in time varying conditions. A detailed comparative analysis is presented employing accurate models of wireless channel and MAC protocol. Numerical results indicate that proposed scheme performs better, especially in worst channel conditions, when long duration error bursts are more frequent.