Protocol for Latency Reduction of Prioritized Traffic in WSN

In critical scenarios nodes switch from low data rate of transmission mode to high data rate. Such scenarios are event driven and traffic is highly dynamic in nature. Latency and reliability issues with Quality of Service (QoS) for such applications in IEEE 802.15.4 have been an issue. The earlier schemes did address them but high data rates and channel error rates resulted in increase in contention for GTS request packets and increased data packet drop rate. In our work, we employed a mechanism to deal with isuues arising out of additional contention caused by prioritized nodes in CAP. We present an enhanced MAC scheme that incorporates two-level service differentiation through Contention Window Differentiation (CWD) and dynamic p-persistent CSMA, for mitigating the issues like lower transmission delays and higher success probability to time-critical messages in high channel error conditions. We evaluate our proposed scheme for varying channel and traffic-load conditions by simulation using Omnet+ + .The results show that performance in terms of the mentioned issues has improved significantly. Further, the energy decline rate analysis have been done for varying traffic arrival rates and compared with the original IEEE 802.15.4 and found that our scheme has less energy decline rate thus increased network lifetime.