Existing contention based nonpersistent medium access control protocols in Wireless Sensor Network (WSN) do not perform well in high contention. Their performances are affected by occurrence of collision due to uniform probability distribution in choosing Time Slot (TS) during backoff period. To address this issue nonuniform probability distribution was proposed. However success rate still drops for higher number of contenders. In this paper we propose CSMA/s (Collision Sense Multiple Access /per Slot based), a new approach in nonuniform contender-aware probability distribution for choosing TS in the backoff period. Rather than taking a premeditated fixed value for contender population size, our proposed scheme embeds neighborhood population size into its bedrock to automatically converge to the actual number of contenders which enables the contender to adaptively choose TS in the backoff period for reducing collision. This method produces better success rate and lower latency for even very high number of contenders.
Collision Sense Multiple Access (CSMA) has been preferred to Time Division Multiple Access (TDMA) as medium access scheme for Wireless Multimedia Sensor Network (WMSN) in the scenarios where the traffic is bursty in nature and multiple consecutive and contiguous packets generated from the same collision neighborhood need to be sent. Protocols based on nonuniform probability distribution do not perform well in high contention and heterogeneous traffic scenarios due to nonadaptive nature to contention neighborhood. In this paper we have proposed a scheme to adapt the Contention Window (CW) size according to the collision neighborhood population complying with the application specific latency and success probability constraints. This scheme shows improved performance compared with SIFT, a stereotype of non-uniform probability based CSMA protocol and can be deployed with any CSMA-CA (CSMA with Collision Avoidance) based backoff algorithm