QoS-aware MAC protocols for wireless sensor networks: A survey <s> QoS-aware MAC Protocols Protocols with Di erentiated Services <s> This paper presents a new prioritized medium access control protocol (PSIFT) that improves the performance of event-driven wireless sensor networks by suppressing the redundant reports of sensor nodes in proximity. This suppression of similar reports results in low collision probability, shorter delay and accurate detection of events by the sink. PSIFT is a CSMA-based MAC protocol that provides traffic differentiation by varying the inter frame space and contention window size for each traffic class. We also introduce the new report suppression mechanism based on the broadcast nature of wireless transmission in PSIFT. This mechanism works very efficiently in large-scale, event-driven wireless sensor networks. Simulation results show that the new PSIFT MAC protocol can bring significant improvement in delay performance of the networks. When the sensing range grows up to transmission range, PSIFT can reduce the latency as much as three times in delivering reports as compared to the existing IEEE802.11 MAC protocol. <s> BIB001 </s> QoS-aware MAC protocols for wireless sensor networks: A survey <s> QoS-aware MAC Protocols Protocols with Di erentiated Services <s> This paper introduces I-MAC, a new medium access control protocol for wireless sensor networks. I-MAC targets at improving both channel utilisation and energy efficiency while taking into account traffic load for each sensor node according to its role in the network. I-MAC reaches its objectives through prioritized and adaptive access to the channel. I-MAC performances obtained through simulations for different network topologies, scenarios and traffic loads show significant improvements in energy efficiency, channel utilization, loss ratio and delay compared to existing protocols. <s> BIB002
Most of the QoS-aware MAC protocols provide service di erentiation by varying: -CW size -Contention slot selection probability -Transmission slot scheduling -IFS duration -Backo exponent -Adaptation coe cients E.g. BIB001 BIB002 