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Wireless Sensor Networks (WSNs) provide a valuable capability to autonomously monitor remote activities. Their limited resources challenge WSN medium access control (MAC) layer designers to adequately support network services while conserving limited battery power. This paper presents an energyadaptive WSN MAC protocol, Gateway MAC (G-MAC), which implements a new cluster-centric paradigm to effectively distribute cluster energy resources and extend network lifetime. G-MAC's centralized cluster management function offers significant energy savings by leveraging the advantages of both contention and contention-free protocols. A centralized gateway node collects all transmission requirements during a contention period and then schedules their distributions during a reservation-based, contention-free period.With minimal overhead, the gateway duties are efficiently rotated based upon available resources to distribute the increased network management energy requirements among all of the nodes.

We develop and analyze a simple, elegant medium access control (MAC) protocol for use in transmitting real-time data in point to point ad hoc wireless local area networks (WLANs). Our enhancement of IEEE 802.11, real-time MAC (RT-MAC), achieves dramatic reductions in mean delay, missed deadlines, and packet collisions by selectively discarding packets and sharing station state information. For example, in a 50 station network with a normalized offered load of 0.7, mean delay is reduced from more than 14 seconds to less than 45 ms, late packets are reduced from 76% to less than 1%, and packet collisions are reduced from 36% to less than 1%. Regression models are developed from simulation data to describe network behavior in terms of throughput, mean delay, ratio of late packets, and ratio of collisions. Stations using RT-MAC are interoperable with stations using IEEE 802.11.

With the progression of computer networks extending boundaries and joining distant locations, wireless sensor networks (WSNs) emerge as the new frontier in developing opportunities to collect and process data from remote locations. WSNs rely on hardware simplicity to make sensor field deployments both affordable and long-lasting without maintenance support. WSN designers strive to extend network lifetimes while meeting application-specific throughput and latency requirements. Effective power management places sensor nodes into one of the available energy-saving modes based upon the sleep period duration and the current state of the radio. The newest generation of sensor platform radios with a 250 kbps data rate does not provide adequate time to completely power off the radio during overheard 128-byte constrained IEEE 802.15.4 transmissions. This paper proposes a new radio power management (RPM) algorithm which optimizes radio sleep capabilities by transitioning nodes to intermediate power level states. Additionally, the experimental work characterizes the radio power levels, state transition times, and state transition energy costs of an IEEE 802.15.4 compliant sensor platform for improved accuracy in simulating WSN energy consumption.