Since nodes in a sensor network have limited energy, prolonging the network lifetime and improving scalability become important. In this paper, we propose a distributed weight-based energy-efficient hierarchical clustering protocol (DWEHC). Each node first locates its neighbors (in its enclosure region), then calculates its weight which is based on its residual energy and distance to its neighbors. The largest weight node in a neighborhood may become a clusterhead. Neighboring nodes will then join the clusterhead hierarchy. The clustering process terminates in O(1) iterations, and does not depend on network topology or size. Simulations show that DWEHC clusters have good performance characteristics.

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Abstract:In this paper, we model a wireless node's state transition using a Markov Chain model in a multihop ad hoc network. To investigate how the metrics, such as transmit power, contention window size, and node density, affect a node's performance with interference, our model takes into account the interfering nodes in the entire system. Most of the previous work either didn't consider all the interfering nodes in the network or simply ignored interference. Based on a Markov Chain model, we calculate a node's throughput, consumed energy and delay time. From the numerical results, we conclude that: 1. Transmit power, contention window size, and node density will all affect the network performance. 2. Throughput and energy can be optimized together, whereas optimizing delay time results in tradeoffs in throughput and consumed energy. 3. A high transmit power can not guarantee a low delay time.

IEEE 802.11 MAC protocol PCF is intended to facilitate real time traffic, however, the performance of PCF is highly affected by conditions on the WLAN and it has unnecessary overhead. To address these problems, we propose an aging priority scheduling algorithm and a dynamic adaptation algorithm to vary the PCF interval based on the traffic and reduce the overhead. Simulation results show our algorithms are efficient and suitable for PCF traffic.