| Wireless Sensor Network (WSN), consisting of many nodes with limited power and working in ad hoc manner, is designed to finish date sensing, gathering, and analyzing tasks in special environment. Since WSN nodes are characterized by small size, limited computing capacity, radio communication and powered by battery, there are still many problems to be solve or improved, to make WSN work optimally in some specific conditions. Topology Control (TC), one of optimization measures, aims at improving the scalability, lifetime and concurrency, through decreasing the media access collision, neighboring degree, and the energy consumed per transmission. Its method includes transmission power adjustment or sleep scheduling.Based on analyzing the position of TC protocol in protocol stack and its relationship with other protocols, the article introduced probabilistic link model and stochastic link quality estimation, and proposed the LQA-TC algorithm, which is based on the RSSI, an indicator of the receiving signal power. In the model specified in the article, LQA-TC ensures network connectivity, link symmetry, proper average neighbor node degree, and improves the network energy consumption, average interfering node degree, with limited extra overhead. Together, the article proposed an improved algorithm LBA-TC, to prolong the lifetime of network. LBA-TC takes into consideration the load balancing issues introduced by traditional TC method and is implemented by utilizing the remained battery energy information or ensuring the minimal neighbor number. By simulating the algorithms, we analyze the effect of parameters and compare the performance of related algorithms. By LQA-TC, while neighboring node degree increases slightly, total path energy consumption and interfering degree decreases. By LBA-TC, the lifetime of network is prolonged significantly, when the standard of lifetime is setting as the ending time when more than 90% nodes are still alive. |
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