無線感測網路(wireless sensor networks)是一種不同於傳統網路新興的改革性技術，結合科技與生活帶給人類更多的舒適與實利。最近公佈的一份 IEEE 802.15.4 規格書就是專門為這類低功耗、低資料量的無線個人區域網路 (LR-WPAN) 所制定的標準。隨著無線感測網路越來越受重視，相關的系統內部運作之最佳化與校調就顯的非常重要。在無線感測網路設計建構中，由於硬體上的限制，使得省電措施不可或缺。因此在本論文中，我們針對提升能源效率 (energy efficiency) ，提出並且詳細敘述一組分析的模型，我們稱之為延伸性的線性反饋模型(extended linear feedback model) 。我們利用這組模型來分析無線感測網路在資料傳輸時必須耗費的電量。 最後，評估與模擬的數據結果顯示，資料傳輸時所使用的載波感測多重多重存取協定 (CSMA protocol) 如果採用固定的競爭時框 (contention window) 所必須耗費的電量會比採用二進指數退避 (binary exponential backoff) 少。另外，在採用固定競爭時框的載波感測多重多重存取協定的運作過程中，我們可以找出一個最佳的競爭時框值，使得資料可以透過最少的耗電量被成功的傳輸。 Wireless sensor network, a revolutionary technology of the traditional network, attracts lots of researchers with new applications. While the recently released IEEE 802.15.4 standard has given us a general inspection over the implementation of wireless sensor networks, specifically analyzing and optimizing some details in MAC layer seems practical and vital. Motivating by the importance of energy conservation in wireless sensor networks, this thesis focuses on providing an in-depth study on the analytical model modifies from linear feedback model in order to deal with the binary exponential backoff mechanism adopted in IEEE 802.15.4 CSMA/CA and improving the energy efficiency with this analytical model. The numerical results show that the energy consumption in wireless sensor networks can be reduced by applying CAMA protocol with fixed contention window. Besides, an optimal contention window that achieves best effective energy consumption is derived from the use of fixed contention window. Effective energy consumption is defined as the minimum energy consumption for successful packet transmission.
