How to save energy is critical in wireless networks. Most of mobile devices are batteryoperated with energy constraints. Therefore, energy-efficienct protocols are required to extend battery lifetime.
In this thesis, we first present Maximum Unavailability Interval (MUI), to improve the energy efficiency for the Power Saving Class (PSC) of Type II in IEEE 802.16e. By applying the Chinese Remainder Theorem, the proposed MUI is guaranteed to find the maximum Unavailability Interval, during which the transceiver can be powered down. We also propose new mathematical techniques to reduce the computational complexity when solving the Chinese Remainder Theorem problem. Because the computational complexity is reduced significantly, the proposed MUI can be practically implemented in real systems. The proposed MUI is fully compatible with the 802.16e standard. It provides a systematic way to determine the start frame number, one of the important parameters defined in the standard. In addition to analyzing the computational complexity, simulations and experiments are conducted to evaluate the performance of the proposed algorithms.
To conserve energy in IEEE 802.16e, MUI is guaranteed to find the maximum unavailability interval. Thus, energy consumption can be reduced significantly. In this thesis, we
further extendMUI for unicast traffic which includes Type I and Type II PSCs. The proposed eMUI still can achieve maximum unavailability interval. The simulation results show that the proposed eMUI reduces energy consumption and average packet response time.
In IEEE 802.16j, relays are added into IEEE 802.16 systems. A relay network can be considered as one type of multihop wireless networks. Also, network coding is a promising way to improve network performance. In this thesis, we further consider practical use of network coding and propose an energy-efficient routing algorithm for multihop wireless networks by exploiting coding opportunities. In the presence of energy constraints, the proposed coding-aware algorithm aims to maximize the total amount of data routed successfully over the network. We derive the competitive ratio to compare the proposed on-line algorithm with the optimal off-line algorithm which knows the information of future flow arrivals. The
competitive ratio shows that the proposed algorithm can achieve the performance which is bound to a factor of the best case. From a practical perspective, the proposed algorithm is also evaluated and compared with other algorithms by extensive simulations. Results show that the proposed algorithm can increase the amount of data routed successfully and reduce the energy consumption.

無線網路中，受到電池電力的限制，行動裝置如何有效地節能是
一大議題。
本論文首先針對IEEE 802.16e，提出了一套省電演算法，稱為
Maximum Unavailability Interval（MUI）。MUI 利用中國餘式定理
（Chinese Remainder Theorem），在給定的各個Type II Class 下，只需動態調整一參數，便能有效保證行動裝置獲得最大的睡眠時間，可大幅減少通訊中所產生的電力消耗。此外，本論文亦提出另一套演算法來降低MUI 的計算複雜度，此演算法並完全相容於802.16e 的標準。透過電腦模擬的結果，驗證了各項創新演算法。此研究最大之特點，在於巧妙地應用「中國餘式定理」，只要調整start frame
number，由數學理論保證MUI 可獲得「最大」的睡眠時間。
本論文更提出一同時考慮Type I Class 的省電機制，稱為eMUI，
eMUI 依舊能保證獲得「最大」的睡眠時間，透過模擬，結果顯示eMUI可以減少電能消耗和封包回應的平均時間。
IEEE 802.16j 標準中，中繼站（Relay）的概念被提出，中繼站
網路可被視為多節點網路的一種。此外，利用網路編碼（Network
Coding）已被證明可以改善網路效能，本論文的第二部分利用網路編
碼提出了一套節能的路徑演算法於多節點網路中，此演算法透尋找編
碼的機會，找出最佳節能的路徑。在給定的電力限制下，此演算法能
使成功被傳送的資料達到最多。本論文並推導出此演算法和最佳化演
算法所能傳的資料比例（competitive ratio），證明此演算法與最佳化演算法的效能差距小於某個值。利用模擬分析，此演算法與其他既有的方法比較，結果顯示此演算法能增加整體資料的傳輸量並減低電能的消耗。

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