在無線通訊網路的領域，為了提升系統表現以及增加頻寬效益，近幾年來合作式通訊的技術已經愈發顯得重要。在本篇論文中，我們著重於討論使用合作式多工通訊技術以及如何延長整體網路的運作存活時間。在無線通訊裡，
增加合作式多工的增益能夠使訊雜比升高或者讓需要的傳輸功率下降。因為如此，許多研究者已將之視為重要的議題持續深入探討。另一方面，在資源有限的無線網路系統中有效率的使用能源是很重要的議題，所以延長整體網路的運作存活時間就是一個重要的指標。有鑑於上述兩個部分，幾個在不同中繼網路技術中的合作式策略目前正被廣泛討論。
在文章中，幾個重要的文獻利用中繼網路的使用公平性來切入延長整體網路的運作存活時間這個問題。研究者設計了一套兼顧傳輸功率效益和能量損耗的選擇中繼點演算法來達到延長整體網路的運作存活時間的目標。
在論文中，我們提出了一個新的演算法來進一步提升網路運作存活時間的表現。其中包括了適應性的運作存活時間閾值，它可以依照每個中繼點的平均傳輸能量去微調不同的閾值，在兼顧通訊品質以及個中繼點能源損耗之外提高整體網路的運作存活時間。

In this paper, what we focus on is using cooperative diversity and prolonging lifetime of the whole wireless network. In wireless communications, increasing diversity gain is a way to increase SNR or decrease transmission power, and it becomes a topic that lots of researchers focus on. The lifetime of the whole wireless network is the other important topic which we should pay attention on. The efficient usage of energy is an important issue in a resource-limited wireless network. There are several cooperative strategies in different relaying techniques which have been discussed recently.
In the literature, some important research works has addressed the issue of prolonging network lifetime by emphasizing the fairness in the relay network.
To prolong the lifetime of overall network, this works designed the utility function with consideration of transmission power efficiency and energy consumption both.
We propose a modified utility function by using an adaptive lifetime threshold, which is adjusted according to the average power consumption of each relay node. With the aid of the adaptive threshold, the fairness of power consumption between relay nodes and overall network performance in terms of lifetime can be improved.
The rest of paper is organized as follows. In Chapter II, the system model is described including channel model, definition of network lifetime and outage probability. In Chapter III, we introduce few cooperative relay selection methods and propose an Adaptive proportional-fairness relay selection scheme.
After demonstrating the simulation results in Chapter IV, we make a conclusion in Chapter V.

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