在標準的IEEE 802.11通訊協定裡規定每個行動工作站在對每個封包做傳輸時，都是採用最大的傳輸功率來進行傳輸動作。然而，在Ad Hoc無線區域網路環境中，能源對於行動工作站而言是一項非常重要的資源。過去此類有關power control方面的研究也是相當熱門。這些power control的方法大都採用不同的power level以及分割網路頻道技術來達到節省能源消耗以及避免碰撞的發生，並且增加網路頻道的使用率。好景不常，當行動工作站利用power control動態調整傳輸功率範圍時，能源是節省了，但是相對的問題也油然而生了，一個比較顯著的問題就是造成了每一個行動工作站的傳輸功率範圍都不一樣，導致了額外的hidden terminal問題產生，即所謂的heterogeneous power terminal problem。然而，這個問題經常被忽略。因此，在這篇論文中，我們提出了一個簡單且有效的方法來解決行動工作站在動態調整傳輸功率範圍時所產生的heterogeneous power terminal problem，使得行動工作站本身可以節省能源之外又可以避免不必要的碰撞機會發生，並且同時又能增加網路頻道使用率。

The standard IEEE 802.11 MAC protocol assumes that each mobile host uses maximum transmission power for the transmission of each packet. However, energy is very valuable resources for mobile host in ad hoc wireless network. In the past, several researches about power control were proposed. These power control schemes use different power levels and one more separate power control channel in order to save energy, avoid occurrence of collision, and increase network channel utilization. But various power levels lead to each mobile host having different transmission power ranges, and cause the additional hidden terminal problem, namely heterogeneous power terminal problem. Therefore, in this paper, we propose a simple and efficient power control protocol that used dynamic adjustment transmission power ranges to reduce power consumption, avoid collision, increase the network channel utilization, and ease heterogeneous power terminal problem as well.

1 Introduction 1
1.1 Introduction 1
1.2 Motivation 4
1.3 Paper Organization 5
2 Background and Related Work 6
2.1 CSMA/CA of IEEE 802.11 MAC Protocol 6
2.2 Transmission Power Range 9
2.3 Power Control Protocols 10
2.3.1 A Novel Link State Routing Protocol and TCP Performance Investigation in Ad Hoc Networks 10
2.3.2 PCM 12
2.3.3 PCMA 12
2.3.4 DBTMA 14
2.3.5 Intelligent Medium Access for Mobile Ad Hoc Networks with Busy Tones and Power Control 16
2.4 Heterogeneous Power Terminal Problem 19
2.4.1 Medium Access Control in a Network for Ad Hoc Mobile Nodes with Heterogeneous Power Capabilities 19
2.4.2 An Efficient MAC Protocol in Wireless Ad-Hoc Networks with Heterogeneous Power Nodes 20
3 Proposed Scheme 22
3.1 Efficient Power Control MAC Protocol 22
3.1.1 Basic Idea 22
3.1.2 Transmission Power Level 23
3.1.3 Channel Split 23
3.1.4 Solution of Heterogeneous Power Terminal Problem 24
4 Simulation and Analysis 28
4.1 Simulation Environment 28
4.2 Simulation Result 29
4.2.1 power consumption 29
4.2.2 successful transmission session 31
4.2.3 collision 33
5 Conclusion 36
Reference 37

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