在無線的環境中，IEEE 組織已經為無線區域網路訂下了標準，也就是IEEE802.11。在IEEE802.11 中，不管是資料封包或是控制封包皆是採用最大固定的能量(power)來傳送。因此對於如何避免原本隱藏和曝露工作站的問題，來提高無線行動網路通道使用率，就是個很重要的研究了。最近幾年來，已經有許多被提出來的MAC 協定結合能量控制的機制來達到這個目的。例如RTS/CTS 封包的傳送是用最大固定的能量，而Data/ACK 封包只用最小所需能量來傳送。但是在傳送Data 的同時，必須週期性的將能量調到最大來傳送。然而這樣的方法雖然可以預防隱藏工作站的問題出現在傳送端，卻無法克服隱藏工作站的問題出現在接收端。

　　在論文中我們提出一動態功率控制的MAC 協定， 是利用一分割通道的HI 封包來相互收集工作站之間的位置資訊。根據這些資訊，每個工作站皆可以建立屬於自己的能量表(power table)。然而在依據這些能量表，每個工作站可以利用適當的能量去傳送， 而且亦可在不干擾其他正在傳輸的工作站之情況下， 對其他工作站進行通訊。我們會經由詳細的模擬驗證此MAC 協定，並顯示出此協定可達到改善有效封包到達率與節省能量消耗之成效。

　Typically, the media access control (MAC) protocol in wireless network, like IEEE802.11, adopts fixed maximum power level to transmit either data packets or control packets. However, how to avoid the hidden-terminal and the exposed-terminal is an important problem to increase channel utilization in mobile Ad-hoc networks (MANET). Recently, several proposed MAC layer protocols have incorporated the power control mechanism to achieve the goal. For example, the RTS/CTS handshake is done at the maximum, and the Data-ACK are transmitted at the minimum necessary transmission power. It also has to use maximum transmission power periodically during data transmission. However, using the maximum transmission power in RTS/CTS handshake does not solve the hidden node problem in receiver.

　In this thesis, we propose an Adaptable Power Control MAC (APCMAC) Protocol that uses a Channel-Separated HI message to mutual collect power level information. According to the power level information, each node can establish its power table. However, depend on the power table, each node can use suitable power level to transmit and communicate for some special cases without colliding other on-going transmissions. We validate APCMAC protocol via detailed simulations to show that it can improve throughout and achieve power saving.

[1] IEEE Standard 802.11a, Part II, “Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications: High Speed Physical Layer Extension in the 5GHz Band,” Tech. Rep., IEEE, 1999.
[2] IEEE Standard 802.11b, Part II, “Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications: High Speed Physical Layer Extension in the 2.4GHz Band,” Tech. Rep., IEEE, 1999.
[3] Amre El-Hoiyidi “Implementation Options for the Distribution System in the 802.11 Wireless LAN Infrastructure Network,” IEEE Network, 2000.
[4] Andrew S. Tanenbaum “Computer Networks,” Prentice-Hall, Inc., 1996.
[5] NCTUns web site, available at http://nsl10.csie.nctu.edu.tw
[6] J.P. Monks, V. Bharghavan, and W. Hwu, “A power controlled multiple access protocol for wireless packet networks,” IEEE INFOCOM ’01, vol.20, pp. 1 – 11, April 2001.
[7] A. Lindgren and O. Schelen, “infrastructured ad hoc networks,” In Proceedings of International Conference on Parallel Processing Workshop, pp. 64 – 70, August 2002.
[8] S. Agarwal, S. Krishnamurthy, R.H. Katz, and S.K. Dao, “Distributed Power Control in Ad-Hoc Wireless Networks,” In PIMRC, 2001.
[9] Rong Zheng and R. Kravets, “On-demand power management for ad hoc networks.” IEEE INFOCOM ’03, vol. 1, pp. 481 – 491, April 2003.
[10] E.S. Jung and N.H. Vaidya. “A Power Control MAC Protocol for Ad Hoc Networks,” In MOBICOM 2002, Sep, 2002.
[11] E.S. Jung and N.H. Vaidya. “An Energy Efficient MAC Protocol for Wireless LANs.” IEEE INFOCOMM 2002.
[12] J. Li, C. Blake, D. Coute, H. Lee and R. Morris, “Capacity of ad hoc wireless networks.” In MOBICOM, July 2001.
[13] S. L. Wu, Y. C. Tseng, and J. P. Sheu. “Intelligent Medium Access for Mobile Ad Hoc Networks with Busy Tones and Power Control.” IEEE Journal on Selected Areas in Communications, 18(9):1647–1657, September 2000.
[14] T. Issariyakul, E. Hossain, and D. I. Kim, “Medium access control protocols for wireless mobile ad hoc networks: Issues and approaches,” Wiley Interscience Wireless Communications and Mobile Computing (WCMC), vol. 3, no. 8, Dec. 2003.
[15] J. G. Proakis, Digital Communications, 3rd Ed., New York: McGraw-Hill, 1995.
[16] J. Gomez, A. T. Campbell, M. Naghshineh, and C. Bisdikian, “Conserving Transmission Power in Wireless Ad Hoc Networks,” Proceedings of Network Protocols Ninth International Conference, pp. 24-34, 2001.
[17] X.-H. Lin, Y.-K. Kwok, and V.K.N. Lau, “Power Control for IEEE802.11 Ad Hoc Networks: Issues and a New Algorithm,” Proceedings of the 2003 International Conference on Parallel Processing (ICPP'2003), pp. 249-256, Kaohsiung, Taiwan, China, October 2003.
[18] K. Xu, M. Gerla and S. Bae, “Effectiveness of RTS/CTS Handshake in IEEE 802.11 based Ad Hoc Networks.” Ad Hoc networks Journal, Volume 1, Issue 1, July 2003.
[19] J. B. Andersen, T. S. Rappaport, and S. Yoshida. “Propagation Measurements and Models for wireless Communication Channels,” IEEE Communication Magazine, vol. 33, pp. 42-49, Jan. 1995.
[20] J. Deng and Z. J. Haas, “Dual Busy Tone Multiple Access (DBTMA): A NEW Medium Access Control for Packet Radio Networks,” Proceedings of IEEE International Conference on Universal Personal Communications, pp. 973-977, 1998.
[21] H. Woesner, J. P. Ebert, M. Schlager, and A. Wolisz, “Power-Saving Mechanisms in Emerging Standards for Wireless LANs: The MAC Level Perspective,” IEEE Personal Communications, June 1998.
[22] J. P. Ebert, B. Stremmel, E. Wiederhold, and A. Wolisz, “An Energy-efficient Power Control Approach for WLANs,” Journal of Communications and Networks (JCN), 2(3): 197-206, September 2000.
[23] J. C. Cano and P. Manzoni, “A low power protocol to broadcast real-time data traffic in a clustered ad hoc network,” IEEE CLOBECOM ’01, vol. 5, pp. 2916-2920, November 2001.
[24] Y. B. Ko, V. Shankarkumar, and N. H. Vaidya, “Medium Access Control Protocols Using Directional Antennas in Ad Hoc Networks,” Proceedings of IEEE INFOCOM ’2000, March 2000.
[25] Dhananjay Lal, Rahul Gupta, and Dharma P. Agrawal, “Throughput Enhancement in Wireless Ad Hoc Networks with Spatial Channels- A MAC Layer Perspective,” Proceedings of the Seventh IEEE Symposium on Computers and Communications, Taormina, Italy, July 2002.
[26] Yu Wang and J. J. Garcia-Luna-Aceves, “Spatial reuse and collision avoidance in ad hoc networks with directional antennas,” GLOBECOM ’02, IEEE, Volume: 1, pp. 112-116, Nov. 2002.
[27] R. Radhakrishnan, Lai Dhananjay, J. J. Caffery, and D. P. Agrawal, “Performance Comparison of Smart Antenna Techniques for Spatial Multiplexing in Wireless Ad Hoc Networks,” The 5th International Symposium on Wireless Personal Multimedia Communications, Volume: 1, pp. 168-171, Oct. 2002.
[28] L. Raju, S. Ganu, B. Anepu, I. Seskar and D. Raychaudhuri, “Beacon assisted discovery protocol (BEAD) for self-organizing hierarchical ad-hoc networks,” Global Telecommunications Conference, 2004. GLOBECOM '04. IEEE Volume 3, 29 Nov.-3 Dec. 2004 Page(s):1676 - 1680 Vol.3.