當我們處在無線網路的環境時，使用多重跳躍（multihop）的轉傳通訊取代單一跳躍（single hop）的直接通訊是否可以得到更好的系統效能？我們設計一個新的方法，稱做PESR（Performance Enhancement of IEEE 802.11 by Spatial Reuse），是在802.11標準上，利用空間重利用（spatial reuse）的特性，來追求更高的系統效能。PESR搭配功率控制（power control）的機制，在來源節點和目的節點之間選擇一個適當的中間點負責將來源節點的資料封包（packet）轉傳給目的節點，使單一跳躍通訊變成多重跳躍通訊；如此，一時間內可提供更多通訊同時進行，搭配空間重利用的優勢，來提升系統效能。然而，在這其中有許多額外的負載，例如：使用多重跳躍通訊比使用單一跳躍通訊需要更長的時間延遲（delay），或者因為有更大量的通訊同時進行，發生碰撞（collision）與資料遺失（data lost）的機率因此提高等。根據第五章的實驗結果顯示，雖然PESR確實因空間重利用提升了頻道使用率（channel utilization），然而負面的負載卻打擊了這個優勢，使得平均下來，PESR的表現仍然比單一跳躍的直接通訊要差，所以我們認為使用多重跳躍通訊取代單一跳躍通訊並非絕佳的選擇。

We question about multihop gets better performance than single hop in wireless networks. In this paper we design a new and simple multihop transmission model called PESR, performance enhancement of IEEE 802.11 by spatial reuse. We elect an intermediate node which between a source-destination pair for forwarding packets to become multihop instead of directly transmission from the source to the destination. By this way, we will have more links at the one time, the channel utilization should be grown and we will get better system performance. However, there is much overhead we have not considered. We will discuss the detail about overhead in coming sections. In fact, the results of simulation show that the performance is not present very well. And we wonder if the multihop in wireless networks is a pretty good idea.

中文摘要 2
英文摘要 3
第一章 導論 7
第二章 相關工作 12
第三章 演算法 15
第四章 實驗與結果 22
第五章 結論與未來工作 27
第六章 參照 28

[ 1]A. Acharya, A. Misra and S. Bansal,”A Label-switching Packet Forwarding Architecture for Multi-hop Wireless LANs”, WoWMoM 2002.
[ 2]D. Bertsekas and R. Gallager, Data networks, NJ: Prentice-Hall, Inc, 1987.
[ 3]L. Bonomi, M. Conti, L. Donatiello, ”Design and Performance Evaluation of a Distributed Contention Control (DCC) Mechanism for IEEE 802.11 Wireless Local Area Networks”, WOWMOM 98 Dallas Texas USA.
[ 4]L. Bonomi, M. Conti, L. Donatiello, “A Distributed Mechanism for Power Saving in IEEE 802.11 Wireless LANs”, In proceedings of Mobile Networks and Applications 6.211-222,2001.
[ 5]B. Chen, K. Jamieson, H. Balakrishnan, and R. Morris, ”Span: An Energy-Efficient Coordination Algorithm for Topology Maintenance in Ad Hoc Wireless Networks”, IEEE MobiCom Conference, 2001.
[ 6]L. Feeney and M. Nilsson, “Investigating the Energy Consumption of a Wireless Network Interface in an Ad Hoc Networking”. In proceedings of IEEE Infocom 2001.
[ 7]J. Gomez, A. T. Campbell, M. Naghshineh, and C. Bisdikian. “Conserving Transmission Power in Wireless Ad Hoc Networks”, In ICNP November 2001.
[ 8]G. Hoiland and N. Vaidya, “A Rate-Adaptive MAC Protocol for Multi-Hop Wireless Networks”, In proceedings of MOBICOM 2001.
[ 9]T. C. Hou and V. O. K. Li, “Transmission range control in multihop packet radio network”, IEEE Trans. Commun. 34(1986).pp 38-44.
[ 10]N.-F. Huang, Local Area Network and High-speed Network, Wei-Keg 1996.
[ 11]E.S. Jung and N.H. Vaidya, ”A Power Control MAC Protocol for Ad Hoc Networks”, In proceedings of MOBICOM 2002.
[ 12]J. P. Monks, V. Bharghavan, and W. W. Hwu, “A Power Controlled Multiple Access Protocol for wireless Packet Networks”, Proceedings of IEEE INFOCOM 2001.
[ 13]K. Paul and S. Bandyopadhyay, “Self-Adjusting Transmission Range Control of Mobile Hosts in Ad Hoc Wireless Networks for Stable Communication”, Proceedings of the Sixth International Conference on High Performance Computing HiPC99,Calcutta, India, December 1999.
[ 14]W. M. Seifert, “Bridges and routers”, IEEE Network , Volume: 2 Issue: 1,Jan 1988 Page(s): 57 -64
[ 15]X. Yang and N. H. Vaidya, “Priority Scheduling in Wireless Ad Hoc Networks”, In proceedings of MOBIHOC'02