臺灣博碩士論文加值系統

隨著時間的演進，分散式系統(Distributed System)在90年代演進到行動計算(Mobile Computing)，而最近行動計算又被瀰合計算(Pervasive Computing)所取代[18]。在此同時，為了滿足人類行為的移動性，無線科技取代了有線的技術，例如：行動電話取代了傳統電話，無線區域網路取代了有線區域網路。輕薄的裝置(例如：筆記型電腦和個人數位助理)取代了厚重的裝置滿足了裝置可攜性。
瀰合計算的特性除了充滿計算和通訊能力的環境，還要使這樣的環境和人之間有著優雅且舒適的整合。在這種環境下，使用者可以透過他的無線裝置，隨時隨地的進行計算，通訊。
藍芽技術（Bluetooth）是一種操作在ISM頻段的新的通訊技術，他的特性是低價，低功率，及距離短。因為他輕薄而且可以和任何裝置整合的特性，被認為蠻適合瀰合計算。因為ISM頻段不用執照的特性，藍芽可能遭遇來自微波，其他通訊裝置，或其他藍芽裝置的干擾。當干擾嚴重時，藍芽可能必須執行重送封包很多次，而引起傳輸延遲和過份耗電的效應。
藍芽技術主要的干擾來源可以是其他的藍芽裝置，也可以是無線區域網路(IEEE 802.11) 。來自其他藍芽裝置的干擾可能分散在整個ISM 頻段，不容易預測在下個時槽會干擾哪些頻道。而來自無線區域網路的干擾則集中在某個子頻段且較可預期。
如果一個裝置可以智慧的偵測網路狀況並根據網路狀況自行調整其媒體擷取控制的方法，則可以避免在媒體傳輸層的傳輸碰撞。在這篇論文，我們提出了一種由藍芽主裝置（Bluetooth master）根據封包錯失率來偵測網路狀態的方法，並根據網路狀態提出相對應的媒體擷取方法。我們使用所謂的封包排程和暫停某個頻段的傳輸來處理無線網路導致的干擾，當來自其他藍芽裝置的干擾嚴重時，我們使用隨機退回重傳的方法來解決干擾過於嚴重的問題。藉由這些機制，我們可以達到省電，省時及增加網路生產量的效果。

As time goes on, distributed computing evolved into mobile computing in 90s, and then pervasive computing substitutes mobile computing recently [18]. Specifically, existing wired technologies are going to be enhanced or complimented by novel wireless technologies, e.g., mobile phone, and wireless LAN in replace of traditional phone and wired LAN. Light and thin computing devices (e.g., notebook, PDA) supersedes heavy and thick devices for portability. Pervasive computing environment could be characterized as one saturated with computing and communication capability, yet elegant integrated with human users.
Bluetooth, a short range, low power, and low cost radio technology operating in ISM band plays an critical role to enable pervasive computing due to the ability to be embedded in any type of device. Since the ISM band is license-free, Bluetooth might experience interference from other wireless communication systems, or even Bluetooth devices themselves. Once the interference occurs, packets of transmission may be dropped seriously. Bluetooth may retransmit a packet several times and it costs power and time.
Two major types of interferences could jeopardize Bluetooth connections. Caused by other overlapping Bluetooth devices, the influence may interfere the current discrete channels, and leave uncertainty of interfering the next slot since the characteristic of FHSS. The other type of interference source may come from WLAN. This type may interfere in a continuous sub-band and the interference is predictable.
A modern device will be highly expected to have an intelligent policy for probing wireless environment and adjusting its medium access method to avoid transmission collision in MAC layer (media access control). This thesis proposes a new MAC mechanism based on the information probed by the master. The proposed protocol adopts a packet scheduler and a suspension scheme in a sub-band to cope with interference caused by WLAN. As the interference caused by other Bluetooth piconets gets serious, the proposed mechanism exploits a random backoff algorithm to resolve it. Through the simulation and analytical experiments, the probing-based MAC will reduce power consumption, reduce the packet delay, and upgrade the system throughput.

摘 要 I
Abstract III
Table of Contents V
List of Figures VIII
List of Tables X
Chapter 1 Introduction 1
1.1 Bluetooth technology and pervasive computing environment 2
1.1.1 Bluetooth technology 2
1.1.2 Bluetooth physical layer 3
1.1.3 Bluetooth medium access control protocol 4
1.1.4 Bluetooth application and pervasive computing scenario 5
1.2 IEEE 802.11b technology and hot spot deployment 7
1.2.1 IEEE 802.11 technology 7
1.2.2 IEEE 802.11b physical layer 9
1.2.3 IEEE 802.11b MAC layer 10
1.2.4 WLAN application and hot spot deployment 14
1.3 Interference problem in the ISM band 15
1.4 Intelligent solution for interference avoidance 16
Chapter 2 Related work 18
2.1 Transmission problem overview 18
2.2 Research category and related work 24
2.2.1 Piconet Interference Modeling and performance Evaluation of Bluetooth MAC protocol 24
2.2.2 Radio Network Performance of Bluetooth 25
2.2.3 Considerations on Link and System Throughput of Bluetooth Networks 25
2.2.4 Performance Evaluation of a Bluetooth Network in the Presence of Adjacent and Co-channel Interference 26
2.2.5 Interference Between Bluetooth Networks─Upper Bound on the Packet Error Rate 26
2.2.6 Bluetooth Voice and Data Performance in 802.11 DS WLAN environment 27
2.2.7 Interference in the 2.4GHz ISM Band: Impact on the Bluetooth Access Control Performance 28
2.2.8 Bluetooth and 802.11b Interference: Simulation Model and System Results 28
2.2.9 Wi-Fi (802.11b) and Bluetooth: Enabling Coexistence 29
2.2.10 Interference Aware Bluetooth Packet Scheduling 31
2.3 Contribution of this research 31
Chapter 3 System description and proposed mechanism 33
3.1 System architecture 33
3.2 Proposed mechanism: PBMAC 36
Chapter 4 Mathematic analysis 49
4.1 Analysis of the interference from Bluetooth 49
4.2 Analysis of the interference from WLAN 53
4.3 Analysis of interference from Bluetooth and WLAN 55
4.4 Power consumption analysis 56
Chapter 5 Simulation results 58
5.1 Simulation environment assumptions 58
5.2 Simulation result 60
Chapter 6 Conclusion 64
References 65

[1] J. Bray, and C. F. Stuman, Bluetooth Connect Without Cables, Prentice Hall, First Edition 2001.
[2] I. Chakraborty, A. Kashyap, A. Rastogi, H. Saran, R. Shorey, and A. Kumar, “Policies for increasing throughput and decreasing power consumption in Bluetooth MAC,” IEEE International Conference on Personal Wireless Communications, 2000, pp. 90 —94.
[3] C. de Morais Cordeiro, D. Sadok, and D.P. Agrawal, “Piconet interference modeling and performance evaluation of Bluetooth MAC protocol,” IEEE Global Telecommunications Conference, 2001, vol. 5, pp. 2870 —2874.
[4] B.P. Crow, I. Widjaja, L.G. Kim, and P.T. Sakai, “IEEE 802.11 wireless local area networks,” IEEE Communication Magazine, vol. 35, issue. 9, Sept. 1997, pp. 116-126.
[5] S. Garg, M. Kalia, and R. Shorey, “MAC scheduling policies for power optimization in Bluetooth: a master driven TDD wireless system,” Vehicular Technology Conference Proceedings, 2000, IEEE 51st, vol. 1, pp. 196 -200.
[6] N. Golmie, “Bluetooth and 802.11 interference: simulation model and system results,” IEEE 802.15-01/195R0, Apr. 2001.
[7] N. Golmie and F. Mouveaux, “Interference in the 2.4 GHz ISM band: impact on the Bluetooth access control performance,” IEEE International Conference on Communications, 2001, vol. 8, pp. 2540 -2545.
[8] N. Golmie, N. Chevrollier, and I. ElBakkouri, “Interference aware Bluetooth packet scheduling,” IEEE Global Telecommunications Conference, 2001, vol. 5, pp. 2857-2863.
[9] J. C. Haartsen, “The Bluetooth radio system,” IEEE Personal Communications, Feb 1, 2000, vol. 7, pp. 28-36.
[10] J. C. Haartsen and S. Mattisson, “Bluetooth--a new low-power radio interface providing short-range connectivity,” IEEE Proceedings, 2000, vol. 88, no. 10, pp. 1651-1661.
[11] J. C. Haartsen and S. Zurbes, “Bluetooth voice and data performance in 802.11 DS WLAN environment,” SIG publication, 1999.
[12] El-Hoiydi A., “Interference between Bluetooth networks-upper bound on the packet error rate,” IEEE Communications Letters, June 2001, vol. 5 issue. 6, pp. 245 —247.
[13] IEEE Std. 802-11, “IEEE standard for wireless LAN medium access control (MAC) and physical layer (PHY) specification,” June 1997.
[14] M. Kalia, D. Bansal, and R. Shorey, “MAC scheduling and SAR policies for Bluetooth a master driven TDD pico-cellular wireless system,” IEEE International Workshop on Mobile Multimedia Communications, 1999, pp. 384 —388.
[15] M. Kalia, D. Bansal, and R. Shorey, “Data scheduling and SAR for Bluetooth MAC,” Vehicular Technology Conference Proceedings, 2000, IEEE 51st, vol. 2, pp. 716 —720.
[16] J. Lansford, A. Stephens, and R. Nevo, “Wi-Fi (802.11b) and Bluetooth: enabling coexistence,” IEEE Network, vol. 15, issue. 5, pp. 20 —27, 2001.
[17] K. J. Negus, A. P. Stephens, and J. Lansford, “HomeRF: wireless networking for the connected home,” IEEE Personal Communications, February 2000, pp. 20-27.
[18] M. Satyanaraynan, "Pervasive computing: vision and challenges", IEEE Personal Communication Magazine, August 2001, pp. 10-17.
[19] Bluetooth Special Interest Group, “Specifications of the Bluetooth system, version1.1,” February 22, 2001.
[20] S. Souissi, E. F. Meihofer, “Performance evaluation of a Bluetooth network in the presence of adjacent and co-channel interference,” IEEE Emerging Technologies Symposium: Broadband, Wireless Internet Access, 2000, 6 pp.
[21] A. S. Tanenbaum, Computer Networks, Prentice Hall, Third Edition 1996.
[22] S. Ziirbes, W. Stahl, K. Matheus, and J. Haartsen, “Radio network performance of Bluetooth,” IEEE International Conference on Communications, 2000, vol. 3, pp. 1563-1567.
[23] S. Zurbes, “Considerations on link and system throughput of Bluetooth networks,” The 11th IEEE International Symposium on Personal, Indoor and Mobile Radio Communications, Sept. 2000, pp. 1315-1319.