臺灣博碩士論文加值系統

在無線網路普及的現代，封包傳送效率日趨重要，碰撞的發生與傳送效率極為相關。在無線網路避免碰撞的機制中，IEEE 802.11 DCF協定與IEEE 802.15.4 CSMA/CA協定是最廣為人知的。他們主要的不同一是監聽通道狀態的方式與次數。在DCF協定中，節點不斷的偵測通道狀態，對通道狀態可以立即性的處理；在IEEE 802.15.4 CSMA/CA協定下，節點只會在backoff結束後偵測通道一次，期間若通道已被佔用是無法得知的。此篇論文主要是於IEEE 802.15.4晶片上建構與實現基於DCF協定的軟體架構，與IEEE 802.15.4 CSMA/CA協定進行比較。實驗成果呈現出，由於IEEE 802.15.4 CSMA/CA沒有持續偵測通道，其傳送失敗率會隨網路變大而急遽上升。因此，IEEE802.11 DCF協定在封包遺失率與整體吞吐量上是優於IEEE 802.15.4 CSMA/CA協定。

Wireless networks are widely popular in modern. The collision occurring is one of the reasons affecting the transmission efficiency. To mitigate the collision issue, the carrier sensing multiple access with collision avoidance (CSMA/CA) protocol is widely applied in wireless networks. IEEE 802.11 DCF protocol and IEEE 802.15.4 CSMA/CA protocol are the most well-known CSMA/CA based protocols. The primary difference between them is how carrier sensing is performed. Stations continuously sense the medium before transmissions in an IEEE 802.11 network, while stations in an IEEE 802.15.4 network only sense once after backoff operation. The thesis is mainly about software architecture design of the IEEE 802.11 DCF protocol on an IEEE 802.15.4 transceiver. Experiment results show that, without continuously sensing, the transmission failure probability of IEEE 802.15.4 CSMA/CA increases dramatically with the network size. Consequently, the IEEE 802.11 DCF protocol provides better performance in the packet loss probability and throughput than IEEE 802.15.4 CSMA/CA does.

Chapter 1 Introduction 1
1.1 Background 1
1.2 Investigated system 2
1.3 Anticipated Achievement 4
Chapter 2 CSMA based protocols 5
2.1 IEEE 802.11 5
2.1.1 DCF 5
2.2 BEB scheme 7
2.1.2 Acknowledgment 9
2.3 IEEE 802.15.4 10
2.2.1 IEEE 802.15.4 CSMA/CA 10
2.4 Difference between DCF and IEEE 802.15.4 CSMA/CA 11
Chapter 3 Software Architecture and Implementation 13
3.1 Software related 13
3.1.1 Interrupt service routine 14
3.1.2 Timer 2 15
3.1.3 Contention Window 19
3.1.4 Frame Filtering 20
3.1.5 RF radio 21
3.1.6 AUTOACK Mechanism 23
3.1.7 Carrier Sense 25
3.1.8 Radio status 26
3.1.9 Subroutine Introducing 27
3.1.10 TI MAC introduction 32
3.2 Hardware related 33
3.2.1 Radio states 33
3.2.2 Synchronous Transmission 35
3.2.3 RSSI 37
3.2.4 Capture Effect 40
3.2.5 Summary 41
Chapter 4 Performance Evaluation 43
Chapter 5 Conclusions 49
Reference 50

[1]IEEE Standard for Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications,” IEEE Std 802.11- 2012

[2]IEEE Standard for Local and metropolitan area networks— Low-Rate Wireless Personal Area Networks (LR-WPANs)- 2011.

[3]CC253x System-on-Chip Solution for 2.4-GHz IEEE 802.15.4 and ZigBee® Applications- User’s Guide.

[4]Giuseppe Bianchi, “Performance Analysis of the IEEE 802.11 Distributed Coordinator Function,” IEEE Journal on Selected Area in Communications, vol.18, pp.535-547, 2000.

[5]C. Wang, W. Tang, “A Probability-based Algorithm to Adjust Contention Window in IEEE 802.11 DCF,” Communications, Circuits and Systems, 2004. ICCCAS 2004. 2004 International Conference, June 2004.

[6]Wang Xiaofan, Chong, P.H.J.; Leong Wai Yie, “Evaluation of Performance on Random Back-off Interval and Multi-channel CSMA/CA Protocols,” TENCON 2009 – 2009 IEEE Region 10 Conference, Jan. 2009.

[7]Meerja Khalim Amjad, and Abdallah Shami, “Improving the Throughput Performance of IEEE 802.11 Distributed Coordination Function,” Communications, 2006 23rd Biennial Symposium.