魏宏宇Wei, Hung-Yu臺灣大學:電機工程學研究所雷喻翔Lei, Yu-HsiangYu-HsiangLei2010-07-012018-07-062010-07-012018-07-062008U0001-2907200823563200http://ntur.lib.ntu.edu.tw//handle/246246/187976以802.11為標準的無線網路設備目前被廣為使用。目前最新的802.11p是基於802.11的修正，目的在於提供車用網路環境下無線網路的使用。在這篇論文中，我們提出了一個802.11p相容的機制用以在車用網路的應用下提供服務品質的保證。交通警示訊息和協定的信令通常在一個有限的時刻內需要服務品質的保證。為了在這種有時效性的傳輸方式傳送高優先權的資料封包，媒體存取控制層對於此種車用無線網路的環境尤為重要。此外，目前的802.11e服務品質的保證機制只由提供差異性的服務品質，並沒有提供服務品質的保證。802.11競爭式的網路環境更需要提供確切的傳送機制。我們知道在隨機存取的無線網路環境下，要提供硬式的服務品質的保證是不切實際的，因此，我們針對802.11的無線網路提出一種軟式服務品質的保證。為了進一步了解我們所設計的方法的優點，我們採用馬可夫鏈分析所提出的架構，並且用網路模擬程式NS-2來驗證所分析的結果。無論是從數學分析或是程式模擬的結果都顯示，在我們所提出的架構下，系統的確會有比較高的吞吐量和傳送成功的機會。Nowadays, IEEE 802.11 based wireless devices are widely deployed. The new 802.11ptandard is an amendment of legacy 802.11 to provide wireless access in vehicular networkingnvironment. In this work, we propose an 802.11p compatible mechanism tonsure guaranteed QoS for the vehicular applications. Vehicular wireless devices moveithin their transmission range during a limited timeframe. Traffic alerting messages androtocol signaling messages require guarantee QoS transmission within the limited timeuration. To transmit high priority data packets during these time-constraint transmissionpportunities, MAC level support is essential for opportunistic networking design inehicular wireless networks. In addition, current 802.11e QoS mechanism only providesifferentiated QoS but not guaranteed QoS. Under such contention-based 802.11 environment,here are strong needs to provide assured delivery mechanism for opportunisticccess. Since hard guaranteed QoS in wireless random access networks is unlikelychievable, we proposed a soft guaranteed QoS mechanism for 802.11 based systems. Tonderstand the benefit of our design, we use Markov chain model to evaluate this system.e also use NS-2 simulations to validate the performance model. The performanceesults show that the proposed scheme has better performance both on throughput anduccessful transmission probability within a given time period.bstract. . . . . . . . . . . . . . . . . . . . . . .iiiist of Figures. . . . . . . . . . . . . . . . . . . vist of Tables. . . . . . . . . . . . . . . . . . . .vii Introduction 1.1 Multimedia Delivery in 802.11 . . . . . . . . . . . . . . . . . . . . . . . 1.2 Challenges in 802.11 QoS . . . . . . . . . . . . . . . . . . . . . . . . . 2.3 Vehicular Networking with 802.11p . . . . . . . . . . . . . . . . . . . . 4.4 Contributions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5.5 Related Work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 System Design and Analytical Model 7.1 System Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7.2 Contention and Collision Probabilities . . . . . . . . . . . . . . . . . . . 17.3 Throughput . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22.4 Successful Transmission Probability During a Period . . . . . . . . . . . 27 Model Validation and Numerical Results 31.1 Model Validation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31.1.1 Throughput . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32.1.2 Successful Transmission Probability During a Time Period . . . . 33.2 Numerical Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35.2.1 Contention Probability . . . . . . . . . . . . . . . . . . . . . . . 35.2.2 Effect of Initial Contention Window Size (CWmin) . . . . . . . . 36.2.3 Soft QoS Guarantee . . . . . . . . . . . . . . . . . . . . . . . . 38 Discussion 40.1 Implementation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40.2 Fairness . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40.3 Integration with 802.11e and 802.11n . . . . . . . . . . . . . . . . . . . 41.4 Opportunistic Transmission in Vehicular Networks . . . . . . . . . . . . 42 Conclusion 43ibliography 46645101 bytesapplication/pdfen-US無線網路服務品質保證競爭窗口wireless networkquality of servicecontention windowthesishttp://ntur.lib.ntu.edu.tw/bitstream/246246/187976/1/ntu-97-R95921099-1.pdf