在高度競爭下具軟性品質服務保證的802.11無線網路環境

Interference-Resisted and Soft Guaranteed QoS for Heavy Contention 802.11 Networks

雷喻翔(Yu-Hsiang Lei)

指導教授 ： 魏宏宇

國立臺灣大學/電機資訊學院/電機工程學研究所/碩士(2008年)

https://doi.org/10.6342/NTU.2008.02990

摘要

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。

關鍵字

無線網路 ； 服務品質保證 ； 競爭窗口

並列摘要

Nowadays, IEEE 802.11 based wireless devices are widely deployed. The new 802.11p
standard is an amendment of legacy 802.11 to provide wireless access in vehicular networking
environment. In this work, we propose an 802.11p compatible mechanism to
ensure guaranteed QoS for the vehicular applications. Vehicular wireless devices move
within their transmission range during a limited timeframe. Traffic alerting messages and
protocol signaling messages require guarantee QoS transmission within the limited time
duration. To transmit high priority data packets during these time-constraint transmission
opportunities, MAC level support is essential for opportunistic networking design in
vehicular wireless networks. In addition, current 802.11e QoS mechanism only provides
differentiated QoS but not guaranteed QoS. Under such contention-based 802.11 environment,
there are strong needs to provide assured delivery mechanism for opportunistic
access. Since hard guaranteed QoS in wireless random access networks is unlikely
achievable, we proposed a soft guaranteed QoS mechanism for 802.11 based systems. To
understand the benefit of our design, we use Markov chain model to evaluate this system.
We also use NS-2 simulations to validate the performance model. The performance
results show that the proposed scheme has better performance both on throughput and
successful transmission probability within a given time period.

並列關鍵字

wireless network ； quality of service ； contention window

參考文獻

[1] Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications,

IEEE Standard 802.11, 1999.

[2] Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications:

[3] Draft Amendment to Wireless LAN Medium Access Control (MAC) and Physical

Layer (PHY) seecifications: Enhancements for Higher Throughput, IEEE Standard