於WiMAX系統下VoIP之效能分析

現今社會最熱門之無線寬頻存取的新標準IEEE802.16，具有高頻寬、支援移動性等特點。但對於BS在有限的頻寬下，如何滿足眾多使用者的要求，是個值得分析的問題。本篇論文以更貼近實際網路運作的狀況為目標，在NS2平台上模擬接近實際PMP的WiMAX網路。並且去探討在有其多個使用者共享頻寬的條件下，對於特定的網路應用服務，如何能才能達到系統最大容量(capacity)的使用率。本論文將網路系統分為兩個部份建置，分別為模擬同時有其他使用者(SS)在同個基站(BS)下，佔用部份頻寬資源的Background APP，與我們欲測試系統容量對於使用特殊應用服務的使用者Tracing APP支援程度。透過五種不同的佇列管理來進行模擬，分別是Drop Tail、RED、DRR、FQ、SFQ來比較隨著使用者的增加分析網路資源競爭狀況以及即時語音傳輸的效能。VoIP的應用中，我們比較了data rate 分別為64kbps和8kbps 的兩種Codec：G.711及G729，最後模擬將Video與VOIP應用結合使模擬更貼近實際網路情況。本篇論文建立了１條data rate為160Kbps的CBR傳輸，用以做為模擬background的網路傳輸行為。模擬所使用的參數設定如下，傳遞延遲時間參數為1 ms、鍊路具有的頻寬為1Mbps、調變為OFDM_QPSK_3_4，Routing protocol為DSDV，其他沒有定義的參數都使用預設值，預設值都存放在ns-default.tcl.檔案裡。評估通話品質的標準設delay為150 ms、loss rate為3%。模擬結果G.711可以達到系統最大容量為同時21名的使用者上線。由於Codec G.729每次傳送的封包大小相對於Codec G.711來的小，可以達到系統最大容量45名使用者上線。最後將Video與VOIP應用結合可以達到系統最大容量為7名使用者上線。

關鍵字

NS-2 ； IEEE802.16 ； WiMAX ； QoS

並列摘要

Nowadays, a new standard IEEE802.16 has become the most popular wireless broadband access technology which has the merit of high bandwidth and mobility. Since the bandwidth of BS is limited, it deserves to do analysis to sacrifice the request of numerous users .Based on the goal of making the simulation corresponding with the actual network operation situation, this research executes the simulation on the platform of NS2 to simulate WiMAX network which is very close to the actual PMP and discuss how to achieve the usage rate of the maximum system capacity for specific web application service on the condition of multiple users sharing the bandwidth. The network system is divided into two parts; one is for simulating Background APP under the circumstances that another user in the same BS occupying the partial bandwidth and the other one is to simulate the level of the system capacity we intent to test supporting Tracing APP (user) for the use of special application service. Five different kinds of queue management are used to do simulation respectively, they are Drop Tail、RED、DRR、FQ and SFQ to analyze and compare the competition situation of the network resource and the efficiency of real-time voice transmission with the increasing of users. In the application of VoIP, two kinds of Codes G.711 and G729 which their data rate are 64kbps and 8kbps respectively are compared. Video and VOIP are combined to make the simulation more closer to the actual network situation. This research establishes a CBR transmission with 160 Kbps data rate to serve as the background for simulation. Parameters in this simulation are as follows: 1ms transmission delay time, 1Mbps bandwidth, OFDM_QPSK_3_4 modulation and DSDV Routing protocol, other parameters that are not defined are used with default values which are put in the ns-default.tcl file. The standard of assessing the communication quality sets the delay time as 150ms and the loss rate as 3%. The result of simulation from this research shows that Codec G.711 can achieve the maximum system capacity with around 21 users getting online simultaneously. Since the amount of packet Codec G.729 transfer each time are smaller, comparing to Codec G.711, it can achieve the maximum system capacity with around 45 users getting online simultaneously.. Finally, the combination of Video and VOIP can achieve the maximum system capacity with 7 users getting online.

並列關鍵字

NS-2 ； IEEE802.16 ； WiMAX ； QoS

參考文獻

[1] IEEE Standard 802.16Tm-2004: Air Interface for Fixed and Mobile Broadband Wireless Access Systems. IEEE, 2004.

[2] IEEE Standard 802. 16e'M-2005: Air Interface for Fixed and Mobile Wireless Access Systems. IEEE, 2006.

[7] ITU-T Rec. H.323 version 4, “Packet-Based Multimedia Communications Systems,” ITU, Nov. 2000.

[12] ITU-T Rec. P.862, ”Perceptual Evaluation of Speech Quality (PESQ), an Objective Method for End-to-end Speech Quality Assessment of Narrowband Telephone Networks and Speech Codecs,” Feb. 2001.

[14] N. O. Johannesson, “The ETSI Computation Model: A Tool for Transmission Planning of Telephone Networks”, IEEE Communications Magazine, vol. 35, issue 1, Jan. 1997, pp. 70-79.

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於WiMAX系統下VoIP之效能分析

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