IEEE 802.16e網路之語音串流性能分析

Performance analysis of voice streams over IEEE 802.16e

林俊宏(Jun- Hong Lin)

指導教授 ： 王居尉

亞洲大學/資訊學院/光電與通訊學系/碩士(2010年)

摘要

在本論文中我們探討語音串流於IEEE 802.16e網路的性能，當語音源處於靜音(Silence)的狀態下無封包產生，而當處於講話(Talkspurt)狀態時週期地產生封包，此一語音活動性偵測(Speech activity detection,SAD)機制可由一個二狀態的馬可夫鏈描述。在不違反現行已定的標準下，我們建議於上行鏈路generic MAC header中加入subheader，並利用Type欄位的位元0來定義管理許可次標頭來傳遞SS所需的上行頻寬請求。此外我們也建議使用Type欄位的位元1來定義裝包次標頭，用以將一 SS中多個語音連線所產生的較短封包多工成較長的封包而以一個上行封包傳送，如此可以大大的減少MAC的標頭耗損。在另外一方面因WiMAX在TDD 結構下的訊框架中下鏈及上鏈次訊框邊界是可動態調整，這特性極為適合具SAD的語音串流，我們比較了固定邊界及可動邊界的性能。在給定的系統參數下及封包漏失率不超過1%的情況下我們的結果顯示可動邊界可以比固定邊界多出兩個語音連線。

關鍵字

802.16e(WiMAX) ； 語音活動性偵測 (SAD) ； 網際網路電話 ； 封包遺漏機率

並列摘要

In this thesis we study the performance of voice streams over IEEE 802.16e networks. We assume the voice source employs a speech activity detection (SAD) mechanism so no packets are generated when the source stays in silence state and packets are periodically generated when it stays in talkspurt state. The SAD mechanism can be described by a two-state Markov chain. Without violating what have been standardized, we suggest to use extention subheaders in uplink generic MAC header of each MAC protocol data unit (MPDU). The Type Field bit 0 in the header is used as an indicator of the presence of grant management subheader which is used for the subscriber station (SS) to ask for uplink bandwidth. In addition, the Type field bit 1 is an indicator of the presence of packing subheader which is for multiplexing the shorter packets from individual voice into a longer packet. By this way, the MAC overhead can be significantly reduced. On the other hand, as the TDD frame structure allows for dynamical boundaries between downlink and uplink subframes, a feature extremely suitable for voice streams with SAD, we investigate the performance merit of using dynamical boundary for voice streams with SAD. For given system parameters and the constraint of packet dropping probability no more than 1%, our results show that the movable boundary scheme can achieve 2 more voice coonnections in comparison with the fixed boundary scheme.

並列關鍵字

802.16e (WiMAX) ； Speech activity detection (SAD) ； VoIP ； Packet dropping probability

參考文獻

[1] IEEE 802.16-2004,“IEEE standard for local and metropolitan area networks-part 16: air interface for fixed broadband wireless access systems,” Oct. 2004.

[3] D. Zhao and X. Shen, “Performance of packet voice transmission using IEEE 802.16 protocol,” IEEE Wireless Comm., pp. 44–51, Feb. 2007.

[4] H. Lee, T. Kwon, and D.-H. Cho, “An enhanced uplink scheduling algorithm based on voice activity for VoIP services in IEEE 802.16d/e,”IEEE Comm. Letters, vol. 9, no. 8, pp. 691693, Aug. 2005.

[5] C. Cicconetti, A. Erta, L. Lenzini, and E. Mingozzi, “Performance evaluation of the IEEE 802.16 MAC for QoS support,” IEE Trans. Mobile Computing, vol. 6, no. 1, pp. 26–38, Jan. 2007.

[6] H. Lee, T. Kwon, and D.-H. Cho, G. Lim, and Y. Chang, “Performance Analysis of Scheduling Algorithms for VoIP Services in IEEE 802.16e Systems,” IEEE VTC 2006-spring, pp. 1231–1235, 2006.