使用無線網路時常會遇到傳送訊號衰減、通訊死角或氣候不佳等原因，造成傳輸失敗。高畫質影像H.264/MPEG-4 編碼考慮影音封包具有不同重要性，對影音封包須制定不同的重傳機制。本研究改善WiMAX2中HARQ（Auto Repeat Request）的流程，將高畫質影像藉由TCP-Like方式傳輸影像，辨識影音封包資訊，確保GOP-Tree中＂骨幹＂節點的抵達率並利用Lagrange Method of Multiplier方法，對GOP-Tree中非骨幹節點提出合適的Trade-off。IEEE 802.16m標準支援Mobile Multi-hop Relay （MMR）的架構，針對目前基地台覆蓋範圍不足及遮蔽效應等問題提出中繼傳輸站(Relay Station，RS）來提升網路吞吐量並增進無線通訊品質。但也因此需要有較多的連線頻道及頻寬。然而此方式不能保證所有頻道都處於良好傳輸狀態，此而常有相當高的資料傳送失敗率。
混和自動重傳要求（Hybrid Automatic Repeat reQuest, HARQ）的提出就是用來確保資料傳遞成功的機制。HARQ早在IEEE 802.16-2004就被提出，然而我們發現HARQ機制在IEEE 802.16m效能不佳，更無法保證QoS (Quality of Service）的服務品質要求。在本研究中我們改善Chen [4]所提出的Dynamic Pre-allocation HARQ（DP-HARQ）機制，考慮當slot分配不足，封包在發生非連續錯誤時造成延遲時間增加等問題。我們所提出的方法加入具服務品質感知（QoS aware）的機制，來降低整體延遲時間（delay）並能有效提高吞吐量（throughput）。在模擬實驗中，我們以具二個hop，二個BS及十個SS以上的模擬環境，對不同方法做不同效能的評比，並以PSNR值檢驗所提出之方法是否能提升畫質，以確保影像傳輸品質。我們透過實驗數據證明提出的方法優於IEEE 802.16m的HARQ機制。 / This research focus on running high definition video over WiMAX2.It is usually that transmission fails through wireless network as it encounters factors like (transmission) signal attenuation, dead zone, bad weather, etc. The high definition video coding in H.264/MPEG-4 involves different degress of important video frames considering the video package. It defines different re-transmission mechanisms for video package. This research starts with the enhancement on the process of HARQ （Hybrid Auto Repeat Request）over WiMAX2, transmitting high definition video signals by“TCP-Like”protocol and indentifying the video package information to ensure a stable arrival rate of the “backbone” nodes in GOP-Tree. Furthermore, we apply Lagrange’s Method of Multiplier and propose an appropriate customization to the non-backbone part in GOP-Tree. Though the IEEE 802.16 standards has the concept of Mobile Multi-hop Relay（MMR）, yet there are problems to be resolved and improved when it comes to reality due to the facts like coverage deficiency of base stations and shadow effect. The IEEE 802.16m standard uses Relay Station (RS）to enhance network traffic throughput and improve QoS over wireless network.Relay transmission stations are set for data transmission in Mobile Multi-hop Relay (MMR),thus it requires more connection channels and bandwidth. The thesis concludes with performance comparison under the simulation environments of 2 hops, 2 BSs and 10 SSs, evaluation of the methodology with PSNR for enhancing the QoS of HD video transmission.The proposed method is proved to surpass the HARQ methodology in IEEE 802.16m.
| Identifer | oai:union.ndltd.org:CHENGCHI/G0096971017 |
| Creators | 王茂盈, Wang, Mao Yin |
| Publisher | 國立政治大學 |
| Source Sets | National Chengchi University Libraries |
| Language | 中文 |
| Detected Language | English |
| Type | text |
| Rights | Copyright © nccu library on behalf of the copyright holders |
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