隨著網路的進步與發展，許多新興的資訊服務，如影音資訊，在網路上傳輸時並未要求封包都送達，不同的封包有不同的重要性，例如 MPEG的關鍵畫面(I -Frame)就比其他畫面重要。常用的傳輸層通訊協定中，UDP與TCP都對所有的封包一視同仁，前者不做任何保證，而後者雖可保證所有封包的送達，但效率較差。 本研究提出一個新的TCP，”Partial-Reliable TCP”，使用選擇性重傳機制，配合應用程式的需求，對指定的封包提供遞送保護。當封包遺失時，只重傳保護的封包，可減少額外的網路資源消耗，並提升服務的品質。 此外，我們提出Single-Side的版本，接收端可以使用一般的 TCP，在封包傳送時，讓接收端以為封包都是無誤傳達的，在server-client架構的網路服務中，只有伺服器端必須使用我們的Partial-Reliable TCP，大幅提高本通訊協定的可行性。 最後我們利用網路模擬工具NS-2來模擬實際網路環境，將我們的方法與現行的通訊協定在可解畫面封包數、PSNR值及額外耗用的網路資源三個參數做比較。我們使用兩個 Video 影像作為傳輸標的，在高遺失率的有線與無線網路的環境中進行實驗。當傳輸時間限制很短時，（例如影像會議的應用），在有線的環境中， Basic PR-TCP比TCP Reno、TFRC最少增加約18%的可解畫面封包數，比UDP、TFRC及TCP Reno的PSNR值最少高出約15%，比TCP Reno及TFRC最少節省了12%的頻寬資源，Single-Side PR-TCP比Basic PR-TCP的PSNR值約低了11%，額外耗用的頻寬約多出10%。在無線的環境中，Basic PR-TCP比TCP Reno、TFRC最少增加約19%的可解畫面封包數，比UDP、TFRC及TCP Reno的PSNR值最少高出約20%，比Single-Side PR-TCP、TCP Reno及TFRC最少節省了15%的頻寬資源，Single-Side PR-TCP比Basic PR-TCP的PSNR值約低了14%。當傳輸時間限制較充裕時 (例如VoD應用)，Basic PR-TCP雖然比TCP Reno及TFRC降低了約3%的PSNR值，但是最少能節省8%的頻寬耗費，Single-Side PR-TCP的PSNR值跟Basic PR-TCP相近，但是額外耗用約5%的頻寬資源。 / With the advance of computer and communication networks, many new information services over IP-based networks such as video streaming and VoIP (Voice over IP) are growing rapidly. These services can tolerate some packets lost in transmission without too much damage to their quality. The content carried in the packets of these services is not equally important in their replay processes. For example, key frames (e.g. I-Frames) of a video encoded in MPEG format are more important than others. The loss of I-frames may have a large impact to the quality of the transmitted video, while the loss of other types of frames may only have nominal damage. Unfortunately, the two most popular transport protocols, UDP and TCP, treat all packets equally without any discrimination. TCP guarantees the delivery of all packets, while UDP doesn't. TCP may waste too much resource to guarantee the delivery of unimportant packets, while UDP may fail to deliver too many important packets. This thesis proposes a new TCP protocol, named Partial-Reliable TCP (PR-TCP), which applies selective retransmission strategy to provide delivery guarantee to the selected packets designated by the application programs. In this way, we can save bandwidth consumption and reduce the average delivery time without significant quality degradation. In fact, if the delivery of an object requires a stringent delivery time, the reduction of average delivery time may also lead to the reduction of abandoned packets at the receiver end. We propose two different versions of PR-TCP, Basic PR-TCP and Single-Side PR-TCP. Basic PR-TCP requires both ends of a connection to adopt PR-TCP while Single-Side PR-TCP only requires the sender end to adopt it. It is much easier to deploy Single-Side PR-TCP on the client-server systems where only servers need to use PR-TCP. Finally, we use NS-2 network simulator to evaluate our PR-TCP against TCP Reno, TFRC and UDP. Two video stream samples are used for video sources. Three quality parameters are evaluated: wasted bandwidth consumption, PSNR, and the number of packets in decodable frames. Under heavy loaded wired network and short delay bound (<0.8 sec.), the simulation shows that Basic PR-TCP can outperform TCP Reno and TFRC in the number of packets in decodable frames by at least 18%. It can outperform TCP Reno, TFRC, and UDP in PSNR by at least 12%. The performance of Single-Side PR-TCP is less then Basic PR-TCP in terms of PSNR by 10%, and it consumes larger bandwidth by 8%. Under wireless environments where error rate is high, the simulation shows that Basic PR-TCP can outperform TCP Reno and TFRC in the number of packets in decodable frames by at least 19% as well as wasted transmission overhead by at least 15%. It can also outperform TCP Reno, TFRC, and UDP in PSNR by at least 20%. The performance of Single-Side PR-TCP is less then Basic PR-TCP in terms of PSNR by 14%, and it consumes larger bandwidth by 10%. Under large delay bound (>8 sec.), the quality (PSNR) of the video transmitted using Basic PR-TCP is downgraded by only 3%, while it can save network bandwidth by 8%. The performance of Single-Side PR-TCP is about the same as Basic PR-TCP in terms of PSNR, but it consumes slightly larger bandwidth by 5%.

IEEE 802.16標準中有所謂Mobile Multi-hop Relay（MMR）的概念，然而基地台覆蓋範圍不足及遮蔽效應等問題尚待解決，因此在IEEE 802.16j標準中提出Relay Station（RS）以提升網路傳輸量並增進無線通訊品質。在MMR中由於多了中繼傳輸站來傳遞資料，因此需要有較多的連線頻道，此外也不能保證所有頻道都處於良好狀態，所以會有很高的機率造成資料傳送失敗。混和自動重傳要求（Hybrid Automatic Repeat reQuest, HARQ）的提出便是用來保證資料傳遞成功的機制。HARQ在IEEE 802.16-2004就已被提出，然而我們發現該HARQ機制在802.16j中是不具效率的，而且也並無法確保QoS（Quality of Service）的要求。在本論文中我們改善Chen[4]所提出的Dynamic Pre-allocation HARQ（DP-HARQ）機制，藉由考慮slot分配不足及封包發生非連續錯誤時造成延遲時間增加等問題，並加入具服務品質感知（QoS aware）的機制，以降低整體延遲時間（delay）並能有效提高吞吐量（throughput）。最後，我們以具二個hop以上的模擬環境，證明我們所提出的方法優於802.16j的HARQ機制及Chen[4]的方法。 / Mobile Multihop Relay (MMR) had already been defined in IEEE 802.16 network. The major purpose of MMR is to efficiently extend the coverage of a base station and to solve the shadow fading problem. The Relay Station (RS) defined in IEEE 802.16j is thus proposed to fulfill these goals. Because of the MMR Relay Station, we need more channels to transmit packets. However we cannot guarantee that all chaneels are in good condtion, there might be a high probability of failure transmission. The Hybrid Automatically Repeat reQuest (HARQ) mechanism is therefor proposed to ensure the successful transmission. The HARQ proposed in IEEE 802.16-2004 is not sufficient in 802.16j. Besides it can not help to meet QoS (Quality of Service) requirements. In this reserch we improve Chen’s [4] Dynamic Pre-allocation HARQ (DP-HARQ) mechanism by considering some problems like lack of slot allocation and packet transmission failure with non-continuous error, etc. We add the QoS aware mechanism to reduce the overall delay time and improve the throughput effectively. Finally, we simulate three hops environment and show that our method outperforms both the standard IEEE 802.16j the HARQ mechanism and Chen’s [4] method.

車載網路在未來社會將會越來越普及，車載網路資料傳遞技術，不僅能連接上網提供多元化的網路應用，甚至提供行車安全性服務。然而車載網路的網路品質不是十分理想，乃因存在著許多不確定因素，因為網路品質低，所以需要更完善的機制來提升車載網路品質。如車輛間速度不一，車輛間的距離變化相當頻繁，若因此而需要重新建立連線路徑是相當浪費傳輸時間並影響到傳輸的頻寛。本篇論文提出Cookie-Cooperative Automatic Repeat request (CCARQ) 的機制是針對這類型的間歇性斷線做修補，其方法是透過MAC (Media Access Control) 層協助網路層 (Network Layer) 的轉送。因為車輛是行駛在道路上，所建立的車載網路拓樸是沿著道路佈建，所以當連線路徑中斷時，周圍鄰近的車輛將是最好的替代選擇。本模擬將比較CCARQ, AODV與Bypass-AODV，透過 packet delivery ratio、end to end delay、control overhead及goodput為效能指標，調整在不同的hop數、車輛數目及車輛速度來觀察效能表現。模擬結果顯示packet delivery ratio增加14.6%、end to end delay減少41.3%、control overhead減少38%。 / VANET (Vehicular Ad-hoc Network) is expected to become more popular in the near future. VANET transmission technology will offer not only bountiful network applications but also safety driving information. Network quality of VANET is usually bad due to speed variation, high mobility, driver behavior variation, traffic density, traffic signal, environment complexity and swarm effect, et al. In this research, we propose a Cookie-Cooperative Automatic Repeat reQues (CCARQ) to enhance network performance by repairing intermittent broken connection. As mentioned above, speed variation will dynamically change the distances of car-to-car frequently and result in broken connections. Each re-establishment of broken connections will waste transmission time and reduce transmission bandwidth. The proposed CCARQ mechanism will help network layer transmission through MAC layer. Since VANET’s topology deployed along with road, the surrounded cars will be the best candidate to be a substitute car when a broken connection occurs. The performance indices are set to varied hops, varied speed and number of cars. Simulations show that CCARQ outperforms AODV and Bypass-AODV in packet delivery ratio by 14.6% increase, end to end delay by 41.3% decrease and control overhead by 38% decrease.

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.