隨著科技日新月異，寬頻無線網路環境快速的發展，由有線與無線建構起的網路架構也愈發成熟，異質性網路將扮演著極重要的角色，最近更有廣範圍的都會區域無線網路(Wireless MAN)802.16，使得無線網路頻寬都已經有足夠的能力能夠乘載多媒體串流的資料流量，因此使用無線網路環境之多媒體串流應用勢必是未來的趨勢。視訊與聲音串流的應用在業界一直受到重視，這些多媒體串流的應用包括網路語音、視訊會議與遠距教學以及隨選視訊。此外，隨著現今異質性網路的發展，許多使用端的設備皆有多個無線或有線網路卡支援，於是學者們針對如何同時使用多個網卡同時建立的連線來做傳輸的動作，增加傳輸連結的可靠性以及傳輸流量的增加，造就了新一代的傳輸協定SCTP，支援 multi-homing 的特徵。然而，根據之前的研究與我們的實驗，現今具有壅塞控制處理的傳輸層協定，無論是適用於資料傳輸的TCP, SCTP 或是適用於多媒體傳輸的TFRC 皆沒有考慮到無線網路的特性。在無線連結比起有線而言是非常不可靠的，任何時間可能會遺失封包且遺失率較高，而現有的TCP 實作都假設封包遺失或逾時是因為壅塞引起的，因而調降傳送的速率，事實上，當封包遺失在有線網路上，傳送端應該要減速；而是遺失在無線網路上，則不應該降低傳送率。如果能讓傳送端分別出封包在何種網路類型中遺失的，必定能改善TCP, TFRC 及SCTP 在無線環境中效能不好的問題。此研究計畫中，我們將提出一個新的方法，利用封包遺失與延遲變異判斷網路連結是否壅塞，基於此方法的提出，將可以滿足無線寬頻網路中傳輸層的基本需求，有效的改善壅塞處理及流量控制的不足，此外我們將設計各種不同的拓樸來驗證我們的理論正確性，包含在與其他TCP 流量並存時所需的友善度及公平性的測試，經由ns2 及相對的分析模組來做驗證，進而最佳化整體頻寬使用率及效能。此計畫將如下面的內容進行︰(1)第1 年︰針對延遲變異的相關理論，開發新的TCP 壅塞處理機制,運用在現今無線網路的資料傳輸部分 (2)第2 年：延伸此延遲變異機制，運用在適用於多媒體傳輸的傳輸層協定TFRC 上 (3)第3 年：SCTP 的multi-homing 特性為未來異質性網路的重點，進而利用延遲變異機制來增進此通訊協定的效能。 As wireless broadband network is growing rapidly, the wired/wireless mixed inter-network, a heterogeneous environment with a great deal of maturity will get wide deployment in the next generation ALL-IP wireless networks. Currently many places support wireless network which may be 802.11 and 802.16, they make wireless network more and more popular. And these wireless networks are capable of multimedia streaming. Multimedia streaming over wireless network will dominate the market in the future. Rate Control plays an key role for many multimedia services such as streaming applications. video/audio streaming applications play an important role in business. They contain VoIP, video conference , distant learning and video on demand. With the advancement of heterogeneous network, especially the wireless technology, a host may be equipped with multiple wired or wireless interfaces. Scholars considered concurrent transmission using multiple path between multi-homing communication hosts in order to improve connection reliability and increase total throughput. So the standard of SCTP which support multi-homing feature is accomplished. However, current transport layer protocols which have congestion control mechanism such as TCP, SCTP and TFRC which detects the losses as congestion events could not suit the heterogeneous network in which the losses will be introduced by higher bit error rates or handoffs. There exist some unsolved challenges for applying TCP, SCTP and TFRC over wireless links. End-to-end congestion control and fairness issues are two significant factors. To satisfy these two criteria, we propose a jitter-based scheme to adapt sending rates by the packet losses and jitter ratios. It can satisfy the end-to-end requirements to improve current congestion and flow control. Furthermore, we will design different kinds of topologies to validate our proposed scheme is correct, including TCP friendly and fairness through the ns2 simulation and analytical results. And then optimize the bandwidth utilization and performance. The project will be proceed as the following: (1) Year 1: Jitter-based TCP Design for Wireless IP Traffic (2) Year 2: Jitter-based TFRC Design for Wireless Multimedia over IP (3) Year 3: Jitter-based SCTP for Wireless Streaming Applications. 研究期間：9608 ~ 9707
