互動式有線電視網路中混和式光纖同軸電纜的多重存取協定

Abstract

因著ATM網路提供國家資訊基礎建設(NII)的主幹線路，已然成熟的有線電 視網路可望能 扮演著將NII深入家庭的媒介角色。然而，要提供這些一 般住戶的使用，有線電視的區域 網路架構必須重新設計使之有具備雙向 的互動傳輸能力。 在本篇論文中，我們提 出一個適用於混和式光纖同軸電纜線的上層傳輸協定*PCUP.這個 PCUP是 應用管線模態於上行頻道中。這可以藉由兩種方式來達成:第一、用戶端 定位，也 就胝測量用戶端和頭端的傳輸位移值:第二、傳輸排程，也就是 在同一個回圈中給予每 個用戶端傳輸開始時間和傳輸時間長度。藉由 計算傳輸開始時間和傳輸時間長度，這使 得他們的傳送結果就宛如兩兩 相連的管線模態一般。另外，以競爭模態的樹狀結構演算 法，將間隔的 被執行，用以調整上線的用護端數目，也就是所謂的成員控制機制。 在論文的最後，我們由模擬的結果來估計它的有效性，包含：資料遺失率 、傳輸量、資 料延遲時間、設定延遲時間及資料佇列時間。同時我們也 對CSMA/CD和R-ALOHA做模擬並 與之比較。 While ATM (Asynchronous Transfer Mode) serves as the backbone of our NII (National Information Infrastructure), the prevailing cable TV networks may serve as the NII community networks that span the infrastructure into the homes. However, in order to support these services to the residential users, the community cable TV networks have to be redesigned to support 2-way interactive communication. In this work, we propose PCUP (Pipelined Cyclic Upstream Protocol) as the upstream MAC (Medium Access Control) protocol for HFC (Hybrid Fiber Coax) community access network. PCUP is designed with the intention of pipelining the upstream channel. This is achieved by proper station positioning, which measures the station propagation offset from the headend, and transmission scheduling, which assigns each station the transmission starting time and duration in a cycle. By taking into account the propagation offsets and the transmission times, transmitted cells can appear back-to-back, i.e. pipelined, at the headend. Since only the active stations are scheduled to transmit in a cycle, a membership control mechanism, which runs a contention-based tree walk algorithm, is executed periodically to allow the stations to join or leave. We evaluate the behavior of our protocol through simulations to show the effectiveness with respect to loss ratio, throughput, delay, and setup latency. Comparisons with R-ALOHA (Reservation Slotted ALOHA) and CSMA/CD are also made. The results confirm PCUP's excellent performance.