【作者】 池灏；

【导师】 陈抗生； 章献民；

【作者基本信息】 浙江大学 ， 电子科学与技术， 2001， 博士

【摘要】 目前多种宽带接入技术可供选择，从xDSL到HFC等。但是从长远来讲，它们只是过渡性方案。在有线接入领域，由于光纤的带宽优势，无源光网络（PON）技术有着良好的市场前景。尤其是基于ATM的无源光网络（ATM-PON或称APON）被誉为面向二十一世纪的宽带接入解决方案，它结合了ATM的多业务、多比特率支持能力和无源光网络的带宽、成本优势。 本文的工作集中于宽带无源光网络系统介质访问控制（MAC）协议的研究和设计、协议性能分析以及其他与MAC协议相关内容的研究。 首先讨论了IP与ATM之争，并研究了APON上传递IP包的可能方式。作为介质共享的树形网络，APON需要介质访问控制协议（MAC）协调各终端对上行信道的访问，避免冲突。MAC协议在整个通信系统中扮演着重要的角色，对系统的性能有着深刻的影响，在APON中居于核心地位。ITU-TG.983建议的推出使APON的发展走上了标准化之路，但它并未对MAC协议作出明确规定，并指明尚需进一步研究，因此本文的工作具有现实意义。 与其他介质共享网络相比，APON的树性结构具有特殊性，这对MAC协议提出了特殊要求。随机接入控制方法虽然具有简单和易于扩展的特点，但是无法满足电信级的时延和吞吐量要求，因而不适用于APON系统。中央控制基于预约的带宽分配算法是APON的首选，它具有良好的时延和吞吐量特性。作为整个ATM网络的一部分，APON必须能与ATM网络的流量监控措施保持协调一致，其要求是尽量降低信元流的时延抖动。各类协议都有各自的带宽分配和抖动控制策略。本文给出分段均匀间隔MAC协议，均匀间隔和分段分配带宽的策略可以使协议自动地随负载状况变化而调整，既很好地控制了抖动，又提高了带宽效率。排队理论和计算机仿真是研究通信系统性能的重要手段，本文对几类典型协议作了成功的分析和研究，分析结果也表明了分段均匀间隔协议的有效性。 SuperPON是APON的扩展，它支持更多的用户，覆盖更广的范围并提供更高的比特率。由于其多用户和大时延的特点，APON的MAC协议并不适用于SuperPON。作者设计的协议中，根据不同时延要求，提供半静态和动态的带宽分配方法，满足不同业务的需求。动态带宽分配算法自适应于系统的负载状况，最大限度改善了非实时业务的性能。 最后还探讨了PON的发展趋势，以及将WDM技术引入PON的几种可行方案。 本文的主要贡献可简单归纳为： 1．采用理论分析和计算机仿真的手段对各类MAC协议（包括作者为APON设计的分段均匀间隔MAC协议和和为SuperPON设计的分优先级自适应MAC协议）及其确定的网络性能进行了较为系统的研究； 2．在综合分析各类带宽分配算法的基础上，首次提出了一套符合ITU-T规范的APON系统MAC协议一分段均匀间隔MAC协议，均匀间隔和分段分配带宽的策略既能很好地控制抖动，又提高了带宽。并对该协议的性能进行了计算机仿真分析，结果表明在总负载为0.8的情况下,CBR流的时延值和抖动值分别被控制在1ms和0.36ms以内(在10^-5分位点上)；浙江大学搏士学位论文 3．针对SaperPON系统多用户、大时延的特点，完整地提出了一套S呷rPON 的MAC协议一分优先级自适应MAC协议，不同优先级满足不同的业务 需求，对于实时业务采用无须预约的半静态带宽分配法，而非实时业务的 申请微时隙接入自适应于系统的负载状况，在固定分配和随机接入间动态 切换，兼顾了系统吞吐量和时延特性的要求。计算机仿真结果表明，当系 统负载为0石时，实时业务的接入时延和时延抖动几乎可以忽略以0．lins＼ 而非实时业务的时延和抖动亦基本上被控制在2．sins和1．4ms以内。更多还原

【Abstract】 At present, several alternatives are considered for the provision of broadband services in the local loop, from xDSL to HFC. However, they are all expediencies, to some degree, from a long-term viewpoint. In the field of wired solutions, passive optical networks (PON) look very promising due to their bandwidth capacity. Especially, ATM based PON (ATM-PON or APON) has been so called the broadband access solution of the 21st century. It integrates the advantages of multi-service and multi-bit rate capabilities of ATM and high bandwidth and low cost of PON.This dissertation focuses on study and design of medium access control (MAC) protocol for passive optical network, protocol performance evaluation, and other aspects closely correlated to MAC protocol.Firstly the author discussed the competition between IP and ATM, and possible modes for IP packet over APON. As media-shared network, APON needs some form of Media Access Control (MAC) protocol to arbitrate the upstream channel among terminations, and avoid collisions. The MAC protocol plays an important role in the whole communication system, and affects performance of the system with great significance. So it’s the kernel in APON access system. ITU-T G.983 recommendation accelerates the process of standardization of APON, but it does not determine MAC protocol and declares that it needs further studies. It’s still an open problem, so our work has practical meaning.Compared with other media-shared network, APON’s tree-like topology has its own characteristics that impose particular requirements on MAC protocol. The method of random access is rather simple and easy to expand, but it cannot satisfy the rigorous delay and throughput requirements of telecommunication network. So it is not available for APON. Centrally controlled reservation-based bandwidth allocation algorithm is the first choice for APON, because it ensures better delay and throughput. As a part of whole ATM network, APON should be in concert with the traffic control policies of ATM. For this, the MAC protocol should minimize the cell jitter over passed stream with effort in the access phase. All MAC protocols characterize themselves by the method of dynamic bandwidth distribution and cell delay variation control. In our protocol, uniform spacing and segmentation polices make algorithm adjust with the change of loading situation dynamically, which suppresses cell jitter pretty well and also improves the bandwidth efficiency. Queuing theory and computer simulation are two important tools to evaluate the performance of the communication system. Based on them the author analyzed some typical protocols successfully, and also approved the segmented uniform spacing MAC protocol by computer simulations as well.SuperPON is a natural upgrade of APON, which can support more users, covers wider range and provides higher bit rate. Due to its high-splitting and high-delay, MAC protocols for APON are not available for SuperPON. The protocol the author designed for SuperPON, provides half-static and demand dynamic access control method according to different delay requirements. Reservation based dynamic bandwidth allocation scheme still adopts the concept of uniform spacing, and the access of requestslot adapts to loading situation, which improves the non-real time services. Computer simulations justify the protocol with satisfactory results.Lastly, the developing directions of PON are discussed, as well as two possible schemes to incorporate WDM technologies into PON.The main contributions of this dissertation can be briefly summarized as follows:1. Different type of MAC protocols and the network performance determined by MAC protocols were studied by theoretical analysis and computer simulation in a systematical way;2. A novel MAC protocol-segmented uniform spacing MAC protocol, which complies with ITU-T recommendation, was firstly designed for APON system based on the analysis of different type of bandwidth allocation algorithms. Its uniform spacing and segmented bandwi更多还原