【作者】 曾清海；

【导师】 邱昆； 唐明光； 罗正华；

【作者基本信息】 电子科技大学 ， 光学工程， 2000， 博士

【摘要】 对高速Internet的接入和多媒体应用的需求，极大地促进了宽带接入网络的发展。作为宽带接入网络的一个重要研究领域，APON把ATM的统计复用功能和PON的宽带透明传输结合起来，以便在为用户提供宽带接入的同时，支持不同业务的服务质量（QoS）要求。APON具有容量大、性价比合理和易于升级等优点。 然而，由于APON采用的是树型结构，且上下行速率很高，所以APON存在测距、上行突发光接收、上行突发同步和带宽动态分配等技术和理论难题。本文将主要针对APON系统的带宽动态分配、上行突发同步和OLT TC层关键功能的设计进行研究。 首先，在本文的绪论部分，我们对现代通信网络和宽带接入网的发展趋势进行了综述，指出研究APON的必要性和现实意义。 第二章介绍了APON系统的结构和要求，并对APON系统的三大功能块进行了较为详细的阐述，最后描述了APON需要解决的关键技术。 在第三章中，我们在John D．Angelopoulos等人提出的顶移分配算法和传送带分配算法的基础上，提出了一种适合于APON的MAC协议。该协议将业务按实时性要求分成两种优先级，实时业务具有更高的优先级，在动态带宽分配时优先分配。实时业务带宽分配使用的传送带分配算法与John D．Angelopoulos等人提出的略有不同。非实时业务采用顶移分配算法进行授权分配。非实时业务通常对时延性能不敏感，而对信元丢失率要求苛刻。顶移分配算法给有较多等待信元的ONU更多的传输机会，因此在一定的缓冲容量下我们的协议能够降低ONU中非实时业务的信元丢失率。同时，我们首次对APON系统上行接入进行了理论分析，并得到了一些初步结果。在本章的最后，对该MAC协议的性能进行了仿真。仿真结果表明，该MAC协议具有很好的接入性能。 在第四章中，我们在Stephen Topliss等人提出的相关同步法基础上，根据APON系统上行信息高速、突发的特点，提出了实现APON系统上行突发同步的方法——相关同步法。在接收端，我们采用延迟线技术获得八个相 扬 要位依次相差45“的时钟。这八个时钟分别对接收信号进行采样读取，得到八组输入信号。八组输入信号被分别送入八个8位移位寄存器。八个移位寄存器的值分别与己知的同步码进行相关比较。同步码具有很好的自相关性。当上行突发块中的同步码到达时，将有一组甚至多组输入信号的相关结果达到最大值1。根据相关原理，取得最大相关结果的那组（或中间那组）输入信号为最佳采样信号，对应的采样时钟为最佳采样时钟。最佳采样时钟的确定，实际上就知道了上行突发信号的到达相位，从而实现了突发同步。用最佳采用时钟来恢复接收信号，就实现了同步接收。 相关同步法的最大优点是它的全数字同步方式，易于FPGA实现。我们采用相关同步法实现T 155．52Mbit／S速率的突发同步。这一成功为 APON的开发扫清了一个关键障碍。 第五章对 OLT TC层功能进行了详细的分析。实现 OLT TC层功能是APON系统开发的难点。我们在准确理解 G．983协议的基础上得出了 OLT TC层关键功能模块的工作流程框图。关键功能工作流程的获得使这些功能的实现变得更加简单。 最后，在第六章中，我们对本文的工作和所得到的结论进行了总结。更多还原

【Abstract】 The demand for accessing Internet with high speed and supporting multi-media applications has greatly accelerated the development of broadband access networks. As one of the major researching areas of broadband access networks, the passive optical networks based on ATM (APON) combine the ATM’s statistic multiplexing function with PON’s broadband transparent transmission, so as to support different Quality of Service (QoS) as well as broadband access. APON have a lot of virtues, such as big capacity, reasonable ratio of performance and price, and easy to upgrade. However, since APON has a tree-based topology and the rates in both way are high, there are some technical or theoretical problems, such as ranging, burst mode optical receipt, burst synchronization and dynamic bandwidth allocation. The dissertation will mainly concentrate on the study of dynamic bandwidth allocation, upstream burst synchronization and the key functions in OLT抯 TC layer. Firstly, in the introduction of this dissertation (chapter 1 ),we briefly present the researching and developing status of modem telecom networks and broadband access networks, and indicate the importance of developing APON. In chapter 2, we introduce the configuration and requirement of APON systems at first, then we expatiate on the three functional blocks in detail. Finally, we describe what the key technologies are for APON. In chapter 3, based on the "moving ceiling" allocating scheme and "transfer belt" allocating scheme proposed by John D. Angelopoulos et al, a MAC protocol suitable for APON is proposed. The services are classed as two priorities according to different delay requirement in the protocol. The real-time services have a higher priority, and can be permitted first. Non real-time services are not sensitive to delay, but sensitive to cell loss ratio (CLR). "moving ceiling" allocating scheme gives the ONU, in which there are more cells waiting, more chance to send, so this protocol can debase the CLR of non real-time services when the buffers are definite in the ONU. For the first time, the APON’s upstream access process is analyzed in this thesis, and some primary results are met. In the chapter’s end, the performances of the proposed MAC protocol are simulated. The simulations?results show that the protocol has good access performances. In chapter 4, based on correlating synchronization scheme proposed by Stephen Topliss et al, a synchronization scheme suitable for APON’s upstream burst synchronization is proposed according to the high-speed and burst-mode characteristics of APON’s upstream information. Delay line technique is used to get eight clocks in the receiver. The phase difference among the eight clvcks is 45 degrees. The eight clocks sample the receiving signal, and get eight inputting data. a The eight inputting data are sent to eight 8-bits registers respectively. The registers? values are compared with a known key word, which has a good self-correlation. When the key word in the burst packet arrive, there must be one ,or even several results are maximal. According to correlation principle, the inputting data with maximal result is the best sampling data, and the corresponding clock is the best sampling clock. Using correlation synchronization scheme, we carry out a burst- mode synchronization with a rate of 155.52OMbit]s. This fruit sweep away a key obstacle in APON’s exploitation. In chapter 5, the functions of TC layer in OLT are analyzed in更多还原