Study On MAC Protocols For Broadband Passive Optical Networks

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...