The Simulation Of Passive Optical Network System And Research Of Its Dynamic Bandwidth Allocation Algorithm

Passive Optical Network (PON) has been one of the main solutions for optical access network, and has the advantages of low cost, high reliability and simple maintance. As users demand for broadband services is growing, the current EPON (Ethernet PON) and GPON (Gigabit PON) are difficult to meet the needs of long-term development, so the next-generation passive optical network technologies have become a research hotspot at home and abroad.This thesis systematically studied the architectures of next-generation PON systems and their media access control (MAC) protocols from the aspects of high bandwidth, long transmission distance, large capacity and local area networking;in addition, the related dynamic bandwidth allocation (DBA) algorithms were simulated and analyzed. The main results were as follows:(1) For varieties of tree-based passive optical network, a general method for network modeling and algorithm simulation was proposed. By using Opnet Modeler simulation software, the node-level models of optical line terminal (OLT), optical network unit (ONU), traffic source and others were realized, and then a PON simulation platform was built, which laid a foundation for the further research of bandwidth allocation algorithm in PON systems.(2) For wavelength division multiplexed passive optical network (WDM-PON), an efficient bandwidth allocation strategy was proposed. The online algorithm was realized and tested with three bandwidth allocation strategies which were fixed service, limited service and gated service respectively. The results show that the open service strategy can effectively reduce the data delay.(3) For long-reach PON (LR-PON), a pipelined cyclic dynamic bandwidth allocation algorithm was proposed, which not only reduces the packet end-to-end delay by eliminating scheduling gaps between the cycles, but also provides better supports for different grades of traffic, especially for the real-time voice service.(4) For subcarrier multiplexed passive optical network supporting local area networking, a distributed multipoint access protocol and DBA algorithm were proposed. Under the proposed algorithm, ONUs communicated with each other by the help of 3×N coupler or Fiber Bragg Grating (FBG) at remote node which reflects the up-transmission optical signals. The process of bandwidth allocation was completed coordinately by the ONLUs without the intervention of OLT, which effectively reduces the control plane delay. In addition, LAN traffic and upstream traffic were separated form each other at ONUs and transmitted synchronously in RF (Radio Frequency) and baseband signals respectively, which increases the available bandwidth of up-link and down-link channel.(5) For hybrid WDM/TDM-PON based on periodical waveguide array grating (AWG), the conceptions of physical sub-PON and logical sub-PON were presented; and for logical sub-PON, two kinds of DBA algorithms adopting earliest available time scheduling mechanism were proposed, which effectively avoids the resources competition and achieves bidirection transmissions between OLT and ONU.