DBA Scheme In MAC Layer For Hybrid Access Network System Based On EPON And WiMAX

In order to meet the increasing high-speed demands of services, such as data, image and multimedia, broadband access technologies have been earning more and more concern. Currently, copper-based broadband access technologies (such as ADSL, VDSL, etc.) has reached its highest rate which it can provide. On one hand, with the fast developing of passive optical network (PON), which can provide huge bandwidth resource, fiber has been applied to access networks, providing Gigabit access bandwidth. On the other hand, wireless broadband access technologies (such as UWB, WiMAX,3G and B3G) became standard and commercial because of its advantages such as mobility and flexibility. However, the infrastructure of fiber access, which needs plenty of fiber lines, costs a lot; wireless access, on another side, which includes a great many of access points/base stations to connect to the core network through broadband fiber-optic network, need a high total initial investment. In order to combine resources and provide higher speed, more stable, more flexible broadband access services, wireless and optical networks tend to be integrated into the access network. Through the reconstructing and updating of EPON system, EPON technology can be used to backhaul wireless nodes, accumulating a variety of wireless services, so that the fiber lines can be used fully and widely in broadband wireless access system.This paper is limited to Ethernet-based Passive Optical Network (EPON) and WiMAX broadband wireless access system, focusing on the media access control (MAC) layer integration. Point to Multipoint (PMP) mode has been chosen for WiMAX system in the research. The base stations (BSs) in WiMAX are connected to the optical network user unit (ONU) in EPON via standard Ethernet interface. In the PMP mode, a BS serves all the user stations (SSs) within the scope of cell it covers. ONUs are connected to the optical link terminal (OLT) through PON network, then to Ethernet networks.This paper focuses on the uplink access control protocol in MAC-layer in the optical wireless converged network, specifically the dynamic bandwidth allocation scheme (DBA). In the scheme, the ONU and the BS can be considered as integrated logically, named ONU_BS node. This node will apply for bandwidth from OLT, and allocate bandwidth for SSs. The DBA algorithm are realized via the coordination of the bandwidth management modules located respectively in OLT, ONU_BS and SS node. Standard control messages, which are defined in specification, are applied to exchange bandwidth management information between nodes. At last, converged access network simulation model is built based on OPNET, which is a network simulation tool, to verify the DBA algorithm proposed in this paper. The simulation shows that this DBA scheme performs better in the overall system performance, such as average delay, throughput, channel utilization. This DBA scheme realized:(1) smooth data transmission throughout the converged access network; (2) end to end differentiated levels of services transmission for users to ensure QoS.