| This paper is worked out based on the research work of National 863 Hi-tech project: "Giga Bit Ethernet Based Passive Optical Network" (No.2001AA122022). The research work of this project is oriented to the practicable EPON system design. This paper studies the several key issues of media access control (MAC) layer of EPON, including MAC control sub-layer and RS sub-layer. The main contributions of this paper are:(1)It puts forward a solution realizing P2PE and SE based on the LLID bridge .An emulation (reflecting) function is added into OLT' MAC layer, and the OLT will learn both MAC address and LLID of user equipment, to build a LLID?MAC table, and forward or reflect frames based on LLID. (2)It brings forward a layered architecture for uplink bandwidth allocation function of OLT. A hardware supporting layer is designed, including a tail coordinate bandwidth table and a bandwidth distribution module. This layered architecture separates the DBA algorithms from the functions for recording and granting the uplink bandwidth. Use such layered model and design, OLT can support multiple kinds of DBA algorithm, and can support multi kind of DBA algorithms, which make the system can satisfy the requirements of different situation or service.(3)A new bandwidth priority partition based upstream bandwidth allocation policy is presented to support multi-services, such as the TDM and data services.So, this paper can be summarized into four aspects:(1)ONU auto discovery and register contention solution. It puts forward a design scheme of ONU auto discovery and register. It compares two register contention solutions, "skip random number of discovery window" scheme and "random delay within the discovery window" scheme, using theoretical and experimental analysis, and chooses the second scheme according to the analytic results. (2)Upstream data collision avoidance. In order to improve the uplink bandwidth utility, that is, keeping the guard band between conterminous ONU slots as short as possible, as well as avoiding the upstream data collision, OLT must take the RTT of ONU into account, when arranges the start and ending time of ONU's transmission window. Meanwhile, ONU must transmit upstream data strictly under the OLT's grants. The technologies for that include time stamp ranging and uplink transmission window control. It puts forward an Ethernet frame based design of time stamp ranging and RTT compensate, as well as the uplink transmission window control. (3)EPON compliance。It puts forward a solution of compatibility between EPON equipments and current Ethernet equipments. The compatibility is achieved by using the reflecting function on MAC layer of OLT and the filtering function on RS sub-layer of ONU, making the P2MP EPON emulate P2P or shared LAN. In the presented solution, the OLT can be regarded as a LLID (logic link ID) bridge which has two ports at least. One port provides standard Ethernet connection to bridge or switch of Internet. And the other port connects with the PON. At that port, it is no longer MAC address but LLID of ONU, on which the user packets (excluding control frames) are forwarded or filtered. Similarly, ONU connects the user stations or networks to the PON. On the UNI side, if ONU is connected with multiple user equipments or networks, ONU must do as a normal Ethernet switch or bridge, or ONU must connect to an Ethernet switch or bridge. While on the PON side, ONU filters received packets based on its LLID. It not only resolves the compatibility with existing IEEE 802.1D compliant bridges, but also gets efficient downstream broadcast utilization.(4)From the uplink bandwidth allocation point of view, this paper brings forward a layered architecture for uplink bandwidth allocation function of OLT. The uplink bandwidth allocation function of OLT is partitioned into three layers: parameter management layer, DBA algorithm layer and hardware support layer. It separates the DBA algorithms from the functions for dealing with the report inform and recording the uplink bandwidth pos...
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