Research On Multiple Access Technology For Ethernet Passive Optical Network

For a long time, the development in the access network area is much slower than that in the backbone and the LAN areas. This makes "Last mile" become the bottleneck of the network. Now the broadband access network is one of the focuses of the network research. Ethernet Passive Optical Network (EPON) is viewed by many as an attractive solution to this problem. EPON has a tree topology and transfers multiple traffics by the use of ethernet frame. In the upstream direction, all ONUs share the trunk fiber channel. To avoid the collision, the multiple access technology is needed. TDMA is the most appropriate multiple access technology at the current technology state. The Round-Trip Time (RTT) for each ONU is different due to the different distance from OLT to each ONU, and the environment also affects the RTT. To reduce packet delay and avoid the data collision in upstream, the TDMA-EPON needs a mechanism to measure the RTT so as to compensate the differences between the ONUs' propagation delays; Furthermore, to make a good use of the network resources, it should be adopt Statistical TDMA and provide Dynamic Bandwidth Allocation (DBA) scheme to the ONUs. These two problems are included in how to design an upstream access scheme which is the emphasis of the research in this thesis.In this thesis, the evolvement, advantages, promising application and market of EPON are introduced and analysed; The structure of EPON system and the function of each part are discussed; Several current multiple access technologies are compared and ayalysed, it shows that Statistical TDMA is the best choice at the current technology state. After lucubrating the IPACT scheme, aiming at its weakness, two jobs are carried out: one is developing a novel bandwidth allocation service for IPACT, another is designing a whole novel upstream access scheme-Broadcast Polling which has better capability than IPACT to support SLA. The performances of the two designes are researched by computer simulation. For simulation, the models of EPON and self-similar traffic are built. The results of the simulation show that both the designes work well. At last, the advice of the further research is presented.