A new MAC PROTOCOL WITH DIFFERENT PRIORITY FOR TRAFFIC CLASSES over ATM-PON system

Abstract

An ATM-PON system is designed in order to satisfy end-to-end ATM connections using PON technology. Because it is based on a shared-medium network and a point-to-multipoint optical tree configuration, a PON access system requires a MAC protocol for the upstream traffic. In the Recommendation G.983.1, the ITU-T has standardized Time Division Multiple Access (TDMA) technique as a MAC protocol for ATM-PON and the basic concept of a MAC protocol, but it does not standardize the format for conveying bandwidth request information and the MAC protocol. Many studies on this topic have been reported. But, unfortunately, a MAC protocol including bandwidth allocation algorithm has not been specified in the ITU-T, and remains an open issue. In this thesis, we propose a MAC protocol which supports the frame format and the MAC protocol of ITU-T recommendation G.983.1 and has different priority for ATM traffic categories such as CBR, rt-VBR, nrt-VBR, ABR, and UBR traffics. The proposed scheme also allocates bandwidth among ONUs, fairly and dynamically. The proposed frame format follows standardization, and has high efficiency (83.7% in case of 32 ONUs, 76.9% in case of 64 ONUs). Each service is allocated on the basis of priority and cell arrival timing information. The bandwidth has to be allocated on two different levels: among the different ONUs and among the different traffic classes supported by the proposed MAC protocol (CBR/rt-VBR, nrt-VBR, ABR, and UBR). CBR and rt-VBR traffics have the highest priority, and then bandwidth allocation algorithm grants for these first. Especially, the CBR and rt-VBR services, which are sensitive to Cell Transfer Delay (CTD) and Cell Delay Variation (CDV), are allocated with higher priority and more cell arrival timing information. After the grants of CBR/rt-VBR are allocated, each grant for nrt-VBR, ABR, and UBR having priorities according to the following order: nrt-VBR, ABR, and UBR. When the OLT have no CBR/rt-VBR, nrt-VBR or ABR...