Successful Migration of EPON to WDM EPON

摘要

In the last decade, Ethernet passive optical networks (EPONs) have been considered as a potential optimized architecture for the access network. However, because of the steady increase in the number of users and bandwidth-hungry applications, although standardized, current single-channel systems cannot satisfy the growing traffic demands in the future. Accordingly, this review further suggests the implementation of wavelength division multiplexing (WDM) technology in EPONs in order to overcome problems that exist in classical single-channel systems. Until today, different models for incremental migration from TDM to TDM/WDM EPON networks have been proposed but most attention is given to those solutions that support quality of service (QoS) implementation. Moreover, with the rapid development of different bandwidth applications QoS support is becoming a key concern in WDM EPON network as was similarly the case in EPON networks. In this chapter, we address many of these issues and present models and algorithms that we believe could resolve these issues. In the first place, we briefly present a theory of differentiated services which represents a basis for the QoS implementation in Ethernet-based networks, and discuss the most important aspects of QoS support and implementation in WDM EPONs. Within our main contribution, we further present and analyze two models for wavelength and bandwidth allocation in hybrid TDM/WDM EPON system with full QoS support, namely the fixed wavelength priority bandwidth allocation (FWPBA) model, and the dynamic wavelength priority bandwidth allocation (DWPBA) model. In order to implement QoS support we present a new approach for QoS analysis and implementation in WDM EPON in which wavelength assignment takes place per service class and not per ONU, a case which is widely suggested by the common approach in literature. Beside this, we propose a method for providing an upgrade to WDM in EPONs that includes an extension of the multipoint control protocol (MPCP). In this way, the presented architecture and models will allow an incremental upgrade from TDM EPON to TDM/WDM EPONs. For each of the proposed models, wavelength and bandwidth allocation algorithms with full QoS support have been presented in order to fulfill all of the requirements necessary for new applications in a converged triple-play network. The presented models and algorithms have been compared in terms of average and maximum packet delay, packet variation delay (jitter), queue occupancy, packet loss rate, throughput and overall system performance. Detailed simulation experiments are presented with the aim of conducting a study of the performance and obtaining the validation of the effectiveness of the presented solutions. In conclusion, we conclude our review and suggest direction for future work.