Research On Convergence Technologies Of Network Coding And Passive Optical Networks

The inter-optical network unit (ONU) communication in passive optical networks (PON) has been increasing with the rapid growth of peer-to-peer (P2P) services. As a promising technology, network coding has been introduced to PON only in recent years to efficiently support inter-ONU communication. According to the existing research, network coding technology is capable of reducing the packet loss caused by congestion in inter-ONU communication, efficiently saving the limited downstream bandwidth in PON, and relieving the pressure on the bandwidth of core networks by localizing the P2P services. In addition, by introducing network coding technology, OLT can save energy through the reduction to packet transmission time, and increase downlink throughput without changing the PON hardware. Thus, network coding in PON is a promising technology with practical application prospect, because it can enable significant network performance improvements with only software upgrades, which are of relatively lower cost and complexity.Upstream and downstream transmissions in PON have been changed by network coding, and some extra actions should be taken to fulfill the realization of network coding in PON and the QoS support to multiclass services in inter-ONU communication. All these issues need further studies. To this end, this dissertation starts off from the increasing demands of inter-ONU communication in PON and mainly focuses on the research on convergence technologies of network coding and PON. The contributions of this doctoral dissertation can be summarized as follows.1. The research on the singaling mechanism in PON with network coding (NC-PON). Upstream and downstream transmissions have been changed because of the introduction of network coding to PON. Thus, a signaling mechanism featured as "OLT domination" is proposed for NC-PON. In this signaling mechanism, downstream eavesdropping risk between ONUs and can be avoided and the implementability can be guaranteed. Moreover, the signaling mechanism can decrease not only the procedure complexity but also the burdens on ONUs in PON. Experiments have been conducted in the hardware platform of10G EPON with network coding to analyse and verify the implementation of network coding and the corresponding performance gain to PON. Experiment results show that1) network coding can be successfully implemented in PON with the help of the proposed signaling mechanism,2) the congestion in downstream channel can be postponed and the downstream throuput in PON can be improved by network coding in case of congestion.2. The research on the QoS support to multiclass services in NC-PON. QoS support issue has not been concerned in former DBA algorithm proposed for NC-PON. Thus, a multiclass services dynamic bandwidth allocation algorithm called MSDBA is proposed as a respond to the QoS support demand in NC-PON. In MSDBA, the "different coding principles in different sub-cycles" scheme has been firstly proposed, and it is integrated with the scheme in which different scheduling and bandwidth allocation schemes are applied to different classes of services. Both numerical analysis and simulation results show that compared with the existing two DBA algorithms (IPACT and APS) deployed in NC-PON, MSDBA not only demonstrates better performance in delay for all classes of services, but also achieves the maximum end-to-end delay fairness between coded and uncoded lower class services which is approximately equal to1, and guarantees the1.5ms end-to-end delay bound and fixed polling order of high class services by sacrificing their the end-to-end delay fairness for compromise.3. The research on the idle time elimination in upstream transmission of NC-PON. Idle time problem in upstream transmission also exists in NC-PON. Thus, a seamless dynamic bandwidth allocation scheme called DBA is proposed. In SDBA,"slidable REPORT window" scheme has been introduced for the first time for efficient upstream idle time elimination. Both numerical analysis and simulation results validate that compared with IPACT and APS, HDBA not only demonstrates the best performance in terms of queuing delay, scheduling delay and end-to-end delay for all classes of services, but also guarantees the fixed polling order and1.5ms end-to-end delay bound of high class services. Moreover, since the idle time in upstream transmission can be eliminated, both the end-to-end delay performances for all classes of coded and uncoded services and the corresponding delay fairness can be improved in SDBA as compared to those of MSDBA. Especially when the total traffic load is low, upstream bandwidth utilization in SDBA demonstrates significant improvement as compared to that in MSDBA.