Research On Key Technologies Of Clustering OLT-based Flexible And High Efficient Optical Access Network

The high-speed network services represented by 4K/8K high-definition video,3D video streaming,and augmented reality will continue to stimulate rapid growth in the bandwidth demand of access network.Meanwhile,the fast spread of optical fiber access in fixed network and 4G terminals in mobile network,as well as the subscribers' habit of cloud access at anytime and anywhere,will promote more traffic-intensive areas and endue the access network with dynamic load characteristic.Moreover,the clear demands of enhanced bandwidth and ultra-low latency of 5G networks will also require access network to support both diverse user interoperability and differentiated service bearing.The access network will face not only the challenge of capacity expansion but also the challenge of meeting various services' functional,performance,and scale needs brought by unified multi-service transmission.Although the passive optical network(PON)has made great strides in bandwidth capacity through wavelength division multiplexing,orthogonal frequency division multiplexing,etc.,the PON-based optical network is still limited to fiber capacity and the costs sensitive feature.The traditional method of simple incremental capacity expansion and customized deployment of PON in specific scenarios will be difficult to continuously solve bandwidth problems with fluctuation characteristics and unified multi-service bearing problems.Moreover,the fixed PON architecture,the status of co-deployment of equipments from different manufacturers and the facts that simply using PON as a transmission pipe in access network also cause the difficulty in unified resource scheduling and limit the clustering optical line terminals(OLTs)cooperate as a resource pool.Those phenomena have greatly limited the access network's ability to flexibly and efficiently bearing diverse network services.Therefore,this paper mainly focuses on the key issues of constructing the flexible and efficient optical access network,and conducts research work on architecture design,bandwidth efficient grooming mechanism and low latency fronthaul network bearing mechanism.Specifically,the main research content and innovations of this paper include:1.A flexible clustering OLT-based optical access network architecture is proposed.The proposed architecture mainly focuses on the unified and efficient multi-service bearing demands of the future access network,and consists of central office(CO),optical distribution network(ODN)and optical network unit(ONU)solution that can support flexible and efficient network management.The features of this architecture include:software-defined networking(SDN)is introduced in the design of CO equipments,and both the fixed and mobile data transmission can be beared by packetized PON system.A shared optical link matrix deployed in CO is proposed to connect the clustered OLTs and ONUs and support flexible change of the OLT-ONU affiliations.It can provide wavelength-and link-level resource scheduling while the current ODN can still remain passive.Moreover,the fast ONU migration scheme and the unified interface between control and forward plane are designed to support flexible and efficient resource management,and the extended OpenFlow protocol is used to transmit the control information of the physical layer and data link layer devices.Besides,the flexible and efficient unified control based on non-SDN devices is also experimentally verified.2.An efficient access network traffic grooming mechanism based on dynamic ONU grouping is proposed.In response to the efficient bandwidth bearing demand for metro-access convergence network,the proposed mechanism uses flexible ONU grouping under the above mentioned flexible architecture to partition different ONUs into different OLTs.Thus the OLT uplink bandwidth utilization can be improved by making use of the switching capabilities of the OLTs as much as possible and avoiding excessive data traffic entering the metro or even the core network.The features include that the dynamic ONU grouping scheme based on TWDM PON system and the ONU dynamic grouping algorithm(DGA)with low complexity are proposed to reduce the OLT outbound traffic brought by peer to peer traffic.The simulation results show that,compared to original random ONU grouping,DGA can achieve inter-OLT traffic reduction,and with the increase of ONU number,the increment of average reduced inter-OLT traffic under different OLT number can range from maximum 3.6%to 76.34%.Since the DGA can be deployed as an application running on the control plane,the proposed scheme can help improve the network efficiency in future traffic-intensive access scenarios.3.An efficient mobile fronthaul network bearer mechanism based on joint bandwidth and latency constrained(JBL)ONU grouping algorithm is proposed.Aiming at fulfilling the ultra-low latency requirement while deploying TDM PON into 5G mobile fronthaul(MFH),as well as improving the bandwidth utilization of MFH,the above-mentioned clustering OLT-based flexible access network architecture is adapted into MFH.The polling cycle adaptive scheme for network slicing and JBL ONU grouping algorithm is proposed.The influence of the propagation time is analyzed to construct the JBL grouping algorithm,and with the help of JBL,the proposed mechanism can provide different polling cycle for different network slice scenarios,and the ONU latency can be adjusted flexibly under the constraint of overall latency.The simulation results indicate that,under the condition that the ONU latency constraint is satisfied,the bandwidth utilization of the heavy-load wavelength can reach more than 94%.Meanwhile,compared with the non-grouping situation and under different initial simulation conditions,the average polling cycle can have an average increase of 98%and maximum reduce of 36?s.The adaptive polling cycle can lower the performance requirement of the hardware device(such as a burst mode transmitter),expands the MFH coverage,and improves the channel utilization.