Study On The Efficient User Access Control Technology In NG-EPON

With the emergence of new industries such as big data,cloud computing,virtual reality and 4K/8K HD video,user bandwidth demand for network access rate keeps increasing.As one of the most popular solutions for the "last mile" network access,passive optical network(PON)can provide strong broadband access capability.The existing PON technologies such as EPON,GPON,10G-EPON and XG(S)-PON,can provide users with high-speed broadband access data rate.However,as the network bandwidth demand is increasing at an annual rate of 50%,the current PON technology will not meet the huge bandwidth demand of future network service in a few years.It is very important and urgent to study the PON technology with higher bandwidth access rate for the huge bandwidth demand in the near future.To this end,the IEEE set up the802.3ca task force to study the next generation Ethernet Passive Optical Network(NG-EPON),which can provide up to 100 Gb/s access rate.On the basis of time-division multiplexing,NGEPON stacks multiple wavelengths to enhance the overall bandwidth capacity,while introducing channel bonding to enhance the bandwidth capability of single ONU.In NG-EPON,ONUs are equipped with multiple transceivers,which enable ONUs to operate on multiple wavelengths at the same time with channel bonding.NG-EPON's new features,namely multi-wavelength and channel bonding,can bring great capacity enhancement,as well as challenges to user access control.This thesis concentrates on user access control,and investigates user registration,resource scheduling and user management in NG-EPON based on the new features such as multiwavelength and channel bonding.This thesis puts forward the multi-channel ONU registration protocol,resource scheduling mechanisms and ONU aggregation management schemes,to achieve the rapid user access and the fine management and efficient utilization of resources in NG-EPON.The detailed work in this thesis is listed as follows:(1)User registration in NG-EPONDue to channel bonding,NG-EPON ONUs can operate on multiple wavelengths simultaneously.In order to ensure the transmission reliability,ONUs are required to be verified on each of their capable wavelengths during registration.Unfortunately,the traditional EPON user registration protocol,designed for single wavelength scenario,cannot be directly applied to NG-EPON.If we simply extend traditional user registration protocol to multi-wavelength NGEPON,the registration delay would be very large,because ONUs need to compete in discovery windows on each wavelengths and the delay depends on the latest completion time.Fast service access cannot be provided in such way.Taking both transmission reliability and registration efficiency into account,a coordinated registration protocol based on the cooperation of channel terminals is proposed in this thesis.By modifying the protocol process,the coordinated registration protocol only needs ONUs to register successfully at any wavelength,and can utilize the cooperation of other channel terminals to verify the transmission reliability of the remaining wavelengths.By this way,the ONU can get registered in all wavelengths.In addition,this thesis extends the traditional registration data unit and state diagrams,which can be well applied to the cooperative registration protocol,while maintaining the backward compatibility with the traditional 1G-EPON and 10G-EPON.In order to evaluate the performance of the simply-extended and the coordinated registration protocols,this thesis analyzes the registration process of the two protocols,derives the theoretical registration delay,and conducts simulation experiments.Both theoretical and simulation results show that the coordinated registration protocol can effectively reduce the registration delay and greatly accelerate the access speed of users.(2)Resource scheduling in NG-EPONThere exist different types of ONUs according to their bonded channel amounts.Different types of ONUs have different wavelength capabilities.In the resource scheduling,i.e.,dynamic wavelength and bandwidth allocation,it is necessary to consider the different ONU wavelength capabilities,the corresponding bandwidth capacity constraints and the fairness problem between different types of ONUs.In order to ensure efficient and fair allocation of bandwidth resources among different types of ONUs,this thesis decouples bandwidth allocation and wavelength allocation.A weighted max-min fair bandwidth allocation algorithm based on multiple threshold is proposed.The wavelength allocation sequences of different types of ONUs are studied.The efficient,fair and flexible resource scheduling of multiple types of ONUs in NG-EPON is realized.In addition,the parallel transmission of Ethernet packets with variable sizes will lead to packet reordering problem.Resequncing packets requires some buffer and processing delay.To solve this problem,a dynamic wavelength and bandwidth allocation algorithm is proposed to mitigate frame reordering.Each ONU's grant is allocated to single wavelength as much as possible and grant readjustment is implemented based on the allocation results.Proposed algorithm can significantly reduce the number of packet reordered ONUs.Both theoretical and simulation results show that the number of packet reordered ONUs is smaller than the wavelength number and irrelevant to ONU number.In the online scheduling mode,the OLT makes fast wavelength and bandwidth decision for each ONU.The thesis studies the impacts of different wavelength allocation patterns on network performance,and proposes an adaptive wavelength allocation pattern that considers both the overall traffic load and single ONU's traffic load.Proposed adaptive wavelength allocation pattern can achieve smaller packet and larger bandwidth throughput.(3)User aggregation management in NG-EPONFor the sake of energy saving and service protection,the OLT can shut off some working wavelengths and aggregate ONUs to the remaining active wavelengths,based on the tidal effect of user number and traffic amount.Due to the coexistence of different ONU working wavelength capabilities in NG-EPON,the OLT must carefully select the aggregation wavelengths by considering the diversity of ONU working wavelength capabilities.Aggregation wavelengths cannot be selected arbitrarily even all the traffic load is light enough to be carried by one wavelength.Instead,in order to ensure the aggregation of all ONUs,aggregation wavelengths must be selected to cover all the ONUs with different wavelength capabilities.Further consideration of the traffic load makes the problem more complex,and the different wavelength capabilities and the corresponding load will lead to different choices of minimal aggregation wavelengths.In this paper,we use graph theory to analyze the problem of wavelength aggregation in NG-EPON,and convert it to the capacitated set cover problem.A two-step heuristic algorithm is proposed to solve the problem of wavelength aggregation.The proposed two-step algorithm has low complexity and good performance.It can quickly find the minimal aggregation wavelengths and give detailed wavelength migration paths for each ONU,which promotes smart operation and management for operators.To sum up,this thesis investigates efficient user access control technologies in NG-EPON.Thie thesis refers to the related proposals in IEEE 802.3ca task group,the research issues come from thinking about the influence of new features in NG-EPON on user access control.This thesis investigates several important aspects of user access control in NG-EPON,which could provide useful information for related research,drive and promote the standardization process of user access control in IEEE 802.3ca NG-EPON.