IPACT With Grant Estimation (IPACT-GE) Scheme for Ethernet Passive Optical Networks

Dynamic bandwidth allocation (DBA) is an open and hot topic in the Ethernet passive optical network (EPON), which is regarded as one of the best choices for next-generation access networks. This paper proposes an estimation-based scheme, interleaved polling with adaptive cycle time with grant estimation (IPACT-GE), for effective upstream channel sharing among multiple optical network units (ONUs) in EPONs. By estimating the amount of new packets arriving between two consecutive pollings and granting ONUs with extra estimated amount, the proposed IPACT-GE scheme can achieve shorter waiting delay and less buffer occupancy at the light load than IPACT, a significant DBA scheme in EPONs. Moreover, when combined with the strict priority queue (SPQ) mechanism to provide differentiated services, IPACT-GE can greatly mitigate the light load penalty that is obvious in the IPACT solution combined with SPQ.      

Iterative resource pooling for bandwidth allocation in TDM-PON: algorithm, convergence and experimental evaluation

In this paper, we propose a new dynamic bandwidth allocation technique, SLIding Cycle Time (SLICT) for TDM-PON, specifically focused on ethernet passive optical network (EPON). Based on the sliding cycle time constraint, the proposed algorithm guarantees the maximum polling interval, an essential property for delay-sensitive applications and interactive services. We then introduce an iterative resource pooling that processes bursty best-effort traffic and achieves high throughput even under non-uniform upstream traffic distribution. We prove that greedy iterative resource pooling converges to equal resource allocation exponentially fast. Extensive numerical simulations show that SLICT outperforms existing techniques in all aspects: throughput, delay, packet loss and average queue size. Finally, SLICT has been implemented on an EPON FPGA board and the performance is confirmed under real traffic.     

EPON和WiMAX融合架构下带宽分配和调度机制的研究

以太网无源光网络(EPON)和IEEE 802.16(WiMAX)的融合网络在固定移动混合接入网中被认为是很有前景的接入方式.文中提出了3种WiMAX无线网络与EPON网络系统融合架构,融合系统同时具有光网络的高带宽和无线网络的灵活性.为了在接入网中支持QoS,本文为融合结构提出了一种动态带宽分配算法(DBA)和调度机...     

Analysis of mean packet delay for upstream transmissions in passive optical networks with sleep mode

The sleep mode has been introduced to improve the energy efficiency of passive optical networks (PONs) with interleaved polling with adaptive cycle time (IPACT) as a medium access control (MAC) scheme. For energy saving, the sleep mode of each optical network unit (ONU) is activated based on the packet queue length for upstream traffic. We model such a PON as an N-user M/G/1 queue with reservations and vacations. Based on the framework of M/G/1 queueing analysis with some modification made to incorporate the nature of IPACT as well as the sleep mode, we derive a closed form expression of the mean packet delay. A unique challenge in our analysis is that certain quantities such as the residual time of an on-going sleep period for the upstream channel must be considered from the network's viewpoint while the delay due to the sleep mode experienced by a packet must be considered from the ONU's viewpoint. Simulation experiments are conducted to validate the analytical results and to show that the results are relatively insensitive to packet arrival statistics for large sleep periods. Finally, we demonstrate how a sleep period can be chosen given the quality-of-service (QoS) requirement on the mean packet delay.     

Genetic expression programming: a new approach for QoS traffic prediction in EPONs

The Ethernet passive optical network is being regarded as the most promising for next-generation optical access solutions in the access networks. In time division multiplexing, passive optical network technology (TDM-PON) and the dynamic bandwidth allocation (DBA) play a crucial key role to achieve efficient bandwidth allocation and fairness among subscribers. Therefore, the traffic prediction in DBA during the waiting time must be put into the account. In this paper, we propose a new prediction approach with an evolutionary algorithm genetic expression programming (GEP) prediction incorporated with Limited IPACT referred as GLI-DBA to tackle the queue variation during waiting times as well as to reduce the high-priority packet delay. Simulation results show that the GEP prediction in DBA can reduce the expedited forwarding (EF) packet delay, shorten the EF queue length, enhance the quality of services and maintain the fairness among the optical network units (ONUs). We conducted and evaluated the detail simulation in two different scenarios with distinctive traffic proportion. Simulation results show that the GLI-DBA has EF packet delay improvement up to 30 % over dynamic bandwidth allocation for multiple of services (DBAM). It also shows that our proposed prediction scheme performs better than the DBAM when the number of ONUs increases.     

Predictive multicast polling for wireless networks with multipacket reception and queuing

In this paper, we propose the predictive multicast polling scheme for medium access control in wireless networks with multipacket reception capability. We concentrate on the case in which the packet arrival process is general and the maximum queue size is finite but larger than one. We derive both analytical results and simulation results. We use the theory of discrete-time Markov chain to analyze the evolution of the system state. In addition, we propose to use Markov reward processes to calculate the exact value of the network throughput. Furthermore, we obtain the average system size, the packet blocking probability, and the average packet delay. We show that our numerical results are consistent with simulation results. We also use simulation results to justify the usage of the proposed approach. Our study shows that the system performance can be significantly improved with a few additional buffers in the queues.     

轮询多址通信系统门限服务策略研究

从两方面对离散时间情况下轮询多址通信门限排队服务系统进行了研究。改进了系统服务策略，运用嵌入式马尔可夫链理论和多维概率母函数的方法，得到了改进后系统查询时间点处的平均排队队长和信息分组平均时延理论解析式，仿真结果表明分析方法有效且系统性能较之原系统得到提高；采用一种简化的近似算法，得到了轮询周期内平均队长的理论解析式，理论计算与仿真结果有较好的一致性。     

Inter‐ONU Bandwidth Scheduling by Using Threshold Reporting and Adaptive Polling for QoS in EPONs

I dynamic bandwidth allocation (DBA) scheme, an inter–optical network unit (ONU) bandwidth scheduling, is presented to provide quality of service (QoS) to different classes of packets in Ethernet passive optical networks (EPONs). This scheme, referred to as TADBA, is based on efficient threshold reporting from, and adaptive polling order rearranging of, ONUs. It has been shown that the network resources are efficiently allocated among the three traffic classes by guaranteeing the requested QoS, adaptively rearranging the polling orders, and avoiding nearly all fragmentation losses. Simulation results using an OPNET network simulator show that TADBA performs well in comparison to the available allocation scheme for the given parameters, such as packet delay and channel utilization.     

Controlling QoS in EPON-based FTTX access networks

The Ethernet PON (EPON) is viewed by many as an attractive solution to deliver very high-speed broadband access and is widely deployed in some geographical areas. While downstream traffic is broadcast to all customers, the access of upstream traffic to the fiber has to be arbitrated in order to avoid collisions. This arbitration mechanism and more generally, bandwidth distribution and QoS Provisioning, have been left to the implementer. One solution is to enforce static Time Division Multiplexing Access (TDMA) between end-users. This however precludes an efficient usage of resources. Interleaved Polling with Adaptive Cycle Time (IPACT) is one of the earliest proposed schemes for Dynamic Bandwidth Assignment (DBA) in EPON and has been extensively used as a benchmark by many subsequent allocation schemes. In this paper, we first propose an analytical model which yields approximate values for mean queue length and mean packet delay in an EPON using IPACT with Gated Service (GS) scheme under the assumption of heterogeneous Poisson arrivals. We use the model to demonstrate that all users experiment performance degradation in case of local overload, thus showing the necessity of correcting somehow IPACT-GS in order to avoid this phenomenon. This is achieved by designing a control plane for EPON, which includes a priority based DBA together with a framework for enforcing Service Level Agreements (SLAs), and fairly sharing available resources. The proposed framework is easily configured (all the control being centralized at the OLT or in the backbone) while allowing the support of large varieties of services. It is shown to behave more efficiently than other QoS sensitive DBAs in the literature.     

多级门限服务轮询系统MAC离散时间控制协议模型分析

 本文提出了一种新的多级门限服务轮询系统MAC控制协议的分析模型.采用嵌入马尔可夫链理论,对离散时间的多级门限服务轮询系统进行了分析,获得了轮询时刻系统队长的概率母函数,精确解析了系统的平均排队队长、平均循环周期、信息分组的平均等待时延.通过对多级门限服务轮询系统的控制机理研究,分析获得了m控制参数的有效控制取值大小和系统的相关特性.多级门限服务轮询系统综合了基本门限服务轮询系统和完全服务轮询系统,在轮询系统的MAC控制协议的应用方面更为有效.     

Optical Coding for Enhanced Real-Time Dynamic Bandwidth Allocation in Passive Optical Networks

In this paper, optical pulse encoding and decoding technology is proposed to enable real-time signaling in a passive optical network (PON) setting. Unique optical codes are assigned to selected optical network units (ONUs) equipped with the corresponding encoders. An out-of-band pulse train is broadcast from the optical line terminal (OLT) and is modulated by ONU-based switches. The encoded reflections of pulses are thus used to update the status of the OC-enabled queues at the OLT in real time. We explore the enhanced PON architecture and define its major design parameters. Through extensive simulations, we investigate the design principles and limits of our system parameters. Through a performance comparison of native interleaved polling with adaptive cycle time with its OC-enhanced counterpart, we show that our OC enhancement breaks the fundamental delay lower bound associated to the polling cycle. We propose and investigate new dynamic bandwidth allocation (DBA) algorithms that exploit real-time queue updates enabled through OC-enhanced polling. We also explore the pay-as-you-grow implementation of OC-enhanced polling to realize quality-of-service (QoS) differentiation, elaborate on possible migration paths from conventional PONs, and investigate absolute QoS performance guarantee improvements achieved through OC-enabled real-time DBA algorithms.     

在工业网中EPON的DBA算法研究

EPON系统中,上行数据传输的动态带宽分配（DBA）算法是关键技术之一。针对EPON在工业网络通信中的应用,对现有的DBA算法进行了分析和改进,以保证监控和报警等特殊业务的实时送达,消除交叉轮询的带宽浪费,并对该算法进行了仿真实验。仿真结果表明,该算法的带宽利用率高,业务时延抖动低,并且在低负载时无轻载惩罚现象。     

Delay analysis for CBR traffic under static-priority scheduling

We examine the delay performance of packets from constant-bit-rate (CBR) traffic whose delay is affected by non-real-time traffic. The delay performance is analyzed by solving the nD/D/1 queue with vacations. We obtain an exact and closed form solution, hence obviating the need of any approximations or numerical Laplace inversions. We then provide various numerical results for low-bit-rate transmission links, in which packets can experience large delay. From our quantitative evaluation, we conclude that there exists an optimum packet size for a given delay bound. In extremely slow links, such as modem links, transmission control protocol (TCP) packets should be segmented to reduce the CBR delay. We therefore investigate the delay impact of TCP packet sizes as well     

离散时间闸门式多级门限服务的两级优先级轮询排队系统分析

本文提出了一种基于闸门式多级门限服务的两级优先级轮询系统.论文先构建了系统的排队分析模型,然后把模型中各个站点内的等待顾客数合起来设定为系统状态变量,对系统状态变量的概率母函数求二阶偏导后组成迭代方程组,联立求解后得到了站点的平均排队队长、顾客平均等待时间以及服务器查询周期等关键指标的完整数学解析表达式.最后,对该模型进行了仿真实验分析,实验结果与理论结果相一致.系统性能分析表明该轮询系统满足了周期性系统服务资源分配过程中业务多样性和弹性服务的发展需求,使得轮询控制策略应用方面更为广泛.     

一种支持多用户SLA的EPON上行带宽分配算法设计

在接入网服务等级协定的基础上,分析了以IPACT和CyclicDBA为代表的EPON上行动态带宽分配算法,讨论了其对EPON上多用户SLA支持所存在的固有缺陷。提出了适合SLA应用的EPON控制帧结构:授权帧和请求帧。根据这两种控制帧,设计了一种新型的支持多用户SLA的EPON上行信道带宽分配算法,等级轮询固定周期算法。通过理论分析和计算机仿真测试表明该算法针对EPON不同类型的接入用户均达到了较理想的性能指标,高优先级业务良好的时延和时延抖动特性,各种业务队列的尺度平稳,同时HPFCT还解决了传统轮询算法中低负载时下行带宽浪费明显的问题。     

Multi-thread polling: a dynamic bandwidth distribution scheme in long-reach PON

With the advances in optical technology, the span of a broadband access network using Passive Optical Network (PON) technology can be increased from today's standard of 20 km to 100 km or higher, and thereby serve a lot more users. Such an extended-reach PON is known as SuperPON in the literature, and we call it a Long-Reach PON (LR-PON). A major challenge in LR-PON is that the propagation delay (for data as well as control signals) between the telecom central office (CO) and the end user is increased by a very significant amount. Now, traditional PON algorithms for scheduling the upstream transmission, such as dynamic bandwidth allocation (DBA) algorithms, may not be sufficient; actually, they may lead to degraded performance because of the long delay of the CO-to- Users "control loop." This challenge motivates us to propose and study a multi-thread polling algorithm to effectively and fairly distribute the upstream bandwidth dynamically. This algorithm exploits the benefits of having multiple polling processes running simultaneously and enabling users to send bandwidth requests before receiving acknowledgement from the CO. We compare the proposed algorithm with traditional DBA, and show its advantage on average packet delay. We then analyze and optimize key parameters of the algorithm, such as initiating and tuning multiple threads, inter-thread scheduling, and fairness among users. Numerical results demonstrate the algorithm's advantage to decrease the average packet delay and improve network throughput under varying offered loads.     

Convergence of ethernet PON and IEEE 802.16 broadband access networks and its QoS-aware dynamic bandwidth allocation scheme

IEEE 802.16 and Ethernet Passive Optical Network (EPON) are two promising broadband access technologies for high-capacity wireless access networks and wired access networks, respectively. They each can be deployed to facilitate connection between the end users and the Internet but each of them suffers from some drawbacks if operating separately. To combine the bandwidth advantage of optical networks with the mobility feature of wireless communications, we propose a convergence of EPON and 802.16 networks in this paper. First, this paper starts with presenting the converged network architecture and especially the concept of virtual ONU-BS (VOB). Then, it identifies some unique research issues in this converged network. Second, the paper investigates a dynamic bandwidth allocation (DBA) scheme and its closely associated research issues. This DBA scheme takes into consideration the specific features of the converged network to enable a smooth data transmission across optical and wireless networks, and an end-toend differentiated service to user traffics of diverse QoS (Quality of Service) requirements. This QoS-aware DBA scheme supports bandwidth fairness at the VOB level and class-of-service fairness at the 802.16 subscriber station level. The simulation results show that the proposed DBA scheme operates effectively and efficiently in terms of network throughput, average/maximum delay, resource utilization, service differentiation, etc.     

分组交换网中两路合用系统的性能分析

本文提出一种级联排队模型对两合用系统了系统建模，并且利用矩阵几何解析法对该模型进行精确的理论分析，推导出分组平均延迟时间和两条链路的平均利用率这两个重要的性能指标。     

非对称周期查询限定服务系统解析

本文利用嵌入马尔可夫链理论和概率母函数的方法,对局域网络中离散时间状态下,有限缓冲器的非对称周期查询限定(k=1)服务系统 ∑ N i G_i/ ∑ N i G_i/1( ∑ N i G_i)/ ∑ N i S_i(FCFS)模型进行了解析,获得了系统第i队列的查询周期、信息分组平均队长、信息分组平均延时和信息分组丢失率的数学解析表达式.计算机模拟的结果表明了仿真与理论的一致性.     

Performance Evaluation of Ethernet Frame Burst Mode in EPON Downstream Link

We apply IEEE 802.3 frame burst mode (FBM) to the Ethernet passive optical network (EPON) downstream link and compare its performance with non‐frame burst mode for various traffic patterns. Although in light traffic loads (ρ<0.5) the efficiency of the FBM mechanism is not significant, it does feature high throughput, small jitter, low queue occupancy, and short queuing delay in optical line terminals under various traffic loads with various numbers of optical network units (ONUs). The FBM performance always approaches that of full‐duplex mode, especially under heavy traffic loads (ρ>0.5). Moreover, an increase in number of ONUs will decrease the burst performance. Our work shows that FBM scheme is very useful for EPON transmission and has low design complexity.