A survey of dynamic bandwidth allocation algorithms for Ethernet Passive Optical Networks

Ethernet Passive Optical Network (EPON) has been widely considered as a promising technology for implementing the FTTx solutions to the “last mile” bandwidth bottleneck problem. Bandwidth allocation is one of the critical issues in the design of EPON systems. In an EPON system, multiple optical network units (ONUs) share a common upstream channel for data transmission. To efficiently utilize the limited bandwidth of the upstream channel, an EPON system must dynamically allocate the upstream bandwidth among multiple ONUs based on the instantaneous bandwidth demands and quality of service requirements of end users. This paper introduces the fundamental concepts on EPONs, discusses the major issues related to bandwidth allocation in EPON systems, and presents a survey of the state-of-the-art dynamic bandwidth allocation (DBA) algorithms for EPONs.     

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.     

Hierarchical Dynamic Bandwidth Allocation Algorithm for Multimedia Services over Ethernet PONs

In this paper, we propose a new dynamic bandwidth allocation (DBA) algorithm for multimedia services over Ethernet PONs (passive optical networks). The proposed algorithm is composed of a low‐level scheduler in the optical network unit (ONU) and a high‐level scheduler in the optical line terminal (OLT). The hierarchical DBA algorithm can provide expansibility and efficient resource allocation in an Ethernet PON system in which the packet scheduler is separated from the queues. In the proposed DBA algorithm, the OLT allocates bandwidth to the ONUs in proportion to the weight associated with their class and queue length, while the ONU preferentially allocates its bandwidth to queues with a static priority order. The proposed algorithm provides an efficient resource utilization by reducing the unused remaining bandwidth caused by the variable length of the packets. We also define the service classes and present control message formats conforming to the multi‐point control protocol (MPCP) over an Ethernet PON. In order to evaluate the performance, we designed an Ethernet PON system on the basis of IEEE 802.3ah “Ethernet in the first mile” (EFM) using OPNET and carried out simulations. The results are analyzed in terms of the channel utilization, queuing delay, and ratio of the unused remaining bandwidth.     

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.      

Per-Stream QoS and Admission Control in Ethernet Passive Optical Networks (EPONs)

Ethernet passive optical networks (EPONs) are designed to deliver services for numerous applications such as voice over Internet protocol, standard and high-definition video, video conferencing (interactive video), and data traffic. Various dynamic bandwidth allocation and intra-optical network unit (ONU) scheduling algorithms have been proposed to enable EPONs to deliver differentiated services for traffic with different quality of service (QoS) requirements. However, none of these protocols and schedulers can guarantee bandwidth for each class of service nor can they protect the QoS level required by admitted real-time traffic streams. In this paper, we propose the first framework for per-stream QoS protection in EPONs using a two-stage admission control (AC) system. The first stage enables the ONU to perform flow admission locally according to the bandwidth availability, and the second stage allows for global AC at the optical line terminal. Appropriate bandwidth allocation algorithms are presented as well. An event-driven simulation model is implemented to study the effectiveness of the proposed schemes in providing and protecting QoS.     

Architecture of multi-OLT PON systems and its bandwidth allocation algorithms

In this paper, we propose a novel passive optical network (PON) architecture that has multiple optical line terminals (OLTs). Unlike existing PONs where all ONUs are connected to a single OLT, the proposed multi-OLT PON allows subscribers to choose their own service providers from among multiple OLTs. Service companies and subscribers can make service level agreements (SLA) on the amount of bandwidth that each OLT or ONU requires. A new control protocol and bandwidth allocation algorithms appropriate in this new PON environments are suggested. For the downstream, a scheme to share the bandwidth among multiple OLTs is studied to maximize the total transmitted packets while guaranteeing each OLT’s SLA. A modified Limited Dynamic Bandwidth Allocation named mLimited scheme is also proposed for upstream transmission toward multiple OLTs, which maximizes the total upstream throughput while minimizing the delay of each ONU. Performances of the proposed PON architecture and algorithms are analyzed. A PON system with two OLTs and 16 ONUs is used in the analysis. Self-similar traffic reflecting current packet distribution is used in the packet generation. The results show that the proposed DBA schemes efficiently manage bandwidth even when the occurred traffic load is quite different from the reserved bandwidth. It is found that the proposed PON architecture is appropriate in supporting diverse services in future high-speed optical access network.     

Bandwidth allocation for multiservice access on EPONs

Ethernet passive optical networks are a low-cost high-speed solution to the bottleneck problem of the broadband access network. A major characteristic of EPONs is the shared upstream channel among end users, mandating efficient medium access control to facilitate statistical multiplexing and provision multiple services for different types of traffic. This article addresses and provides an overview of the upstream bandwidth allocation issue for multiservice access provisioning over EPONs, and proposes an algorithm for dynamic bandwidth allocation with service differentiation. Based on the multipoint control protocol (MPCP) and bursty traffic prediction, our algorithm enhances QoS metrics such as average frame delay, average queue length, and frame loss probability over other existing protocols     

Dynamic Bandwidth Allocation Algorithm for Multimedia Services over Ethernet PONs

Ethernet passive optical networks (PONs) are an emerging access network technology that provides a low‐cost method of deploying optical access lines between a carrier's central office and a customer site. In this paper, we propose a new algorithm of dynamic bandwidth allocation for multimedia services over Ethernet PONs. To implement the suggested dynamic bandwidth allocation algorithm, we present control message formats that handle classified bandwidths in a multi‐point control protocol of Ethernet PONs.     

Cyclic Polling-Based Dynamic Bandwidth Allocation for Differentiated Classes of Service in Ethernet Passive Optical Networks

Ethernet passive optical networks (EPONs) are an emerging access network technology that provides a low-cost method of deploying optical access lines between a carrier's central office and customer sites. Dynamic bandwidth allocation (DBA) provides statistical multiplexing between the optical network units for efficient upstream channel utilization. To support dynamic bandwidth distribution, a cyclic polling-based DBA algorithm for differentiated classes of service in EPONs is proposed. It is shown that an interleaved polling scheme severely decreases downstream channel capacity for user traffic when the upstream network load is low. To obtain realistic simulation results, synthetic traffic that exhibits the properties of self-similarity and long-range dependence is used. Network performance under various loads is analyzed. Specifically, frame delays for different classes of traffic are considered.     

TOPICS IN OPTICAL COMMUNICATIONS - STARGATE: The Next Evolutionary Step toward Unleashing the Potential of WDM EPONs

WDM EPONs are rapidly becoming mature. In this article we briefly review the state of the art of cost reduction, colorless ONUs, and WDM PONs. We then lift the veil of future WDM EPONs, and elaborate on evolutionary cost-effective upgrades of WDM EPONs and their all-optical WDM integration with Ethernet-based metropolitan area networks to provide transparent connections at the wavelength and sub-wavelength granularity on demand between ONUs residing in different WDM EPONs     

DBA algorithm for the support of multi-tiered bandwidth guarantee in Ethernet passive optical networks

Access Networks based on Passive Optical Network (PON) technology can offer transport services to broadband service providers, such as mobile backhauling/fronthauling for Mobile Network Operators and multi-ONU Service Level Agreements for Virtual Network Operators. Besides that, Infrastructure Service Provider (InP) also provides broadband access services to end-users, such as residential subscribers and single or multi-site enterprises. In such a scenario, the InPs support diverse customers in the same PON. This paper proposes a bandwidth slicing mechanism to assure bandwidth isolation for different PON customers who rent part of a PON infrastructure from the InP. We introduce a Dynamic Bandwidth Allocation algorithm for Ethernet PONs called MAB-IPACT, which assures bandwidth on different granularity: conventional customers with a single ONU, multi-ONU customers owning a group of ONUs and providing a single type of service, and multi-ONU customers having diverse types of services. The MAB-IPACT algorithm also prioritizes bandwidth distribution among subgroups of ONUs of the same multi-ONU customer. A subgroup of ONUs is a subset of ONUs that belongs to the same multi-ONU customer, which are employed for the same type of service (e.g., ONUs for business service.). Simulation results show that the proposed mechanism improves the network performance of multi-ONU customers with subgroups of ONUs serving different services.

     

以太网无源光网络中的时间标签法测距

基于千兆以太网的无源光网络将千兆以太网与无源光纤接入的优势相结合,实现低成本的高速、远距离接入。针对EPON系统上行链路多个ONU共享带宽的树型拓扑结构,为实现EPON系统上行TDMA接入,提出了时间标签法测距方案,论述了方案的可行性并指出其优点。     

EPON中一种动态带宽分配算法

以太无源光网络(EPON)被认为是下一代宽带接入的最有效的解决方案。文章提出了一种新的基于EOPN提供多种服务的动态带宽分配算法。为了能够应用这种算法还给出了协助带宽分配多点控制协议(MPCP)的控制消息的格式。     

Resource allocation using adaptive linear prediction in WDM/TDM EPONs

This letter discusses dynamic-wavelength and bandwidth-allocation (DWBA) algorithm for differentiated services in hybrid WDM/TDM EPONs (Ethernet passive optical networks). We integrate the traffic estimation for variable-bit-rate (VBR) video traffic with the resource allocation to satisfy the increasing demand of video streaming services. A new DWBA algorithm using an adaptive linear prediction model is proposed to estimate the bandwidth required by VBR video traffic arriving during the next waiting period, so that the DWBA algorithm can assign wavelength and bandwidth more effectively. Simulation results show that the proposed DWBA-ALP algorithm can significantly improve the delay jitter performance for both CBR and VBR services.     

Sleep assistive dynamic bandwidth assignment scheme for passive optical network (PON)

In passive optical network (PON), in addition to efficient bandwidth management, a dynamic bandwidth assignment (DBA) scheme can also enhance the energy efficiency performance of the optical networks units (ONUs) during sleep mode. A few such green DBA schemes have been proposed in literature for EPON, however, ITU compliant PONs have not got attention. In this study, the role of a DBA scheme during the cyclic sleep mode for XGPON has been investigated. A sleep assistive (SA)-DBA scheme is proposed that not only improves the energy saving performance of cyclic sleep mode but also reduces the upstream delays and variance for all the type-2 (T2), type-3 (T3) and type-4 (T4) traffic classes. Although, the upstream delay of type-1 (T1) traffic class slightly increases, the average upstream delay of all the traffic classes remains below the set target delay limit of 56 ms.     

Enhanced Dynamic Bandwidth Allocation Algorithm in Ethernet Passive Optical Networks

As broadband access is evolving from digital subscriber lines to optical access networks, Ethernet passive optical networks (EPONs) are considered a promising solution for next generation broadband access. The point‐to‐multipoint topology of EPONs requires a time‐division multiple access MAC protocol for upstream transmission. In this paper, we propose a new enhanced dynamic bandwidth allocation algorithm with fairness called EFDBA for multiple services over EPONs. The proposed algorithm is composed of a fairness counter controller and a fairness system buffer in the optical line terminal. The EFDBA algorithm with fairness can provide increased capability and efficient resource allocation in an EPON system. In the proposed EFDBA algorithm, the optical line termination allocates bandwidth to the optical network units in proportion to the fairness weighting counter number associated with their class and queue length. The proposed algorithm provides efficient resource utilization by reducing the unused remaining bandwidth made by idle state optical network units.     

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.     

Elastic ONU-class-based idle time elimination algorithm for Ethernet passive optical networks

To fully exploit the upstream bandwidth in Ethernet passive optical networks (EPONs), dynamic bandwidth allocation (DBA) algorithms need to collect the report messages from all the optical network units (ONUs), incurring an idle time comprising the DBA computation time and the round trip time. Some studies have addressed the problem by using the data transmissions of some or all ONUs (ONU-based) to eliminate the idle time. To satisfy the stringent quality of service (QoS) requirements, for example, to improve the packet delay and jitter for delay sensitive applications without degrading QoS support for other types of applications, some studies have proposed to separate the transmission of higher-class and lower-class traffic within one scheduling cycle. Existing studies on the separable scheduling scenario use the class-based concept, that is, use either the higher-class transmission or the lower-class transmission to eliminate the idle time. By contrast, in this paper, an elastic ONU-class-based idle time elimination algorithm (EOCA) is proposed in which the idle time is eliminated using both the higher-class and lower-class transmissions. The proposed mechanism is elastic in the sense that the lower-class transmission is first considered, and then if insufficient lower-class transmissions exist to eliminate the idle time, the OLT pre-allocates the higher-class transmissions in the following cycle to test whether or not the idle time is eliminated. If the idle time is still not eliminated, the OLT reallocates the bandwidth corresponding to the uneliminated idle time to either the last ONU (uneven method) or all of the ONUs (even method) such that the ONU(s) can early transmit any lower-class packets which arrive during the waiting time. Compared to existing class-based or ONU-based idle time elimination algorithms, the proposed EOCA algorithm performs better. The validity of the proposed EOCA algorithm is demonstrated via detailed simulation experiments.     

Grant-sizing-differentiated bandwidth allocation algorithm for the coexistence of ONUs with and without wavelength tunability in WDM/TDM PONs

Adopting the pay-as-you-grow approach to upgrade passive optical network (PON) facilities by WDM technology insures the smoothness of the upgrade, and also results in the coexistence of wavelength-fixed/tunable optical network units (ONUs) in WDM/TDM PONs. Dynamic bandwidth allocation (DBA) is the key to support such coexistence of heterogeneous ONUs. Thus, DBA is also the key to support the smooth evolution of PONs. To more fairly coordinate the bandwidth allocation among the coexisting heterogeneous ONUs, a differentiated grant sizing (DGS) scheme is proposed. In DGS, not only the fairness between the wavelength-fixed/tunable ONUs but also the fairness between the lightly/heavily loaded ONUs is taken into account. To further carry out load balancing among wavelengths, a grant scheduling scheme is also proposed to cooperate with the grant sizing scheme. In the grant scheduling scheme, a measure of the ONUs’ flexibility is given, and then the least flexible job first rule (LFJF) is adopted for joint wavelength and time-slot assignment. Finally, to demonstrate the effectiveness of the proposed algorithm, a series of comparative analyses is conducted based on simulation experiments.     

Resource Management for Broadband Access over Time-Division Multiplexed Passive Optical Networks

Passive optical networks are a prominent broadband access solution to tackle the "last mile" bottleneck in telecommunications infrastructure. Data transmission over standardized PONs is divided into time slots. Toward the end of PON performance improvement, a critical issue relies on resource management in the upstream transmission from multiple optical network units (ONUs) to the optical line terminal (OLT). This includes resource negotiation between the OLT and the associated ONUs, transmission scheduling, and bandwidth allocation. This article provides an overview of the resource management issues along with the state-of-the-art schemes over time-division multiplexed PONs (TDM-PONs). We categorize the schemes in the literature based on their features, and compare their pros and cons. Moreover, we introduce a unified state space model under which all TDM-PON resource management schemes can be evaluated and analyzed for their system level characteristics. Research directions are also highlighted for future studies.