Dynamic bandwidth allocation in heterogeneous WDM EPONs

ABSTRACTIn order to manage Quality of Service (QoS) and energy efficiency in the optical access network, an online Dynamic Bandwidth Allocation (DBA) algorithm with adaptive sleep cycle is presented. This DBA algorithm has the ability to allocate an additional bandwidth to the end user within a single sleep cycle whose duration changes depending on the current buffers occupancy. The purpose of this DBA algorithm is to tune the duration of the sleep cycle depending on the network load in order to provide service to the end user without violating strict QoS requests in all network operating conditions.

An upcoming capable technology named as Next generation Ethernet passive optical network (NG-EPON); to handle enormous bandwidth and effective distribution requirements for prospective Internet based services. Standardization procedures for NG-EPON are in progress. Transmission of data traffic from Optical Network Units (ONUs) towards Optical Line Terminal (OLT) in NG-EPON is carried out through four wavelengths each operating at a data rate of 25Gbps. Dynamic wavelength and bandwidth allocation (DWBA) algorithms are needed for the efficient arbitration of the bandwidth resources between the subscribers. In this paper, we have proposed two different DWBA algorithms for NG-EPON; DWBA-I and DWBA-II. DWBA-I is a Quality-of-Service based algorithm that has been designed to manage the different types of data traffic in NG-EPON. DWBA-I performs better than the different existing DBA algorithms in terms of packet delay, completion time and packet drop ratio. DWBA-II is an algorithm designed to meet the system requirement specifications of NG-EPON and handle traffic requirements of subscribers in a cost effective manner. DWBA-II algorithm is comparatively analyzed and evaluated with First-Fit-DWBA and Modified-IPACT algorithms. Performance of DWBA-II is better on the basis of average delay, grant utilization, completion time and packets drop ratio. Performance of DWBA-I and DWBA-II has been evaluated through simulation results.

In this paper, an (ONU-load and RTTs)-based (OLR) dynamic wavelength and bandwidth allocation (DWBA) algorithm for upstream channel in next-generational Ethernet passive optical network (NG-EPON) is proposed. By proposing adaptive threshold grouping algorithm, the waste of bandwidth resources caused by massive guard timeslots and mismatch between assigned transmission window and frame size is reduced. By adjusting the Optical Network Unit (ONU) scheduling order, the idle time caused by Round-Trip Times (RTTs) is reduced. By proposing joint ONU grouping and RTT scheduling mechanism, load balance among wavelengths is achieved. By proposing a fair allocation scheme, the fairness of bandwidth granting for each ONU is ensured. Finally, by the simulation, the effectiveness of proposed algorithm is demonstrated. The simulation indicates that the rate of bandwidth utilization, the average package delay, the scheduling cycle and the network throughput in the system based on proposed algorithm have better performance.

Passive optical networks (PONs) are thought to be the next step in the development of access networks and providing broadband access in the ¿last mile¿ area. Ethernet PON (EPON) gains the most attention from the researchers as it offers highly flexible and cost effective solution. In this paper we propose two high level scheduler algorithms inside the optical line terminal (OLT) and optical network units (ONU). In the proposed dynamic bandwidth allocation (DBA) algorithm, the OLT allocates the bandwidth to the ONUs in proportion to the weight associated with the excess bandwidth available, while the ONU preferentially allocates its bandwidth to queues with a strict or non strict priority order. The algorithms provide dynamic bandwidth allocation and separate the burden of queue management fairly between the customer and the network. This led to less complicated and more intelligent equipment has been used on the customer's premises. We show the results of simulations to validate the effectiveness of algorithms presented and to provide quality of service (QoS) for triple play real time services in Ethernet passive optical networks (EPONs).

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.

The IEEE initialized a working group to study the 100 Gb/s next-generation passive optical networks (NG-EPON). A key technology adopted by NG-EPON is channel bonding, which enables optical network units (ONUs) to transmit data on multiple wavelength channels simultaneously to achieve higher peak rates. In the upstream, ONUs share the bandwidth of each wavelength in a time-division multiplexing manner, and dynamic wavelength and bandwidth allocation (DWBA) coordinates ONU upstream transmission. If an ONU is granted transmission of data on multiple wavelengths simultaneously, frame reordering will occur due to simultaneous parallel transmission, which needs to be minimized because buffer and extra processing time are needed to restore the original framesequence. For a group of ONUs, DWBA can grant each ONU transmission on either a single wavelength or multiple wavelengths without affecting total bandwidth occupation. Since ONUs transmitting on single wavelength can get rid of frame reordering, different DWBA algorithms can result in different numbers of ONUs suffering frame reordering. In this paper, we investigate the impacts of DWBA algorithms on frame reordering in NG-EPON. A DWBA algorithm for mitigating frame reordering without affecting bandwidth utilization is proposed. The theoretical upper bound of a frame-reordered ONU number with the proposed algorithm is also analyzed. The performances (in terms of frame-reordered ONU number and packet delay) of DWBA algorithms are evaluated through simulations. Simulation results show that the proposed algorithm can mitigate frame reordering efficiently and reduce packet delay as well.

This paper proposes a new scheme for dynamic bandwidth allocation for XG-PON (10-Gbps-capable passive optical network). In the propose scheme, an ONU (optical network unit) does not explicitly report its queue status to an OLT (optical line termination). The OLT monitors the bandwidth usage of each ONU to estimate the queue status of each ONU. The OLT allocates a bandwidth to an ONU when the previous allocated bandwidth was fully used. Also the OLT periodically allocates a probe bandwidth to an ONU to check the queue status of the ONU.

The deployment of new 5G services and future demands for 6G make it necessary to increase the performance of access networks. This challenge has prompted the development of new standardization proposals for Passive Optical access Networks (PONs) that offer greater bandwidth, greater reach and a higher rate of aggregation of users per fiber, being Time- and Wavelength-Division Multiplexing (TWDM) a promising technological solution for increasing the capacity by up to 40 Gbps by using several wavelengths. This solution introduces tunable transceivers into the Optical Network Units (ONUs) for switching from one wavelength to the other, thus addressing the ever-increasing bandwidth demands in residential broadband and mobile fronthaul networks based on Fiber to the Home (FTTH) technology. This adds complexity and sources of inefficiency, such as the laser tuning time (LTT) delay, which is often ignored when evaluating the performance of Dynamic Bandwidth Allocation (DBA) mechanisms. We present a novel DBA algorithm that dynamically handles the allocation of bandwidth and switches the ONUs’ lasers from one wavelength to the other while taking LTT into consideration. To optimize the packet delay, we introduce a scheduling mechanism that follows the Longest Processing Time first (LPT) scheduling discipline, which is implemented over the Interleaved Polling with Adaptive Cycle Time (IPACT) DBA. We also provide quality of service (QoS) differentiation by introducing the Max-Min Weighted Fair Share Queuing principle (WFQ) into the algorithm. The performance of our algorithm is evaluated through simulations against the original IPACT algorithm, which we have extended to support multi-wavelengths. With the introduction of LPT, we obtain an improved performance of up to 73% reduction in queue delay over IPACT while achieving QoS differentiation with WFQ.

Grant management procedure for energy saving TDM-PONs

Chapter 5 - Ranging and Dynamic Bandwidth Allocation

Wavelength division multiplexing/time division multiplexing (WDM/TDM) passive optical networks (PON) is being viewed as a promising solution for delivering multiple services and applications. The hybrid WDM / TDM PON uses the wavelength and bandwidth allocation strategy to control the distribution of the wavelength channels in the uplink direction, so that it can ensure the high bandwidth requirements of multiple Optical Network Units (ONUs) while improving the wavelength resource utilization. Through the investigation of the presented dynamic bandwidth allocation algorithms, these algorithms can't satisfy the requirements of different levels of service very well while adapting to the structural characteristics of mixed WDM / TDM PON system. This paper introduces a novel wavelength and bandwidth allocation algorithm to efficiently utilize the bandwidth and support QoS (Quality of Service) guarantees in WDM/TDM PON. Two priority based polling subcycles are introduced in order to increase system efficiency and improve system performance. The fixed priority polling subcycle and dynamic priority polling subcycle follow different principles to implement wavelength and bandwidth allocation according to the priority of different levels of service. A simulation was conducted to study the performance of the priority based polling in dynamic resource allocation algorithm in WDM/TDM PON. The results show that the performance of delay-sensitive services is greatly improved without degrading QoS guarantees for other services. Compared with the traditional dynamic bandwidth allocation algorithms, this algorithm can meet bandwidth needs of different priority traffic class, achieve low loss rate performance, and ensure real-time of high priority traffic class in terms of overall traffic on the network.

In this paper, a dynamic bandwidth allocation (DBA) algorithm based on differentiated service cycle (DSC) in multiple service (multi-service) hybrid Virtual Passive Optical Network (VPON) is proposed. The DSC algorithm introduces neural network prediction and improves the polling mechanism between Optical Network Unit (ONU) and Optical Line Terminal (OLT). DSC can be applied to multi-service VPON scenarios. By introducing neural network, the problem that traditional prediction methods can only predict one polling cycle service traffic will be solved. By establishing the separation mechanism of report cycle and prediction cycle, the idle time in multi-wavelength VPON is eliminated, and the bandwidth consumption caused by a large number of REPORT messages is reduced. By proposing differentiated service cycle polling mechanism, the transmission delay of high priority service traffic caused by the simultaneous interpreting of multiple services in offline DBA algorithm can be reduced. Finally, by the simulation and analysis, the effectiveness of the proposed model is demonstrated.

Passive optical networks (PONs) require a dynamic bandwidth allocation (DBA) algorithm at the optical line terminal for efficient utilization of upstream bandwidth among the optical network units (ONUs) as per the quality of service requirements for each traffic class defined by PON standardizing bodies. The GigaPON access network (GIANT) was the first International Telecommunication Union compliant DBA algorithm, which is further improved by Immediate Allocation with Colorless Grant (IACG) and Efficient Bandwidth Utilization (EBU) algorithms. However, the polling mechanism of IACG and EBU may not report the true bandwidth demand of ONUs during a service interval. Furthermore, ONU scheduling mechanisms give preference to best effort traffic over the assured traffic during recursive allocation cycles in a service interval, which results in an increase in upstream delays for the assured traffic class. This paper presents an improved bandwidth utilization (IBU) algorithm, which rectifies these deficiencies with a novel polling and scheduling mechanism. Experimental results show that IBU improves the mean of upstream delays of type 2 traffic up to 98%, 93%, and 76% and up to 99%, 92%, and 73% for type 3 traffic compared to the GIANT, IACG, and EBU algorithms, respectively. IBU also shows the least frame loss compared to these state-of-the-art algorithms.

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

The implications of the main components of dynamic bandwidth allocation (DBA) algorithms in ethernet passive optical networks, namely grant scheduling framework, grant sizing, and grant scheduling, have to date been examined in isolation. In contrast, we conduct a comprehensive throughput-delay comparison study of the three main DBA components; whereby, for each of the DBA components, we consider a range of common mechanisms. Our comparison study considers a number of novel combinations of mechanisms for the individual DBA algorithms, such as the double-phase polling (DPP) scheduling framework combined with limited with excess distribution grant sizing, and shortest propagation delay (SPD) first scheduling. We find that this (DPP, Limited with excess, SPD) combination in conjunction with a novel excess sharing mechanism outperforms previously studied DBA algorithms.