Dynamic Bandwidth Assignment Research Articles

Merging engine implementation for intra-frame sharing in multi-tenant virtual passive optical networks

High up-front capital expenditures impede the widespread deployment of passive optical networks (PONs). A multi-tenant solution, in which multiple network operators virtually share PON infrastructure and bandwidth resources, can result in significant cost savings. First, we investigate the viability of virtual PONs, in which virtual network operators share a portion of the upstream bandwidth in a frame. Each PON schedules its frame-level capacity using a dedicated dynamic bandwidth assignment algorithm, resulting in the generation of an independent bandwidth map (BMap). Second, we implement at the optical line terminal a merging engine that combines individual virtual BMaps into a single physical BMap, which is then transmitted to all optical network units. Our novel traffic merging algorithm is capable of consolidating traffic across all transmission containers. We apply this merging engine on top of the 10-Gbit-capable PON module and validate our approach using network simulator 3. The results show that our proposed intra-frame sharing technique, when integrated with our traffic merging algorithm, significantly outperforms the standard inter-frame sharing approach in terms of both latency and packet loss. Furthermore, we observed that best-effort traffic is affected most for all resource constraint scenarios of intra-frame sharing.

Highest Cost First-Based QoS Mapping Scheme for Fiber Wireless Architecture

The combination of a high-speed wireless network with passive optical network technologies has led to the evolution of a modern integrated fiber wireless (FiWi) access network. Compared to broadband wireless networks, the FiWi network offers higher bandwidth with improved reliability and reduced maintenance costs due to the passive nature of passive optical network (PON). Since the quality of service (QoS) is a baseline to deploy high-speed FiWi broadband access networks, therefore, it is essential to analyze and reduce the typical problems (e.g., bandwidth and delay) in the high-speed next-generation networks (NGANs). This study investigates the performance of a fiber wireless architecture where a 10-Gigabit-capable passive optical network (XGPON) and fifth generation of wireless local area network (WLAN) (i.e., IEEE 802.11ac) are integrated. Both technologies take benefits from each other and have pros and cons concerning the QoS demands of subscribers. The proposed work offers a very flexible QoS scheme for the different types of services of 5G WLAN and XGPON with the help of the highest cost first (HCF) algorithm, which leads to reduced upstream delays for delay-sensitive applications. The simulation results show that the HCF algorithm boosts the performance of the dynamic bandwidth assignment (DBA) scheme and results in up to 96.1%, 90.8%, and 55.5% reduced upstream (US) delays for video: VI(T2), background: BK(T3), and best effort: BE(T4) traffic in enhanced-distributed-channel-access (EDCA) mode. Compared to earlier work, the HCF and immediate allocation with the colorless grant (IACG) DBA combination results in the reduction of up to 54.8% and 53.4% mean US delays. This happens because of 50% to 65% better bandwidth assignment by the IACG DBA process due to efficient mapping by the HCF algorithm.

A Survey of Dynamic Bandwidth Assignment Schemes for TDM-Based Passive Optical Network

AbstractIn time division, multiple access (TDMA)-based passive optical network (PONs), a dynamic bandwidth assignment (DBA) is necessary for efficient utilization of the available bandwidth of the upstream link. An efficient DBA scheme can improve the upstream performance of a traffic class of an ONU in two ways. First, it can increase the bandwidth assignment to it by efficiently utilizing the available bandwidth. Secondly, it can reduce the channel and frame idle time by increasing the polling frequency and by assigning extra surplus bandwidth not used by the other ONUs. Many DBA schemes have been reported for both ITU PONs (GPON and XGPON) and IEEE PONs (EPON and 10 G EPON). In this study, we explain the impact of DBA scheme on the upstream performance of PON and then do a thorough survey of both PON standards, categorize the DBA schemes and review them critically. Based on the literature review we also give our opinion on the most suitable DBA scheme for both type PONs on the basis of upstream delays, frame loss and bandwidth utilization efficiency.

Efficient upstream bandwidth utilization with minimum bandwidth waste for time and wavelength division passive optical network

For an efficient bandwidth management among the optical network units in the upstream link of a passive optical network (PON), it is necessary to use a dynamic bandwidth assignment (DBA) scheme at the optical line terminal. This is really helpful for the PON service providers in meeting their delay guarantees and bandwidth commitments as per the service level agreements (SLAs). It also enables them to increase their revenue by accommodating more users in the available bandwidth. This study investigates the weaknesses of existing ITU compliant DBA schemes. The study reviews the earlier reported work on DBA with a focus on the ITU compliant schemes. The study argues that the existing reported schemes suffer from a few deficiencies such as inefficient bandwidth reporting in their polling process and borrow refund problem while utilizing the unused bandwidth (UBW). To overcome these shortcomings, an efficient bandwidth assignment (EBA) scheme is presented. Extensive simulations are performed to test the performance of the proposed scheme with both Poisson distributed and self-similar traffic patterns. The results show that the EBA scheme efficiently utilizes the UBW and RSB leading up to 80%, 90%, 60% and 99% lesser upstream delays with Poisson traffic pattern and up to 80%, 77% and 99% lesser delay with self-similar traffic compared to GREAL, IACG, and GIANT schemes. However, compared to EBU it shows up to 12% higher delay values due to reduction of its RSB share because of the utilization of UBW by T3 and T4. Overall, compared to other schemes, EBA exhibits least bandwidth waste per cycle resulting in least US delays. The bandwidth waste in EBA is also minimized due to least unallocated bandwidth ratio and frame loss rate. The maximum US delays of all traffic classes for EBA remains under 2 ms for T2 and T3 till the traffic load of 1 and till the load of 0.8 for T4 traffic class.

Attack-Aware Dynamic Upstream Bandwidth Assignment Scheme for Passive Optical Network

Abstract Network security is an important component of today’s networks to combat the security attacks. The passive optical network (PON) works at the medium access layer (MAC). A distributed denial of service (DDOS) attack may be launched from the network and transport layers of an Optical Network unit (ONU). Although there are various security techniques to mitigate its impact, however, these techniques cannot mitigate the impact on the MAC Layer of the PON and can cause an ONU to continuously drain too much bandwidth. This will result in reduced bandwidth availability to other ONUs and, thus, causing an increase in US delays and delay variance. In this work we argue that the impact of a DDOS attack can be mitigated by improving the Dynamic bandwidth assignment (DBA) scheme which is used in PON to manage the US bandwidth at the optical line terminal (OLT). The present DBA schemes do not have the capability to combat a security attack. Thus, this study, uses a machine learning approach to learn the ONU traffic demand patterns and presents a security aware DBA (SA-DBA) scheme that detects a rogue (attacker) ONU from its traffic demand pattern and limits its illegitimate bandwidth demand and only allows it the bandwidth assignment to it as per the agreed service level agreement (SLA). The simulation results show that the SA-DBA scheme results in up to 53%, 55% and 90% reduced US delays and up to 84%, 76% and 95% reduced US delay variance of T2, T3 and T4 traffic classes compared to existing insecure DBA schemes.

Machine learning based dynamic load balancing DWBA scheme for TWDM PON

Abstract The time and wavelength division passive optical network (TWDM PON) provides broadband services to residential, commercial and industrial users at four different wavelengths. Typically, the industrial users are active in day time and inactive in evening while the residential customers are expected to have quite opposite behavior. This disparity will create an imbalance of traffic load on the wavelengths of TWDM PON. Like IEEE PONs, a load proportional wavelength activation approach cannot work for ITU compliant PONs as ITU standard requires all the wavelengths to be active simultaneously. Moreover, the ONUs cannot be assigned bandwidth on two different wavelengths simultaneously and the migration of an ONU from one wavelength to another causes a tuning delay due to a handshaking mechanism between the OLT and the ONU. Therefore, this work proposes an efficient load balancing dynamic wavelength and bandwidth assignment (LB-DWBA) scheme for TWDM PON to maintain a balanced load between the heavily loaded and least loaded ONUs using a regression based machine learning approach. Simulation results show that LB-DWBA scheme not only reduces the traffic load of heavily loaded wavelengths but also minimizes the bandwidth waste from the excess assigned bandwidth assigned to ONUs using type-5 (T5) traffic class. Overall, the LB-DWBA scheme reduces the average upstream delays of type-2 (T2), type-3 (T3) and type-4 (T4) by 18.9%, 24% and 43% respectively.

Disaggregation of Time-Critical Applications in Flexible Access System Architecture [Invited

To quickly meet the diverse requirements imposed by emerging new services on optical access networks, we recently proposed the new concept of flexible access system architecture (FASA), which features the disaggregation of time-critical applications. This paper introduces our activities on FASA along with related technical trends. As our key ongoing challenge, the modularization of the dynamic bandwidth assignment function in a passive optical network is reviewed, and information on its use cases, approach, and sequences is given. Furthermore, a reference hardware implementation of FASA for mobile service is described.

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.

Comprehensive bandwidth utilization and polling mechanism for XGPON

SummaryFor an efficient utilization of the upstream bandwidth in passive optical network, a dynamic bandwidth assignment mechanism is necessary as it helps the service providers in provisioning of bandwidth to users according to the service level agreements. The scheduling mechanism of existing schemes, immediate allocation with colorless grant and efficient bandwidth utilization (EBU), does not assign the surplus bandwidth to a specific traffic class and only divides it equally among the optical network units (ONUs). This results in overreporting of ONU bandwidth demand to the optical line terminal and causes wastage of bandwidth and increase in delays at high traffic loads. Moreover, the EBU also assigns the unused bandwidth of lightly loaded ONU queues to the overloaded queues through an Update operation. This Update operation has a flaw that it borrows the extra bandwidth to a queue in the current service interval, if the queue report is higher than its service level agreement and refunds in next service interval. This borrow‐refund operation causes reduced bandwidth allocation to the lower priority classes and increases their delay and frame loss. This study improves both these weaknesses. The simulation results show that the proposed scheme uses bandwidth efficiently and reduces mean upstream delay of type‐2 (T2) traffic class by 38% and type‐3 (T3) up to 150% compared to immediate allocation with colorless grant at a cost of up to 10% higher delay for T2. However, T4 performance improves by 400% compared to EBU with slight increase in delay for T2 traffic class. Overall, it shows a balanced performance for all the traffic classes and minimizes the bandwidth waste per cycle as well as the frame loss rate.

An energy efficient cyclic sleep control framework for ITU PONs

Cyclic Sleep Mode (CSM) is a widely studied and standard energy conservation technique for Passive Optical Networks (PONs). The energy savings provided by CSM increase with longer Asleep and shorter SleepAware state periods. However, this also leads to increased communication delays. Moreover, too short SleepAware time may degrade dynamic bandwidth assignment (DBA) performance and even may cause delay of urgent PLOAM messages from OLT. Neither CSM standards nor existing studies provide any detailed framework to configure CSM performance and control parameters in accordance to the target delays. Another limitation of existing studies is their assumption of a single traffic class during sleep mode analysis. They do not consider the impact of CSM on Type-1 (T1) to Type-4 (T4) traffic classes defined by International Telecommunication Union (ITU). Most of these studies also neglect the role of DBA by considering a fixed bandwidth assignment. However, upstream delays critically depend on the DBA performance and its impact should not be ignored during CSM studies. Therefore, this study presents an Efficient Cyclic Sleep (ECS) framework to configure all CSM parameters and timers with optimum values in the presence of all traffic classes and DBA scheme. The proposed scheme maximizes the energy savings even at very high traffic loads while satisfying the target average delay limit of 56ms for both US and DS links. A sleep buffer approach is used to configure the Local Wake Up Indication (LWI) events and all CSM control timers at the OLT and ONU. The proposed scheme is compared with two other reported schemes. Simulation results show up to 84.1% energy savings at very low traffic loads and 43% savings at 80% network traffic load (equal to traffic arrival rate of 550Mbps per ONU). The delay variance results for both US and DS also remain under 1ms.

Evaluating Dynamic Bandwidth Allocation of Virtualized Passive Optical Networks Over Mobile Traffic Traces

Deploying passive optical networks (PONs) requires substantial investments, despite their savings compared to point-to-point solutions. Consequently, network-sharing business models where a network operator leases its system to other service providers, are being investigated and deployed in some countries. These types of schemes require that operators are either physically isolated or have reserved capacity so that they can operate independently. We present the benefits that our group-assured dynamic bandwidth assignment (DBA) algorithm brings to access network virtualization. This algorithm enables operators to take advantage of the benefits of statistical multiplexing, while maintaining isolation from other operators in the PON. To test our algorithm, we considered the particular use case of a mobile system backhauling multiple base stations through a PON. Our tests, operated over real mobile traffic traces, show increased quality of service with a reduction of backhaul capacity of >30% compared to a legacy DBA algorithm.

Optical network unit‐based traffic prediction for Ethernet passive optical networks

The authors propose a novel traffic prediction method for the minimisation of packet delay in Ethernet passive optical networks. The method relies on traffic monitoring at the optical network units (ONUs) and utilises readily available traffic information to predict the accumulated burst size of each respective ONU in the following cycle. They demonstrate that a significant delay enhancement can be accomplished by reporting the predicted, rather than the current, burst size to the optical line terminal (OLT). The author's simulation results show that a delay improvement of over 25% can be expected by the proposed method without modifying the well-established interleaved polling scheme with adaptive cycle time dynamic bandwidth assignment scheme at the OLT.

Editoral: Special Issue on Photonic and RF Communications Systems

Editoral: Special Issue on Photonic and RF Communications Systems

Network virtualization based seamless networking scheme for fiber-wireless (FiWi) networks

In order to reduce cost and complexity, fiber-wireless (FiWi) networks emerge, combining the huge amount of available bandwidth of fiber networks and the flexibility, mobility of wireless networks. However, there is still a long way to go before taking fiber and wireless systems as fully integrated networks. In this paper, we propose a network virtualization based seamless networking scheme for FiWi networks, including hierarchical model, service model, service implementation and dynamic bandwidth assignment (DBA). Then, we evaluate the performance changes after network virtualization is introduced. Throughput for nodes, bandwidth for links and overheads leaded by network virtualization are analyzed. The performance of our proposed networking scheme is evaluated by simulation and real implementations, respectively. The results show that, compared to traditional networking scheme, our scheme has a better performance.

Comprehensive Performance Assessment of Bipartition Upstream Bandwidth Assignment Schemes in GPON

With the emerging diversified services, the gigabit-capable passive optical network (GPON) has emerged as one of the most important technologies to support the next-generation broadband access networks. Dynamic bandwidth assignment (DBA) avoids transmission collision in the upstream direction and improves the efficiency of the PON upstream bandwidth by dynamically adjusting the bandwidth among the optical network units (ONUs) in response to the ONU burst traffic requirement. Instead of using GATE and REPORT control messages in Ethernet PON DBA, the buffer REPORT/GRANT message is embedded into a GPON encapsulation mode (GEM)/GPON transmission convergence (GTC) frame, and all ONUs are essentially polled simultaneously within a GEM/GTC frame in GPON DBA. This paper proposes a bipartition DBA (BI-DBA) mechanism in GPON that divides the transmission cycle time into two groups and adjusts the bandwidth dynamically. Two cases are considered: in the first case, there is a first group for high priorities T-CONT 1 and T-CONT 2 and a second group for low priorities T-CONT 3 and T-CONT 4, called class based scheduling (CBDBA). In the second case, the first and the second group are created according to the number of ONUs, called group based scheduling (GBDBA). Moreover, the T-CONT 2 traffic has a prediction mechanism and recycles the remaining unused bandwidth for the low-priority T-CONTs. The GBDBA has better system performances in terms of the average bandwidth utilization, packet latency, and drop probability; on the other hand, the CBDBA has better packet delay performance when the proportion of T-CONT 1 traffic is higher and has better fairness performance.

Traffic-prediction-assisted dynamic bandwidth assignment for hybrid optical wireless networks

Hybrid optical-wireless networks provide the inexpensive broadband bandwidth, vital for modern applications, as well as mobility, and scalability required for an access network. However, in order to provide satisfactory Quality of Service (QoS) on such a non-homogeneous network, innovative designs are required. This paper proposes a novel scheduling mechanism to significantly improve the delay guarantee, while maintaining high-level throughput, by predicting the incoming traffic to optical network units (ONU). The proposed scheduler managed to exploit the available information in hybrid optical-wireless networks, to enhance the ONU scheduler. This results in accurate prediction of incoming traffic, which leads to intelligent and traffic-aware, scheduling and dynamic bandwidth assignment (DBA). Based on the proposed architecture, two DBA algorithms are proposed and their performance is evaluated by extensive simulations. Moreover, the maximum throughput of such network is analyzed. The results show that by using the proposed algorithms, the delay bound of delay-sensitive traffic classes can be decreased by a factor of two, without any adverse effect on the throughput.

Local-Traffic-Redirection-Based Dynamic Bandwidth Assignment Scheme for EPON With Active Forwarding Remote Repeater Node

The Ethernet passive optical network (EPON) has been considered as one of the most suitable next-generation optical access solutions. As a time-division multiplexing PON (TDM-PON) technology, the transmission media of EPON is shared among multiple users. Therefore, medium access control (MAC) protocol plays an important role in enabling a dynamic bandwidth assignment (DBA) mechanism that provides efficient and fair utilization of the PON resources. However, the DBA mechanism implemented in products is open for vendor customization. In this paper, we propose a novel local-traffic-prediction-based dynamic bandwidth assignment (LT-DBA) mechanism applicable in a remote-repeater-based EPON system with active forwarding. The LT-DBA aims to improve the bandwidth utilization and average packet delay performance of EPON in upstream transmission in comparison to conventional bandwidth assignment techniques such as static bandwidth assignment (SBA) and the interleaved polling algorithm (IPACT), leading to a more efficient PON system.

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.

Offset-Based Scheduling With Flexible Intervals for Evolving GPON Networks

This paper introduces a novel framework for dynamic bandwidth assignment (DBA) in gigabit passive optical networks (GPONs) employing the Offset-Based Scheduling with Flexible Intervals (OSFI) concept in order to achieve distribution of bandwidth in such networks ensuring not only high system utilization but also clean-cut quality of service (QoS) differentiation based on the individual demands of user services. In addition, ways to enhance efficiency in the case of next generation long-reach GPONs are discussed. A thorough description of the proposed mechanisms is provided, while the improved system performance is verified using simulations.

Suitability of DAMA and Contention-Based Satellite Access Schemes for TCP Traffic in Mobile DVB-RCS

The problem of optimizing access and bandwidth sharing among transmission control protocol (TCP) connections in the mobile digital video broadcasting return channel via satellite (DVB-RCS) is tackled in this paper. After sketching the general system architecture, we explicitly deal with the dynamic assignment of bandwidth to TCP connections on the return link, which is accomplished by a network control center (NCC) placed onboard the satellite. Mobile users access the satellite in multifrequency time-division multiple access (MF-TDMA), whereas they receive data from the NCC in time-division multiplexing (TDM). Two different techniques, based on deterministic and random access, are compared in terms of bandwidth usage and average completion time per connection, when the mobile user acts as both server and client. In the server case, to increase the TCP throughput, both packet-level forward error correction (FEC) on data sent by mobile users and a duplicated and delayed acknowledgment technique for TCP acknowledgment traffic from the NCC to the mobile users are applied. An analysis of the packet losses and a simulation campaign of file transfers by employing a realistic channel model has been carried out. The results of the analysis show the convenience of adopting a technique, in addition to the optimal data redundancy in different cases, such as the server or client role of users, their willingness to pay, the file size, and the environment type.