Dynamic Wavelength Allocation Research Articles

Reducing the lightpath establishing time of FWM-aware dynamic RWA for wavelength-routed optical networks

A dynamic routing and wavelength allocation technique with an interplay between physical and network layer parameters encompassing Four-wave mixing (FWM) awareness and teletraffic performance of wavelength-routed optical networks has previously been proposed for a distributed approach. In this article, we present a fast computational algorithm for our routing and wavelength assignment (RWA) encompassing FWM-induced crosstalk. The objective is to minimize the time of establishing a dynamic lightpath. For this purpose, a precomputed matrix of FWM crosstalk products is used in an adapted version of the FWM-aware dynamic RWA algorithm. The approach is validated through simulations showing improvement up to 30–50% on the provisioning time of lightpaths for different network topologies compared to an online full computational scheme.

Fault-tolerant architecture with dynamic wavelength and bandwidth allocation scheme in WDM-EPON

This study proposes a novel cost-based fault-tolerant WDM-EPON (CFT-WDM-EPON) to provide overall protection. It only equips a backup feeder fiber to recover the system failure. Additionally, a prediction-based fair wavelength and bandwidth allocation (PFWBA) scheme is proposed to enhance the differentiated services for WDM-EPON based on dynamic wavelength allocation (DWA) and prediction-based fair excessive bandwidth reallocation (PFEBR) from our previous work. PFEBR involves an early-DBA mechanism, which improves prediction accuracy by delaying report messages of unstable traffic optical network units (ONUs), and assigns linear estimation credit to predict the arrival of traffic during waiting time. DWA can operate in coordination with an unstable degree list to allocate the available time of wavelength precisely. Simulation results show that the proposed PFWBA scheme outperforms WDM IPACT-ST and DWBA3 in terms of packet delay, jitter performance, throughput, wasted bandwidth, gain ratio of bandwidth, and packet loss.

Dynamic Wavelength Allocation in IP/WDM Metro Access Networks

Increasing demand for bandwidth and proliferation of packet based traffic represent a challenge for today's metro networks, which have been traditionally designed to carry circuit- switched connections. The problem is further complicated by the constraints of cost efficiency and traffic adaptability, imposed by the limited customer base in the metro area. Recently, several architectures have been proposed for future metro access networks. Nearly all of these solutions support dynamic reconfigurability, however reconfiguration policies have not been fully explored yet. In this paper, reconfiguration policies for IP/WDM metro access networks with switching delays are considered, where dynamic reconfiguration corresponds to dynamic allocation of wavelengths to access nodes. Exact formulation of the dynamic wavelength allocation (DWA) problem is developed as a Markov Decision Process (MDP) and a new cost function is proposed to attain both throughput efficiency and fairness. For larger problems, a heuristic approach based on first passage probabilities is developed and shown to yield nearly optimum performance through simulations.

Modelling and performance evaluation of optical burst switched node with deflection routing and dynamic wavelength allocation

In this paper the effect of dynamic wavelength allocation (DWA) scheme implementation to the OBS node performance is investigated. We have developed the mathematical model of an OBS node in order to evaluate the burst blocking probability. It is proposed to allocate a part of total wavelength capacity to be used by deflected bursts only. The results obtained from the model show that if the number of allocated wavelengths is dynamically adapted to the deflected burst traffic intensity, the total blocking probability and deflected burst blocking probability significantly decrease. Concerning to the hardware requirements the implementation of deflection routing needs the limited optical FDL buffer incorporation, to provide the deflected burst with the extra offset time. Also, control logic for burst scheduler needs to be upgraded to perform the dynamic wavelength allocation for deflected bursts. .

Optimal routing and wavelength assignment for survivable multifibre WDM networks

Multifibre optical networks use a bundle of fibres to realize a link between two optical nodes. Such networks can offer significant economic benefits over single-fibre networks because of their ability to relax the restrictions imposed by the wavelength continuity constraint and their potential for handling future growth. This paper introduces two new and efficient integer linear program (ILP) formulations for dynamic wavelength allocation in survivable multifibre wavelength-division multiplexing (WDM) networks, using dedicated and shared protection. Single-fibre networks, both with and without wavelength conversion, can be treated as a special case of these formulations. The new formulations have been tested on several well-known WDM networks, and the results have been compared to those for single-fibre networks. A simple heuristic for dynamic lightpath allocation is also proposed, and its performance is validated by a comparison of the results to optimal solutions generated by the ILPs. Experimental results demonstrate that the new ILPs are feasible for current networks under low-to-medium traffic. For very large or highly congested networks, the heuristic can be used.

A robust fiber-radio architecture for wavelength-division-multiplexing ring-access networks

In this paper, we propose a dynamic wavelength-allocation scheme for wavelength-division multiplexing (WDM) fiber-radio ring-access networks. This scheme can be used to improve the use efficiency of wavelengths at the burst traffic load on the fiber-radio networks. Moreover, a novel bidirectional wavelength add-drop multiplexer (B-WADM) is designed on the backboned ring, which can connect the working and standby sub-rings. It can provide the self-protected function that uses just a few optical devices under link failures. Furthermore, we carry out this study through the simulation and analysis for carrier-to-noise ratio (CNR), channel capacity, and spurious free dynamic range (SFDR) of the fiber-radio network. Finally, we set up an experimental network to demonstrate its performance. The experimental results illustrate that this fiber-radio architecture can provide the robust, flexible, and reliable characteristics for large radio terminals.

Dynamic Wavelength Allocation in Wavelength Division Multiplexing Radio-over-Fiber Access Network

We demonstrate that dynamic wavelength add-drop multiplexing technology based on a fiber Bragg grating array (FBGA) can be used to improve the efficiency of wavelengths at a burst traffic load for wavelength division multiplexing radio-over-fiber (ROF) access networks. Moreover, we also propose an upstream injection-locked longitudinal mode scheme in a remote node to offer a simple ROF interface. Experimental results demonstrate that these technologies can provide robust and reliable characteristics for large radio terminals.

A highly flexible and efficient passive optical network employing dynamic wavelength allocation

A novel and high-performance passive optical network (PON), the SUCCESS-DWA PON, employs dynamic wavelength allocation to provide bandwidth sharing across multiple physical PONs. In the downstream, tunable lasers, an arrayed waveguide grating, and coarse/fine filtering combine to create a flexible new optical access solution. In the upstream, several distributed and centralized schemes are proposed and investigated. The network performance is compared to conventional TDM-PONs under different traffic models, including the self-similar traffic model and the transaction-oriented model. Broadcast support and deployment issues are addressed. The network's excellent scalability can bridge the gap between conventional TDM-PONs and WDM-PONs. The powerful architecture is a promising candidate for next generation optical access networks.

Novel Bidirectional Wavelength Add-Drop Multiplexer in the Wavelength Division Multiplexing Radio-over-Fiber Ring Network

In this paper, we propose and implement a novel bidirectional wavelength add-drop multiplexer (B-WADM) to provide dynamic wavelength allocation employing tunable fiber Bragg gratings (FBGs) and self-protecting function under link failure. This device can be used to improve the efficient use of wavelengths under burst traffic load as well as increase network reliability. The experimental results demonstrate that this B-WADM device can provide robust, flexible and cost-effective characteristics in the wavelength division multiplexing (WDM) fiber-radio ring access network.

SUCCESS-DWA: a highly scalable and cost-effective optical access network

Passive optical networks have been identified as promising access solutions that can open the first-mile bottleneck, bringing gigabits-per-second data rates to end users. Current TDM PONs enjoy low cost by sharing resources in time, but suffer from limited capacity. In the future, WDM technology may be employed to achieve high performance. In this article we introduce a novel PON employing dynamic wavelength allocation to provide bandwidth sharing across multiple physical PONs. Tunable lasers, arrayed waveguide gratings, and coarse/fine filtering combine to create a flexible new optical access solution. The network's excellent scalability can bridge the gap between conventional TDM PONs and WDM PONs. The powerful architecture is a promising candidate for next-generation optical access networks.

Path Selection Methods With Multiple Constraints in Service-Guaranteed WDM Networks

We propose a new approach to constraint-based path selection for dynamic routing and wavelength allocation in optical networks based on WDM. Our approach considers service-specific path quality attributes, such as physical layer impairments, reliability, policy, and traffic conditions, and uses a flooding-based transfer of path information messages from source to destination to find multiple feasible paths. It is fully decentralized, as it uses local network state information. To better understand how multiple constraints impact the efficiency of wavelength routing, and consequently provision the service guarantees, we specifically focus on electronic regenerators that, while being widely considered as the basic building blocks for optical switching nodes, are likely to impose conflicting constraints on routing. For example, electronic regenerators extend the optical reach and could perform wavelength shifting, but also induce impairments, such as delays and operational costs. The question for constraint-based routing is how to account for these conflicting effects. To validate the network modeling, a wide range of networking scenarios are simulated, such as ring, mesh and interconnections of all-optical networks with electronic gateways. For all these scenarios, our approach is shown to efficiently accommodate multiple, conflicting routing metrics related to different services and network architectures.

Analysis of Wavelength-Routed Optical Burst-Switched Network Performance

This paper studies a novel scalable network architecture combining optical burst switching (OBS) with dynamic wavelength allocation to guarantee quality of service (QoS), forming a wavelength-routed optical burst-switched network. All processing and buffering functions are concentrated at the network edge and bursts are assigned to fast tuneable lasers and routed over a bufferless optical transport core using dynamic wavelength assignment. Different burst aggregation mechanisms are evaluated for a range of traffic statistics in terms of delay and packet loss rate. New network performance parameters in an analytical model quantify the advantages of dynamic wavelength allocation. The results define the operational gain achievable with dynamic wavelength assignment compared to quasi-static wavelength routed optical networks.

Analysis of a dynamically wavelength-routed optical burst switched network architecture

The concept of optical burst switching (OBS) aims to allow access to optical bandwidth in dense wavelength division multiplexed (DWDM) networks at fractions of the optical line rate to improve bandwidth utilization efficiency. This paper studies an alternative network architecture combining OBS with dynamic wavelength allocation under fast circuit switching to provide a scalable optical architecture with a guaranteed QoS in the presence of dynamic and bursty traffic loads. In the proposed architecture, all processing and buffering are concentrated at the network edge and bursts are routed over an optical transport core using dynamic wavelength assignment. It is assumed that there are no buffers or wavelength conversion in core nodes and that fast tuneable laser sources are used in the edge routers. This eliminates the forwarding bottleneck of electronic routers in DWDM networks for terabit-per-second throughput and guarantees forwarding with predefined delay at the edge and latency due only to propagation time in the core. The edge burst aggregation mechanisms are evaluated for a range of traffic statistics to identify their impact on the allowable burst lengths, required buffer size and achievable edge delays. Bandwidth utilization and wavelength reuse are introduced as new parameters characterizing the network performance in the case of dynamic wavelength allocation. Based on an analytical model, upper bounds for these parameters are derived to quantify the advantages of wavelength channel reuse, including the influence of the signaling round-trip time required for lightpath reservation. The results allow to quantify the operational gain achievable with fast wavelength switching compared to quasistatic wavelength-routed optical networks and can be applied to the design of future optical network architectures.

Performance of a dynamically wavelength-routed optical burst switched network

This letter describes a novel network architecture combining optical burst switching with dynamic wavelength allocation to achieve a guaranteed quality of service. All processing and buffering functions are concentrated at the network edge and bursts are assigned to fast tuneable lasers and routed over a bufferless optical transport core using dynamic wavelength assignment. Burst aggregation is evaluated for a range of traffic statistics in terms of delay and packet loss rate, and an analytical model is given to quantify the benefits of dynamic wavelength reuse. The results define the operational gain achievable with dynamic wavelength assignment compared to quasi-static wavelength-routed optical networks.

Algorithms for Dynamic Routing in All-Optical Networks

In this paper, we have studied a number of algorithms for routing in all-optical wavelength routed networks. We have considered situations where a lightpath is dynamically created in response to a request for communication and the WDM channels constituting the lightpath are reclaimed when the communication is over. We have looked at two schemes for dynamic wavelength allocation. In the first scheme we have assumed the existence of a central agent to maintain a database of existing lightpaths where the central agent attempts to generate a new lightpath in response to a request for communication. In the second scheme, we attempt to generate a new lightpath using a distributed algorithm. In the first scheme we have exploited the existence of multiple paths between any pair of nodes in a network in order to reduce the blocking probability. For the second scheme, we have proposed three distributed strategies to determine, if possible, a lightpath when there is a request for communication. Each of these strategies have their advantages and disadvantages in terms of the expected blocking probability and the set-up time. We have studied the performances of both the schemes using Monte Carlo simulation.

Worst-case analysis of dynamic wavelength allocation in optical networks

This paper proposes algorithms for allocating wavelengths to connections (lightpaths) in optical wavelength division multiplexed networks, predominantly for ring topologies. A worst-case model is considered, where no blocking of lightpaths is allowed, and there are no assumptions made on the traffic arrival and holding times. The traffic is characterized only by its load L, which is the maximum number of lightpaths that can be present on any link, assuming no blocking. A dynamic traffic model is considered where requests to set up lightpaths arrive over time and, must be accommodated without rerouting existing lightpaths, and lightpaths may be terminated over time as well. For networks without wavelength conversion, we show that at least 0.5Llog/sub 2/N wavelengths are required by any dynamic algorithm for rings of N nodes and present an algorithm that uses at most Llog/sub 2/N+L wavelengths for rings and 2(L-1)log/sub 2/N for trees. We also study the worst-case behavior of the well-known first-fit algorithm, and show that it requires at most 2.52Llog/sub 2/N+5L wavelengths (small variants of these constants are proven as well). When limited wavelength conversion is allowed, we first show how to use expanders to insure no blocking in arbitrary topologies. Then, we present conversion patterns for rings with conversion degree d=2, which require Llog/sub 2/L+4L or 2Llog/sub 2/log/sub 2/L+4L wavelengths, thereby eliminating the dependence (that exists without wavelength conversion) between the number of wavelengths and N. We also consider different traffic models where lightpath setup requests arrive over time, but once set up, lightpaths are never taken down. For this model, the number of wavelengths needed is shown to be only max{0,L-d}+L for a conversion degree of d.