Limited Range Wavelength Conversion Research Articles

Packet Blocking Performance of Cloud Computing Based Optical Data Centers Networks under Contention Resolution Mechanisms

Abstract In data center networks use of optical communication has revolutionized the data transfer mechanism. Optical communication heavily relies on enormous bandwidth of optical fiber. Wavelength Division Multiplexing (WDM) technique can be used for utilization of huge bandwidth. To employ WDM which uses distinct set of wavelengths to carry data wavelength converters are required. However as the tunable range of wavelength converter increases both cost and technological design complexity rises exponentially. Therefore, both Limited Range Wavelength Converter (LRWC) and Full Range Wavelength Converter (FRWC) are considered. However, under higher loading conditions buffering is also required as using wavelength converter (WC) blocking can be reduced significantly. This paper presents comprehensive analysis of blocking performance under various types of wavelengths converters and buffering of contending packets.

Synchronous optical packet switch architecture with tunable single and multi-channels wavelength converters

Abstract In this paper, we propose a bufferless synchronous optical packet switch (OPS) architecture named the Limited-range wavelength conversion with Dynamic Pump-wavelength Selection (LDPS) architecture. LDPS is equipped with a dedicated limited-range wavelength converters (LRWCs, and a shared pool of parametric wavelength converters (PWCs) with dynamic pump-wavelength selection (DPS). The adoption of hybrid conversion types in the proposed architecture aims at improving the packet loss rate (PLR) compared to conventional architecture with single conversion types, while reducing (or at least maintaining) the conversion distance ( d ) of used wavelength converters. Packet contention in the proposed architecture is resolved using the first available algorithm (FAA) and the dynamic pump-wavelength selection algorithm (DPSA). The performance of the proposed architecture is compared to two well-known conventional architectures; namely, the LRWC architecture that uses dedicated LRWCS for each input wavelength, and the DPS architecture that uses a shared pool of dynamic pump-wavelength converters (PWCs). Simulation results show that, for the same value of d , the new architecture reduces the PLR compared to the LRWC architecture by up to 40 % and 99.7 % for traffic loads, 0.5 and 1; respectively. In addition, for d = 1 , the new architecture reduces the PLR compared to the DPS architecture by up to 10 % and 99.3 % for traffic loads, 0.5 and 1; respectively.

Dropping probability reduction in OBS networks: A simple approach

In this paper, we propose and derive a slotted-time model for analyzing the burst blocking probability in Optical Burst Switched (OBS) networks. We evaluated the immediate and delayed signaling reservation schemes. The proposed model compares the performance of both just-in-time (JIT) and just-enough-time (JET) signaling protocols associated with of void/non-void filling link scheduling schemes. It also considers none and limited range wavelength conversions scenarios. Our model is distinguished by being adaptable to different offset-time and burst length distributions. We observed that applying a limited range of wavelength conversion, burst blocking probability is reduced by several orders of magnitudes and yields a better burst delivery ratio compared with full wavelength conversion.

An Optical Packet Switch with Recirculation Limited Range Wavelength Converter Groups and Recirculation Optical Buffers

AbstractThis paper focuses on performances of limited range wavelength converters (LRWCs) in resolving optical packet contentions. An optical packet switch is proposed, which uses recirculation LRWC groups and recirculation fiber delay lines (FDLs) to resolve optical packet contentions. In order to make full use of the LRWCs and the FDLs, a control algorithm is also proposed. Packet loss probability of the proposed switch versus the number of FDLs, the wavelength conversion range, and the number of LRWC groups are evaluated in detail.

A method of segment protection based on p-cycle for dynamic multicast with limited-range wavelength converter in WDM network

In the optical multicast network, node and link failures have very important influence on the network survivability which may lead to multiple destinations cannot receive data. Based on the wavelength layered-graph method, a method of efficiency-score based on heuristic algorithm of pre-configured cycle (p-Cycle) based-segment protection (ESHS) for dynamic multicast with limited-range wavelength conversion was presented in this paper. By finding the multicast tree segment protection, the total available p-Cycles are constructed for the multicast. Then we calculate each p-Cycle efficiency-score, the highest efficient-score p-Cycle is selected as the multicast route protection p-Cycle. The simulation results show that the ESHS can get higher performance than the existing ESHT algorithm, in terms of multicast request blocking probability and wavelength utilization.

An OPS Architecture of Multistage Wavelength Conversion with Shared Limited Range

Architecture is proposed for a Wavelength Division Multiplexed (WDM) optical packet switch equipped with both limited range wavelength converters (LRWCs) and parametric wavelength converters (PWCs). A scheduling algorithm is defined to control optical packet forwarding in a synchronous scenario. Simulation results dictate that significant improvement in performance in terms of packet loss probability when compared with architectures employing LRWCs.

A Fan-out Splitting Scheduling Algorithm with QoS Difference for Optical Multicast Packet Switching Node

Abstract To improve the optical multicast packet switching node throughput performance, the new multicast scheduling algorithms are need urgently to overcome the entire optical multicast packet discard under the model of “one-shot”. A novel QoS difference optical multicast scheduling algorithm, which supporting the fan-out splitting for optical multicast packet switching node with limited range wavelength converter shared per node and without optical random access memory, is presented in the paper. By dropping partly not all the optical multicast packets which are replicated in the blocking multicast source, the proposed algorithm can improve output port utilization. Moreover, the algorithm is improved to provide service QoS difference for priority different traffic application. The simulation results show that the proposed algorithms remarkably improve the throughput of optical multicast packet switch node in comparison with the existing algorithms and support high priority service with high throughput QoS.

Limited Range Wavelength Converter Based PLI-Signal Quality RWA (PLI-SQRWA) Algorithm for Translucent Optical Wavelength Division Multiplexed (WDM) Networks

Limited Range Wavelength Converter Based PLI-Signal Quality RWA (PLI-SQRWA) Algorithm for Translucent Optical Wavelength Division Multiplexed (WDM) Networks

Dynamic Routing and Wavelength Assignment with Backward Reservation in Wavelength-routed Multifiber WDM Networks

In wavelength-routed WDM networks, blocking probability of lightpath establishments is generally high due to coarse granularity and wavelength continuity constraint. Therefore, blocking of lightpath establishments is one of crucial issues which must be resolved. Multifiber environments reduce blocking probability of lightpath establishments because each link consists of multiple fibers and multifiber links can be viewed as limited-range wavelength conversion. Blocking probability can be further reduced by an appropriate routing and wavelength assignment (RWA) scheme. This paper proposes a dynamic RWA scheme using signaling of backward reservation for wavelength-routed multifiber WDM networks. In the proposed scheme, information on link state is collected by signaling of backward reservation along multiple routes between a sender node and a receiver node whenever a new lightpath-setup request arrives. Then the proposed scheme selects a combination of a route and a wavelength at the receiver node based on the collected information in such a way that it avoids the generation of bottleneck links and the depletion of a specific wavelength. Through simulation experiments, we show that the proposed scheme efficiently reduces blocking probability of lightpath establishments in multifiber WDM networks.

An optical packet contention resolution supporting QoS differentiation with LRWC wavelength converters for OPS

The wavelength conversion is regarded as an effective way to resolve the optical packet contention in the wavelength domain for optical packet switching. An optical packet switching node, based on shared-per-node equipped with limited range wavelength converters and parametric wavelength converters (SPN-LP), is designed to further reduce optical packet loss probability. A novel optical packet contention resolution with priority differentiation wavelength scheduling algorithm to support quality of service (QoS) for the SPN-LP architecture is put forward in the article. The simulation results show that proposed optical packet resolution enables a good QoS differentiation, namely the high priority contending optical packet has the sufficient low packet loss probability.

A Novel Contention Resolution Scheme of Hybrid Shared Wavelength Conversion for Optical Packet Switching

Wavelength conversion is an efficient way to improve the optical packet blocking performance for all-optical packet switching networks. The synchronous OPS node architecture, with a hybrid shared wavelength conversion (HSWC) scheme based on shared per output fiber and shared per node wavelength conversion, is put forward to reduce the packet loss probability in this paper. A heuristics is developed into assigning the wavelength channels for packets in the proposed optical nodes. The limited range wavelength converters first available (LFA) algorithm and parametric wavelength converters first available (PFA) algorithm are used to schedule contending optical packets to available wavelength channels. Simulation results show that the hybrid shared wavelength conversion scheme has significant performance improvement in terms of packet loss probability. And the utilization of wavelength converter is greatly improved for OPS node with hybrid shared wavelength conversion scheme. Furthermore, the PFA scheduling algorithm compared with LFA algorithm is validated to improve the wavelength assignment efficiency and reduce the required total wavelength converters for OPS nodes.

Optimal Packet Scheduling in WDM Optical Switches With Output Buffer and Limited Wavelength Conversion

All-optical packet switching is a promising candidate for future high-speed switching. However, due to the absence of optical random access memory, the traditional Virtual Output Queue (VOQ) based input-queued switches are difficult to implement in the optical domain. In this paper we consider output-buffered optical packet switches. We focus on packet scheduling in an output-buffered optical packet switch with limited-range wavelength conversion, aiming at maximizing throughput and minimizing average queuing delay simultaneously. We show that this problem can be converted to a minimum cost maximum network flow problem. To cope with the high complexity of general network flow algorithms, we present an algorithm that can efficiently find an optimal schedule in O(min{NW,BW}) time, where <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">N</i> is the switch size, W is the number of wavelength channels per fiber and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">B</i> is the length of the longest FDL at the output of the switch. The complexity of the new algorithm asymptotically matches the lower bound of the scheduling problem. We also conduct extensive simulations to test the performance of the proposed scheduling algorithm under different traffic models.

MDP-based lightpath establishment for service differentiation in all-optical WDM networks with wavelength conversion capability

In this paper, we propose a service differentiation method for lightpath establishment in all-optical WDM networks. The proposed method derives the optimal lightpath establishment policy for each serve class based on a Markov Decision Process (MDP). The optimal policy considered here is to provide service differentiation for lightpath establishment and to utilize wavelengths effectively. Here, we focus on two cases for wavelength conversion capability; full-range wavelength conversion and limited-range wavelength conversion. For full-range wavelength conversion, the number of lightpaths for each class is considered as a state of MDP. On the other hand, for limited-range wavelength conversion, the service class of lightpath that has been established with each output wavelength is considered as the state. Based on these states, we derive the optimal policy for lightpath establishment. In both cases, we evaluate the performance of the proposed method with simulation. In numerical examples, we show that our proposed method can provide service differentiation and use wavelengths effectively regardless of wavelength conversion capability.

Design of a practical optical cross-connect with limited-range wavelength conversion

The architecture of and the corresponding control algorithm for a devised optical cross-connect, limitedrange wavelength converision wavelength interchangeable cross-connect (L-WIXC), are presented. The performances of L-WIXC including blocking probability, switching time, and throughput are simulated. Cost comparison with wavelength selective cross-connect (WSXC) and WIXC is calculated. Key optical parameters, such as crosstalk, eye diagram, bit error rate, and linear Q factor, are measured and discussed.

Optical Packet Network With Limited-Range Wavelength Conversion: A Novel Formalization of the Optimal Scheduling Problem

In this paper, we consider synchronous optical packet networks formed by switches equipped with a complete set of limited-range wavelength converters. On these networks, we dealt with scheduling algorithm that maximizes the switch throughput. So far, previous literature works have formalized this scheduling problem as the finding of a maximum bipartite matching (MBM) in a convex graph. The MBM formalization has collected various follow-ups, mainly focused on measuring switch-level performance. We revise the MBM formalization by measuring network-level performance. Surprisingly, we find out that when optical switches are cascaded, MBM formalization has two not negligible lacks: (1) a useless degradation of optical signal quality and (2) a tendency of shifting optical packets toward lower wavelengths, thus increasing the occurrence of wavelength contention. To solve these issues, we propose a novel formalization of the scheduling problem as the finding of a MBM with minimum edges weights (MW-MBM). We show that MW-MBM outperforms MBM in terms of both network throughput and optical SNR. Performance evaluation is carried out by means of NS2 simulator that we extend to toughly model optical components (e.g., semiconductor optical amplifier four-wave-mixing wavelength converter). The simulator is provided as open source.

Wavelength allocation in an optical switch with a fiber delay line buffer and limited-range wavelength conversion

This paper presents an approach to evaluate the performance of an optical switch equipped with both limited-range wavelength conversion and Fiber Delay Lines to resolve contention. We propose an analytical model that allows a general behavior for the packet size distribution while the inter-arrival times are assumed to be of Phase-Type and can easily be relaxed to be generally distributed if needed. As the set of reachable wavelengths is a major issue in limited-range wavelength conversion, we first focus on a simple wavelength set configuration that allows the comparison of different policies and their effect on the loss rate of the system. In addition, a linear association between the loss rate of the simple and a more complex set configuration is identified. Using this association and the results from the analytical model, we derive an approximation for the more complex case, where the interactions among adjacent wavelengths play an important role. The approximation works well for different parameter instances and is particularly useful for the mid load case, when simulations become computationally prohibitive.

Fixed point analysis of limited range share per node wavelength conversion in asynchronous optical packet switching systems

In this article, we study an asynchronous optical packet switch equipped with a number of wavelength converters shared per node. The wavelength converters can be full range or circular-type limited range. We use the algorithmic methods devised for Markov chains of block-tridiagonal type in addition to fixed-point iterations to approximately solve this relatively complex system. In our approach, we also take into account the finite number of fiber interfaces using the Engset traffic model rather than the usual Poisson traffic modeling. The proposed analytical method provides an accurate approximation for full range systems for relatively large number of interfaces and for circular-type limited range wavelength conversion systems for which the tuning range is relatively narrow.

Performance evaluation of optical packet switches equipped with heterogeneous wavelength converters

An optical packet switch that shares both limited range and full range wavelength converters for contention resolution is proposed with the aim to guarantee a high conversion cost saving. To optimally dimension the number and the conversion range of the wavelength converters, an analytical model, validated by simulation, is introduced. Numerical results show that the proposed switch architecture allows for a conversion cost saving in the order of 90% with respect to a traditional architecture in which only shared full range wavelength converters are used.

Cost Evaluation of Optical Packet Switches Equipped With Limited-Range and Full-Range Converters for Contention Resolution

Two architectures are proposed for a wavelength-division multiplexed optical packet switch equipped with both limited-range wavelength converters (LRWCs) and shared full-range wavelength converters (FRWCs). The FRWCs are used to overcome the performance degradation in terms of packet loss probability due to the use of LRWCs only. Two different sharing strategies of the FRWCs are considered. In the first architecture, a pool of FRWCs is shared among the arriving packets. In the second one, the sharing is only partial and the packets directed to the same output share a same pool of FRWCs. A probabilistic model is proposed to dimension the number of shared FRWCs so that the same packet loss probability of a switch equipped with only shared FRWCs is guaranteed. After introducing a cost model of the converters depending on the conversion range, we show that the architectures may allow a conversion cost savings on the order of 90%.

Optical Switching Networks With Minimum Number of Limited-Range Wavelength Converters

We study the problem of determining the minimum number of limited-range wavelength converters needed to construct strictly, wide-sense, and rearrangeably nonblocking optical cross-connects for both unicast and multicast traffic patterns. We give the exact formula to compute this number for rearrangeably and wide-sense nonblocking cross-connects under both the unicast and multicast cases. We also give optimal cross-connect constructions with respect to the number of limited-range wavelength converters.