Optical Mesh Research Articles

A survey of survivability in multi-domain optical networks

Network survivability is becoming an important issue and a topical subject in WDM optical mesh networks. Many works have studied network survivability. However, few works have focused on survivability in multi-domain optical networks. This paper reviews the literature on survivability against failures in multi-domain optical networks. The main objective of this study is to evaluate and analyze existing solutions and to compare their performance in terms of different criteria: resource utilization, ratio of rejected connections and recovery time.

$1+{\rm N}$ Network Protection for Mesh Networks: Network Coding-Based Protection Using p-Cycles

p-Cycles have been proposed for preprovisioned 1 + N protection in optical mesh networks. Although the protection circuits are preconfigured, the detection of failures and the rerouting of traffic can be a time consuming operation. Another survivable mode of operation is the 1 + 1 protection mode, in which a signal is transmitted to the destination on two link disjoint circuits, hence recovery from failures is expeditious. However, this requires a large number of protection circuits. In this paper, we introduce a new concept in protection: 1 + N protection, in which a p-Cycle, similar to FIPP p-cycles, can be used to protect a number of bidirectional connections, which are mutually link disjoint, and also link disjoint from all links of the p-Cycle. However, data units from different circuits are combined using network coding, which can be implemented in a number of technologies, such as Next Generation SONET (NGS), MPLS/GMPLS, or IP-over-WDM. The maximum outage time under this protection scheme can be limited to no more than the p-Cycle propagation delay. It is also shown how to implement a hybrid 1 + N and 1 + N protection scheme, in which on-cycle links are protected using 1 + N protection, while straddling links, or paths, are protected using 1 + N protection. Extensions of this technique to protect multipoint connections are also introduced. A performance study based on optimal formulations of the 1 + 1, 1 + N and the hybrid scheme is introduced. Although 1 + N speed of recovery is comparable to that of 1 + N protection, numerical results for small networks indicate that 1 + N is about 30% more efficient than 1 + 1 protection, in terms of the amount of protection resources, especially as the network graph density increases.

Configuration of an optical waveguide interconnect mesh network based on EOPCB

An optical waveguide interconnect mesh network scheme for parallel multiprocessor systems based on an electro-optical printed circuit board (EOPCB) with multimode polymer waveguide is proposed. The system consists of 22 processor element chips interconnected in a mesh network configuration. An additional layer with optical waveguide structure is embedded in a conventional printed circuit board to construct the EOPCB. Vertical cavity surface emitting laser (VCSEL)/positive intrinsic-negative (PIN) arrays are applied as the optical transmitters/receivers. Three 112 VCSEL/PIN parallel optical transmitting/receiving modules are used to provide 32 input/output optical channels required by the 22 chip-to-chip optical mesh interconnect system. The data rate in each optical channel is 3.125 Gbps and thus 10 Gbps parallel optical interconnect link for each direction of a chip is obtained. The optical signals from a processor element chip can be transmitted to another chip through optical waveguide interconnect embedded in the board. Thus the optical interconnect mesh network for parallel multiprocessor system can be implemented.

A unified framework for shared protection schemes in optical mesh network

While the advantages of p-cycles and FIPP p-cycles are well established, there has been no systematic analysis of how much bandwidth they consume in comparison with the classical shared link and path protection schemes. It was recently observed that, even enumerating a huge number of cycles, is not necessarily a guarantee for obtaining good quality solutions with the ILP models if tools for large scale programming are not used. We propose to investigate the bandwidth protection costs of p-cycles and FIPP p-cycles in comparison with those of shared link and path protection by applying the column generation technique to solve relaxed LP models for the four protection schemes, and then solving the resulting ILP models. Provably near-optimal solutions allow us to perform accurate quantitative comparisons on real-world networks.

Survivable scheduled service provisioning in WDM optical networks with iterative routing

Survivable service provisioning design has emerged as one of the most important issues in communication networks in recent years. In this work, we study survivable service provisioning with shared protection under a scheduled traffic model in wavelength convertible WDM optical mesh networks. In this model, a set of demands is given, and the setup time and teardown time of a demand are known in advance. Based on different protection schemes used, this problem has been formulated as integer linear programs with different optimization objectives and constraints in our previous work. The problem is N P -hard. We therefore study time efficient heuristic solutions to the problem. Our approach is based on an iterative survivable routing (ISR) scheme that utilizes a capacity provision matrix and processes demands sequentially using different demand scheduling policies. The objective is to minimize the total network resources (e.g., number of wavelength-links) used by working paths and protection paths of a given set of demands while 100% restorability is guaranteed against any single failure. The proposed algorithm is evaluated against solutions obtained by integer linear programming. Our simulation results indicate that the proposed ISR algorithm is extremely time efficient while achieving excellent performance in terms of total network resources used. The impact of demand scheduling policies on the ISR algorithm is also studied.

Design and performance of randomized schedules for time-domain wavelength interleaved networks

Time-domain wavelength interleaved networking (TWIN) is an optical mesh network architecture in which each edge node has one (or more) tunable lasers to transmit fixed-length bursts to various destinations and one (or more) burst-mode receivers capable of decoding each burst intended to it. In this architecture, the interior nodes route each burst independently and passively based on the wavelength of the burst. Network scheduling is thus a critical component that arbitrates burst transmissions from sources to destinations so that conflicts are either avoided or minimized, and wavelength division multiplexing (WDM) transport capacity is efficiently utilized. However, in access or metro networks, which lend themselves naturally to the TWIN mesh architecture, centralized network scheduling would be cumbersome. We consider a distributed mechanism that performs scheduling of bursts to further simplify TWIN mesh architectures. In one realization, each source randomly assigns non-overlapping time slots within a frame for its transmissions. In another realization, each destination grants random but non-overlapping time slots to sources for transmissions. In neither scheme is there any coordination across sources and destinations. We present an analytical formulation of these schemes and investigate their performance under two broad types of traffic: dynamic traffic and semi-dynamic traffic. For dynamic traffic, the analytical results show that for offered load close to 100 percent of capacity, there is 63 percent efficiency for the destination-based mechanism and 37 percent efficiency for the source-based mechanism. When end-to-end demands are semi dynamic, we show through simulations that the destination-based random schedules can achieve over 90 percent efficiency even for offered loads close to 100 percent. These results indicate that the proposed distributed schemes, though exceedingly simple, provide acceptable efficiency comparable to that realized by computation-intensive centralized schedulers irrespective of propagation delays and applicable to any kind of network traffic.

Lightpath- and Light-Tree-Based Groupcast Routing and Wavelength Assignment in Mesh Optical Networks

With wide deployment of optical transport networks and the emergence of bandwidth-intensive applications, the idea of multicasts and groupcasts in optical networks stems from the ability to set up optical point-to-multipoint (multicast) and multipoint-to-multipoint (groupcast) sessions in wavelength-routed networks. As the technology for intelligent optical networks grows, optical groupcast applications (such as grid computing, distributed interactive simulations, multimedia-rich interactive services, virtual private network services, personal–customized content authoring services, and Ethernet LAN services) will become widely popular. In this paper we introduce the concept of groupcast routing and wavelength assignment (GC-RWA) and evaluate the performance of GC-RWA for light-forests corresponding to the groupcast sessions, when these light-forests are composed of lightpaths and light-trees.

Planar-Subgraph and Eulerian-Based Techniques for Determining Protection Ring Covers in Mesh Optical Networks

Ring architectures have been widely used by telecommunications carriers for the deployment of networks based on synchronous optical network (SONET) and wavelength division multiplexing (WDM). These architectures have several attractive properties that make them desirable for a large number of applications. Even though arbitrary mesh network architectures provide additional degrees of freedom and are more flexible than rings, in a number of applications there are advantages to decomposing the mesh topologies into a set of rings that cover the network. One of the primary uses of ring covers is to provide survivability against link and node failures. This paper investigates novel approaches for establishing ring covers in optical networks with mesh topologies, while minimizing the length of the ring covers.

Wavelength reservation scheme with switch fabric status in distributed mesh optical networks

A new wavelength reservation scheme is proposed to mitigate the connection setup time and minimize the reconfiguration times of optical cross-connects (OXCs) for WDM optical networks in this study. In this scheme, we consider the reconfiguration information of switch fabrics in the signaling protocol, which is designated as the signaling with switch fabric status (SWFS). Distributed reservation algorithms will reserve the wavelength with minimum of reconfiguration times of OXCs along the route. Simulation results indicate that the proposed schemes with switch fabrics status have shorter setup time, lower switching ratio as well as better blocking performance than those of the traditional classic schemes. Moreover, the proposed schemes with SWFS significantly reduce the number of switch fabrics that need to be reconfigured.

A dynamic impairment-aware networking solution for transparent mesh optical networks

Core networks of the future will have a translucent and eventually transparent optical structure. Ultra-high-speed end-to-end connectivity with high quality of service and high reliability will be realized through the exploitation of optimized protocols and lightpath routing algorithms. These algorithms will complement a flexible control and management plane integrated in the proposed solution. Physical layer impairments and optical performance are monitored and incorporated in impairment-aware lightpath routing algorithms. These algorithms will be integrated into a novel dynamic network planning tool that will consider dynamic traffic characteristics, a reconfigurable optical layer, and varying physical impairment and component characteristics. The network planning tool along with extended control planes will make it possible to realize the vision of optical transparency. This article presents a novel framework that addresses dynamic cross-layer network planning and optimization while considering the development of a future transport network infrastructure.

On segment-shared protection for dynamic connections in multi-domain optical mesh networks

We propose a novel protection algorithm called Enhanced Local Segment-Shared Protection (ELSSP) for dynamic connections in multi-domain optical mesh networks. ELSSP assigns rational link-cost on the virtual topology when calculating the primary path, and provides segment-shared protection in the passing domains of the primary path. Simulation results show the good network performance of ELSSP.

Use of a genetic algorithm with a penalty strategy to optimize optical communication window mesh

A constrained nonlinear programming model was extracted from an optimum design of optical communication window mesh with optical transmittance chosen as the objective function, and a shielding effectiveness requirement as the nonlinear constraint. The globally optimized solution of the constrained nonlinear programming model was solved using a genetic algorithm with a penalty strategy. The globally optimized design was then verified by comparing the measurements of window mesh samples with the optimized values. The experimental results and optimized tracing figures of the genetic algorithm indicate that the presented optimization method based on the genetic algorithm is accurate and efficient. Therefore, it can be concluded that a genetic algorithm can be used to optimize optical communication window mesh.

Improvement of Metropolitan Wireless Networking Using Wireless Optical Mesh Networks

Improvement of Metropolitan Wireless Networking Using Wireless Optical Mesh Networks

Voice Operated Guidance Systems for Vision Impaired People: Investigating a User-Centered Open Source Model

Many wireless networking systems were established to manipulate metropolitan networks in order to provide internet, voice, data, video and TV services in large cities. Two major systems were used for such services; Local Multipoint Distribution Service (LMDS) and Multi-channel Multipoint Distribution Service (MMDS). Both of these systems are fixed broadband access networks and both have problems in the cost, speed, coverage area and last-mile bottleneck, especially when the network size is increased. Deploying a new technology of a Wireless Optical Mesh network (WOMN) which uses wireless optical communications between nodes can overcome these problems and can provide more bandwidth, an interference-free network, a frequency-free network, and more effective applications that require a real time responding like video surveillance. We investigate the WOMN against LMDS and MMDS to show that WOMN is better than both LMDS and MMDS in commercial, geographical coverage, and real time applicability. We will also investigate the challenges to deploy the new technique for local and metropolitan networks between different city buildings. Furthermore, we will show that we can have a better performance by including microwave weather detection mechanism through the estimation of the fog and rain presence under several different conditions. In addition, combining the Free Space Optic (FSO) technology with the 60GHz radio waves can increase the WOMN link availability, thus providing an alternative communication way and increasing the distance between wireless optical devices. This strategy can avoid the effect of fog and snow on wireless signal since they do not have effect on the propagation of 60GHz radio waves. The WOMN link can be engineered by adjusting antenna size, choosing a high-power option, and changing the microwave frequency.

Capacity-efficient strategy for 100% dual-failure restorability in optical mesh networks utilising reconfigurable p-cycles and a forcer filling concept

The problem of achieving 100% dual-failure restorability utilising reconfigurable p-cycle mechanisms has been investigated via three different p-cycle mechanisms derived from the integer linear programming model; complete-repair (CRP), incremental-repair (IRP) and dynamic-repair (DRP). An enhanced 100% dual-failure restoration mechanism is proposed, designated as modified DRP with forcer filling concept (MDRP/wFF), in which network protection is achieved using only reconfigurable span-protecting p-cycles without the addition of path-segment-protecting p-cycles as in DRP. As a result, the overhead incurred in differentiating between the two p-cycles becomes non-existent upon network restoration. Furthermore, a FF concept is employed to reduce the amount of spare capacity required to restore the network. The performance of the MDRP/wFF scheme was benchmarked against that of the CRP, IRP and DRP mechanisms. The simulation results show that MDRP/wFF achieves a performance tradeoff among CRP, IRP and DRP in terms of its spare capacity requirements and average number of reconfigured spans during the reconfiguration process [designated as average reconfiguration overhead (ARO)]. The MDRP/wFF scheme was found to have a lower spare capacity requirement but incurs some additional ARO compared with DRP.

Book reviews (2 books reviewed)

The following two books are reviewed in this issue: Network Management: Accounting and Performance Strategies (Claise, B. and Wolter, R.; 2007) and Path Routing in Mesh Optical Networks (Bouillet, E. et al.; 2007).

An improved shared-path protection algorithm for double-link failures in meshed WDM optical networks

In this paper, we investigate survivability in wavelength division multiplexing (WDM) mesh networks and propose a new algorithm called improved shared-path protection (ISPP) to completely tolerate the double-link failures. Compared with previous algorithms for protecting double-link failures, i.e., shared-path protection (SPP) and shared-link protection (SLP), the advantage of ISPP is to allow primary paths and backup paths to share the mixed wavelength-links based on the proposed new rules in which some primary wavelength-links can be changed to mixed wavelength-links, which can be shared by primary paths and backup paths. In addition, some mixed wavelength-links also can be shared by different backup paths for saving resources. Simulation results show that ISPP algorithm performs better in resource utilization ratio and blocking probability than conventional SPP and SLP algorithms.

Optimization of optical communication window mesh through full-wave analysis of periodic mesh

In order to develop an optical communication window mesh with good optical transmittance and shielding effectiveness at the same time, models were established for the shielding effectiveness and optical transmittance of optical communication window mesh, verified through experiments, and used to run full-wave analyses. The effect of period and linewidth of mesh on the shielding effectiveness and optical transmittance of optical communication window mesh was investigated through simulation. Simulation results indicated that better optical transmittance can be achieved using optical communication window mesh with high porosity and finer linewidth while the given shielding effectiveness requirement is satisfied.

Novel P-Cycle protection strategy for asymmetric traffic in mesh optical networks

A novel prefigured-cycle (P-Cycle) algorithm was proposed to improve the protection success ratio for asymmetric traffic in mesh optical networks. The proposed algorithm was simulated in a Pan-European COST239 network environment under an asymmetric dynamic traffic model. The experimental results show that the proposed algorithm has lower capacity redundancy and higher utilization rate of configured resources than traditional P-Cycle methods. Network performance can be improved when implementing this algorithm under single-link failure circumstances. The system behavior is analyzed under different traffic volumes and the configuration strategy is also investigated for the heavyload and light-load networks respectively.

Design and analysis of partial protection mechanisms in groomed optical WDM mesh networks

We consider the problem of survivable network design in traffic-groomed optical WDM mesh networks that support subwavelength capacity connections. In typical survivable network designs, individual sessions are provided either full protection or no protection. We consider a quality of protection (QoP) framework where a connection is provided partial protection, i.e., when a link failure occurs on the primary path, the protection bandwidth provided on the backup path is less than or equal to the primary bandwidth. Each connection request specifies the primary bandwidth and a minimum backup bandwidth required. The network will guarantee at least the minimum backup bandwidth and, if capacity is available, higher backup bandwidth up to the primary path's bandwidth. The advantage of such a model is that it can reduce backup capacity requirements based on connection needs leading to lower blocking probability and lower network costs. We consider two scenarios: (i) a network with static traffic that is designed using an integer linear program (ILP) formulation and (ii) a network with dynamic traffic for which we present a heuristic connection admission control algorithm that prevents backup resource contention during recovery from a link failure. The results quantify the gain in blocking probability for different partial protection scenarios. The mechanism proposed to counter backup contention is seen to provide an average of 120% reduction in the contention among backup paths of connections traversing a link, especially when the number of wavelengths in each link is small.