In this paper, two distinct optical network design approaches, namely mesh and multi-ring, for survivable WDM networks are investigated. The main objective is to compare these two design approaches in terms of network costs so that their merits in practical environments can be identified. In the mesh network design, a new mathematical model based on integer liner programming (ILP) and a heuristic algorithm are presented for achieving a minimal cost network design. In the multi-ring network design, a heuristic algorithm that can be applied to large network problems is proposed. The influence of wavelength conversion and the number of wavelengths multiplexed in a fiber on system designs are also discussed. Based on the simulation results, the redundancy quantities required for full protection in multi-ring approach are significantly larger in comparison to the minimal cost mesh counterpart.

This paper introduces 12 channel reservation techniques for medium access control (MAC) protocols suitable for high bit-rate wireless communication systems. The first 7 algorithms, namely CFP, CAP, COP, COP+SPL, CFP+SPL, UNI and UNI+LA, are applicable to systems with single-access chance per frame, whereas the other 5 algorithms, namely MT-CFP, MT-CFP+SPL, MT-UNI, MT-UNI+LUA and MT-UNI+LUT are suitable for systems with multi-access attempts per frame. The performance of these techniques are analytically evaluated and compared with the existing known techniques. The analytical model derived here are also validated through Monte Carlo computer simulations. Numerical results show that all proposed techniques are in general more superior to conventional reservation techniques. Finally when comparing between all proposed schemes in terms of both throughput performance and practical feasibility it is found that the MT-UNI+LA scheme are relatively efficient and suitable for practical applications.

This paper presents a comprehensive investigation of three optical wavelength-division multiplexed (WDM) mesh network protection approaches, namely minimal cost, single link basis and disjoint path approaches. The operation of each approach is described and their performances are extensively evaluated and compared. Key aspects that are taken into the consideration and comparison of the designs include a spare capacity requirement, ease of operation and practical feasibility. A mathematical model based on integer linear programming is introduced to obtain a lower bound on the spare capacity requirement for full protection against all single link failures. Two heuristic algorithms have also been developed to perform wavelength resource allocation under both normal and failure conditions for both systems with and without wavelength conversion capability. It is shown that the minimal cost approach can accomplish the lowest extra cost requirement for protection, but this approach is considered not appropriate for practical applications due to complicated restoration and management. The single link basis scheme is on the other hand more practical and very cost efficient. For the disjoint path technique, the cost for spare capacity is generally slightly greater than that of the single link basis scheme. Its main advantages lie in the simple re-configuration and inherent protection against node failure for in-transit traffic. Finally, a new framework for obtaining a good spare capacity cost estimate of a mesh restorable network is presented.

While the problem of multicast routing and wavelength assignment (MC-RWA) in optical wavelength division multiplexing (WDM) networks has been investigated, relatively few researchers have considered network survivability for multicasting. This paper provides an optimization framework to solve the MC-RWA problem in a multi-fiber WDM network that can recover from a single-link failure with shared protection. Using the light-tree (LT) concept to support multicast sessions, we consider two protection strategies that try to reduce service disruptions after a link failure. The first strategy, called light-tree reconfiguration (LTR) protection, computes a new multicast LT for each session affected by the failure. The second strategy, called optical branch reconfiguration (OBR) protection, tries to restore a logical connection between two adjacent multicast members disconnected by the failure. To solve the MC-RWA problem optimally, we propose an integer linear programming (ILP) formulation that minimizes the total number of fibers required for both working and backup traffic. The ILP formulation takes into account joint routing of working and backup traffic, the wavelength continuity constraint, and the limited splitting degree of multicast-capable optical cross-connects (MC-OXCs). After showing some numerical results for optimal solutions, we propose heuristic algorithms that reduce the computational complexity and make the problem solvable for large networks. Numerical results suggest that the proposed heuristic yields efficient solutions compared to optimal solutions obtained from exact optimization.

In a shared medium communication system, mobile users contend for channel access according to a given set of rules to avoid collisions and achieve efficient use of the medium. If one or more users do not comply with the agree rules either due to selfish or malicious behaviours, they will cause some impacts on the system performance, especially to the well-behaved users. In this paper, we consider the problem of user misbehaviours on the performance of a wireless infrastructure-based network using reservation-based MAC protocols. Key misbehaving strategies possible in such a network are identified and explained. To quantify the impact of these misbehaviours upon the network performance, three different misbehaving scenarios are developed to allow a systematic investigation of each misbehaving strategy. For each scenario, we have derived mathematical formulations for evaluating and analyzing the key performance metrics, i.e., probabilities of success of well-behaved and misbehaved users and the fairness index. Numerical results show that the presence of misbehaviours can cause different levels of damage depending on the misbehavior strategy used. The combined multi-token and increasing permission probability strategies where the misbehaved user selfishly accesses the channel more times and with higher probabilities than allowed is shown to cause the most severe impairment of performance and fairness.

This paper considers the problem of contention resolution algorithm for multi-class with quality of service (QoS) constrained for wireless communication. Five different channel reservation schemes are proposed, namely, UNI+MLA, UNI+DS, UNI+DS+MLA, Partial UNI and Partial UNI+MLA schemes for multimedia traffic, all are extensions of our recently proposed UNI scheme for single-class traffic. The goal is to achieve the highest system performance and enable each traffic type to meet its QoS requirements. We evaluate the performance of each scheme by mathematical analysis. The numerical results show that our proposed schemes are effective in enabling each traffic type to achieve the best successful rate possible in this kind of environment. Finally when comparing between our proposed schemes and conventional technique in terms of both throughput performance and QoS requirements it is found that the UNI+MLA, UNI+DS+MLA and Partial UNI+MLA schemes are relatively efficient and suitable for practical applications.

In this paper, we consider the problem of multicast routing and wavelength assignment (MC-RWA) in multi-fiber all-optical WDM networks. Two main network design system comprehensively investigated here are mesh and multi-ring designs. Given the multicast traffic demands, we present new ILP formulations to solve the MC-RWA problem with an objective to determine the minimal number of fibers needed to support the multicast requests. Unlike previous studies, our ILP formulations are not only capable of finding the optimal multicast routing and wavelength assignment pattern to the light-trees, but also finding the optimal light-tree structures simultaneously. Since broadcast and unicast communications are special cases of multicast communications, our ILP models are actually the generalized RWA mathematical models of optical WDM networks. In addition to proposing the ILP models, this paper takes two main issues affecting the network capacity requirement into account, that is, the splitting degree level of optical splitters and techniques of wavelength assignment to the light-trees. Three multicast wavelength assignment techniques studied in this paper are Light-Tree (LT), Virtual Light-Tree (VLT) and Partial Virtual Light-Tree (PVLT) techniques. Due to the NP-completeness of the MC-RWA problem, the ILP formulations can reasonably cope with small and moderate networks. To work with large networks, this paper presents alternative MC-RWA ILP-based heuristic algorithms for the PVLT and LT networks and develops lower bound techniques to characterize the performance of our algorithms. Using existing large backbone networks, numerical results are reported to analyze such aspects as multiple fiber systems, the benefits of using optical splitters and wavelength converters, and the capacity difference between the mesh and multi-ring designs. Finally, this paper provides an analysis of the influence of network connectivity on the network implementation under the constraints of mesh and multi-ring design schemes.