Performance Evaluation of Fixed Routing Algorithms in All-Optical Networks under Non-uniform Traffic

In order to transmit data efficiently over an optical network, many routing and wavelength assignment (RWA) algorithms have been proposed. This work presents a genetic algorithm that aims at solving the RWA problem, which consists of choosing the most suitable lightpath (i.e., a combination of a route and a wavelength channel) between a source-destination pair of nodes in all-optical networks. A comparison to some already known approaches in terms of blocking probability was made. Results show a reasonable performance, since the average blocking probability achieved by the genetic algorithm was lower than or relatively equivalent to the standard approaches compared.

The problem of dynamic routing in a multifibre time-slotted wavelength routed WDM network is considered. Requests to establish a connection are dynamic and each connection requests an integer multiple of some basic unit. Each wavelength has the capacity of carrying a multiple of these channels, where each channel is represented by a time-slot as in TDM networks. The network is represented as a layered graph model with multiple layers, where each layer represents a specific wavelength. Each link in the layered graph has one or more fibres and an associated cost. The cost of layered graph links could be a function of the loading state of the respective wavelength across the available fibres. Algorithms are proposed for fibre selection and for setting link costs, and a modified Dijkstra algorithm on the layered graph is used to select a route on the layered graph for a new connection request. The selected route on the layered graph represents the physical path and the selected wavelength. The performance of these algorithms is evaluated for a realistic mesh network topology for various combinations of the number of wavelengths, the number of fibres per link, the number of time-slots per wavelength, and the offered load for both uniform and non-uniform traffic loads. The best performing fibre selection and link cost update methods are identified. The proposed algorithm for routing and wavelength assignment in mesh optical WDM grooming networks outperforms previously proposed work in the literature.

The method in which Routing and Wavelength Assignment (RWA) of connection requests is performed in optical WDM networks, can appreciably affect resource consumption. The blocking probability for lightpath requests increases significantly with increase in resource consumption. Thus the method of performing RWA should be such that it minimizes consumption of network resources. RWA in all-optical networks is an NP-Complete problem. This paper proposes six new heuristic algorithms for static RWA in all-optical mesh networks that are not only efficient in terms of resource conservation but can also solve the RWA problem effectively in polynomial time. Comparisons show that the proposed algorithms perform better than some earlier well-known strategies.

The power and signal-to-noise ratio fluctuations and transmission penalties during transients in an all-optical gain-controlled WDM network have been investigated. The impact of the coherent self-homdyne crosstalk from a gain-clamped EDFA on the system's performance has been evaluated for the first time.

An improved approximate network blocking probability model for all-optical WDM Networks with heterogeneous link capacities

Dynamic routing and wavelength assignment (RWA) is an attractive method for the efficient use of network resources in all-optical networks. We present a novel fixed alternate routing method referred to as Overlap-Degree Aware (ODA) routing in all-optical networks. A lot of researchers have focused on the shortest path routing and alternate shortest path routing taking into acount link and wavelength usage so as to reduce the consumption of network resources. The authors, however, believe that in order to minimize the blocking probability, it is important to consider not only the consumption of link and wavelength resources but also the existence of the other flows when a routing decision is made. The ODA routing decides routes using the knowledge of ingress-egress node pairs, and tries to prevent future path requests from being blocked unnecessarily by reserving link and wavelength resources for the future requests. Our simulation results show that our new routing algorithm outperforms Fixed-Alternate Routing (FAR) and Weighted Least Congestion Routing (WLCR) from the viewpoint of call blocking probability.

Unlike broadcast-and-select networks, wavelength-routing networks offer the advantages of wavelength reuse and scalability and are thus suitable for wide-area networks (WANs) We study the effects of topological connectivity and wavelength conversion in circuit-switched all-optical wavelength-routing networks. A blocking analysis of such networks is given. We first propose an analytical framework for accurate analysis of networks with arbitrary topology. We then introduce a model for networks with a variable number of converters and analyze the effect of wavelength converter density on the blocking probability. This framework is applied to three regular network topologies that have varying levels of connectivity: the ring, the mesh-torus, and the hypercube. The results show that either a relatively small number of converters is sufficient for a certain level of performance or that conversion does not offer a significant advantage. The benefits of conversion are largely dependent on the network load, the number of available wavelengths, and the connectivity of the network. Finally, the tradeoff between physical connectivity, wavelength conversion, and the number of available wavelengths is studied through networks with random topologies.

In this paper a practical routing algorithm is proposed that increases the network throughput irrespective of the network traffic load. Its effectiveness is based on an efficient cost function which achieves a successful trade-off between the use of the minimum-hop routes and the application of the load-balancing concept. Moreover, it employs the known Trunk Reservation notion according to a probability that increases linearly with the traffic load. This results in an effective compromise of the performance of the algorithm between light and heavy traffic loads. Finally, its simplicity and its suitability for a real-time application render it as an efficient routing algorithm for ATM networks. Copyright © 1999 John Wiley & Sons, Ltd.

In this paper a practical routing algorithm is proposed that increases the network throughput irrespective of the network traffic load. Its effectiveness is based on an efficient cost function which achieves a successful trade-off between the use of the minimum-hop routes and the application of the load-balancing concept. Moreover, it employs the known Trunk Reservation notion according to a probability that increases linearly with the traffic load. This results in an effective compromise of the performance of the algorithm between light and heavy traffic loads. Finally, its simplicity and its suitability for a real-time application render it as an efficient routing algorithm for ATM networks. Copyright © 1999 John Wiley & Sons, Ltd.

In this paper, we present a wavelength routing technique with spare reconfiguration (SR) to construct dependable all-optical WDM networks. Path protection using shared spare lightpaths is a general wavelength routing method to improving the blocking probability while minimizing the required spare resources. However, in a dynamic traffic environment, this method may still lead to poor performance because it is highly likely that a wavelength on a link is continuously held by a spare lightpath and can not be assigned to the working lightpath of a new connection. This paper presents a spare reconfiguration mechanism with wavelength reassignment (SR_WR) and path reassignment (SR_PR) to make the spare dynamic and thus to further reduce the blocking probability. It uses an occupancy function q, a tuning function g, and the conflict table T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> to enable the spare reconfiguration when a new connection arrives. The set of lightpaths using a wavelength of the link is recorded by the function q. It contains the same information as shared risk link group (SRLG) used by other researches. The available wavelength or path that a spare lightpath can he tuned during the spare reconfiguration is obtained through the function g. While T <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> maintains the relationship between the wavelength used by the spare lightpath and the link used by the corresponding working lightpath. The proposed wavelength routing with SR proceeds in three stages and has polynomial time complexity. Extensive simulation experiments were conducted on the NSFNET and the fully connected network to study the performance of the proposed wavelength routing with SR. The results show that the proposed wavelength routing with SR can reduce the blocking probability when compared with the general wavelength routing with just shared spare lightpaths by choosing the positive tuning cost. In addition, the best improvement on the blocking performance is achieved when using SR_WR first and SR_PR second.

In WDM optical networks connection requests can be classified into three different types: Permanent Lightpath Demands (PLDs), Scheduled Lightpath Demands (SLDs), and Random Lightpath Demands (RLDs). These three types of traffic demands are considered for network planning, network engineering and traffic engineering respectively. In this paper we investigate the Routing and Wavelength Assignment (RWA) problem in all-optical WDM networks operating under the wavelength continuity constraint by jointly considering PLDs, SLDs and RLDs. We aim to model a realistic situation where an operator wishes to employ its optical network initially designed for PLDs and/or SLDs to offer on the fly lightpath provisioning. To the best of our knowledge, our global approach has not already been investigated in the literature. According to the considered timescale, various types of optimization tools are used. Numerous numerical results are presented and discussed to outline the benefits of such a global perspective.

As an important part of satellite communication network, LEO satellite constellation network is one of the hot research directions. Since the nonuniform distribution of terrestrial services may cause inter-satellite link congestion, improving network load balancing performance has become one of the key issues that need to be solved for routing algorithms in LEO network. Therefore, by expanding the range of available paths and combining the congestion avoidance mechanism, a load balancing routing algorithm based on extended link states in LEO constellation network is proposed. Simulation results show that the algorithm achieves a balanced distribution of traffic load, reduces link congestion and packet loss rate, and improves throughput of LEO satellite network.

Two quasi-static minimax open shortest path first (OSPF) routing algorithms in networks supporting the Switched Multi-megabit Data Service (SMDS) are presented and compared. In OSPF routing, the network is modeled as a graph and each link is associated with a nonnegative arc weight. A shortest path spanning tree is calculated for each origin to carry both the individually addressed and the group addressed (multicast) traffic. The OSPF routing protocol is adopted as a major part of the default inter-switching system interface (ISSI) routing algorithm for SMDS networks where arc weights are inversely proportional to the aggregate link set capacities. The problem of choosing a set of link set metrics is considered so that the maximum link utilization factor is minimized in an SMDS network. The problem is formulated as a nonlinear mixed integer programming problem.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

When it comes to WSN, routing is the most difficult and time-consuming part. For WSN, there are a variety of routing protocols. Routing techniques for mobile sensor networks include Ad hoc On-Demand Distance Vector (AODV). The use of less energy. NAODV is a new routing protocol that incorporates an energy-aware algorithm and the shortest route into the current Ad hoc On-demand Distance Vector Routing (NAODV) protocol in order to save battery consumption and WSN lifespan. Research challenges including packet loss and energy consumption have been taken into consideration when developing new routing protocols for mobile nodes. The simulation results demonstrate that a combination of both bandwidth and energy management works better than the present methods. According to this study, the suggested cluster-based routing algorithms for mobile wireless sensor networks are compared among themselves. According to the simulation results, the suggested energy-efficient routing algorithm consumes very little energy and provides a high level of performance. A study of the AODV protocol's throughput, packet rate, coverage area, and the number of packets has been conducted in this work. With 11 nodes, our simulation findings demonstrate that the network's lifespan is increased greatly without affecting packet delivery speed. Cells, the smallest unit of geographic division in the 5G network, will be used to connect providers' service areas. There are still certain locations that don't yet have access to 5G. Thus new gadgets may still connect to 4G LTE networks. Data aggregation methods are crucial to network efficiency. Accumulating and effectively condensing data packets is the fundamental goal of a data aggregation technique. This study created a hybrid clustering and routing strategy for data aggregation in 5G wireless sensor networks.

An important aspect of the MAC layer design for mobile ad hoc networks (MANETs) is the ability to adapt to spatially non-uniform traffic load distributions. While coordinated channel access protocols have been shown to be well suited for highly loaded MANETs, these protocols are in general not as well suited for non-uniform load distributions as uncoordinated channel access protocols. In order to improve the performance of coordinated MAC protocols for MANETs under non-uniform load distribution, in this paper we apply to MANETs the dynamic channel allocation concept used in cellular networks. We present a new coordinated MAC protocol called DCA-TRACE (Dynamic Channel Allocation for TRACE), which is a sequel of our earlier MH-TRACE protocol. In addition to the mechanisms that exist in MH-TRACE for throughput and energy efficiency maximization, DCA-TRACE implements a distributed dynamic channel allocation strategy based on spectrum sensing. We compare DCA-TRACE with the MH-TRACE and 802.11 protocols in terms of throughput, energy consumption and interpacket delay variation (IPDV). Simulation results show that DCA-TRACE provides significant improvement for both uniform and non-uniform traffic loads.