Distributed approaches for impairment-aware routing and wavelength assignment algorithms in GMPLS networks

This work proposes two different distributed strategies for provisioning lightpaths in the presence of optical physical-layer impairments in GMPLS networks. The first approach is a more classical one, which introduces new extensions to the OSPF-TE routing protocol. The other approach makes use of an Ant Colony Optimization (ACO) algorithm to adaptively calculate routes in the network by actively monitoring the aggregate optical power of each link.By using an analytical model to incorporate the constraints of the Amplified Spontaneous Emission (ASE) noise of the optical amplifiers into the routing, we demonstrate the effectiveness of our approaches by means of an illustrative numerical example.     

DWDM光网络中RWA问题的遗传求解方法

针对密集波分复用(dense wavelength-division multiplexing,DWDM)光网络通信中的动态路由与波长分配(routing and wavelength assignment,RWA)问题,提出了一种基于遗传算法的动态RWA方法.将遗传算法与分层图模型相结合,实现了RWA的方便计算.通过扩展适应值函数,能够有效地处理带时延约束的通信量请求.实验结果表明,与已有最短路径算法(Dijks-tra)相比,该算法能够提供多条候选路由方案,更适应较差环境下的网络通信.     

Selfish routing and wavelength assignment strategies with advance reservation in inter-domain optical networks

The main challenge in developing large data network in the wide area is in dealing with the scalability of the underlying routing system. Accordingly, in this work we focus on the design of an effective and scalable routing and wavelength assignment (RWA) framework supporting advance reservation services in wavelength-routed WDM networks crossing multiple administrative domains. Our approach is motivated by the observation that traffic in large optical networks spanning several domains is not controlled by a central authority but rather by a large number of independent entities interacting in a distributed manner and aiming at maximizing their own welfare. Due to the selfish strategic behavior of the involved entities, non-cooperative game theory plays an important role in driving our approach. Here the dominant solution concept is the notion of Nash equilibria, which are states of a system in which no participant can gain by deviating unilaterally its strategy. On this concept, we developed a selfish adaptive RWA model supporting advance reservation in large-scale optical wavelength-routed networks and developed a distributed algorithm to compute approximate equilibria in computationally feasible times. We showed how and under which conditions such approach can give rise to a stable state with satisfactory solutions and analyzed its performance and convergence features.     

A novel ring-tree-based routing and wavelength assignment algorithm for multicasting in DWDM optical mesh networks

Multicast session communications, such as video-conferencing and video-broadcasting, in DWDM mesh networks require the efficient multipoint-to-multipoint multicast algorithms. Several heuristics have approximate solutions using lightpath or light-tree for one-to-multipoint multicast communications, but few papers have discussed the multipoint-to-multipoint multicast problems in DWDM mesh networks. This paper proposes a ring-tree-based routing and wavelength assignment (RTRWA) solution in DWDM mesh networks. It proceeds to multipoint-to-multipoint multicast transmission by reserving links and wavelengths assigned by the Least Converter Count algorithm. The RTRWA algorithm tries to find an optimal ring path that connects all multicast session members with unidirectional links and connects the remaining nodes to the ring path with the light-tree. The RTRWA algorithm outperforms the Steiner minimal tree (SMT) algorithm in terms of the call blocking probability, difference in user capacity and the mean maximum transmission time.     

A multipopulation parallel genetic simulated annealing-based QoS routing and wavelength assignment integration algorithm for multicast in optical networks

In this paper, we propose an integrated Quality of Service (QoS) routing algorithm for optical networks. Given a QoS multicast request and the delay interval specified by users, the proposed algorithm can find a flexible-QoS-based cost suboptimal routing tree. The algorithm first constructs the multicast tree based on the multipopulation parallel genetic simulated annealing algorithm, and then assigns wavelengths to the tree based on the wavelength graph. In the algorithm, routing and wavelength assignment are integrated into a single process. For routing, the objective is to find a cost suboptimal multicast tree. For wavelength assignment, the objective is to minimize the delay of the multicast tree, which is achieved by minimizing the number of wavelength conversion. Thus both the cost of multicast tree and the user QoS satisfaction degree can approach the optimal. Our algorithm also considers load balance. Simulation results show that the proposed algorithm is feasible and effective. We also discuss the practical realization mechanisms of the algorithm.     

A survey on routing algorithms for wireless Ad-Hoc and mesh networks

Wireless networking technology is evolving as an inexpensive alternative for building federated and community networks (relative to the traditional wired networking approach). Besides its cost-effectiveness, a wireless network brings operational efficiencies, namely mobility and untethered convenience to the end user. A wireless network can operate in both the “Ad-Hoc” mode, where users are self-managed, and the “Infrastructure” mode, where an authority manages the network with some Infrastructure such as fixed wireless routers, base stations, access points, etc. An Ad-Hoc network generally supports multi-hopping, where a data packet may travel over multiple hops to reach its destination. Among the Infrastructure-based networks, a Wireless Mesh Network (with a set of wireless routers located at strategic points to provide overall network connectivity) also provides the flexibility of multi-hopping. Therefore, how to route packets efficiently in wireless networks is a very important problem.A variety of wireless routing solutions have been proposed in the literature. This paper presents a survey of the routing algorithms proposed for wireless networks. Unlike routing in a wired network, wireless routing introduces new paradigms and challenges such as interference from other transmissions, varying channel characteristics, etc. In a wireless network, routing algorithms are classified into various categories such as Geographical, Geo-casting, Hierarchical, Multi-path, Power-aware, and Hybrid routing algorithms. Due to the large number of surveys that study different routing-algorithm categories, we select a limited but representative number of these surveys to be reviewed in our work. This survey offers a comprehensive review of these categories of routing algorithms.In the early stages of development of wireless networks, basic routing algorithms, such as Dynamic Source Routing (DSR) and Ad-Hoc On-demand Distance Vector (AODV) routing, were designed to control traffic on the network. However, it was found that applying these basic routing algorithms directly on wireless networks could lead to some issues such as large area of flooding, Greedy Forwarding empty set of neighbors, flat addressing, widely-distributed information, large power consumption, interference, and load-balancing problems. Therefore, a number of routing algorithms have been proposed as extensions to these basic routing algorithms to enhance their performance in wireless networks. Hence, we study the features of routing algorithms, which are compatible with the wireless environment and which can overcome these problems.     

A reliable QoS aware routing protocol with slot assignment for mobile ad hoc networks

A mobile ad hoc network (MANET) is a collection of mobile hosts that form a temporary network on the fly without using any fixed infrastructure. Recently, the explosive growth in the use of real-time applications on mobile devices has resulted in new challenges to the design of protocols for MANETs. Chief among these challenges to enable real-time applications for MANETs is incorporating support for quality of service (QoS), such as bandwidth constraints. However, MANETs having a high ratio of topology change make routing especially unstable; making stability is an important challenge, especially for routing having a quality of service provision. In this paper, we propose a reliable multi-path QoS routing (RMQR) protocol with a slot assignment scheme. In this scheme, we examine the QoS routing problem associated with searching for a reliable multi-path (or uni-path) QoS route from a source node to a destination node in a MANET. This route must also satisfy certain bandwidth requirements. We determine the route expiration time between two connected mobile nodes using global positioning system (GPS). Then, two parameters, the route expiration time and the number of hops, are used to select a routing path with low latency and high stability. Simulation results show that the proposed RMQR protocol have some outstanding properties when compared with Lin's [Lin C-R. On-demand QoS routing in multihop mobile networks. In: Proceedings of the twentieth annual joint conference of the IEEE computer and communications societies (INFOCOM), vol. 3(22–26), 2001, p. 1735–44], Liao's [Liao W-H, Tseng Y-C, Wang S-L, Sheu J-P. A multi-path QoS routing protocol in a wireless mobile Ad Hoc network. Telecommunication Systems 2002;19(3–4):329–47], and Chen's [Chen Y-S, Tseng Y-C, Sheu J-P, Kuo P-H. An on-demand, link-state, multi-path QoS routing in a wireless mobile Ad-Hoc network. Computer Communications 204;27(1):27–40] protocols.     

Ant colony optimization for dynamic routing and wavelength assignment in WDM networks with sparse wavelength conversion

Since optical WDM networks are becoming one of the alternatives for building up backbones, dynamic routing, and wavelength assignment with delay constraints (DRWA-DC) in WDM networks with sparse wavelength conversions is important for a communication model to route requests subject to delay bounds. Since the NP-hard minimum Steiner tree problem can be reduced to the DRWA-DC problem, it is very unlikely to derive optimal solutions in a reasonable time for the DRWA-DC problem. In this paper, we circumvent to apply a meta-heuristic based upon the ant colony optimization (ACO) approach to produce approximate solutions in a timely manner. In the literature, the ACO approach has been successfully applied to several well-known combinatorial optimization problems whose solutions might be in the form of paths on the associated graphs. The ACO algorithm proposed in this paper incorporates several new features so as to select wavelength links for which the communication cost and the transmission delay of routing the request can be minimized as much as possible subject to the specified delay bound. Computational experiments are designed and conducted to study the performance of the proposed algorithm. Comparing with the optimal solutions found by an ILP formulation, numerical results evince that the ACO algorithm is effective and robust in providing quality approximate solutions to the DRWA-DC problem.     

Routing and wavelength assignment for hypercube in array-based WDM optical networks

Hypercube is one of the most versatile and efficient communication patterns shared by a large number of computational problems. As the number of edges in hypercube grows logarithmically with the size of networks, the complexity of network topologies can be significantly reduced to realize hypercube in optical networks by taking advantage of the parallel transmission characteristic of optical fibers. In this paper, we study the routing and wavelength assignment for realizing hypercube on WDM optical networks including linear arrays and rings with the consideration of communication directions. Specifically, we analyze this problem for both bidirectional and unidirectional hypercubes. For each case, we identify a lower bound on the number of wavelengths required, and design the embedding scheme and wavelength assignment algorithm that uses a provably near-optimal number of wavelengths. In addition, we extend the results to meshes and tori. By our embedding schemes, many algorithms, originally designed based on hypercubes, can be applied to optical networks, and the wavelength requirements can be easily derived using our obtained results.     

基于WAPG动态路由与波长分配的优化算法

多粒度交换能减少交换节点中的交换矩阵规模及复用器和解复用器的数目,很大程度降低了网络成本,但使得光纤网络路由与波长分配问题变得更加复杂.通过分析多粒度光网络交换节点的结构和动态路由与波长分配的特点,定义5种不同的逻辑链路权重标注方法,提出一种基于路径图波带分配的路由与波长分配模型,达到减少波长碎片的目的.模拟结果表明,该方法能有效地减少多粒度光网络中的波长转换数和降低网络成本.     

Routing wavelength and time-slot reassignment algorithms for TDM based optical WDM networks

In this paper, we consider the problem of maximizing the time of first lightpath request rejection, T in the circuit-switched time division multiplexed (TDM) wavelength-routed (WR) optical WDM networks. TDM is incorporated into WDM, to increase the channel utilization when the carried traffic does not require the entire channel bandwidth. In TDM–WDM network, multiple sessions are multiplexed on each wavelength by assigning a sub-set of the TDM slots to each session. Thus, given a session request with a specified bandwidth, a lightpath has to be established by using the routing, wavelength and time-slot assignment (RWTA) algorithms. If the lightpath cannot be established, lightpath request rejection or call blocking occurs. As each lightpath is substantial revenue and long-lived, lightpath request rejection is highly unfavourable in the optical backbone networks. In this paper, we are proposing an intelligent routing, wavelength and time-slot reassignment algorithm for multi-rate traffic demands, where, when a call gets blocked, the already established calls in the network are rerouted, wavelength and time-slot reassigned so as to accommodate the blocked call. Since we are talking of slow arrivals and long holding times for the lightpaths, it is possible to do this reassignment while provisioning a new call. Simulation based analyses are used to study the performance of the proposed reassignment algorithm. The results show that the proposed reassignment algorithm can be used to maximize the time of first call blocking, thereby accommodating more calls in the network before upgrading the network capacity.     

Traffic grooming, routing, and wavelength assignment in WDM transport networks with sparse grooming resources

While a single fiber strand in wavelength division multiplexing (WDM) has over a terabit-per-second bandwidth and a wavelength channel has over a gigabit-per-second transmission speed, the network may still be required to support traffic requests at rates that are lower than the full wavelength capacity. To avoid assigning an entire lightpath to a small request, many researchers have looked at adding traffic grooming to the routing and wavelength assignment (RWA) problem. In this work, we consider the RWA problem with traffic grooming (GRWA) for mesh networks under static and dynamic lightpath connection requests. The GRWA problem is NP-Complete since it is a generalization of the RWA problem which is known to be NP-Complete. We propose an integer linear programming (ILP) model that accurately depicts the GRWA problem. Because it is very hard to find a solution for large networks using ILP, we solve the GRWA problem by proposing two novel heuristics. The strength of the proposed heuristics stems from their simplicity, efficiency, and applicability to large-scale networks. Our simulation results demonstrate that deploying traffic grooming resources on the edge of optical networks is more cost effective and results in a similar blocking performance to that obtained when distributing the grooming resources throughout the optical network domain.     

Design principles and improvement of cost function based energy aware routing algorithms for wireless sensor networks

Cost function based routing has been widely studied in wireless sensor networks for energy efficiency improvement and network lifetime elongation. However, due to the complexity of the problem, existing solutions have various limitations. In this paper, we analyze the inherent factors, design principles and evaluation methods for cost function based routing algorithms. Two energy aware cost based routing algorithms named Exponential and Sine Cost Function based Route (ESCFR) and Double Cost Function based Route (DCFR) have been proposed in this paper. For ESCFR, its cost function can map small changes in nodal remaining energy to large changes in the function value. For DCFR, its cost function takes into consideration the end-to-end energy consumption, nodal remaining energy, resulting in a more balanced and efficient energy usage among nodes. The performance of the cost function design is analyzed. Extensive simulations demonstrate the proposed algorithms have significantly better performance than existing competing algorithms.     

A novel algorithm for routing and wavelength assignment considering the load balancing

For the problem of routing and wavelength assignment in Wavelength Division Multiplexing （WDM） optical transport network, an algorithm based on the state of links is proposed, which is named Tradeoff_LSDRAW, and which can select a path with the higher state level between a pair of nodes in a network. Finally, by an example network, we show that the algorithm has the stronger capability of selecting a better path between a pair of nodes, and can achieve the load balancing and reduce the congestion probability in WDM optical transport networks.     

Position-based routing in vehicular networks: A survey

Routing in vehicular network is a challenging task due to network partitioning, high vehicular speed, and city environment characteristics. These characteristics results in degraded performance in traditional routing protocols. Traditional routing protocols, addressing the issues of mobile ad hoc network, are applicable for MANET applications. Position-based routing protocols, which are mostly based on greedy routing, are more suited to highly dynamic and mobile network. In this paper, we survey state of art routing protocols previously used in vehicular networks, present open research challenges and possible future direction. We categorize protocols into two categories based on their communicating mode (vehicle-to-vehicle, vehicle-to-infrastructure) irrespective of their simulating environment (highway, urban). Both vehicle-to-vehicle and vehicle-to-infrastructure communication provides connectivity based on multi-hop paradigm in a seamless way. We discuss pros and cons for routing protocols belonging to each category. By doing qualitative comparison of routing protocols, it is observed that hybrid communication would be the better choice for both communication mode operable in either a city environment or an open environment.     

A survey on routing techniques in underwater wireless sensor networks

Underwater Wireless Sensor Networks (UWSNs) are finding different applications for offshore exploration and ocean monitoring. In most of these applications, the network consists of significant number of sensor nodes deployed at different depths throughout the area of interest. The sensor nodes located at the sea bed cannot communicate directly with the nodes near the surface level; they require multi-hop communication assisted by appropriate routing scheme. However, this appropriateness depends not only on network resources and application requirements but also on environmental constraints. All these factors provide a platform where a resource-aware routing strategy plays a vital role to fulfill the different application requirements with dynamic environmental conditions. Realizing the fact, significant attention has been given to construct a reliable scheme, and many routing protocols have been proposed in order to provide an efficient route discovery between the sources and the sink. In this paper, we present a review and comparison of different algorithms, proposed recently in order to fulfill this requirement. The main purpose of this study is to address the issues like data forwarding, deployment and localization in UWSNs under different conditions. Later on, all of these are classified into different groups according to their characteristics and functionalities.     

Parallel algorithms for routing in nonblocking networks

We construct nonblocking networks that are efficient not only as regards their cost and delay, but also as regards the time and space required to control them. In this paper we present the first simultaneous weakly optimal solutions for the explicit construction of nonblocking networks, the design of algorithms and data-structures. Weakly optimal is in the sense that all measures of complexity (size and depth of the network, time for the algorithm, space for the data-structure, and number of processor-time product) are within one or more logarithmic factors of their smallest possible values. In fact, we construct a scheme in which networks withn inputs andn outputs have sizeO(n(logn)²) and depthO(logn), and we present deterministic and randomized on-line parallel algorithms to establish and abolish routes dynamically in these networks. In particular, the deterministic algorithm usesO((logn)⁵) steps to process any number of transactions in parallel (with one processor per transaction), maintaining a data structure that useO(n(logn)²) words.     

1.5-Approximation algorithm for weighted maximum routing and wavelength assignment on rings

We give a 1.5-approximation algorithm for the weighted maximum routing and wavelength assignment problem on undirected ring networks. This improves the previous 1.58-approximation result.     

A mobility aware protocol synthesis for efficient routing in ad hoc mobile networks

In mobile ad hoc networks (MANETs), the mobility of the nodes is a complicating factor that significantly affects the effectiveness and performance of the routing protocols. Our work builds upon recent results on the effect of node mobility on the performance of available routing strategies (i.e., path-based, using support) and proposes a protocol framework that exploits the usually different mobility rates of the nodes by adapting the routing strategy during execution. We introduce a metric for the relative mobility of the nodes, according to which the nodes are classified into mobility classes. These mobility classes determine, for any pair of origin and destination, the routing technique that best corresponds to their mobility properties. Moreover, special care is taken for nodes remaining almost stationary or moving with high (relative) speeds. Our key design goal is to limit the necessary implementation changes required to incorporate existing routing protocols into our framework. We provide extensive evaluation of the proposed framework, using a well-known simulator (NS2). Our first findings demonstrate that the proposed framework improves, in certain cases, the performance of existing routing protocols.     

Local routing algorithms based on Potts neural networks

A feedback neural approach to static communication routing in asymmetric networks is presented, where a mean field formulation of the Bellman-Ford method for the single unicast problem is used as a common platform for developing algorithms for multiple unicast, multicast and multiple multicast problems. The appealing locality and update philosophy of the Bellman-Ford algorithm is inherited. For all problem types the objective is to minimize a total connection cost, defined as the sum of the individual costs of the involved arcs, subject to capacity constraints. The methods are evaluated for synthetic problem instances by comparing to exact solutions for cases where these are accessible, and else with approximate results from simple heuristics. In general, the quality of the results are better than those of the heuristics. Furthermore, the computational demands are modest, even when the distributed nature of the the approach is not exploited numerically.