A framework for the multicast lifetime maximization problem in energy-constrained wireless ad-hoc networks

We consider the problem of maximizing the lifetime of a given multicast connection in wireless networks that use directional antennas and have limited energy resources. We provide a globally optimal solution to this problem for a special case of using omni-directional antennas. This graph theoretic approach provides us insights into more general case of using directional antennas, and inspires us to produce a group of heuristic algorithms. Experimental results show that our algorithms outperform other energy-aware multicast algorithms significantly in terms of multicast lifetime.

Study of multicast wavelength arrangement for maximizing network capacity in WDM networks with sparse wavelength converters

The issue of wavelength assignment is one of the most important factors that affect the capacity for the deployment of optical networks. This issue becomes more critical for multicast connections, especially when the network nodes have no wavelength conversion capability. Although the wavelength assignment can be more flexible if each node can perform wavelength conversion, the deployment cost increases accordingly. A compromise is to support a limited portion of conversion nodes in the WDM network. We propose a systematic approach for the wavelength assignment of multicast connections in WDM networks with sparse wavelength conversion nodes. The efficiency of the arrangement of wavelength is measured by its influences on the available capacity of the network and the consumption of wavelengths. By using the proposed approach, the Static Cost Greedy (SCG) algorithm [8] can be easily extended to be applicable in a Sparse Wavelength Conversion Network (SWCN). In addition, instead of SCG, the Minimum-Effect-First (MEF) algorithm is proposed to maximize the network capacity during wavelength assignment. We compare the performance of the proposed MEF methods with the extended SCG scheme through exhaustive simulations. The experimental results indicate that the proposed MEF schemes demonstrate much better performance than the SCG scheme. We also found that the performance is not always improved proportionally to the increment of the wavelength conversion nodes. The improvement reaches saturation when the number of conversion nodes is above 35% of the total number of nodes.

GMZRP: Geography-aided Multicast Zone Routing Protocol in Mobile Ad Hoc Networks

This paper presents the design and evaluation of a highly efficient on-demand multicast routing protocol for mobile ad hoc networks (MANETs). The protocol, called Geography-aided Multicast Zone Routing Protocol (GMZRP), eliminates as much as possible duplicate route queries by using a simple yet effective strategy for propagating the multicast route request (MRREQ) packets. GMZRP is the first hybrid multicast protocol taking the advantages of both topological routing and geographical routing. It partitions the network coverage area into small zones and guarantees that each geographic zone is queried only once. GMZRP maintains a multicast forwarding tree at two levels of granularities, i.e., the zone granularity and the node granularity. By doing this, it can easily handle route breakage since the zone level information can help recover the link failure at the node level. The results of the performance evaluation of GMZRP using simulation show that, comparing with the well-known multicast protocol ODMRP (On-Demand Multicast Routing Protocol), GMZRP has much lower protocol overhead in terms of query packets and, meanwhile, achieves competing packet delivery ratio and shorter delivery latency.

Distributed Dijkstra sparse placement routing algorithm for translucent optical networks

In this paper we study translucent optical networks as an alternative to fully transparent and fully opaque optical networks. In the former networks, a technique called sparse placement is used to overcome the lightpath blocking caused by the signal quality degradation, using much less regenerators, which must strategically be placed, in contrast to a fully opaque network. In this paper we propose a sparse placement algorithm based on two requirements. The first one is signal regeneration necessary to re-amplify, reshape, and retime the optical signals after some predefined transparent distance in order to successfully receive the signals at the destination node. The other is load balance of the traffic in the network aimed at efficient usage of the network capacity resources. We apply a distributed Dijkstra routing algorithm which dynamically changes weights of links during the process of locating regeneration capable nodes. We compare the performance of the proposed algorithm with commonly used sparse placement algorithms through simulation experiments. The benefits are such that load balancing of the network traffic is fully utilized, and with technological development it will be sufficient to equip up to 30% of nodes in the network with electronic regenerations in order to have the same performance as in an opaque network.

Scalable architectures for all-optical label swapping nodes

All-Optical Label Swapping (AOLS) nodes are believed to be part of the future networks. The original node designs, however, are very hard scalable. This article presents three alternatives that swap labels analogous to the original design. Two of the proposed new switches use the same all-optical technology to parallelly compare labels but, they divide fibres in data wavelengths that only transport payloads and label wavelengths that only transport labels. The third design sequentially compares the incoming label with addresses in the node available in order to make the routing decision. All three architectures are compared in terms of hardware necessary to perform routing.

Performance evaluation of p-cycle based protection methods for provisioning of dynamic multicast sessions in mesh WDM networks

Network survivability is crucial to both unicast and multicast traffic. Up to now, extensive research has been done on unicast traffic protection. Recently, due to the rapid growth of multicast applications, such as video-conferencing, high definition television (HDTV), distance learning, and multi-player on-line gaming, the problem of multicast traffic protection has started to draw more research interests. The preconfigured protection cycle (p-cycle) method proposed by Grover offers fast speed in restoration (because p-cycles are pre-cross-connected) and high efficiency in resource utilization (because p-cycles protect both on-cycle and straddling links). So far p-cycles based protection approaches have been intensively studied for unicast traffic protection, but have been rarely investigated for multicast traffic. We propose to apply p-cycles to dynamic protection provisioning of multicast traffic, and evaluate the blocking performance in comparison to other existing multicast protection schemes. We consider three different p-cycle based multicasting protection methods, namely dynamic p-cycle (DpC) design, p-cycle based protected working capacity envelope (PWCE) design, and hybrid DpC and PWCE design. We show that p-cycle-based multicast protection approaches offer much better blocking performance, as compared with other existing multicast protection schemes. The main reasons for the much better blocking performance are attributed to the facts that (i) the selection of p-cycles is independent of the routing of the multicast light trees, (ii) there are no path/segment disjoint constraints between the selected p-cycles and the multicast light trees to be protected, (iii) the selected p-cycles are the most efficient p-cycles.

A route maintaining algorithm using neighbor table for mobile sinks

In the wireless microsensor networks, both source and sink nodes can be changed or mobile. The movement of source and sink may lead to the breakage of existing routes. In most routing protocols, query packets are broadcasted to correct a broken route between source and sink, which causes significant communication overhead in terms of both energy and delay. In order to support the sink mobility of conventional routing protocols, we propose a simple route maintaining algorithm which does not use the flooding method. Since the proposed algorithm does not require the information on the geometric location of sensor nodes, it can be easily adopted in most existing routing protocols including Ad Hoc On Demand Distance Vector (AODV) and Direct Diffusion (DD). Experimental results show that the proposed algorithm drastically improves the conventional routing protocols in terms of both energy and delay in case of mobile sinks.

DTN Based Dominating Set Routing for MANET in Heterogeneous Wireless Networking

In mobile communications, effective inter-networking is mandatory in order to support user roaming among various types of wireless networks while maintaining connectivity. In this paper, we propose a super node system architecture to achieve the connectivity over interconnected heterogeneous wireless access networks, which employs the delay-tolerant network (DTN) concept to overcome the problem of potential intermittent connections caused by user roaming and ensures message delivery in the presence of a long disconnection period. By introducing the concept of virtual network topology, we present a new routing technique for mobile ad hoc networks (MANETs) within the system architecture, which redefines the dominating-set based routing for the challenged network environment. A time based methodology is presented to predict the probability of future contacts between node pairs for constructing the virtual network topology. Simulation results demonstrate the effectiveness of the proposed dominating-set based routing scheme under the DTN system architecture.

An Approach to Increase the Lifetime of a Linear Array of Wireless Sensor Nodes

The nodes in a wireless sensor network are generally energy constrained. The lifetime of such a network is limited by the energy dissipated by individual nodes during signal processing and communication with other nodes. The issues of modeling a sensor network and assessment of its lifetime have received considerable attention in recent years. This paper provides an analytical framework for placing a number of nodes in a linear array such that each node dissipates the same energy per data gathering cycle. This approach ensures that all nodes run out of battery energy almost simultaneously. It is shown that the network lifetime almost doubles with the proposed scheme as compared to other reported schemes. However, in practice, the nodes are not expected to be placed as per this theoretical requirement. The issue of random placement of nodes has also been investigated to obtain the statistics of energy consumption of a node. The analytical results for random node placement are validated through simulation studies.

Information-based connection algorithm for supporting QoS in nested mobility network

A multihop mobile wireless network can be a collection of wireless mobile nodes forming a temporary network without the aid of any established infrastructure or centralized administration. Mobile nodes communicate with each other using multihop wireless links. Each mobile node in the network also acts as a router, which forwards data packets to other nodes. A main challenge in the design of this mobile network is the development of dynamic routing protocols that can efficiently find routes between two communicating nodes that often change the network topology drastically and unpredictably. All communications between the nodes inside the mobile network and the global Internet must be maintained, although the mobile router (MR) connecting the other mobile network to the global Internet must change their address; and mobile nodes suffer from end-to-end delay and handoff delay. That is to say, hereafter the packets sailing for the mobile node would not be routed directly for the destination, but will always make a detour by way of HA to the target node. In this paper, we suggest Information-based Connection Algorithm that adds keyword management method in order to resolve such a problem, simulations are carried out with NS-2 for performance evaluation. The results of the simulations show an improvement on throughput and handoff delay, and consequently the QoS improvement.

Cross-layer Routing Design in Cognitive Radio Networks by Colored Multigraph Model

In this paper, the cross-layer design routing in cognitive radio(CR) networks is studied. We propose a colored multigraph based model for the temporarily available spectrum bands, called spectrum holes in this paper. Based on this colored multigraph model, a polynomial time algorithm with complexity O(n ²) is also proposed to develop a routing and interface assignment, where n is the number of nodes in a CR network. Our algorithm optimizes the hop number of routing, meanwhile, the adjacent hop interference (AHI) is also optimized locally.

Very Low Energy Consumption Wireless Sensor Localization for Danger Environments with Single Mobile Anchor Node

In wireless sensor networks (WSN), it is very important for sensor nodes to locate with low energy consumption and high accuracy, especially in a dangerous environment. This paper describes a range-free layered localization scheme using one mobile anchor node which can transmit gradient signals, and whose moving track is a straight-line along the x-axis. And this paper proposes a sleep/wake mechanism called sensor sleep-time forecasting to save energy consumption during localization. The relationship, between the key factors in localization algorithm and the average location error, is analyzed in detail. Simulation results show that the scheme performs better than other range-free mechanisms—the average location error is less than 0.7 m, and it is independent on sensor nodes density or sensor nodes radio range, the accuracy of the algorithm can be adjusted in different occasions, and the algorithm beacon overhand is small and average localization time is short.

A tabu search heuristic for the routing and wavelength assignment problem in multigranular optical networks

This paper proposes a tabu search heuristic for solving the routing and wavelength assignment problem in multigranular optical networks, considering the wavelength-continuity constraint and a set of connections to satisfy. For a number of fibers per link, a number of wavebands per fiber, and a number of wavelengths per waveband, this algorithm attempts to minimize the total number of ports used in the network by efficiently grouping lightpaths into bands and fibers, and switching the whole bands and fibers. The algorithm has been implemented and tested on the NSFNET network, and comparisons have been made with the Balanced Path Routing and Heavy Traffic First (BPHT) algorithm in terms of number of ports. Generally, the results obtained with our tabu search heuristic are better than those provided by this algorithm.

A dynamic-clustering reactive routing algorithm for wireless sensor networks

The clustering is a key routing method for large-scale wireless sensor networks, which effective extends the lifetime and the expansibility of network. In this paper, a node model is defined based on the structure and transmission principle of neuron, and a dynamic-clustering reactive routing algorithm is proposed. Once the event emergences, the cluster head is dynamic selected in the incident region according to the residual energy. The data collected by the cluster head is sent back to the Sink along the network backbone. Two kinds of accumulation ways are designed to increase the efficiency of data collection. Meanwhile through the fluctuation of action-threshold, the cluster head can trace the changing speed of incident; the nodes outside the incident region use this fluctuation to send data periodically. Finally, the simulation results verify that the DCRR algorithm extends the network’s lifetime considerably and adapts to the change of network scale. The analysis shows that DCRR has more prominent advantages under low and middle load.

Proactive mitigation of impact of wormholes and sinkholes on routing security in energy-efficient wireless sensor networks

Sensor networks are deployed in a variety of environments for unattended operation. In a hostile terrain, sensor nodes are vulnerable to node capture and cryptographic material compromise. Compromised nodes can be used for launching wormhole and sinkhole attacks in order to prevent sensitive data from reaching intended destinations. Our objective in this paper is mitigating the impact of undetected compromised nodes on routing. To this end, we develop metrics for quantifying risk of paths in a network. We then introduce a novel routing approach: Secure-Path Routing (SPR) that uses expected path risk as a parameter in routing. Quantified path risk values are used in routing to reduce traffic flow over nodes that have high expected vulnerability. Selecting low risk routes may lead to the choice of energy-expensive routes. Thus, we develop algorithms for balancing risk with other path selection parameters, including energy consumption. We conduct simulation experiments to evaluate the effectiveness of our approach and study the tradeoff between security and energy. Simulation shows that SPR can be quite effective at increasing traffic flow over legitimate routes and that the impact of SPR on network lifetime is negligible.

Restoration in wavelength-routed optical networks by means of ant colony optimization

Because of the distributed control of the network, the dynamic nature of the traffic and the unpredictability of a failure event, the flexibility and robustness of ant colony optimization (ACO) make it a suitable candidate for provisioning lightpaths in an optical network. In this work, we propose a fault-tolerant dynamic routing and wavelength assignment (RWA) algorithm based on the ACO framework, presenting its integration into the Generalized multi-protocol label switching (GMPLS) control plane. By simulating two different scenarios, we demonstrate the effectiveness of this algorithm when a single link or node failure occurs.

An Efficient Framework for Scalable Defect Isolation in Large Scale Networks of DNA Self-Assembly

This paper proposes and evaluates an approach for defect isolation of DNA self-assembled networks made of a large number of processing nodes. The complexity of DNA self-assembled networks makes impractical to add a large amount of redundancy and employ inefficient and unscalable defect tolerant schemes. A previous framework based on a broadcast algorithm isolates defective nodes without incorporating redundancy for nodes. However, its disadvantage is the limited scalability, thus making it unsuitable for extremely large scale networks built by DNA self-assembly. The proposed framework improves upon the previous framework by involving three algorithmic tiers; namely, 1-hop wave expansion, efficient via placement, and unsafe node detection. The performance of the proposed framework is evaluated and compared with the original framework by considering large scale networks (up to 2,000 × 2,000 nodes), and a novel gross defect model (as well as a conventional random defect model as assumed in previous works). Simulation results indicate that the proposed framework outperforms the original framework in broadcast latency and efficiency and shows excellent scalability for DNA self-assembled nano-scale networks.

A novel online wavelength assignment algorithm in wavelength-convertible multi-granular optical networks

As industrial technology gets more mature, a single fiber can offer more and more wavelengths. However, it also results in a large amount of switching ports at optical cross-connects (OXCs). Certainly, it is expected that higher and higher complexity is inevitable to control and manage such large OXCs. In this paper, we study the dynamic wavelength assignment problem in waveband switching (WBS) networks composed of multi-granular OXCs (MG-OXCs). Moreover, in order to relax the wavelength continuity constraint on lightpath establishments, each MG-OXC node is equipped with a certain number of converters. To efficiently minimize the extra port consumption and utilize wavelength converters, we proposed an online wavelength assignment algorithm named Least Weighted Configuration Cost (LWCC). For a new request, LWCC first adopts fixed routing and then exploits the layered-graph approach and a new cost function for edge weight assignment to determine adequate wavelength(s). The performance metrics of interest include both blocking performance and converter utilization. Numerical results show that LWCC is superior in waveband grouping and therefore results in significant performance gain in terms of blocking probability.

Energy Efficient Non-uniform Clustering Division Scheme in Wireless Sensor Networks

Wireless sensor networks can be used to monitor the interested region by multi-hop communication. Since sensor nodes are equipped with energy-limited batteries, energy conservation in such networks is of paramount importance in order to prolong the network lifetime. In this paper, considering the constrained radio range of node, we propose an energy efficient clustering division scheme from the viewpoint of energy consumption. The difference between our scheme and previous schemes is that ours is a non-uniform clustering hierarchy. With the algorithm that is proposed by this paper, we can divide the cluster into multiple non-uniform concentric rings and obtain the optimal thickness of each ring. Motivated by the derived results, every sensor node can adjust its radio range for transmission. Our extensive simulation results indicate that the proposed non-uniform clustering division scheme outperforms the conventional uniform clustering division schemes in terms of energy consumption and lifetime. The future research that should be explored is also discussed finally.

Routing scalability in multi-domain DWDM networks

This paper studies routing scalability in multi-domain DWDM networks. Although inter-domain provisioning has been well studied for packet/cell-switching networks, the wavelength dimension (along with wavelength conversion) poses many challenges in multi-domain DWDM settings. To address these concerns a detailed GMPLS-based hierarchical routing framework is proposed for multi-domain DWDM networks with wavelength conversion. This solution uses mesh topology abstraction schemes to hide domain-internal state. However related inter-domain routing loads can be significant here, growing by the square of the number of border nodes. To address these scalability limitations, improved inter-domain routing update strategies are also proposed and the associated performance of inter-domain lightpath RWA and signaling schemes studied.