Showing papers on "Hazy Sighted Link State Routing Protocol published in 2009"

A case for bufferless routing in on-chip networks

Abstract: Buffers in on-chip networks consume significant energy, occupy chip area, and increase design complexity. In this paper, we make a case for a new approach to designing on-chip interconnection networks that eliminates the need for buffers for routing or flow control. We describe new algorithms for routing without using buffers in router input/output ports. We analyze the advantages and disadvantages of bufferless routing and discuss how router latency can be reduced by taking advantage of the fact that input/output buffers do not exist. Our evaluations show that routing without buffers significantly reduces the energy consumption of the on-chip cache/processor-to-cache network, while providing similar performance to that of existing buffered routing algorithms at low network utilization (i.e., on most real applications). We conclude that bufferless routing can be an attractive and energy-efficient design option for on-chip cache/processor-to-cache networks where network utilization is low.

SOAR: Simple Opportunistic Adaptive Routing Protocol for Wireless Mesh Networks

Abstract: Multihop wireless mesh networks are becoming a new attractive communication paradigm owing to their low cost and ease of deployment. Routing protocols are critical to the performance and reliability of wireless mesh networks. Traditional routing protocols send traffic along predetermined paths and face difficulties in coping with unreliable and unpredictable wireless medium. In this paper, we propose a simple opportunistic adaptive routing protocol (SOAR) to explicitly support multiple simultaneous flows in wireless mesh networks. SOAR incorporates the following four major components to achieve high throughput and fairness: 1) adaptive forwarding path selection to leverage path diversity while minimizing duplicate transmissions, 2) priority timer-based forwarding to let only the best forwarding node forward the packet, 3) local loss recovery to efficiently detect and retransmit lost packets, and 4) adaptive rate control to determine an appropriate sending rate according to the current network conditions. We implement SOAR in both NS-2 simulation and an 18-node wireless mesh testbed. Our extensive evaluation shows that SOAR significantly outperforms traditional routing and a seminal opportunistic routing protocol, ExOR, under a wide range of scenarios.

HOPNET: A hybrid ant colony optimization routing algorithm for mobile ad hoc network

Abstract: Mobile ad hoc network (MANET) is a group of mobile nodes which communicates with each other without any supporting infrastructure. Routing in MANET is extremely challenging because of MANETs dynamic features, its limited bandwidth and power energy. Nature-inspired algorithms (swarm intelligence) such as ant colony optimization (ACO) algorithms have shown to be a good technique for developing routing algorithms for MANETs. Swarm intelligence is a computational intelligence technique that involves collective behavior of autonomous agents that locally interact with each other in a distributed environment to solve a given problem in the hope of finding a global solution to the problem. In this paper, we propose a hybrid routing algorithm for MANETs based on ACO and zone routing framework of bordercasting. The algorithm, HOPNET, based on ants hopping from one zone to the next, consists of the local proactive route discovery within a node's neighborhood and reactive communication between the neighborhoods. The algorithm has features extracted from ZRP and DSR protocols and is simulated on GlomoSim and is compared to AODV routing protocol. The algorithm is also compared to the well known hybrid routing algorithm, AntHocNet, which is not based on zone routing framework. Results indicate that HOPNET is highly scalable for large networks compared to AntHocNet. The results also indicate that the selection of the zone radius has considerable impact on the delivery packet ratio and HOPNET performs significantly better than AntHocNet for high and low mobility. The algorithm has been compared to random way point model and random drunken model and the results show the efficiency and inefficiency of bordercasting. Finally, HOPNET is compared to ZRP and the strength of nature-inspired algorithm is shown.

Load management in wireless mesh communications networks

Abstract: Methods and systems for providing a network and routing protocol for utility services are disclosed. A method includes discovering a utility network. Neighboring nodes are discovered and the node listens for advertised routes for networks from the neighbors. The node is then registered with one or more utility networks, receiving a unique address for each network registration. Each upstream node can independently make forwarding decisions on both upstream and downstream packets, i.e., choose the next hop according to the best information available to it. The node can sense transient link problems, outage problems and traffic characteristics. Information is used to find the best route out of and within each network. Each network node maintains multi-egress, multi-ingress network routing options both for itself and the node(s) associated with it. The node is capable of several route maintenance functions utilizing the basic routing protocol and algorithms.

A system and method for implementing mesh network communications using a mesh network protocol

Abstract: The following describes data structures, communication protocol formats and process flows for controlling and facilitating secure communications between the nodes of a mesh network, such as utility meters and gateway nodes comprising a utility network. The enabled processes include association, information exchange, route discovery and maintenance and the like for instituting and maintaining a secure mesh network.

Practical, distributed channel assignment and routing in dual-radio mesh networks

Abstract: Realizing the full potential of a multi-radio mesh network involves two main challenges: how to assign channels to radios at each node to minimize interference and how to choose high throughput routing paths in the face of lossy links, variable channel conditions and external load. This paper presents ROMA, a practical, distributed channel assignment and routing protocol that achieves good multi-hop path performance between every node and one or more designated gateway nodes in a dual-radio network. ROMA assigns non-overlapping channels to links along each gateway path to eliminate intra-path interference. ROMA reduces inter-path interference by assigning different channels to paths destined for different gateways whenever possible. Evaluations on a 24-node dual-radio testbed show that ROMA achieves high throughput in a variety of scenarios.

Multirate Anypath Routing in Wireless Mesh Networks

Abstract: In this paper, we present a new routing paradigm that generalizes opportunistic routing in wireless mesh networks. In multirate anypath routing, each node uses both a set of next hops and a selected transmission rate to reach a destination. Using this rate, a packet is broadcast to the nodes in the set and one of them forwards the packet on to the destination. To date, there is no theory capable of jointly optimizing both the set of next hops and the transmission rate used by each node. We bridge this gap by introducing a polynomial-time algorithm to this problem and provide the proof of its optimality. The proposed algorithm runs in the same running time as regular shortest-path algorithms and is therefore suitable for deployment in link-state routing protocols. We conducted experiments in a 802.11b testbed network, and our results show that multirate anypath routing performs on average 80% and up to 6.4 times better than anypath routing with a fixed rate of 11 Mbps. If the rate is fixed at 1 Mbps instead, performance improves by up to one order of magnitude. I. INTRODUCTION The high loss rate and dynamic quality of links make routing in wireless mesh networks extremely challenging (1). Anypath routing 1 has been recently proposed as a way to circumvent these shortcomings by using multiple next hops for each destination (3)-(6). Each packet is broadcast to a forwarding set composed of several neighbors, and the packet must be retransmitted only if none of the neighbors in the set receive it. Therefore, while the link to a given neighbor is down or performing poorly, another nearby neighbor may receive the packet and forward it on. This is in contrast to single-path routing where only one neighbor is assigned as the next hop for each destination. In this case, if the link to this neighbor is not performing well, a packet may be lost even though other neighbors may have overheard it. Existing work on anypath routing has focused on wireless networks that use a single transmission rate. This approach, albeit straightforward, presents two major drawbacks. First, using a single rate over the entire network underutilizes available bandwidth resources. Some links may perform well at a higher rate, while others may only work at a lower rate. Secondly and most importantly, the network may become disconnected at a higher bit rate. We provide experimental measurements from a 802.11b testbed which show that this phenomenon is not uncommon in practice. The key problem is that higher transmission rates have a shorter radio range, which reduces network density and connectivity. As the bit rate in- creases, links becomes lossier and the network eventually gets disconnected. Therefore, in order to guarantee connectivity, single-rate anypath routing must be limited to low rates. In multirate anypath routing, these problems do not exist; however, we face different challenges. First, we must find 1 We use the term anypath rather than opportunistic routing, since oppor- tunistic routing is an overloaded term also used for opportunistic contacts (2).

Comparison of two routing metrics in OLSR on a grid based mesh network

Abstract: Predicting the performance of ad hoc networking protocols for mesh networks has typically been performed by making use of software based simulation tools. Experimental study and validation of such predictions is a vital to obtaining more realistic results, but may not be possible under the constrained environment of network simulators. This paper presents an experimental comparison of OLSR using the standard hysteresis routing metric and the ETX metric in a 7 by 7 grid of closely spaced Wi-Fi nodes to obtain more realistic results. The wireless grid is first modelled to extract its ability to emulate a real world multi-hop ad hoc network. This is followed by a detailed analysis of OLSR in terms of hop count, routing traffic overhead, throughput, delay, packet loss and route flapping in the wireless grid using the hysteresis and ETX routing metric. It was discovered that the ETX metric which has been extensively used in mesh networks around the world is fundamentally flawed when estimating optimal routes in real mesh networks and that the less sophisticated hysteresis metric shows better performance in large dense mesh networks.

Energy Efficient Location Aided Routing Protocol for Wireless MANETs

Abstract: A Mobile Ad-Hoc Network (MANET) is a collection of wireless mobile nodes forming a temporary network without using any centralized access point, infrastructure, or centralized administration. In this paper we introduce an Energy Efficient Location Aided Routing (EELAR) Protocol for MANETs that is based on the Location Aided Routing (LAR). EELAR makes significant reduction in the energy consumption of the mobile nodes batteries by limiting the area of discovering a new route to a smaller zone. Thus, control packets overhead is significantly reduced. In EELAR a reference wireless base station is used and the network's circular area centered at the base station is divided into six equal sub-areas. At route discovery instead of flooding control packets to the whole network area, they are flooded to only the sub-area of the destination mobile node. The base station stores locations of the mobile nodes in a position table. To show the efficiency of the proposed protocol we present simulations using NS-2. Simulation results show that EELAR protocol makes an improvement in control packet overhead and delivery ratio compared to AODV, LAR, and DSR protocols.

Enhanced tree routing for wireless sensor networks

Abstract: Tree routing (TR) is a low-overhead routing protocol designated for simple, low-cost and low-power wireless sensor networks. It avoids flooding the network with path search and update messages in order to conserve bandwidth and energy by using only parent-child links for packet forwarding. The major drawback of TR is the increased hop-counts as compared with more sophisticated path search protocols. We propose an enhanced tree routing (ETR) strategy for sensor networks which have structured node address assignment schemes. In addition to the parent-child links, ETR also uses links to other one-hop neighbours if it is decided that this will lead to a shorter path. It is shown that such a decision can be made with minimum storage and computing cost by utilizing the address structure. Detailed algorithms for applying ETR to ZigBee networks are also presented. Simulation results reveal that ETR not only outperforms TR in terms of hop-counts, but also is more energy-efficient than TR.

A genetic approach to joint routing and link scheduling for wireless mesh networks

Abstract: Wireless mesh networks are an attractive technology for providing broadband connectivity to mobile clients who are just on the edge of wired networks, and also for building self-organized networks in places where wired infrastructures are not available or not deemed to be worth deploying. This paper investigates the joint link scheduling and routing issues involved in the delivery of a given backlog from any node of a wireless mesh network towards a specific node (which acts as a gateway), within a given deadline. Scheduling and routing are assumed to be aware of the physical interference among nodes, which is modeled in the paper by means of a signal-to-interference ratio. Firstly, we present a theoretical model which allows us to formulate the task of deriving joint routing and scheduling as an integer linear programming problem. Secondly, since the problem cannot be dealt with using exact methods, we propose and use a technique based on genetic algorithms. To the best of our knowledge, these algorithms have never been used before for working out these kinds of optimization problems in a wireless mesh environment. We show that our technique is suitable for this purpose as it provides a good trade-off between fast computation and the overall goodness of the solution found. Our experience has in fact shown that genetic algorithms would seem to be quite promising for solving more complex models than the one dealt with in this paper, such as those including multiple flows and multi-radio multi-channels.

Interference-aware QoS routing for multi-rate multi-radio multi-channel IEEE 802.11 wireless mesh networks

Abstract: QoS routing in multi-channel wireless mesh networks (WMNs) with contention-based MAC protocols is a very challenging problem. In this paper, we propose an on-demand bandwidth-constrained routing protocol for multi-radio multi-rate multi-channel WMNs with the IEEE 802.11 DCF MAC protocol. The routing protocol is based on a distributed threshold-triggered bandwidth estimation scheme, implemented at each node for estimating the free-to-use bandwidth on each associated channel. According to the free-to-use bandwidth at each node, the call admission control, which is integrated into the routing protocol, predicts the residual bandwidth of a path with the consideration of inter-flow and intra-flow interference. To select the most efficient path among all feasible ones, we propose a routing metric which strikes a balance between the cost and the bandwidth of the path. The simulation results show that our routing protocol can successfully discover paths that meet the end-to-end bandwidth requirements of flows, protect existing flows from QoS violations, exploit the capacity gain due to multiple channels, and incurs low message overhead.

Small-Scale and Large-Scale Routing in Vehicular Ad Hoc Networks

Abstract: A vehicular ad hoc network (VANET) is a highly mobile wireless ad hoc network that is targeted to support vehicular safety, traffic monitoring, and other applications. Mobility models used in traditional mobile ad hoc networks cannot directly be applied to VANETs since real-world factors such as road layouts and traffic regulations are not considered. In this paper, we propose a vehicular mobility model that reflects real-world vehicle movement and study the performance of packet-routing protocols. First, we study the routing in small-scale VANETs and propose two routing schemes: (1) connection-based restricted forwarding (CBRF) and (2) connectionless geographic forwarding (CLGF). With the insights obtained, we consider routing in large-scale VANETs. Since road complexity and traffic variety may cause many potential problems that existing routing protocols cannot address, we introduce a two-phase routing protocol (TOPO) that incorporates road map information. The proposed protocol defines an overlay graph with roads of high vehicular density and access graphs that are connected to the overlay. While in the overlay, packets are forwarded along a precalculated path. As far as access routing is concerned, we employ the aforementioned CBRF and CLGF schemes and send packets to the overlay or handle packets delivered from the overlay. We argue that the TOPO can serve as a framework that integrates existing VANET routing protocols. We also consider data diversity in VANETs and design the TOPO as an intelligent transportation system (ITS)-friendly protocol. To validate our design philosophy and the routing protocol, we use different areas in the city of Orlando, FL, and generate vehicular mobility traces, following our mobility models. We feed the traces to network simulators and study the routing behavior. Simulation results demonstrate the performance and effectiveness of the proposed routing protocols for large-scale VANET scenarios.

Load-balancing in MANET shortest-path routing protocols

Abstract: Mobile ad hoc networks (MANET) are infrastructure-less networks, dynamically formed by an independent system of mobile nodes that are connected via wireless links. Because routing is performed by nodes with limited resources, load should be efficiently distributed through the network. Otherwise, heavily-loaded nodes may make up a bottleneck that lowers the network performances by congestion and larger delays. Regrettably, load-balancing is a critical deficiency in MANET shortest-path routing protocols, as nodes at the center of the network are much heavily-loaded than the others. Thus, we propose, in this paper, load-balancing mechanisms that push the traffic further from the center of the network. Basically, we provide novel routing metrics that take into account nodes degree of centrality, for both proactive and reactive routing protocols. Simulations show that the proposed mechanisms improve the load distribution and significantly enhance the network performances in terms of average delay and reliability.

Joint routing and link rate allocation under bandwidth and energy constraints in sensor networks

Abstract: In sensor networks, both energy and bandwidth are scarce resources. In the past, many energy efficient routing algorithms have been devised in order to maximize network lifetime, in which wireless link bandwidth has been optimistically assumed to be sufficient. This article shows that ignoring the bandwidth constraint can lead to infeasible routing solutions. As energy constraint affects how data should be routed, link bandwidth also affects not only the routing topology but also the allowed data rate on each link. In this paper, we discuss the sufficient condition on link bandwidth that makes a routing solution feasible, then provide mathematical optimization models to tackle both energy and bandwidth constraints.We first present a basic mathematical model to address using uniform transmission power for routing without data aggregation, then extend it to handle nonuniform transmission power, and then routing with data aggregation. We propose two efficient heuristics to compute the routing topology and link data rate. Simulation results show that these heuristics provide more feasible routing solutions than previous work, and provide significant improvement on throughput and lifetime.

Implementation of Gradient Routing in Wireless Sensor Networks

Abstract: IETF ROLL has recently proposed gradient routing as a fundamental building block for data collection in Wireless Sensor Networks. This paper seconds this choice by presenting an implementation of gradient routing on current hardware, and by showing experimentally that gradient routing is robust against topological changes. To stress its self-healing quality, we design and implement a complete communication stack in which neighbor tables are built in a purely reactive fashion. We quantify the resulting topological changes, and show how gradient routing elegantly handles these dynamics. This paper presents, to the best of our knowledge, the first experimental study on gradient routing as advocated by IETF ROLL.

ARMR: Anonymous routing protocol with multiple routes for communications in mobile ad hoc networks

Abstract: A mobile ad hoc network consists of mobile nodes that communicate in an open wireless medium. Adversaries can launch analysis against the routing information embedded in the routing message and data packets to detect the traffic pattern of the communications, thereby obtaining sensitive information of the system, such as the identity of a critical node. In order to thwart such attacks, anonymous routing protocols are developed. For the purposes of security and robustness, an ideal anonymous routing protocol should hide the identities of the nodes in the route, in particular, those of the source and the destination. Multiple routes should be established to increase the difficulty of traffic analysis and to avoid broken paths due to node mobility. Existing schemes either make the unrealistic and undesired assumption that certain topological information about the network is known to the nodes, or cannot achieve all the properties described in the above. In this paper, we propose an anonymous routing protocol with multiple routes called ARMR, which can satisfy all the required properties. In addition, the protocol has the flexibility of creating fake routes to confuse the adversaries, thus increasing the level of anonymity. In terms of communication efficiency, extensive simulation is carried out. Compared with AODV and MASK, our ARMR protocol gives a higher route request success rate under all situations and the delay of our protocol is comparable to the best of these two protocols.

J-CAR: An efficient joint channel assignment and routing protocol for IEEE 802.11-based multi-channel multi-interface mobile Ad Hoc networks

Abstract: The capacity of an IEEE 802.11-based multi-hop wireless network is limited. By effectively utilizing multiple non-overlapping channels and multiple interfaces, collision and co-channel interference can be reduced. This allows more concurrent transmissions and thus enhances the network capacity. In this paper, we introduce an efficient distributed joint channel assignment and routing protocol, called J-CAR. Unlike existing schemes, J-CAR allows a data interface to dynamically change its routing protocol working mode between send and receive on a call-by-call basis, which distributed joint channel assignment enhances the utilization of both interface and channel. In J-CAR, channels are negotiated and assigned to active links in conjunction with the on-demand routing process. At each hop, J-CAR conducts a local optimization by selecting the least interfered channel according to the channel interference index. The channel interference index is designed by taking both the protocol and physical interference models into consideration. To find the least interfered path for network load balancing on a global scale, J-CAR employs a length-constrained widest-path routing. The ldquowidthrdquo of a path is determined by the interference level of its bottleneck link. With an adjustable threshold on the path length (with respect to the shortest-path), the excessively long path can also be avoided. We show that with a comparable complexity as the existing schemes, J-CAR provides much higher system good puts and shorter end-to-end packet delays.

Parallel Opportunistic Routing in Wireless Networks

Abstract: We study benefits of opportunistic routing in a large wireless ad hoc network by examining how the power, delay, and total throughput scale as the number of source- destination pairs increases up to the operating maximum. Our opportunistic routing is novel in a sense that it is massively parallel, i.e., it is performed by many nodes simultaneously to maximize the opportunistic gain while controlling the inter-user interference. The scaling behavior of conventional multi-hop transmission that does not employ opportunistic routing is also examined for comparison. Our results indicate that our opportunistic routing can exhibit a net improvement in overall power--delay trade-off over the conventional routing by providing up to a logarithmic boost in the scaling law. Such a gain is possible since the receivers can tolerate more interference due to the increased received signal power provided by the multi-user diversity gain, which means that having more simultaneous transmissions is possible.

Routing metrics for Wireless Mesh Networks

Abstract: Routing in wireless mesh networks has been an active area of research for many years, with many proposed routing protocols selecting shortest paths that minimize the path hop count. Whereas minimum hop count is the most popular metric in wired networks, in wireless networks interference- and energy- related considerations give rise to more complex trade-offs. Therefore, a variety of routing metrics has been proposed especially for wireless mesh networks providing routing algorithms with high flexibility in the selection of best path as a compromise among throughput, end-to-end delay, and energy consumption. In this paper, we present a detailed survey and taxonomy of routing metrics. These metrics may have broadly different optimization objectives (e.g., optimize application performance, maximize battery lifetime, maximize network throughput), different methods to collect the required information to produce metric values, and different ways to derive the end-to-end route quality out of the individual link quality metrics. The presentation of the metrics is highly comparative, with emphasis on their strengths and weaknesses and their application to various types of network scenarios. We also discuss the main implications for practitioners and identify open issues for further research in the area.

A Taxonomy of Routing Protocols for Mobile Ad Hoc Networks

Abstract: This chapter contains sections titled: Introduction Ad Hoc Networks Applications Design Issues Ad Hoc Networks Routing Protocols Conclusions Exercises References

Probabilistic counter-based route discovery for mobile ad hoc networks

Abstract: Conventional on-demand route discovery for ad hoc routing protocols extensively use simple flooding, which could potentially lead to high channel contention, causing redundant retransmissions and thus excessive packet collisions in the network. This phenomenon has been shown to greatly increase the network communication overhead and end to end delay. This paper proposes a new probabilistic counter-based method that can significantly reduce the number of RREQ packets transmitted during route discovery operation. Our simulation results reveal that equipping AODV routing protocol with the proposed probabilistic counter-based route discovery method can result in significant performance improvements in terms of routing overhead, MAC collisions and end-to-end delay while still achieving a good throughput.

Network utilities in wireless mesh communications networks

Abstract: Methods and systems for providing a network and routing protocol for utility services are disclosed. A method includes discovering a utility network. Neighboring nodes are discovered and the node listens for advertised routes for networks from the neighbors. The node is then registered with one or more utility networks, receiving a unique address for each network registration. Each upstream node can independently make forwarding decisions on both upstream and downstream packets, i.e., choose the next hop according to the best information available to it. The node can sense transient link problems, outage problems and traffic characteristics. Information is used to find the best route out of and within each network. Each network node maintains multi-egress, multi-ingress network routing options both for itself and the node(s) associated with it. The node is capable of several route maintenance functions utilizing the basic routing protocol and algorithms.

Convex Partition of Sensor Networks and Its Use in Virtual Coordinate Geographic Routing

Abstract: Virtual coordinate geographic routing is an appeal- ing geographic routing approach for its ability to work without physical location information. We examine two representative such routing protocols, namely NoGeo and BVR, and show through experiments and theoretical analysis their limitation in adapting to complex field topologies, in particular fields with concave holes. Based on the new insights, we propose a distributed convex partition protocol that divides the field to subareas with convex shapes, using only connectivity information. A new geographic routing protocol, called CONVEX, that builds upon the partitioning protocol is then described. Simulations demonstrate significant performance improvement of the new routing protocol over NoGeo and BVR, in terms of transmission stretch and maintenance overheads. I. INTRODUCTION

Distributed potential field based routing and autonomous load balancing for wireless mesh networks

Abstract: Congested hot spots and node failures severely degrade the performance of wireless mesh networks. However, conventional routing schemes are inefficient in mitigation of the problems. Considering analogy to physics, we propose a novel distributed potential-field-based routing scheme for anycast wireless mesh networks, which is robust to sudden traffic and network perturbations, effectively balancing load among multiple gateways and mesh nodes with little control overhead. Simulation results exhibit autonomous load balancing and failure-tolerant performance in wireless mesh networking.

EAMTR: Energy aware multi-tree routing for wireless sensor networks

Abstract: IEEE 802.15.4 is the prevailing standard for low-rate wireless personal area networks. It specifies the physical layer and medium access control sub-layer. Some emerging standards such as ZigBee define the network layer on top of these lower levels to support routing and multi-hop communication. Tree routing is a favourable basis for ZigBee routing because of its simplicity and limited use of resources. However, in data collection systems that are based on spanning trees rooted at a sink node, non-optimal route selection, congestion and uneven distribution of traffic in tree routing can adversely contribute to network performance and lifetime. The imbalance in workload can result in hotspot problems and early energy depletion of specific nodes that are normally the crucial routers of the network. The authors propose a novel light-weight routing protocol, energy aware multi-tree routing (EAMTR) protocol, to balance the workload of data gathering and alleviate the hotspot and single points of failure problems for high-density sink-type networks. In this scheme, multiple trees are formed in the initialisation phase and according to network traffic, each node selects the least congested route to the root node. The results of simulation and performance evaluation of EAMTR show significant improvement in network lifetime and traffic distribution.

Node discovery and culling in wireless mesh communications networks

Abstract: Methods and systems for providing a network and routing protocol for utility services are disclosed. A method includes discovering a utility network. Neighboring nodes are discovered and the node listens for advertised routes for networks from the neighbors. The node is then registered with one or more utility networks, receiving a unique address for each network registration. Each upstream node can independently make forwarding decisions on both upstream and downstream packets, i.e., choose the next hop according to the best information available to it. The node can sense transient link problems, outage problems and traffic characteristics. Information is used to find the best route out of and within each network. Each network node maintains multi-egress, multi-ingress network routing options both for itself and the node(s) associated with it. The node is capable of several route maintenance functions utilizing the basic routing protocol and algorithms.

Impact of Social Networks on Delay Tolerant Routing

Abstract: Delay Tolerant Networks (DTNs) are wireless networks in which at any given time instance, the probability of having a complete path from a source to destination is low due to the intermittent connectivity between nodes. Several routing schemes have been proposed for such networks to make the delivery of messages possible despite the intermittent connections. In this paper, in addition to intermittent connectivity which impacts routing most strongly, we also analyze the effects of underlying social structure over the communication network. In a social network, nodes interact in diverse ways so that some nodes meet each other more frequently than others. In the paper, we first propose a new network model to reflect the underlying social structure over the network nodes, then we study the effects of this model on the performance of multi-copy based routing algorithms. We also analyze the performance of routing and validate our analysis with simulations.

An Improvement of LEACH Routing Protocol Based on Trust for Wireless Sensor Networks

Abstract: LEACH is a hierarchy routing protocol for WSN (wireless sensor networks), which is superior to direct communication protocol, minimum-transmission-energy protocol and static clustering protocol. However, LEACH itself has some defects. In this paper LEACH-TM introduces the concept of Trust, designs the cluster-head adjusting procedure and establishes multi-path with cluster-heads acting as routers. The simulation illustrates that LEACH-TM makes much progress in the reliability of data transmission, the distribution of cluster heads and the lifetime of networks.