Showing papers on "Geographic routing published in 2007"

Social network analysis for routing in disconnected delay-tolerant MANETs

Abstract: Message delivery in sparse Mobile Ad hoc Networks (MANETs) is difficult due to the fact that the network graph is rarely (if ever) connected. A key challenge is to find a route that can provide good delivery performance and low end-to-end delay in a disconnected network graph where nodes may move freely. This paper presents a multidisciplinary solution based on the consideration of the so-called small world dynamics which have been proposed for economy and social studies and have recently revealed to be a successful approach to be exploited for characterising information propagation in wireless networks. To this purpose, some bridge nodes are identified based on their centrality characteristics, i.e., on their capability to broker information exchange among otherwise disconnected nodes. Due to the complexity of the centrality metrics in populated networks the concept of ego networks is exploited where nodes are not required to exchange information about the entire network topology, but only locally available information is considered. Then SimBet Routing is proposed which exploits the exchange of pre-estimated "betweenness' centrality metrics and locally determined social "similarity' to the destination node. We present simulations using real trace data to demonstrate that SimBet Routing results in delivery performance close to Epidemic Routing but with significantly reduced overhead. Additionally, we show that SimBet Routing outperforms PRoPHET Routing, particularly when the sending and receiving nodes have low connectivity.

Connectivity-Aware Routing (CAR) in Vehicular Ad-hoc Networks

Abstract: Vehicular ad hoc networks using WLAN technology have recently received considerable attention. We present a position-based routing scheme called Connectivity-Aware Routing (CAR) designed specifically for inter-vehicle communication in a city and/or highway environment. A distinguishing property of CAR is the ability to not only locate positions of destinations but also to find connected paths between source and destination pairs. These paths are auto-adjusted on the fly, without a new discovery process. "Guards" help to track the current position of a destination, even if it traveled a substantial distance from its initially known location. For the evaluation of the CAR protocol we use realistic mobility traces obtained from a microscopic vehicular traffic simulator that is based on a model of driver behavior and the real road maps of Switzerland.

An Acknowledgment-Based Approach for the Detection of Routing Misbehavior in MANETs

Abstract: We study routing misbehavior in MANETs (mobile ad hoc networks) in this paper. In general, routing protocols for MANETs are designed based on the assumption that all participating nodes are fully cooperative. However, due to the open structure and scarcely available battery-based energy, node misbehaviors may exist. One such routing misbehavior is that some selfish nodes will participate in the route discovery and maintenance processes but refuse to forward data packets. In this paper, we propose the 2ACK scheme that serves as an add-on technique for routing schemes to detect routing misbehavior and to mitigate their adverse effect. The main idea of the 2ACK scheme is to send two-hop acknowledgment packets in the opposite direction of the routing path. In order to reduce additional routing overhead, only a fraction of the received data packets are acknowledged in the 2ACK scheme. Analytical and simulation results are presented to evaluate the performance of the proposed scheme

Geographic Routing Using Hyperbolic Space

Abstract: We propose a scalable and reliable point-to-point routing algorithm for ad hoc wireless networks and sensor-nets. Our algorithm assigns to each node of the network a virtual coordinate in the hyperbolic plane, and performs greedy geographic routing with respect to these virtual coordinates. Unlike other proposed greedy routing algorithms based on virtual coordinates, our embedding guarantees that the greedy algorithm is always successful in finding a route to the destination, if such a route exists. We describe a distributed algorithm for computing each node's virtual coordinates in the hyperbolic plane, and for greedily routing packets to a destination point in the hyperbolic plane. (This destination may be the address of another node of the network, or it may be an address associated to a piece of content in a Distributed Hash Table. In the latter case we prove that the greedy routing strategy makes a consistent choice of the node responsible for the address, irrespective of the source address of the request.) We evaluate the resulting algorithm in terms of both path stretch and node congestion.

Practical Routing in Delay-Tolerant Networks

Abstract: Delay-tolerant networks (DTNs) have the potential to interconnect devices in regions that current networking technology cannot reach. To realize the DTN vision, routes must be found over multiple unreliable, intermittently-connected hops. In this paper we present a practical routing protocol that uses only observed information about the network. We designed a metric that estimates the average waiting time for each potential next hop. This learned topology information is distributed using a link-state routing protocol, where the link-state packets are "flooded" using epidemic routing. The routing is recomputed each time connections are established, allowing messages to take advantage of unpredictable contacts. A message is forwarded if the topology suggests that the connected node is "closer" to the destination than the current node. We demonstrate through simulation that our protocol provides performance similar to that of schemes that have global knowledge of the network topology, yet without requiring that knowledge. Further, it requires significantly less resources than the alternative, epidemic routing, suggesting that our approach scales better with the number of messages in the network. This performance is achieved with minimal protocol overhead for networks of approximately 100 nodes.

HiBOp: a History Based Routing Protocol for Opportunistic Networks

Abstract: In opportunistic networks the existence of a simultaneous path between a sender and a receiver is not assumed. This model (which fits well to pervasive networking environments) completely breaks the main assumptions on which MANET routing protocols are built. Routing in opportunistic networks is usually based on some form of controlled flooding. But often this results in very high resource consumption and network congestion. In this paper we advocate context-based routing for opportunistic networks. We provide a general framework for managing and using context for taking forwarding decisions. We propose a context-based protocol (HiBOp), and compare it with popular solutions, i.e., Epidemic Routing and PROPHET. Results show that HiBOp is able to drastically reduce resource consumption. At the same time, it significantly reduces the message loss rate, and preserves the performance in terms of message delay.

Asymptotically optimal energy-aware routing for multihop wireless networks with renewable energy sources

Abstract: In this paper, we develop a model to characterize the performance of multihop radio networks in the presence of energy constraints and design routing algorithms to optimally utilize the available energy. The energy model allows us to consider different types of energy sources in heterogeneous environments. The proposed algorithm is shown to achieve a competitive ratio (i.e., the ratio of the performance of any offline algorithm that has knowledge of all past and future packet arrivals to the performance of our online algorithm) that is asymptotically optimal with respect to the number of nodes in the network. The algorithm assumes no statistical information on packet arrivals and can easily be incorporated into existing routing schemes (e.g., proactive or on-demand methodologies) in a distributed fashion. Simulation results confirm that the algorithm performs very well in terms of maximizing the throughput of an energy-constrained network. Further, a new threshold-based scheme is proposed to reduce the routing overhead while incurring only minimum performance degradation.

A Distributed Joint Channel-Assignment, Scheduling and Routing Algorithm for Multi-Channel Ad-hoc Wireless Networks

Abstract: The capacity of ad hoc wireless networks can be substantially increased by equipping each network node with multiple radio interfaces that can operate on multiple non-overlapping channels. However, new scheduling, channel-assignment, and routing algorithms are required to fully utilize the increased bandwidth in multi-channel multi-radio ad hoc networks. In this paper, we develop a fully distributed algorithm that jointly solves the channel-assignment, scheduling and routing problem. Our algorithm is an online algorithm, i.e., it does not require prior information on the offered load to the network, and can adapt automatically to the changes in the network topology and offered load. We show that our algorithm is provably efficient. That is, even compared with the optimal centralized and offline algorithm, our proposed distributed algorithm can achieve a provable fraction of the maximum system capacity. Further, the achievable fraction that we can guarantee is larger than that of some other comparable algorithms in the literature.

Joint On-Demand Routing and Spectrum Assignment in Cognitive Radio Networks

Abstract: In cognitive radio networks, nodes can work on different frequency bands. Existing routing proposals help nodes select frequency bands without considering the effect of band switching and intra-band backoff. In this paper, We propose a joint interaction between on-demand routing and spectrum scheduling. A node analytical model is proposed to describe the scheduling-based channel assignment progress, which relief the inter-flow interference and frequent switching delay. We also use an on-demand interaction to derive a cumulative delay based routing protocol. Simulation results show that, comparing to other approaches, our protocol provides better adaptability to the multi- flow environment and derives paths with much lower cumulative delay.

A survey of void handling techniques for geographic routing in wireless networks

Abstract: Communications voids, where geographic greedy forwarding fails to move a packet further towards its destination, are an important issue for geographic routing in wireless networks. This article presents an overview of the void problem and surveys the currently available void-handling techniques (as of July 2006) for geographic routing. In the survey, we classify these void-handling techniques into six categories, each designed with a different approach, that is, planar-graph-based, geometric, flooding-based, costbased, heuristic, and hybrid. For each category, we present its basic principle and illustrate some classic techniques as well as the latest advances. We also provide a qualitative comparison of these techniques and discuss some possible directions of future research.

Enhanced Perimeter Routing for Geographic Forwarding Protocols in Urban Vehicular Scenarios

Abstract: Geographic stateless routing schemes such as GPSR have been widely adopted to routing in vehicular ad hoc networks (VANET). However, due to the particular urban topology and the non-uniform distribution of cars, the greedy routing mode often fails and needs a recovery strategy such as GPSR's perimeter mode to deliver data successfully to the destination. It has been shown that the cost of planarization, the non-uniform distribution of cars, and radio obstacles make GPSR's perimeter mode inefficient in urban configurations. Some enhancements have been proposed such as GPCR, which uses the concept of junction nodes to control the next road segments that packets should follow. However, the concept of junction nodes itself is problematic and hard to maintain in a dynamic urban environment. In this paper, we describe GpsrJ+, a solution that further improves the packet delivery ratio of GPCR with minimal modification by predicting on which road segment its neighboring junction node will forward packets to. GpsrJ+ differs from GPCR as decisions about which road segment to turn does not need to be made by junction nodes. Moreover, GpsrJ+ does not need an expensive planarization strategy since it uses the natural planar feature of urban maps. Consequently, GpsrJ+ reduces the hop count used in the perimeter mode by as much as 200% compared to GPSR. It therefore allows geographic routing schemes to return to the greedy mode faster.

The design and implementation of a declarative sensor network system

Abstract: Sensor networks are notoriously difficult to program, given that they encompass the complexities of both distributed and embedded systems. To address this problem, we present the design and implementation of a declarative sensor network platform, DSN: a declarative language, compiler and runtime suitable for programming a broad range of sensornet applications. We demonstrate that our approach is a natural fit for sensor networks by specifying several very different classes of traditional sensor network protocols, services and applications entirely declaratively -- these include tree and geographic routing, link estimation, data collection, event tracking, version coherency, and localization. To our knowledge, this is the first time these disparate sensornet tasks have been addressed by a single high-level programming environment. Moreover, the declarative approach accommodates the desire for architectural flexibility and simple management of limited resources. Our results suggest that the declarative approach is well-suited to sensor networks, and that it can produce concise and flexible code by focusing on what the code is doing, and not on how it is doing it.

Network routing device and network routing method

Abstract: A network routing device according to the invention transmits a packet via a second port based upon destination information included in the packet received via a first port referring to a routing table. In addition, the network routing device calculates beforehand a third port which is a transfer destination when a fault occurs in a destination connected to the second port. Further, the network routing device holds scenario information including a combination of the second port and the third port and updates the routing table based upon the scenario information when a fault is detected in either of the ports.

On compact routing for the internet

Abstract: The Internet's routing system is facing stresses due to its poor fundamental scaling properties. Compact routing is a research field that studies fundamental limits of routing scalability and designs algorithms that try to meet these limits. In particular, compact routing research shows that shortest-path routing, forming a core of traditional routing algorithms, cannot guarantee routing table (RT) sizes that on all network topologies grow slower than linearly as functions of the network size. However, there are plenty of compact routing schemes that relax the shortest-path requirement and allow for improved, sublinear RT size scaling that is mathematically provable for all static network topologies. In particular, there exist compact routing schemes designed for grids, trees, and Internet-like topologies that offer RT sizes that scale logarithmically with the network size.In this paper, we demonstrate that in view of recent results in compact routing research, such logarithmic scaling on Internet-like topologies is fundamentally impossible in the presence of topology dynamics or topology-independent (flat) addressing. We use analytic arguments to show that the number of routing control messages per topology change cannot scale better than linearly on Internet-like topologies. We also employ simulations to confirm that logarithmic RT size scaling gets broken by topology-independent addressing, a cornerstone of popular locator-identifier split proposals aiming at improving routing scaling in the presence of network topology dynamics or host mobility. These pessimistic findings lead us to the conclusion that a fundamental re-examination of assumptions behind routing models and abstractions is needed in order to find a routing architecture that would be able to scale "indefinitely.

Media management and routing within an electronic device

Abstract: A method and apparatus for intelligently routing and managing audio signals within an electronic device is disclosed. The routing is responsive to a set of logical and physical policies which are stored in data tables which can be updated as needed.

Shortcut Tree Routing in ZigBee Networks

Abstract: ZigBee is the emerging industrial standard for ad hoc networks based on IEEE 802.15.4. Due to characteristics such as low data rate, low price, and low power consumption, ZigBee is expected to be used in wireless sensor networks for remote monitoring, home control, and industrial automation. Since one of the most important goals is to reduce the installation and running cost, ZigBee stack is embedded in small and cheap micro-controller units. Since tree routing does not require any routing tables to send the packet to the destination, it can be used in ZigBee end devices that have limited resources. However, tree routing has the problem that the packets follow the tree topology to the destination even if the destination is located nearby. We propose the shortcut tree routing protocol to reduce the routing cost of ZigBee tree routing by using the neighbor table that is originally defined in the ZigBee standard. While following the ZigBee tree routing algorithm, we suggest forwarding the packet to the neighbor node if it can reduce the routing cost to the destination. Simulation results show that the shortcut tree routing algorithm saves more than 30 percent of the hop count compared with ZigBee tree routing.

Movement Prediction-Based Routing (MOPR) Concept for Position-Based Routing in Vehicular Networks

Abstract: Nowadays, researchers show more and more interests to vehicular ad hoc networks (VANETs), which are a specific instance of mobile ad hoc networks (MANETs) where nodes are vehicles. In VANETs, vehicles have no energy resource constraint which could extend coverage and network lifetime, but have a high mobility patterns that cause frequent and fast topology changes. Consequently, VANETs have particular research interests, like dedicated MAC and routing optimization. In our previous work, we have proposed movement prediction-based routing (MOPR) concept for VANETs, which improves the routing process by selecting the most stable route in terms of lifetime with respect to the movement of vehicles. And in this paper, we present how this MOPR concept can be applied to position-based routing protocols, and how it improves their performances. Based on simulation results we compare MOPR with the position-based routing protocol GPSR and another movement-based routing protocol called MORA.

Deterministic versus Adaptive Routing in Fat-Trees

Abstract: Clusters of PCs have become very popular to build high performance computers. These machines use commodity PCs linked by a high speed interconnect. Routing is one of the most important design issues of interconnection networks. Adaptive routing usually better balances network traffic, thus allowing the network to obtain a higher throughput. However, adaptive routing introduces out-of-order packet delivery, which is unacceptable for some applications. Concerning topology, most of the commercially available interconnects are based on fat-tree. Fat-trees offer a rich connectivity among nodes, making possible to obtain paths between all source-destination pairs that do not share any link. We exploit this idea to propose a deterministic routing algorithm for fat-trees, comparing it with adaptive routing in several workloads. The results show that deterministic routing can achieve a similar, and in some scenarios higher, level of performance than adaptive routing, while providing in-order packet delivery.

Sociological orbit aware location approximation and routing (SOLAR) in MANET

Abstract: Mobility affects routing protocol performance in a Mobile Ad Hoc NETwork (MANET). This paper introduces a novel concept of ''macro-mobility'' information obtained from the sociological movement pattern of MANET users, and proposes a routing protocol that can take advantage of the macro-mobility information. This macro-mobility information is extracted from our observation that the movement of a mobile user exhibits a partially repetitive ''orbital'' pattern involving a set of ''hubs''. This partially deterministic movement pattern is not only practical, but also useful for locating nodes without the need for constant tracking and for routing packets to them without flooding. More specifically, this paper makes the following two contributions. First, it proposes an ORBIT mobility framework to achieve this macro-level abstraction of orbital movement. Second, to take advantage of this hub-based orbital pattern, it proposes a Sociological Orbit aware Location Approximation and Routing (SOLAR) protocol. Extensive performance analysis shows that SOLAR significantly outperforms conventional routing protocols like Dynamic Source Routing (DSR) and Location Aided Routing (LAR) in terms of higher data throughput, lower control overhead, and lower end-to-end delay.

Cooperative Routing in UWB Wireless Networks

Abstract: There is recently an increasing popularity in the use of wireless ad hoc networks, especially for sensor networks. However, these networks are susceptible to fading, interference and limited power supply. In this paper, we consider the issue of cooperative routing under the effect of both multi-user interference (MUI) and fading in ultra-wideband (UWB) networks. We first generate a single path route from any available routing algorithms. Based on this single path route, our cooperative routing algorithm is executed to see whether nodes which 'overhear' the information should cooperate to alleviate the effect of fading, and thus improve outage performance. From our result, it is shown that our cooperative routing algorithm reduces the average transmit energy by 8dB at 3% of outage.

DART: dynamic address routing for scalable ad hoc and mesh networks

Abstract: It is well known that the current ad hoc protocol suites do not scale to work efficiently in networks of more than a few hundred nodes. Most current ad hoc routing architectures use flat static addressing and thus, need to keep track of each node individually, creating a massive overhead problem as the network grows. Could dynamic addressing alleviate this problem? In this paper, we argue that the use of dynamic addressing can enable scalable routing in ad hoc networks. We provide an initial design of a routing layer based on dynamic addressing, and evaluate its performance. Each node has a unique permanent identifier and a transient routing address, which indicates its location in the network at any given time. The main challenge is dynamic address allocation in the face of node mobility. We propose mechanisms to implement dynamic addressing efficiently. Our initial evaluation suggests that dynamic addressing is a promising approach for achieving scalable routing in large ad hoc and mesh networks.

Method to enhance traffic capacity for scale-free networks.

Abstract: In this paper, a method is proposed to enhance the traffic handling capacity of scale-free networks by closing or cutting some links between some large-degree nodes, for both local routing strategy and global shortest-path routing strategy. The traffic capacity of networks is found to be considerably improved after applying the link-closing strategy, especially in the case of global routing. Due to the strongly improved network capacity, easy realization on networks, and low cost, the strategy may be useful for modern communication networks.

Balancing traffic load in wireless networks with curveball routing

Abstract: We address the problem of balancing the traffic load in multi-hop wireless networks. We consider a point-to-point communicating network with a uniform distribution of source-sink pairs. When routing along shortest paths, the nodes that are centrally located forward a disproportionate amount of traffic. This translates into increased congestion and energy consumption. However, the maximum load can be decreased if the packets follow curved paths. We show that the optimum such routing scheme can be expressed in terms of geometric optics and computed by linear programming. We then propose a practical solution, which we call Curveball Routing which achieves results not much worse than the optimum.We evaluate our solution at three levels of fidelity: a Java high-level simulator, the ns2 simulator, and the Intel Mirage Sensor Network Testbed. Simulation results using the high-level simulator show that our solution successfully avoids the crowded center of the network, and reduces the maximum load by up to 40%. At the same time, the increase of the expected path length is minimal, i.e., only 8% on average. Simulation results using the ns2 simulator show that our solution can increase throughput on moderately loaded networks by up to 15%, while testbed results show a reduction in peak energy usage by up to 25%. Our prototype suggests that our solution is easily deployable.

Map: medial axis based geometric routing in sensor networks

Abstract: One of the challenging tasks in the deployment of dense wireless networks (like sensor networks) is in devising a routing scheme for node to node communication. Important consideration includes scalability, routing complexity, quality of communication paths and the load sharing of the routes. In this paper, we show that a compact and expressive abstraction of network connectivity by the medial axis enables efficient and localized routing. We propose MAP, a Medial Axis based naming and routing Protocol that does not require geographical locations, makes routing decisions locally, and achieves good load balancing. In its preprocessing phase, MAP constructs the medial axis of the sensor field, defined as the set of nodes with at least two closest boundary nodes. The medial axis of the network captures both the complex geometry and non-trivial topology of the sensor field. It can be represented succinctly by a graph whose size is in the order of the complexity of the geometric features (e.g., the number of holes). Each node is then given a name related to its position with respect to the medial axis. The routing scheme is derived through local decisions based on the names of the source and destination nodes and guarantees delivery with reasonable and natural routes. We show by both theoretical analysis and simulations that our medial axis based geometric routing scheme is scalable, produces short routes, achieves excellent load balancing, and is very robust to variations in the network model.

Least-Cost Opportunistic Routing

Abstract: In opportunistic routing, each node maintains a group of candidate relays to reach a particular destination, and transmits packets to any node in this group. If a single candidate relay receives the packet, it becomes the effective relay to forward the packet further. If no candidate receives the packet, then the current sender re-transmits. If multiple candidates receive the packet, then the link layer chooses a single receiver to be the relay. This choice could be made at random, or it could be driven by information coming from the routing layer, for example to use the best receiver as the relay. This paper addresses the least-cost opportunistic routing (LCOR) problem: how to assign and prioritize the set of candidate relays at each node for a given destination such that the expected cost of forwarding a packet to the destination is minimized. We solve this problem with a distributed algorithm that provably computes the optimal assignment of candidate relays that each node should allow to reach a particular destination. Prior proposals based on single-path routing metrics or geographic coordinates do not explicitly consider this tradeoff, and as a result make choices which are not always optimal.

Routing in ZigBee: Benefits from Exploiting the IEEE 802.15.4 Association Tree

Abstract: An IEEE 802.15.4-based wireless sensor network is considered, and the relationship between the IEEE 802.15.4 topology formation mechanism and possible routing strategies at the network layer is studied. Two alternative routing schemes proposed in the framework of the ZigBee alliance are analyzed. The first is the well-known ad-hoc on demand distance vector (AODV) routing protocol, which was designed for highly dynamic application scenarios in wireless ad-hoc networks. The second is a tree-based routing scheme based on a hierarchical structure established among nodes during the network formation phase. This latter approach, referred to as HERA (hierarchical routing algorithm) in the paper, routes packets from sensors to sink based on the parent-child relationships established by the IEEE 802.15.4 topology formation procedure. An extensive simulation analysis is carried out to compare HERA and AODV. It is shown that a hierarchical routing scheme based on the MAC association procedures offers several benefits with respect to reactive routing in typical sensor network applications. Moreover, it is to be noted that most sensor network scenarios are concerned with delivery of packets from a series of static sensors to a single, static, sink.

Routing stability in static wireless mesh networks

Abstract: Considerable research has focused on the design of routing protocols for wireless mesh networks. Yet, little is understood about the stability of routes in such networks. This understanding is important in the design of wireless routing protocols, and in network planning and management. In this paper, we present results from our measurement-based characterization of routing stability in two network deployments, the UCSB MeshNet and the MIT Roofnet. To conduct these case studies, we use detailed link quality information collected over several days from each of these networks. Using this information, we investigate routing stability in terms of route-level characteristics, such as prevalence, persistence and flapping. Our key findings are the following: wireless routes are weakly dominated by a single route; dominant routes are extremely short-lived due to excessive route flapping; and simple stabilization techniques, such as hysteresis thresholds, can provide a significant improvement in route persistence.