Showing papers on "Wireless mesh network published in 2003"

The nominal capacity of wireless mesh networks

Abstract: Wireless mesh networks are an alternative technology for last-mile broadband Internet access. In WMNs, similar to ad hoc networks, each user node operates not only as a host but also as a router; user packets are forwarded to and from an Internet-connected gateway in multihop fashion. The meshed topology provides good reliability, market coverage, and scalability, as well as low upfront investments. Despite the recent startup surge in WMNs, much research remains to be done before WMNs realize their full potential. This article tackles the problem of determining the exact capacity of a WMN. The key concept we introduce to enable this calculation is the bottleneck collision domain, defined as the geographical area of the network that bounds from above the amount of data that can be transmitted in the network. We show that for WMNs the throughput of each node decreases as O(1/n), where n is the total number of nodes in the network. In contrast with most existing work on ad hoc network capacity, we do not limit our study to the asymptotic case. In particular, for a given topology and the set of active nodes, we provide exact upper bounds on the throughput of any node. The calculation can be used to provision the network, to ensure quality of service and fairness. The theoretical results are validated by detailed simulations.

On the capacity of hybrid wireless networks

Abstract: This paper involves the study of the throughput capacity of hybrid wireless networks. A hybrid network is formed by placing a sparse network of base stations in an ad hoc network. These base stations are assumed to be connected by a high-bandwidth wired network and act as relays for wireless nodes. They are not data sources nor data receivers. Hybrid networks present a tradeoff between traditional cellular networks and pure ad hoc networks in that data may be forwarded in a multihop fashion or through the infrastructure. It has been shown that the capacity of a random ad hoc network does not scale well with the number of nodes in the system. In this work, we consider two different routing strategies and study the scaling behavior of the throughput capacity of a hybrid network. Analytical expressions of the throughput capacity are obtained. For a hybrid network of n nodes and m base stations, the results show that if m grows asymptotically slower than √n, the benefit of adding base stations on capacity is insignificant. However, if m grows faster than √n, the throughput capacity increases linearly with the number of base stations, providing an effective improvement over a pure ad hoc network. Therefore, in order to achieve nonnegligible capacity gain, the investment in the wired infrastructure should be high enough.

Multipath Routing in Mobile Ad Hoc Networks: Issues and Challenges

Abstract: Mobile ad hoc networks (MANETs) consist of a collection of wireless mobile nodes which dynamically exchange data among themselves without the reliance on a fixed base station or a wired backbone network MANET nodes are typically distinguished by their limited power, processing, and memory resources as well as high degree of mobility In such networks, the wireless mobile nodes may dynamically enter the network as well as leave the network Due to the limited transmission range of wireless network nodes, multiple hops are usually needed for a node to exchange information with any other node in the network Thus routing is a crucial issue to the design of a MANET In this paper, we specifically examine the issues of multipath routing in MANETs Multipath routing allows the establishment of multiple paths between a single source and single destination node It is typically proposed in order to increase the reliability of data transmission (ie, fault tolerance) or to provide load balancing Load balancing is of especial importance in MANETs because of the limited bandwidth between the nodes We also discuss the application of multipath routing to support application constraints such as reliability, load-balancing, energy-conservation, and Quality-of-Service (QoS)

Mobile mesh ad-hoc networking

Abstract: An architectural solution in which standalone ad-hoc network cells are used as an extension of the backbone infrastructure in terms of network architecture or/and its service capabilities is provided. These Ad-Hoc networks will integrate to the Internet via cellular and other access networks. This integration brings new possibilities to network operators and ISP's. In its extended architecture, it is envisaged that the mobility issues are handled by utilizing the IP mobility capabilities, taking into account the mobile mesh Ad-Hoc specific requirements.

Secure aggregation for wireless networks

Abstract: An emerging class of important applications uses ad hoc wireless networks of low-power sensor devices to monitor and send information about a possibly hostile environment to a powerful base station connected to a wired network. To conserve power, intermediate network nodes should aggregate results from individual sensors. However, this opens the risk that a single compromised sensor device can render the network useless, or worse, mislead the operator into trusting a false reading. We present a protocol that provides a secure aggregation mechanism for wireless networks that is resilient to both intruder devices and single device key compromises. Our protocol is designed to work within the computation, memory and power consumption limits of inexpensive sensor devices, but takes advantage of the properties of wireless networking, as well as the power asymmetry between the devices and the base station.

Localized minimum-energy broadcasting in ad-hoc networks

Abstract: In the minimum energy broadcasting problem, each node can adjust its transmission power in order to minimize total energy consumption but still enable a message originated from a source node to reach all the other nodes in an ad-hoc wireless network. In all existing solutions each node requires global network information (including distances between any two neighboring nodes in the network) in order to decide its own transmission radius. We describe a new localized protocol where each node requires only the knowledge of its distance to all neighboring nodes and distances between its neighboring nodes (or, alternatively, geographic position of itself and its neighboring nodes). In addition to using only local information, our protocol is shown experimentally to be comparable to the best known globalized BIP solution. Our solutions are based on the use of relative neighborhood graph, which preserves connectivity and is defined in localized manner.

Throughput capacity of random ad hoc networks with infrastructure support

Abstract: In this paper, we consider the transport capacity of ad hoc networks with a random flat topology under the present support of an infinite capacity infrastructure network. Such a network architecture allows ad hoc nodes to communicate with each other by purely using the remaining ad hoc nodes as their relays. In addition, ad hoc nodes can also utilize the existing infrastructure fully or partially by reaching any access point (or gateway) of the infrastructure network in a single or multi-hop fashion. Using the same tools as in [1], we show that the per source node capacity of T(W/log(N)) can be achieved in a random network scenario with the following assumptions: (i) The number of ad hoc nodes per access point is bounded above, (ii) each wireless node, including the access points, is able to transmit at W bits/sec using a fixed transmission range, and (iii) N ad hoc nodes, excluding the access points, constitute a connected topology graph. This is a significant improvement over the capacity of random ad hoc networks with no infrastructure support which is found as T(W/vN log(N)) in [1]. Although better capacity figures may be obtained by complex network coding or exploiting mobility in the network, infrastructure approach provides a simpler mechanism that has more practical aspects. We also show that even when less stringent requirements are imposed on topology connectivity, a per source node capacity figure that is arbitrarily close to T(1) cannot be obtained. Nevertheless, under these weak conditions, we can further improve per node throughput significantly.

Integrated wireless distribution and mesh backhaul networks

Abstract: Networks, devices and methods related to wireless networking. A wireless network using nodes that perform both distribution and backhaul functions is provided. These nodes constitute the key elements of a wireless network that would be deployed and controlled by a wireless network operator. Each node contains a distribution wireless module which is wirelessly coupled to the wireless end user device using a point to multipoint scheme. Also integrated into each node is at least one backhaul wireless module with a directional wireless antenna. Each backhaul wireless module communicates by way of a point to point wireless link with the backhaul module of one other node. The nodes in the wireless network are interconnected to form a mesh backhaul network. Because of the nature of a mesh network, data traffic can be routed around obstacles that may prevent line of site links. Furthermore, the mesh network allows dynamic routing of data traffic to avoid congestion points or downed links in the network.

Topology Control Protocols to Conserve Energy in Wireless Ad Hoc Networks

Abstract: In wireless ad hoc networks and sensor networks, energy use is in many cases the most important constraint since it corresponds directly to operational lifetime. This paper presents two topology control protocols that extend the lifetime of dense ad hoc networks while preserving connectivity, the ability for nodes to reach each other. Our protocols conserve energy by identifying redundant nodes and turning their radios off. Geographic Adaptive Fidelity (GAF) identifies redundant nodes by their physical location and a conservative estimate of radio range. Cluster-based Energy Conservation (CEC) directly observes radio connectivity to determine redundancy and so can be more aggressive at identifying duplication and more robust to radio fading. We evaluate these protocols through analysis, extensive simulations, and experimental results in two wireless testbeds, showing that the protocols are robust to variance in node mobility, radio propagation, node deployment density, and other factors.

Connectivity of wireless multihop networks in a shadow fading environment

Abstract: This paper investigates the connectivity of wireless multihop networks in a log--normal shadow fading environment. Assuming a spatial Poisson distribution of the network nodes, we derive (a) a closed--form expression for the probability that a node is isolated and (b) a tight bound for the minimum node density that is needed to obtain an almost surely connected subnetwork on a given area. Both results find application in the design and simulation of wireless sensor and ad hoc networks.

Security in ad hoc networks

Abstract: In wirelesss ad hoc networks basic network operations are carried out through the cooperation of all available nodes. Due to the inherent lack of a managed infrastructure the nodes of an ad hoc network cannot be considered as trustworthy as in a dedicated infrastructure. Wireless ad hoc networks are thus vulnerable to various exposures threatening the basic network operations like routing and packet forwarding. This paper presents a survey of current research activities dealing with routing security, cooperation enforcement and key management in wireless ad hoc networks. Existing solutions seem to only partially address the threats and fall short of providing a comprehensive answer. Wireless security mechanisms in layer 2 that are often considered as part of the solution domain do not meet the specific requirements of wireless ad hoc networks.

Protocol and structure for mobile nodes in a self-organizing communication network

Abstract: A self-organizing network characterized as having a number of nodes, with at least one control node of the nodes operable to control one or more of the formation, maintenance and message routing between nodes of the network, and operable to support the association, maintenance, deployment, and disassociation of one or more mobile nodes (MN) in the network (200, 300). The mobile nodes do not form part of the logical backbone of the network and thus may have a static address assigned to them to facilitate communications between regular, fixed nodes of the network and the mobile node in an efficient manner.

System and method for determining relative positioning in ad-hoc networks

Abstract: A system and method for improving the ability of a portable voice and data wireless communications network to provide position information regarding mobile nodes located within a network (figure 1). The system and method employs mobile access points (101), wireless routers (102), and mobile nodes (103), which each contain at least one transceiver, and are mounted or dispersed at a geographic location. Access points can be connected to mobile vehicles, or connected to a network management system, and wireless routers can be mounted to portable stands for easy deployment. Mobile nodes can be attached to equipment or personnel for tracking purposes, and each node includes technology which may determine an absolute node location containing latitude, longitude and altitude of a node, or a relative node location containing the distance and angle between nodes, or a combination of both absolute and relative location data.

Method and Apparatus for Providing Mobile Inter-Mesh Communication Points in a Multi-Level Wireless Mesh Network

Abstract: A mobile backhaul inter-mesh communication point forms an interface between a wireless mesh network on a first level and a wireless mesh network on a second, higher bandwidth, level. The two wireless networks are differentiated, e.g., by causing the mesh networks to be formed using different spectra, protocols or coding, or antennae. The mobile intra-mesh communication point functions as an access point in the lower level mesh network and as a relay point in the upper level mesh network. Utilizing mobile inter-mesh communication points facilitates deployment of wireless network access points while enabling the location of access points to follow the concentration of network users. Mobile inter-mesh communication points may be deployed in personal vehicles such as cars, trucks, and motorcycles, public transportation vehicles such as busses, trains, and aircraft, emergency vehicles such as fire trucks and ambulances, and many other types of vehicles.

Simulation of large ad hoc networks

Abstract: This research was supported, in part, by the NCCR "Mobile Information and Communication Systems", a research program of the Swiss National Science Foundation, and by a gift from the Microprocessor Research Lab (MRL) of Intel Corp.An ad hoc network is formed by wireless mobile nodes (hosts) that operate as terminals as well as routers in the network, without any centralized administration. Research in ad hoc networks often involves simulators since management and operation of a large number of nodes is expensive. However, the widely used simulator NS-2 does not scale; it is very hard to simulate medium scale networks with 100+ nodes. We describe here improvements to NS-2 to meet the needs of large ad hoc network simulations. The modified NS-2 simulator is based on the idea of exploiting the limited interference of wireless communication. The modified simulator has simulated populations of up to 3000 nodes so far and works up to 30 times faster than the original version. We also discuss how the modified simulator is validated.

Hop distances in homogeneous ad hoc networks

Abstract: Given is the network-level view of a wireless multi-hop network with n uniformly distributed nodes, each of them with radio transmission range r/sub 0/, on a rectangular area. This paper investigates the discrete probability distribution of the minimum number of wireless hops H between a random source and destination node. This topology attribute has significant impact on the network performance, e.g., on route discovery delay and message delivery. We derive closed form expressions for the probability that two nodes can communicate within H = 1 hop (i.e., via a direct link) or H = 2 hops (i.e., over one relay node). Connection paths with H > 2 hops and the expected hop distance E{H} are studied by analytical bounds and extensive simulations.

An adaptive mesh-based protocol for geocast routing

Abstract: This article concerns a variation on multicasting, called geocasting, for an ad hoc network. The goal of a geocast routing protocol is to deliver packets to a group of nodes that are within a specified geographical area, i.e., the geocast region. This paper presents a Geocast Adaptive Mesh Environment for Routing (GAMER) which provides geocast communication in an ad hoc network. GAMER adapts to the current network environment by dynamically changing the density of the mesh. Thus, when nodes are highly mobile, a dense mesh is created; when nodes are moving slowly, a sparse mesh is created. We compare the performance of GAMER with non-adaptive mesh-based geocast routing protocols in an ns-2 simulated ad hoc network. We also compare two versions of GAMER; one version is more active than the other in adapting to the current network environment. We conclude that both versions of GAMER improve the transmission accuracy significantly, without increasing the load on the network significantly, when compared to non-adaptive mesh-based geocast routing approaches.

EMPOWER: a network emulator for wireline and wireless networks

Abstract: The increasing need of protocol development environments and network performance evaluation tools gives rise to the research of flexible, scalable, and accurate network emulators. The desired network emulator should be able to facilitate the emulation of either wireline or wireless networks. In the case when network topology is critical to the underlying network protocol, the emulator should provide specific mechanisms to emulate network topology. In this paper, we present a distributed network emulation system EMPOWER, which not only can fulfill those requirements, but also can generate user-defined network conditions and traffic dynamics at packet level. EMPOWER is highly scalable in that each emulator node could be configured to emulate multiple network nodes. Some significant research issues such as topology mapping scheme and scalability of the emulator are discussed and addressed. Preliminary emulation results show that EMPOWER is capable of assisting the study of both wireless and wireline network protocols and applications.

A system and method for determining physical location of a node in a wireless network during an authentication check of the node

Abstract: A system and method for providing security to a wireless network by using a mobile node's location as a parameter for deciding if access is to be given to the node. The system and method employ access points, wireless routers and mobile nodes, each including at least one transceiver adapted to transmit and receive communication signals to and from other wireless routers, mobile nodes and other mobile access points. Each access point is connected to a network management system which allows enhanced network monitoring and control. Each network node includes technology which may determine an absolute node location containing latitude, longitude and altitude of a node, or a relative node location containing the distance and angle between nodes, or a combination of both absolute and relative location data.

Hybrid wireless network protocols

Abstract: Basically, there are two types of wireless network systems - base-station (BS) oriented networks and ad hoc wireless networks. In the first type, the mobile hosts communicate with base stations, while, in ad hoc networks, the mobile hosts communicate with one another directly. The BS-oriented wireless network has better performance and is more reliable. However, the ad hoc network topology is desirable because of its low cost, plug-and-play convenience, and flexibility. Its usage of bandwidth and battery power is more efficient, but route and communication connectivity is fairly weak; any migration by a host participating in one or more routes could make the route invalid. Much cost is incurred in maintaining communication. Thus, the ad hoc wireless network is only suitable for applications in a small geographical area. We propose hybrid wireless network protocols to combine the advantages of BS-oriented and ad hoc wireless networks. We allow two mobile hosts to communicate directly (one-hop direct transmission) or through another mobile host (two-hop direct transmission) within a BS-oriented network. The hybrid protocols are more flexible, reliable, and have better performance than the traditional protocols. Simulation results show that two-hop direct-transmission has a lower non-completion probability. If the communicating parties are always within a two-hop direct-transmission area, the rate of complete communication improves by about 20%.

Resisting Malicious Packet Dropping in Wireless Ad Hoc Networks

Abstract: Most of the routing protocols in wireless ad hoc networks, such as DSR, assume nodes are trustworthy and cooperative. This assumption renders wireless ad hoc networks vulnerable to various types of Denial of Service (DoS) attacks. We present a distributed probing technique to detect and mitigate one type of DoS attacks, namely malicious packet dropping, in wireless ad hoc networks. A malicious node can promise to forward packets but in fact fails to do so. In our distributed probing technique, every node in the network will probe the other nodes periodically to detect if any of them fail to perform the forwarding function. Subsequently, node state information can be utilized by the routing protocol to bypass those malicious nodes. Our experiments show that in a moderately changing network, the probing technique can detect most of the malicious nodes with a relatively low false positive rate. The packet delivery rate in the network can also be increased accordingly.

Dynamically managing and reconfiguring wireless mesh networks

Abstract: A wireless network with multiple subscriber systems in a lobe pool may operate by determining a state of the wireless network, identifying a new condition, the new condition including a new demand condition or a new network health condition, determining whether the new condition has a threshold impact on operations of the wireless network or component subscriber systems of the wireless network, and if the threshold impact exists, reconfiguring the wireless network to accommodate the new condition.

Upper bounds to transport capacity of wireless networks

Abstract: We derive upper bounds on the transport capacity of wireless networks The bounds obtained are solely dependent on the geographic locations and power constraints of the nodes As a result of this derivation, we are able to conclude the optimality, in the sense of scaling of transport capacity with the number of nodes, of a multi-hop communication strategy for a class of network topologies

System and method for measuring per node packet loss in a wireless network

Abstract: A method and system for configuring a wireless network, e.g., an ad hoc wireless network having a plurality of nodes and at least one server. In the wireless network, among other things, mesh network viability is maintained as packet loss information is recorded at a plurality of individual nodes in the wireless network during packet transmission from each of the plurality of nodes. The packet loss information may be stored at the at least one server for access at a period of time other than the moment when the packet is received at the at least one server from one of the plurality of nodes.

Mixed-mode WLAN: the integration of ad hoc mode with wireless LAN infrastructure

Abstract: In the traditional IEEE 802.11 wireless LAN using infrastructure mode, all users share the same channel and all packets are forwarded by an access point (AP). As a result, as the number of users in the cell increases, the throughput for each user degrades substantially. If there are users communicating with each other within the cell (as in conferencing or file exchange applications), such throughput degradation could be relieved by making these users communicate through ad hoc connections without going through the AP. The advantages are multi-fold. First, the traffic load at the AP is reduced, hence relieving the contention. Second, ad hoc connections are single-hop, hence improving the channel efficiency. Moreover, ad hoc connections could use different channels, hence multiplying the system bandwidth. In this paper, we propose to integrate the infrastructure mode and the ad hoc mode in a wireless network so as to achieve these advantages. We present a framework for such mixed-mode wireless LAN (termed M/sup 2/-WLAN). In such a network, a node can dynamically switch between the infrastructure mode and the ad hoc mode according to the instruction of the AP, and hence the switching is transparent to the users. Using simulations, we show that M/sup 2/-WLAN can indeed improve system throughput substantially without user's manual configuration.

Mesh networks with exclusion capability

Abstract: In an exemplary method implementation, a method includes: designating a neighborhood administrator; receiving notification of a delinquent router from the designated neighborhood administrator; and excluding the delinquent router responsive to the notification. In an exemplary mesh router implementation, a mesh router is capable of establishing a wireless mesh network with other mesh routers, the mesh router is further capable of designating a neighborhood administrator mesh router; and the mesh router is adapted to exclude another mesh router that is associated with a particular certificate when the particular certificate has been identified as delinquent by the designated neighborhood administrator. mesh router.

Mesh network bridges making operable spanning tree protocol and line fault backup protocol in optimized forwarding environment

Abstract: A plurality of mesh-connecting ports interconnect a plurality of bridges including an own bridge and other bridges as a mesh network. A packet transmitter/receiver reciprocally transmits and receives packets between the plurality of bridges through the mesh-connecting ports. A shortest path constructing unit constructs the shortest path between the bridges through the packet transmitter/receiver. An STP processing unit executes STP processing for activating a spanning tree protocol (STP) to provide redundancy to the mesh network. A backup processing unit continuously leaves in the mesh domain a first mesh network bridge detected a line fault, and executes the backup processing to active a back up protocol for forming a backup route in such a manner that the packet reaches a second mesh network bridge that has become unreachable by the line fault, through a third mesh bridge connected with the second mesh network bridge.

Mesh implementation of light-trails: a solution to IP centric communication

Abstract: Light-trails communication (Chlamtac and Gumaste, 2003) proposes a solution for implementing a conceptual framework for IP centric communication in the optical domain which is a combination of node architecture and protocol for realizing efficient optical communications from IP bursts to dynamic lightpaths. In this paper we introduce a Light-trails solution that is applicable to mesh networks. Contrary to existing proposals for IP type communication in the optical domain light-trail node architecture also presents the first practically implementable solution to enable optical transport with mature technology, nonstringent optical switching requirements, and potentially presents a cost effective alternative to electronics in supporting IP networks.

Secure dynamic distributed routing algorithm for ad hoc wireless networks

Abstract: An ad hoc wireless network permits wireless mobile nodes to communicate without prior infrastructure. Due to the limited range of each wireless node, communication sessions between two nodes are usually established through a number of intermediate nodes. Unfortunately, some of these intermediate nodes might be malicious, forming a threat to the security or confidentiality of exchanged data. While data encryption can protect the content exchanged between nodes, analysis of communication patterns may reveal valuable information about end users and their relationships. Using anonymous paths for communication provides security and privacy against traffic analysis. To establish these anonymous paths, all nodes build a global view of the network by exchanging routing information. In dynamic ad hoc networks, building this global view is not an option. In this paper, we propose and analyze a distributed route construction algorithm for use in the establishment of anonymous routing paths in ad hoc wireless networks.

Localized topology generation mechanisms for wireless sensor networks

Abstract: The basic topology desired in data-gathering wireless sensor networks is a spanning tree, since the traffic is mainly in the form of many-to-one flows. Nodes in the network can self-configure themselves into such a topology by a two-phase process: a flood initiated by the root node, followed by parent selection by all nodes. We present four localized topology generation mechanisms - earliest-first, randomized, nearest-first, and weighted-randomized parent selection. We also compare the network performance of these mechanisms on the basis of the following metrics: node degree, robustness, channel quality, data aggregation and latency; our study shows how localized self-configuration mechanisms can impact the global network behavior.