Showing papers on "Wireless mesh network published in 2002"

Mobility increases the capacity of ad hoc wireless networks

Abstract: The capacity of ad hoc wireless networks is constrained by the mutual interference of concurrent transmissions between nodes. We study a model of an ad hoc network where n nodes communicate in random source-destination pairs. These nodes are assumed to be mobile. We examine the per-session throughput for applications with loose delay constraints, such that the topology changes over the time-scale of packet delivery. Under this assumption, the per-user throughput can increase dramatically when nodes are mobile rather than fixed. This improvement can be achieved by exploiting a form of multiuser diversity via packet relaying.

Traffic grooming in an optical WDM mesh network

Abstract: In wavelength-division multiplexing (WDM) optical networks, the bandwidth request of a traffic stream can be much lower than the capacity of a lightpath. Efficiently grooming low-speed connections onto high-capacity lightpaths will improve the network throughput and reduce the network cost. In WDM/SONET ring networks, it has been shown in the optical network literature that by carefully grooming the low-speed connection and using wavelength-division multiplexer (OADM) to perform the optical bypass at intermediate nodes, electronic ADMs can be saved and network cost will be reduced. In this study, we investigate the traffic-grooming problem in a WDM-based optical mesh topology network. Our objective is to improve the network throughput. We study the node architecture for a WDM mesh network with traffic-grooming capability. A mathematical formulation of the traffic-grooming problem is presented in this study and several fast heuristics are also proposed and evaluated.

A directionality based location discovery scheme for wireless sensor networks

Abstract: A sensor network is a large ad hoc network of densely distributed sensors that are equipped with low power wireless transceivers. Such networks can be applied for cooperative signal detection, monitoring, and tracking, and are especially useful for applications in remote or hazardous locations. This paper addresses the problem of location discovery at the sensor nodes, which is one of the central design challenges in sensor networks. We present a new method by which a sensor node can determine its location by listening to wireless transmissions from three or more fixed beacon nodes. The proposed method is based on an angle-of-arrival estimation technique that does not increase the complexity or cost of construction of the sensor nodes. We present the performance of the proposed method obtained from computer simulations.

Connectivity based k-hop clustering in wireless networks

Abstract: In this paper we describe several new clustering algorithms for nodes in a mobile ad hoc network. We propose to combine two known approaches into a single clustering algorithm which considers connectivity as a primary criterion and lower ID as secondary criterion for selecting cluster heads. The goal is to minimize the number of clusters, which results in dominating sets of smaller sizes (this is important for applications in broadcasting and Bluetooth formation). We also describe algorithms for modifying cluster structure in the presence of topological changes. Next, we generalize the cluster definition so that a cluster contains all nodes that are at a distance of at most k hops from the cluster head. The efficiency of four clustering algorithms (k-lowestID and k-CONID, k=1 and k=2) is tested by measuring the average number of created clusters, the number of border nodes, and the cluster size in random unit graphs. The most interesting experimental result is stability of the ratio of the sum of CHs and border nodes in the set. It was constantly 60-70% for 1-lowestID and 46-56% for 1-ConID, for any value of n (number of nodes) and d (average node degree). Similar conclusions and similar number were obtained for k=2. We also proposed a unified framework for most existing and new clustering algorithms where a properly defined weight at each node is the only difference in the algorithm. Finally, we propose a framework for generating random unit graphs with obstacles.

Investigating upper bounds on network lifetime extension for cell-based energy conservation techniques in stationary ad hoc networks

Abstract: Cooperative cell-based strategies have been recently proposed as a technique for extending the lifetime of wireless ad hoc networks, while only slightly impacting network performance. The effectiveness of this approach depends heavily on the node density: the higher it is, the more consistent energy savings can potentially be achieved. However, no general analyses of network lifetime have been done either for a base network (one without any energy conservation technique) or for one using cooperative energy conservation strategies. In this paper, we investigate the lifetime/density tradeoff under the hypothesis that nodes are distributed uniformly at random in a given region, and that the traffic is evenly distributed across the network. We also analyze the case where the node density is just sufficient to ensure that the network is connected with high probability. This analysis, which is supported by the results of extensive simulations, shows that even in this low density scenario, cell-based strategies can significantly extend network lifetime.

IP address assignment in a mobile ad hoc network

Abstract: A mobile ad hoc network (MANET) consists of a set of identical mobile nodes communicating with each other via wireless links. The network's topology may change rapidly and unpredictably. Such networks may operate in a stand-alone fashion, or may be connected to the larger Internet. In traditional networks, hosts rely on centralized servers like DHCP for configuration, but this cannot be extended to MANETs because of their distributed and dynamic nature. Many schemes have been proposed to solve this problem. Some of these approaches try to extend the IPv6 stateless autoconfiguration mechanism to MANETs, some use flooding the entire network to come up with a unique IP address, and others distribute IP addresses among nodes (using binary split) so that each node can independently configure new nodes. None of these existing solutions consider network partitioning and merging. In this paper, we propose a proactive scheme for dynamic allocation of IP addresses in MANETs. Our solution also uses the concept of binary split and takes into consideration the previously unsolved issues like partitioning and merging and abrupt departure of nodes from the system. We show that our solution is scalable and does not have the limitations of earlier approaches.

MIRAI architecture for heterogeneous network

Abstract: One of the keywords that describe next-generation wireless communications is "seamless." As part of the e-Japan Plan promoted by the Japanese Government, the Multimedia Integrated Network by Radio Access Innovation project has as its goal the development of new technologies to enable seamless integration of various wireless access systems for practical use by 2005. This article describes a heterogeneous network architecture including a common tool, a common platform, and a common access. In particular, software-defined radio technologies are used to develop a multiservice user terminal to access different wireless networks. The common platform for various wireless networks is based on a wireless-supporting IPv6 network. A basic access network, separated from other wireless access networks, is used as a means for wireless system discovery, signaling, and paging. A proof-of-concept experimental demonstration system is available.

K-clustering in wireless ad hoc networks

Abstract: Ad hoc networks consist of wireless hosts that communicate with each other in the absence of a fixed infrastructure. Clustering is commonly used in order to limit the amount of routing information stored and maintained at individual hosts. A k-clustering is a framework in which the wireless network is divided into non-overlapping sub networks, also referred to as clusters, and where every two wireless hosts in a sub network are at most k hops from each other. The algorithmic complexity of k-clustering is known to be NP-Complete for simple undirected graphs. For the special family of graphs that represent ad hoc wireless networks, modeled as unit disk graphs, we introduce a two phase distributed polynomial time and message complexity approximation solution with O(k) worst case ratio over the optimal solution. The first phase constructs a spanning tree of the network and the second phase then partitions the spanning tree into subtrees with bounded diameters.

Wireless mesh network

Abstract: Method and apparatus for providing a wireless mesh network and network node are described. More particularly, a network having network node neighborhoods is described. A node comprises a multi-sectored antenna and a transceiver controller. Nodes are configured for installation without antenna pointing and without pre-coordination with the network. Software architecture for the node is also described.

On the capacity of wireless relaying

Abstract: We consider wireless relaying: one or more nodes in a wireless (ad-hoc) network assist other nodes in their transmission by partially retransmitting messages. A characteristic of wireless relays - as compared to the work by T.M. Cover and A.A. El Gamal on the relay channel (see IEEE Trans. on Inf. Theory, vol.25, no.5, p.572-84, 1979) - is that they cannot transmit and receive simultaneously at the same frequency. We derive new upper and lower bounds for the capacity of this wireless relay channel. We then apply these result to a 4 terminal network, and show that the gain (considering outage capacity) of using wireless relaying is of the order of 8-9 dB.

Energy Efficient Design of Wireless Ad Hoc Networks

Abstract: One of the most critical issues in wireless ad hoc networks is represented by the limited availability of energy within network nodes. The time period from the instant when the network starts functioning to the instant when the first networkno de runs out of energy, the so-called network life-time, strictly depends on the system energy efficiency. Our objective is to devise techniques to maximize the network life-time in the case of cluster-based systems, which represent a significant subset of ad hoc networks. We propose an original approach to maximize the network life-time by determining the optimal clusters size and the optimal assignment of nodes to cluster-heads. The presented solution greatly outperforms the standard assignment of nodes to cluster-heads, based on the minimum distance criterion.

Interference in Wireless Multi-hop Ad-hoc Networks

Abstract: In this paper we propose a new model to calculate interference levels in wireless multi-hop ad-hoc networks. This model computes the expected value of Carrier to Interference ratio (C/I) by taking into account the number of nodes, density of nodes, radio propagation aspects, multi-hop characteristics of the network, and the amount of relay traffic. Our model uses a regular lattice for possible locations of mobile nodes. This enables us to calculate the expected values of C/I , without having detailed information about movement patterns and exact location of all nodes at any moment. Based on this model we have evaluated effects of variations in the network size, network density and traffic load on C/I , and consequently throughput of the network. Our calculations suggest that interference is upper-bounded in wireless ad-hoc networks that use carrier sensing for medium access. Further, our calculations indicate that in large networks traffic increase due to routing overhead does not have a significant impact on network throughput.

New options and insights for survivable transport networks

Abstract: This article is devoted to a selection of recent topics in survivable networking. New ideas in capacity design and ring-to-mesh evolution are given, as well as a systematic comparison of the capacity requirements of several mesh-based schemes showing how they perform over a range of network graph connectivity. The work provides new options and insights to address the following questions. How does one evolve from an existing ring-based network to a future mesh network? If the facilities graph is very sparse, how can mesh efficiency be much better than rings? How do the options for mesh protection or restoration rank in capacity requirements? How much is efficiency increased if we enrich our network connectivity? We also outline p-cycles, showing this new concept can realize ring-like speed with meshlike efficiency. The scope is limited to conveying basic ideas with an understanding that they could be further adapted for use in IP or DWDM layers with GMPLS-type protocols or a centralized control plane.

On the connectivity of wireless multihop networks with homogeneous and inhomogeneous range assignment

Abstract: This paper investigates the connectivity of wireless multihop networks with uniformly randomly distributed nodes. We analyze the required transmission range that creates, for a given node density, an almost surely k-connected topology. Besides scenarios in which each node has the same range, we discuss inhomogeneous range assignments. Our results are of practical value for the task of setting parameters in network-level simulations of ad hoc networks and in the design of wireless sensor networks.

Radio access network with meshed radio base stations

Abstract: A wireless communication network supporting mobile communications includes a mesh of radio base stations (RBSs) interconnected to form a packet data routing network. The RBSs are RF-coupled together so that adjacent ones may relay communications traffic to each other. By attaching to the mesh of radio base stations at one or more attachment points, communications traffic may be routed between a base station controller and any one of the radio base stations in the mesh based on configuring the appropriate route through the mesh. Preferably, the mesh is implemented as an IP-based routing network with each radio station in the mesh operating as an addressable routing node wtihin the mesh.

QoS Routing for Mesh-Based Wireless LANs

Abstract: Wireless LANs with their increased data rate become an attractive technology for connecting mobile users to the Internet. Efficient deployment of wireless LANs will require the ability to extend the wireless LANs coverage without the need to deploy a very large number of access points. Mesh-based wireless LANs are an attractive solution to this problem. These networks extend wireless LAN coverage by using each node in the network as a router, resulting in a multihop topology. In this paper we introduce a novel routing algorithm, wireless mesh routing (WMR), that provides quality-of-service (QoS) support and accounts for the characteristics of both infrastructure-based wireless LANs and ad hoc networks. The algorithm is validated using the OPNET modeler. The simulation results show that the mesh network using WMR protocol can provide QoS support and react dynamically to the network status changes with low control overheads. Using the proposed software architecture the proposed routing protocol can be implemented with any MAC protocol, resulting in easy implementation in existing wireless nodes.

Coordinated power conservation for ad hoc networks

Abstract: Existing ad hoc routing protocols assume all nodes within the network to participate in the routing process. By conditionally selecting a subset of nodes is an appropriate approach to limiting the number of nodes participating in routing such that nodes not selected may be turned off to conserve power and extend network lifetime. However, not all non-routing-related nodes will be able to be turned off (suspended) at the same time. Sufficient bandwidth and forwarding capacity are still necessary in case of changing network topology and environment. We describe the coordinated power conservation (CPC) algorithm to facilitate power conservation for ad hoc networks. The algorithm constructs a backbone infrastructure to have CPC servers running on backbone nodes to coordinate suspending schedules among their local non-backbone nodes running CPC clients. Simulation results demonstrate that CPC-enabled ad hoc networks exhibit performance closely equivalent to ad hoc networks without CPC, while consuming less power.

Multihop scatternet formation for Bluetooth networks

Abstract: This paper describes a new protocol for the establishment of multihop ad hoc networks based on Bluetooth devices. The proposed solution is specification compatible, and achieves the following desirable properties, only a few of which are available in previous solutions. The protocol is executed at each node with no prior knowledge of the network topology, thus being fully distributed. The selection of the Bluetooth masters is driven by the suitability of a node to be the "best fit" for serving as a master. The generated topology (a scatternet, according to the Bluetooth terminology) is a connected mesh with multiple paths between any pair of nodes, thus achieving robustness. In contrast to existing protocols, the proposed solution does not assume any designated device to start the scatternet formation process and it is multihop in the precise sense that there is no requirement for each node to be in the transmission range of all the other nodes (one-hop networks).

Method for allocating protection bandwidth in a telecommunications mesh network

Abstract: A telecommunications mesh network includes a plurality of nodes each interconnected by an edge. A traffic demand is received having a working path with a link of edges interconnecting a source node with a destination node. The telecommunications mesh network has one or more pre-cross-connected trails associated therewith that are subdivided into one or more subtrails. Subtrails that do not meet pre-determined conditions are discarded. A logical graph representation of the telecommunications mesh network is created from subtrails that have not been discarded. Unused, shortcut, and rival edges are inserted into the logical graph. A shortest admissible protection path from the source node to the destination node is identified from the logical graph.

Wireless broadband in a box

Abstract: Despite all the talk about broadband, only about 7%, or 7.5 million, of US households subscribed to high-speed Internet access services as of last June, according to a February report issued by the US Federal Communications Commission (FCC). The situation is not much different elsewhere; only a few countries with much smaller populations report somewhat higher percentages. Lack of need is, one reason for the unimpressive numbers. Another reason is difficulty in getting service. For a variety of reasons, many would-be subscribers have been unable to get cable or digital subscriber line (DSL) service. For them, a fairly new type of technology known as non-line-of-sight (NLOS) wireless may be just what they need. NLOS wireless systems offer high-speed Internet access over several kilometers without directional antennas. When wireless routers are mounted on a subscribers' building, they can configure themselves into a mesh network. Mesh networks solve the problem of connecting widely separated wireless routers that cannot see each other by using many intermediate points, each of which can be seen by its neighbors. The article looks at the potential of this technology.

Elective participation in ad hoc networks based on energy consumption

Abstract: In ad hoc networks, each node utilizes its limited resources to carry out the collective operation of the network. It is not always in the best interests of the network's nodes to demand the continuous participation of all nodes in the network operations. We propose an energy dependent participation (EDP) scheme, where a node periodically re-evaluates its participation in the network based on the residual energy in its battery. More importantly, a node gives special consideration to supporting the communication needs of its active network applications and preventing further network partitioning. EDP's localized partition checking algorithm is particularly well suited for the zone routing protocol, where the link-state information is proactively maintained within each node's local zone and routes to faraway nodes are reactively obtained via global queries. Through simulations, we evaluate the impact of our proposed scheme on battery life and network connectivity. Our results suggest that the EDP scheme can increase the usable lifetime of a battery-constraint ad hoc network by over 50%.

Link expiration times in mobile ad hoc networks

Abstract: Mobile ad hoc networks are self configuring wireless networks without any fixed infrastructure. The members within such a network move independently from each other and their movements are not restricted in any case (in car to car ad-hoc networks nodes partly drive in the same direction). Hence, it is impossible to predict routes, link expiration or link failure times. We describe a simplified scenario with two stationary terminals and one terminal in motion. This simple approach allows a statistical derivation to forecast the average distance the moving relay is within the scope of the two other nodes. With these statistical calculations, predictions about the average link expiration times and deviations for different node velocities are possible, independent from the nodes' radio transmission ranges and the distances between each other.

Self-surveying wireless network

Abstract: A wireless node capable of self-configuring a wireless network includes an ultra-wideband (UWB) transceiver and an antenna coupled to the UWB transceiver A logic circuit is adapted to automatically establish the wireless network with at least one of a plurality of wireless nodes based on UWB signals having distance information transmitted by the plurality of wireless nodes The locations of the plurality of wireless nodes are calculated based on the distance information

Comparison of two optical-core networks

Abstract: The resource requirements for two optical-core network architectures are compared One architecture is a highly optimized, multihop mesh of optical switches, in which the number of optical nodes traversed by a light path is bounded The other is a single-hop composite-star structure We show in a case study that although the composite star may require a higher fiber-distance value than the optimized mesh structure, it needs many fewer ports and a smaller optical switching fabric to achieve the same throughput The single-hop network does not require any wavelngth conversion, it eliminates the need for traffic engineering, and is resilient to changes in the spatial distribution of traffic Results are quantified through simulation

Design of WDM mesh networks with sparse grooming capability

Abstract: In a WDM optical network, the bandwidth requirement of a customer's connection can vary over a wide range, and many of these connections could have a capacity that is much lower than the capacity of a wavelength channel. Efficiently grooming low-speed connections onto high-capacity wavelength channels can significantly improve the bandwidth utilization and minimize the network cost. Our research shows that it is not necessary to have traffic-grooming capability at every network node. We call a network which has only a few grooming nodes to be a sparse-grooming network. Through proper network design and traffic engineering, it is possible for a sparse-grooming network to achieve similar network performance as a network which has grooming capability at every node. We investigate the problem of designing such a sparse-grooming WDM mesh network. The problem is mathematically formulated and several design schemes are proposed. Illustrative numerical results from the mathematical formulation as well as heuristics show that, by properly choosing the grooming nodes, a network with sparse-grooming capability can achieve good network performance and the network cost can be significantly reduced.

Location aided broadcast in wireless ad hoc network systems

Abstract: Ad hoc networks in wireless communications is a challenging field due to the constant change of network topology. Broadcast service in ad hoc networks is critical in supporting various important applications and message routing. We examine the problem of the traditional broadcast protocol (i.e., flooding) in mobile wireless ad hoc networks, also known as "broadcast storm problem". We introduce a location aided algorithm to compute the optimal local cover set without delay and without much communication overhead. Based on the algorithm, we propose three new location-aided broadcast protocols for ad hoc networks that compute the optimal local cover set for retransmissions on-the-fly. We compare and analyze the simulation results of our protocols and others. The results show that our new protocols save a significant amount of wireless bandwidth and consume less overhead.

A series of Hamiltonian cycle-based solutions to provide simple and scalable mesh optical network resilience

Abstract: A mesh optical resilience solution has many requirements, some of which conflict with others. This article highlights the issues relevant to mesh optical resilience and the challenges of meeting the myriad requirements. A series of Hamiltonian cycle-based solutions with different efficiency, complexity, and scalability trade-offs are introduced. Solutions for moderate-sized and large networks are differentiated with the former emphasizing simplicity and efficiency, and the latter stressing resilience from multiple simultaneous failures and isolation of failure events.

Apparatus, and associated method, for dynamically selecting frequency levels upon which to define communication channels in a radio communication system

Abstract: Apparatus (50), and associated method, for dynamically selecting frequencies upon which to define communication channels in a communication system (10), such as a wireless mesh network. Frequency levels are selected (56) for global use throughout the entire mesh network. And, frequency levels upon which to define local communication channels for individual nodes of the mesh network are also selectable (58).