Showing papers on "Wireless mesh network published in 2000"

AODV-BR: backup routing in ad hoc networks

Abstract: Nodes in mobile ad hoc networks communicate with one another via packet radios on wireless multihop links. Because of node mobility and power limitations, the network topology changes frequently. Routing protocols therefore play an important role in mobile multihop network communications. A trend in ad hoc network routing is the reactive on-demand philosophy where routes are established only when required. Most of the protocols in this category, however, use a single route and do not utilize multiple alternate paths. We propose a scheme to improve existing on-demand routing protocols by creating a mesh and providing multiple alternate routes. Our algorithm establishes the mesh and multipaths without transmitting any extra control message. We apply our scheme to the Ad-hoc On-Demand Distance Vector (AODV) protocol and evaluate the performance improvements by simulation.

Distribution of potential neighbor information through an ad hoc network

Abstract: A communication network includes plural nodes capable of receiving and issuing messages. Each node has actual neighboring nodes to which it is connected. At each node, network information is received from other nodes of the network. Information of potential neighboring nodes to which the node could possibly be connected is generated in the node in response to the network information received from other nodes of the network. A network information message issued from the node to the other nodes of the network that includes information of the potential neighboring nodes.

Communications protocol for packet data particularly in mesh topology wireless networks

Abstract: In a wireless mesh topology data communications network, a communications method having a type of handshaking protocol for data exchange. A portion of the protocol is synchronous, using a schedule of control channel sessions held at all mutually communicating nodes of the network and a portion of the protocol is asynchronous, relying upon gaps between control channel sessions for transmission of requested data. Nodes which are in line of sight relation request data from each other using a request to send message and a clear to send message. A requesting node sends an RTS message to a neighbor node with information about gaps specifying the location of requested data. A supplying node transmits a potential schedule for sending requested information and the requesting node sends a CTS message agreeing upon the schedule. The potential schedule includes a number of available gaps between known control channel sessions. Because transmissions are scheduled, rapidly switchable directional antennas at requesting and supplying nodes may be used with good advantage.

Self-organizing, self-healing wireless networks

Abstract: Self-organizing, self-healing networks-also called "ad hoc" networks-are perhaps the most exciting new trend in networking research and development. Every node in such a network has sufficient intelligence to continuously sense and discover other nearby nodes, dynamically determine the optimal path for forwarding data packets from itself hop by hop through the network to any other node in the network, and automatically heal any ruptures in the network fabric that are caused by ongoing movement of the nodes themselves, changes in RF propagation, destruction of nodes, etc. In essence, one need merely launch such radio nodes into some space and they will not only organize themselves into a network but also adapt continuously to changes in the network's connectivity. The field is currently evolving at "Internet speed"-the first large-scale systems are now being fielded into the US military and yet many of the field's research fundamentals are at present only very poorly understood. This paper begins with an example that introduces some of the fundamental issues for ad hoc networks (hidden terminals, channel access, mobility, scalability, and power constraints). It then discusses the two dominant approaches in current ad hoc networking technologies, "proactive" and "on-demand" path discovery, and compares the strengths and weaknesses of each approach. The paper then presents two brief case studies with which the authors were involved-of a 400-node, terrestrial, vehicle-based system and of a high-capacity voice and data network deployed among drone aircraft-and concludes with highlights of the current research topics in the field.

Method and apparatus for connection handoff between connected radios

Abstract: In a radio based wireless mesh packet network wherein packet traffic is scheduled between a high capacity communications link and a plurality of nodes interconnected by wireless links, an access unit is provided at a first node having a plurality of radios coupled to the high capacity link and wherein each of the plurality of radios is capable of detecting a polling of the access unit by other nodes. A poll is sent from a second node to the access unit at the first node on a first channel. Reports of receipt of the poll are shared among the plurality of radios. An acknowledgment is sent on behalf of the access unit from only one of the plurality of radios to the polling node, and further communication is conducted between the one of the plurality of radios and the node on a second channel.

Experimental evaluation of a wireless ad hoc network

Abstract: We experimentally evaluate the performance of a wireless ad hoc network from the point of view of both the routing and transport layers. The experiments are done on a testbed with desktop PCs and laptops using wireless radio LAN interfaces. For these experiments an on-demand routing protocol called AODV (ad hoc on-demand distance vector) has been implemented as a part of the operating system protocol stack. We describe our design choices and the experimental setup. The performance evaluation reveals that the performance is poor beyond two hops at moderate to high loads.

Mesh networks; a new architecture for broadband wireless access systems

Abstract: This paper describes the attributes and practical realisation of mesh architectures for broadband wireless access (BWA) deployment. The mesh concept eliminates the need for base stations and instead uses an arrangement of short point-to-point connections that evolves as subscribers join the system. This inherently simple concept can be developed to produce systems with many attractive advantages for operators and subscribers. Future services will require high data rates, complete flexibility in the ratio of traffic received to traffic sent, low cost equipment and capability to reach virtually any subscriber who wants service. As deployment moves from the relatively high revenue business subscriber towards mass-market deployment, issues such as high levels of coverage, spectral efficiency, capacity, co-existence and ease of deployment become increasingly important. Mesh solutions offer substantial benefits in all these areas.

Topology Discovery in Ad Hoc Wireless Networks Using Mobile Agents

Abstract: Extensive research on mobile agents has been rife with the growing interests in network computing. In this paper, we have discussed a mobile multi-agent-based framework to address the aspect of topology discovery in ad hoc wireless network environment. In other words, we have designed a multi-agent based protocol to make the nodes in the network topology aware. Our primary aim is to collect all topology-related information from each node in the network and distribute them periodically (as updates) to other nodes through mobile agents. The notion of stigmergic communication has been used through the implementation of a shared information cache in each node. Moreover, we have defined a concept of link stability and information aging based on which a predictive algorithm running on each node can predict the current network topology based on the current network information stored at that node. We have demonstrated through performance evaluation of a simulated system that the use of mobile multi-agent framework would be able to make each node in the network topology aware, without consuming large portion of network capacity. As a direct outcome of infiltrating topology information into the nodes, the foundations for designing efficient routing scheme, distributed network management and implementing communication awareness get automatically laid.

Self-organizing, self-healing wireless networks

Abstract: Self-organizing, self-healing networks, also called "ad hoc" networks, are perhaps the most exciting new trend in networking research and development. Every node in such a network has sufficient intelligence to continuously sense and discover other nearby nodes, dynamically determine the optimal path for forwarding data packets from itself hop by hop through the network to any other node in the network, and automatically heal any ruptures in the network fabric that are caused by ongoing movement of the nodes themselves, changes in RF propagation, destruction of nodes, etc. In essence; one need merely launch such radio nodes into some space and they will not only organize themselves into a network but also adapt continuously to changes in the network's connectivity. The field is currently evolving at "Internet speed" - the first large-scale systems are now being fielded into the USA military and yet many of the field's research fundamentals are at present only very poorly understood. This paper begins with an example that introduces some of the fundamental issues for ad hoc networks (hidden terminals, channel access, mobility, scalability, and power constraints). It then discusses the two dominant approaches in current ad hoc networking technologies, "proactive" and "on-demand" path discovery, and compares the strengths and weaknesses of each approach. The paper then presents two brief case studies with which the authors were intimately involved - of a 400-node, terrestrial, vehicle-based system and of a high-capacity voice and data network deployed among drone aircraft - and concludes with highlights of the current research topics in the field.

Ad hoc network capacity

Abstract: We study the performance of wireless ad hoc networks in the limit of a large number of nodes. We first define ad hoc networks and their capacity. We then calculate a lower bound on the capacity by constructing a communications scheme that achieves it. We also determine an upper bound on the capacity by investigating the properties of any transmission schedule. Bounds indicate that for a large number of nodes n, the total network capacity increases with a rate between k/sub 1/n/sup 1/3/ and k/sub 2/n/sup 1/2/, while the per-node rate goes to zero.

Self configuring high throughput medium access control for wireless networks

Abstract: A network architecture that coordinates shared access to a wireless transmission medium while avoiding collisions between simultaneous transmissions even where network nodes cannot hear one another. There is also the capability of readily reconfiguring a wireless network to accommodate new nodes. In one embodiment, there is a hierarchy of master nodes that coordinate wireless transmissions by the other nodes. Since the need for retransmission is minimized, throughput is improved.

Ring-mesh networks

Abstract: A ring-mesh network architecture is provided for increasing the working/protection bandwidth ratio (W/PBR) of transport networks. The ring-mesh network has mesh connections between some nodes, the traffic on the mesh connections being unprotected. This increases the W/PBR from the current 1:2 value to (n−2)/(n−1), where n is the number of nodes, (n−1) is the number of connections on each node and (n−2) is the number of working connections on each node for one direction of traffic. Ring-mesh networks with add/drop multiplexers in the mesh connection are also provided.

All-optical network with passive wavelength routers

Abstract: An optical network, which may be an all-optical network, including passive wavelength routers is described. Methods for implementing such networks as well as different router configurations which may be used in optical networks are also disclosed. The routing functionality in the all-optical network can be done in the optical domain without switching elements at the nodes. This is achieved by routers which are passive and preferably operative to route wavelength bands. A mesh can be used as the network configuration. The optical networks described can be used to facilitate the transmission of higher network protocols, such as internet protocol (IP) packets or ATM-cells, purely in the optical domain.

Balancing traffic load for multi-node multicast in a wormhole 2D torus/mesh

Abstract: This paper considers the multi-node multicast problem in a wormhole-routed 20 torus/mesh, where an arbitrary number of source nodes each intending to multicast a message to an arbitrary, set of destinations. To resolve the contention and the congestion problems, we propose to partition the network into subnetworks to distribute, and thus balance, the traffic load among all network links. Several ways to partition the network are explored. Simulation results show significant improvement over existing results for torus and mesh networks.

Multicasting sustained CBR and VBR traffic in wireless ad-hoc networks

Abstract: Wireless ad-hoc networks consist of mobile nodes forming a dynamically changing topology without any infrastructure. Multicasting in a wireless ad-hoc network is difficult and challenging. We propose a novel protocol, the Wireless Ad-hoc Real-Time Multicast (WARM) protocol, for multicasting real-time (CBR and VBR) data among nodes in a wireless ad-hoc network. The protocol is distributed, highly adaptive and flexible. Multicast affiliation is receiver initiated. The messaging is localized to the neighborhood of the receiving multicast member and thus the overhead consumed is low. The protocol enables spatial bandwidth reuse along a multicast mesh (a connected structure of multicast group members). The real time connection is guaranteed quality of service (QoS) in terms of bandwidth. For VBR traffic, a combination of reserved and random access mechanisms are used. The protocol is self-healing in the sense that the mesh structure has the ability to repair itself when members either move or relays fail. We present simulation results to demonstrate features of the protocol and show that the throughput is above 90% for pedestrian environments.

Performance evaluation of a wireless ad hoc network: flexible radio network (FRN)

Abstract: In an ad hoc wireless network system, wireless terminals can autonomously construct a network and directly communicate with each other without using a wired network A flexible radio network is one of the ad hoc wireless network systems which has been operational in recent years In the flexible radio network, an original communication protocol is implemented to obtain reliability of communication We evaluate the performance by means of simulations for the data-link protocol and routing protocol of the flexible radio network We first show the performance when system parameters are changed to examine how these parameters affect the system performance Furthermore, we investigate the performance improvement by changing the network configuration

A method for communicating with multiple network nodes

Abstract: A method for communicating with multiple network nodes is provided in which each node of a network has a wireless link that allows data to travel to and from the nodes in parallel, thereby taking advantage of the inherent broadcast capabilities of wireless media. The wireless link may be used in parallel with a point-to-point, land-based network linking the nodes. The method may be used for multicasting or broadcasting data on a network. Specifically, the method may be used to maintain a network cache, a routing database and quality of service in a manner that is more efficient and reliable than previous methods that use serial protocols over point-to-point networks links.

Wireless technologies convergence: results and experience

Abstract: The wireless network evolution, delineated during the last years, has urged the necessity to extend the up-to-now static business environment to a mobile and wireless one. However, the current and forthcoming wireless technologies are characterized by different attributes regarding the coverage area, offered bandwidth and delay. The transparent conjunction of various wireless technologies into a single mobile terminal can further boost the wireless explosion. This paper presents the architectural approach and the results concerning the continuous connectivity and seamless switching between two complementary wireless networks, one 802.11-compliant in the short area and a CSM in the wide area. The described experiments were performed on an open, IP-based wireless architecture that can be easily extended to accommodate future wireless networks.

OctMesh-interactive mesh browsing over the Internet

Abstract: This paper proposes OctMesh, an interactive mesh browsing scheme over the Internet. In OctMesh, a large-scale mesh is encoded into one bit-stream, which is organized with respect to spatial locality and resolution. When the mesh is viewed over the Internet, by examining the user's viewpoint, the compressed mesh with desired locality and resolution is streamed to the client. OctMesh enables a large-scale mesh to be viewed quickly, over the Internet.

Protection cycle covers in optical networks with arbitrary mesh topologies

Abstract: A new methodology of finding cycle covers in networks with arbitrary mesh topologies is presented. The cycles that comprise the cycle cover are then used to protect the network against link and node failures.

Method and apparatus for communication between different wireless networks using a dual-power node

Abstract: A method and apparatus for internetworked communication between first and second wireless networks containing first and second pluralities of wireless nodes, respectively, is disclosed herein. In a preferred implementation a first dual-power node participates in both a first wireless network and an overlay network. The dual-power node is configured to transmit and receive in both a high-power mode and a low-power mode. The dual-power node operates in an overlay network and facilitates data transmission between low-power nodes and high-power nodes by toggling between these two power modes. In a preferred implementation, a third wireless network containing a third plurality of wireless nodes is utilized. The overlay network can accommodate a plurality of high-power or dual-power nodes.

Range adaptive protocols for wireless multi-hop networks

Abstract: Electrical Engineering (ABSTRACT) Recent accomplishments in link-level and radio technologies have significantly improved the performance of wireless links. Wireless mobile ad hoc networks, however, typically only take limited advantage of these enhancements. In this research, the medium access control protocol and ad hoc routing protocol are extended to take advantage of radios offering multiuser interference cancellation and direct-sequence spread-spectrum functionality, by encouraging multiple simultaneous connections and adaptively changing communication parameters on a per-packet basis. Through its environment characterization techniques, the adaptive direct sequence spread spectrum MAC protocol for non-broadcast multiple access networks (ADIM-NB) improves several aspects of the wireless mobile ad hoc network performance, including throughput, delay, stability, and power consumption, through its use of spread-spectrum multiple access and four different adaptive algorithms. The four adaptive algorithms change processing gain, forward error correction coding rate, transmit power, and number of simultaneous connections. In addition, the ad hoc routing protocol is extended with the clustering algorithm for mobile ad hoc network (CAMEN). With ADIM-NB in mind, CAMEN discourages the use of broadcast messages, supplements ADIM-NB's functionality at the network level, and improves the network scalability by aggregating nodes into clusters. Both protocols are intended to lead to more powerful and flexible communication capabilities for wireless nodes. Simulation models have been developed and simulated to verify the performance improvements of both protocols at the network-level as well as provide a means to perform trade-off analysis. Results indicate that the network capacity is increased between 50% in a moderately loaded network to 100% in a heavily loaded network over a non-adaptive MAC protocol. The delay also improve significantly in most scenarios of interest. III Acknowledgments I am eternally grateful for the assistance of many people involved in this research development. This research effort will not be materialized without their contributions. Chief among these is my advisor, Dr. Midkiff. I thank him for accepting me as one of his Ph.D. students. He was always there to provide invaluable guidance and support; and for that I am greatly indebted. Dr. Midkiff also goes well above and beyond his call of duty by always sharing with me every possible opportunity to improve myself in research and academic environments.

Routing and scheduling algorithms in resource-limited wireless multi-hop networks

Abstract: The recent advances in the area of wireless networking present novel opportunities for network operators to expand their services to infrastructure-less wireless systems. Such networks, often referred to as ad-hoc or multi-hop or peer-to-peer networks, require architectures which do not necessarily follow the cellular paradigm. They consist of entirely wireless nodes, fixed and/or mobile, that require multiple hops (and hence relaying by intermediate nodes) to transmit their messages to the desired destinations. The distinguishing features of such all-wireless network architectures give rise to new trade-offs between traditional concerns in wireless communications (such as spectral efficiency, and energy conservation) and the notions of routing, scheduling and resource allocation. The purpose of this work is to identify and study some of these novel issues, propose solutions in the context of network control and evaluate the usual network performance measures as functions of the new trade-offs. To these ends, we address first the problem of routing connection-oriented traffic with energy efficiency in all-wireless multi-hop networks. We take advantage of the flexibility of wireless nodes to transmit at different power levels and define a framework for formulating the problem of session routing from the perspective of energy expenditure. A set of heuristics are developed for determining end-to-end unicast paths with sufficient bandwidth and transceiver resources, in which nodes use local information in order to select their transmission power and bandwidth allocation. We propose a set of metrics that associate each link transmission with a cost and consider both the cases of plentiful and limited bandwidth resources, the latter jointly with a set of channel allocation algorithms. Performance is measured by call blocking probability and average consumed energy and a detailed simulation model that incorporates all the components of our algorithms has been developed and used for performance evaluation of a variety of networks. In the sequel, we propose a “blueprint” for approaching the problem of link bandwidth management in conjunction with routing, for ad-hoc wireless networks carrying packet-switched traffic. We discuss the dependencies between routing, access control and scheduling functions and propose an adaptive mechanism for solving the capacity allocation (at both the node-level and the flow-level) and the route assignment problems, that manages delays due to congestion at nodes and packet loss due to error prone wireless links, to provide improved end-to-end delay/throughput. The capacity allocations to the nodes and flows and the route assignments are iterated periodically and the adaptability of the proposed approach allows the network to respond to random channel error bursts and congestion arising from bursty and new flows.

Assignment of ADM Rings and DCS Mesh in Telecommunication Network

Abstract: This paper discusses a design of hybrid ring-mesh network in survivable communication network. Given a set of traffic demands, the problem is to assign each traffic demand to rings and mesh such that the cost of ADM and DCS equipments required is minimized. This assignment problem can be considered together with the fiber routing of nodes on rings and mesh. As a solution procedure, tabu search is developed with a recency based short term and a frequency based long term memory structure. In computational experiments, the proposed tabu search is compared with the solutions obtained by the branch and bound procedure of CPLEX. We see that the tabu search provides nearly optimal solution within sufficiently short time periods for all test problems with a gap of approximately 14% from the lower bound.

Throughput and delay analysis in an ad hoc wireless LAN using a token passing access method

Abstract: Research activities on wireless LANs, in particular the standardization work dealing with medium access methods (MAC sub-layer) give priority to CSMA principles. In this paper we are concerned with performance evaluation of a token passing access method applied to a wireless LAN without infrastructure (ad hoc network), composed of nomadic stations. Typically, in an ad hoc network, not all stations are within range of each other. Communications between hidden terminals make use of one or several relay nodes. The routing technique is based on using the local view which is specific to each station and updated thanks to observations made of the traffic ‘visible’ to each station. The study of the performances of such a network reveals a correlation between the throughput and end-to-end delay versus the mesh connectivity characteristics and the wealth of the knowledge of the local views. Copyright © 2000 John Wiley & Sons, Ltd.