Showing papers on "Optimized Link State Routing Protocol published in 1997"

A highly adaptive distributed routing algorithm for mobile wireless networks

Abstract: We present a new distributed routing protocol for mobile, multihop, wireless networks. The protocol is one of a family of protocols which we term "link reversal" algorithms. The protocol's reaction is structured as a temporally-ordered sequence of diffusing computations; each computation consisting of a sequence of directed link reversals. The protocol is highly adaptive, efficient and scalable; being best-suited for use in large, dense, mobile networks. In these networks, the protocol's reaction to link failures typically involves only a localized "single pass" of the distributed algorithm. This capability is unique among protocols which are stable in the face of network partitions, and results in the protocol's high degree of adaptivity. This desirable behavior is achieved through the novel use of a "physical or logical clock" to establish the "temporal order" of topological change events which is used to structure (or order) the algorithm's reaction to topological changes. We refer to the protocol as the temporally-ordered routing algorithm (TORA).

Signal stability-based adaptive routing (SSA) for ad hoc mobile networks

Abstract: Ad hoc networks have no spatial hierarchy and suffer from frequent link failures which prevent mobile hosts from using traditional routing schemes. Under these conditions, mobile hosts must find routes to destinations without the use of designated routers and also must dynamically adapt the routes to the current link conditions. This article proposes a distributed adaptive routing protocol for finding and maintaining stable routes based on signal strength and location stability in an ad hoc network and presents an architecture for its implementation. Interoperability with mobile IP (Internet protocol) is discussed.

Associativity-Based Routing for Ad Hoc Mobile Networks

Abstract: This paper presents a new, simple and bandwidth-efficient distributed routing protocol to support mobile computing in a conference size ad-hoc mobile network environment. Unlike the conventional approaches such as link-state and distance-vector distributed routing algorithms, our protocol does not attempt to consistently maintain routing information in every node. In an ad-hoc mobile network where mobile hosts (MHs) are acting as routers and where routes are made inconsistent by MHs‘ movement, we employ an associativity-based routing scheme where a route is selected based on nodes having associativity states that imply periods of stability. In this manner, the routes selected are likely to be long-lived and hence there is no need to restart frequently, resulting in higher attainable throughput. Route requests are broadcast on a per need basis. The association property also allows the integration of ad-hoc routing into a BS-oriented Wireless LAN (WLAN) environment, providing the fault tolerance in times of base stations (BSs) failures. To discover shorter routes and to shorten the route recovery time when the association property is violated, the localised-query and quick-abort mechanisms are respectively incorporated into the protocol. To further increase cell capacity and lower transmission power requirements, a dynamic cell size adjustment scheme is introduced. The protocol is free from loops, deadlock and packet duplicates and has scalable memory requirements. Simulation results obtained reveal that shorter and better routes can be discovered during route re-constructions.

A new routing protocol for the reconfigurable wireless networks

Abstract: We propose a new routing protocol, the Zone Routing Protocol (ZRP), for the reconfigurable wireless networks, a large scale, highly mobile ad-hoc networking environment. The novelty of the ZRP protocol is that it is applicable to large flat-routed networks. Furthermore, through the use of the zone radius parameter, the scheme exhibits the adjustable hybrid behavior of proactive and reactive routing schemes. We evaluate the performance of the protocol, showing the reduction in the number of control messages, as compared with other reactive schemes, such as flooding.

A cluster-based approach for routing in dynamic networks

Abstract: The design and analysis of routing protocols is an important issue in dynamic networks such as packet radio and ad-hoc wireless networks Most conventional protocols exhibit their least desirable behavior for highly dynamic interconnection topologies We propose a new methodology for routing and topology information maintenance in dynamic networks The basic idea behind the protocol is to divide the graph into a number of overlapping clusters A change in the network topology corresponds to a change in cluster membership We present algorithms for creation of clusters, as well as algorithms to maintain them in the presence of various network events Compared to existing and conventional routing protocols, the proposed cluster-based approach incurs lower overhead during topology updates and also has quicker reconvergence The effectiveness of this approach also lies in the fact that existing routing protocols can be directly applied to the network --- replacing the nodes by clusters

QoS routing mechanisms and OSPF extensions

Abstract: This paper presents and discusses path selection algorithms to support QoS routes in IP networks. The work is carried out in the context of extensions to the OSPF protocol, and the initial focus is on unicast flows, although some of the proposed extensions are also applicable to multicast flows. We first review the metrics required to support QoS, and then present and compare several path selection algorithms, which represent different trade-offs between accuracy and computational complexity. We also describe and discuss the associated link advertisement mechanisms, and investigate some options in balancing the requirements for accurate and timely information with the associated control overhead. The overall goal of this study is to identify a framework and possible approaches to allow deployment of QoS routing capabilities with the minimum possible impact to the existing routing infrastructure.

Routing in ad hoc networks using a spine

Abstract: We present a two-level hierarchical routing architecture for ad hoc networks. Within each lower level cluster, we describe a self-organizing, dynamic spine structure to (a) propagate topology changes, (b) compute updated routes in the background, and (c) provide backup routes in case of transient failures of the primary routes. We analyze and bound the worst case of movements between upper level clusters to show that this hierarchical architecture scales well with network size.

A system and traffic dependent adaptive routing algorithm for ad hoc networks

Abstract: An ad hoc network consists of a number of mobile hosts who communicate with each other over a wireless channel without any centralized control. The basic problem is to obtain a distributed routing scheme so that under the network connectivity assumption any mobile host can transmit/receive data from any other host in the network. In this paper we propose a new routing algorithm for ad hoc networks. The proposed algorithm uses a more appropriate distance measure given by the expected delay along a path, instead of the number of hops used in most of the existing algorithms. This metric allows the algorithm to adapt to changes not only in the topology of the network, but also in the traffic intensity. The algorithm uses a novel technique for estimating the path delays without requiring the links to be bidirectional or the clocks at the nodes in the network to be synchronized. The proposed algorithm is able to perform both reliable and good routing with low communication overhead and computational requirements.

Performance of optimized routing in LEO intersatellite link networks

Abstract: An ATM based routing concept for LEO intersatellite link networks is proposed. The challenges arising from the complex time-variant ISL network topology are tackled by a discrete-time network model and routing procedure. The approach is based on the combination of a modified standard routing scheme and the ATM VPC concept. The routing scheme works completely off-line, i.e. prior to system operation. In a first step, a virtual topology is set up for all successive time intervals, providing instantaneous sets of alternative VPCs (paths) between all source-destination satellite pairs. In the second step, path sequences over a series of time intervals are chosen from that according to a certain optimization procedure. Two different optimization procedures are discussed in detail, and a numerical performance evaluation is presented for telephony service in an example ISL network (Iridium). The overall routing performance is evaluated in terms of remaining delay jitter due to inevitable path handover. The results show that optimized routing strategies are specifically capable of minimizing severe delay jitter, and thus in turn reduce the complexity of ATM based operation in a connection-oriented service environment.

A new hierarchical routing protocol for dynamic multihop wireless networks

Abstract: The routing techniques used in conventional packet radio networks are not suitable for dynamic multihop wireless networks because of their unique architecture. In this paper a new hierarchical multihop routing algorithm is introduced which balances the cost of location-update and path-finding operations by partitioning the terminals and mobile base stations to produce a virtual topology. Based on the virtual topology each network entity stores a fraction of the network topology information and maintains the routing efficiency. Finally, the performance of the hierarchical multihop routing algorithm is investigated through simulations.

Using Location Information to Improve Routing in Ad Hoc Networks

Abstract: In ad hoc network environments, any techniques to reduce high routing-related overhead are worth investigating. This brief note explains how to exploit location information to improve ad hoc routing. We also suggest some optimization approaches that can improve the performance of the protocol.

Issues in Supporting Quality of Service in Mobile Ad Hoc Networks

Abstract: This paper addresses issues in supporting Quality of Service (QoS)-based delivery in mobile ad hoc networks. It first describes the generic character of mobile ad hoc networks (a.k.a. mobile packet radio networks), some ways in which they differ from non-wireless multihop networks, and the impact these differences have on supporting QoS-based delivery. It then briefly gives some thoughts on supporting QoS in these systems.

Mutual Exclusion on Multihop, Mobile Wireless Networks

Abstract: The system considered in this paper is a mobile wireless network, commonly known as an ad hoc network. Mobile nodes in this dynamic topology function both as processors and routers to provide communication between nodes which are not within wireless transmission range. We present a token based mutual exclusion algorithm designed for an ad hoc distributed system. This mutual exclusion algorithm modifies a logical tree structure when link failures occur or when the token moves, thereby adapting to node mobility.

A Routing Protocol for Physically Hierarchical Ad Hoc Networks

Abstract: Several routing schemes proposed for ad hoc networks assume that all mobile hosts have the same transmission power and bandwidth constraints. However, in real world, this assumption may often not be true since there exist many types of mobile hosts with different transmission capacity and mobility rate. This paper discusses a new ad hoc network architecture, called `Physically Hiera rchical Ad Hoc Networks'' where two kinds of mobile hosts form the ad hoc network hierarchy: Super Mobile Hosts(Super-MHs) and Mini Mobile Hosts (Mini-MHs). The paper presents a protocol for routing in such a network. The protocol is based on the idea that most communication between Mini-MHs can be provided through a Super-MH playing the role of mobile base station for Mini- MHs.

A distributed multicast routing protocol for ad-hoc (flat) mobile wireless networks

Abstract: "Multicasting" refers to the transmission of the same information to several destinations. We present a loop-free, distributed multicast routing protocol for wireless networks that consist of an arbitrarily large number of nodes, each of which is mobile in an unpredictable manner. Most existing multicast protocols have been developed for non-wireless, stationary networks in which there is an abundance of bandwidth and where intended destinations initiate their connection to the multicast tree. In mobile wireless networks of the future, bandwidth may be limited if not scarce, and in addition to destination initiated connections, there will be purely source-initiated multicasts. We propose a combined multicast routing and resource reservation protocol, which is source-initiated and which uses dynamic frequency allocation to establish, and maintain, connections to desired destinations in the randomly varying topology of ad-hoc wireless networks. Power control is applied to tradeoff between routing delays and frequency reuse factor.

A dynamic routing protocol for broadband networks

Abstract: An efficient dynamic routing protocol is necessary for future broadband networks where a variety of services with different characteristics and QoS requirements are integrated. The main components of a dynamic routing protocol are the exchange of topology state information, the routing algorithm and the routing decision. The exchange of topology state information helps in keeping the network nodes updated on the network status and hence making the correct routing decision. The routing algorithm is responsible for computing the best paths for different source-destination pairs. The routing decision taken at a node decides the path to be followed by a certain call. Different alternatives are possible in the design of each of these components leading to different scenarios for the routing protocol. These different scenarios are examined based on both analytical and/or simulation results and the one with the best results in terms of efficiency as well as various performance measures is presented. The simulation is carried out over a practical network topology; the NSFNET.

The Cambridge Ad-Hoc Mobile Routing Protocol

Abstract: This chapter is concerned with the protocol aspects for ad-hoc mobile networks. In particular, it reveals what are the problems associated with routing in such networks. Although several routing schemes have been proposed, most of them are modified extensions of existing link-state or distance-vector based routing protocols. However, in an ad-hoc mobile network where mobile hosts are acting as routers and have both power and bandwidth constraints, conventional routing protocols which employ periodic broadcast are unlikely to be suitable. Consequently, there is a need for a simple, bandwidth-efficient and robust routing protocol for ad-hoc mobile networks.

PNNI routing support for ad hoc mobile networking: A flat architecture

Abstract: This contribution extends the Outside Nodal Hierarchy List (ONHL) procedures described in ATM Form Contribution 97-0766. These extensions allow multiple mobile networks to form either an ad hoc network or an extension of a fixed PNNI infrastructure. This contribution covers the simplest case where the top-most Logical Group Nodes (LGNs), in those mobile networks, all reside at the same level in a PNNI hierarchy. Future contributions will cover the general case where those top-most LGNs reside at different hierarchy levels. This contribution considers a flat ad hoc network architecture--in the sense that each mobile network always participates in the PNNI hierarchy at the preconfigured level of its top-most LGN.

A new highly efficient multicast protocol on ad hoc network under slow fading environments

Abstract: This paper proposes a new data link layer protocol for multicast communications on ad hoc TDMA mobile networks, which accomplishes highly efficient transmission throughput in slow fading environments. The ad hoc network structure assumed in this paper is a network with a proxy access point which relays broadcasting messages among the terminals. The proposed multicast data link protocol integrates a retransmission control function with a flow control function by a collision based procedure. This collision based procedure using a negative acknowledgement (NAK) message can improve throughput owing to the effective retransmission achieved by the NAK message. Moreover, the proposed protocol achieves the flow control function by introducing the collision procedure of the NAK message with a sending message from a sender in order to facilitate a complete transmission guarantee in the upper layer. Its throughput performance is evaluated by computer simulations in applying this protocol to the Japanese Personal Handyphone System (PHS). It is shown that, under the conditions of 1% frame error rate (which can be considered as the mobile groupware condition) the realizable effective transmission rate is about 28 kbps with a physical layer transmission rate of 32 kbps, and it suffers from no degradation regardless of the network layer packet length or the number of the group members.