Broadcasting is a common operation in a network to resolve many issues. In a mobile ad hoc network (MANET) in particular, due to host mobility, such operations are expected to be executed more frequently (such as finding a route to a particular host, paging a particular host, and sending an alarm signal). Because radio signals are likely to overlap with others in a geographical area, a straightforward broadcasting by flooding is usually very costly and will result in serious redundancy, contention, and collision, to which we call the broadcast storm problem. In this paper, we identify this problem by showing how serious it is through analyses and simulations. We propose several schemes to reduce redundant rebroadcasts and differentiate timing of rebroadcasts to alleviate this problem. Simulation results are presented, which show different levels of improvement over the basic flooding approach.

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The broadcast storm problem in a mobile ad hoc network

Advances in processor, memory, and radio technology will enable small and cheap nodes capable of sensing, communication, and computation. Networks of such nodes can coordinate to perform distributed sensing of environmental phenomena. In this paper, we explore the directed-diffusion paradigm for such coordination. Directed diffusion is data-centric in that all communication is for named data. All nodes in a directed-diffusion-based network are application aware. This enables diffusion to achieve energy savings by selecting empirically good paths and by caching and processing data in-network (e.g., data aggregation). We explore and evaluate the use of directed diffusion for a simple remote-surveillance sensor network analytically and experimentally. Our evaluation indicates that directed diffusion can achieve significant energy savings and can outperform idealized traditional schemes (e.g., omniscient multicast) under the investigated scenarios.

/pdf/directed-diffusion-for-wireless-sensor-networking-57x2fro512.pdf

Directed diffusion for wireless sensor networking

1 Introduction h this paper we introduce a new routing protocol for ad hoc networks built around two novel observations. One, called the distance eflect, usw the fmt that the greater the distance separating two nodes, the slower they appear to be moving with respect to each other. Accor@gly, the location information in routing tables can be updated as a function of the distance separating nodes without compromising the routing accuracy. The second idea is that of triggering the sending of location updates by the moving nodes autonomously, based ody on a node's mobility rate. htuitively, it is clear that in a direction routing dgorithrn, routing information about the slower moving nodes needs to be updated less frequently than that about hig~y mobtie nodw. h this way e~ node can optimize the frequency at which it sends updates to the networks and correspondingly r~ duce the bandwidth and energy used, leading to a fully distributed and self-optimizing system. B~ed on thwe routing tablw, the proposed direction algorithm sends messages in the " recorded dwectionn of the destination node, guaranteeing detivery by following the direction with a given probability. We show by detailed simda-tion that our protocol always delivers more than 80% of the data messages by following the direction computed, without using any recovery procedure. In addition, it mintilzes the overhead used for maintaining routes using the two new principlw of update message frequency and distance. Lastly, the dgorithrn is fully distributed, provides loop-free paths, and is robust, since it suppfies multiple routes. Pemlissiontomakedigitalorhsrdcopiesof allorpartof this\vorkfor personal or classroom use is granted without fee provided that copies are not mzde or dis~.buted for prolit or commercial ad~arrtageand that copies bcwrthis notice and the full citation on the first page. To copy othm}tise, to republish, to post on senrers or to redistribute to lists, requires prior specific permission an&'ora fee. 76 Rom a routing perspective, an ad hoc network is a packet radio network in which the mobile nodes perform the routing functions. Generdy, routing is multi-hop since nodes may not be within the wireless transmission range of one another and thus depend on each other to forward packets to a given destination. Since the topology of an ad hoc network changes frequently, a routing protocol should be a distributed algorithm that computes multiple, cycle free routes while keeping the communication overhead to a minimum (see, e.g., [4]). One way to …

A distance routing effect algorithm for mobility (DREAM)

Mobile ad hoc networks (MANETs) represent complex distributed systems that comprise wireless mobile nodes that can freely and dynamically self-organize into arbitrary and temporary, ‘‘ad-hoc’’ network topologies, allowing people and devices to seamlessly internetwork in areas with no pre-existing communication infrastructure, e.g., disaster recovery environments. Ad hoc networking concept is not a new one, having been around in various forms for over 20 years. Traditionally, tactical networks have been the only communication networking application that followed the ad hoc paradigm. Recently, the introduction of new technologies such as the Bluetooth, IEEE 802.11 and Hyperlan are helping enable eventual commercial MANET deployments outside the military domain. These recent evolutions have been generating a renewed and growing interest in the research and development of MANET. This paper attempts to provide a comprehensive overview of this dynamic field. It first explains the important role that mobile ad hoc networks play in the evolution of future wireless technologies. Then, it reviews the latest research activities in these areas, including a summary of MANETs characteristics, capabilities, applications, and design constraints. The paper concludes by presenting a set of challenges and problems requiring further research in the future. � 2003 Elsevier B.V. All rights reserved.

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Mobile ad hoc networking: imperatives and challenges

https://ir.nctu.edu.tw:443/bitstream/11536/29078/1/000174218000005.pdf

Fundamentals of Satellite Navigation. GPS Systems Segments. GPS Satellite Signal Characteristics and Message Formats. Satellite Signal Acquisitions and Tracking. Effects of RF Interference on GPS Satellite Signal Receiver Tracking. Performance of Standalone GPS. Differential GPS. Integration of GPS with other Sensors. Galileo. The Russian GLONASS, Chinese Bediou, and Japanese QZSS Systems. GNSS Markets and Applications.

Elliott D. Kaplan

Papers

Understanding GPS : principles and applications