A 2001 IBM manifesto observed that a looming software complexity crisis -caused by applications and environments that number into the tens of millions of lines of code - threatened to halt progress in computing. The manifesto noted the almost impossible difficulty of managing current and planned computing systems, which require integrating several heterogeneous environments into corporate-wide computing systems that extend into the Internet. Autonomic computing, perhaps the most attractive approach to solving this problem, creates systems that can manage themselves when given high-level objectives from administrators. Systems manage themselves according to an administrator's goals. New components integrate as effortlessly as a new cell establishes itself in the human body. These ideas are not science fiction, but elements of the grand challenge to create self-managing computing systems.

The vision of autonomic computing

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.

/pdf/mobile-ad-hoc-networking-imperatives-and-challenges-56mord86q0.pdf

Mobile ad hoc networking: imperatives and challenges

Topology Control (TC) is one of the most important techniques used in wireless ad hoc and sensor networks to reduce energy consumption (which is essential to extend the network operational time) and radio interference (with a positive effect on the network traffic carrying capacity). The goal of this technique is to control the topology of the graph representing the communication links between network nodes with the purpose of maintaining some global graph property (e.g., connectivity), while reducing energy consumption and/or interference that are strictly related to the nodes' transmitting range. In this article, we state several problems related to topology control in wireless ad hoc and sensor networks, and we survey state-of-the-art solutions which have been proposed to tackle them. We also outline several directions for further research which we hope will motivate researchers to undertake additional studies in this field.

/pdf/topology-control-in-wireless-ad-hoc-and-sensor-networks-3e17u396zt.pdf

Topology Control in Wireless Ad Hoc and Sensor Networks

Mobile ad hoc networking has been an active research area for several years. How to stimulate cooperation among selfish mobile nodes, however, is not well addressed yet. In this paper, we propose Sprite, a simple, cheat-proof, credit-based system for stimulating cooperation among selfish nodes in mobile ad hoc networks. Our system provides incentive for mobile nodes to cooperate and report actions honestly. Compared with previous approaches, our system does not require any tamper-proof hardware at any node. Furthermore, we present a formal model of our system and prove its properties. Evaluations of a prototype implementation show that the overhead of our system is small. Simulations and analysis show that mobile nodes can cooperate and forward each other's messages, unless the resource of each node is extremely low.

/pdf/sprite-a-simple-cheat-proof-credit-based-system-for-mobile-2xgda04los.pdf

Sprite: a simple, cheat-proof, credit-based system for mobile ad-hoc networks

Gathering sensed information in an energy efficient manner is critical to operating the sensor network for a long period of time. The LEACH protocol presented by Heinzelman et al. (2000) is an elegant solution where clusters are formed to fuse data before transmitting to the base station. In this paper, we present an improved scheme, called PEGASIS (power-efficient gathering in sensor information systems), which is a near-optimal chain-based protocol that minimizes energy. In PEGASIS, each node communicates only with a close neighbor and takes turns transmitting to the base station, thus reducing the amount of energy spent per round. Simulation results show that PEGASIS performs better than LEACH. For many applications, in addition to minimizing energy, it is also important to consider the delay incurred in gathering sensed data. We capture this with the energy /spl times/ delay metric and present schemes that attempt to balance the energy and delay cost for data gathering from sensor networks. We present two new schemes to minimize energy /spl times/ delay using CDMA and non-CDMA sensor nodes. We compared the performance of direct, LEACH, and our schemes with respect to energy /spl times/ delay using extensive simulations for different network sizes. Results show that our schemes perform 80 or more times better than the direct scheme and also outperform the LEACH protocol.

/pdf/data-gathering-algorithms-in-sensor-networks-using-energy-3vwrde95ey.pdf

Data gathering algorithms in sensor networks using energy metrics

This paper addresses fundamental issues in a shared channel where the users have different priority levels. In particular, we study a two-user cognitive shared channel consisting of a primary (higher-priority) and a secondary user, operating in the cognitive underlay fashion, but in a novel way where interference suffered by the primary user is compensated by requiring the secondary user to cooperatively relay some of the primary's packets. We start by analyzing the case of no node cooperation, where nodes transmit their own packets to their respective destinations. We then extend the analysis to a system in which the secondary node acts as a relay for the primary user, in addition to serving its own packets. Specifically, in the cognitive cooperation case, the secondary node forwards those packets to the primary destination that it receives successfully from the primary source. In such cognitive shared channels, a tradeoff arises in terms of activating the secondary along with the primary so that both transmissions may be successful, but with a lower probability, compared to the case of the secondary node staying idle when the primary user transmits. Results show the benefits of relaying for both the primary as well as the secondary nodes in terms of the stable-throughput region.

Cooperation in cognitive underlay networks: stable throughput tradeoffs

Addresses the impact of resource limitations on the operation and performance of the broadcasting and multicasting schemes developed for infrastructureless wireless networks in our earlier studies (2000, 2001). These schemes, which provide energy-efficient operation for source-initiated session traffic, were previously studied without fully accounting for such limitations. We discuss the "node-based" nature of the all-wireless medium and demonstrate that improved performance can be obtained when such properties are exploited by networking algorithms. Our broadcast and multicast algorithms involve the joint choice of transmitter power and tree construction, and thus depart from the conventional approach that makes design choices at each layer separately. We indicate how the impact of limited frequency resources can be addressed. Alternative schemes are developed for frequency assignment, and their performance is compared under different levels of traffic load, while also incorporating the impact of limited transceiver resources.

/pdf/resource-limited-energy-efficient-wireless-multicast-of-3k5rjevxqs.pdf

Resource-limited energy-efficient wireless multicast of session traffic

We address the problem of multicasting in military "ad-hoc" wireless networks. Since such networks lack a fixed cellular infrastructure, multicast algorithms that are based on the availability of fixed, known topologies cannot be used effectively. Even when the locations of the nodes are fixed and known, the properties of the wireless medium create a networking environment that is vastly different from that of wired networks, and for which the multicasting problem has scarcely been addressed. Specifically, the broadcast nature of wireless transmission and the dependence of range on the transmission power create new opportunities for multicasting that need to be traded off against the interference caused by such transmissions. We address the ways in which the wireless network characteristics, as well as the constraints of limited energy, affect the multicast protocol operation. Preliminary trade-offs are provided, and future research directions are outlined.

Multicasting in energy-limited ad-hoc wireless networks

The broadcast incremental power (BIP) algorithm is a centralized heuristic for the construction of energy-efficient broadcast trees in wireless networks. We discuss the issues associated with the development of distributed algorithms for broadcast tree construction, and develop and evaluate several versions of distributed BIP (Dist-BIP). We compare the performance of these schemes with that of both centralized BIP and minimum-cost spanning tree (MST) algorithm.

The energy efficiency of distributed algorithms for broadcasting in ad hoc networks

Previously, we developed the broadcast incremental power (BIP) algorithm (Wieselthier, J.E. et al., Proc. IEEE INFOCOM 2000, p.585-94, 2000; Mobile Networks and Applications (MONET), vol.7, no.6, 2002), which is a centralized heuristic for energy-efficient broadcasting of source-initiated session-based traffic in wireless networks. This algorithm, which exploits the characteristics of the wireless channel, was shown to perform better than adaptations of conventional algorithms that were originally developed for wired networks. However, as a consequence of its centralized nature, it is "expensive" in terms of both communication and computation requirements. We now develop two distributed versions of BIP, and compare their performance to that of centralized BIP and to an algorithm based on the minimum-cost spanning tree formulation.

Gam D. Nguyen

Papers

Cooperation in cognitive underlay networks: stable throughput tradeoffs

Resource-limited energy-efficient wireless multicast of session traffic

Multicasting in energy-limited ad-hoc wireless networks

The energy efficiency of distributed algorithms for broadcasting in ad hoc networks

Distributed algorithms for energy-efficient broadcasting in ad hoc networks