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.

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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.

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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.

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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

We formulate the interaction between link connectivity and hostile interference in a wireless system as a nonzero-sum two-player game. One player is the transmitter aiming to maintain the connections to its receivers, whereas the other player is the interferer aiming to disrupt the connections. The players’ strategies are their transmitted power levels. We focus on the case in which the ratio of the averages of the channel power gains for the transmitter and interferer are the same at all receivers. We then provide closed-form expressions for the Nash and Stackelberg equilibria. When the channel is affected by Rayleigh fading, we show that both players have the same power cost at Nash equilibria. In addition, the Stackelberg strategies dominate the Nash strategies, that is, the utility functions of the Stackelberg equilibria exceed or equal those of the Nash equilibria.

Impact of Hostile Interference on Wireless Link Connectivity

Most studies of wireless random-access systems have addressed single-destination networks (e.g., an isolated base station in a cellular network). Here, we consider networks with multiple destinations, where transmissions intended for one destination can interfere with those intended for others. In our earlier work on stabilized slotted Aloha in a symmetrical two-destination system, we derived analytically an invariance result that states that the maximum overall throughput is obtained when the channel traffic is equal to one packet per slot at each of the two destinations. The value of throughput that is achieved at this optimal point depends on the degree of overlap between the two regions, i.e., on the level of interference at each destination that is caused by packets that were intended for the other destination. In this paper, we generalize our results by presenting a complete analysis for two-destination systems that are characterized by an interference model in which interference range exceeds communication range.

Performance evaluation of random access in wireless networks with multiple destinations

We consider the problem of throughput maximization in circuit-switched networks, subject to quality of service (QoS) constraints on circuit blocking probability. We formulate an associated nonlinear optimization problem, which incorporates nonlinear inequality constraints, and develop a technique for guiding the search more directly toward the optimal solution. The resulting algorithm leads to faster and more reliable convergence over a variety of network instances.

http://ieeexplore.ieee.org/iel3/4303/12375/00572691.pdf

A problem of constrained optimization for bandwidth allocation in high-speed and wireless communication networks

The Advanced Research Projects Agency (ARPA) has initiated the Synthetic Theater of War (STOW) program to expand the current distributed interactive simulation (DIS) capability to handle larger exercises. Characterizations of the unclassified network traffic from the Synthetic Theater of War-Europe (STOW-E) demonstration are assessed in the context of self-similarity. At small time scales, the LAN traffic oscillates between burstiness and smoothness, whereas the WAN traffic exhibits smoothness. However, both the LAN and the WAN traffic exhibit high burstiness on larger time scales. Therefore, the traffic shows characteristics that would be produced by Poisson-type and self-similar processes. Additionally, in comparing the STOW-E traffic with an asymptotically self-similar process, we find that it has an unusually high Hurst parameter (i.e., H/spl sim/1). A simple mathematical model for the traffic is an uncorrelated process whose parameters vary according to another asymptotically self similar process of high burstiness. Since a combination of self-similar processes results in an asymptotically self-similar process, we conjecture that future STOW traffic should behave as asymptotically modulated self-similar processes.

Statistical characteristics of DIS traffic

In this work, we model a random access multicast network with cooperative relaying and analyze its throughput. The network consists of two source nodes and two destination nodes, where both source nodes generate data that needs to be transmitted to both destination nodes. We study the possibility that one of the sources can also act as a cooperative relay by transmitting some of the packets originating at the other source node. It is assumed that the destination nodes are equipped with multiuser detectors, and hence are capable of successfully decoding transmissions from multiple source nodes simultaneously (multipacket reception). We derive the achievable service rates for packets originating at each node in a system with cooperative relaying, and thereby compute the overall throughput region. Further analysis of the system (stability region) is reserved for future work.

Gam D. Nguyen

Papers

Impact of Hostile Interference on Wireless Link Connectivity

Performance evaluation of random access in wireless networks with multiple destinations

A problem of constrained optimization for bandwidth allocation in high-speed and wireless communication networks

Statistical characteristics of DIS traffic

Wireless multicast with cooperative relaying