We consider the problem of adjusting the transmit powers of nodes in a multihop wireless network (also called an ad hoc network) to create a desired topology. We formulate it as a constrained optimization problem with two constraints-connectivity and biconnectivity, and one optimization objective-maximum power used. We present two centralized algorithms for use in static networks, and prove their optimality. For mobile networks, we present two distributed heuristics that adaptively adjust node transmit powers in response to topological changes and attempt to maintain a connected topology using minimum power. We analyze the throughput, delay, and power consumption of our algorithms using a prototype software implementation, an emulation of a power-controllable radio, and a detailed channel model. Our results show that the performance of multihop wireless networks in practice can be substantially increased with topology control.

Topology control of multihop wireless networks using transmit power adjustment

We present an overview of ad hoc routing protocols that make forwarding decisions based on the geographical position of a packet's destination. Other than the destination's position, each node need know only its own position and the position of its one-hop neighbors in order to forward packets. Since it is not necessary to maintain explicit routes, position-based routing does scale well even if the network is highly dynamic. This is a major advantage in a mobile ad hoc network where the topology may change frequently. The main prerequisite for position-based routing is that a sender can obtain the current position of the destination. Therefore, previously proposed location services are discussed in addition to position-based packet forwarding strategies. We provide a qualitative comparison of the approaches in both areas and investigate opportunities for future research.

A survey on position-based routing in mobile ad hoc networks

This paper describes a self-organizing, multihop, mobile radio network which relies on a code-division access scheme for multimedia support. In the proposed network architecture, nodes are organized into nonoverlapping clusters. The clusters are independently controlled, and are dynamically reconfigured as the nodes move. This network architecture has three main advantages. First, it provides spatial reuse of the bandwidth due to node clustering. Second, bandwidth can be shared or reserved in a controlled fashion in each cluster. Finally, the cluster algorithm is robust in the face of topological changes caused by node motion, node failure, and node insertion/removal. Simulation shows that this architecture provides an efficient, stable infrastructure for the integration of different types of traffic in a dynamic radio network.

Adaptive clustering for mobile wireless networks

This document provides updates to IEEE Std 802.16's MIB for the MAC, PHY and asso- ciated management procedures in order to accommodate recent extensions to the standard.

IEEE Standard for Local and Metropolitan Area Networks Part 16: Air Interface for Fixed Broadband Wireless Access Systems Draft Amendment: Management Information Base Extensions

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

This paper presents a model for analyzing the performance of transmission strategies in a multihop packet radio network where each station has adjustable transmission radius. A larger transmission radius will increase the probability of finding a receiver in the desired direction and contribute bigger progress if the transmission is successful, but it also has a higher probability of collision with other transmissions. The converse is true for shorter transmission range. We illustrate our model by comparing three transmission strategies. Our results show that the network can achieve better performance by suitably controlling the transmission range. One of the transmission strategies, namely transmitting to the nearest forward neighbor by using adjustable transmission power, has desirable features in a high terminal density environment.

Transmission Range Control in Multihop Packet Radio Networks

The ad hoc network is a temporary wireless system without a fixed (wired or wireless) infrastructure. Many clustering algorithms have been proposed to partition mobile users into clusters to support routing and network management. Most previous studies, however, focus on algorithm design, lacking an overall evaluation of clustering overheads. We design a multiple access scheme for the broadcast of control messages, and propose a new access-based clustering protocol (ABCP) whose cluster formation is heavily influenced by the outcome of the multiple access. By taking into account many delicate aspects in the clustering process, the ABCP provides a generic, flexible, rapidly deployed and stable cluster architecture for the upper layer protocols. Simulation is used to compare ABCP with the other clustering strategy in terms of cluster stability and overheads. Since ABCP makes clustering decision directly based on the result of channel access, it requires fewer control overheads and has shorter convergence time than the other clustering criteria. We also demonstrate that the resulting cluster structure by ABCP behaves stable in face of topology changes.

A access-based clustering protocol for multihop wireless ad hoc networks

Broadband packet switches handling an asynchronous-time-division-multiplexing type protocol format, e.g. Starlite, can achieve buffer efficiencies by sharing buffers between output ports. It is shown that the number of buffers required with sharing, for random traffic, would be overestimated by as much as 30% at 90% traffic load if the negative correlations that naturally exist, for this type of traffic, between packet streams destined for different output ports were not taken into account. In general, the discrepancy increases as the traffic load increases, and decreases as the switch size increases. A general approach is developed for the analysis of set of queues to which the arrival streams are correlated, which could be used to assess the impacts on shared buffer requirements due to other types of stream correlation (e.g. positive correlations) that may result from other traffic assumptions. >

Effects of output buffer sharing on buffer requirements in an ATDM packet switching

Mixed continuous-bit-rate (CBR) and bursty traffic contending for transmission on any output line of a broadband switch based on the asynchronous transfer mode (ATM) is modeled as a superposition of traffic from a number of independent random and binary sources. With the use of a recursive algorithm, a complete queuing analysis is presented. The queue length distribution, the delay distribution, and the cell loss probability for a finite buffer system are exactly calculated. Cases considered and analyzed include: delay priority for CBR traffic, absolute cell loss priority for DS1/DS3 emulation or guaranteed bandwidth CBR traffic with a stringent cell loss requirement, and threshold cell dropping for voice CBR traffic with a high degree of cell loss tolerance. >

Queueing analysis for ATM switching of mixed continuous-bit-rate and bursty traffic

In this paper, we analyze the throughput of the IEEE 802.11 DCF scheme using the RTS/CTS access mechanism in multi-hop ad hoc networks. The mathematical analysis is much more involved than that in a single-hop network due to the hidden node problem. A more realistic carrier sense range is considered in this paper. The impact of parameters, such as the number of stations, the packet size, and the carrier sense range, is also considered. Simulation results show good agreement with the analytical results.

Ting-Chao Hou

Papers

Transmission Range Control in Multihop Packet Radio Networks

A access-based clustering protocol for multihop wireless ad hoc networks

Effects of output buffer sharing on buffer requirements in an ATDM packet switching

Queueing analysis for ATM switching of mixed continuous-bit-rate and bursty traffic

Analyzing the throughput of IEEE 802.11 DCF scheme with hidden nodes