Jeffrey S. Wysocarski

Energy-efficient transmission and routing protocols for wireless multiple-hop networks and spread-spectrum radios

We describe link and network layer protocols that can conserve energy in store-and-forward packet radio networks. At the link layer, an adaptive-transmission protocol allows the radios to adjust the power in the transmitted signal and the information rate to respond to variations in interference and propagation loss. The network layer protocols are designed to account for the energy requirements of the alternative routes for each source-destination pair. Routing is accomplished using least-resistance routing (LRR) with a metric that includes a measure of the energy consumption.

An adaptive-transmission protocol for frequency-hop wireless communication networks

An energy-efficient adaptive-transmission protocol for mobile frequency-hop spread-spectrum wireless communication networks is described and evaluated. The purpose of the protocol is to permit each of the mobile terminals to adjust its transmitter power and code rate to match the characteristics of the time-varying communication links in the network. The proposed adaptive-transmission protocol bases its choice of transmission parameters on a very simple form of side information that is easy to obtain in a FH communication receiver. The performance of the adaptive-transmission protocol is evaluated for networks in which each communication link may have a time-varying propagation loss and intermittent partial-band interference. Our results demonstrate that the adaptive-transmission protocol can improve the utility of a link and reduce energy consumption by adjusting the transmission parameters in response to changes in the side information.

Adaptive transmission protocols for frequency-hop radio networks

The focus of this paper is on the performance of an adaptive transmission protocol for frequency-hop (FH) radio networks in which the radios can adjust the power in the transmitted signal and the rate of a Reed-Solomon code to respond to variations in partial-band interference and propagation loss. The adaptation is based on side information from the FH receiver and on information derived from the decoder. The results presented in this paper are obtained from a simulation of a wireless FH radio network in which the characteristics of the links are time-varying. These results demonstrate that the adaptive transmission protocol can improve the quality of a link by adapting to variations in both path-loss and interference to take advantage of favorable channel conditions.

Energy-efficient routing in frequency-hop networks with adaptive transmission

We describe and evaluate an energy-efficient protocol for routing traffic in frequency-hop (FH) store-and-forward packet radio networks that employ an adaptive transmission protocol. The adaptive transmission protocol allows the radios to adjust the power in the transmitted signal and the rate of a Reed-Solomon code to respond to variations in partial-band interference and propagation loss. Routing is accomplished using least-resistance routing (LRR) with a new metric that provides a quantitative assessment of the ability of a radio to receive and forward packets and includes a measure of the energy that is expected to be required for successful transmission. The new energy metric and LRR are integrated with the adaptive transmission protocol, and the performance of the new protocol suite is evaluated for a distributed FH network. The performance results presented in this paper are obtained from a simulation of wireless FH radio networks in which the characteristics of the links vary with time. The results demonstrate that in FH networks that employ an adaptive transmission protocol, the new method for routing can adapt quickly to changes in interference conditions. We find that LRR with the energy metric works with the adaptive transmission protocol to improve the information throughput and energy efficiency of the network.

Energy-efficient routing in frequency-hop radio networks with partial-band interference

The performance of an energy-efficient adaptive routing protocol is evaluated for a frequency-hop (FH) store-and-forward wireless network that must operate in the presence of partial-band interference. The routing protocol is based on least-resistance routing with a metric that accounts for link quality and energy consumption. The distributed routing protocol is integrated with the adaptive transmission and channel-access protocols. The performance of this protocol suite is demonstrated for a distributed FH network by use of a network simulation that includes multiple sources of partial-band interference. We find that the combination of energy-efficient routing and adaptive transmission improves the information throughput and energy efficiency of the network.

An improved forwarding protocol for updating channel state information in mobile FH wireless networks

The purpose of adaptive forwarding is to provide short-term responses to changes in propagation conditions and network topology in mobile store-and-forward wireless communication networks. The primary need for such short-term responses occurs during the time period between consecutive updates to the routing tables. In this paper a new adaptive-forwarding protocol is described and evaluated for frequency-hop (FH) mobile wireless networks. The forwarding protocol operates in conjunction with adaptive routing and adaptive transmission to provide energy-efficient delivery of packets. Channel state information, which is developed in the receivers of the terminals in the network, is used to estimate the energy requirements of alternative routes for use in the routing protocol. For FH networks the channel state information consists primarily of counts of errors and erasures that are generated in the demodulators and decoders. Since channel state information may become outdated, especially for infrequently used links, it is desirable to provide a mechanism for occasionally testing links that have not handled packets recently. A feature of the new adaptive-transmission protocol is that it employs information packets, rather than control packets, to update the channel state information and thereby benefit the routing protocol without adding overhead traffic to the network load.

Tradeoffs in the design of routing metrics for frequency-hop wireless networks

Throughput and energy consumption are two important performance measures for use in the evaluation of routing protocols for frequency-hop store-and-forward packet radio networks. As the radios adjust their transmission parameters to adapt to changes in propagation loss and interference, large differences may be created in the energy requirements of alternative routes available for routing. We previously demonstrated the advantages of incorporating an energy metric into least resistance routing to increase the energy efficiency of the routing protocol. In this paper new performance results are presented for an energy-efficient routing protocol, and the tradeoff between packet success probability and energy consumption is investigated.

Energy-efficient routing in multimedia ad hoc networks

A new protocol is presented for routing multimedia traffic in an energy-efficient manner in a frequency-hop, store-and-forward, packet radio network. The FH network employs an adaptive-transmission protocol integrated with a distributed, energy-aware routing protocol, based on least-resistance routing. Adaptive transmission gives rise to alternative paths through the network with different energy requirements. The adaptive routing and transmission protocols are designed to exploit the differences in the energy consumption of different routes and the service requirements of the different types of traffic. Results are provided that show that our energy-efficient routing protocol provides good service to the different types of media while conserving energy.

Route adaptation in response to changes in network activity in mobile frequency-hop networks

An adaptive routing protocol is defined and evaluated that uses a measure of the network activity in making routing decisions. The distributed routing protocol is designed to conserve energy when possible without increasing delay or decreasing packet success probability. It operates in a frequency-hop network in which mobile radios employ an adaptive-transmission protocol. Each radio monitors the amount of time that it is transmitting or receiving, and it uses this information to calculate an on-air ratio. This on-air ratio provides each radio with a measure of its activity level, which is used by a radio to determine when to adapt its routing protocol. When the network activity is low, a radio strives to employ low-energy links in forwarding packets. As the activity level increases, the routing protocol adapts by employing more high-quality routes in an effort to maintain low delay and high packet success rate. Our simulation results for mobile networks show that routing based on network activity levels provides energy savings when the opportunity exists, yet it achieves low delay and high packet success probability.

Energy-Efficient Routing for Frequency-Hop Wireless Networks

The use of adaptive-transmission protocols in wireless, store-and-forward, packet communication networks may result in large differences in the energy requirements of the alternative paths that are available to the routing protocol. Routing metrics can provide quantitative measures of the quality and energy efficiency of the paths from the source to the destination. Such measures are required if the routing protocol is to take advantage of the potential energy savings that are made possible by an adaptive-transmission protocol. An energy-efficient protocol suite for routing and adaptive transmission in frequency-hop wireless networks is described and evaluated, several routing metrics are compared, and tradeoffs among energy efficiency, delay, and packet success probability are investigated.