We examine the performance of a random-walk search algorithm for wireless sensor networks when resources are subject to limited lifetimes and queries are constrained by application-specific deadlines. Specifically, via the time-to-live and transmission range parameters, we estimate the appropriate number of resource copies that must be created within the network to minimize the total node arrival rate (the energy-centric approach) or to ensure the total proportion of queries failures does not exceed a specified threshold (the failure-centric approach). The effect of node transmission range on network performance is also investigated. We compare the results of our network simulations to our queueing-based analytic node model and find that there is an inverse relationship between transmission range and the time-to-live value required to minimize the total node arrival rate.

We develop a queueing model for analyzing resource replication strategies in wireless sensor networks. The model can be used to minimize either the total transmission rate of the network (an energy-centric approach) or to ensure the proportion of query failures does not exceed a predetermined threshold (a failure-centric approach). The model explicitly considers the limited availability of network resources, as well as the frequency of resource requests and query deadlines, to determine the optimal replication strategy for a network resource. While insufficient resource replication increases query failures and transmission rates, replication levels beyond the optimum result in only marginal decreases in the proportion of query failures at a cost of higher total energy expenditure and network traffic.

We present a small-footprint search protocol designed to facilitate any-type queries for data content and services in large population, high-density wireless sensor networks. Our protocol, termed Trajectory-based Selective Broadcast Query (TSBQ), works in conjunction with time division multiple access- or schedule-based medium access control protocols to reduce per-query energy expenditure. We compare the performance of TSBQ to unicast- and local broadcast-based search algorithms and also determine a critical node density based on the energy expended by nodes to transmit and receive. Minimal energy expenditure is achieved by determining the optimal number of data/service replicates and the number of nodes designated to receive each query transmission. Numerical results indicate that TSBQ significantly reduces the total energy expenditure of a network as compared to unicast and local broadcast-based search protocols.

Wireless sensor network (WSN) design is complicated by the interaction of three elements: localization, medium access control, and routing. The design of wireless sensor networks necessarily focuses on the network's intended purpose as well as an understanding of the synergies and tradeoffs between each of these three elements. We propose five guidelines for the development of a wireless sensor network, and the performance and suitability of several protocols and algorithms are examined with respect to those guidelines. We also suggest several performance metrics to provide fair comparisons between various localization, medium access control, and routing protocols.

The Intermodal Surface Transportation Efficiency Act of 1991 (ISTEA) requires that projects identified in a region's long range plan be financially constrained. As a metropolitan planning organization, the Southeast Michigan Council of Governments (SEMCOG) developed a plan that not only met the ISTEA requirements and served the needs of its member communities, but that also was consistent and comparable with forecasts developed by the state's other urban areas and with the state plan developed by the Michigan Department of Transportation. This paper describes the method, development of assumptions and databases and the validation of the forecast with local and state transportation agencies. SEMCOG focused on identifying and matching resources to meet the region's capital needs, which involved roadway, transit, non-motorized and intermodal projects. Future revenues were used to constrain the projects, with unmet needs being defined as the shortfall of financial resources necessary to meet all needs identified in the deficiency analysis stage. In a survey that identified revenue resources, revenues were anticipated as being available from federal, state and local sources.

The Intermodal Surface Transportation Efficiency Act of 1991 requires that projects identified in a region's long range plan be financially constrained. As an MPO, SEMCOG, the Southeast Michi- gan Council of Governments, developed a plan that not only met the ISTEA requirements and served the needs of its member communities, but that also was consistent and comparable with forecasts developed by the state's other urban areas and with the state plan developed by MDOT, the Michigan Department of Transportation. This paper will describe the method, development of assumptions and databases and the validation of the forecast with local and state transportation agencies. SEMCOG focused on identifying and matching resources to meet the region's capital needs, which involved roadway, transit, non-motorized and intermodal projects. Future revenues were used to constrain the projects in the RTP, with unmet needs being defined as the shortfall of financial resources necessary to meet all needs identified in the deficiency analysis stage. In a sur- vey that identified revenues resources, revenues were anticipated as being "available" from fed- eral, state and local sources. The forecast of federal funds focused on those available to local units of government in Southeast Michigan with the Michigan Department of Transportation being responsible for forecasting funds for state trunkline projects within the region. Historical data from pre-ISTEA years was identified and, with some manipulation of the data, made compatible with the federal-aid programs created by ISTEA in order to identify a trend in revenues. Each year, the transit agencies, county road commissions, cities, villages and state department of transportation share state fuel taxes and vehicle registration fees credited to the Michigan Trans- portation Fund (MTF). Distribution reports have been provided each year in compliance with the state's "Act 51" requirements. SEMCOG developed an internal database to capture the financial information delineated in this annual report. It was decided that a simple regression of 25 year's information could provide a reasonable projection of future anticipated revenues from this source. Ascertaining revenues derived from local non-user sources proved to be quite challenging. In addi- tion to its federal and state revenue receipts, each local unit of government (i.e. county road com- missions, cities, villages) has the ability to generate or assign its own revenues for transportation purposes. With well over 100 units of local government, there was a need to identify a single, uni- form and reasonably comparable source of data. It was determined that the best source of informa- tion was contained in "Act 51" computerized databases. These annual databases were compiled by MDOT, based upon audited reports submitted by each local unit of government, in compliance with state Act 51 reporting requirements. There were several barriers in performing a capital-only forecast. While federal revenues must be earmarked for capital projects, in general, the assignment of MTF and local revenues to capital projects are not as apparent. As such, it was necessary to develop a factor to approximate capital/ operating expense portions of total expenses. Once again, the best source of information appeared to be the Act 51 reports. It was necessary to validate the information with the individual county road commissions, since it was the information that they had reported that was being captured.