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This study develops an enhanced transportation planning framework by augmenting the sequential four-step planning process with post-processing techniques. The post-processing techniques are incorporated through a feedback mechanism and aim to improve the stability and convergence properties of the solution, thereby improving the reliability of the planning process. There are three building blocks of the proposed post-processing module: slope-based multi-path algorithm or SMPA, perturbation assignment, and O-D prioritization technique. SMPA is the most important part of the module and it can be used as both a post-processing algorithm and an independent static traffic assignment algorithm. In addition to SMPA, the post-processing module consists of perturbation assignment and O-D prioritization schemes. Perturbation assignment provides warm start and the O-D prioritization improves the rate of convergence by deciding the sequence in which the O-D pairs are brought into the flow update process. A detailed implementation procedure for perturbation assignment is developed along with six different criteria for O-D prioritization. Computational experiments using the Sioux Falls, Anaheim and Borman Corridor networks provide insights on these techniques. Results of the computational experiments show that SMPA has a superior rate of convergence compared to state-of-the-practice algorithms even without O-D prioritization and warm start. Results of computational experiments further reveal that a warm start using perturbation assignment and O-D prioritization provides significant benefits in improving the convergence properties and obtaining a more stable solution.

This study addresses the problem of dynamic routing operations in the emergency response context, primarily in terms of the routing of response vehicles and evacuees. The study focuses on identifying the paths used for routing response vehicles and the evacuees in disaster situations. In this context, two application modules are developed: module for K-shortest paths routing and module for multiple-stop routing. The K-shortest paths module allows more flexible options for routing response vehicles under the dynamic network conditions due to a disaster. It provides multiple routes for evacuation and response operations. The multiple-stop routing module enables the delivery of relief resources to several locations using a single response vehicle. It has the ability to impose time window constraints for relief operations and the reordering of the routing to the delivery locations, capabilities which are critical to disaster operations. For ease of operability, these modules are developed on a Geographic Information System (GIS) platform used by the Indiana Department of Transportation (INDOT) and Indiana Department of Homeland Security (IDHS). Based on dynamic field conditions, color-coded flags on the GIS map are used to characterize links in terms of their availability and functionality in the context of the response operations. These link characteristics are dynamically updated as new information on the network conditions becomes available over time. The proposed modules can be integrated into the current web-based traffic information system called TrafficWise supported by INDOT and disaster management system Web Emergency Operation Center (WebEOC) supported by IDHS for seamless practical implementation.

Network-coded cooperative communications (NCCC) is a new paradigm in wireless networks that employs network coding (NC) to improve the performance of CC. The core mechanism to harness the benefits of NC-CC is to appropriately combine sessions into separate groups, and then have each group select the most beneficial relay node for NC-CC. In this paper we study this joint grouping and relay node selection problem for NC-CC. Due to NP-hardness of problem, we propose a distributed and online algorithm that offers near-optimal solution to this problem. The key idea in our algorithm is to have each neighboring relay node of a new session determine and offer its best local group; and then to have the source node of the new session select the best group among all offers. We show that our distributed algorithm has polynomial complexity. Using extensive numerical results, we show that our distributed algorithm adapts well to online network dynamics., Published in the IEEE INFOCOM Proceedings held in Shanghai, China on 10-15 April 2011.

Recently, cooperative communications, in the form of having each node equipped with a single antenna and exploit spatial diversity via some relay node's antenna, is shown to be a promising approach to increase data rates in wireless networks. Under this communication paradigm, the choice of a relay node (among a set of available relay nodes) is critical in the overall network performance. In this paper, we study the relay node assignment problem in a cooperative ad hoc network environment, where multiple source-destination pairs compete for the same pool of relay nodes in the network. Our objective is to assign the available relay nodes to different source-destination pairs so as to maximize the minimum data rate among all pairs. The main contribution of this paper is the development of an optimal polynomial time algorithm, called ORA, that achieves this objective. A novel idea in this algorithm is a ?linear marking? mechanism, which maintains linear complexity of each iteration. We give a formal proof of optimality for ORA and use numerical results to demonstrate its capability., The original document contains color images.

In this paper, we present an analytical model that characterizes TCP NewReno's goodput as a function of round-trip time, average time duration between handoffs, average number of packets reordered during a handoff, and the congestion window threshold. In cellular networks, the effective packet-loss probability for a flow experiencing handoffs is not exactly equal to the physical-layer packet-loss probability; it also depends on the frequency of handoffs and the number of packets that may arrive out of order at the receiver due to handoffs. With the emergence of technologies such as WiMax and Ultra Mobile Broadband (UMB), understanding the effect of handoffs and packet reordering on the goodput of TCP becomes very important for the designers of next generation cellular networks. Existing TCP throughput models cannot be used to understand the precise effect of handoffs and the resultant packed reordering on TCP's goodput. In this paper, we present a model of TCP NewReno goodput that captures the effect of handoffs. We validate the model by performing actual file transfers between different hosts that are connected by a router which emulates the wireless environment with handoff events and packet reordering.