Development in short range wireless LAN (WLAN) and long range wireless WAN (WWAN) technologies have motivated recent efforts to integrate the two. This creates new application scenarios that were not possible before. Vehicles with only WLAN radios can use other vehicles that have both WLAN and WWAN radios as mobile gateways and connect to the Internet while on the road. The most difficult challenge in the scenario is to deal with frequent route breakages due to dynamic mobility of vehicles on the road. Existing routing protocols which are widely used for mobile ad hoc networks are reactive in nature and wait till existing routes break before constructing new routes. The frequent route failures result in significant amount of time needed for repairing existing routes or reconstructing new routes. In spite of the dynamic mobility, the motion of vehicles on highways is quite predictable compared to other mobility patterns for wireless ad hoc networks, with location and velocity information readily available. This can be exploited to predict how long a route will last between a vehicle requiring Internet connectivity and the gateway which provides a route to the Internet. Successful prediction of route lifetimes can significantly reduce the number of route failures. In this paper we introduce a prediction based routing (PBR) protocol that is specifically tailored to the mobile gateway scenario and takes advantage of the predictable mobility pattern of vehicles on highways. The protocol uses predicted route lifetimes to preemptively create new routes before existing ones fail. We study the performance of this protocol through simulation and demonstrate significant reductions in route failures compared to protocols that do not use pre-emptive routing. Moreover, we find that the overhead of pre-emptive routing is kept in check due to the ability of PBR to predict route lifetimes.

Abstract-Energy consumption of portable RFID readers is becoming an important issue as applications of RFID systems pervade many aspects of our lives. Surprisingly, however, these systems are not energy-aware with the focus till date being on reducing the time to read all tags by the reader. In this work, we consider the problem of tag arbitration in RFID systems with the aim of designing energy aware anti-collision protocols. We explore the effectiveness of using multiple time slots per node of a binary search tree through three anti-collision protocols. We further develop an analytical framework to predict the performance of our protocols and enable protocol parameter selection. We demonstrate that all three protocols provide significant energy savings both at the reader and tags (if they are active tags) compared to the existing Query Tree protocol, while sharing the deterministic property of the latter. Further, we show that our protocols provide similar benefits even with correlated tag IDs.

Development in Wireless LAN and Cellular technologies has motivated recent efforts to integrate the two. This creates new application scenarios that were not possible before. Vehicles with Wireless LAN radios can use other vehicles with both Wireless LAN and Cellular radios as mobile gateways and connect to the outside world. We aim to study the feasibility of such global connectivity from the road through simulation of the underlying connectivity characteristics for varying traffic and gateway densities. The connectivity results suggest that each vehicle should be able to connect to at least one gateway for a majority of time. The average path lifetimes are found to be good enough many traditional Internet applications like FTP and HTTP. The effectiveness of the AODV wireless ad-hoc routing protocol over this scenario is evaluated and shown to perform well for the densities considered. However, the routes created by AODV can break very frequently due to the dynamic nature of mobility involved. We introduce a couple of prediction based routing protocols to minimize these route breakages and thus improve performance. These protocols take advantage of some deterministic characteristics of the mobility model to better predict route breakages and take preemptive action.

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There are currently few options for navigational aids for the blind and visually impaired (BVI) in large indoor spaces. Such indoor spaces can be difficult to navigate even for the general sighted population if they are disoriented due to unfamiliarity or other reasons. This research study presents an indoor wayfinding system called GuideBeacon for the blind, visually impaired, and disoriented (BVID) that assists people in navigating between any two points within indoor environments. It describes the technical challenges faced in designing such a system, the design decisions made in building the current version of the GuideBeacon system, the solutions developed to meet the technical challenges, and results from the evaluation of the system. Results presented in this research study obtained from field testing GuideBeacon with BVI and sighted participants suggests that it can be used by the BVID for navigation in large indoor spaces independently and effectively.