Enhancing the efficacy and security of emerging wireless systems:

In this thesis, we intend to promote the efficacy and tackle the vulnerabilities in three emerging wireless systems that have recently became popular examples of emerging wireless systems, namely location-based systems, RFID systems, and cognitive radio systems. In location-based systems, we first address the problem of being able to reliably deliver content to users based on their locations, in spite of the limited resources available in a wireless network. Secondly, allocating content based on a claimed location implies that location information should be verified in order to support these new location-based services. We examine strategies whereby access points in an infrastructure delegate the responsibility to serve users to other users who have cached requested content. The resulting strategy, which we call Deputy&Forward, uses knowledge of the user mobility pattern to optimize content delivery for location-based services. Additionally, to verify location information, we adapt the classical challenge-response method for authentication to the task of verifying an entity's location. Our scheme utilizes a collection of transmitters, and adapts the power allocations across these transmitters to verify a user's claimed location. This strategy, which we call power-modulated challenge response, is able to be used with existing wireless networks. As for the RFID systems, we propose a new RFID network prototype that uses transmit-only low-cost tags and lays the burden of the detection and discrimination of collided tag signals on the RFID readers. We present a statistical estimation approach that can perform the detection in the existence of collisions and the near-far problem. Further, we present a low detection error through simulations under realistic system conditions. Lastly, in cognitive radio systems, we focus on the security problem whereby a cognitive radio node inserts too many packets into the network, thereby disregarding the link quality, the transaction parties' processing speed and other nodes' transmission attempts. An onboard regulative approach is presented to locally enforce the spectrum etiquettes based on the associated link qualities. We evaluate the performance of our scheme with GNU radios in the ORBIT testbed, and show that better transmission efficiency is achieved.Ph.D.Includes bibliographical references (p. 120-126)by Yu Zhan