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IEEE 802.11 based wireless networks have seen rapid growth and deployment in the recent years. Critical to the 802.11 MAC operation, is the <i>handoff</i> function which occurs when a mobile node moves its <i>association</i> from one <i>access point</i> to another. In this paper, we present an empirical study of this handoff process at the link layer, with(More)
The explosive growth in wireless networks over the last few years resembles the rapid growth of the Internet within the last decade. During the beginning of the commercialization of the Internet, organizations and individuals connected without concern for the security of their system or network. Over time, it became apparent that some form of security was(More)
Many wireless channels in different technologies are known to have partial overlap. However, due to the interference effects among such partially overlapped channels, their simultaneous use has typically been avoided. In this paper, we present a first attempt to model partial overlap between channels in a systematic manner. Through the model, we illustrate(More)
We propose techniques to improve the usage of wireless spectrum in the context of wireless local area networks (WLANs) using new channel assignment methods among interfering Access Points (APs). We identify new ways of channel re-use that are based on realistic interference scenarios in WLAN environments. We formulate a weighted variant of the graph(More)
The 802.11 IEEE Standard has enabled low cost and effective wireless LAN services (WLAN). With the sales and deployment of WLAN based networks exploding, many people believe that they will become the fourth generation cellular system (4G) or a major portion of it. However, the small cell size of WLAN creates frequent hand-offs for mobile users. If the(More)
Node compromise poses severe security threats in wireless sensor networks. Unfortunately, existing security designs can address only a small, fixed threshold number of compromised nodes; the security protection completely breaks down when the threshold is exceeded. In this paper, we seek to overcome the threshold limitation and achieve resiliency against an(More)
In a computer system, the integrity o f l o wer layers is treated as axiomatic by h i g h e r l a yers. Under the presumption that the hardware comprising the machine (the lowest layer) is valid, integrity o f a l a yer can be guaranteed if and only if: (1) t h e i n tegrity o f t h e lower layers is checked, and (2) transitions to higher layers occur only(More)
Copilot is a coprocessor-based kernel integrity monitor for commodity systems. Copilot is designed to detect malicious modifications to a host's kernel and has correctly detected the presence of 12 real-world rootkits, each within 30 seconds of their installation with less than a 1% penalty to the host's performance. Copilot requires no modifications to the(More)
Ad-hoc networks — and in particular wireless mobile ad-hoc networks — have unique characteristics and constraints that make traditional cryptographic mechanisms and assumptions inappropriate. In particular, it may not be warranted to assume pre-existing shared secrets between members of the network or the presence of a common PKI. Thus, the issue of key(More)
— We propose an efficient client-based approach for channel management (channel assignment and load balancing) in 802.11-based WLANs that lead to better usage of the wireless spectrum. This approach is based on a " conflict set coloring " formulation that jointly performs load balancing along with channel assignment. Such a formulation has a number of(More)