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Hybrid automata model systems with both digital and analog components, such as embedded control programs. Many veriication tasks for such programs can be expressed as reachability problems for hybrid automata. By improving on previous decidability and undecidability results, we identify a boundary between decidability and undecidability for the reachability… (More)

In this paper, we present an algorithm for routing in wireless ad hoc networks using information about geographical location of the nodes. We assume each node knows its geographical position and the position of the node to which it wants to send a packet. Initially, the nodes only know their neighbors but over time they discover other nodes in the network.… (More)

A hybrid system models both discrete event and continuous dynamics. We present a modeling formalism and a veriication methodology for hybrid systems. The veriication methodology is based on abstracting the continuous dynamics in the hybrid system by simpler continuous dynamics. We present two methods for doing this: in the rst method, a diierential… (More)

In IEEE 802.11 wireless LANs, the DCF access method and the PCF access method operate alternatively within a superframe to service the time-varying traffic demands. Due to different medium access mechanisms deployed by DCF and PCF, they work well for some particular types of traffic scenarios respectively, while their performance may degrade under some… (More)

Proof: 2 L(H D) (2 L(H C)) provided there is a sequence =< D(l 0); 0 ; 0 >< D(l 1); 1 ; 1 > : : : which is discrete-time (continuous-time) consistent. As discussed at beginning of Sect. 3, every discrete-time consistent sequence is continuous-time consistent. From Lemma 3-Lemma 7, every continuous-time consistent sequence is also discrete-time consistent.… (More)

We consider the problem of storing a set S k as a deterministic nite automaton (DFA). We s h o w that inserting a new string 2 k or deleting a string from the set S represented as a minimized DFA can be done in expected time O(kjj), while preserving the minimality of the DFA. We then discuss an application of this work to reduce the memory requirements of a… (More)

— We consider a packet switched wireless network in which a base station serves the mobiles. The packets for the mobiles arrive at the base station and have to be scheduled for transmission to the mobiles. The capacity of the channel from the base station to the mobiles is varying with time due to fading. We assume the mobiles can obtain different types of… (More)