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We study the running time of distributed algorithms deployed in a widely distributed setting over the Internet using TCP. We consider a simple primitive that corresponds to a <i>communication round</i> in which every host sends information to every other host; this primitive occurs in numerous distributed algorithms. We experiment with four algorithms that(More)
BACKGROUND Conventional programmed ventricular stimulation protocols are inefficient compared with more recently proposed protocols. The purpose of the present study was to determine if additional efficiency could be derived from a 6-step programmed ventricular stimulation protocol that exclusively uses four extrastimuli. METHODS AND RESULTS The subjects(More)
— This paper presents a practical method for using multi-antenna radios to cancel interference in cognitive radio systems. Under this method, secondary radio transmitters use beamforming techniques to find antenna weights that place nulls at the primary receivers, and secondary radio receivers use adaptive techniques to decode in the presence of(More)
We consider the problem of secure wireless communication in the presence of an eavesdropper when the transmitter has multiple antennas, using a variation of the recently proposed artificial noise technique. Under this technique, the transmitter sends a pseudo-noise jamming signal to selectively degrade the link to the eavesdropper without affecting the(More)
Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to(More)
Although mobile phone usage has proliferated in urban areas of developing countries, many rural or poor users remain completely unconnected, particularly in Africa. In this paper, we advocate an alternative " voice message mostly " mobile phone architecture to reach the next billion users. Using initial analyses of mobile phone usage and rural power data,(More)
This paper proposes a new framework for spectrum reuse. Existing architectures have centered on secondary users (cognitive radios) that can reliably sense primary users and opportunistically transmit, without directly interacting with the primary system. We present a paradigm in which the primary and secondary systems cooperate, to minimize interference to(More)
Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to(More)
Multi-element antennas offer the possibility of increasing the spatial reuse of wireless spectrum by &#x201C;nulling&#x201D; out interfering signals. However, the interference suppression performance is highly sensitive to small errors in the gains applied to the antenna elements. In this paper, we examine in detail the effect of one specific source of(More)
Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to(More)