Juite Hwu

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— The use of signal processing techniques to protect wireless transmissions is proposed as a way to secure wireless networks at the physical layer. This approach addresses a unique weakness of wireless networks whereby network traffic traverses a public wireless medium making traditional boundary controls ineffective. Specifically, a randomized array(More)
Cognitive radio is a desirable technique for secondary users to utilize the spectrum gray space. In order to avoid intolerable interference to primary users, the transmission power of cognitive radios must be carefully managed. In this paper, we analyze the sum transmission power of a group of randomly distributed but fully cooperated secondary transmitters(More)
One of the major challenges to cognitive radios is the synchronization of distributed radios onto the same spectrum white spaces which vary in time and space. In this paper, we propose a frequency-hopping spread spectrum transmission scheme which works reliably without any a priori handshaking assumption. Each cognitive radio independently detects white(More)
In contrast to the classical spread spectrum or data encryp-tion methods, we propose an array redundancy-based approach for wireless transmissions with inherent low probability of interception (LPI). The redundancy of transmit antenna arrays introduces some degrees of freedom for deliberate signal randomiza-tion, based on which, diversity is exploited to(More)
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