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The enormous increase in wireless enabled devices has posed a great challenge for effective resource sharing in Wi-Fi networks. This challenge has triggered the re-evaluation of wireless resource sharing protocols. Available frequency spectrum is probably the most valuable network resource. Therefore, effective utilization of this scarce resource is highly desired. The traditional channelization of...
In this paper, an energy efficient adaptive modulation scheme is proposed for a wireless cognitive radio ad hoc network, where each node is equipped with cognitive radio and the network is an OFDMA system operating on time slots. In each slot, the users with new traffic demand will sense the spectrum and locate the available subcarrier set. Then they choose subcarriers with favorable channel condition...
We propose a novel distributed cross-layer optimization approach for cognitive radio wireless networks. A cognitive radio is a wireless device that is capable of sensing the prevailing environmental conditions and automatically adapting its operating parameters in order to enhance the performance of both the system and potentially the whole network. Given the lack of a centralized intelligence to...
In this paper, we propose a cross-layer optimization approach that exploits retransmission diversity in wireless CDMA communications. Conventionally, data packets that are not correctly detected are usually dropped. These dropped packets can be used to help data packet detection. By exploiting all the retransmitted packets, data packets can be correctly detected with higher probability. The proposed...
Wireless sensor networks consist of a large number sensors spread across a given geographical area. Each sensor has its own communication capability as well as certain level of intelligence for signal processing and networking. As the sensor nodes are densely populated, communication range requirement for these nodes is smaller. After signal detection, a number of sensor nodes communicate over the...
A high intercept points, cost-effective, and power-efficient switching FET double balanced mixer (DBM) is reported. The Switching FET DBM demonstrated in this work offers input intercept points (IIP3) and conversion loss typically 44 dBm and 8.5 dB respectively with 15 dBm LO power for the frequency band (RF: 900-2150 MHz, LO: 850-1950 MHz, IF: 50-200 MHz). The measured interport isolation is typically...
Correlative minimum shift keying (MSK), a second order polynomial modulation scheme known as tamed frequency modulation (TFM), is a constant envelope type of modulation with a perfect peak to average power ratio (PAPR), besides the property of low out of band power. We apply the linearized TFM to the single carrier transmission with frequency domain equalization (SC/FDE) concept. We then obtain a...
In this paper, we propose a cognitive radio-based multi-user resource allocation framework for mobile ad hoc networks using multi-carrier DS CDMA modulation over a frequency-selective fading channel. In particular, given pre-existing communications in the spectrum where the system is operating, in addition to potential narrow-band interference, a channel sensing and estimation mechanism is provided...
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