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The energy consumption driven by dramatic growing demand for mobile data rates has attracted extensive attention. It is expected that the next generation cellular communication systems should improve not only spectral efficiency but also energy efficiency. Coordinated multi-point transmission (CoMP) and heterogeneous networks (HetNets) are two techniques for achieving high spectral efficiency and...
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...
In this paper the performance of the ESPAR (electronically steerable passive array radiator) antenna in suppressing both the co-channel and inter-symbol interferences is compared with the conventional circular and linear arrays. For this purpose, the STAP (space-time adaptive processing) is implemented in both arrays with equal elements. Simulation results show that when the pattern of the ESPAR antenna...
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...
In this paper, we address the issue of transmission power control (TPC) in wireless ad hoc networks. Power control plays an important role in energy saving and network performance enhancement. However, the existing TPC schemes either face the problem of hidden and exposed terminal or have additional hardware requirements. We propose a novel distributed power control protocol, called Receiver Initiated...
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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