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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 work, the bulk-gate controlled circuit to improve the power supply ripple ratio (PSRR) of a Low Dropout Regulator (LDO) which deteriorates due to lowering power consumption is proposed. Designing with 0.25 mum CMOS process, the simulation results by HSPICE shown that the proposed circuit provides a high performance of PSRR even though 1/10 of the power consumption is reduced compare to the...
A delay-locked loop of multi-band selector with wide-locking range and low power dissipation is presented. The architecture of the proposed delay-locked loop consists of phase frequency detector, charge pump, band selector, multi-control delay line, and start-up circuit. The multi-band selector is used to extend operation frequency of delay-locked loop by switching the multi-control delay line. The...
This paper describes a comparative analysis between two topologies of operational amplifiers to design a 40 MS/s 12-bit pipeline analog to digital converter (ADC). The analysis includes AC and transient simulation to select the proper topology. This ADC is implemented in a 0.35 mum AMS CMOS technology with 3.3 V single power supply. The capacitors and selected operational amplifiers were scaled for...
In this paper, a 12-bit 50MHz Pipelined Low-Voltage ADC is presented, which consists of 8-stage-pipelined low resolution ADCs and a 4-bit flash ADC. Several critical technologies are used to guarantee the resolution and high sampling and converting rate such as 1.5bits per stage conversion, digital correction logic, gain-boosted telescopic OTA and so on. Finally the whole system is taped out in SMIC...
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...
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...
Sink mobility has become an increasingly important requirement of various sensor network applications. Handling such mobile sink conditions brings new challenges to large-scale sensor networking. This investigation proposed a hybrid-structure routing protocol (HSRP) that combines the benefits of grid-based and cluster-based structures. Grid-based structure is designed to solve the cluster head selection...
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