2011/4

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    A High Accurate and Low Bias SNR Estimator: Algorithm and Implementation
    (Společnost pro radioelektronické inženýrství, 2011-12) Gong, Chao; Zhang, Bangning; Liu, Aijun; Guo, Daoxing
    Signal to noise ratio (SNR) estimators are required for many radio engineering applications. In this paper, a SNR estimator based on the first and second order moments is derived and examined for constant envelop modulations over additive white Gaussian noise (AWGN) channel. In the first, a modification method is proposed to reduce the bias of conventional first and second order moments based SNR estimator. Then, in order to reduce hardware implementation complicity, multi segments of cubic polynomial are adopted to approximate the expression of the proposed SNR estimator which doesn’t have a close form solution. The approximate expression is very precise in the SNR range -10dB ~ 20 dB as illustrated by numerical simulation. Besides, practical hardware circuit is proposed for FPGA implementation. Simulation results show that the proposed SNR estimator has the lowest normalized bias and variance when compared with two other classic estimators.
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    Efficient Algorithm for Power Allocation in Relay-based Cognitive Radio Network
    (Společnost pro radioelektronické inženýrství, 2011-12) Ferdous, N.; Ahmed, M.; Matin, M. A.; Habiba, U.
    This paper addresses a cognitive radio (CR) network scenario where a relay is assigned to mitigate interference to primary users (PUs). We develop an average probability of successful secondary transmission (PSST) to introduce relay in the CR network. The power allocation is done using dual domain concept to maximize the system throughput as well as maintaining interference to an acceptable level and this approach is implemented in our paper that has a higher convergence rate. Furthermore, we propose an alternative approach that maintains a high throughput and at the same time reduces the computational complexity significantly. A detailed analysis is done before simulation. The simulated results validate the theoretical analysis.
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    Analysis and Simulation of the Transmission Distortions of the Mobile Digital Television DVB-SH Part 1: Terrestrial Mode DVB-SH-A with OFDM
    (Společnost pro radioelektronické inženýrství, 2011-12) Polak, Ladislav; Kratochvil, Tomas
    This paper deals with the latest digital TV standard DVB-SH (Digital Video Broadcasting - Satellite to Handhelds) with focus on utilization of its advantages for the next generation of mobile TV broadcasting. The whole paper consists of two parts. In this first part, after the brief introduction to DVB-SH and related last works review, the simulation model of DVB-SH-A, which is using terrestrial configuration with OFDM transmission mode, is presented. The work is especially focused on the description of new type of forward error correction and system configuration of the DVB-SH-A mode. For the analysis and simulation of the transmission, the original scheme of turbo encoder was modified in this paper. Application for simulation of the transmission in mobile and portable fading transmission channels was developed in MATLAB. Dependences of BER on C/N ratio for all types of payload modulation are compared with focus on mobile TV services availability. Finally, the achieved results are evaluated and clearly discussed.
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    Realization of Resistorless Wave Active Filter using Differential Voltage Current Controlled Conveyor Transconductance Amplifier
    (Společnost pro radioelektronické inženýrství, 2011-12) Pandey, Neeta; Kumar, Praveen
    In this paper, a resistorless realization of high order voltage mode wave active filter based on Differential Voltage current controlled conveyor transconductance amplifier (DVCCCTA) is presented. The wave method is used for simulating reflected and incident wave for basic building block i.e. series inductor and configuring it for other passive element realization by making appropriate connection. The proposed structure uses grounded capacitors and possesses electronic tunability of cutoff frequency. The proposed approach is verified for a 4th order low pass filter through SPICE simulation using 0.25µm TSMC CMOS technology parameters.
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    Energy Analysis of Received Signal Strength Localization in Wireless Sensor Networks
    (Společnost pro radioelektronické inženýrství, 2011-12) Moravek, Patrik; Komosny, Dan; Simek, Milan; Girbau, David; Lazaro, Antonio
    This paper presents the investigation of energy demands during localization of wireless nodes in ad-hoc networks. We focus on the method based on the received signal strength (RSS) to estimate the distances between the nodes. To deal with the uncertainty of this technique, statistical methods are used. It implies more measurement samples to be taken and consequently more energy to be spent. Therefore, we investigate the accuracy of localization and the consumed energy in the relation to the number of measurement samples. The experimental measurements were conducted with IRIS sensor motes and their results related to the proposed energy model. The results show that the expended energy is not related linearly to the localization error. First, improvement of the accuracy rises fast with more measurement samples. Then, adding more samples, the accuracy increase is moderate, which means that the marginal energy cost of the additional improvement is higher.