This paper proposes a new Matlab-developed algorithm for automatic recognition of digital modulations using the constellation of states. Using this technique the automatic distinction between four digital modulation schemes (8-QAM, 16-QAM, 32-QAM and 64-QAM) was made. It has been seen that the efficiency of the algorithm is influenced by the type of modulation, the value of the signal-to-noise ratio and the number of samples. In the case of an AWGN noise channel the simulation results indicated that the value of SNR (signal-to-noise ratio) has a small influence on the recognition rate for lower-order QAM (8-QAM and 16-QAM). The length of the signal may change essentially the recognition rate of this algorithm especially for modulations with a high number of bits per symbol. Consequently, for the 64-QAM modulation in a case of 25dB signal-to-noise ratio the recognition rate is doubled if the sample rate is incresed from 5400 to 80640.
This article deals with developing new modified algorithms of 40kb/s ADPCM. Beside the standard algorithm, three algorithms are developed to reduce the ADPCM distortion. The performances of all algorithms are evaluated with QAM signal at speed of 9.6kb/s. The outcomes demonstrate that the first proposed algorithm outperforms the other algorithms.
This paper presents new modified QAM modem that operates at data rate of 14.4kb/s to be transmitted over 32kb/s Adaptive Differential Pulse Code Modulation (ADPCM). The purpose of this modified QAM modem is to reduce the nonlinear distortion introduced by ADPCM. The performance of ADPCM is studied considering the standard QAM modem and modified QAM modem with different constellations. The simulation results show that the performance of ADPCM with modified QAM modem is better than its performance with standard QAM modem. Also, the performance with circular constellation is better than rectangular one.
The power-line communication (PLC) technique involves sending information through an electrical conductor for a commercial or domestic purpose. Lately, electronic means of communication have gained popularity for the transfer of information. Conversely, there is an increased requirement for more transmission media, like the use of power line as a communication channel for remote data delivery. This paper focuses on determining the data rate profile achievable using the single-carrier/multicarrier modulation techniques with Reed- Solomon concatenated convolutional (RS-CC) codes for data transmission through a power line channel. In this investigation, MATLAB/SIMULINK was used to explore a low-voltage power line as a communication channel for high data transmission rate. Data transmission was accomplished by utilizing a parametric model of a power line channel with the different kinds of noise considered in the simulation. In the designed power-line communication (PLC) system, single-carrier modulation offered a maximum of 14.4 Mbps reduction in the data rate when the uncoded 64-quadrature amplitude modulation (QAM) was compared to coded 64-QAM with 1/2 forward error correction (FEC). In the OFDM power-line communication (PLC) system, the decrease in the data rate was maximal at 39 Mbps when the uncoded 16-QAM was contrasted with the 16-QAM having 1/2 FEC. It was evident that the increased code rate of the PLC system using single-carrier and OFDM modulation implied increased data rate profiles
Oleg Chernoyarov, Alexey Glushkov, Vladimir Litvinenko, Yuliya Litvinenko and Boris Matveev
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