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Pilot Based MMSE Channel Estimation for Spatial Modulated OFDM Systems

Soman Anetha Mary, Nakkeeran R., Shinu Mathew John

International Journal of Electronics and Telecommunications

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2021

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Vol. 67, No. 4

685--691

EN

Due to the multifold growth in demands of multimedia services and mobile data, the request for increased channel capacity in mobile and wireless communication has been quickly increasing. Developing a wireless system with more spectral efficiency under varying channel condition is a key challenge to provide more bit rates with limited spectrum. Multiple Input Multiple Output(MIMO) system with Orthogonal Frequency Division Multiplexing (OFDM) gives higher gain by using the direct and the reflected signals, thus facilitating the transmission at high data rate. An integration of Spatial Modulation (SM) with OFDM (SM OFDM) is a newly evolved transmission technique and has been suggested as a replacement for MIMO -OFDM transmission. In practical scenarios, channel estimation is significant for detecting transmitted data coherently. This paper proposes pilot based, Minimum Mean Square Error (MMSE) channel estimation for the SM OFDM communication system. We have focused on analyzing Symbol Error Rate (SER) and Mean Square error (MSE) under Rayleigh channel employing International Telecommunication Union (ITU) specified Vehicular model of Pilot based MMSE channel estimator using windowed Discrete Fourier Transform (DFT) and MMSE weighting function. Simulation output shows that proposed estimator’s SER performance lies close to that of the MMSE optimal estimator in minimizing aliasing error and suppressing channel noise by using frequency domain data windowing and time domain weighting function. Usage of the Hanning window eliminates error floor and has a compact side lobe level compared to Hamming window and Rectangular window. Hanning window has a larger MSE at low Signal to Noise Ratio (SNR) values and decreases with high SNR values. It is concluded that data windowing technique can minimize the side lobe level and accordingly minimize channel estimation error when interpolation is done. MMSE weighting suppresses channel noise and improves estimation performance. Since Inverse Discrete Fourier Transform(IDFT)/DFT transforms can be implemented with fast algorithms Inverse Fast Fourier Transform( IFFT)/Fast Fourier Transform(FFT) computational complexity can be remarkably reduced.

2

Resource allocation in MIMO systems specific to radio communication

Ghaderi Bahar, Parhizgar Naser

Archives of Electrical Engineering

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2019

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Vol. 68, nr 1

91--100

EN

The performance of the multi-input multi-output (MIMO) systems can be improved by spatial modulation. By using spatial modulation, the transmitter can select the best transmit antenna based on the channel variations using channel state information (CSI). Also, the modulation helps the transmitter to select the best modulation level such that the system has the best performance in all situations. Hence, in this paper, two issues are considered including spatial modulation and information modulation selection. For the spatial modulation, an optimal solution for obtaining the probability of selecting antenna is calculated and then Huffman coding is used such that the transmitter can select the best transmit antenna to maximize the channel capacity. For the information modulation, a multi quadrature amplitude modulation (MQAM) strategy is used. In this modulation, the modulation size is changed based on the channel state variations; therefore, the best modulation index is used for transmitting data in all channel situations. In simulation results, the optimal method is compared with Huffman mapping. In addition, the effect of modulation on channel capacity and a bit error rate (BER) is shown.

3

Performance Analysis of SPSK with Dual Polarized Transmit Antennas over Rayleigh Fading Channel

Subramani M., Neduncheran A. V., Ponnusamy V.

Journal of Telecommunications and Information Technology

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2018

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nr 1

58--61

EN

In this paper, the Space Polarization Shift Keying (SPSK) system, which is an extended version of Space Shift Keying (SSK) and includes both space and polarization dimensions with dual polarized antennas, is studied. The capacity and error probability analysis of SPSK for different polarization configurations are dealt with over the Rayleigh fading channel with a rich scattering environment. The analysis conducted shows that the SPSK with a dual polarized antenna (DP) offers better results than SPSK with a single orthogonal polarized antenna SPSK(SP), under non-LOS conditions. SPSK(DP) outperforms SSK by 4.2 dB over the correlated Rayleigh fading channel at 3 bits/s/Hz.

4

Method of processing of thermal images recorded in the beam displacement modulation technique

Kosikowski M., Suszyński Z.

Elektronika : konstrukcje, technologie, zastosowania

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2012

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Vol. 53, nr 1

68-71

EN

The article discusses the concept of acquisition and processing of thermal images recorded in the mode of spatial modulation. The basic problem related to analysing thermal images acquired in such a way is the inhomogeneity of the thermal background and significant diversification of signal levels, stemming from optic contrast differences. In the typical active thermography this is not a problem because the recording time is much shorter and the temperature background may be considered invariable and, the signal detection in the realm of time refers either to all the pixels at the same time or to every pixel separately. In the beam displacement modulation mode, the temperature signal value is recorded for successive pixel for the same lag when compared to the excitation which for large optical contrast differences brings about significant discrete signal changes with a finite relaxation time, resulting in linear signal distortion, visible as trails in the images.

PL

W artykule zaprezentowano i opisano koncepcję akwizycji i przetwarzania obrazów termicznych zarejestrowanych w trybie modulacji przestrzennej (BDM). Podstawowym problemem analizy tak pozyskanych obrazów termograficznych jest niejednorodność tła termicznego oraz duże zróżnicowanie poziomów sygnału wynikające z różnic kontrastu optycznego. W typowej termografii aktywnej nie jest to problemem ponieważ, po pierwsze czas rejestracji jest znacznie krótszy i tło temperaturowe można uznać za niezmienne a po drugie detekcja sygnału w dziedzinie czasu dotyczy albo wszystkich pikseli jednocześnie albo każdego piksela oddzielnie. W trybie BDM rejestruje się wartość sygnału temperaturowego dla kolejnych pikseli dla tego samego opóźnienia względem pobudzenia, co przy dużych różnicach kontrastu optycznego powoduje znaczące skokowe zmiany sygnału o skończonym czasie relaksacji, co wprowadza zniekształcenie liniowe sygnału, widoczne na obrazach w postaci smug.