ICTACT Journal on Communication Technology

Zenitha Rehman ¹, H. M. Savitha ¹

Affiliations
1 Department of Electronics and Communication Engineering, St Joseph Engineering College, IN

Abstract

Multiple Input Multiple Output (MIMO) systems with multiple antenna elements at both transmitter and receiver ends are an efficient solution for wireless communication systems. They provide high data rates by exploiting the spatial domain under the constraints of limited bandwidth and transmit power. Space-Time Block Coding (STBC) is a MIMO transmit strategy which exploits transmit diversity and provides high reliability. Implementation of orthogonal space-time block codes (OSTBCs) for a two transmitter-two receiver system under AWGN (Additive White Gaussian Noise) channel and flat fading channel is performed. Alamouti code is employed for the STBC. The modulation techniques used are BPSK, QPSK and 16-QAM. Decoding is done using the Zero Forcing (ZF) algorithm and Maximum Likelihood (ML) algorithm. The BER Performance of each modulation scheme is compared with the un-coded version of the same. Performance comparison between the two decoding techniques is also done. It is found that ML detection offers a slightly better performance for BPSK and QPSK system than ZF detection.

Keywords

Alamouti Code, Flat Fading, STBC, ZFD, MLD.

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H. M. Savitha ¹, Muralidhar Kulkarni ¹

Affiliations
1 Department of Electronics and Communication Engineering, National Institute of Technology, Karnataka, IN

Abstract

A comparison of the performance of hard and soft-decision turbo coded Orthogonal Frequency Division Multiplexing systems with Quadrature Phase Shift Keying (QPSK) and 16-Quadrature Amplitude Modulation (16-QAM) is considered in the first section of this paper. The results show that the soft-decision method greatly outperforms the hard-decision method. The complexity of the demapper is reduced with the use of simplified algorithm for 16-QAM demapping. In the later part of the paper, we consider the transmission of data over additive white class A noise (AWAN) channel, using turbo coded QPSK and 16-QAM systems. We propose a novel turbo decoding scheme for AWAN channel. Also we compare the performance of turbo coded systems with QPSK and 16-QAM on AWAN channel with two different channel values- one computed as per additive white Gaussian noise (AWGN) channel conditions and the other as per AWAN channel conditions. The results show that the use of appropriate channel value in turbo decoding helps to combat the impulsive noise more effectively. The proposed model for AWAN channel exhibits comparable Bit error rate (BER) performance as compared to AWGN channel.

Keywords

Bit Error Rate, Orthogonal Frequency Division Multiplexing, Turbo Codes, 16-QAM, AWAN Channel.

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