Encrypted message transmission in a QO-STBC encoded MISO wireless Communication system under implementation of low complexity ML decoding algorithm

Shaikh Enayet Ullah,Most Farjana Sharmin,Md Golam Rashed

doi:10.24297/ijct.v2i1.2617

Shaikh Enayet Ullah, Most Farjana Sharmin + Show 1 more

Open Access

https://doi.org/10.24297/ijct.v2i1.2617

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Abstract

In this paper, we made a comprehensive BER simulation study of a quasi- orthogonal space time block encoded (QO-STBC) multiple-input single output(MISO) system. The communication system under investigation has incorporated four digital modulations (QPSK, QAM, 16PSK and 16QAM) over an Additative White Gaussian Noise (AWGN) and Raleigh fading channels for three transmit and one receive antennas. In its FEC channel coding section, three schemes such as Cyclic, Reed-Solomon and Â½-rated convolutionally encoding have been used. Under implementation of merely low complexity ML decoding based channel estimation and RSA cryptographic encoding /decoding algorithms, it is observable from conducted simulation test on encrypted text message transmission that the communication system with QAM digital modulation and Â½-rated convolutionally encoding techniques is highly effective to combat inherent interferences under Raleigh fading and additive white Gaussian noise (AWGN) channels. It is also noticeable from the study that the retrieving performance of the communication system degrades with the lowering of the signal to noise ratio (SNR) and increasing in order of modulation.

Highlights

Data Security using cryptography has emerged as a topic of significant interest in both academic and industry circles
The complex digitally modulated symbols are block encoded with implemented Quasi-orthogonal space time block codes (QOSTBCs) scheme and fed into three transmitting antennas
It is assumed that the channel state information (CSI) is available at the receiver and the fading process is approximately constant during each time slot assigned for simultaneous transmission of symbols from three transmitting antennas in a Q-Orthogonal space time block codes (OSTBCs) codeword

Summary

INTRODUCTION

Data Security using cryptography has emerged as a topic of significant interest in both academic and industry circles. One main challenge is the transmission over channels that experience time-variant multipath fading Such detrimental effects in wireless fading channels can be combated using space –time block coding (STBC), an efficient transmit diversity scheme with exploitation of the diversity advantage of multi-antenna systems[3,4].Orthogonal space time block codes (OSTBCs) achieve full transmit diversity with a low (linear) maximum-likelihood (ML) decoding complexity. To overcome the low-rate constraints of OSTBCs, Quasi-orthogonal space time block codes (QOSTBCs) for four and three transmit antennas have been proposed which not achieve full diversity and have a substantially higher ML decoding complexity than the OSTBCs[5].In this present study , a low-complexity sub optimal ML decoder for coherent quasi-orthogonal space time block codes with three transmit antennas and RSA block cipher scheme based data encryption/decryption algorithm have been used. A brief description of these data processing schemes are outlined below

RSA Algorithm

Low Complexity ML Decoding

COMMUNICATION SYSTEM MODEL

RESULTS AND DISCUSSION

Conclusions