Performance Comparison of Digital Quaternion Modulation System with OFDM Systems

Abstract

Every communication system tries to achieve a lower bit error rate, ensuring minimum data loss. In this thesis some previously proposed methods to improve BER in the military are discussed and a recently digitized quaternion modulation system using FSK is presented to enhance system‟s BER efficiency. Using FSK modulation scheme, the four quaternion coordinates are generated and transmitted. The implementation and theoretical derivations of the proposed system is discussed in detail. After ensuring the orthogonality of proposed system theoretically, comparison is done between proposed system and OFDM system. The BER performance of quaternion modulation system and OFDM system is compared using idealistic AWGN and flat Rayleigh fading channel. MATLAB results show the superior BER performance of the proposed system in comparison with OFDM. In OFDM, several separately modulated subcarriers cause the system to have high peak value compared to the average of the system. OFDM with high PAPR causes system to become very sensitive to nonlinear distortions produced by analog components, i.e. high-power amplifier, D/A converters and A/D converters. Digitized Quaternion System using FSK modulation scheme gives high level of robustness against errors with acceptable PAPR. There are various applications where to achieve lower BER is more essential as compared to bandwidth utilization. The proposed scheme finds use in applications requiring improved BER such as Military communication, point-to-point communication and point-tomultipoint communication.