International Journal of Ambient Systems and Applications (IJASA) Vol.9, No.1/2, June 2021 DOI:10.5121/ijasa.2021.9202 7 COMPARISON OF BIT ERROR RATE PERFORMANCE OF VARIOUS DIGITAL MODULATION SCHEMES OVER AWGN AND RAYLEIGH FADING CHANNELS USING SIMULINK Md. Firoz Ahmed 1 , Md. Faysal Ahmed 1 and Abu Zafor Md. Touhidul Islam 2 1 Department of Information and Communication Engineering, Rajshahi University, Rajshahi-6205 Bangladesh 2 Department of Electrical and Electronic Engineering, Rajshahi University, Rajshahi-6205 Bangladesh ABSTRACT Digital modulation increases information capacity, data security, and system availability while maintaining high communication quality. As a result, digital modulation techniques are in higher demand than analog modulation techniques due to their ability to transmit larger amounts of data. Amplitude Shift Keying (ASK), Frequency Shift Keying (FSK), Phase Shift Keying (PSK), Differential Phase Shift Keying (DPSK), and Quadrature Amplitude Modulation (QAM) are critical components of current communications systems development, particularly for broadband wireless communications. In this paper, the comparison of bit error rate performance of different modulation schemes (BPSK, QPSK, and16-QAM) and various equalization techniques such as constant modulus algorithm (CMA) and maximum likelihood sequence estimate (MLSE) for the AWGN and Rayleigh fading channels is analyzed using Simulink. BPSK outperforms QPSK and 16-QAM when compared to the other two digital modulation schemes. Among the three digital modulation schemes, BPSK is showing better performance as compared to QPSK and 16- QAM. KEYWORDS AWGN Channel, Rayleigh Fading Channel, CMA, MLSE 1. INTRODUCTION The performance of transmitting and receiving systems is critical in recent times for rapidly growing wireless technologies. Digital modulation schemes help to advance mobile communications by increasing wireless network capacity, speed, and quality [1]. The strategies of digital modulation increase information-carrying capacity, communication quality, data security, and RF spectrum sharing, allowing for more services. The choice of digital modulation scheme will significantly affect the characteristics, performance, and resulting physical realization of a communication system. There is no universal 'best' scheme, but some will be a better fit than others depending on the physical characteristics of the channel, required levels of performance, and target hardware trade-offs. The required data rate, acceptable latency, available bandwidth, anticipated link budget, and target hardware cost, size, and current consumption must all be taken into account [2]. The next-generation wireless communication systems require higher data transmission rates in order to meet the higher demand for quality services [3]. A major transition from analog to digital