MATLAB Source Code Example for Raised Cosine Roll-Off System Implementation

The raised cosine roll-off system is a fundamental pulse shaping technique in digital communications, primarily used to eliminate inter-symbol interference (ISI). The MATLAB implementation involves three key stages: parameter configuration, filter design, and performance validation. The system begins by defining the roll-off factor (α), which ranges between 0 and 1 and determines the trade-off between spectral efficiency and interference immunity. Typical applications select compromise values between 0.3-0.5. The symbol period and sampling rate must then be configured to satisfy the Nyquist sampling theorem requirements. The critical implementation step involves generating the root raised cosine filter using MATLAB's rcosdesign function. This function requires three main parameters: the roll-off factor, filter span length, and oversampling ratio. The resulting filter exhibits a distinctive "bell-shaped" characteristic in the time domain, while its frequency response shows smooth transition bands at the cutoff frequencies. To validate system performance, the filter can be applied to randomly generated digital sequences through convolution operations. The output signal's time-domain waveform demonstrates smooth transitions, and eye diagram analysis provides visual confirmation of ISI suppression. Finally, power spectral density plots verify whether the system achieves distortion-free transmission within bandwidth constraints. This implementation can be directly adapted for modulation systems like QPSK and QAM, serving as a fundamental building block in communication link simulations. Practical engineering applications may require additional considerations such as group delay equalization and multipath channel adaptation enhancements.