Fractionally Spaced Equalizer for Next Generation Terahertz Wireless Communication Systems

Higher data rates are required to support exponential growth in wireless traffic, motivating an expansion of the transmission bandwidth for sixth generation (6G) communications. The available bandwidth in the terahertz (THz) band significantly exceeds the available bandwidth in the mmWave band that has been adopted in fifth generation (5G) systems; thus, the THz band is envisioned as a pillar for 6G systems that can support data rates on the order of terabits per second (Tb/s). However, wireless communications in the THz band poses several new challenges. One of these challenges involves the practical constraint of employing a limited oversampling factor to process wideband THz signals, even while leveraging state-of-the-art analog/digital converter techniques. This limited oversampling factor – which can lead to an increased sampling timing offset – degrades the demodulation performance when it is employed in conjunction with a conventional symbol-spaced equalizer. Thus, we employ a fractionally spaced equalizer (FSE) in a THz communication system to overcome the impact of the increased sampling timing offset for a practical system that utilizes a limited sampling rate. Analysis and simulations demonstrate that the FSE can perfectly compensate the timing offset by optimally combining the available samples. Also, an approximation to the noise covariance matrix is proposed to reduce the computational complexity of the frequency-domain FSE.