Terahertz-Band MIMO Systems: Adaptive Transmission and Blind Parameter Estimation

Abstract

Terahertz (THz)-band communications are a key enabler for future wireless communication systems, that promise to integrate a plethora of data-demanding and delay-sensitive applications. Towards this end, THz transceivers are expected to be reconfigurable and highly adaptive. Since propagation losses are very high at the THz band, dense ultra-massive multiple-input multiple-output (UM-MIMO) antenna arrays are required to combat the resultant short propagation distances. Such arrays can be made adaptive by dynamically tuning the modulation types, operating frequencies, and indices of transmitting antennas. This flexibility and compactness in design, however, should be complemented by efficient signal processing techniques at the receiver side for efficient resource utilization. In this paper, we consider the design of efficient adaptive THz-band UM-MIMO systems. We first study the THz channel conditions and advocate the practicality of adaptive transmission schemes. Then, we develop low-complexity blind parameter estimation techniques for the receiver. We propose a tertiary hypothesis test based on power comparison for antenna index and modulation mode detection and we derive the corresponding closed-form expressions of error probabilities. We further propose low-complexity frequency index detectors and modulation type estimators.