Challenges in LoS Terahertz MIMO

This paper examines a 2x2 LoS (Line of Sight) MIMO (Multiple Input Multiple Output) channel for terahertz communications. Utilizing measurements, we extract channel models which are then used in a simulation to produce bit error rate curves for uncoded QPSK (Quadrature Phase Shift Keying). The specific focus of this work is on studying the impact of changing transmitter receiver distances and relative orientation. Since the terahertz band has a small wavelength, such small movements can have a large impact on the channel. The results support this intuition and show that horizontal displacements of one antenna relative to another by distances as small as 1-2 cm can cause the bit error rate to increase by an order of magnitude. Similarly, utilizing sub-optimal antenna spacing at the transmitter and receiver can also result in similar types of performance degradation. This study illustrates that while LoS MIMO is an effective approach for utilizing the large terahertz bandwidth, we need to consider the effects of antenna deployments.