Wireless real-time transmission of 101GHz terahertz signals over 19.6 km: fully solid-state prototype design and experimental validations

This study addresses the growing demand for high-capacity, long-distance wireless connectivity in applications such as fixed wireless backhaul, high-capacity access networks, and beyond-6G ultra-long-range links. We develop a spread-spectrum terahertz (THz) wireless transmission system operating at 101 GHz and validate its performance through field trials over 10.9 km and 19.6 km. To tackle the key signal-processing challenges of long-range THz links, three hardware-feasible algorithms are introduced: (1) a stage-wise digital predistortion scheme for power-amplifier linearization; (2) a low-complexity energy-aggregation strategy that enables robust synchronization of long spreading codes at low SNR; and (3) a decision-directed LMS equalizer that mitigates local-oscillator-induced phase noise. The prototype operates at a fixed 2.25 Gbps air-interface rate. In field experiments, it delivers 1.67 Gbps user throughput over 10.9 km without spreading and 16.7 Mbps over 19.6 km using a spreading factor of 100. Larger spreading factors further improve post-despreading SNR and link margin at the cost of proportionally reduced throughput. These results demonstrate that compact solid-state THz transceivers, combined with tailored baseband algorithms, can sustain real-time transmission over multi-kilometre distances. They also highlight the coverage-throughput trade-off introduced by spreading, offering practical guidance for designing future long-range THz communication systems.