Inter-User Interference Analysis in a Point-to-Multipoint Sub-THz Wireless Communication Link

This paper presents the analysis of the inter-user interference (IUI) in a multiuser wireless link operating in the sub-THz frequency range of 270 GHz to 330 GHz. The link utilizes an optoelectronic transmitter (Tx) comprising two integrated external cavity lasers with a wide tuning range, a broadband electro-optic modulator, and a uni-traveling carrier photodiode with a WR3.4 output. A conformal lens-integrated WR3.4 frequency beam-steering antenna transmits the signal to seven users distributed in space. At the user side, an electronic sub-THz receiver is used for the wireless link. A finite portion of the Rx bandwidth (270 GHz to 330 GHz) is allocated to each user. The power ratio between the individual user channels is experimentally evaluated in three different test scenarios, operating at carrier frequencies of 290 GHz, 300 GHz, and 310 GHz, respectively. This evaluation is based on the frequency response analysis of the optoelectronic Tx, the electronic Rx, and the radiation characteristics of the frequency beam-steering antenna. To the best of our knowledge, this work presents the first IUI analysis in a sub-THz wireless link operating over a distance of 10 m, with a record high gross aggregated data rate of 140 Gbps across seven users. A worst-case power ratio of -2.5 dB between adjacent channels and an average power ratio of -11.3 dB is observed, highlighting the potential of sub-THz communication for high-data-rate multiuser networks.