Scalable Multi-User Terahertz Wireless Networks With Angularly Dispersive Links

THz communication can realize the next order of magnitude in data rate and user densities due to the availability of wide THz-scale spectral bands. Wide bandwidth links can exhibit angular dispersion, i.e., frequency-dependent radiation direction. While angular dispersion has enabled path discovery and dynamic beam steering via frequency tuning, multi-user communication in THz links remains an unaddressed challenge. This paper presents the first study and performance evaluation of multi-user THz WLANs with angularly dispersive links. We employ a single parallel-plate Leaky-Wave Antenna (LWA) for THz directional transmission and present a multi-user communication strategy that exploits angular dispersion and angular separation of users and provides all-spectrum access to users located in different directions with the objective of aggregate rate maximization. With analytical model-driven evaluations and over-the-air experiments that inform our trace-driven emulation of multi-user conditions, we show how the multi-user performance of an angularly dispersive LWA link fundamentally depends on frequency, angle, and bandwidth utilized by users through non-linear mechanisms. As increasing bandwidth yields a larger signal footprint in LWA links, we demonstrate that as compared to the model prediction, not only is the aggregate data rate maximized with wider beams, but the experimental link is far better even for practical irregular beams with side lobes and asymmetry. Our experimental findings reveal the potential of leveraging angular dispersion and users’ angular separation to establish a scalable THz wireless link that offers contention-free or medium access control-free access. Our results demonstrate the feasibility of accommodating up to 11 simultaneous users, making it a promising candidate solution for densely populated user environments.

I. Introduction

Recent advances in WLANs have employed multi-user MIMO to realize multi-Gb/sec data rates via multiplexing multiple data streams in 60 GHz, as standardized in IEEE 802.11ad/ay [1], [2]. Today, THz communications is envisioned as the key building block to realize the next order of magnitude in data rate and user densities for the next generation wireless networks [3], [4], [5], [6], thanks to the availability of the ultra-large bandwidth (0.1 to 1 THz) in THz spectrum. These THz links exhibit a unique property of angular dispersion, where higher frequencies radiate with maximum power towards smaller angles. Yet, due to the high pathloss in THz regime, directional transmission is required and therefore Leaky Wave Antennas (LWA) which work on the same principle of angular dispersion, stands to be a promising candidate for THz scale networking. The steering capabilities coupled with the wide bandwidth support offered by angularly dispersive links such as such as those based on LWAs has enabled beam steering by a simple mechanism of tuning the carrier’s center frequency [7] and efficient path discovery [8]. While all these works demonstrate the capabilities of angularly dispersive links to transmit and receive directional transmission from a single user, realizing multi-user communication with angularly dispersive THz links is still an open problem.