Single-Shot Single-Antenna Motion Sensing in THz Networks
We have designed the world's first single-shot single-antenna motion tracking system for THz networks. We proposed a novel THz node architecture in which both transmitter and receiver are equipped with a single leaky-wave antenna (LWA) structure. LWA is a passive device consisting of two metal parallel plates with a slot on one side. An injected signal propagating inside the waveguide “leaks” out into free space, with the unique property that the emission angle is coupled to the frequency of the injected signal.
We excite the LWA with a time-domain THz pulse and leverage its spectral-spatial properties to form unique angular-dependent spectral signatures that we call a “THz Rainbow”. We demonstrate how to sense and track device motion (translation and rotation) by processing the power spectrum provided by a non-coherent receiver. Our solution is single-shot (one THz pulse transmission), single-antenna, and scalable to multiple clients. This fast and robust procedure enables low-latency client tracking in a directional THz network, for the first time.
Multi-stream Multi-User Transmissions in 60 GHz WLANs
We enable multi-user simultaneous transmissions in mmWave bands taking into account the limitations of commercial systems. In particular, commercial phased arrays generate irregular and overlapping bams as antenna weights are configured via low-resolution phase-shifters. Moreover, power consumption considerations yield a disparity between the number of RF chains and antenna elements in practical systems making direct channel sounding infeasible.
We leverage the beam irregularity, GHz-scale sampling rate, and channel sparsity to design a context-aware system that identifies diverse paths that can carry independent data streams simultaneously. We strategically transmit few beacons and couple the measured CIR with the knowledge of radiation patterns to sense the key component of the sparse mmWave channel. We have also demonstrated how to configure multi-stream beams over diverse paths to minimize inter-user interference. We have developed a programmable SDR and have conducted the first experimental exploration of multi-user multi-stream communication in the mmWave spectrum.
Wireless Security in mmWave and Terahertz Networks
In the modern era of wireless interconnected devices, the issue of security is a forefront concern. One commonly cited advantage of wireless communication in mmWave and Terahertz regime is enhanced resilience against malicious attacks, as highly directional links are presumably more secure against eavesdropping and jamming. We have explored the security vulnerabilities in next-generation wireless communications. In particular, we have studied, for the first time, the security of a THz link created by a leaky-wave antenna. We have performed an analytic and experimental investigation and showed how the link’s unique angle-frequency coupling impacts security, in some cases aiding the adversary and in other cases hindering the adversary.
Mobility Tracking and Localization via Light Sensing
We have designed and implemented the first light-controlled radio system that exploits light intensity measurements from a light source in close proximity of wireless AP (e.g., AP’s indicator LED) or other indoor luminaries to localize and track a mobile client. Such information is then used to adapt mmWave beams under mobility with zero training overhead. On the hardware side, we built a custom dual-band (60 GHz and visible light) hardware testbed and demonstrated that our solution successfully offers robust multi-Gbps connectivity for directional mobile mmWave networks yet eliminates the overhead of an exhaustive radar-like beam search (suggested by IEEE 802.11ad) altogether.