High-Accuracy Radio Sensing in 5G New Radio Networks: Prospects and Self-Interference Challenge

The emerging 5G New Radio (NR) networks will provide large improvements in mobile radio access in terms of peak data rates, latency, reliability and network capacity. One of the new technical elements compared to LTE-based networks is the support for millimeter-wave (mmW) frequencies, facilitating carrier bandwidths up to 400 MHz at the currently specified operating bands between 24-40 GHz. Such large bandwidths enable highly-accurate time-based measurements and hence ranging. Thus, in time-division duplexing (TDD) based networks, base-stations and possibly also user equipment can pursue high-accuracy radio sensing by observing the transmit signal reflections, assuming that the direct transmitter-receiver leakage or self-interference can be sufficiently suppressed. In this article, we address, analyze and demonstrate the prospects of OFDM-waveform based radio sensing in 5G NR base-stations with particular emphasis on the mmW use cases. First, basic target range and velocity estimation resolution analysis is provided for different carrier bandwidths and observation time windows, showing that close to centimeter-level ranging accuracy can basically be obtained. Then, specific emphasis is put on the analysis and suppression of the direct self-interference when executing the receiver simultaneously to transmitting. Finally, concrete RF measurements at 28 GHz operating band are provided and analyzed comprising self-interference cancellation and radar processing solutions. The obtained results demonstrate that direct self-interference cancellation can be successfully carried out, and that targets can be accurately sensed and tracked.