  The focus of this paper is to demonstrate an over-the-air (OTA) 5G new radio
(NR) sidelink communication prototype. 5G NR sidelink communications allow NR
UEs to transfer data independently without the assistance of a base station
(gNB), which enables V2X communications, including platooning, autonomous
driving, sensor extension, industrial IoT, public safety communication and much
more. Our design leverages the open-source OpenAirInterface5G (OAI) software,
which operates on software-defined radios (SDRs) and can be easily extended for
mesh networking. The software includes all signal processing components
specified by the 3GPP 5G sidelink standards, including Low-Density Parity Check
(LDPC) encoding/decoding, polar encoding/decoding, data and control
multiplexing, modulation/demodulation, and orthogonal frequency-division
multiplexing (OFDM) modulation/demodulation. It can be configured to operate
with different bands, bandwidths, and antenna settings. The first milestone in
this work was to demonstrate the completed Physical Sidelink Broadcast Channel
(PSBCH) development, which conducts synchronization between a Synchronization
Reference (SyncRef) UE and a nearby UE. The SyncRef UE broadcasts a sidelink
synchronization signal block (S-SSB) periodically, which the nearby UE detects
and uses to synchronize its timing and frequency components with the SyncRef
UE. Once a connection is established, the next developmental milestone is to
transmit real data (text messages) via the Physical Sidelink Shared Channel
(PSSCH). Our PHY sidelink framework is tested using both an RF simulator and an
OTA testbed with multiple nearby UEs. Beyond the development of synchronization
and data transmission/reception in 5G sidelink, we conclude with various
performance tests and validation experiments. The results of these metrics show
that our simulator is comparable to the OTA testbed.
