FPGA-based Implementation and Evaluation of Realtime OFDM Phase Compensation in 5G

In the New Radio (NR) standard which is standardized by 3GPP as a candidate for 5G mobile communication system, Orthogonal Frequency Division Multiplexing (OFDM) has been selected as the waveform for the air interface. Unlike the 4G Long Term Evolution (LTE), where the carrier frequency between the transmitter and receiver are always at the same locations, in NR, they can be at different frequencies. In such case, this leads to the phase ramped up at the receiver which cannot be recovered if the OFDM symbol is not equipped with reference signal for channel estimation and equalization. In this paper, we present our model for this issue and how to eliminate it by compensating the phase difference at both transmitter and receiver. We also implement this approach in Field Programmable Gate Array (FPGA) and validate it in real hardware testbed. The result show that with phase compensation, the received signal constellation is significantly improved.