Over-the-air testing for 5G NR beamforming
A method and system for performing Over-The-Air (OTA) testing for 5G New Radio (NR) beamforming is presented. In one embodiment the method includes transmitting, by only the User Equipments (UEs) U and Sx, the Orthogonal Frequency Division Multiplexing (OFDM) symbols containing UL Demodulation Reference Signal (DMRS) that are orthogonal to each other during Uplink (UL) subframes; performing, by a gNB, channel estimation in the same UL subframe, precoding matrix computation, and antenna elements weighting coefficient computations; transmitting, by the gNB in a subsequent Downlink (DL) subframe, known data streams to UEs U and S x using the massive MU-MIMO beamforming coefficients; collecting by the host PC, the IQ samples from the UE U and all the victim UEs V x in the DL subframe; and evaluating a performance of the beam that was meant for UE U.
1. A method for performing Over-The-Air (OTA) testing for 5G New Radio (NR) beamforming, comprising:
transmitting, by only a User Equipment (UE) under test U and a supporting UE Sx, Orthogonal Frequency Division Multiplexing (OFDM) symbols containing UL Demodulation Reference Signals (DMRS) that are orthogonal to each other during a particular Uplink (UL) subframe;
computing, by a gNB, in the same UL subframe as the UL subframe of the transmitted DMRS signals, a channel estimation matrix, a precoding matrix, and MU-MIMO antenna element weighting coefficients;
transmitting, by the gNB in a subsequent Downlink (DL) subframe, known data streams to the UE under test U and the supporting UE S x using the computed MU-MIMO antenna element weighting coefficients;
collecting, by a host PC, IQ samples from the UE under test U and a plurality of victim UEs V x in the subsequent DL subframe; and
evaluating performance of the transmitted known data stream received at the UE under test U.
2. The method of claim 1 wherein the evaluating a performance of the transmitted known data stream received at the UE under test U comprises using a value of an Error Vector Magnitude (EVM) of demodulated Quadrature Amplitude Modulation (QAM) symbols from the UEs U and Vx.
3. The method of claim 2 further comprising calibrating a value of EVM using a thermal noise variance σ 2 from U and Vx.
4. The method of claim 1 , further comprising: a plurality of User Equipments (UEs), wherein a first UE (U) is used for assessing the performance of a transmitted test data stream directed towards it, wherein at least one second UE (Vx) is a victim UE and wherein at least one using a third UE (Sx) to increase the dimension of a matrix H for a given test.
5. The method of claim 4 wherein the victim UEs are used to evaluate the deviation of an intended beam from U.
6. The method of claim 5 wherein the victim UEs are placed at horizontal angles of θ x relative to U.
7. The method of claim 5 wherein the victim UEs are placed at vertical angles φ x relative to U.
8. The method of claim 5 wherein the system evaluates a performance of the beam that was meant for UE U using a value of an Error Vector Magnitude (EVM) of demodulated Quadrature Amplitude Modulation (QAM) symbols from the UEs U and Vx.
9. The method of claim 8 wherein a value of EVM is calibrated using a thermal noise variance σ 2 from U and Vx.
10. The method of claim 4 wherein the DUT includes a digital baseband section and an analog RF section.
11. The method of claim 4 wherein the host computer schedule Uplink transmissions from each of the UEs.
12. The method of claim 11 wherein the host computer collects the IQ samples from a plurality of UE simulators to do performance analysis.
13. The method of claim 4 wherein a gNB and a plurality of UE simulators are synchronized using a master clock.