5G beam-based uplink power control

2022-08-01 0 By

Power control is also slightly different due to the introduction of Massive MIMO and multiple beams in NR.For multi-beam operations, analog beam shaping can be used on the TRP and UE sides.Different beam forming gains can be observed from different TRP UE beam pairs.As the number of antenna elements increases, the beam becomes narrower and the maximum beam forming gain increases.Figure 1 illustrates the beam energy difference between the best beam and the other beams, where and represent the beam energy in the JTH highest energy beam.Assume that all UE has an LOS path and only array gain is considered.It can be observed that the beam energy may change if the uplink signal is received with a new beam.In order to receive uplink signals using suboptimal beams, changes in beam energy of up to 15 dB can be observed from the CDF curve of the antenna.Therefore, considering potential beam energy fluctuations due to changes in the TRP or UE beam, UE may need to maintain multiple path loss values corresponding to each beam.To measure the path losses between TRP and UE from different TRP beams, RS applying the corresponding TRP beam can be used.Therefore, RS in beam management process P1/2/3 is a good choice.In addition, UE can use different UE beams to receive signals from different TRP beams.Therefore, power control RS should take into account measurements from different UE beams.The power-controlled RS design has two options: Option 1: Beam management RS used in P-1 Option 2: Beam Management UE-specific CSI-RS used in P-2/P-3 For Option 1, some TRP beams can be applied to RS.However, to reduce the overhead of such RS, the number of TRP beams can be limited so that they do not cover all transmission directions well.As shown in Figure 2, the beam in RS in scheme 1 does not cover the optimal transmission direction.Therefore, the RS in option 2 can be complementary to the RS in option 1 for a more precise path loss.However, since the CSI-Rs in option 2 are UE-specific, the overhead of such CSI-Rs can be relatively high if the number of UEs connected is large.Then, multiplexing some ue measurements for a CSI-RS signal may help reduce its overhead.At the same time, it is necessary to support measurements from multiple UE beams because different beam forming gains can be observed in different UE beams.Then, for option 1, in order to allow measurement of different UE beams, some TRP beam information, such as TRP beam repetition, should be known on the UE side;For option 2, it is desirable to support measurement of multiple UE beams from a single CSI-RS.Because the orientation of each TRP Rx beam is different, the interference observed in each TRP beam may be different.Figure 3 shows the results of a semi-static system-level simulation for an indoor scenario.Assume that each UE is scheduled based on a circular scheme and can be granted four RBS.Gather results from multiple snapshots, excluding unused beams from each snapshot.Therefore, if the target SINR is considered to determine the power control factor P0, beam-specific P0 may be required because IoT may differ in each beam.Therefore, different P0 values can be configured to each beam to reflect different IoT levels.Power control Settings can be beam-specific.In addition, the beam used to receive the control channel and the data channel can be different, and the target SNR or SINR can be different.Power control Settings for the control channel and data channel should also be separated.In addition, it has been agreed that UE must support both CP-OFDM and DFT-S-OFDM waveforms.Dft-s-ofdm can improve link budgets, especially for UE with limited coverage.On the other hand, cp-OFDM waveform enables gNB receivers to adopt advanced algorithms, such as ML detection, which can result in cp-OFDM having lower target SNR or SINR compared to DFT-S-OFDM.In these respects, cp-OFDM and DFT-S-OFDM can have different target received power, and separate power control Settings can be considered depending on the waveform used.