Handling of radio frequency front-end group delays for round trip time estimation
摘要
說明書
These interferences can be avoided by scheduling calibration gaps wherein these interfering transmissions are allowed and the transmissions they would have interfered with are instead suspended. The occurrence (including duration, periodicity, etc.) of these gaps could be signaled by gNB to the UE, to allow UE to perform group delay calibration for FDD. A base station could also perform similar calibration by coordinating with its neighboring base stations, for example, over X2 or Xn interface, to schedule interference-free calibration gaps, which may be transparent to UEs (i.e., the UEs are not scheduled on uplink, and may be unaware that the reason they are not scheduled is to allow neighboring gNBs to transmit on the uplink frequency).
Alternatively or in addition thereto, if the base stations are sufficiently separated from each other, as is usually the case, they may perform their calibration transmissions at low enough power to avoid the interference. This may be feasible since the receiver for these transmissions is physically very close, being within the base station itself. Note that such calibration gaps may be necessary only for devices that include the additional transmitter transmitting at the receive frequency, needed to make use of them. Hence the presence of this transmitter may be indicated, for example, as a UE capability. Similarly, the presence of the additional receiver for the transmit frequency may be indicated, for example, as a UE capability. A UE may have one or both of these capabilities. If only one of them is supported, the UE may be able to compensate for a part of its group delay (eg, only the txgd(i,kT) or only the rxgd(j,kR) but not both), which would limit the accuracy of its RTT estimate.
