Content for  TR 38.844  Word version:  18.0.0

Overlapping channels from the network perspective works with all the legacy UEs. As presented in previous sub-clauses, from an individual UE perspective, this is just a standard Rel-15 channel and no special UE side enhancements are needed. Thus an operator can use this solution with the whole ecosystem of available devices.

• No impact to legacy UEs. UEs which support this solution would be reconfigured in RRC_CONNECTED, there is no change to UE behaviour in IDLE mode which could create potential issue with legacy UE compatibility

This option is for UEs that have no support for using an irregular bandwidth. Such a UE will apply the next smaller bandwidth referring to the channel filtering. It will never receive more than the PRBs defined for the next smaller bandwidth and it follows the conventional way of aligning the center frequency of the channel in both DL and UL. These UEs will camp on the same frequency part of the channel since the SIB1 only has one allocation. In CONNECTED mode, the network can configure UE with the UE specific ServingCellConfig IE which configures the point A reference that may shift the UE to operate either at the lower side or the upper side of the irregular bandwidth. In most of the configurations with an irregular BW below 10 MHz, legacy UEs can only use one side of the irregular BW unless - as in the case of overlapping CBWs from network perspective - a second, time-staggered SSB is spent.