Content for TR 38.844 Word version: 18.0.0
6.2.3 Overlapping CA (two cells) p. 26
6.2.3.1 General Aspects p. 26
Using the Overlapping CA approach to support irregular spectrum is one of the methods without the need of introduction of new dedicated channel bandwidths for both UE and BS. Figure 6.2.3-1 shows overlapping CA from network perspective, in which BS supports the intra-band overlapping CA, while UEs only supports the single CC with the existing channel bandwidth. And Figure 6.2.3-2 shows overlapping CA from UE perspective, in which both BS and UE support the intra-band overlapping CA to use all RBs, and the UE supports intra-band non-contiguous CA for the combination as well.
Even two CCs are overlapped in frequency domain, the network can configure different CCs with non-overlapping BWP to avoid the conflict of physical signals or channels.
In summary,
- No new gNB channel bandwidth is required
- Legacy UE using existing lower regular NR channel bandwidth can operate in either carrier
- Overlapping CA approach needs to have PRB grid alignment between overlapping CCs
- From UE perspective, overlapping CA is optional supported in DL only
- Irregular bandwidth utilizing overlapping CA approach cannot be combined with NR CA combinations
- From UE perspective, the solution requires UE support of intra-band non-contiguous CA for the combination
6.2.3.2 Configuration and signalling aspects p. 27
In this approach, network configures two cell-defining SSB in the allocated irregular spectrum block and the two cells are configured with overlapping regular channel bandwidth. From procedure wise, the network can indicate UE the location and bandwidth by using the existing procedures on individual CC. From UE perspective, there are two independent cells with overlapped bandwidth. For a particular UE, CA with overlapped cells can be configured to fully utilize the network bandwidth.
