Content for TR 38.844 Word version: 18.0.0
6.1.2.2 Method using Next smaller channel bandwidth is broadcast in SIB1 p. 15
The gNB broadcasts the DL carrier bandwidth and the bandwidth of the initial BWP (BWP#0) in SIB1. For the 7MHz allocation, SIB1 can indicate DL next smaller standard channel bandwidth, i.e., 5 MHz, and that the initial DL BWP can be set to 25PRBs:
Once the UE established the RRC connection, the gNB can account for the UE capabilities and re-configure the UE accordingly. At this point the gNB will override the carrier bandwidth value that the UE obtained from SIB1 and configure a dedicated BWP with a bandwidth that differs from the bandwidth of BWP#0. For the 7MHz allocation, gNB will override the SIB1 channel bandwidth by 10MHz and configure a larger BWP that will cover the whole 7MHz irregular channel.
While not ruled out by the RRC specification, configuration of a UE-specific CHBW wider than the carrier bandwidth indicated by SIB1 and BWPs wider than this resource grid require further consideration and may be subject to UE capability.
It should be noted that BWPs of sizes different from the already defined channel bandwidths are not currently tested within the RAN4 defined requirements. As such, UE behaviour under such configuration is not verified by RAN4 requirements.
The above configuration doesn't consider the PRB grid alignment between SIB1 channel bandwidth and UE configured channel bandwidth based on the 100 kHz channel raster.
- SIB1→ servingCellConfigCommon→ downlinkConfigCommon→ frequencyInfoDL→ scs-SpecificCarrierList→ carrierBandwidth = 25 PRBs / subcarrierSpacing = 15 kHz
- SIB1→ servingCellConfigCommon→ downlinkConfigCommon→ initialDownlinkBWP→ genericParameters→ locationAndBandwidth = 25 PRBs
- ServingCellConfig→ downlinkChannelBW-PerSCS-List→ carrierBandwidth = 52 PRBs, subcarrierSpacing = 15 kHz
- ServingCellConfig→ downlinkBWP-ToAddModList→ bwp-Common→ genericParameters→locationAndBandwidth = 35 PRBs
