Planning the B1 Threshold value for NSA 5GNB addition
Too High RSRP - Potential 5G connections will be reduced. This will prevent offloading from 4G to 5G and will reduce end user throughput.
Too low RSRP - 5G Connections will be attempted at bad 5G Radio coverage, so either 5G RACH will not be successful or it will drop quickly.
Tests have confirmed that If 5G connection is attempted at low B1 there can be a series of 5G RACH Failures, which will lead to decrease in 4G Throughput as well.
If 5G Addition at low RSRP takes place, chances are that 5g connection can drop quickly and this will in turn affect the retainability KPI as well.
Considerations while setting up B1 Threshold:
5G bandwidth – If 5G bandwidth is large, even poor 5G radio conditions can give significant improvement in combined 4g/5g throughput. So B1 Threshold should be less for high 5G bandwidth and high for low 5G bandwidth.
If the network is using A2 based release from 5G, then the b1 threshold should be considerably higher than A2 threshold to avoid any ping pong.
5G Uplink Quality – B1 threshold is a measure of downlink condition, while after this condition are met, UE would need 5G RACH to succeed, while planning B1, a safety margin should be added for uplink.