You can go by this.
Check if equipped SDCCH capacity is sufficient to cater the BBH SDCCH Traffic.If YES,
A)Check for H/W issues
B)High HR Traffic
D)No. of SDCCH configured/TRX
E)Change the LAC boundary if SDCCH usage due to LU is very high.
F)Go for Carrier Augmentation if Cell Utilisation is High
A)Add SDCCH and check.
B)Enable Dynamic SDCCH,if disabled.
If HR Traffic is high,signalling load will obviously be higher.(but check first if your HR triggering is rational,you should trigger HR only when FR utilisation is >80%).So,cells where HR Traffic is higher,you need to augment the LAPD signalling from 16 KBPS to 32 KBPS.