how to reduce network joining time period

MY XBEE-PRO-S2B module configured as End Device is taking long time period for network joining after pin hibernate.
Initial node joining time after power on is 24sec.
If NJ=0xFF with NT=3C, node joining time taken is 23sec with Repeater.
If NJ=0x0A or 0x02 with NT=3C, node joining time taken is 6sec with repeater.
There is no effect on node joining time if NT=0x20.
I want to reduce the node joining time to 0 for perfect operation as my device is Low powered, I can’t spare this much time for joining.
Kindly suggest me best possible way, like what changes i need to do.
Thank You

Are you using DHCP? If so it could be the reason for the delay, try assigning a static IP to see if the association time changes.

Sorry ignore answer thought you were asking about S6B