CC2530: CC2530 Z-stack mesh

Hi, I'm using three CC2530 modules and Z-stack mesh.

I'm trying to do my sensor network project and I use one ED, one Router and one Coordinator.

My ED is Normally in deep sleep mode and it is a portable device and

when the ED going out of its parent coverage, starts sending rejoin request continuously which consumes a lot of battery.charge.I was wondering if somebody tell me can do some changes to reduce the rejoin request number?

thanks.