CC2538: AF_DataRequest and Collision detection

Part Number:CC2538

Hello.

I have an endpoint, which sends about 60 packets per second with 72 bytes of data. But my router does not recived all the sent packets.

I counted packets on the endpoint before send and on the router after receive and got the numbers: for every 5000 sent packets I receive only 4900.

I tried to use AF_ACK_REQUEST flag, but the situation became worse: for 5000 packets router receives only 2300.

So I have some questions:

- am I right when I using AF_ACK_REQUEST flag to get more reliable link?
- may it be error in colision avoidance? How the collisiion avoidance in z-stack works?

Used Z-stack version is 3.0.1, hardware is CC2538.