communication between coordinator xbee and slave xbee is slowing down. coordinator xbee receives little data

hi guys, I have a question. I make line follow car. I want to my robot communication with my computer because I want to watch position of the car on the line in this reason I use xbees. if my problem will come 20(max) seconds after the communication between the car and the computer started coordinator xbee(my computer) is slow for retrieve data but I want to constand communication. What is my problem? How I can solve this problem? (I am sorry for my bad_english :))

First off, the modules you are using are Mesh based product and are NOT suited for Streaming data.

Next, the default configuration of the Coordinator is Broadcast mode while the router is unicast mode. To reduce the required latency for a broadcast transmission to be re-transmitted, set the Coordinator for Unicast mode by setting the Dl and DH of the Coordinator to the SL and SH of the router.