Thank you for replying me.
The transmission distance is around 300m and only one byte is enough to send the data from slave to master.
As I know Xbee/Zigbee uses inter device communication which will consume much power from slaves. Because I have to consider the battery life of the slave devices, I though of having this method,
"The slave send the button pressed event only when button is pressed, if the master does not reply, slave waits until the button is pressed again and transmite the number of button presses (one byte length)".
I was thinking about frequency hopping because of,
If I use same frequency for all slaves with addressing; and a slave(slave-B) tries to initiate the communication with master while another slave(slave-A) is communicating will lead to loose the data form master. The both slave can know that they lost the communication and can try to send data again,
But there are more than 200 slaves
The attachment will describe the network