XBee PRO S2C- sometime packet of data received with 200-400ms delay

xbee pro s2c, 802.15.4 firmware for peer to peer connection.
I connect xbee and controller through UART. xbee is configured in Transparent mode.

Two xbee are used, both set as end devices. xbee transmit/receive 9 bytes of data, it takes around 65ms time for one cycle. i.e ( uart transmit->RF transmit->RF recieve-> uart receive->uart transmit->RF transmit->RF receive->Uart receive).

During continuous transmit/receive, sometimes it takes around 200ms time for one cycle.

1.Why it takes more time(200ms)? How to avoid the delays?

I read the complete xbee datasheet. I disable sleep support, node discovery, I/O support.
I have set MM (MAC mode)=1 (802.14.5 no Ack) to disable retries.

I found the following concepts will create delays in this firmware.
Clear channel Assessment(CCA), there is a retries available.
Acknowledgment retries are available.

  1. Can we disable the delays because of (CCA) retries and Acknowledgment retries ?
  2. Will xbee give any error command in UART receive PIN?.

Please tell us the solution for the above doubts? and out of this, let us know any other reason for delay during continuous transmit/receive?.

Your immediate response is highly appreciated…