XbeeZB s2 throughput

I have purchased two XBee XB24-Z7WIT-004 S2 module. I have configured one as coordinator and another as end device. Both coordinator and end device are configured to operate at 115200 baud rate with host. End device is interfaced to ARM7 lpc2148 micro controller. Coordinator is connected to PC bu usb and XCTU app. I want send 500 packet in one 1 sec for 5 minute continuously. Each packet contains 20 byte of data.
Through serial port of micro controller I am able to send required amount of data to a terminal program on PC successfully. But when I am connecting end device to same serial port I am unable to achieve required throughput.

Please suggest me settings needed for higher throughput. As my deadline is approaching any suggestion will be highly appreciated.

Thank you in advance

So, to understand better, are you trying to send 500 x 20 = 10,000 bytes in 1 second? I don’t think that the XBee will be able to handle that properly.
Are you using flow-control? Are you in AT or API mode?