Issue to send at commands using echo-e at command not respond but using same serial at minicom its worked

i have router in which one usb port is there where i am using huawei e3276 modem .
i am using ncm protocol on dongle and through kmod -usb-serial-option package it gives two serial port /ttyUSB0 and ttyUSB1 and i send at command using minicom ttyusb0 it work fine and respond properly.
but i am using echo -e "AT \r\n" > /dev/ttyUSB0 && cat /dev/ttyUSB0 it is not respond .
please help me if any idea why it is happened

Be aware that busybox echo(1) does not support GNU extensions (such as the -e parameter), but implements only the bare minimum subset as defined for a POSIX/ SUSv4 compliant echo(1) implementation.

For portability and interoperability reasons you should prefer to use printf(1), instead of echo(1).

Thank for reply.....
echo is worked actually i tested it write to serial port using echo -e "AT \n" >/dev/ttyUSB0 on one terminal and on another terminal i read it cat < /dev/ttyUSB0 so it read successfully AT .but my issue is AT command not respond or not ok coming .but using minicom it respond please help me

You won't see the replies using that method.

The actual output is on the physical serial Tx/Rx pins.