When I connect gsm with lpc 2148 I am not receiving any response from gsm. Program is correct I have seen it's output on hyperterminal.what can be the problem please help me.
So which part of, "TX on modem would likely want to go to TX on micro-controller" did you not understand?
"Check naming and connectivity expectations. Check baud rate, and voltage level expectations"
Have you done that?
See: www.avrfreaks.net/.../2356086
Try monitoring the comms between your GSM and microcontroller:
www.avrfreaks.net/.../2306116
See also:
www.avrfreaks.net/.../2336161
Note that this has nothing to do with Keil!