need transceiver circuit

I need transceiver circuit for interfacing with 8051 based microcontroller for a minimum distance of 1Km.

Thanks in advance

Questions:
-speed requirements ?
-security ?
-power consumption requirements ?
-data or voice (i guess data because of -51)
-price target ?
And of course it must be legal.
Frequency bands are country dependant.
Perhaps some of the ISM-bands will do ?
Many manufacturers exists.
Serial interface is convenient to use and there are
ready made solutions (though expensive).
Special attention must be payed to protocol.

Happy projecting...

answers:
-speed requirements ? 9600bps or any RS232 standard
-security ? no need (secured by sotware)
-power consumption requirements ? doesn't matter
-data or voice (i guess data because of -51) ? data
-price target ? doesn't matter

thanks

try for chipcon cc1000 or cc1010 with 8052 core www.chipcon.com