Question about multiplexed GSM signal

Dear all, Most BTS code I have, generate only one or two 200 kHz channels, but I need to test a receiver using several (multiplexed) 200 kHz channels, composing approximately 5 MHz of total bandwidth. This should be a "valid" multiplex signal (correct and "decodable" control channel). Can anyone pointout where should I start to put together the software to generate a binary file with such signal? I guess I can inspect the code of a BTS that supports two TRX (two 200 kHz channels) but I would like to double check whether there is a more direct approach. Thanks beforehand, Marcus Dias UFPA - Lasse - LaPS