Gsm bands multiplexing !!!

Hello Everybody
I'm alaa from egypt n i need some help here, i'm doing my graduation project.
One of the tasks in our project is to design RF circuit that could receive GSM signals over both 900 & 1800 bands and compress them to less than 32 MHZ so that we could sample it with the usrp AD ship which has 64 M sampling rate.

So our supervisor told us to use ADS to design that circuit but unfortunately i don't have any experience using that tool beside i don't know what are the steps to take in order to design such a circuit ..

So please i need any help to put me on the right track.

Thanks in advance.

What is the GSM signal? Voice, EDGE? What is the signal bandwidth?
Say one channel bandwidth is less than 1M. You should design a LO, maybe 2 LO, to down-convert the 900M or 1800M signal to baseband for sampling. You can refer ADS samples, there are several telecomm systems.

thanks for relying tony, GSM signal would be voice i've thought of an approach but may be it's not applicable or can't be implemented and i need your opinion .

mainly we want to scan the GSM bands so that we could decide were should the software Bts work on the frequency spectrum ...
we have 25mega ( 890 to 915 ) and 75mega (1710 to 1785 ) and we want to multiplex them over some carrier and decimate them to something lower than 32mega

1) multiply the rf signal by LO with frequency 397.5 mega so that the 900 band would be fom 372.5 to 397.5 , and the 1800 band would be from 397.5 to 472.5 .
2) now we've got the total signal with bandwidth 100M from 372.5 to 472.5 and this signal would be applied to the WBX daughterboard which has a software controlled LO, there we could down-convert the signal to baseband ( by setting this value to 372.5 for example ), but the problem is that the WBX allows maximum bandwidth of 40M, so is there's any method to decimate the 100M signal to somethin like 32M ......
3) then ( if we could decimate the 100 mega signal to 32 mega and then multiply by the WBX's LO to get the baseband signal ) the 32mega signal would be applied to the ADC.

Sorry for taking too long time to reply.

1. you can't implement your ideas. Spectrum compression can't conduct on GSM signals, because the bandwidths includes many channels, and each channel only occupies bandwidth less than 1M, I forgot the details.
2. Good news is that for each GSM operator, they only occupies about 5M or 10M bandwidth. So you can use 1 WBX for 900M GSM and 3 WBXs for 1800M GSM, and you need about 4 LOs.