Phone acting as a BTS

Hi, Since the beginning, I'm wondering if it would be possible to turn one of those cheap phone into a BTS. I'm n ot talking a full featured BTS and the mod will involve hardwares changes obviously. The more I look at it and the more I think it might work. No, I'm not crazy, please bear with me until the end of this post :) So, what are the obstacles (taking the C118 as an example): * RX filters : Obviously you would need to remove one and replace it with one for the good band. I would only replace one of them so that you can use the 900 band for BTS and the 1800 band for MS for example (so that you can still listen to a official bts and calibrate the clock). * RX/TX switch Those have ports that have frequency bands ... but .. do they really filter that much ? * MS can't TX/RX simultaneously. I think you can take advantage of the fact. Imagine that you only ever allocate channels on TS0,1 & 2. ( BCCH+SDCCH/4 + 2*TCH/F ), you could divide your time like this : TS0 - Capture FCCH of a nearby station to calibrate local vcxo TS1 - Our BTS TS0 TX TS2 - Our BTS TS1 TX TS3 - Our BTS TS2 TX TS4 - Our BTS TS0 RX TS5 - Our BTS TS1 RX TS6 - Our BTS TS2 RX TS7 - nothing ... But this can still be a battery powered handheld BTS :) Sylvain