Testing protocol stack with OsmocomBB (cheap way)

Hi all, going through the documentation, I am trying to figure out what would be the best way to have whole protocol stack communication with OsmocomBB. Now, I understand that osmocon can be used to load layer1 into phones RAM, so that this code turns on Calypso and communicate with DSP with AT commands. Then osmocon gets messages from layer1 via RS232 and can distribute them to the mobile application, which sends them to layer23 for further processing or via GSM tap to Wireshark or outputs them on stdout. What I am most interested in how do we insert pacgaes on the other side of the stack, i.e. via telephone air interface (packets that will traverse through Rita, Iota, Calypso down to stdout of host). From what I understand we need some kind of BTS, and I can see that GNU Radio is used for this purpose. But for this, as I understand USPRP (http://en.wikipedia.org/wiki/Universal_Software_Radio_Peripheral) FPGA motherboard with both RX and TX doughterboards is needed, which can go up to 1k eur (too expensive for a hobbist). I was wondering so, what is the best and the cheapest way to inject packets at the protocol stack on the phone and analyze some packet flow later with Wireshark - i.e. to get some usage of the OsmocomBB and to see how it works. At this point I can only run Hello World application, or "mobile" app without any usage (or I do not know how to use it). What would be the best way to start playing around without spending too much money. Speaking of this, what would be the price of the cheapest existing packet generator that can transmit them via Um (i.e. what is the price of the cheapest BTS)? Is there some open source FPGA that can be used for this purpose? Thanks for your explanations and best regards, Drasko