If you need higher bitrates, implementing header and payload compression at the SNDCP level in the SGSN is possible.

Also, always keep in mind that while you can offer 7 TS with GPRS/EDGE, almost no phone has support for a multislot class that allows for 7 TS in DL. So multiple phones can fill the 7 TS, but it's unlikely one phone can use all of them.

Regards, Harald