GSM-850

Hello, I don't know if anyone has already successfully used OsmocomBB with GSM-850. It seems that although receiving on GSM-850 works, there are issues when transmitting. The phone produces a signal on the correct ARFCN, however the BTS can't make use of it. The problem seems to be "I/Q-swap", something which can be turned on in the DSP independently for receiving and transmitting. So far it seems that this was not needed, at least for receiving and also for tranmitting when using GSM-900/1800/1900. However for GSM-850 it seems to be essential for transmitting. It is not clear if different phones behave differently, this might be the case. Also it might be the case that some phones require to turn on "I/Q-swap" when receiving on certain bands. Considering all those uncertainties of "I/Q-swap" the appended patch should be considered as a suggestion, it might be neccessary to make it dependend on the phone and also to introduce a similar function for receiving. At least with the patch a C122 GSM-850/1900 phone now works on GSM-850 too. Thank you very much to Harald who remembered that there was this "I/Q-swap" thing for the DSP. Best regards, Dieter Dieter Spaar, Germany spaar(a)mirider.augusta.de