8-PSK modulation/demodulation

Hi all, I'm developing gr-gsm - the ancestor of Airprobe's gsm-receiver. I want to add support for 8-PSK reception. I'm going to implement a demodulator (preferably doing also channel equalization) and also modulator (currently mostly to generate test data). I don't want to duplicate work that was already done so I want to ask if you are aware of any publicly available 8-PSK implementations (or partial implementations) aimed at supporting EDGE reception? Also I will greatly appreciate pointing to any documents containing good information on this topic. -- Best Regards, Piotr Krysik