Co-Channel Interference is a classical problem in cellular systems that
has been studied extensively and several methods have been proposed to
overcome it. These include interference rejection techniques as well as
joint detection techniques. We have previously proposed a joint
detection technique for MSK-type signals that works quite well in
certain conditions. In this paper, we formally present what we call
Orthogonal MSK and postulate that if two MSK signals have a 90-degree
phase offset between them then both can be detected successfully
increasing the spectral efficiency two-fold. This technique works well
even if the two signals are near equal power and have the same carrier
frequency.