  It is widely believed that the low frequency quasi-periodic X-ray
oscillations observed in microquasars are correlated to, but do not originate
at, the physical radius of the inner edge of the accretion disk. Models
relating the QPO frequency and color radius are hindered by observations
showing contradicting trend correlations between the microquasars GRO 1655-40,
XTE J1550-564 and GRS 1915+105. The first shows a negative correlation and the
latter two a positive one. By taking into account relativistic rotation in the
accretion disk, the Accretion-Ejection Instability (AEI) model predicts a
turnover in the frequency-radius relationship, and has been successfully
compared with observations of GRO J1655-40 and GRS 1915+105. We present further
evidence supporting the AEI model prediction by using observations of the
microquasar GRS 1915+105. By combining a data set including $\theta$-, $\beta$-
and $\alpha$-class X-ray light curves, we observe positive, negative and null
correlations in the frequency-radius relationship. This is the first time a
single source has shown a possible inversion in the QPO frequency-color radius
curve predicted by the AEI model.
