  We report on the long term monitoring of X-ray dips from the ultracompact
low-mass X-ray binary (LMXB) XB 1916-053. Roughly one-month interval
observations were carried out with the Rossi X-ray Timing Explorer (RXTE)
during 1996, during which the source varied between dim, hard states and more
luminous, soft states. The dip spectra and dip lightcurves were compared
against both the broadband luminosity and the derived mass accretion rate Mdot.
The dips spectra could be fitted by an absorbed blackbody plus cut-off power
law non-dip spectral model, with additional absorption ranging from 0 to >100 x
10^22 cm^-2. The amount of additional blackbody absorption was found to vary
with the source luminosity. Our results are consistent with an obscuration of
the inner disk region by a partially ionized outer disk. The size of the
corona, derived from the dip ingress times, was found to be ~10^9 cm. The
corona size did not correlate with the coronal temperature, but seemed to
increase when \Mdot also increased. We discuss our findings in the context of
an evaporated accretion disk corona model and an ADAF-type model.
