  We performed a long-term optical (B, V, R bands), infra-red (J and K bands)
and radio band (15, 22, 37 GHz band) study on the flat spectrum radio quasar,
3C 454.3, using the data collected over a period of more than 8 years (MJD
54500--57500). The temporal variability, spectral properties and inter-waveband
correlations were studied by dividing the available data into smaller segments
with more regular sampling. This helped us constrain the size and the relative
locations of the emission regions for different wavebands. Spectral analysis of
the source revealed the interplay between the accretion disk and jet emission.
The source predominantly showed a redder-when-brighter trend, though we
observed a bluer-when-brighter trend at high flux levels which could be
signatures of particle acceleration and radiative cooling. Significant
correlations with near-zero lag were seen between various optical/infra-red
bands, indicating that these emission regions are co-spatial. Correlations with
a time lag of about 10--100 days are seen between optical/infra-red and radio
bands indicating these emissions arise from different regions. We also observe
the DCF peak lag change from year to year. We try to explain these differences
using a curved jet model where the different emission regions have different
viewing angles resulting in a frequency dependent Doppler factor. This variable
Doppler factor model explains the variability timescales and the variation in
DCF peak lag between the radio and optical emissions in different segments.
Lags of 6-180 days are seen between emissions in various radio bands,
indicating a core-shift effect
