Hi Kandavelan,
I would like to see the scene file (please reduced to the parts that causes it, or on which the banding is visible)
Banding is normally a result of a low bit/c format or a over corrected material. In short 8 bit/c are the typical reason for banding. As this is a data-image which is only based on gray (B&W) values, you get only 256 values in it with 8bit/c
As every data image it should have no change of the data enabled. AntiAlias for example is a big no for those channels. Like yesterday in CV-Live, the UVW channel is a data channel, which means RGB are just numbers. If one uses dithering or Anti Alias in render or post, these values are destroyed. Heavy compression is as well something to avoid on all cost. Any loss based on compression is the dead of these data types.
I work in nothing else than 32bit/c and of course linear, to avoid all of these problems. With OpenEXR the file size is not that larger (With tiff it is dramatically larger of course)
If floating point 32bit/c is not helping at all the reason must be in the scene file.
All the best
Sassi
P.S. Radiance (.hdr) is not a 32/bit/c (channel) file it is a 32bit/p (pixel) format. Do not use it if you like to have quality.