How does cc1100e work on the mode without preamble/syncword detection?

When you enter RX, the AGC needs a finite time to do gain adjustment and the data slicer needs bit transitions to set the slicing level. A preamble is thus needed prior to the data payload. A SOF or sync word is also needed to find where the packet starts (and do byte sync). 

It is possible to disable the automatic preamble/sync word detection, but then the preamble/sync word detection needs to be handled by the interfacing MCU. The recommendation is to use the on-chip preamble/sync word detection unless you have a good reason not to (e.g. an old legacy system which does not support the 2 or 4 byte sync word option in CC1100E)

Thanks for your reply.

I want to improve the sensitivity of cc1100e. I have done some coding in payload, and if with the correct sync, the sensitivity will be improved.  However, packets lose when attenuation increase. I want to try the mode without preamble and sync word, and I have no idea wether there have some solutions to this mode or it  is just a mode without meaning.