Frequency Synchronization in OFDM -- a Bayesian Analysis.
IEEE 61st Vehicular Technology Conference
, Stockholm, Sweden, May 30-June 1, 2005.
The Bayesian approach offers three key advantages in the present
problem of estimating the frequency offset when synchronizing
a mobile to a base station in an orthogonal frequency division
multiplexing system: a systematic way to include important
information via prior probabilities; ability to update our probability
distributions consistently using Bayes theorem; access to reliability
measures for the actual estimate at hand.
We show that the
Bayesian approach in these ways enables fast frequency
acquisition without pilots at low SNR, and also provides a good
indicator of when the mobile is sufficiently synchronized to
transmit for the first time.
Our analysis and simulations indicate
that oversampling and nulling of subcarriers can speed up the
acquisition further. When pilot and (incomplete) channel
information is available, it can be successfully included via
priors to significantly improve the synchronization performance.
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