  In \cite{Chandar2008}, Chandar et al studied a problem of sequential frame
synchronization for a frame transmitted randomly and uniformly among $A$ slots.
For a discrete memory-less channel (DMC), they showed that the frame length $N$
must scale as $e^{\alpha(Q)N}>A$ for the frame detection error to go to zero
asymptotically with $A$. $\alpha(Q)$ is the synchronization threshold and $Q$
is channel transition probability. We study the sequential frame
synchronisation problem for a fading channel and additive noise and seek to
characterise the effect of fading. For a discrete ON-OFF fading channel (with
ON probability $p$) and additive noise (with channel transition probabilities
$Q_n$), we characterise the synchronisation threshold of the composite channel
$\alpha(Q)$ and show that $\alpha(Q)\leq p\,\alpha(Q_n)$. We then characterize
the synchronization threshold for Rayleigh fading and AWGN channel as a
function of channel parameters. The asynchronous framework permits a trade-off
between sync frame length, $N$, and channel, $Q$, to support asynchronism. This
allows us to characterize the synchronization threshold with sync frame energy
instead of sync frame length.
