Re: DAB Receivers compatibility vs MOT

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1 total messages Started by Ted Ledingham Thu, 17 Dec 1998 00:00

#224

Author: Ted Ledingham
Date: Thu, 17 Dec 1998 00:00

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Date: 17 December 1998
From: matthias@radio.kth.se
Subject: Re: DAB Receivers compatibility vs MOT

Re: Francois O. Gauthier, Synchronization of DAB Data Services
    [RADIO-L, 16 December 1998]

In MOT, synchronization is done by inserting time stamps in the data
stream. Both time and date are coded according to UTC/MJD, just like
in FIG 0/10 in ETS 300401, which allows time accuracy way below
seconds. Provided the PAD inserter is properly implemented and its
time is accurately set, it then only depends on the PAD/MOT decoder in
the receiver, how sound and data are aligned. Delay could be introduced
by:

- timer polling intervals, i.e. how frequent is the time stamp list
updated and checked

- decoding speed (which might be considerable for e.g. JPEG pictures)

Since no ARQ can be used, one can of course not guarantee that a
sequence of time stamps might not be lost due to e.g. a fading dip. In
that case the according data items are simply not displayed, but the
MOT decoder does not get "out of pace", because all data items are
linked with the time stamps by a unique identifier.

Synchronization with an accuracy of approx. 1 sec. can be achieved,
provided the equipment is operated properly. Many demonstrations during
the recent years have shown this.

Best regards,
Matthias Unbehaun.
_______________________________________
Matthias Unbehaun
Royal Institute of Technology Stockholm
Radio Communication Systems Group

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