Subject: any thought to doing similar with broadcast FM radio SCA?

From: Michael L Kornegay <[email-masked]>
Date: Tue, 15 Jun 1999 12:44:21 -0400

Hello, 

I am not on the mail list so please include me in CC.  

I have been watching the work you have been doing on this draft
with interest.  

I was wondering if anyone has considered doing something similar
for FM broadcast radio SCA?  

Though the following may not be entirely correct, for those that 
are unfamiliar with SCA it is a hidden channel in an FM broadcast
channel that is often used for the subscription based "elevator"
music often heard in business.  I also believe that there are 
many data uses of SCA but are unfamiliar with them.  Seems like
IP/SCA, like IP/VBI, would be an interesting implementation.  

As an aside, I was wondering if anyone is currently deploying
IP over VBI to devices other than PCs?  Seems like this would 
be an interesting transport to consider for traffic/news/weather
data that might be broadcast to wireless PDAs and other devices.  

Thanks for any comments,
mlk

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From: Grenville Armitage <[email-masked]>
Date: Wed, 16 Jun 1999 15:45:38 -0400

Michael L Kornegay wrote:
	[..]
> I was disappointed that there did not appear to be an archive of your mail
> list.

And now for something completely different, the lack of archive means
I have to ask this question out loud :-)

In the current spec it is assumed that SLIP is the framing mechanism
of preference. I was wondering what the trade-offs were relative to
PPP? The motivation for my question is a related issue of QoS over
an IP-VBI channel - the PPP group have a couple of extensions
(MCML and RTF) for interleaving large and small packets on low speed
links. I'm not sure enough about the target environments for VBI
to know if this is irrelevant or just not covered yet (ignorance due
to the aforementioned absent archive ;)  But if interleave jitter
is going to be a consideration, the more compressed forms of
PPP framing might be a better track to head down....

cheers,
gja
________________________________________________________________________
Grenville Armitage                            http://mh005.infi.net/~gja
Bell Labs, Lucent Technologies

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From: Michael L Kornegay <[email-masked]>
Date: Wed, 16 Jun 1999 15:29:40 -0400

Dave, 

Thanks for your comments.  

Dave Rayers wrote:

Your comments about IP/VBI for mobile devices are appreciated.  I really 
did not think about the reception problems that might be encountered by
a mobile device receiving television signals.  

> I don't know about FM radio SCA. We don't have it here, at least its not
> called this.

Is your DAB or RDS a channel all its own, or do they utilize portions of 
an existing channel like VBI and SCA?  They might be like it but are just
called something else.  Maybe SCA is US centric but I would think that 
similar things are being done elsewhere.  

I will probably say this wrong but, SCA stands for Sub Carrier Authorization
and is allowed in the US in FM radio broadcast channels.  It uses a portion
of an existing channel that is the primary program where it's portion is 
generally not accessible to the public without a special decoder (much like
VBI).  I dont know enough about SCA to know what kind of bandwidth there is
and what kind of data rate could be achieved on such a portion of a normal
FM radio broadcast channel.  I just thought the idea was an interesting one
from the perspective of mobile devices, and the currently expensive wireless
network communications possibilities.  And if it looked promising, that 
work like that of IP/VBI might provide ideas on how to apply similar 
techniques to FM radio broadcast SCA.  

You did not comment on the current or anticipated deployment of IP/VBI?  
Is this just being implemented in things like WebTV and PC based TV tuners?
Other areas?  

Thanks,
mlk