Subject: [rohc] Some reflections on the notation discussions in Yokohama

From: "Lars-Erik Jonsson (EAB)" <[email-masked]>
Date: Fri, 2 Aug 2002 12:34:17 +0200

Hi all,

At the Yokohama meeting, we seemed to have some disagreements whether
we should have a unified or modulated approach with the notation. I was
in favor of the latter, but afterwards I started to wonder whether we 
really had that different opinions. Maybe I was not really clear with
what I meant, especially not considering the material we had on the 
table with two different notation documents. I do think we should have
one uniform notation, and this is where I think there might have been
some misunderstanding. However, I think it is important to build that
notation in such a way that it can be applied in several steps, i.e.
the input side is a mapping from the original header while the output
only covers what is needed for the bits-on-the-wire-encoding.

Another thing that I think has caused some confusion is what we mean
when we say encoding. There are two kind of encodings involved in
this and we should try to come up with a terminology that clearly
shows the difference. We have agreed that the final encoding of the
compressed header bits is not part of the notation work, but the
notation obviously do include lots of encoding stuff. The notation
defines various encoding methods on a per-field level, and this is
the core content of the notation. As an example, LSB encoding could
be applied to an original header field, and the notation provides
formal ways of describing the encoding. What is not part of the
notation is how to take all encoded fields and turn these into a
bitstring for transmission as an identifiable compressed header over
the wire. That could be done in many ways, with certain intelligent
encoding methods or by hand, and each new notation-based profile
would have to choose which such encoding to use and with that produce
the actual compressed header formats. 

Cheers,
/L-E

-----------------------------------
Lars-Erik Jonsson, M.Sc
Wireless IP Optimizations
AWARE - Advanced Wireless Algorithm Research and Experiments
Ericsson Research, Corporate Unit
Ericsson AB
Box 920, S-971 28 Luleå, Sweden
E-mail: [email-masked]
Phone: +46 920 20 21 07
Fax: +46 920 20 20 99
Home: +46 920 999 57

My opinions are my personal opinions and should not be considered
as the opinions of my employer, if not explicitly stated. 

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