RE: [rohc] Liaison towards 3GPP

[khiem.le@nokia.com]

Hi,

There have been quite a few mails on this topic already, I just want to make
some quick comments.

Khiem Le, PhD
Nokia Research Center

-----Original Message-----
From: EXT Krister Svanbro [mailto:krister.svanbro@lu.erisoft.se]
Sent: Friday, April 07, 2000 6:42 AM
To: Casati, Alessio (Alessio)
Cc: rohc@cdt.luth.se
Subject: Re: [rohc] Liaison towards 3GPP



"Casati, Alessio (Alessio)" wrote:
> 
> > I have also seen these not yet concretized proposals for header
> > stripping and I don't think that they are a preferred way.
> >
> Tdoc 2-00-771 from Nokia (sorry for introducing company related
> things here, which I hate to do, but this is how SMG2 works) is a good
> document, although not yet finalized and approved, for instance.
> Also There are some merits in handling RTP play out at the RNC
> for R'99 CS backward compatibility.
> 
> > They violate
> > the end-to-end integrity of IP. To me it seems like these proposals aim
> > at "eating the cake and still try to keep it".
> >
> For the sake of truth, they don't violate IP integrity,
> but RTP integrity (not to mislead anybody, this is not WAP
> based ;).

Are you sure about this. If the IP ID is non-sequential as it commonly
is, I am pretty sure it will be stripped and reproduced without
preserving the original value. Hence, violation of IP integrity. 

KL: Obviously, header stripping does not guarantee header transparency. My
understanding is the driver behind header stripping is spectrum efficiency.
There is also the fluctuation in bandwidth demand caused by variable size
compressed headers which is eliminated. 

> 
> >  Furthermore, I seriously doubts that there is any large
> > gain in capacity having this kind of algorithms. The proposals I've seen
> > involves sending some header related information over the air-interface,
> > hence they will create some overhead. Since there are no actual detailed
> > proposals on header stripping (to my knowledge) it is not possible to
> > estimate the overhead, however, it is not unlike that it would be some
> > 0.x of a byte overhead in average per packet.
> >
> I would say that once the bearer is set up, maybe that X
> is very close to 0.

Radio bearer setup would include extra overhead for setting up the
stripping scheme, I think you should count these bytes as well.

KL: Counting these bytes will not make any difference to the overall average
overhead.

> 
> > Given the propsals for header compression in ROHC wg today, the
> > difference in efficiency will not be large. ROCCO for instance is
> > currently able to compress the header down to an average of appr. 1
> > byte.
> >
> 1 byte out of 20 is 5 %.

1 out of 30 something is probably more realistic, => 3 %.

> 
> Spectrum license B in UK auction is now valued around  $6 billions
> 5% is roughly valued $300 M even 30% of that is still $100 M.  That's
enough
> to start looking at the merits of header stripping.

3 % of bandwidth increase does not map linear to 3 % in terms of system
spectrum efficiency, especially not for TDMA systems such as EDGE. It
will 
probably be a smaller decrease in spectrum efficiency.

KL: On the other hand, you have to factor in the fact that compressed
headers will likely need a stronger error protection than the payload, which
results in a higher relative overhead percentage.

> 
> > I don't expect the final scheme to be any less efficient. Hence,
> > with header compression the efficiency will be only slightly smaller,
> > but you have the very desirable property of IP end to end.
> >
> when trading IP end to end for voice services and $300 M (or $100 M) a
> carrier may like the latter. This however does not mean we don't need
> the ROCH stuff. People just must be informed and be aware of the
> context they are working in (I assume not everybody here has visibility
> on everything, and I would like to be informed about what I can't see
> myself)

I fully agree.

/ Krister

 __________________________________________________________

 Krister Svanbro, M.Sc.  -  Ericsson Research 
 AWARE - Advanced Wireless Algorithm Research at Erisoft
 Box 920                 |   Tel.     : +46 920-20 20 77
 SE-971 28 Luleå         |   Fax      : +46 920-20 20 99
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          mailto:Krister.Svanbro@epl.ericsson.se
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