RE: [rohc] Implementation parameters and signals

[juha.kalliokulju@nokia.com]

Moi Micke,

> -----Original Message-----
> From: EXT Mikael Degermark [mailto:micke@cs.arizona.edu]
> Sent: 19. lokakuuta 2000 16:14
> To: juha.kalliokulju@nokia.com
> Cc: micke@optima.CS.Arizona.EDU; juha.kalliokulju@nokia.com;
> rohc@cdt.luth.se
> Subject: RE: [rohc] Implementation parameters and signals
> 
> 
> Hi Juha, 
> 
> At 11:12 AM 10/19/00 +0300, juha.kalliokulju@nokia.com wrote:
> 
> >> Hmmm. The current spec does not recognize this possibility. 
> >> But you are
> >> right that it wouldn't change things very much if the CIDs 
> >> were passed in 
> >> lower layers. This should be  easy to describe in a "ROHC 
> >> over PDCP" document.
> >> 
> >> The meaning of "small CIDs" would be to use the CID in the 
> >> lower layers.
> >> The meaning of "large CIDs" would be to add 1-2 CID bytes.
> >
> >-jk- I didn't quite get the idea. Do you mean that in the 
> case that link can
> >provide CID the "small CID" would indicate to utilise CID on 
> link layer and
> >"large CID" would indicate that ROHC would add the CID bits?
> 
> Yes, that is what I meant. I thought some more about this, 
> however, and
> it would probably be better to use those 5 bits as channel 
> identifiers. Using
> small CID space on each individual channel would be equally 
> efficient and 
> does not require any changes to anything in ROHC. The spec of 
> this could
> be done in the "ROHC over PDCP" document.
> 
-jk- Bits as channel identifiers? The actual channels in WCDMA are separated
by other identifiers so these 5 bits are not needed for that purpose. What I
originally tried to propose is that ROHC would provide compressed header +
associated CID (CID not part of the compressed header). By having such
possibility the logical layered architecture could be maintained (in 3GPP).
By having the CID separate as an output from ROHC we would be able to get
rid of 1 octect overhead in ROHC (in case CID can be provided by link) and
be able to feed in several flows to ROHC but get them out as separate. I try
to illustrate it in the figure below.

-------------------------------------------------
PDCP                |   n flows into ROHC
                    V
          -------------------------
          | ROHC                  |
          |                       |
          -------------------------
            |     |      |      |       1. Flow 1 'logical CID' 0
            v     v      v      v       2. Flow 2 'logical CID' 1
            1.    2.     3.     4.      3. Flow 3 'logical CID' 2
                                        4. Flow n 'logical CID' n-1

            Put compressed headers (+payload)
            to PDCP PDU and copy 'logical CID'
            to PDCP header (those 5 bits)

                      |
                      | all flows travel over same radio bearer
                      v
---------------------------------------------------
RLC

Any clearer or did I misunderstood something in first place?

-jk-

> >> >---
> >> >Mailing list for Robust Header Compression WG
> >> >Archive: http://www.cdt.luth.se/rohc/
> >> > 
> >> 
> > 
>