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Hi sheldon,prabeen
can u justexplain what is the difference between LA , IR and BLER mode.
Location Area
Incremental Redundancy
Block Erasure RateIt is like comparing apples, a thermonuclear explosion and my grand mother.
That sounds actually like the start of a good joke 🙂
Cheers
pixPix,
I think he is referring to Link Adaptation, not Location Area.
Safar,
Here is the difference:
With link adaptation, the whole data block is retransmitted with a new coding scheme if decoding of the first block fails. However, with IR, if the decoding of one block of data fails, ADDITIONAL CODING DATA is transmitted and soft-combined with the earlier data. This will continue until the data is successfully decoded.
BLER is one of the paramaters used to determine which coding scheme should be used to transmit the next block of data in LA/IR. If the BLER is high, a lower coding scheme is used and vice versa.
Regards,
SHELDONHi pix,
there is no need to explain full form here.actually discussion is abt fundamentals.
i think this sounds also good joke
Hi sheldon,
thanks for reply.ya right buddy we have here la\bler\ir mode for egprs.so here it always start with IR? is it?
and for gprs only LA is available? right sheldon?
then whats the meaning of regementation of retransmission?
Safar,
With your setting (LA/IR-BLER), they work simultaneously. Normally, an initial coding scheme (or MCS) is chosen for the first transmission. If the decoding of the data fails, then more coding data will be retransmitted (IR) using a lower coding scheme (LA).
I’m not sure if IR is also available for normal GPRS, I have to crosscheck.
Resegmentation and retransmission: When you’re transmitting data, the data is normally divided into smaller ‘pieces’. These pieces are then combined with some coding bits and transmitted as ‘blocks’ (data+coding bits). If you fail to decode a block, you have to retransmit the data with more coding bits. But more coding bits means you cannot transmit the same amount of data per block, thus the data has to be further subdivided. The subdividing is what is referred to as resegmentation, and the retransmission part should be obvious.
Hope you get the idea.
Regards,
SHELDONoh ok , link adaptation makes more sense than location area 🙂
sheldon : IR is not available for GPRS
IR is actually retransmitting the same piece of information, with the same coding scheme (MCS) but a different puncturing scheme (PS1, PS2 or PS3).
Some exception can be done within MCS of same family : retransmission of MCS9 block can be done over 2 MCS6 blocks with different puncturing schemes. That’s IR with LA. That is an exception though, which tends to confuse many people (me included ! 🙂 )safar,
i’m ok for discussing fundamentals 🙂
I really didn’t understand your first question. Now it is clear. I think that LA/IR/BLER is a “word” you see in Ericsson documents ? In alcatel we never use these acronyms next to each other…regards,
pixHi sheldon,pix
ok buddy right ir is not available in gprs .gprs only works with la
but buddy can u tell while in edge if my session is in ir and after ms soft memory is full then it will go in la. but is it possible to change mcs while session is in ir ?
and how we can judge the ms soft memory i mean how much?
pix – hey ok buddy no problem and thanks for reply.
safar,
yes, as i said, Retransmission using LA along with IR happens if radio quality is bad.
If radio qual is not that bad, the MCS is kept (no LA).
If radio qual is bad, then LA is used.
In both cases, IR is used if MS memory is not full.cheers
pixhi pix,
Thanks buddy here in logfile i saw when my ms out of memory soft capacity is full even though it remains in ir not going to la.
Hi sheldon,pix
plz share.
Safar,
How do you “see” that it’s IR that’s used and not LA? It seems impossible to use IR when the MS memory is not full. However, there’s still a fundamental question: Does the BSC know abt the memory status of the MS? Maybe Pix can help.
Pix,
Thanks for the info on IR.Regards,
SHELDONHi pix,
any idea abt this…
Hi, yes, the PCU (MFS) knows about the Memory Status of the MS. If memory is full, then the IR is not used.
I don’t know how you know whether the retransmission is using LA or IR in your traces… It is not explicitly stated…As long as radio quality doesn’t degrade, the retransmission is done on the same MCS. With IR or without IR, it is the same, in this case.
Did you check the MEAN BEP and CV BEP ? Is there a degradation when data are retransmitted ?
Pix
Hi pix,
i think we can check IR status in tems in egprs status but i check it again it is IR UL.so it is for uplink pix?
and buddy in my logfile ms out of memory messege comes and before that messege value of mean bep is 16 and cv bep is 4.
pix can u tell me how we can conclude that retransmission happen?
i mean so many PACKET UPLIN ACK/NACK MESSEGE WHICH IS DOWNLINK MESSEGE FROM PCU TO MS or
so many EGPRS PACKET DOWNLINK ACK/NACK MESSEGES form MS TO PCU IN UPLINK.
PLZ CLEAR THIS I HAVE CONFUSION ABT THIS
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