Difference between AFR and CFR

[islam wagih]

Dears,
please i want to know the difference between AFR and CFR.

[Optimustron]

Did you mean AFR & EFR?, if yes, both codecs work at 12.2 kbps, however AFR is stronger in bad quality conditions because it changes its rate to lower but with more FEC and EFR not it remains equal. AFR is AMR FR and EFR is Enhanced FR and was developed before than AMR codecs, you have too AHR this is AMR HR. The main differences are the adaptation of AMR to different C/I situations and it is successful standard because it is used in GSM, UMTS, WIRELINE and there are new versions like AMR WB instead EFR only was used almost at the begining of GSM and remains in that system but isn't on UMTS or in other places.

I hope this can help if not I don't know of a new codec or set of codecs different I said before. Best regards friend,

[Optimustron]

I found in Internet that exist VFR & CFR, but this is for video and means VARIABLE FRAME RATE & CONSTANT FRAME RATE that is measured in fps or FRAMES PER SECOND, that is not related to directly to CODECS that is COmpression & DECompression, in video they use that techniques along with video CODECS like MPEG-1, MPEG-2, MPEG-4, WMV, SORENSON 3, SORENSON SPARK, REAL VIDEO, etc. I think that any one mention it and mix the codecs for video and audio, maybe the cause of mix AFR & CFR.

There are another concepts associated to this, VBR & CBR, those it mean VARIABLE BIT RATE & CONSTANT BIT RATE that is used almost in the same way that is used AMR in the case of VBR and for EFR, FR & HR in the case of CBR.

I hope this can be useful, best regards friend,

[islam wagih]

I mean Call Failure rate and Access Failure rate

[Optimustron]

Ok, that is clear and about that and in that case I can only guess about what I understand, and maybe help you with that. Access is the first stage in a call when you are trying to access the system, for example in the random access, signalling access and traffic channel access each of one are different stages of a call and failures that can happened at this points, call is a more longer process that include reaching the other side/part.

On the other hand, from the definition of call failure in the CORE side, you can ask them and you will find that they have some causes like:

Cause Table

Number	Cause
1	Unallocated (unassigned) number
2	No Route to specified transit network
3	No Route to destination
4	Vacant Area Code or Central Office Code
6	Channel unacceptable
7	Call awarded and being delivered in an established channel
8	Prefix 0 dialed but not allowed
9	Prefix 1 dialed but not allowed
10	Prefix 1 not dialed but required
11	More digits received than allowed, call is proceeding
16	Normal call clearing
17	User busy
18	No user responding
19	No answer from user (user alerted)
21	Call rejected
22	Number changed There are more reasons but I stop the list here because is so long.

Then the call failure must be after access a signalling channel and access traffic channel, specifically after you get a that traffic channel, this is the point when DROP CALL happens but in this case the release is because of another causes different to BAD QUALITY, SUDDENLY LOST CONNECTIONS, LOW SIGNAL, EXCESSIVE TIMING ADVANCE for example, maybe to after your call pass TRANSCODER ASSIGNMENT.

However you need to define very well the point of measurement and have a clear difference specially with DROP CALL. From my point of view maybe is to establish separation causes because of network elements, i.e., radio network access failures and in the other hand flaws that prevent reaching the final destination in the CORE network.

I hope this can help you, best regards friend,

[qaqa]

Hi Islam,

this will depends on the operator who has defined them. The following is how I interpret them:

1- AFR: this looks at customer's access to the network. in general access will be tow stages 1-RRC access than 2-RAB access. The two should happen so that the customer could successfully access the network. now if you are talking PS in UMTS you need to think also about the state transitions as as a kind of network access.

2- CFR: call failure rate should be a composite KPI that combines both AFR and Drop Call Rate DCR. why? because from customer's point of view a call is failed if a call did not go through or the call has dropped. so this KPI is a superimposition (a plus).

hope this help.