Half Rate

[justdream]

Experts,
can you give me small explanations about Half Rate?
and the difference between it and full Rate?

[xcatas]

half rate is a gsm speech codec operates at 5.6 kbps
it can double the network capacity with compensation reducing the audio quality.

full rate's bit rate is 13 kbps.
so we need to have optimal configuration between half rate and full rate.
if not configured correctly, maybe many user will have dropped calls..etc..

cmiiw

[justdream]

half rate is a gsm speech codec operates at 5.6 kbps
it can double the network capacity with compensation reducing the audio quality.

full rate's bit rate is 13 kbps.
so we need to have optimal configuration between half rate and full rate.
if not configured correctly, maybe many user will have dropped calls..etc..

cmiiw

Do you have documents explaining how to use Half rate and Full rate in a smart way.. (I mean how to plan using them together!!)

[danikd]

Do you have documents explaining how to use Half rate and Full rate in a smart way.. (I mean how to plan using them together!!)

For better understanding about GSM HR vocoder, please refer to the attached presentation. This presentation explains some theory for HR codec.

If you need more stuff related to implementation in air-interface, let me know.

BR

[s52d]

Hi!

While FR call needs one Time Slot, you can put two HR call in the same cell capacity.
TS is shared by alternating two calls on even/odd burst.
Good: more capacity in the cell, with same nr of TS/TRX
bad: low quality. Especially in noisy environment (both on voice and radio).
Joke: With handsfree, FR takes your voice out and keeps surrounding noise.
Radio: as 20 ms of speech is spread over 4 bursts, one lost burst means 40 ms is lost.
Observe Frame Erasure Ratio!

Most operators support HR-AMR on top of HR: it makes much better quality.
Problem with lost burst remains.

Some terminals do not support HR any more (just HR-AMR), some older support only HR.

Allocation policy:
- design network for FR/EFR/AMR
- use HR-AMR only for overflow traffic (unplanned peaks)
- use HR as backup for HR-AMR
On certain cell: start HR when allocating last available TS.
There might be some congestion, but you maximize FR usage.

BR
Iztok

[danikd]

Hi!

While FR call needs one Time Slot, you can put two HR call in the same cell capacity.
TS is shared by alternating two calls on even/odd burst.
Good: more capacity in the cell, with same nr of TS/TRX
bad: low quality. Especially in noisy environment (both on voice and radio).
Joke: With handsfree, FR takes your voice out and keeps surrounding noise.
Radio: as 20 ms of speech is spread over 4 bursts, one lost burst means 40 ms is lost.
Observe Frame Erasure Ratio!

Most operators support HR-AMR on top of HR: it makes much better quality.
Problem with lost burst remains.

Some terminals do not support HR any more (just HR-AMR), some older support only HR.

Allocation policy:
- design network for FR/EFR/AMR
- use HR-AMR only for overflow traffic (unplanned peaks)
- use HR as backup for HR-AMR
On certain cell: start HR when allocating last available TS.
There might be some congestion, but you maximize FR usage.

BR
Iztok

Iztok??? How you doing man?!!!! Welcome to the club!!!!!!!

[ludali]

Hi,

Note that it is also possible to convert on-going FR calls into HR calls.

This requires the tuning of some special features and the trigger comes about at predefined thresholds.

For E******* BSS, the feature "DYMA - Dynamic FR/HR Mode Adaptation" and its associated parameters make the process possible.

[coursekec]

very good explanation...i have one question though..if full rate's bit rate is 13 kbps then why is the bit rate of half rate not 6.5 kbps but 5.6 kbps ?

[plannerguy]

Hi small doubts


1)Does any one have a calculation for a half rate ...ie if full rate supports 2.9 Erl fro 1 TRx ,with half rate how much will we get?


2)will dynamically changing from full rate to half rate based on threshold, suppose if there is already a call in full rate will it get switched to half rate after half rate activation or will stay in full rate untill the call ends?


Regards
Plannerguy

[s52d]

Hi!

Reagrding kbit/sec in different codings:

20 ms of FR voice: 8 times 57 bits.
20 ms of HR voice: 4 times 57 bits.

There is channel coding on top of plain data.
In short, different voice coding have different forward-error-correction mechanisms.