How will UE shift its codec from EVS to AMR and AMR to EVS?

Hi Experts.

One query related to VoLTE Huawei.

How will UE shift its codec from EVS to AMR and AMR to EVS?

Any parameter setting, condition or anything else?

VoLTE rate control feature helps in controlling the codecs between AMR only or EVS only?

Need to know the controlling factors of EVS to AMR and AMR to EVS codec shifting.

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The controlling factors should be the radio conditions.

When this feature is activated, the eNodeB monitors radio network conditions, and periodically sends optimal uplink physical bit rate to the UEs which support RAN-assisted codec adaptation specified in 3GPP Release 14.

In poor radio conditions, a lower bit rate is recommended, and if it is accepted by the UE, the lower codec rate results in fewer dropped packets through the call.

In good radio conditions higher codec rate is proposed, and the UE adapts to the recommendation, if this is supported.

Using higher bit rates improves speech quality.

Yes. That’s already understood that radio conditions are changing the codec, but asking the specific parameter or algorithm from which its happening in Huawei.

EVS to AMR and AMR to EVS.

Is it changing during the call or at the beginning only during codec negotiation?

There is a codec change in UL only in Huawei vendor.

Basically handsets connected on EVS codecs and they are not following the rate negotiation during call.

If any codec negotiated at the start of the call, UE will remain on same codec.

Even tough, EVS rate control complete feature implemented along with license, its not working.

But for AMR NB and WB its working fine.

Yes, how it will communicate to come down from EVS to AMR?

Main issue is that rate negotiation is not happening for EVS during the call and Call is not shifting from EVS to AMR codec.

Just wanted to know how can we check controlling parameter.

In my opinions codec is not possible to change during the call.

It is always negotiated at the start of the call.

Only rate recommendation is done through feature from RAN side and can be changed during the call but within the same codec.

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Its changes and UE measurement for codec changes at VoLTE as well and device also to support to up / down.

It allows to have HD VoLTE speech codec, and classified into EVS narrowband, EVS wideband, EVS superwideband, and EVS fullband. Either 5.9 or 13.2 or 16.4 kbps [Amr does 12.2 to 5.9]

Based on Radio condition, eNB transparent to signalling.

After all, it is EVS with just the rate changing? Is’n’t it?

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Yes, correct.

Conclusion is there is a codec change with in EVS rate and there may not be a codec change b/w EVS and AMR.Am I right?.

Within EVS Rate change happens in NR in 5GC take control. LTE has AMR to EVS or codec change also

there is other question if the UE(A) has EVS , and UE(B) doesn’t support the EVS or doesn’t agree for EVS negociation , what will be the situation?

Yes. Thinking of codec change from EVS to AMR is illogical as EVS is more robust compared to AMR under same radio conditions.

E2E volte calls are either on EVS or AMR. The type of codec is negotiated only once during call setup. This is done in two steps. In the first step the caller includes information about supported codecs in the SIP INVITE message. At the end of this message all supported codecs are enlisted. The callee selects one of the codecs and informs the caller about the chosen codec in a 183 SESSION PROGRESS message. So codec type is selected at this phase ensuring both UEs support the same codec.