4 General

26.4543GPPCodec for Enhanced Voice Services (EVS)Interface to Iu, Uu, Nb and MbRelease 17TS

The Iu-Interface is defined in two different variants for speech telephony in CS networks:

a) for the ATM bearer with Iu-framing; and

b) for the IP bearer with Iu-framing.

The Nb-Interface is defined in three different variants for speech telephony:

a) for the ATM bearer with Nb-framing in a BICC-based Core Network,

b) for the IP bearer with Nb-framing in a BICC-based Core Network, and

c) for the IP bearer with RTP packing in a SIP-I-based Core Network.

The Mb-Interface is defined in one variant for speech telephony:

a) for the IP bearer with RTP packing.

The mapping of the EVS generic frame format (TS 26.453 [19]) to the Iu interface specifies the speech data exchange between the RNC and the Iu-terminating MGW in PDU Type 0 (see TS 25.415 [4]). This mapping is independent of the radio interface in the sense that it has the same structure for both Frequency Division Duplex and Time Division Duplex modes of UTRAN.

The EVS-CMR is transported on the Iu and Uu interfaces appended to the speech payload, transparent to the RNC. The RNC Rate Control commands (UL RC Proc), sent uplink to the Iu-terminating MGW for downlink rate control, are contained in PDU Type 14 messages (see TS 25.415 [4]). The Iu-terminating MGW combines the UL EVS-CMR, received in uplink from the UE, with the UL RNC Rate Control commands, received in uplink from the RNC. The present document describes the interworking.

The mapping of the EVS Speech Codec parameters to the Nb interface in a BICC-based Core Network specifies the speech data exchange between two MGWs in PDU Type 0. This mapping is very similar to the mapping on the Iu interface. However, PDU Type 14 is not used for Rate Control on Nb. The present document specifies the User Plane interworking between Iu and Nb.

The mapping into PDU Type 0 on the Nb Interface in a BICC-based Core Network is identical to the one on the Iu Interface. In case of Transcoder Free Operation, the MGW is relaying the Speech Data Units unaltered between Iu and Nb Interfaces. The EVS-CMR, contained in Iu and Nb frames, may be modified by the MGW.

The mapping of the EVS Speech Codec parameters to the Nb interface in a SIP-I-based Core Network is as specified in TS 26.445 [3], with some restrictions, as specified in the present document.

The mapping between the EVS Codec and the Radio Access Network within the UE is not an open interface and need not to be detailed. The present document specifies the interworking within the UE between EVS-CMR, Rate Control by the RNC and transmit-power-limitations.

For the 3GPP Codec Type UMTS_EVS the framing is 20 ms and also the packing time is 20 ms in all versions of the Iu and Nb-Interface. On the Mb interface, a different RTP packing may be applied.

The mapping of the EVS Speech Codec parameters to the Mb interface specifies the speech data exchange in RTP packets between the CS network and the IMS network. This mapping is specified in TS 26.445 [3]. TS 29.163 [5] specifies the User Plane interworking between Nb and Mb; the present document specifies further details.

The present document specifies also the Interworking within the MGWs on User Plane and the interworking in case of the EVS Channel Aware Mode.