VoLTE as the Technology of Choice for LTE Voice Transmission and SMS
GSM Association IR.92 specifications highlight specific standards to deliver voice and SMS services over an LTE network with IMS (IP Multimedia Sub-systems). WiFi as an “offload” is also an interesting concepts for many operators. VoLTE is essentially VoIP over 4G/LTE using IMS architecture.
In order for LTE UE to establish a voice call over IMS, the following steps are essential:
- UE RRC Connection Request to EPC & IMS
- PDN Connectivity Request
- Protocol Configuration Options IE
- P-CSCF address
- EPS Attach & P-CSCF Discovery
- UE initial IMS registration
KEY TECHNICAL REQUIREMENTS FOR VoLTE ARE:
- PCC rule authorization and QoS rule generation
- Multiple Bearers (Default, Dedicated)
- QoS Class Identifiers (QCIs)
- Semi-Persistent Scheduling
- Transmission Time Interval (TTI) Bundling
- Discontinuous Reception (DRX)
- Robust Header Compression (RoHC)
COMMON RTP PAYLOAD TYPES FOR VOLTE ARE:
- Audio AMR 8000
- Audio AMR-WB 16000
- Text T140 1000
- Video H.263 90000
- Audio EVRCB 8000
- Audio EVRCWB
- Video H.263-2000 90000
- Video H.263-2000 90000
- Video H.264
- Video MP4V-ES 90000
Great Post Charles. What are the differences between SRVCC and CSFB?
ReplyDeleteCircuit Switched Fall Back (CSFB) and LTE VoIP-based Single Radio Voice Call Continuity (SRVCC) are different. CSFB by 3GPP is a solution that requires terminals be equipped with either dual-mode/single-standby or dual-mode/dual-standby capabilities. With CSFB there is no need for IMS.
ReplyDeleteSRVCC offers LTE-IMS based voice service within the LTE coverage area, and CS-based voice service outside the LTE coverage area. SRVCC service for LTE comes into the picture when a single radio User Equipment (UE) accessing IMS-anchored voice call services switches from the LTE network to the Circuit Switched domain.
in SRVCC, within LTE coverage voice call is initiated from
LTE/EPC via IMS, which controls and anchors
the voice call. When the UE leaves the coverage of LTE, IMS
will transfer the ongoing call to CS network.
I hope this helps.