Voice Over U M T S Evolution From W C D M A, H S P A To L T EPresentation Transcript
Song, Peng-Peng UTRAN system engineering Voice over UMTS evolution - from WCDMA, HSPA to LTE
AMR voice characteristics
Voice over UMTS evolution
R99 DCH scheme
CS Voice over HSPA+
VoIP over LTE
How fast, how big, how reliable
AMR Voice characteristics
Voice telephony service: modeled as a low, fixed rate data stream.
AMR_NB: an “adaptive”, “multi-rate” codec that is able to adapt to variable channel conditions .
AMR_WB (Optional) : significant improvement for clear sound and rich voice.
VoIP in cellular networks
VoIP in IMS domain (Rel-5)
encapsulated in RTP/UDP protocol
UTRAN serves VoIP with PS conversational RAB
header compression is a must for wireless transmission
mandatory UE support
23.85, 23.05, 19.85, 18.25, 15.85, 14.25, 12.85, 8.85, 6.6 AMR_WB multi rate (kbps) 12.2 (GSM-EFR), 10.2, 7.95, 7.4(IS-136), 6.7(PDC-EFR), 5..9, 5.15, 4.75, 1.8(SID) AMR_NB multi rate (kbps) A/D … …… voice samples compressed frame 20ms codec output voice frame RTP packet UDP packet VoIP packet UTRAN UMTS PS CN IMS application servers 40 bytes (AMR 12.2) Total voice payload on air interface 16 bits (CRC) 2 byte (RLC security) 4 byte (RTP/UDP/IP) 10 bit + padding (RTP-pre-header) protocol overhead with compressed header SID packet every 160ms during silence 15 bytes(5 bvtes + header) SID 50% voice activity factor 20 ms encoder frame length source rate 12.2kbps RTP AMR 12.2 codec Characterization Parameter
Voice over R99 DCH
Support UED/UEP (unequal bit error detection and protection) against prioritized codec output sub-flows
DCH DTCH DTCH DTCH DCCH DCCH DCCH DCCH DCH DCH DCH 3.4 kb/s DPDCH Class A bits Transport channels Physical channels Class B bits Class C bits RRC,AM NAS_DT, High prio, AM Logical channels NAS_DT, Low prio, AM RRC,UM DPCCH TFCI Transport Block Add CRC Add tailer bits Channel coding 2 nd interleaving Class A bits Class B bits Class C bits TB AMR 12.2k payload (SRB 3.4kb/s) DCCH CRC CRC 81 60 103 148 81 12 103 60 148 16 93 8 103 8 60 8 164 8 303 333 136 516 294 324 128 548 Rate matching 294 324 128 548 1 st interleaving Segmentation 1a 1b 2a 2b 3a 3b 4a 4b 4c 4d 1a 2a 3a 4a 147 147 162 162 64 64 137 137 137 137 1b 2b 3b 4b radio frame i radio frame i+1 1 2 15 510 510 CCTrCH level Phy Channel level … 1 2 15 … 6 34 510 + 90 6 34 … … … 510 + 90 Trans. ch multiplexing DPCCH DPDCH Transport Block level 1/3 Conv coding
Voice over R99 DCH
AMR control: adapts AMR Codec rate to varying radio channel conditions
Based on radio link power: further optimizes radio resource usage
Based on cell load: offers a trade-off between capacity and coverage & alleviates load congestion
6A/6B event NodeB RNC Measurement report MSC UE Tx power IuUP rate control process Transport Format Combination Control NBAP dedicated measurement process RB reconfig A complete solution accompanied by power control, dedicated measurement, adaptive rate control, soft handover while minimizing radio resource usage! cell load Transmitted code power
CS over HSPA
Standardized in R7 spec - driven by NSN and Qualcomm
To avoid surplus “SRNS relocation” signaling between “hierarchical RNC” and “flat RNC”
Benefit: no needs of IMS core network for voice packet over HSPA
- 23% capacity gain( with 2ms HSUPA TTI) over R99 voice user numbers per cell;
- with CPC, will have 48% capacity gains over R99.
A beginning for voice over “packetized” radio interface!
VoIP over LTE
LTE is purely PS-domain oriented - Can LTE support voice service?
Yes, in term of VoIP with IMS core
Otherwise use “CS fallback” or “SR-VCC” feature
VoLGA(Voice over LTE Generic Access) underway now
What is the difference between circuit-switched voice and packet-switched voice?
NAS Layer: Call control and switching functions already have been built into CS Core network elements but in PS domain, SIP/SDP protocols are in use.
AS Layer: header compression mandatory for VoIP
AS Layer: flexible UED/UEP on “DCH-based” radio interface but not for VoIP which is based on “shared” radio interface
TN Layer: bearers/interfaces need to support rigid QoS & differ-Serv management for PS traffic
VoIP over LTE
Downlink(OFDMA): dynamic scheduling (time+frequency domain) or semi-persistent scheduling
Uplink(DFTS-OFDM): semi-persistent scheduling
UE 1 resource block: 180 kHz = 12 subcarriers PDCCH PDSCH Packet-switched voice over “packetized” radio interface! VoIP packets via S1 interface Multiplexing per user scheduling RLC (Segmentation, ARQ) PDCP (Header Compression, Ciphering) HARQ OFDM Signal Generation coding data modulator resource mapping eNodeB Tx to RF module time frequency Reference symbol Control channel resource User A User B User C Idle resource for data
Performance – cell capacity in 5MHz
VoIP over LTE benefits from orthogonal uplink design,
intelligent scheduling, antenna diversity and link adaptation!
Performance – latency Control plane latency: User plane latency: “ single-node” RAN architecture; Optimized signaling procedures 50ms 250~350ms 400~550ms dormant->connected < 100ms ~460ms >500ms idle ->connected ~100ms 2~3s >5.5s voice call setup LTE_VoIP CS over HSPA R99 AMR C-Plane latency
Packetized radio interface can serve voice traffic pretty well when “QoS enablers” are built into each NE/interface.
Greater capacity by time/frequency diversity gain and multi-user diversity gain
Flexible channel bandwidth adjustment during one session
Rigid QoS and “diff-serv” management needed on each NE/interface
CS over HSPA: controversial with new link budget & planning reqts
VoIP over LTE: sounds good but when will IMS enter life?
Backup - comparison of radio parameters IMS core MSC+MGW MSC+MGW CN dependency Rel-8 UE as defined in TS 36.306 Rel-7 UE that can report “support for CS voice over HSPA” in “UE Radio Capability” IE N/A UE dependency available control channel resource(PUCCH/PDCCH bandwidth) UL interference-limited UL interference-limited, DL OVSF code limited potential capacity limitation UM UM TM RLC mode Yes(RFC3095) No No Header compression No No Y DL No Y Y UL support SHO or not N/A Y Y DL N/A Y Y UL rate adjustable by UTRAN 2x2/4x2 MIMO N/A N/A DL MU-MIMO, No Tx diversity N/A N/A UL Antenna diversity dynamic or semi-persistent scheduling Enhanced PF scheduling N/A DL semi-persistent scheduling Non-scheduled mode, rate controlled by RNC N/A UL NodeB scheduling Y in case of multi-RAB N/A DL Y N/A N/A UL link adaptation(AMC) Y Y N/A DL Y Y N/A UL HARQ 1/3 Turbo(QPP interleaver) 1/3 Turbo 1/3 Conv. DL 1/3 Turbo(QPP interleaver) 1/3 Turbo 1/3 Conv. UL channel coding 1ms 2ms 10ms DL 1ms 2ms or 10ms 10ms UL radio frame PDSCH(shared PHY channel) HS-DSCH(shared PHY channel) DCH DL PUSCH(shared PHY channel) E-DCH DCH UL radio channel LTE_VoIP CS over HSPA R99 voice