Voice in 4G: CSFB, VoIP & VoLTE
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Transcript of Voice in 4G: CSFB, VoIP & VoLTE
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Voice in 4G: CSFB, VoIP & VoLTE
@3g4gUK
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Did you hear this joke about 4G?
Now lets get back to the serious discussions
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IMT-Advanced and 4G Technologies
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Different paths to 4G
4G LTE / LTE-A
(FDD – TDD)
3GPP 3GPP2
1xEV-DO: Enhanced Voice-Data Optimized CDMA ONE: Code Division Multiple Access One EDGE: Enhanced Data rates for GSM Evolution eHRPD: Enhanced High Rate Packet Data GPRS: General Packet Radio Service GSM: Global System for Mobile Communications HSPA: High Speed Packet Access HSPA+: High Speed Packet Access Plus OFDMA: Orthogonal Frequency Division Multiple Access SCDMA: Synchronous CDMA TD: Time Division TD-SOFDMA TD Scalable OFDMA UMTS: Universal Mobile Telecommunication System
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The ‘4G’ LTE Network Architecture
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BSC
BTS
MSC
Voice (PSTN) Network
SGSN
Data (IP) Network
RNC
Node B eNodeB
MME
GGSN
Access Network
Core Network
Air Interface
MS UE UE
BSS RNS
S-GW
P-GW
2G 2.5G
3G 4G
EPC
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Circuit Switched Fallback (CSFB)
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LTE
2G/3G UE
CSFB
• CSFB has been designed as an interim solution until the LTE networks are rolled out completely.
• In case of CSFB, the UE falls back to 2G/3G network when a voice call / SMS needs to be initiated / sent or received.
• Since the UE has just one receiver, the data rates after CSFB would be the data rates offered by the 2G/3G network.
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CSFB Approaches
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• Redirection: When UE starts a call in Idle (RRC_IDLE) state
• Handover: When the UE already has an active data connection (in
RRC_Connected state). The active data connection is handed over to 2G/3G network
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SVLTE (Simultaneous Voice and LTE)
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• Also known as Dual Radio Concept
• Separate registration takes place for the CDMA/EV-DO and LTE networks
• Each network need not be aware of what the UE is doing with the other one.
• Since Voice and Data are independent one of them does not impact the other one.
LTE
CDMA/EV-DO
• CDMA/EV-DO registration • Paging for Voice call • MO/MT Voice call
• LTE registration • Paging for Data call • Data call
UE
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SGLTE (Simultaneous GSM and LTE)
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• Same as SVLTE but for GSM Network
LTE
2G – GSM
• 2G registration • Paging for Voice call • MO/MT Voice call
• LTE registration • Paging for Data call • Data call
UE
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SRLTE (Single Radio LTE)
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• Similar to SVLTE but Single Radio • Only Apple implemented it in
iPhone • Separate registration takes place
for the 2G/3G and LTE networks • Each network is not aware of
what the UE is doing with the other one.
• Only Voice or Data can be done at any time, not both.
• UE scans paging channel regularly making it inefficient
LTE
CDMA/EV-DO
• CDMA/EV-DO registration • Paging for Voice call • MO/MT Voice call
• LTE registration • Paging for Data call • Data call
UE
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SxLTE was strongly discouraged
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• Devices were more expensive because of dual radios
• Higher Power Consumption
• Does not allow legacy networks to be switched off
• Can have competitive disadvantage
2G
WiMAX
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©3G4G
UE
eNB
S-GW
P-GW
Peer Entity
Radio S1 S5 / S8 Gi
E-UTRAN EPC Internet
End-to-End Service
EPS Bearer External Bearer
E-RAB S5/S8 Bearer
S1 Bearer Radio Bearer
Type Error Rate Delay Priority QCI Examples
1
GBR
10-2 100 ms 2 Conversational voice
2 10-3 150 ms 4 Conversational video
3 10-3 50 ms 3 Real-time games
4 10-6 300 ms 5 Streaming video
5
Non – GBR
10-6 100 ms 1 IMS Signalling
6 10-6 300 ms 6 Steaming video, web, email
7 10-3 100 ms 7 Voice, video, games
8 – 9 10-6 300 ms 8 – 9 Streaming video, web, email
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Voice over IP (VoIP)
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• Voice goes as data, the same way as any other IP data.
Default Bearer
eNB
Internet
UE
APN1
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Over The Top (OTT) Apps
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Why have 4G Voice?
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• Better for MNO’s with no legacy Infrastructure
• Re-farm Spectrum
• Better Voice Quality
• Faster Data Rates while voice calling – other services are not impacted
• Simpler operation
• Better Battery Life
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Voice over LTE (VoLTE)
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• Voice is independent of Data and is carried by different bearer • An additional signalling and data bearer is used for VoLTE
VoLTE bearer
Default Bearer eNB
Internet
UE
APN1
APN2
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Question: Can Voice work Independently of Data?
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VoLTE bearer
Default Bearer eNB
Internet
UE
APN1
APN2
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Handing over from LTE to 2G/3G
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VoLTE to VoHSPA Handover
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• HSPA call is controlled by IMS Core
E-UTRAN
UTRAN
IMS Call
IMS Call
Telephony server
Rich Communication
Suites
SMS server
MGW
IMS CORE
VoHSPA Handover
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Single Radio Voice Call Continuity (SRVCC)
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• The Voice call continues on CS Core
E-UTRAN
UTRAN GERAN
IMS Client
UE
Telephony server
Rich Communication
Suites
SMS server
MGW
IMS CORE
SRVCC – PS to CS
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Voice path before and after SRVCC
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UE
E-UTRAN
UTRAN GERAN
HSS
S-GW P-GW
MSC
MME
SGSN
SV
S3
UE
E-UTRAN
UTRAN GERAN
HSS
MSC
SV
MME
SGSN
S3
SRV
CC
P
S to
CS
S-GW P-GW
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Voice path before and after SRVCC
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UE
E-UTRAN
UTRAN GERAN
HSS
S-GW P-GW
MSC
MME
SGSN
SV
S3
UE
E-UTRAN
UTRAN GERAN
HSS
MSC
SV
MME
SGSN
S3
SRV
CC
P
S to
CS
S-GW P-GW
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Thank You
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