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Voice in 4G: CSFB, VoIP & VoLTE

A look at different approaches to voice in 4G LTE Mobile Cellular Technology.

Voice in 4G: CSFB, VoIP & VoLTE

  1. 1. Voice in 4G: CSFB, VoIP & VoLTE @3g4gUK
  2. 2. Did you hear this joke about 4G? Now lets get back to the serious discussions ©3G4G
  3. 3. ©3G4G IMT-Advanced and 4G Technologies
  4. 4. ©3G4G 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
  5. 5. The ‘4G’ LTE Network Architecture ©3G4G BSC BTS MSC Voice (PSTN) Network SGSN Data (IP) Network RNC Node BeNodeB MME GGSN Access Network Core Network Air Interface MSUEUE BSSRNS S-GW P-GW 2G 2.5G 3G 4G EPC
  6. 6. Circuit Switched Fallback (CSFB) ©3G4G 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.
  7. 7. CSFB Approaches ©3G4G • 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
  8. 8. SVLTE (Simultaneous Voice and LTE) ©3G4G • 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
  9. 9. SGLTE (Simultaneous GSM and LTE) ©3G4G • 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
  10. 10. SRLTE (Single Radio LTE) ©3G4G • 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
  11. 11. SxLTE was strongly discouraged ©3G4G • 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
  12. 12. ©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 BearerRadio Bearer Type Error Rate Delay PriorityQCI 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
  13. 13. Voice over IP (VoIP) ©3G4G • Voice goes as data, the same way as any other IP data. Default Bearer eNB Internet UE APN1
  14. 14. Over The Top (OTT) Apps ©3G4G
  15. 15. Why have 4G Voice? ©3G4G • 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
  16. 16. Voice over LTE (VoLTE) ©3G4G • 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
  17. 17. Question: Can Voice work Independently of Data? ©3G4G VoLTE bearer Default Bearer eNB Internet UE APN1 APN2
  18. 18. Handing over from LTE to 2G/3G ©3G4G
  19. 19. VoLTE to VoHSPA Handover ©3G4G • 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
  20. 20. Single Radio Voice Call Continuity (SRVCC) ©3G4G • 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
  21. 21. Voice path before and after SRVCC ©3G4G 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 SRVCC PStoCS S-GW P-GW
  22. 22. Voice path before and after SRVCC ©3G4G 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 SRVCC PStoCS S-GW P-GW
  23. 23. Thank You To learn more, visit: 3G4G Website – http://www.3g4g.co.uk/ 3G4G Blog – http://blog.3g4g.co.uk/ 3G4G Small Cells Blog – http://smallcells.3g4g.co.uk/ Follow us on Twitter: https://twitter.com/3g4gUK Follow us on Linkedin: https://www.linkedin.com/company/3g4g ©3G4G

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A look at different approaches to voice in 4G LTE Mobile Cellular Technology.

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