8 the path to voice over lte - vo lte

1. Greater insight. Greater confidence. Accelerate next-generation wireless. The Path to Voice over LTE - VoLTE with IMS (IP Multimedia Subsystem) presented by Andjela Ilic-Savoia Agilent Technologies Wireless Communications © 2012 Agilent Technologies 2013 1

2. Agenda: Greater insight. Greater confidence. Accelerate next-generation wireless. • Intro: a very brief history of IMS, Legacy (CS) vs. LTE (PS) domain considerations • Architecture of IMS, components, SIP • IMS call: SIP call-flow • What happens when out-of-coverage: flavors of fallbacks • Protocol features for successful and efficient VoLTE • Discussion, questions, comments? Wireless Communications © 2012 Agilent Technologies 2013 2

4. IMS - IP Multimedia Subsystem …how it all began… Greater insight. Greater confidence. Accelerate next-generation wireless. • 3GPP defined IMS in 1999 • IMS as the framework for delivery of multimedia services was standardized in 3GPP rel.5 for delivery of “Internet” services on GPRS. This was updated and extended to CDMA and WLAN. • In 2009 a group of over 40 organisations, operators, vendors etc. came together to form One Voice, whose aim was essentially to decide or drive the method of voice delivery on LTE through IMS. • GSMA finally adopted VoLTE in 2010, and so did many of the industry big companies • The use of IMS through the Verizon LTE network in the USA has accelerated the use of IMS development for mobile devices. Wireless Communications © 2012 Agilent Technologies 2013 4

5. Support for Voice with LTE Greater insight. Greater confidence. Accelerate next-generation wireless. 2G/3G – Circuit Switched calls have an allocated resource even during times of inactivity - even when nothing is being said • Inefficient use of available bandwidth • Access times between requesting resource and being able to talk were too slow to enable a reaction based allocation reduced flexibility for resource allocation LTE – UE will generally only be provided resources when it is necessary – even for voice • Allows efficient use of network resources. If we are saying nothing we will require no network resources • Places stress on the network to ensure suitable access timing and quality of service (QoS). LTE transportation is fully IP – no circuit switched services Wireless Communications © 2012 Agilent Technologies 2013 5

6. Voice with LTE: what is the goal and how to get there Greater insight. Greater confidence. Accelerate next-generation wireless. To deliver same standard of voice call with VoLTE as is delivered by 2G/3G. Most agree that the long term solution for voice is to use VoIP and an IMS based core network - However it will take time for networks to support this. For networks which do not support IMS several technologies are considered, namely: • CSFB (Circuit Switched Fall Back) - single radio approach • SVLTE or Dual Standby approach (Simultaneous Voice and Data LTE) dual radio approach • SRVCC (Single Radio Voice Call Continuity) – Voice on LTE with CS backup CSFB, SVLTE and SRVCC all involve some level of I-RAT behavior Wireless Communications © 2012 Agilent Technologies 2013 6

7. Enter IMS … Greater insight. Greater confidence. Accelerate next-generation wireless. Characteristic CS Mobile Telephony Legacy IP Standards bodies 3GPP, 3GPP2 IEEE 3GPP/3GPP2 and IEEE CS voice PS data PS data and PS voice Phone numbers IP addresses IP + support for legacy phone numbers Access Protocol Reservation based Reservation less SIP provides reservation based protocol for voice and video Connection Type Connection orientated Connectionless SIP provides connection orientated Centralised/ hierarchical/ closed Distributed/ flat/open IMS “walled garden” debate QoS Guaranteed bandwidth Best Effort GBR and BE supported AAA    ~5 billion >500M Will be lots! Primary service Addressing technique Architecture No. of devices IMS IP Multi-Media Service Wireless Communications © 2012 Agilent Technologies 2013 7

9. IMS has quite complex architecture… Greater insight. Greater confidence. Accelerate next-generation wireless. Architecture divided into: • Application Plane, Control Plane, User Plane Important part of Control Plane is the 1st point of contact for the UE – The CSCF (Call Session Control Function). CSCF is further divided into nodes: • Proxy CSCF (P-CSCF) (acts as the entry point in the IMS core network) • Interrogating CSCF (I-CSCF) • Serving CSCF (S-CSCF) Wireless Communications © 2012 Agilent Technologies 2013 9

10. P-CSCF: Proxy-Call Session Control Function of IMS Greater insight. Greater confidence. Accelerate next-generation wireless. • It is assigned to an IMS-capable UE terminal before registration (through OTA message), and does not change for the duration of the registration. • It may be in the home domain or in the visited domain. • It facilitates the routing path for mobile originated or mobile terminated session requests. • It is responsible for allocating resources for the media flows (bandwidth management) • It can also compress/decompress SIP messages using SigComp, which reduces the RTT over slow radio links. • It provides subscriber authentication, and is responsible for the security of the messages between the network and the user (ex: may establish an Ipsec). • It may include a Policy Decision Function (PDF), which authorizes media plane resources e.g. QoS over the media plane. Wireless Communications © 2012 Agilent Technologies 2013 10

11. SIP and IMS Greater insight. Greater confidence. Accelerate next-generation wireless. SIP server IP Network PSTN GSM IP Network 3G Telephone Network • SIP (Session Initiation Protocol) was initially designed to work in an open homogeneous IP network • SIP provides the signalling required to support call set-up procedures • SIP also provides many other services (caller id, multi-party & emergency calls…) Wireless Communications © 2012 Agilent Technologies 2013 11

12. To test VoLTE today, you need: Greater insight. Greater confidence. Accelerate next-generation wireless. • IMS/VoLTE capable device • IMS/VoLTE capable BSE • IMS Server • Somebody to talk to: Either another UE or IMS Client emulator Wireless Communications © 2012 Agilent Technologies 2013 12

13. Agenda: Greater insight. Greater confidence. Accelerate next-generation wireless. • Presentation: • Intro: a very brief history of IMS, Legacy (CS) vs. LTE (PS) domain considerations • Architecture of IMS, components, SIP • IMS call: SIP call-flow • What happens when out-of-coverage: flavors of fallbacks • Protocol features for successful and efficient VoLTE • Discussion, questions, comments? Wireless Communications © 2012 Agilent Technologies 2013 13

14. IMS uses SIP (Session Initiation Protocol) User A CSCF Proxy REGISTER User B REGISTER OK OK Greater insight. Greater confidence. Accelerate next-generation wireless. Optional AKAv2 authentication and IPsec SIP (Session Initiation Protocol) e.g. INVITE, TRYING, RING, OK, BYE etc. SDP (Session Description Protocol) INVITE e.g. m (media), a (attribute) etc. TRYING INVITE TRYING m=audio 49120 RTP/AVP 98 97 a=rtpmap:98 AMR/8000 a=fmtp:98 mode-set=7 RING RING OK OK RTP (Real-time Transport Protocol) e.g. AMR encoded speech ACK ACK RTCP (RT Control Protocol) e.g. Send/receive quality metrics RTP/RTCP BYE ACK BYE ACK CSCF = Call Session Control Function Wireless Communications © 2012 Agilent Technologies 2013 14

15. IMS uses SIP (Session Initiation Protocol) User A CSCF Proxy REGISTER Greater insight. Greater confidence. Accelerate next-generation wireless. User B REGISTER CSCF Proxy OK OK INVITE TRYING INVITE TRYING RING RING OK OK IP ACK ACK ACK User A User B SIP messages go via proxy server RTP voice traffic ~ peer to peer (or via other network nodes) RTP/RTCP BYE Router/IP network BYE ACK CSCF = Call Session Control Function Wireless Communications © 2012 Agilent Technologies 2013 15

18. What if…LTE/IMS out of coverage? Greater insight. Greater confidence. Accelerate next-generation wireless. Then: the Voice call to work would require some level or I-RAT. Let’s examine each of the voice related I-RAT behaviors separately. Wireless Communications © 2012 Agilent Technologies 2013 18

19. Phone x Network Configuration Greater insight. Greater confidence. Accelerate next-generation wireless. 1xRTT/eVDO/ eHRPD LTE GSM/W-CDMA/ TDSCDMA SVLTE Simultaneous Voice & LTE aka Dual Standby •Two phones in one case •1xRTT (or GSM/W-CDMA) chipset for all voice calls (CS only) •LTE/eVDO/eHRPD (and/or W-CDMA) separate chipset for data e.g. LTE/eVDO/HRPD radio GUI 1xRTT CS radio CS Voice Client Wireless Communications © 2012 Agilent Technologies 2013 19

20. Phone x Network Configuration Greater insight. Greater confidence. Accelerate next-generation wireless. 1xRTT/eVDO/ eHRPD LTE GSM/W-CDMA/ TDSCDMA CSFB Circuit Switched Fall Back •Handover from LTE to legacy 2G/3G for ALL voice calls •Use Circuit switched voice (and if available parallel slower legacy data) e.g. LTE/W-CDMA/GSM radio GUI CS Voice Client Wireless Communications © 2012 Agilent Technologies 2013 20

21. Phone x Network Configuration Greater insight. Greater confidence. Accelerate next-generation wireless. 1xRTT/eVDO/ eHRPD LTE GSM/W-CDMA/ TDSCDMA LTE / IMS Islands •Differentiated quality/price IMS voice in LTE coverage areas •End call at LTE edge •1xRTT for E911 and wide area coverage (CS only) E.g. LTE/W-CDMA/GSM radio IMS Voice Client GUI 1xRTT CS radio CS Voice Client Wireless Communications © 2012 Agilent Technologies 2013 21

22. Phone x Network Configuration Greater insight. Greater confidence. Accelerate next-generation wireless. 1xRTT/eVDO/ eHRPD LTE GSM/W-CDMA/ TDSCDMA SRVCC Single Radio Voice Call Continuity •IMS voice calling in LTE coverage areas •Quickly handover from LTE to legacy 2G/3G at LTE edge e.g. LTE/W-CDMA/GSM radio IMS Voice Client GUI CS Voice Client Wireless Communications © 2012 Agilent Technologies 2013 22

23. Phone x Network Configuration Greater insight. Greater confidence. Accelerate next-generation wireless. 1xRTT/eVDO/ eHRPD LTE GSM/W-CDMA/ TDSCDMA SVLTE CSFB Simultaneous Voice & LTE Aka Dual Standby Circuit Switched Fall Back e.g. LTE/ IMS islands SRVCC LTE / IMS only Single Radio Voice Call Continuity Most Operators will skip some steps World phones will need to roam with many network configurations LTE/eVDO/HRPD/GSM/WCDMA/ TDSCDMA radio 1xRTT CS radio IMS Voice Client GUI CS Voice Client Wireless Communications © 2012 Agilent Technologies 2013 23

25. LTE Protocol features that will affect how VoLTE performs Greater insight. Greater confidence. Accelerate next-generation wireless. • Multiple PDNs • QoS through QCI - QoS class identifier • TFT – Traffic flow Template • SPS – semi-persistent scheduling • TTI bundling • RoHC – Robust header compression • SigComp –SIP Signaling compression • Ipsec – security tunneling • … Wireless Communications © 2012 Agilent Technologies 2013 25

26. Protocol Features: VoIP QoS and Multiple PDN’s Greater insight. Greater confidence. Accelerate next-generation wireless. Strict packet delay-based QoS QoS will vary by allocation, by application and will be heavily dependent on system capacity. UE’s can have multiple data streams, Multiple PDN’s, Addresses, Port numbers etc. – All with different parameters: •Default DRB or Dedicated DRB •Guaranteed or non Guaranteed Bit Rate •Packet delay budget e.g. 50 to 300ms •Packet Error rate e.g. 10-2 to 10-6 Wireless Communications © 2012 Agilent Technologies 2013 26

28. Protocol Features: Traffic Flow Template Greater insight. Greater confidence. Accelerate next-generation wireless. IP packets Applications o TFT is set of packet filters ~ EPS bearer o TFT decides on IP traffic priority o Sort IP packets based on: •IP protocol; e.g. UDP, TCP •Port number •IP address •Priority Example configuration Internet Dedicated IMS-SIP RTP Non-GBR, low error IPv4/6 address 1 IPv6 address 2 TFT e.g. IMS-SIP signalling IP1 IP2 SIP LTE Radio GBR, high error Default e.g. Browser e.g. RTP voice stream RF UE Wireless Communications © 2012 Agilent Technologies 2013 28

29. Protocol Features: GBR, TFT, QoS, DRB’s signalled to UE Greater insight. Greater confidence. Accelerate next-generation wireless. Dedicated bearer, linked to default bearer GBR TFT Negotiated QoS Wireless Communications © 2012 Agilent Technologies 2013 29

30. Protocol Features: Semi-persistent scheduling (SPS) • Normal LTE operation – each SF is allocated individually. • For highly repeatable applications such as voice this is un-necessary waste of the DL signalling channel bandwidth. • In voice we normally only need a few 100’s of bits at regularly spaced intervals. • Greater insight. Greater confidence. Accelerate next-generation wireless. SPS is used to tell the UE to use specific resources for a fixed time period and can reduce significantly the DL signalling bandwidth required. Normal allocation - Each time an allocation is made, PDCCH resources are required DL Normal DL after SPS is scheduled 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 SPS allocation – reduced PDCCH signalling Wireless Communications © 2012 Agilent Technologies 2013 30

31. Protocol Features: TTI bundling Greater insight. Greater confidence. Accelerate next-generation wireless. If at the cell edge, UE can either increase power or increase coding rate to ensure reception at eNB If the UE cannot increase its power - eNB gets power headroom status reports from each UE, the UE can be instructed to use TTI bundling. TTI bundling prevents round trip ACK/NACK delays by transmitting all Redundancy versions in successive TTI’s. DL signalling is reduced (less ACKs/NACKs) and round trip delay is minimized. NACK NACK NACK ACK DL: TTI 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 UL: RV# 0 DL: TTI 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 UL: RV# 0 1 2 3 1 2 3 0 1 2 3 ACK 0 1 2 3 Normal transmission with HARQ feedback delay of 4ms for each 8ms HARQ cycle – up to 28ms for final ACK. Bundled TTI HARQ process 0 in 4 consecutive TTI’s (different RV). Total feedback delay is only 8ms. ACK Wireless Communications © 2012 Agilent Technologies 2013 31

33. Protocol Features: ROHC - Robust Header Compression Greater insight. Greater confidence. Accelerate next-generation wireless. Typical VoIP Header for IP v4/v6 = 40/60 Bytes With a typical voice rate of 12kbps, uncompressed IPv6 headers represent approximately 60% of the data sent / received LTE network efficiency very poor without RoHC Robust Header Compression is therefore required for LTE VoIP. Compression is over the air interface only i.e. between UE and eNB/NB/BTS It happens in PDCP, user plane traffic only. Wireless Communications © 2012 Agilent Technologies 2013 33

34. Protocol Features: RoHC continued Cuts IP overhead e.g. RTP streams for speech; 2:1 for IPv4, 3:1 for IPv6 • RoHCv2 simplification robustness handling of outof-sequence packets Greater insight. Greater confidence. Accelerate next-generation wireless. Applications • Payload DeCompressor RoHC Context Payload Header Payload Compressor RoHC Context LTE Radio Layers Payload LTE Radio Layers LTE Radio Header IP packets Network RF UE Wireless Communications © 2012 Agilent Technologies 2013 34

35. Protocol Features: SigComp - SIP Signalling Compression SIP/SDP signalling stack State full Compressor /De-compressor RTP/RTCP Media stack Greater insight. Greater confidence. Accelerate next-generation wireless. • Compresses text based SIP and SDP messages • Up to 3:1 compression • Standardized by the IETF RoHC working group • only implemented between a UE and P-CSCF Wireless Communications © 2012 Agilent Technologies 2013 35

36. Protocol Features: IP Sec Greater insight. Greater confidence. Accelerate next-generation wireless. Tunnel Mode (VPN like) • Entire original IP datagram encrypted More info in RFC4301, 4302, 4303 Transport Mode • AH added to protect against alteration of datagrams while in transit Normal IP traffic IP Header IP Header Transport Mode Tunnel Mode New IP Hdr AH AH Data Data IP Header Data Wireless Communications © 2012 Agilent Technologies 2013 36

37. Useful references Greater insight. Greater confidence. Accelerate next-generation wireless. GSMA IR.92 IMS Profile for Voice and SMS 3GPP TS 34.229 IP Multimedia call control protocol based on SIP and SDP, UE conformance specification 3GPP TS 33.178 Security Aspects of early IP Multimedia Subsystems (IMS) 3GPP TS 26.114 IP Multimedia Subsystems (IMS) Multimedia telephone: Media handling and interaction 3GPP TS 26.132 Speech and video telephony terminal acoustic test specification 3GPP TS 22.173 IP Multimedia Core Network Subsystem Multimedia Telephony Service and supplementary services 3GPP TS 23.228 IP Multimedia Subsystem (IMS) Stage 2 ITU-T P.862. Perceptual evaluation of speech quality (PESQ) ITU-T P.863. Perceptual Objecting Listing Quality Assessment (POLQA) PXT Website. www.agilent.com/find/PXT Agilent IMS/SIP www.agilent.com/find/E6966A Interactive Functional Test (IFT). www.agilent.com/find/IFT Wireless Communications © 2012 Agilent Technologies 2013 37

38. Thank you! Greater insight. Greater confidence. Accelerate next-generation wireless. Questions, comments? Thank you for attending: The Path to Voice over LTE - VoLTE with IMS (IP Multimedia Subsystem) By Andjela Ilic-Savoia Agilent Technologies Wireless Communications © 2012 Agilent Technologies 2013 38

40. CS vs. PS Greater insight. Greater confidence. Accelerate next-generation wireless. LTE PS IMS core emulation RF IP Audio 2G/3G PS RF IP RF IMS end-point emulation Audio 2G/3G CS Wireless Communications © 2012 Agilent Technologies 2013 40

41. Agilent E6966A 1FP & 2FP IMS-SIP client Greater insight. Greater confidence. Accelerate next-generation wireless. • Easy to install and use Windows 7 PC-based IMS-SIP client • IPv4, IPv6, Voice, video, SMS, GUI • Audio: AMR, AMR-WB, G711 a/uLaw, G722/.1, G729, GSM, iLBC, Speex/wb voice codecs • AMR/AMR-WB Octet-align, bandwidth-efficient, Mode-set negotiation and fixing • Video: H264, H263 • Play test files, audio loopback, auto-answer • Proven voice interop with VoLTE UEs Wireless Communications © 2012 Agilent Technologies 2013 41

43. Audio test scenario Human jury testing and/or PESQ with IP impairments Greater insight. Greater confidence. Accelerate next-generation wireless. Delay/Jitter/Loss insertion Agilent IMS-SIP server Ethernet Agilent PXT Agilent PXT VoLTE UE VoLTE UE RF RF Audio Analyzer Audio in/out headphone jack Audio in/out headphone jack Wireless Communications © 2012 Agilent Technologies 2013 43

44. Functional test scenario IMS/CS voice calling & Inter-RAT scenarios Greater insight. Greater confidence. Accelerate next-generation wireless. Agilent IMS server and several remote clients Agilent 8960 1xRTT cell Ethernet Agilent 8960 eHRPD cell Test automation Agilent PXT LTE cell RF Wireless Communications © 2012 Agilent Technologies 2013 44

45. Delay and Jitter insertion with ZTI NetDisturb Greater insight. Greater confidence. Accelerate next-generation wireless. ZTI NetDisturb Agilent IMS-SIP server & client(s) USB USB-Ethernet adaptors can be used with ZTI NetDisturb to add delay/Jitter to any Ethernet link in the system. NetDisturb can run on a separate PC or share a PC with Agilent IMS-SIP client and/or server Windows XP or 7 PC Ethernet VoLTE UE Delay/Jitter insertion http://www.zti-telecom.com/EN/NetDisturb.html Agilent PXT RF Wireless Communications © 2012 Agilent Technologies 2013 45

46. Agilent-B&K VoLTE Audio Test System Greater insight. Greater confidence. Accelerate next-generation wireless. Agilent IMS-SIP server & client .bat file, IPv6 router adv* * Batch file can be used to configure Windows 7 PC to transmit IPv6 Router Advertisements. Alternatively an IPv6 router can be added to the connection between a Windows 7 or XP PC and the PXT. B&K Audio Test Software B&K ZE 0948 Windows 7 PC USB VoLTE UE Ethernet Audio Line in/out Agilent PXT RF HATS B&K PESQ Audio Analyzer Wireless Communications © 2012 Agilent Technologies 2013 46

47. Adding Jitter to audio quality systems Agilent IMS-SIP server & client Greater insight. Greater confidence. Accelerate next-generation wireless. .bat file, IPv6 router adv* Delay/Jitter tool, e.g. ZTI NetDisturb USB B&K Audio Test Software Optional Delay/Jitter added to any link B&K ZE 0948 Windows 7 PC USB VoLTE UE Ethernet Audio Line in/out Agilent PXT RF HATS B&K PESQ Audio Analyzer Wireless Communications © 2012 Agilent Technologies 2013 47

48. Vzw VoLTE test plans Greater insight. Greater confidence. Accelerate next-generation wireless. Device Test Plan VoIP quality 1 •PESQ testing with VoLTE link Compliance Test Plan IMS VoIP 2 •VoLTE call processing, voice function, timers, InterRAT Compliance Test Plan LTE RCS 3 •Video functional, EAB Wireless Communications © 2012 Agilent Technologies 2013 48

49. Mode-sets explained Greater insight. Greater confidence. Accelerate next-generation wireless. SDP examples AMR AMR RTP/UDP/IP Example 1; use AMR and only allow 12.2kbps a=rtpmap:97 AMR/8000 a=fmtp:97 octet-align=1; mode-set=7 AMR: 8kHz sampling, 13 bit per sample, typically 20ms frames Mode 0 1 2 3 4 5 6 7 Bit rate kbps 4.75 5.15 5.9 6.7 7.4 7.95 10.2 12.2 Example 2; use AMR and allow several rates a=rtpmap:97 AMR/8000 a=fmtp:97 octet-align=1; mode-set=2,3,5,5,6,7 Quality OK AMR-WB: 16kHz sampling, 14 bit per sample, typically 20ms frames Good Mode 0 1 2 3 4 5 6 7 8 Bit rate kbps Quality 6.6 Good 8.85 12.65 V. Good 14.25 15.85 18.25 19.85 23.05 23.85 Excellent AMR-WB gives better speech quality than AMR at a given bit rate. Notes: •If client A suggests mode-set=7 and client B suggests modeset=2,3,5,5,6,7 then both will use only 7. •If more than one mode is agreed then mode is set on an RTP frame by RTP frame basis •Octet-align=1 means octet align •Octet-align=0 (or not present) means bandwidth efficient RTP encoding •Vzw recommends Octet align=0 and only AMR mode 7 or AMR-WB mode 2 Wireless Communications © 2012 Agilent Technologies 2013 49

8 the path to voice over lte - vo lte

8 the path to voice over lte - vo lte

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8 the path to voice over lte - vo lte