KT VoLTE status and commercial interconnected ITU Workshop on “Voice and Video over LTE” Geneva, Switzerland, 1 December 2015 KT VoLTE status and commercial interconnected VoLTE service in South Korea June Young Jeon Principal Research Engineer juneyoung.jeon@kt.com

Contents In 1. KT’s Business and Korean Market 2. Commercial Interconnected VoLTE Service 3. Achievements & Issues 4. Conclusion

KT: Corporate Profile Subsidiaries In Established December 10, 1981 Revenue USD 23.4 Billion(2014) Stock Listing Korea, New York, London No. of Employees 23,754(as of Sep. 2014) Communications, IT Services, Media & Contents, Capital, Security Subsidiaries 7 Subsidiaries(USA, China, Japan, etc.) 10 Offices Overseas subsidiaries and offices Fixed Phone Broadband Mobile Pay-TV 17.3M (58.6%) 8.1M (42.4%) 17.2M (30.3%) 7.0M (25.1%)

Global Telecommunications Infrastructure Comparison ▣ The world’s highest level of broadband penetration rate ▣ Outstanding LTE connection and wireless penetration rate Broadband Penetration rate Time on LTE Wireless Penetration rate % of all households Measures portion of time connected to LTE Source: Open Signal, 2014  Source: OECD Internet Economy Outlook 2013  Source: OECD (2013)

Korean Market and KT’s market share In ▣ Wireline and wireless markets saturated, while Pay TV market is growing ▣ KT is leading wireline and Pay TV market, and is second in wireless market Telecom Market Size Trend KT‘s Market Share (as of Feb 2015) Growth rate of Wireless (2%) and Wireline (2%) implies market saturation Pay TV growing most rapidly: 19% Wireline: 42% (1st) Wireless: 30.4% (2nd) Pay TV: 28.6% (1st) - Rolled out VoLTE service(Oct, 2012) - Supporting UICC portability between mobile operators(From Jul, 2014) - Launched VoLTE international roaming service with NTT DoCoMo(Oct, 2015) - Completed Nation-wide VoLTE Interoperability (Oct, 2015) (Unit: mil.)

Contents In 1. KT’s Business and Korean Market 2. Commercial Interconnected VoLTE Service 3. Achievements & Issues 4. Conclusion

World’s 1st commercial Interconnected VoLTE Service ▣ Commercial Rollout (Jun. 2015) South Korea’s mobile network operators announced the commercial interconnected VoLTE service GSMA Awards Certificate of Special Recognition for Launch of World’s First Commercial Interconnected VoLTE Service in South Korea

Legacy Interworking Architecture SKT Network KT Network MGCF IMS Legacy Circuit UE-B MGW EPC/ E-UTRAN HSS TAS MME PCRF CSCF BGCF MGCF UE-A LGUplus Network E-UTRAN SGW PGW MGW Legacy Circuit MGCF IMS UE-C MGW EPC/ E-UTRAN Control Plane(SIP) User Plane(RTP media)

Dedicated Working Group ▣ TTA-WG9102 : VoLTE interworking specification between Korean MNOs ㆍMembers - TTA(Telecommunications Technology Association), KT, SKT, LG Uplus ㆍPeriod - 2012.10 ~ 2013.10 ㆍPurpose: to complete core protocols and transmission specifications call flow (ex, video announcement, ring back tone, early-session) SIP header, Reason header, SDP parameter, SIP numbering plan codec, response code, session timer device capability of voice-video switching IBCF requirements for interworking * TTA-WG9101: Specification of VoLTE Terminal for UICC Portability between Mobile Operators * TTA-WG9103: Rich Communication Suite(RCS) Interworking Specification for Mobile Network Operator

Evolution of Interworking Architecture KT Network Other Networks HSS TAS MME PCRF CSCF BGCF MGCF MGCF IMS UE-A Legacy Circuit UE-B E-UTRAN SGW PGW MGW MGW EPC/ E-UTRAN KT Network Other Networks HSS TAS ENUM MME PCRF CSCF IBCF IBCF IMS UE-A UE-B E-UTRAN SGW PGW TrGW TrGW EPC/ E-UTRAN Control Plane(SIP) User Plane(RTP media)

Practical Implementation ▣ Standard : IR.65 6.3.3 Interworking Routing of SIP signalling over the IMS NNI requires use of SIP URIs. Session requests based upon E.164 format Public User Identities require conversion into an NNI routable SIP URI format. ▣ Implementation in Korea : Routing in TEL URI format The Absence of Tier 1 ENUM causes a branch at terminating network KT Network Other Networks other ENUM Query : B  SIP URI kt ENUM NPDB Query : B  Routing Number ① ③ MGCF ② INVITE in TEL URI Format CSCF IBCF IBCF CSCF

Contents In 1. KT’s Business and Korean Market 2. Commercial Interconnected VoLTE Service 3. Achievements & Issues 4. Conclusion

Process of Service Interconnection 6th stage 3.8 million 12th stage 20 million 18th stage 55 million Interworking Test Trial Service Commercialization ‘15.05 ‘15.07 ‘15.08 ‘15.10 ▣ Milestones `15.05~`15.07 - User device / network / charging test in commercial network `15.07~`15.07 - Trial service(50 subscribers for each operator) `15.08~`15.10 - Migration of 55 million subscribers on a stage-by-stage basis

Achievements ▣ Switching Interconnection Traffic – Circuit to Packet MGCF IBCF With the vitalization of VoLTE services, other various supplementary services are expected to be provided creating benefits for both users and operators as listed below; - User side: high-quality voice/video call, etc. - Operator side: increase in subscribers, revenue, and efficiency of network resource usage. ▣ Enriching customer experience - Seamless switch between voice and video, faster connection speeds Media Type VoLTE 3G Voice Wideband (HD Voice) Narrowband Video VGA (480 X 640) QCIF (176 X 144)

Interworking Issues in Commercialization Stage ▣ End-to-End codec negotiation and media connection issues - Operator specific UE Spec RTP - RTP timeout Media - one-way call SIP Header - Header matching error SDP - Parameter processing error SDP (6%) SIP header (15%) 통신사별 독자 단말규격으로 E2E 코덱협상 실패 및 미디어연결 이슈 발생 임시방안 : CS망 우회 라우팅 조치방안 : 단말 보완, IBCF/TrGW 정합기능 추가 UNI 규격 협의 이전의 단말과 이후의 단말 to IBCF’s malfunction RTP (35%) Media (18%)

Contents In 1. KT’s Business and Korean Market 2. Commercial Interconnected VoLTE Service 3. Achievements & Issues 4. Conclusion

Conclusion Conclusion In ▣ Summary - Forming a dedicated working group in 2012 - Rolling out the commercial interconnected VoLTE service in 2015 - Providing HD-Voice and Video interconnection service Need a long time for interoperability test Call quality degradation due to E2E codec negotiation directly Ex) on Jan, 2015, We tested VoLTE roaming services between KT and CMCC through RAVEL, but couldn’t make a video call because of having no transcoding node. The direct interworking is impossible due to a difference portrait/landscape ,although the both of KT and CMCC’s devices are supported of all codecs.(VGA, H.264 etc.) ▣ Considerations - Transcoding overhead for existing operator-specific terminal - Further discussion on UNI specifications in detail - Global E-NUM for international interworking