GSMA语音通信演进白皮书

Status and challenges in thefurtherevolu3on from VoLTE towardseXtendedRealityCalling and other communica3on services in 6G. 1.Introduc+on Summary This white paper describes the evolu3on path and growing challenges of developing, maintaining andevolving a strategy for mobile network operators’ communica3on services in a context ofthe lack ofaclearroadmapfor the industryandsignificant decline in the usage of voice calls by mobile customers. 3GPP and GSMA are ac3vely engaged on delivering to the industry an evolu3on path for IMS services,voice and video calls, based on expectedincrease in availabilityof ViLTEservices and the evolu3on toIMS Data Channel capabili3es to add in-call interac3vity capabili3es. However, bothViLTEand IMS Data Channelare challenged by the lack of universal support.Several yearsaMer being released, ViLTE is s3ll not being supportedna3velyinthemain mobile OSecosystems,represen3nga significant part of mobile customers.Consequently,the service has not been massivelydeployed in mobile networksand demandis low.IMS Data Channel, except in China, does not havesignificant support, current or planned, in the majority of smartphone anddiallervendors.Withthissitua3on,there are no commitments from operators in many regions to evolve their IMS networks andac3vely support ViLTE and IMS DC-based services. In this context, the effort from 3GPP focusingon the standardiza3on forconversa3onalservices ineXtended Reality (XR) servicesexpected to be part of 6G (Rel.21onwards) could be challenged by a lackof industry support,leading to an uncertain ROI (return on investment) foroperators and otherstakeholders. Furthermore, security and trustworthiness of 6G communica3on servicesprovided byoperator networksis expected toplay into future proofingcurrent voiceandmul3media networks. Without a clear path in the industry thatenablesoperatorsiden3fy a path togenerate incrementalrevenue from evolved Comms services, the investments are compromised.Notonly to embrace all thesetechnologies, but also to con3nue maintaining exis3ng voice services in 6Gnetworks, consideringdeclining voice traffic scenarioswithup to 10% reduc3on year on year in some markets. In addi3on, new service launchesmightrequiretheupgradingoflegacy IMS networks,causingconsiderable impactand relevant investments.In this case,the support ofall stakeholdersin the valuechainfor a futurestandards-basedfeature set on newCommunica3onsServicesis essen3al,as ithasbeenfor RCSin the messaging space. Background and context In the late 1990s it became clear that IP based voice was taking offoverfixed networks and that SIP-based voice calls were going to become relevant. Although some par3es proposed to move to SIP-basedvoice calling with 3GPP Release 4, many players in the ecosystem thought that it would be easier to keepwith circuit switched(CS)voice in parallel with IP for data.When LTE was implementedwith 3GPPRelease 8,the first versions con3nued with this “backward-looking” view where voice was enabled usingCS-fallback to an earlier genera3on network rather than suppor3ngSIP based-based voice callingin LTE. Once there was mass availability of LTE networks the need for a “na3ve” voice service over LTE to avoidCS fallback issues became evident for the industry. Since LTE was already IP orientated, the op3on todeliver operator voice via IP Comms and IMS capabili3es to the mobile space led to the development ofIMS in 3GPP standards and the subsequent adop3on of GSMA’s specifica3on for the Voice over LTE(VoLTE) service[5]. VoLTE addressed the migra3on to aPacket Switched(PS)only domain by leveraging on the capabili3es oftheIP Mul3media Subsystem(IMS) to offer voice and messaging services over LTE, and enabledinclusionofasetof communica3on servicesand addi3onal service capabili3es,thusenablingthe migra3on awayfromlegacy CS networks. Furthermore, VoLTE provided customers with enhanced voice quality, reduced 3me taken to establishcallsand the possibility of placing video calls. Tofacilitate deployments,in 2010GSMApublished the first set of recommenda3ons for a unified VoLTEprofile: IR.92 IMS Profile for Voice and SMS[5]. This was complemented at the end of 2011 with theaddi3on of Video services over IMS (referred as ViLTE), with GSMA IR.94 IMS Profile for Conversa3onalVideo Service[7]. Both services were delivered asGSMAPermanent Reference Documents. In 2019, andaMer several years of development, 3GPP published the first industry-wide specifica3ons for 5G as partof 3GPP Release 15. The industry agreed onevolving VoLTE towards Voice over NR (VoNR), and GSMAreleased in 2020 a new set of requirements for ensuring industry interoperability around mobile Voice in5G (NG.114-IMS Profile for Voice, Video and Messaging over 5GS[8]). However, the ini3al deployments of VoLTE services were quite complicatedwithslow adop3on withinthedeviceecosystemand mul3ple IMS profiles for service delivery. The standards for IMS and its usagewithin LTE networks were quite open,