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VoLTE*: A Lightweight Voice Solution to 4G LTE Networks
Guan-Hua Tu1,Chi-YuLi1, Chunyi Peng2, Zengwen Yuan1,Yuanjie Li1,Xiaohu Zhao2,Songwu Lu1
1University of California, Los Angeles2The Ohio State University
HotMobile’16
Voice: Essential Cellular Service§ 30+ years (from 1G to 4G)§ Full coverage:
¨ All carriers¨ Almost all users
2Chunyi Peng HotMobile'16
Voice Evolution in 4G LTE § 4G LTE: packet-switched (PS) only
¨ Traditional voice: circuit-switched (CS) for carrier-grade quality
Chunyi Peng HotMobile'16 3
InternetPS Domain
4G Gateway
circuitTelephony
NetworkCS Gateways
3G/2G CS Domaincircuit circuit
Voice Evolution in 4G LTE § 4G LTE: packet-switched (PS) only
¨ Traditional voice: circuit-switched (CS) for carrier-grade quality
Chunyi Peng HotMobile'16 4
InternetPS Domain
4G Gateway
Telephony
Network
?
VoLTE: Voice over LTE§ Standard solution (cellular carrier industry)§ Carry voice in packets (aka. VoIP)
Chunyi Peng HotMobile'16 5
InternetPS Domain
4G Gateway
Telephony
NetworkIMSCore
MediaGateway
SignalingServer
Data Packet Flow VoLTE Signaling Flow VoLTE Voice Flow
The Good § Successor of cellular voice for LTE users
¨ Comparable carrier-grade quality
§ Enable rich communication¨ Voice/video calls, video conferencing, HD voice …
Chunyi Peng HotMobile'16 6
But, The Ugly§ Deploymentpain
¨ 20outof480LTEcarrierssupportVoLTE (Oct2015)¨ Delayedrolloutuntillate2014inUScarriers(AT&T,Verizon,T-
Mobile)- Nonationwidedeploymentyet
§ IPMultimediaSubsystem(IMS):complexandcostly¨ Proposedin2002¨ LittleprogressuntilVoLTE
Chunyi Peng HotMobile'16 7
IMSCore
MediaGateway
SignalingServer
Alternative to VoLTE§ VoIP: on-the-top (OTT) mobile data app
¨ Hangouts, Skype, Line, Viber, Whatsapp, …
§ Pros: low cost (Carriers), OTT benefits§ Cons (concerns): quality?
Chunyi Peng HotMobile'16 8
4G Gateway
PS Domain VoIPService
Q1: VoLTE or no VoLTE?
Q2: Alternative lightweight and cost-effective solution?
Chunyi Peng HotMobile'16 9
VoLTE or No VoLTE?
Comparison VoLTE and VoIP over 4G LTE§ Deployment cost§ Operation complexity§ Voice quality
Chunyi Peng HotMobile'16 10
Deployment and Operation
VoLTE- DeployIMS- Upgrade4Ginfrastructure
¨ BS,PSgateways,andOAM(Operation,Administration,management)subsystem
¨ Upgradefirmware/OSofmobiledevicestosupportcarrier-specificVoLTE
VoIP over 4G LTE+ Nonewdeployment/upgrade
¨ Reuse4GPSinfrastructure¨ ReuseVoIPserviceprovider’s
infrastructure¨ ExistingCellular– VoIP
translation¨ Noupgradeonmobiledevices
- Concerns- Quality?- Compatibilitywithlegacyvoice
Chunyi Peng HotMobile'16 11
Voice Call Quality§ Small-scaleassessment
¨ 10staticlocations,20routes,50participants¨ VoIP:GoogleHangouts
§ Callsetuptime§ Voicecallquality(subjective)§ Calldroprate
Chunyi Peng HotMobile'16 12
Note:VoLTE atearlydeployment (12/2014– 02/2015)
Call Setup time§ Comparable performance except VoIP-CS case
¨ Caller-to-Callee:V-to-V,V-to-C,H-to-H,H-to-C¨ V:VoLTE;C:CS;H:Hangout
§ Takeaway:enhanceVoIP-CS callsupport
Chunyi Peng HotMobile'16 13
Signal strength is week (<-115dbm) Signal strength is strong (>-90dbm)
Voice Call Quality§ Record calls and offline listening
¨ ITU standard metrics: ACR(AbsoluteCategoryRating)andCCR(CategoryRatingComparison)
§ Comparable voice quality (VoLTE win: congestion & CS)
Chunyi Peng HotMobile'16 14
ACR: Absolute Category Rating CCR: Category Rating Comparison
Call Drop Rate
§ Comparable in static and most mobility§ VoLTE (4G-2G/3G): even worse (implementation
issues on SRVCC) [mobicom’15]
Chunyi Peng HotMobile'16 15
[mobicom’15] Yunhan Jia, et.al,PerformanceCharacterizationandCallReliability ProblemDiagnosisforVoiceoverLTE
Scenarios VoLTE HangoutStatic (strong/weak coverage) 0% 0%Mobility (4G only, strongà weak)
0% 0.5%
Mobility (4G à2G/3G) 8% 4%
VoLTE’s Advantage: High QoS Bearer
Chunyi Peng HotMobile'16 16
Internet
4G Gateway
PS Domain
IMSCore
MediaGateway
SignalingServer
4G GatewayPS Domain VoIP
Service
VoLTEVoIP
Chunyi Peng HotMobile'16 17
VoLTE’s Advantage: High QoS Bearer
Delivery PriorityVoLTE Voice Bearer Guaranteed-Bit-Rate 2VoLTE Signaling Bearer Best Effort 1
(highest)Data Service Bearer Best Effort 6-9
4G Gateway
VoLTE*: Alternative Solution?
Chunyi Peng HotMobile'16 18
VoLTE*: A Lightweight Voice Solution§ Both good of VoIP and VoLTE
¨ VoIP-centric: low cost on deployment and operation¨ High QoS bearer: call quality
Chunyi Peng HotMobile'16 19
4G Gateway
PS Domain VoIPService
High-QoSbearer
VoLTE*: Voice Service Classes§ ApplydifferentQoS profilestoVoIPpacketsin4GLTE
Chunyi Peng HotMobile'16 20
Service Class DescriptionFirst Use highest QoS; quality is similar to VoLTE
Business Always better than the best-effort QoS profile Deluxe Economy Better than best-effort when needed (e.g.,
congestion occurs)Economy best-effort
Modest Support§ Device:specifyQoS profiles(serviceclasses)forVoIPpackets
§ VoIPserviceproviders:connecttotheexistingIPXusedbycarrierstoensureQoS
§ Whilecongestionoccurs,¨ UpgradeQoS ofVoIPpacketsifsubscribingtheplan(e.g.,“DeluxeEconomy”)
Chunyi Peng HotMobile'16 21
VoLTE*: Benefit all Parties§ Carriers:gainmorerevenuefrompriorityvoiceservicewithoutdeployingandoperatingIMScore
§ VoIPserviceproviders:moredailyactiveusers– e.g.,havemoremobilead.revenue
§ Users:betterservicewithcheaperfare
Chunyi Peng HotMobile'16 22
VoLTE* Evaluation in Crowded Areas§ Hacking: VoLTE signaling bearer reused to carry
VoIP traffic [ccs’15]§ VoLTE*: congestion-resistant +lightweight
Chunyi Peng HotMobile'16 23
Uplink Downlink
[ccs’15] Chiyu Li, et.al Insecurity of Voice Solution VoLTE in LTE Mobile Networks
Possible Downsides§ Technicaldrawbacks(LTERadio)
¨ NoVoLTE-likeenergy-savingmechanism¨ NoVoLTE-likecoverageenhancemechanism
§ Non-Technicaldrawbacks(businessconcerns)¨ CarriersmaynotwanttosharecustomerswithVoIPserviceproviders
¨ Carriersmaynoteasilydeploynewmultimediaservices
Chunyi Peng HotMobile'16 24
Summary§ VoLTE*:BothgoodofVoIPandVoLTE
¨ VoIP:Easydeployment/upgradeandlowcost¨ VoLTE:callquality
§ VoLTE (vs.VoIP)¨ Comparableorslightlybetterquality¨ But,maynotworththeefforts
§ PromisesofVoLTE*deployment¨ RoomforVoLTE (notreplacement)¨ RolesofVoIPproviderandcellularcarriers
Chunyi Peng HotMobile'16 25
Thankyou!Questions?
Chunyi Peng HotMobile'16 26
Open Issues in VoLTE*§ Interplay of VoIP (external) and cellular CS
domain¨ API, translation
§ Migration from 4G to 2G¨ Poor support for data (VoIP) in 2G
§ Voice billing (different QoS)
Chunyi Peng HotMobile'16 27
Internet
4G Gateway
PS Domain
IMSCore
MediaGateway
SignalingServer
Data Packet Flow VoLTE Signaling Flow VoLTE Voice Flow
Chunyi Peng HotMobile'16 28
VoLTE*: Four Service Classes§ ApplydifferentQoS profilestoVoIPpacketsin4GLTE
29
Service Class Description
First Use highest QoS; quality is similar to VoLTE
Business Always better than the best-effort QoS profile
Deluxe Economy Better than best-effort when needed (e.g., congestion occurs)
Economy best-effort
Chunyi Peng HotMobile'16
VoLTE*: Only Requires Essential Support from Infrastructure§ AllowdevicestospecifyQoS profileforVoIPpackets
¨ Itisaoperationalpolicyissuenotatechnicalproblem- QoS negotiation isamandatoryprocedurebystandards
§ AllowVoIPserviceproviderstoconnecttotheexistingIPXusedbycarriersinpractice¨ ToensureQoS
§ Whilecongestion occurs,¨ 4GinfrastructurewillupgradeQoS ofVoIPpacketsifusers
subscribetheserviceclass “DeluxeEconomy”
30Chunyi Peng HotMobile'16
VoLTE*: Benefit all Parties§ Users have better service with cheaper fare
§ Carriers get more revenue from priority service without deploying and operating IMS core
§ VoIP service providers have more daily active users – e.g., have more mobile ad revenue
31
Charge (cent/min) T-Mobile AT&T Verizon SprintCellular Call 450 mins 6.7 8.9 7.8 6.7
900 mins 3.3 4.4 3.9 3.3Hangouts 450/900 mins 1.2 1.2 0.6 0.9
(Surveyed on Sep. 2015)
Chunyi Peng HotMobile'16
Evaluation of VoLTE* in Crowded Areas
32
¨ ComparisonofJitterofnormalVoIPandVoLTE*(VoIP+4GInfrastructure-assisted)
Uplink Downlink
• VoLTE*isa congestion-resistantvoiceservice,similartoVoLTE;butVoLTE*islightweightandbenefitallparitiesChunyi Peng HotMobile'16