iCellular: Device-Customized Cellular Network Access on ... · iCellular: Device-Customized Cellular Network Access on Commodity Smartphones Yuanjie Li 1, HaotianDeng2, ChunyiPeng2,

iCellular:Device-CustomizedCellularNetworkAccessonCommoditySmartphones

YuanjieLi1,Haotian Deng2,Chunyi Peng2,Zengwen Yuan1,Guan-HuaTu1,Jiayao Li1,Songwu Lu1

1 UniversityofCalifornia,LosAngeles2 TheOhioStateUniversity

UserDemandsforHigh-QualityCellularAccess

2

• “Wewanthigh-qualitycellularnetworkserviceanytime,anywhere”• Nosinglecarriernetworkcanalways satisfythesedemands

Home Campus

• Lettheenddevicesaccessmultiplecarriersandchoosethebestone• Emergingefforts:GoogleProjectFi,AppleSIM,Samsunge-SIM,etc.

AnAlternativeApproach:Multi-CarrierAccess

3

Home Campus

• Lettheenddevicesaccessmultiplecarriersandchoosethebestone• Emergingefforts:GoogleProjectFi,AppleSIM,Samsunge-SIM,etc.

AnAlternativeApproach:Multi-CarrierAccess

4

Home Campus

Desired Features forMulti-CarrierAccess

5

#1:Switchwhenexpected

#2:Makeawisedecision

#3:Fast andseamless switch

Example:Willmy phone switchtoT-Mobile whenit is betterthan Sprint?

Example:Will my phone select T-Mobile 4G or Sprint 3G?

Example:Willmy phone quicklyswitchtoSprint4Gwithminimal data disruption?

Outline

6

• Multi-carrieraccesstoday:threeissues• Rootcauseanalysis

• iCellular design

• Evaluation

Multi-CarrierAccessPrimer

7

• Rich coverage at each location (3G/4G, multi-carriers)• Inter-carrier switch: monitoringà selection à switch

Monitoring networks…

Selection: to Sprint

Issue 1:PassiveMonitorMissesBetterNetwork

8



#2:Make a wisedecision

Issue 1:PassiveMonitorMissesBetterNetwork

9

• Monitoringistriggeredwhentheservingcarriernetworkfails• Optimized for single-carrier access: roaming to other carriers was not preferred

No monitoring




Issue 2:Unwise Network Selection

10




Issue 2:Unwise Network Selection

11

• Intra-carrier handoff is still preferred,although other carriers are better• Servingcarriernetworkaffects themobilitydecision




to Sprint3G

Issue 3:Long Switch Time and Service Disruption

12




Issue 3:Long Switch Time and Service Disruption

13

Monitoringnetworks…

• Exhaustive search forallpossiblecarriernetworks




Reality ofMulti-CarrierAccess

14


#2:Makeawisedecision

#3: Fast andseamless switch

15

P1:Passivemonitor

P2:Unwiseselection

Canwesolvetheseproblemswithoutchanging3G/4Gdesign?

Empowertheenddevicewithlow-levelcellularinfo!

Reality ofMulti-CarrierAccess

P3:Long switch and

disruption

P1:Passivemonitor

P2:Unwiseselection

iCellular Overview

Activemonitor Intelligentselection Directswitch

P3:Long switch and

disruption

12

iCellular Architecture

• Ain-phonesoftwareservice• Leverage low-level mechanism and info• Runtime cellular info (knowingmoreforawiserdecision)• Abilityforadaptation inexistingmechanisms(actionreadynow)

SW

HW Cellularinterface

Activemonitor Intelligentselection Directswitch

Diagnosticport

ActiveMonitor

18

• Goal:proactively detectotheravailablecarriernetworks• Mechanism:manualnetworksearch• Challenge:searchingothercarriersmaydisruptdataservice!

Downlinkdata


Activemonitor

Intelligentselection

Directswitch

ActiveMonitor

19

• Keyinsight:datareceptionisregulatedbypagingcycle

• Schedulethemanualnetworksearchwithlow-levelcellularfeedback


PhonestateOn

Off TimePagingcycle

NodataActivemonitor


Directswitch

IntelligentSelection

20

IsT-Mobile4Gfaster?

• Withoutregistration,dataperformancecannotbemeasured…

• Bettersignalstrength≠Fasterspeed!• Heterogeneouscarriernetworks

0

5

10

T-4G S-4G

DownlinkSpeed(Mbps)

?

RSS

T-4G -95dBm

S-4G -100dBm

Activemonitor


Directswitch

IntelligentSelectionwithPrediction

21

IsT-Mobile4Gfaster?

• Collecteachcarriernetwork’sprofile:QoS +radioparameters

• Predictcarrierperformancewithradiomeasurements+cellularprofile

RSS QoS class

T-4G -95dBm Background

S-4G -100dBm Interactive

0

5

10

T-4G S-4G

DownlinkSpeed(Mbps)

Activemonitor


Directswitch

DecisionFaultsPrevention

22

• Conflictswithnetwork-sidemobilityrules

Intra-carrierhandoff

ToT-Mobile4G

Activemonitor


Directswitch

DecisionFaultsPrevention

23

• Conflictswithnetwork-sidemobilityrules

• Safeguarddeviceselectionbypredictingdecisionfaults

Intra-carrierhandoffprofile

T-4G Handoff to3GifRSST-4G<-120dm,andRSST-3G>-90dBm

RSS

T-4G -123dBm

T-3G -85dBm

T-Mobile4Gunreachable

T-4GàT-3Ghandoffwouldbetriggered!Active

monitorIntelligentselection

Directswitch

AdaptiveDirectSwitch

24

• Goal:minimizeswitchtimeandservicedisruption• Keyinsight:mostswitchtimeisspentonexhaustivesearch• Solution: cross-layeradaptationforPLMNpreference

Monitoringnetworks…

Activemonitor


Directswitch

Implementation

• In-phone daemon service on Nexus 6/6P• Leverage Project Fi SIM card for multi-carrier access• Built-in strategies for better usability

SW

HW Cellularinterface

Active monitor Predictor Direct switch

Diagnosticport

Selection strategies (prediction-based, radio-only, etc.)

Evaluation Setup

26

• Comparisonbetween iCellular and Project Fi

• Pedestrianmobilityandstaticexperiments at campus

• Four representative applications:• Bulk file transfer: SpeedTest• Web: Firefox• Video streaming: Youtube• VoIP: Skype

Data Performance Improvement

27

• Downlink speedincrement: 23.8% onaverage,3.74x atmaximum• Video suspension reduction: 37% onaverage,6.9x atmaximum• VoIP latencyreduction:60.4% onaverage,1.9x atmaximum• Web loading timereduction: 7.3% on average, 46.5% at maximum

0 20 40 60 80

100

0 0.2 0.4 0.6 0.8 1

Project FiiCellular-prediction

0 0.2 0.4 0.6 0.8 1


020406080

100

0 1 2 3 4 5 6 7 8


0 0.5 1 1.5 2

Speedtest Web

Youtube Skype

Gap = |x - Optimal| / Optimal


0 20 40 60 80

100

0 0.2 0.4 0.6 0.8 1

Project Fi

0 0.2 0.4 0.6 0.8 1

Project Fi

020406080

100

0 1 2 3 4 5 6 7 8

Project Fi

0 0.5 1 1.5 2

Speedtest Web

Youtube Skype


Project Fi

0 20 40 60 80

100

0 0.2 0.4 0.6 0.8 1


0 0.2 0.4 0.6 0.8 1


020406080

100

0 1 2 3 4 5 6 7 8


0 0.5 1 1.5 2

Speedtest Web

Youtube Skype



0 20 40 60 80

100

0 0.2 0.4 0.6 0.8 1

Project Fi

0 0.2 0.4 0.6 0.8 1

Project Fi

020406080

100

0 1 2 3 4 5 6 7 8

Project Fi

0 0.5 1 1.5 2

Speedtest Web

Youtube Skype


Project Fi

0 20 40 60 80

100

0 0.2 0.4 0.6 0.8 1


0 0.2 0.4 0.6 0.8 1


020406080

100

0 1 2 3 4 5 6 7 8


0 0.5 1 1.5 2

Speedtest Web

Youtube Skype



0 20 40 60 80

100

0 0.2 0.4 0.6 0.8 1

Project Fi

0 0.2 0.4 0.6 0.8 1

Project Fi

020406080

100

0 1 2 3 4 5 6 7 8

Project Fi

0 0.5 1 1.5 2

Speedtest Web

Youtube Skype


Project Fi

0 20 40 60 80

100

0 0.2 0.4 0.6 0.8 1


0 0.2 0.4 0.6 0.8 1


020406080

100

0 1 2 3 4 5 6 7 8


0 0.5 1 1.5 2

Speedtest Web

Youtube Skype



0 20 40 60 80

100

0 0.2 0.4 0.6 0.8 1

Project Fi

0 0.2 0.4 0.6 0.8 1

Project Fi

020406080

100

0 1 2 3 4 5 6 7 8

Project Fi

0 0.5 1 1.5 2

Speedtest Web

Youtube Skype


Project Fi

0 20 40 60 80

100

0 0.2 0.4 0.6 0.8 1


0 0.2 0.4 0.6 0.8 1


020406080

100

0 1 2 3 4 5 6 7 8


0 0.5 1 1.5 2

Speedtest Web

Youtube Skype



0 20 40 60 80

100

0 0.2 0.4 0.6 0.8 1

Project Fi

0 0.2 0.4 0.6 0.8 1

Project Fi

020406080

100

0 1 2 3 4 5 6 7 8

Project Fi

0 0.5 1 1.5 2

Speedtest Web

Youtube Skype


Project Fi

0 20 40 60 80

100

0 0.2 0.4 0.6 0.8 1

Project Fi

0 0.2 0.4 0.6 0.8 1

Project Fi

020406080

100

0 1 2 3 4 5 6 7 8

Project Fi

0 0.5 1 1.5 2

Speedtest Web

Youtube Skype


CDF

(%)

Project Fi

Inter-carrier Switch Time Reduction

28

• Average saving: 37.7s à 8.8s (76% reduction)• FurtherimprovementispossiblewithbetterSIMimplementation

Time Event16:40:36.756 Deregister from Sprint 4G16:40:36.890 Invalidate SIM data request16:40:36.892 Reconfiguring SIM card…… … 16:40:43.100 SIM card configuration done16:40:44.501 Scanning T-Mobile 4G cell 1, available16:40:44.709 Attach request (to T-Mobile 4G)16:40:45.471 Attach accept

SIMcardReconfig:6.4s

Networkregistration:2.3s

iCellular’s Overhead

29

• Signalingoverhead:32msg/satmaximum

• CPU/Memory:below2%/16.5MB

• Energyconsumption:4.75% battery usage in24-hrnormal usage test• Comparabletonormalmobileapps:e.g.,4.54%forSkypeinsametest

0 1 2 3 4 5

0 300 600 900 1200C

PU

Usa

ge (

%)

Time (s)

Conclusion

30

• Multi-carrieraccessispromising,butits full benefits are constrained• Legacy3G/4Gwasdesignedforsingle-carrier access

• Theenddevicecantakeamoreactiveroleinmulti-carrieraccess

• Leveragingruntimecellularinformationisanalternativedimensiontoenhancedevice-sideinter-carrierswitch

Thank you!

31

Documents

iCellular: Device-Customized Cellular Network Access on ... · iCellular: Device-Customized Cellular Network Access on Commodity Smartphones Yuanjie Li 1, HaotianDeng2, ChunyiPeng2,