WiFi, LTE, or Both? Measuring Multi-Homed Wireless

Internet Performance

Shuo Deng, Ravi Netravali,

Anirudh Sivaraman, Hari Balakrishnan

MIT CSAIL

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Motivation

• How good are LTE and WiFi networks in practice?

• How do they compare with each other?

• Should a mobile device use one or both networks?

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Main Findings

• No clear cut for WiFi and LTE selection

– Crowd-Sourcing Measurement

• Multi-Path TCP not always outperform TCP

• Interface selection for primary subflow matters

– Controlled Measurement on Multi-Path TCP

• Short-flow apps benefit most from TCP

– Mobile App Measurement

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Main Findings

• No clear cut for WiFi and LTE selection

– Crowd-Sourcing Measurement

• Multi-Path TCP not always outperform TCP

• Interface selection for primary subflow matters

– Controlled Measurement on Multi-Path TCP

• Short-flow apps benefit most from TCP

– Mobile App Measurement

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Crowd-Sourcing Measurement

• Free App for Android ( >1000 downloads)

• Measures WiFi and LTE performance on the same device at (almost) the same time

– Signal Strength

– Ping

– DNS Query Time

– TCP Throughput

– …

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Crowd-Sourcing Measurement• World-wide data collection: 16 countries, over

3000 measurements

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Crowd-Sourcing Measurement

• 20% of the time, LTE has lower RTT than WiFi

• 40% of the time, LTE has higher TCP throughput than WiFi

Crowd-Sourcing Measurement

Uplink

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Downlink

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Crowd-Sourcing Summary

• WiFi and LTE can win over each other significantly

• Mobile devices should be able to choose between WiFi and LTE adaptively

• Or, use both?

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Main Findings

• No clear cut for WiFi and LTE selection

– Crowd-Sourcing Measurement

• Multi-Path TCP not always outperform TCP

• Interface selection for primary subflow matters

– Controlled Measurement on Multi-Path TCP

• Short-flow apps benefit most from TCP

– Mobile App Measurement

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Multi-Path TCP Setup• Measurement setup

• Measured at 20 different locations on the east and west coasts of the United States

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Multi-Path TCP vs TCP• 33% of the time, Multi-Path TCP gives higher

throughput than TCP

MPTCP performs worse than TCP

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Multi-Path TCP Measurement

• Measure Multi-Path TCP using different configs

– Use WiFi or LTE for primary subflow

– Use coupled or decoupled congestion control

– Use backup and non-backup mode

• Quantify by relative difference

– |Tput1–Tput2|/Tput1

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Multi-Path TCP Primary Subflow• Using different interface for primary subflow has a

significant impact on short flows

• Using different congestion control algorithms affects long flows more

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Multi-Path TCP Congestion Ctrl

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Multi-Path TCP Backup Mode

• Energy efficiency: MPTCP may consume excessive energy, even in Backup Mode

LTE, Non-backup Mode LTE, Backup Mode

WiFi, Non-backup Mode WiFi, Backup Mode

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Multi-Path TCP Summary

• Multi-Path TCP does not always outperform TCP

• Choosing the proper interface for primary subflow improves MPTCP throughput for short flows

• Using different congestion control affects long flow more

• Multi-Path TCP may consume excessive amount of energy

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Takeaways

• Multi-homed devices need to choose between WiFi and LTE adaptively

• Devices need to decide when to use Multi-Path TCP or TCP

– Multi-Path TCP does not always outperform TCP

– Multi-Path TCP may not be energy efficient

• Devices need to decide which network to transmit on first when using Multi-Path TCP