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