1. WiFi, LTE, or Both? Measuring Multi-Homed Wireless Internet Performance
Shuo Deng, Ravi Netravali,
Anirudh Sivaraman, Hari Balakrishnan
MIT CSAIL

2. 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?

3. 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

4. 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

5. 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 …

6. Crowd-Sourcing Measurement
World-wide data collection: 16 countries, over measurements

7. Crowd-Sourcing Measurement
20% of the time, LTE has lower RTT than WiFi

8. Crowd-Sourcing Measurement
40% of the time, LTE has higher TCP throughput than WiFi
Uplink
Downlink 8

9. 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?

10. 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

11. Multi-Path TCP Setup Measurement setup
Measured at 20 different locations on the east and west coasts of the United States

12. MPTCP performs worse than TCP
Multi-Path TCP vs TCP
33% of the time, Multi-Path TCP gives higher throughput than TCP
MPTCP performs worse than TCP

13. 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

14. Multi-Path TCP Primary Subflow
Using different interface for primary subflow has a significant impact on short flows

15. Multi-Path TCP Congestion Ctrl
Using different congestion control algorithms affects long flows more

16. 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

17. 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

18. 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