Characterization by Measurement of a CDMA 1x EVDO Network

Presenter: Mingzhe Li [lmz@cs.wpi.edu]Wireless Internet Conference (WICON’06)

Boston, Massachusetts, August 2006

Mark Claypool, Robert Kinicki, William Lee, Mingzhe Li, and Gregory Ratner

CS Department at Worcester Polytechnic Institute

Worcester, MA 01609USA

WICON’06 – Boston, Massachusetts

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Motivation

• EVDO 3G cellular data networks – Provides more bandwidth – More applications:

• Throughput sensitive• Latency sensitive• Multimedia streaming

• Current research of cellular data network performance– Theoretical analysis and simulations– Measurements studies

• 2G/2.5G networks• Focus on throughput• Few latency measurements and bandwidth estimations

• We need more characterization on EVDO networks.

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Introduction

• Measurement based characterization of EVDO network – TCP throughput– Round trip time – Loss rate– Bandwidth estimation

• Gauge the ability of EVDO to support the QoS of a range of applications

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Outline

• Introduction

• Methodology– Testbed – Tools– Experiment Design

• Analysis

• Conclusion and future work

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Testbed

Sierra Wireless Aircard 580 PCMCIA EVDO Network CardGnu Linux kernel 2.6.11

50 Mbps uplink

Measure downlinknetwork to the laptop

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Tools

Measurements Tools

TCP Throughput Gnu Wget.

RTT and loss rate Standard Linux ping.

npath Loosely based on pathrate

Bandwidth estimation using packet pair/train

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Experimen design

• Each test includes:– Measure wireless signal strength– Wget downloads 20 Mbyte file – Ping server 100 times– npath: capacity estimation

• Packet pairs length: 25 packets• Packet size: 1472, 1200, 1000, and 800 bytes• Repeat 30 times for each packet size

– Each test takes 12 minutes in total

• Run every 30 minutes for a week– November 28, 2005 to December 4, 2005

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Outline

• Introduction

• Methodology– Testbed – Tools– Experimental Desgin

• Analysis

• Conclusion and future work

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Analysis

• Data collected– 48 runs each day for 7 days– All tests with excellent signal strength

• -90 to -83 dBm

– TCP throughput: tcpdump and tcptrace– RTT and packet loss: ping– Network capacity: npath.

• Analysis focus– Week day: Wednesday November 30, 2005– Weekend: Saturday December 3, 2005

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TCP Throughput (cont.)

TCP throughput lower than theoretically EVDO networks No visual correlation between throughput and the time of day Satisfactory for most Internet applications

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TCP Throughput

TCP throughput are consistent between tests Slightly higher TCP throughput for weekend

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Round trip time of a weekday

Average RTT are consistent between tests Maximum RTT vary greatly. No visual correlation between RTT and the time of day.

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CCDF of RTT

Median RTT 200ms is too high for interactive applications. Maximum RTT around 1 second can seriously Impact the

performance of interactive applications.

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Bandwidth Estimation

Median of estimated bandwidth is consistent 5th percentile of estimated bandwidth varies.

Tests of a weekday

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Bandwidth Estimation (cont.)

Tests for weekday and weekend at 5:30pm

Bandwidth estimations are consistent. Only a small percentage of packet pairs get low estimatiions

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Summary and Conclusion

• 3G EVDO network provides higher throughput than 2G/2.5G cellular networks

• The high RTT may impact the performance of interactive applications• Bandwidth estimations are consistent, suggesting packet pairs are

sufficient for bandwidth estimation.• Neither throughput, round-trip time, nor bandwidth estimation correlates

with time of day or the day of the week.

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Future work

• More Characterizations– Mobility– Poor signal quality– Variable traffic load– Comparison with other cellar networks

• Application performance– Interactive applications (games, VoIP)– Multimedia streaming applications

Characterization by Measurement of a CDMA 1x EVDO Network

Presenter: Mingzhe Li [lmz@cs.wpi.edu]Wireless Internet Conference (WICON’06)

Boston, Massachusetts, August 2006

Mark Claypool, Robert Kinicki, William Lee, Mingzhe Li, and Gregory Ratner

CS Department at Worcester Polytechnic Institute

Worcester, MA 01609USA