J. Patrick FrantzExecutive Director

Center for Multimedia CommunicationRice University

IEEE Vehicular Technology ConferenceApril 24, 2003

J. Patrick FrantzExecutive Director

Center for Multimedia CommunicationRice University

IEEE Vehicular Technology ConferenceApril 24, 2003

Performance of IEEE 802.11b Wireless LAN in an Emulated Mobile

Channel

Performance of IEEE 802.11b Wireless LAN in an Emulated Mobile

Channel

Performance of 802.11b is Well Understood for Indoor UseOutdoor and Mobile Environments Remain an Unexplored SpacePlans for Use in Such Environments Prompts Further Study (e.g. Mercedes & Other Telematics Applications)

Performance of 802.11b is Well Understood for Indoor UseOutdoor and Mobile Environments Remain an Unexplored SpacePlans for Use in Such Environments Prompts Further Study (e.g. Mercedes & Other Telematics Applications)

MotivationMotivation

Reviewed Literature for Measurements of Outdoor 2.4GHz ISM ChannelDetermined a Reasonable Set of Channel Parameters for Repeatable ExperimentsPrecise Variation of Parameters to Measure Relationship to System PerformanceUsed Channel Emulation for Reliable & Repeatable Results

Reviewed Literature for Measurements of Outdoor 2.4GHz ISM ChannelDetermined a Reasonable Set of Channel Parameters for Repeatable ExperimentsPrecise Variation of Parameters to Measure Relationship to System PerformanceUsed Channel Emulation for Reliable & Repeatable Results

MethodologyMethodology

Experimental SetupExperimental Setup

Setup 3 Peer-to-Peer Links With H/W From 2 Different Manufacturers

Wanted to Test Differences in Baseband Implementations from Two Leading Chipset Manufactureres

AgereIntersil

Setup 3 Peer-to-Peer Links With H/W From 2 Different Manufacturers

Wanted to Test Differences in Baseband Implementations from Two Leading Chipset Manufactureres

AgereIntersil

2 Orinoco WLAN PC Cards (Agere Chipset)2 D-Link Air DWL-520 WLAN PCI Cards (Intersil Chipset)TAS 4500 FLEX5 RF Channel Emulator from Spirent CommunicationsIPERF v1.1.1 Network Testing Software

2 Orinoco WLAN PC Cards (Agere Chipset)2 D-Link Air DWL-520 WLAN PCI Cards (Intersil Chipset)TAS 4500 FLEX5 RF Channel Emulator from Spirent CommunicationsIPERF v1.1.1 Network Testing Software

Equipment UsedEquipment Used

Experimental SetupExperimental Setup

MethodologyMethodology

Velocity - Combined Effect of Ricean and Rayleigh Fast Fading with Doppler ShiftDelay Spread - Created an Ad Hoc Multipath Channel to Study Effects of Delay Spread (RMS)

Similar to Power Delay Profiles from LiteratureUsed 6-Path Model

Velocity - Combined Effect of Ricean and Rayleigh Fast Fading with Doppler ShiftDelay Spread - Created an Ad Hoc Multipath Channel to Study Effects of Delay Spread (RMS)

Similar to Power Delay Profiles from LiteratureUsed 6-Path Model

Variable Modulations - Constrained the Hardware to Specific Modulations (1, 2, 5.5 & 11Mbps)SNR - Monitored and Recorded SNR at both ends of Test Setup to Account for Path Losses in the System.Careful System Isolation and Shielding

Variable Modulations - Constrained the Hardware to Specific Modulations (1, 2, 5.5 & 11Mbps)SNR - Monitored and Recorded SNR at both ends of Test Setup to Account for Path Losses in the System.Careful System Isolation and Shielding

MethodologyMethodology

Both Implementations of 802.11b Showed Significant Performance Degredations in Mobile Channels, as ExpectedStrong Link Between SNR and Flat Fading & Delay Spread Susceptibility

Both Implementations of 802.11b Showed Significant Performance Degredations in Mobile Channels, as ExpectedStrong Link Between SNR and Flat Fading & Delay Spread Susceptibility

Experimental ResultsExperimental Results

Throughput vs. Velocity in Rayleigh & Ricean Fading

Throughput vs. Velocity in Rayleigh & Ricean Fading

Packet Loss vs. Velocity in Rayleigh & Ricean Fading

Packet Loss vs. Velocity in Rayleigh & Ricean Fading

Throughput and Packet Loss vs. Delay Spread

Throughput and Packet Loss vs. Delay Spread

Throughput & Packet Loss vs. Velocity (D-Link, Rayleigh, 15dB)

Throughput & Packet Loss vs. Velocity (D-Link, Rayleigh, 15dB)

Throughput & Packet Loss vs. Velocity (D-Link, Rayleigh, 15dB)

Throughput & Packet Loss vs. Velocity (D-Link, Rayleigh, 15dB)

Throughput & Packet Loss vs. Delay Spread

Throughput & Packet Loss vs. Delay Spread

ConclusionsConclusions

Typical Implementations of 802.11b are Far Less Effective in Mobile ChannelHowever, No Reason that Current Implementations Can’t be ModifiedRAKE Receivers for Indoor Channels are Insufficient for Outdoor Channels with High RMS Delay SpreadSlight Incompatibilities Between Chipsets Adversely Affect Performance

Typical Implementations of 802.11b are Far Less Effective in Mobile ChannelHowever, No Reason that Current Implementations Can’t be ModifiedRAKE Receivers for Indoor Channels are Insufficient for Outdoor Channels with High RMS Delay SpreadSlight Incompatibilities Between Chipsets Adversely Affect Performance