Performance of IEEE 802 11 b Wireless LAN

Performance of IEEE 802. 11 b Wireless LAN in an Emulated Mobile Channel J. Patrick Frantz Executive Director Center for Multimedia Communication Rice University IEEE Vehicular Technology Conference April 24, 2003

Motivation Performance of 802. 11 b is Well Understood for Indoor Use Outdoor and Mobile Environments Remain an Unexplored Space Plans for Use in Such Environments Prompts Further Study (e. g. Mercedes & Other Telematics Applications)

Methodology Reviewed Literature for Measurements of Outdoor 2. 4 GHz ISM Channel Determined a Reasonable Set of Channel Parameters for Repeatable Experiments Precise Variation of Parameters to Measure Relationship to System Performance Used Channel Emulation for Reliable & Repeatable Results

Experimental 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 Agere Intersil

Equipment Used 2 Orinoco WLAN PC Cards (Agere Chipset) 2 D-Link Air DWL-520 WLAN PCI Cards (Intersil Chipset) TAS 4500 FLEX 5 RF Channel Emulator from Spirent Communications IPERF v 1. 1. 1 Network Testing Software

Experimental Setup

Methodology Velocity - Combined Effect of Ricean and Rayleigh Fast Fading with Doppler Shift Delay Spread - Created an Ad Hoc Multipath Channel to Study Effects of Delay Spread (RMS) Similar to Power Delay Profiles from Literature Used 6 -Path Model

Methodology Variable Modulations - Constrained the Hardware to Specific Modulations (1, 2, 5. 5 & 11 Mbps) SNR - Monitored and Recorded SNR at both ends of Test Setup to Account for Path Losses in the System. Careful System Isolation and Shielding

Experimental Results Both Implementations of 802. 11 b Showed Significant Performance Degredations in Mobile Channels, as Expected Strong Link Between SNR and Flat Fading & Delay Spread Susceptibility

Throughput vs. Velocity in Rayleigh & Ricean Fading

Packet Loss vs. Velocity in Rayleigh & Ricean Fading

Throughput and Packet Loss vs. Delay Spread

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

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

Throughput & Packet Loss vs. Delay Spread

Conclusions Typical Implementations of 802. 11 b are Far Less Effective in Mobile Channel However, No Reason that Current Implementations Can’t be Modified RAKE Receivers for Indoor Channels are Insufficient for Outdoor Channels with High RMS Delay Spread Slight Incompatibilities Between Chipsets Adversely Affect Performance