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WLAN Performance Prediction and Environments a framework for discussion

Explore the importance of wireless LAN environments and testing, differentiate between test and customer environments, and understand the impact of noise, traffic overlap, and signal strength on performance. Learn about different test environments - Open Air, Cabled, Test Boxes, and Faraday Cages. Gain insight on mapping test environments to real-life scenarios for optimal performance expectations.

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WLAN Performance Prediction and Environments a framework for discussion

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  1. WLAN Performance Prediction and Environmentsa framework for discussion Rick Denker, VeriWave Rick Denker, VeriWave Inc.

  2. Importance of Environment • In Ethernet testing prediction was simple. Test the switch/router, test the cable, and the results could be easily predicted • In wireless the variation of customer environments is a critical factor to performance. • Interference • Interaction • Distance Rick Denker, VeriWave Inc.

  3. Two Types of Environments • Test Environments • Created by equipment developers • Often artificial, not matching a customer use • High degree of control • Small number of types • Customer Environments • Any place equipment is used • Large variation Rick Denker, VeriWave Inc.

  4. Test Environments • Four basic types of environments: • Open Air • Cabled • Test Boxes • Faraday Cages • Each has different trade-offs • Almost all developers use a combination of the four basic types of environments Rick Denker, VeriWave Inc.

  5. Test Environment: Open Air • Resistance to interference: Low • Cost: Free • Size limitations: None • Typical Use: • Development • Antenna testing: • Required for longer range tests • Strengths: • Matches customer usage, only solution for certain spatial tests • Weaknesses: • Not appropriate for crowded test environments Rick Denker, VeriWave Inc.

  6. Test Environment: Cabled • Resistance to interference: High • Cost: Very Low • Size limitations: None • Typical Use: • Crowded lab environments, manufacturing • Antenna tests: • Not appropriate • Strengths: • Easy to set-up • Weaknesses: • Idealized results that do not match the randomness of open air Rick Denker, VeriWave Inc.

  7. Test Environment: Test Boxes • Resistance to interference: Very high • Cost: Moderate • Size limitations: Yes • Typical Use: • Development labs • Antenna testing: • Not appropriate for most antennas • Strengths: • Clear environment • Weaknesses: • Near field effects, multiple box sizes required Rick Denker, VeriWave Inc.

  8. Test Environment: Faraday Cage • Resistance to interference: Very high • Cost: Expensive • Size limitations: Yes • Typical Use: • Shared resource in development labs • Antenna testing: • Good for antenna tests • Strengths: • Clear environment • Weaknesses: • Can only test 3-4 devices before traffic gets congested Rick Denker, VeriWave Inc.

  9. Summary Chart: Test Environments Rick Denker, VeriWave Inc.

  10. Customer Use Environments Customer environments vary widely • Hard to create a small set of model environments • Very expensive Implies an approach of characterizing an environment by a small set of key variables Potential key summary variables are: • Amount of noise • Overlap with other traffic • Signal strength Rick Denker, VeriWave Inc.

  11. Key Variable: Amount of Noise • Kind of noise: • Cordless phones • Microwave ovens • Bluetooth devices • etc. • Nature: • Dynamic • Cannot be measured for single point in time (average over a typical day) • Effect: • Causes frames with CRC errors • Measure of different noise levels: • # CRC errors per time Rick Denker, VeriWave Inc.

  12. Key Variable: Overlap with Other Traffic • Kind of traffic: • APs placed close together • Traffic from neighboring business • Nature: • Dynamic • Traffic could be measured at peak traffic times of the day for a short period • Channel mapping issue • Effect: • Causes contention for air • Measure of overlap: • Duty cycle of background traffic • Burstiness of background traffic Rick Denker, VeriWave Inc.

  13. Key Variable: Signal Strength • Kind of strength variation: • Distance • Construction materials • Location of metal equipment • Nature: • Mostly static (you can move metal file cabinets) • Effect: • Causes poor signal strength • Measure of signal strength: • Range of signal strength levels (Typically a color-coded contour map on a floor play layout) Rick Denker, VeriWave Inc.

  14. Mapping Test Environments to User Environments • Noise, Overlap, and Signal Strength can have a significant impact on performance for a given customer • Measurements in ideal test environments can set overly high false expectations • Providing the user with a good understanding of how equipment will perform in their environment is key Rick Denker, VeriWave Inc.

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