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WLAN Performance Prediction and Environments a framework for discussion

WLAN Performance Prediction and Environments a framework for discussion. Rick Denker, VeriWave. Importance of Environment. In Ethernet testing prediction was simple. Test the switch/router, test the cable, and the results could be easily predicted

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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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