1. WLAN Maintenance and Troubleshooting Design and Site Survey Considerations
2. Building Materials 3. Identify Problematic Areas 4. Signal Attenuation These values are examples, and attenuation may vary depending on the actual material used 3 - 6 dB Wireless device position 12 dB Metal door in brick wall 6 dB Metal door 3 dB Office window 4 dB Cinderblock wall 6 dB Glass wall with metal frame 3 dB Plasterboard wall Signal Attenuation Through Object Object in Signal Path 5. Non-802.11 Sources of Interference20 MHz 20 MHz 802.11 a or g OFDM 802.11 b DSSS 6. Microwave Ovens Loud moving signal seen at max. Duty cycle higher in part of band Drifts in frequency 7. Bluetooth Speckled pattern in spectrogram Dutycycle spread across band See more hops in max. hold See hops in max. 8. Wireless Phones Pulses increase in max. Speckled appearance in swept = frequency hopper Duty cycle fairly low and spread across band 9. Analog Cameras Constant signal seen in avg./max. Dutycycle Is 100% Constant power level stripe 10. Verifying Coverage with Site Survey
In a wireless network creation process, there commonly are two site surveys:
Pre-deployment site survey to determine AP position and density, along with problematic areas
Post-deployment site survey, to audit coverage, cell overlap, roaming and RF-related issues
Pre-deployment site survey is never the first step in a wireless project
Post-deployment site survey should be for verifying conformity to the design
11. Which Coverage for Which Usage 12. WLAN Coverage and Capacity 13. Recommended Parameters for2.4-GHz Data Networks Minimum packet performance should be greater than 90 percent successful packet transfer (10 percent lost) 31 22 -62 -72 48 14 4 -84 -94 1 16 6 -81 -91 2 18 8 -79 -89 6/5.5 20 10 -72 -82 12/11 22 12 -67 -77 24 28 18 -63 -73 36 35 25 -61 -71 54 Recommended Minimum SNR Rx SNR Recommended Minimum Rx Threshold Rx Threshold Data Rate 14. Voice Cell Overlap Guidelines
A typical deployment showing a 15-20% overlap from each of the adjoining cells
Provides almost complete redundancy throughout the cell
15. AP Placement for Location 16. Coverage Overlap 17. Multifloor Coverage 18. Site Survey Tools 19. Basic Survey Tools 20. Summary
Walls, doors, and furniture may affect and degrade a wireless signal.
Many other devices may use the ISM band, and although they would not be directly visible to the wireless infrastructure, they may degrade or completely block the wireless signals.
The size of the coverage area, the overlap between cells, and the number and position of APs depends on the type of wireless devices expected in the network.