© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—6-1

WLAN Maintenance and Troubleshooting

Design and Site Survey Considerations

© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—6-2

Building Materials

© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—6-3

Identify Problematic Areas

© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—6-4

Signal Attenuation

Object in Signal Path Signal Attenuation Through Object

Plasterboard wall 3 dB

Glass wall with metal frame 6 dB

Cinderblock wall 4 dB

Office window 3 dB

Metal door 6 dB

Metal door in brick wall 12 dB

Wireless device position 3 - 6 dB

These values are examples, and attenuation may vary depending on the actual material used

© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—6-5

Non-802.11 Sources of Interference

20 MHz 20 MHz

802.11 a or gOFDM

802.11 bDSSS

© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—6-6

Microwave Ovens

Loud moving signalseen at max.

Duty cycle higher inpart of band

Drifts in frequency

© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—6-7

Bluetooth

Speckled patternin spectrogram

Duty cyclespreadacrossband

See more hops in max. hold

See hops in max.

© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—6-8

Wireless Phones

Pulses increasein max.

Speckled appearancein swept = frequency

hopper

Duty cyclefairly low andspread acrossband

© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—6-9

Analog Cameras

Constant signalseen in avg./max. Duty

cycleIs 100%

Constant powerlevel stripe

© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—6-10

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

© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—6-11

Which Coverage for Which Usage

© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—6-12

WLAN Coverage and Capacity

© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—6-13

Recommended Parameters for 2.4-GHz Data Networks

Data Rate Rx Threshold Recommended Minimum Rx

Threshold

Rx SNR Recommended Minimum SNR

54 -71 -61 25 35

48 -72 -62 22 31

36 -73 -63 18 28

24 -77 -67 12 22

12/11 -82 -72 10 20

6/5.5 -89 -79 8 18

2 -91 -81 6 16

1 -94 -84 4 14

Minimum packet performance should be greater than 90 percent successful packet transfer (10 percent lost)

© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—6-14

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

© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—6-15

AP Placement for Location

© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—6-16

Coverage Overlap

© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—6-17

Multifloor Coverage

© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—6-18

Site Survey Tools

© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—6-19

Basic Survey Tools

© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—6-20

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.

© 2008 Cisco Systems, Inc. All rights reserved. IUWNE v1.0—6-21