User's Manual

Table Of Contents

Deployment Guide 21

BASIC WI-FI CONCEPTS

Microwave ovens, wireless video cameras, Bluetooth headsets, and cordless phones can all interfere with Wi-Fi

signals (see Figure 5). Excess noise in an environment is often difficult to diagnose and can have a major negative

impact on network performance. To discover noise sources, a spectrum analysis system is needed. AirMagnet

provides an affordable spectrum analysis tool that operates in the 2.4 GHz and 5 GHz spectra.

Figure 5 Path Loss with Noise (from Microwave)

Now that you have a sense of how Wi-Fi performance changes over distance and with noise, look at some ways to

perform channel assignment. If two access points are on the same channel right next to each other, they are forced

to share the same spectrum. This means that they share the 54 Mbps available in 802.11a/g rather than each being

capable of 54-Mbps speeds independently. This essentially halves the bandwidth for each access point. To manage

this situation, make sure that neighboring APs are on different channels and that their power is adjusted so that it

does not overlap that of other APs with the same channel.

In the 2.4 GHz spectrum, there are 11 channels in the United States. However, a Wi-Fi signal consumes more than

one channel. Consequently, there are only 3 non-overlapping channels: 1, 6, and 11. To achieve optimal

performance, you need to design a channel layout pattern such as the one on the left in Figure 6.

Figure 6 Channel Layout Patterns

Signal-to-Noise

Ratio

Distance

Noise

Received Signal

6460

7-to-1 Layout Pattern

116

111

6 111

3-to-1 Layout Pattern