|  | 3.3 |
| Wireless Media
|  | 3.3.6 |
| Signals and noise on a WLAN
On a wired Ethernet network, it is usually a simple process to diagnose the cause of interference. When using RF technology many kinds of interference must be taken into consideration. Narrowband is the opposite of spread spectrum technology. As the name implies narrowband does not affect the entire frequency spectrum of the wireless signal. One solution to a narrowband interference problem could be simply changing the channel that the AP is using. Actually diagnosing the cause of narrowband interference can be a costly and time-consuming experience. To identify the source requires a spectrum analyzer and even a low cost model is relatively expensive. All band interference affects the entire spectrum range. Bluetooth™ technologies hops across the entire 2.4 GHz many times per second and can cause significant interference on an 802.11b network. It is not uncommon to see signs in facilities that use wireless networks requesting that all Bluetooth™ devices be shut down before entering. In homes and offices, a device that is often overlooked as causing interference is the standard microwave oven. Leakage from a microwave of as little as one watt into the RF spectrum can cause major network disruption. Wireless phones operating in the 2.4GHZ spectrum can also cause network disorder. Generally the RF signal will not be affected by even the most extreme weather conditions. However, fog or very high moisture conditions can and do affect wireless networks. Lightning can also charge the atmosphere and alter the path of a transmitted signal. The first and most obvious source of a signal problem is the transmitting station and antenna type. A higher output station will transmit the signal further and a parabolic dish antenna that concentrates the signal will increase the transmission range. In a SOHO environment most access points will utilize twin omnidirectional antennae that transmit the signal in all directions thereby reducing the range of communication.