802.11 Security

Radio Transmission

Wireless networking is accomplished by sending and receiving radio waves between a transmitter and receiver. The theory behind RF data transmission can get very complicated and is outside the scope of this book. However, there are some basic concepts you should understand when you implement a WLAN.

Data Rate

A radio wave consists of electromagnetic energy. Visible light, television transmissions, and cosmic radiation are all forms of radio waves. Regardless of the type or purpose of the electromagnetic energy, these waves can be measured by several metrics. The frequency of a radio wave is how often the waveform completes a cycle in a given amount of time. The most common unit of measurement of frequency is the Hertz (Hz). A 1 Hz signal completes one cycle per second while a 10 Hz signal completes 10 cycles per second. Figure 1-1 shows the difference between the waveforms of a 10 Hz signal and a 1 Hz signal.

Figure 1-1. A 10 Hz signal (top) and 1 Hz signal (bottom)

Generally, the faster the frequency, the more information you can transmit and receive. The method of encoding (or modulating) the data affects the amount that can be transmitted. Some encoding techniques are more resilient to errors but end up with lower data rates. Conversely, high data rate modulation mechanisms may be more susceptible to outside interference.

Signal Strength

In the most general sense, ...