In order to transmit data from one location to another, stations (wireless APs and client radios) generate energy in the form of electromagnetic waves, which travel at the speed of light. These electromagnetic waves operate at different frequencies, which are defined as the number of periodic cycles traversed per second. The frequency and wavelength of an electromagnetic wave are inversely proportional and related by the speed of light:
Frequency is measured in Hertz (Hz), which individually represents one period, wavelength, or wave cycle. As a waveform travels from one point to another, it undergoes signal loss due to a phenomenon known as Free Space Path Loss (FSPL). However, lower frequencies (ex. 2.4 GHz) have much longer wavelengths and can propagate further than higher frequencies (ex. 5 GHz).
To relate the levels of energy associated with wireless receive signals, including attenuation (loss) of a wireless signal, we use decibels (dB). Decibels follow a logarithmic relationship where adding & subtracting decibels corresponds to exponential growth or reduction on the linear domain. Each time you add 3 dB or 10 dB, the value on the linear domain increases or decreases by a factor of x2 or x10, respectively.
The relationship between frequency and propagation is best illustrated by the Free Space Path Loss (FSPL) chart for 2.4 and 5 GHz waveforms. At a given distance, 5 GHz (the higher frequency) undergoes more attenuation. Therefore, 2.4 GHz WLANs are ideal for coverage scenarios, while 5 GHz are well-suited for density.
Different materials can affect the level of attenuation faced by wireless signals. For example, concrete attenuates wireless signals more than wood. Certain materials may also cause a wireless signal to propagate, or, ‘behave’ differently. For example, some metal surfaces can cause wireless signals to reflect, leading to less predictability throughout the WLAN environment. Other materials, like water (or people) can absorb wireless signals. Strategically, the construction of the WLAN environment can help or hinder how you design your wireless network.
