Wireless networking has become one of the fastest growing segments within the computer industry.
Wireless signals are important because they can transfer information such as audio, video, our voices and data without the use of wires. Wireless signals are electromagnetic waves travelling through the air. These are formed when electric energy travels through a piece of metal (for example a wire or antenna) and waves are formed around that piece of metal. These waves can travel some distance depending on the strength of that energy.
The types of wireless technologies are numerous and include:
- AM and FM radio
- Satellite signals
- Cellular phones
- Two-way radio
What really separates one wireless technology from another is what makes them different.
Take frequency. Wireless signals occupy a spectrum, or wide range, of frequencies, which is the rate at which a signal vibrates. If the signal vibrates very slowly, it has a low frequency. If the signal vibrates very quickly, it has a high frequency. Frequency is measured in Hertz, which is the count of how quickly a signal changes every second.
As an example, FM radio signals vibrate around 100 million times every second. Since communications signals are often very high in frequency, we abbreviate the measurements for the frequencies – millions of vibrations a second is Megahertz (MHz), and billions of vibrations a second is Gigahertz (GHz). One thousand Megahertz is one Gigahertz.
Modulation is another major factor that separates the types of wireless technologies. In addition to having different frequencies, wireless signals can be different in the way they convey information. A wireless signal needs to be modulated–or changed–to send information. There are many types of modulation, and different technologies can use one or more types to send and receive information.
For example, the A in AM comes from Amplitude — the energy or strength of the signal, operating at a single frequency. An un-modulated AM wave repeats the same pattern. A modulated AM radio wave has higher and lower energy (amplitude) waves indicating higher and lower audio frequencies in the signal.
The F in FM comes from Frequency — defined by how quickly the wave vibrates every second.
The type of modulation various technologies use to communicate can be very different, and are often not compatible. Satellite equipment cannot speak directly to your laptop or smartphone, which uses Wi-Fi to send and receive information. This is because the radios in different devices can listen only to certain types of modulations and frequencies.
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