2.4 GHz and 5.8 GHz or 5 GHz are the most common wireless frequency band used in sync with IEEE 802.11 Wi-Fi standards. Wireless systems use radio frequencies which works in between 20 kHz and 200 GHz. Hertz (Hz) is the unit of frequency in the International System of Units (SI).
Frequency is the number of times a specified event repeats itself in a unit time interval. Hertz is named after Heinrich Rudolf Hertz who was the first person to prove the existence of electromagnetic waves.
Hertz is defined as one cycle per second where a cycle (also known as oscillation) refers to a single change from positive to negative to positive in a wave (radio waves in case of wireless communication). If a wave completes 60 cycles/oscillations in one second, the frequency of that wave would be 60 Hz.
Commonly used units
While going through information about wireless networks, you will come across terms such as kHz, MHz, and GHz. These are multiples of the unit of frequency. MHz stands for Megahertz while GHz stands for Gigahertz.
- 1 kHz = 1000 Hertz. This means that the wave completes 1000 cycles in one second.
- 1 MHz = 1 million Hertz =Hz = 1000 kHz. This means that the wave completes 1 million cycles in 1 second.
- 1 GHz = 1 billion Hertz = Hz = 1000 MHz. This means that the wave completes 1 billion cycles in 1 second.
The frequency of radio waves in wireless networks
Wireless systems use radio frequency (RF) signals for communication. Radio waves are electromagnetic waves that fall in the range of 20 kHz and 200 GHz.
In the 1980s, U.S. government opened three wireless frequencies for public use – 0.9 GHz (900 MHz), 2.4 GHz and 5.8 GHz. 5.8 GHz is also sometimes called 5 GHz. Out of this 2.4 GHz and 5.8 GHz were used in different Wi-Fi standards.
900 MHz (or 0.9 GHz) was not found to be useful for data networking and thus was limited to cordless phones.
What if all devices use the same frequency?
If all devices started using the same frequency for communication, the signals will collide and cause what is called destructive interference.
Destructive interference leads to loss of energy, and thus the signal will be lost before reaching the receiving antenna on your device.
Uses of different frequency bands
Many wireless standards are followed while using a wireless local area network (WLAN). Some of the most commonly used include 802.11a, 802.11b, 802.11g, 802.11n, 802.11ac.
Some of these specifications use 5.8 GHz frequency band (802.11a, 802.11ac) while other use 2.4 GHz frequency band (802.11b, 802.11g, 802.11n, 802.11ac). 802.11ac has a dual-band technology and can support both bands simultaneously. Both bands have their pros and cons.
Advantages of using 2.4 GHz frequency band
- Devices that use 2.4 GHz frequency band are cheaper to manufacture.
- Low frequency requires less power for transmission than high frequency. Thus, the range of the signals is much wider.
- Low frequency can easily penetrate brick walls and is not easily obstructed by other heavy objects.
- Less power is required to transmit signals using lower frequency band.
Disadvantages of using 2.4 GHz frequency band
- Other household appliances and wireless devices, such as wireless keyboard, Bluetooth devices, microwave ovens, etc., the same frequency band. The signals from these devices can interfere with that of the wireless network.
- Low-frequency signal can carry fewer data. This limits the speed of the network.
Advantages of using 5 GHz frequency band
- Since the network will operate on a different frequency than the household items, there will be less interference.
- High-frequency radio waves can carry more data and thus can reach higher speed limits.
Disadvantages of using 5 GHz frequency band
- This frequency band has high power requirements.
- The range of the signal is also low due to high power required to transmit data.
- Devices compatible with this band are more expensive to manufacture.
- The signal does not penetrate brick walls easily. So, the signal can easily be obstructed.
Which frequency is better to use?
Recent wireless standards such as 802.11n use 2.4 GHz frequency. The drawbacks of the frequency are handled by implementing modulation techniques such as OFDM (Orthogonal Frequency Division Multiplexing Tutorial).
Also, by using multiple channels working at narrow frequency bands, called MIMO (multiple inputs multiple outputs), the data speed can be increased.