This blog post clearly explains how radio frequency and wavelength influence the speed and quality of mobile communications, and why extremely high frequency (EHF) waves are central to modern communication networks.
Since the advent of smartphones, mobile wireless communication has become an indispensable part of modern life. The radio waves used in mobile wireless communication are invisible and hard to grasp, but they are a type of electromagnetic wave, the same category as visible light and X-rays. Radio waves propagate through the atmosphere at approximately 300,000 km per second, which is exactly the same as the speed of light in a vacuum. Generally, radio waves refer to electromagnetic waves that oscillate between approximately 3,000 and 3 trillion times per second. The number of oscillations per second is called the ‘frequency,’ and one oscillation per second is defined as 1 Hz. Therefore, radio waves have frequencies ranging from 3 kHz to 3 THz. Furthermore, frequency is inversely proportional to wavelength, which is the length of a single wave. Higher frequencies correspond to shorter wavelengths, while lower frequencies correspond to longer wavelengths. The product of the frequency and wavelength of an electromagnetic wave is constant and equals the speed of light.
Mobile wireless communications utilize radio waves in a frequency band lower than visible light or X-rays because they facilitate long-distance transmission of information. Higher frequencies make electromagnetic waves more directional, making them prone to absorption or scattering by dust or water vapor in the atmosphere, resulting in signal attenuation. Conversely, lower-frequency radio waves exhibit superior diffraction and penetration capabilities; they bend around obstacles and can pass through thin walls to spread over long distances. Among radio waves in the 3 kHz to 3 GHz band, ultra-low frequency (ULF) and longwave frequencies below 0.3 MHz can travel extremely long distances. They are primarily used for public purposes such as maritime communications, beacon communications, and guiding ships and aircraft. Frequencies in the 0.3 to 800 MHz band are utilized for shortwave broadcasting, international broadcasting, FM radio, and terrestrial analog TV broadcasting. Ultra-high frequencies (UHF) in the 800 MHz to 3 GHz band are primarily used for mobile wireless communications and are divided into four main bands: the ‘800–900 MHz band’, ‘1.8 GHz band’, ‘2.1 GHz band’, and ‘2.3 GHz band’. Since the advent of smartphones, the importance of efficient frequency management in the microwave band has grown significantly. Beyond 5G, the utilization of even higher frequency bands (several GHz to tens of GHz) is expanding technologically. Meanwhile, radio waves in the 3 GHz and above band exhibit extremely strong directionality, making them primarily used in special situations without obstacles, such as satellite communications or space communications.
The reason ultra-high frequency is used in mobile wireless communications is that it can transmit more information in a shorter time than the 0.3 to 800 MHz band. For example, assuming 4 waves are needed to transmit 1 bit of data, a 1 kHz very high frequency wave generates 1,000 waves per second, allowing only 250 bits of information to be transmitted per second. However, an 800 MHz ultra-high frequency wave generates 800 million waves per second, enabling the transmission of 200 million bits of information per second. A 1.8 GHz microwave can process a massive amount of information equivalent to 450 million bits per second. To compensate for the vulnerability of ultra-high frequency waves in long-distance information transmission, mobile wireless communications densely install wireless base stations that transmit and receive radio waves within a narrow area of about 2 to 5 km radius. These base stations are then connected by wire to transmit information in a relay manner, minimizing dead zones. Similar to mobile wireless communications, terrestrial digital TV broadcasting using UHF also strives to erect transmission towers at the highest possible locations to reduce obstacles along the radio wave propagation path.
The use of ultra-high frequencies has also dramatically improved the portability of mobile communication devices. This is because the effective length of an antenna for efficient signal reception is approximately 0.25 to 0.5 times the wavelength of the received signal. Utilizing high-frequency bands like ultra-high frequencies enables highly efficient signal transmission and reception even with antennas smaller than the palm of your hand. These technological advancements have enabled the miniaturization and high performance of modern mobile communication devices, including smartphones. Alongside the expanded use of high-frequency bands, they continue to form the foundation for an increasingly sophisticated mobile communication environment.
