In this blog post, we’ll examine the types and characteristics of electromagnetic waves and explore how the development of radio waves, in particular, has influenced the advancement of mobile wireless communication.
What are electromagnetic waves and radio waves?
In just a few years since the advent of smartphones, mobile wireless communication has become an indispensable part of our daily lives. Thanks to advanced communication technologies, we can communicate with anyone we want, anytime and anywhere—and one of the starting points for these technologies was the discovery of electromagnetic waves. Therefore, this article will explore the different types of electromagnetic waves, with a particular focus on how the development of radio waves has influenced the advancement of mobile wireless communication.
Electromagnetic waves are waves composed of two components—electric and magnetic fields—that propagate through space at the speed of light in a vacuum, which is approximately 300,000 km/s. Electromagnetic waves can be classified into radio waves, infrared, visible light, ultraviolet, X-rays, and gamma rays based on their wavelength, and radio waves used in wireless communication are also a type of electromagnetic wave.
The number of times a wave, such as an electromagnetic wave, oscillates in one second is called the “frequency,” and one oscillation per second is defined as 1 hertz (Hz). Frequency is inversely proportional to “wavelength,” which refers to the length of a single wave. In other words, the higher the frequency, the shorter the wavelength, and the lower the frequency, the longer the wavelength. The product of the frequency and wavelength of an electromagnetic wave is constant and, in a vacuum, equals the speed of light. Therefore, the classification of electromagnetic waves based on wavelength can be understood in conjunction with their classification based on frequency. Radio waves generally refer to electromagnetic waves in the frequency range from several kHz to several hundred GHz; internationally, the radio spectrum is divided into nine frequency bands ranging from 3 kHz to 3,000 GHz.
Why are radio waves used in mobile wireless communications?
The reason radio waves with lower frequencies than visible light or X-rays are used in mobile wireless communications is that they are advantageous for transmitting information over long distances. Generally, as the frequency increases, the straight-line propagation of radio waves becomes stronger, and the extent to which they are affected by obstacles or water vapor in the atmosphere may also increase. Conversely, radio waves with relatively low frequencies can utilize diffraction and penetration characteristics, allowing them to be transmitted over a wider area while being less affected by obstacles. Here, diffraction refers to the phenomenon where radio waves pass around the edges of obstacles and spread out behind them. However, the actual propagation characteristics of radio waves depend not only on frequency but also on various conditions such as terrain, buildings, atmospheric conditions, and the height and structure of the antenna.
Radio waves can be classified by frequency into long waves, medium waves, short waves, very high frequency (VHF), and ultra-high frequency (UHF), among others. Among these, the lower-frequency bands can travel relatively long distances and have been used for various purposes, such as maritime communications, beacon communications, and the guidance of ships and aircraft. The shortwave band has been utilized for shortwave broadcasting and international broadcasting, while the very high frequency (VHF) band has been used for FM radio and terrestrial broadcasting. Meanwhile, ultra-high-frequency (UHF) waves have been utilized in various wireless communication fields, including mobile wireless communications. Taking advantage of the characteristic that radio waves at higher frequencies travel in a more straight line, they are also used in fields such as satellite communications and space communications.
One of the key reasons for using UHF in mobile wireless communications is that it is relatively easier to secure a wider bandwidth compared to lower-frequency radio waves, allowing for the transmission of more information in a shorter time. For example, assuming that two waves are needed to transmit 1 bit of data, a radio wave oscillating 1,000 times per second generates 1,000 waves per second, allowing for the transmission of 500 bits of information per second. In contrast, a radio wave oscillating 800 million times per second generates 800 million waves per second, allowing 400 million bits of information to be transmitted per second under the same conditions. As shown here, the higher the frequency, the greater the potential to transmit more information in the same amount of time; therefore, relatively high-frequency bands have been utilized in mobile wireless communications. However, actual communication speeds and data throughput are not determined solely by frequency but by various factors such as bandwidth, modulation schemes, signal processing technology, and multiple-input multiple-output (MIMO) technology.
How do base stations compensate for the drawbacks of radio waves?
As mentioned earlier, while ultra-high-frequency waves are advantageous for transmitting large amounts of data, they have the drawback that as frequency increases, their directionality becomes stronger, meaning signals can be blocked or weakened by obstacles. To overcome this, mobile wireless communications use a method that divides and connects coverage areas using multiple wireless base stations. In other words, by strategically deploying base stations that transmit and receive radio waves within a relatively short range and connecting these base stations via wired or wireless networks to relay information, dead zones in voice and data communications are minimized. Additionally, efforts are made to install base stations and antennas in locations suitable for radio wave transmission to reduce the impact of obstacles along the signal path.
The use of ultra-high-frequency (UHF) waves in mobile wireless communications has also dramatically improved the portability of communication devices. While external antennas were commonly used in early mobile phones, today’s smartphones typically feature antennas built into the device itself. The effective length of an antenna required for efficient radio wave reception is closely related to the wavelength of the radio waves being used; generally, the shorter the wavelength, the smaller the antenna can be designed. As discussed earlier, frequency and wavelength are inversely proportional, and their product is related to the speed of light; therefore, using high frequencies—such as those in the ultra-high frequency (UHF) band—results in very short wavelengths. Consequently, using higher frequency bands enables efficient transmission and reception of radio waves using relatively short antennas, which is advantageous for the design of small communication devices such as smartphones.
How have advancements in mobile communications been linked to changes in frequency?
In the early days of mobile wireless communications, relatively low frequency bands were primarily used; however, as mobile wireless technology advanced, the use of higher frequency bands expanded. In particular, 4G mobile communications utilized various frequency bands—including 700 MHz, 800 MHz, 900 MHz, 1.8 GHz, 2.1 GHz, and 2.6 GHz—while 5G mobile communications rely on the 3.5 GHz band as a key frequency resource. Furthermore, while millimeter-wave bands such as 28 GHz offer very high data transmission capacity, their limited signal range and vulnerability to obstacles impose constraints on their use in actual mobile communication networks. Under South Korea’s 5G frequency policy, both the 3.5 GHz and 28 GHz bands were allocated, with the 3.5 GHz band establishing itself as the core band for the deployment of the nationwide 5G network.
This shift in frequencies is linked to the rapid increase in the volume of data that must be processed in mobile wireless communications. With the widespread adoption of smartphones, mobile networks now provide a variety of services—including not only voice calls but also internet searches, video streaming, and real-time communication—creating a need for greater data transmission capacity. Furthermore, as communication devices have become smaller, the need to efficiently arrange antennas and communication components within limited spaces has grown. While the characteristic that higher frequencies correspond to shorter wavelengths is advantageous for this miniaturization, it simultaneously presents new challenges regarding the range of radio waves and their ability to penetrate obstacles; therefore, multiple factors must be considered when selecting a frequency.
How have radio waves advanced mobile wireless communications?
So far, we’ve started with the definition of electromagnetic waves, explored their types, and, in particular, examined how radio waves are utilized in the field of communications. Among the various types of electromagnetic waves, radio waves possess characteristics suitable for wireless communication, and mobile wireless communication has continued to evolve by leveraging these characteristics. In particular, mobile communication has seen the development of technologies that efficiently utilize frequency and bandwidth to transmit more information faster; at the same time, to compensate for the limited propagation range and vulnerability to obstacles associated with high frequencies, the dense deployment of base stations and various antenna technologies have also advanced.
Moving forward, mobile wireless communications will continue to utilize new frequency bands and communication technologies as the volume of data and the variety of services demanded by users increase. For 5G, the potential for utilizing not only mid-bands such as 3.5 GHz but also higher frequency bands has already been explored, and the efficient utilization of frequency resources, taking their characteristics into account, remains a key challenge for future mobile communication technologies. Ultimately, an understanding of electromagnetic waves and radio waves is a crucial starting point for comprehending the evolution of mobile wireless communications, and the physical characteristics of radio waves and the advancement of communication technologies are expected to remain closely intertwined in the future.
