In this blog post, we’ll break down the reasons and importance of why radio frequencies have become a core resource in modern communications.
Humans have long devoted significant effort to overcoming temporal and spatial limitations to transmit information. We overcame temporal limitations by storing information on media such as CDs and tapes, and radio broadcasts—which we often hear in our cars—can be seen as an example of information transmission that overcomes spatial limitations. We call this “communication,” and the reason modern wireless communication has been able to develop so dramatically is thanks to research in the field of frequency. While the dictionary definition of frequency is “the number of cycles of a wave that repeats in a given time,” it holds greater significance in engineering. Although understanding frequency requires mathematical and physical background knowledge, this article aims to explain it as simply and intuitively as possible to explore the power and importance of frequency in modern society.
We are fundamentally familiar with the time domain. Consider a situation where you shout a message to a friend standing 100 meters away at a concert venue. In this scenario, I am the sender transmitting information, my friend is the receiver, and the message I convey constitutes a single piece of information. Other sounds occurring simultaneously—such as the singer’s voice or the audience’s cheers—are irrelevant to my friend and can therefore be regarded as noise. This is precisely where the problem with communication in the time domain arises. When multiple pieces of information exist at the same time, they can interfere with one another, potentially canceling out the desired information. Just as my message might not reach my friend if the noise at the concert is too loud, it becomes difficult for the receiver to obtain the desired information if they are significantly affected by noise. In particular, as the communication distance increases, the signal strength weakens while the relative strength of the noise increases, making this problem even more severe.
To overcome this, scientists developed a method of transmitting information in the frequency domain. In other words, they provided a new perspective by considering frequency as the variable rather than time. If the sender transmits information that carries meaning in the frequency domain, the receiver—provided they know the agreed-upon frequency—can filter out signals of other frequencies using a filter. The simplest example is the human ear, which can be viewed as a filter. For instance, humans cannot perceive sounds outside the audible frequency range of 16 Hz to 20 kHz, such as the ultrasonic sounds of dolphins. So, how are signals with meaning in the frequency domain created? In the case of radio broadcasting, this can be understood as a method of transmitting information by modulating a sine wave with a predetermined frequency. AM modulates the amplitude based on the information, while FM transmits information through frequency changes. This is why, even if multiple stations broadcast simultaneously, the listener can tune in to the desired station and hear only that broadcast. Signals converted to the frequency domain in this way are free from interference in the time domain.
However, the same problem can arise in the frequency domain. If multiple pieces of information are transmitted on the same frequency, they may interfere with each other, making it difficult for the receiver to obtain the desired information. However, the situation changes if specific users are assigned to specific frequencies. This is because time is equally available to everyone. In modern communications, speed is critical, so it is self-evident that we must decide whether to allocate time—sending information every second or minute—or to allocate frequencies to send information simultaneously. Communication methods using frequencies are utilized in various fields, such as radio, TV, and mobile phones.
However, as is always the case in engineering, there is a trade-off. Starting with simple data, transmitting high-quality signals like voice or video requires a wider frequency band. Consequently, everyone wants to use a larger frequency band. The solution lies in either infinitely expanding the available frequency spectrum or allocating the limited spectrum fairly. However, due to technical limitations, the available spectrum is finite, and frequency bands become a resource. The astronomical sums bid in national spectrum auctions by telecommunications companies underscore the importance of spectrum. Even in the United States, where essential resources like gas and electricity are managed by the private sector, the government directly manages the spectrum. This speaks volumes about the importance of spectrum.
People worried about high phone bills might think that, theoretically, they could steal radio frequencies to make free calls. However, it would be best not to attempt this. After all, one day, people in black suits might suddenly show up to arrest you for unauthorized use of radio frequencies.
