This blog post will explain why and how frequency has become a key resource in modern communications.
Humans have long been trying to overcome the limitations of time and space and to transmit information. Information was stored on media such as CDs and tapes, overcoming the limitations of time, and radio broadcasts that could be frequently listened to in cars are an example of information delivery that overcame the limitations of space. We call this communication, and the reason why modern wireless communication has been able to make such dramatic progress is thanks to research on the frequency domain. The dictionary definition of frequency is “the number of cycles of a wave that repeats in a given amount of time,” but it has more than that meaning in engineering. Understanding frequency requires mathematical and physical background knowledge, but in this article, we will explain it as simply and intuitively as possible to explore the power and importance of frequency in modern society.
We are basically familiar with the realm of time. Let’s think about a situation where you shout to a friend 100 meters away from the concert hall to deliver some message. In this case, you will be the sender of the information, and your friend will be the receiver, and the message you deliver will be one piece of information. Other sounds that occur at the same time, such as the singer’s singing or the audience’s cheering, are not important to your friend, so they can be seen as noise. This is where the problem of communication in the time domain arises. When there is more than one piece of information at the same time, they can interfere with each other and cancel out the desired information. Just as the sound in a concert venue is too loud to get through to your friend, it is difficult to get the desired information if the receiver is heavily affected by noise. In particular, the farther the communication distance, the weaker the signal strength, and the stronger the noise strength, making this problem even more serious.
To overcome this, scientists applied the method of sending information in the frequency domain. In other words, they provided a new perspective by considering frequency as a variable rather than time. If the sender sends information with meaning in the frequency domain, the receiver can filter out signals of other frequencies through a filter if they know the promised frequency. In the simplest example, the human ear can be seen as a filter. For example, humans cannot recognize sounds outside the audible frequency band of 16 Hz to 20 kHz, such as the ultrasonic waves of dolphins. So how do we create signals that have meaning in the frequency domain? In the case of radio broadcasting, it can be understood as a method of sending information on a sinusoidal wave with a fixed frequency. AM varies the amplitude according to the information, while FM conveys information through frequency changes. This is why, even if broadcasting stations are broadcasting at the same time, the receiver can tune in to the desired channel and listen to only the desired broadcast. The signals converted into the frequency domain are free from interference in the time domain.
However, the same problem can occur in the frequency domain. If multiple pieces of information are transmitted at the same frequency, interference can occur between them, making it difficult for the receiver to receive the desired information. However, the situation changes when a specific user is assigned a frequency. Time is given to everyone equally. In modern communication, speed is important, and it is self-evident to decide whether to send information every second or minute by allocating time or to send information at the same time by allocating frequency. The frequency-based communication method is used in various fields such as radio, TV, and mobile phones.
However, as is always the case in engineering, there is a trade-off relationship. To transmit high-quality signals such as voice or video, starting with simple information, more frequency bands are needed. Therefore, everyone wants to use more frequency bands. The solution is to either increase the available frequencies to infinity or allocate the limited frequencies fairly. However, due to technical limitations, the number of frequencies that can be used is finite, and frequency bands are transformed into resources. The astronomical amounts of money being bid in frequency auctions by telecommunications companies in different countries show the importance of frequencies. Even in the United States, essential resources such as gas and electricity are managed by the private sector, but the government directly manages frequencies. This means that the importance of frequencies goes without saying.
People who are worried about the high cost of calls may think that they can theoretically steal the frequency and make free calls. However, it is better not to try this. One day, people in black suits may suddenly come to you for unauthorized use of the frequency.
