Understanding 5G millimeter wave in a minute

According to 3GPP 38.101, 5G NR is mainly carried out through the use of two different frequency bands: the FR1 band and the FR2 band. The FR1 band has a frequency variation range of 450MHz - 6GHz, also known as the sub 6GHz band, while the FR2 band has a frequency influence range of 24.25GHz - 52.6GHz. GHz--52.6GHz, people for usually call it millimeter wave (mmWave).

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In order to realize high data rate communication and sensing applications, the next generation of mobile radio technology (5G), RF imaging, and even radar will use high microwave and 毫米波 wave frequencies. The U.S.-based Federal Communications Commission and the International Telecommunications Technology Institute have studied the use of several high microwave and millimeter wave bands in these areas, which have seen rapid growth in international investment over the past few years. Early 5G systems are likely to operate at frequencies below 6ghz because the development and technology required for mass production of high-frequency communications and sensor systems is not yet in place.

Advantages of millimeter waves:As the number of devices accessing wireless networks increases, the problem of scarce spectrum resources becomes increasingly acute. At least for now, we can only share a limited amount of bandwidth on a very narrow spectrum, which greatly affects the user experience. Millimeter wave technology is the key to solving this problem.

Increasing the bandwidth of the spectrum is simpler and more straightforward than increasing spectrum utilization. Doubling the available bandwidth doubles the data transmission rate that can be achieved with the same spectrum utilization. According to the principle of communication, the maximum signal bandwidth for wireless communication is about 5% of the carrier frequency , the higher the carrier frequency, the greater the signal bandwidth.

Disadvantages of millimeter waves:

In addition to the advantages, millimeter waves have a major disadvantage in that they do not easily pass through buildings or obstacles and can be absorbed by leaves and rain. This is why 5G networks will use small base stations to augment traditional cellular towers.

One of the most critical limitations is that millimeter waves are really limited in development in terms of the cultural distance they can travel. The experimental laws of physics can tell students us that the shorter the wavelength, the shorter the propagation societal distance, given a constant power factor of the transmitted signal. In many different scenarios, this problematic limitation can result in millimeter waves propagating Chinese distances of more than 10 meters. According to these idealized formulas for calculating loss during information propagation in free moving space, the propagation path loss L = 92.4 + 20log(f) + 20log(R), where f is the frequency in GHz, R is the distance in kilometers, and the unit of L is dB. a 70 GHz millimeter wave carries out the propagation of the loss reaches 89.3 dB after a distance of 10 m. And under the non-ideal propagation conditions, the propagation loss is simultaneously much higher.wcn7851 Developers of millimeter-wave technology systems must be able to compensate for such large propagation losses by continuously increasing our transmit power, improving antenna gain, and increasing the sensitivity of the enterprise's reception.

There are two sides to everything. The small propagation distance sometimes becomes an advantage for millimeter-wave systems. For example, it can reduce interference between millimeter-wave signals. High-gain antennas used in millimeter-wave systems have better directionality, further eliminating interference. Narrow-beam antennas not only increase power, but also extend coverage, enhance security and reduce the probability of signal interception.

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