With the assistance of the FCC, the major telecom carriers received licenses to operate in the millimeter wave (mmWave) spectrum before embarking on their 5G network build out, which is still several years from completion.
This high band mmWave frequency was chosen as the backbone of the new 5G architecture for a couple of reasons:
- The band was relatively uncongested compared to the lower band frequencies that had become far congested, which negatively impacted transmission speeds and latency.
- The amount of bandwidth available at mmWave frequencies (30 GHz to 300 GHz) is enormous compared to the amount of frequency spectrum used by 4G and previous wireless network technologies. Consequently, the hundreds of megahertz of wireless transmission bandwidth available at center frequencies allows 5G wireless networks to operate with almost zero latency and extremely high data speeds.
Based on communication principles, the maximum signal bandwidth in wireless communication is about 5% of the carrier frequency. Therefore, the higher the carrier frequency, the greater the signal bandwidth.
That’s why, among the millimeter-wave frequencies, 28 GHz and 60 GHz are the most promising frequencies for 5G. The 28 GHz band can provide an available spectrum bandwidth of up to 1 GHz, while each channel in the 60 GHz band can provide an available signal bandwidth of 2 GHz (a total available spectrum of 9 GHz divided between four channels).
The downside of high band mmWave frequencies is that electromagnetic (EM) energy at those higher frequencies suffers a great deal of path loss through the air (especially through air with high humidity) compared to lower-frequency signals with longer wavelengths.
Also there are penetration issues with wwWaves because signals at 24 GHz and above can be absorbed by any objects in their propagating path, such as buildings, trees, even the hand of someone holding the smartphone that’s sending the mmWave signals to a cell site to connect with a listener.
The signal attenuation problem has been a thorny issue for system engineers. So far the top solutions have been spreading out small cell base stations, 20 to 25 per square mile, to go along with beamforming, a kind of radio frequency (RF) management in which an access point makes use of various antennas to transmit the exact same signal.
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