Understanding the spectrum frequencies for realistic 5G deployment
The recent attention devoted to the 5G mobile communication network derives from the anticipated game-changing benefits. For the common mobile phone user, the most important consequence of 5G is faster speed when compared to the 4G network (or LTE). (The speedup will even be much larger relative to older networks like 3G or 2G.) Using a conservative estimate, we probably should be looking for a speedup of 100 times compared with 4G, especially given the potential technical challenges with 5G. One big benefit of 5G is believed to be its low latency, which is the short delay time between when a mobile device pings the network and when it actually gets a response.
Another expectation of 5G is the potential to resolve the ‘last-mile’ issue. The 5G is also expected to play a major role in Internet of Things (IoT), and in the much anticipated Fourth Industrial Revolution, or Industry 4.0, with applications to smart city, smart industrial software, powering connected cars, and smart homes and buildings.
The humongous promise of 5G explains the global race to lead its deployment, as well as the anxiety in terms of national security. The latter seems to explain why the US, Australia, Japan, and some European countries are excluding Chinese companies from bidding for 5G-related projects. At any rate, the country that wins the 5G race, at least from the standpoint of technology deployment, is not going to be the most innovative. On the other hand, the country with the availability of the correct combination of spectrum frequency bands and the ability and willingness to make contiguous spectrum available to phone carriers in all the required layers, will win the 5G race.
The holy grail of the 5G technology is the spectrum, specifically the radio spectrum, and the available frequency bands within the spectrum. The relevant spectrum, that is, the electromagnetic spectrum, consists of all forms of electromagnetic radiation (emission), each corresponding to a different section, or band, of the spectrum. For example, one band includes emissions that our eardrums use to interpret sound. Another band, the visible light, consists of emissions that our eyes interpret as light, so that our eyes cannot “see” light outside of this specific band.
The electromagnetic radiation (emission) shows up in terms of waves, where you should visualize a wave as simply a sine wave or cosine wave. The length of a wave is called the wavelength, which is in meters. The number of waves per second is called the frequency. The wavelength and frequency are inversely proportional; meaning that high frequency corresponds to low wavelength.
Important components of the electromagnetic spectrum include gamma rays (highest frequency in the spectrum), x rays, ultraviolet rays, visible light, infrared, microwaves, and radio waves (lowest frequency in the spectrum). The radio-waves portion of the electromagnetic spectrum has wavelengths that vary from one millimeter (which is written as 1mm) to 10,000 kilometers (or 10,000 km). The corresponding frequencies are thirty cycles per second (also written as 30 Hertz, or 30 Hz) to 300 Gigahertz (300 GHz). Note that the AM radio waves are transmitted at approximately 1 Mega Hertz (1 MHz), FM at approximately 100 MHz, TV transmission is between 100 MHz and 1 GHz, while microwave transmission takes place between 100 MHz and 300 GHz. (Note that the microwaves are contained in the high frequency bands of the radio wave portion of the electromagnetic spectrum.) The cell phones transmit data roughly within 800 MHz to 1990 MHz. Roughly speaking, 2G and 3G networks use 1800 and 2100 MHz frequencies, respectively. The 4G frequency band goes from 2 to 8 GHz.
The radio spectrum bands can be roughly divided into six: extremely low frequency (ELF), ultralow frequency (ULF), low frequency (LF), medium frequency (MF), ultrahigh frequency (UHF), and extremely high frequency (EHF). A part of the EHF band (30 GHz to 300 GHz) is sometimes referred to as the millimeter band, because its wavelengths range from 1 to 10 millimeter. Wavelengths around this band are referred to as the millimeter waves, or mmWaves. The mmWaves are a popular choice for 5G. The UHF portion (300 MHz to 3 GHz) of the radio waves is also being used for 5G. (This band is additionally used for Bluetooth, cordless phones, GPS, TV broadcasting, and Wi-Fi.)
Note that frequency determines the speed and power of data transmission. Specifically, high frequency means faster speeds and shorter distances that messages (data) can be carried. Conversely, lower frequency means slower speeds and longer distances. The millimeter waves, which are in the high-frequency-band spectrum, can carry lots of data, but the waves are also dissipated more easily by gases in the air, trees, and nearby buildings. Therefore, while they may be quite useful in densely packed networks, they are not able to carry data for long distances (due to the attenuation).
For this reason, different (low, medium, and high frequency) parts of the radio spectrum need to be combined in a network for acceptable 5G performance. In a particular advanced country, the medium-range radio frequencies are in short supply because perhaps they have been used for military purposes. This may undermine the ability of the country to compete effectively in 5G.