For the most part, 5G wireless networks are powered by a technology known as the millimeter wave (mmWave).
Millimeter waves are electromagnetic radio waves typically defined to lie within the frequency range of 30–300 GHz. The micro wave band is just below the millimeter-wave band and is typically defined to cover the 3–30 GHz range.
Although the available bandwidth of mmWave frequencies is promising, the propagation characteristics are significantly different from microwave frequency bands in terms of path loss, diffraction and blockage, rain attenuation, atmospheric absorption and foliage loss behaviors. In general, the overall loss of mmWave systems is significantly larger than that of microwave systems for a point-to-point link.
These are facts that the major mobile carriers are now dealing with as the 5G rollout takes place across the U.S. On the one hand, mmWaves are necessary to fulfill the 5G promise of nearly zero latency and ultra-fast download speeds. On the other hand, the instability of mmWaves makes its usage a challenge to manage.
Fortunately, the small wavelengths of mmWave frequencies enable large numbers of antenna elements to be deployed in the same form factor thereby providing high spatial processing gains that can theoretically compensate for at least the isotropic path loss. Still, as mmWave systems are equipped with several antennas, a number of computation and implementation challenges arise to maintain the anticipated performance gain of mmWave systems.
This is where the link factor comes in and enabling techniques of mmWave-based 5G networks. The link level performance of the mmWave wireless system depends on a number of factors, including the transmission scheme such as beamforming or multiplexing, the approach to identifying the channel, how to design the transmitted signal waveform structure and access strategies.
One thing for sure, the major carriers are not going to back down from riding the backs of mmWaves a far as they can. Looking at the available mmWave bands in the United States provides a good example of the spectrum that can be utilized for 5G networks. The FCC has made strides toward a commitment of making more spectrum available for 5G and have signaled that more licensed bands will be opened up for use.
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