What is mm wave and how does it fit into 5G?

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‘Extremely high frequency’ means extremely fast 5G speeds

Millimeter wave spectrum is the band of spectrum between 30 GHz and 300 GHz. Wedged between microwave and infrared waves, this spectrum can be used for high-speed wireless communications as seen with the latest 802.11ad Wi-Fi standard (operating at 60 GHz). It is being considered by standards organization, the Federal Communications Commission and researchers as the way to bring “5G” into the future by allocating more bandwidth to deliver faster, higher-quality video, and multimedia content and services.

Earlier this year, Ted Rappaport, founding director of NYU Wireless, said mobile data traffic is projected to rise 53% each year into the “foreseeable future,” and over the last 40 years, computer clock speeds and memory sizes rose by as much as six orders of magnitude. We need higher frequency spectrum to accommodate the increases in data usage, and one of the greatest and most important uses of millimeter waves is in transmitting large amounts of data.

Today, mm wave frequencies are being utilized for applications such as streaming high-resolution video indoors. Traditionally, these higher frequencies were not strong enough for outdoor broadband applications due to high propagation loss and susceptibility to blockage from buildings as well as absorption from rain drops. These problems made mm wave difficult for mobile broadband.

Too good to be true?

High frequency means narrow wavelengths, and for mm waves that sits in the range of 1 millimeter to 10 millimeters. It’s strength can be reduced due to vulnerabilities against gases, rain and humidity absorption. And to make matters even less appealing, due to those factors millimeter wavelengths only reach out to a few kilometers.

Just a few years ago mm wave was not being put to use because few electronic components could receive millimeter waves. Now, thanks to new technologies, it is on the brink of being an integral part of the next-generation network.

The solutions

Thankfully, the same characteristics that make mmWave so difficult to implement can be used to combat its shortcomings.
Short transmission paths and high propagation losses allows for spectrum reuse by limiting the amount of interference between adjacent cells, according to Robert Heath, professor in the department of electrical and computer engineering at The University of Texas at Austin. In addition, where longer paths are desired, the extremely short wavelengths of mm wave signals make it feasible for very small antennas to concentrate signals into highly focused beams with enough gain to overcome propagation losses. The short wavelengths of mm wave signals also make it possible to build multi-element, dynamic beamforming antennas that will be small enough to fit into handsets.

How mm wave spectrum is being handled

Last October, the FCC proposed new rules for wireless broadband in wireless frequencies above 24 GHz. According to the government organization, these proposed rules “are an opportunity to move forward on creating a regulatory environment in which these emerging next-generation mobile technologies – such as so-called 5G mobile service – can potentially take hold and deliver benefits to consumers, businesses and the U.S. economy.”
According to the FCC, the organization is “taking steps to unlock the mobile broadband and unlicensed potential of spectrum at the frontier above 24 GHz.”
Service operators have begun investigating mm wave technology to evaluate the best candidate frequencies for use in mobile applications. The International Telecommunication Union and 3GPP have aligned on a plan for two phases of research for 5G standards. The first phase, set to conclude in September 2018, defines a period of research for frequencies less than 40 GHz to address the more urgent subset of the commercial needs. The second phase is slated to begin in 2018, and complete in December 2019, to address the KPIs outlined by IMT 2020. This second phase focuses on frequencies up to 100 GHz, according to National Instruments.
In an report titled “Millimeter wave for 5G: Unifying Communication and Sensing,” Xinyu Zhang, assistant professor of the electrical and computer engineering at the University of Wisconsin, detailed the mm wave bands being considered:

• 57 GHz to 64 GHz unlicensed.
• Seven gigahertz in total 28 GHz/38 GHz licensed but underutilized.
• Three gigahertz in total 71 GHz/81 GHz/92 GHz Light-licensed band: 12.9 gigahertz in total.

The ITU released a list of proposed globally viable frequencies between 24 GHz and 86 GHz after the most recent World Radiocommunications Conference:
24.25–27.5 GHz                                        31.8–33.4 GHz
37–40.5 GHz                                             40.5–42.5 GHz
45.5–50.2 GHz                                           50.4–52.6 GHz
66–76 GHz                                                      81–86 GHz
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