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Millimeter wave spectrum has key role in 802.11ay wireless

IEEE 802.11ay Wi-Fi is getting closer to final ratification. The new standard relies on millimeter wave spectrum to deliver stronger and more robust services.

In concept, wireless is simple. Just generate an electromagnetic carrier wave occupying designated bandwidth at a particular frequency, modulate, or encode, the information you want to send on the wave, amplify the signal, apply it to an antenna and off it goes into the ether.

In reality, the technology is complex and involves math that only a graduate student in physics or electrical engineering could understand.

For our purposes, let's focus on wireless broadband communications -- specifically the millimeter wave spectrum frequency underlying next-generation IEEE 802.11ay wireless.

Frequency is also a simple concept. It tells us how fast a given wave vibrates. We need an electronic device called an oscillator to create the wave -- a technology that goes back more than 100 years. But the higher the frequency, the more  complex the electronics in that oscillator become. Advances in basic circuitry and semiconductor manufacturing processes over the past 20 years have enabled low-cost, highly reliable, very-high-frequency oscillators that offer excellent performance.

This means we can now produce highly reliable, low-cost, high-performance radios that operate in what used to be the exotic domain of millimeter wave. This band of spectrum between 30 GHz and 300 GHz got its name because the wavelengths -- the physical distance between a given peak of a wave and the peak following it -- range from about 10 mm to less than 1 mm. This undeveloped band of spectrum can be used in a variety of products and services, including point-to-point wireless LANs and broadband access.

Millimeter wave spectrum is also being used for a variety of services on mobile networks, because it allows for data rates up to 10 Gbps and it will underpin IEEE 802.11ay, which promises to deliver even faster and longer-range Wi-Fi services.

Millimeter wave challenges and their impact on IEEE 802.11ay

We can now cost-effectively access these high frequencies, but two big issues remain.

The first covers country-specific regulations. Regulations for radio transmissions vary because countries put policies in place that make the best use of spectrum within their political boundaries. A lot of spectrum is licensed and increasingly made available via auctions, which is typically where cellular carriers operate. Unlicensed spectrum is still regulated and has restrictions on transmit power and other elements, but it is made available directly to end users. This is the domain of Wi-Fi, Bluetooth and many other low-power technologies.

While much of the millimeter wave spectrum is licensed, a portion around the 60 GHz spectrum -- measuring 7 GHz to 9 GHz -- is not. That's a lot of landscape, especially compared to the 1 GHz of spectrum otherwise available to Wi-Fi and the paltry 100 MHz to 200 MHz of spectrum typically owned by a cellular carrier in a given location. The bottom line is millimeter waves can enable serious wireless broadband. This is also true for the licensed millimeter wave bands, as well.

The second challenge comes from the attenuation -- that is, loss of signal strength -- that occurs in the millimeter wave spectrum at 60 GHz. Oxygen quickly absorbs 60 GHz signals, which limits their range. But the news isn't all bad. Gigabit-class signals can be sent at 60 GHz for 1 km, while still meeting the regulations required for unlicensed use.

In addition, signals at 60 GHz are quite directional, but this can be beneficial in many cases. Using sophisticated and low-cost antenna techniques, signal processing and the development of the IEEE 802.11ay wireless standard, engineers can compensate for 60 GHz directional signals.

The promise of IEEE 802.11ay

Because hardware costs are falling as traffic demands increase, we expect interest in 60 GHz applications to grow rapidly. For example, the Wi-Fi 802.11ad standard for 60 GHz spectrum has been completed for some time and promises Wi-Fi broadband throughput up to about 10 Gbps. With a projected release in late 2019, IEEE 802.11ay  is expected to increase bandwidth and improve the reliability of unlicensed 60 GHz millimeter wave spectrum. It's possible the technology could support speeds as high as 100 Gbps and reach distances of about 1,000 feet.

We also expect to see increased deployments of fixed millimeter wave products for campus and metro-scale applications, like video surveillance, smart cities and even basic internet access -- think 5G. Cellular carriers adopting millimeter wave are expected to interconnect cells for wireless backhaul purposes -- a case where licensed spectrum owners use unlicensed spectrum to interconnect cells.

Fixed millimeter wave designs can support point-to-point, point-to-multipoint, star and even full-mesh implementations that can provide unlimited coverage and cost-effective growth. The uses for millimeter wave spectrum are rapidly evolving. In the future, we might even see this technology used to replace wireline networks, giving enterprises an entirely new way to deploy wireless communications.

This was last published in March 2018

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