Distribution & Delivery Global Viewpoint – February 2019

RF Spectrum Use Meets the Terahertz Gap

The phrase “DC to light” was once a euphemism among broadcast engineers and audiophiles to describe the frequency response of the perfect power amplifier. Today, it’s the real description of usable RF spectrum.

The terahertz gap is the band between radio and infrared, from 100 GHz (0.1 THz) to 10 THz (3 mm to 30 µm). The longest wavelength in the far infrared (FIR) spectrum is 1mm (300 GHz or 0.3 THz). Technologies to effectively radiate terahertz gap band signals and detect them through anything other than the vacuum in space are being researched. Meanwhile on Earth, the march towards 100 GHz of usable RF spectrum is becoming a race.

House RF Experts

Broadcast transmitter engineers are the house RF experts who keep their stations on the air and often oversee nearly everything wireless in station infrastructure, from walkie-talkies and Wi-Fi to BAS microwave systems and STLs. They are always watching for better, faster and more cost-effective ways to accomplish broadcast RF transmission, RF and IP transport, backhaul and communications tasks.

The house RF expert keeps an eye on FCC activities, RF spectrum and other RF-related issues including new RF technologies with the potential to impact station operations. If the house RF expert is you, are you monitoring the progress of 5G? It’s already been launched in a few markets. How will it affect broadcasters?

Big money and profit potential are behind the commercial and military hunger for more spectrum. Demand is driving the technology for an unprecedented expansion of the upper limits of usable RF spectrum. More spectrum benefits telecom carriers and wireless operators because they charge customers to use it.

More spectrum benefits TV broadcasters by providing more space and flexibility for high-quality live video transport. As the spectrum door opens wider for content creators and consumers, TV broadcasters will discover new ways to make more money with it. Let ATSC 3.0 lead the way.

New Radio

The push to expand usable RF spectrum is 5G, aka 5G New Radio, 5G NR and New Radio. The New Radio name appears to be catching on for 5G, as LTE did with 4G. Consider New Radio as fiber-to-the-phone.

Frequency bands for New Radio are in two different frequency ranges. Frequency Range 1 (FR1) starts below the TV UHF band from 450 MHz (the lower edge of Channel 14 is 470 MHz) up to 6 GHz. It was one of the reasons the FCC auctioned the 600 MHz band. Frequency Range 2 (FR2) covers 24.25 GHz (upper-K Band) to 54.6 GHz (mid-V band). Currently FR2 is occupied by Ka Band satellite uplinks, police radar, point-to-point data links and the military.

Spectrum distribution covering new 5G planned allocations.

Spectrum distribution covering new 5G planned allocations.

Above FR2 at 60 GHz is IEEE 802.11ad, aka WiGig or 60 GHz Wi-Fi. WiGig products were certified in 2016 and a 2ndgeneration WiGig IEEE standard is expected in 2019. WiGig uses beamforming and reflects off walls, ceilings and floors. Full body scanners operate at 94 GHz. Atmospheric attenuation makes G Band (110-300 GHz) practical only for satellite-to-satellite communications.

Until New Radio, use of FR2 frequencies has been limited. Millimeter waves are attenuated by the atmosphere and require raw ERP to maintain full OFDM bandwidth even at relatively short distances. The sharply inverse distance/bandwidth relationship dictates the physical need for significantly more New Radio towers and sites with higher ERPs than LTE, blanketing the terrain with high power signals at shortest wavelengths ever broadcast. There are many questions about how powerful millimeter waves may adversely effect of the health and DNA of living things.

New Radio, LTE and Wi-Fi use OFDM modulation. ATSC 3.0 is OFDM, coded with forward error correction and time/frequency interleaving (COFDM), primarily to contend with multipath. OFDM (including COFDM) is the best method known to modulate and transmit maximum data over a bandwidth-limited RF channel.

3GPP

The 3rd Generation Partnership Project is a collaboration between groups of telecommunications standards associations, known as the Organizational Partners (3GPP). 3GPP has adopted the 5G New Radio standard.

Five years ago, 3GPP adopted LTE Broadcast, aka LTE Multicast, based on 3GPP’s evolved Multimedia Broadcast Multicast Service standard. It’s used to distribute the same content to many users simultaneously on a LTE network. For example, when many viewers in a major sports stadium are watching the same stream while watching the game, the LTE Broadcast bandwidth doesn’t change with the number of wireless devices tuned in. Use of LTE Broadcast will expand along with New Radio, particularly for emergency communications and announcements.

3GPP is focused on three primary areas of New Radio. One is enhanced mobile broadband (eMBB) for increased network capacity and higher peak data rates. Another is massive machine type communications (mMTC) for connection density and energy efficiency. The third is ultra-reliable, low latency communications (URLLC).

In 2015, 3GPP release 13 adopted License Assisted Access (LAA) as part of LTE Advanced Pro. LTE LAA uses carrier aggregation in the downlink to combine LTE in the unlicensed 5 GHz Wi-Fi band with LTE in the licensed band to provide better data rates and improved QoS and QoE.

LAA uses Listen-before-talk (LBT) to find and select unused channels in the 5 GHz band. If there is no clear channel available, LAA can share a channel. The telecommunication industry considers LAA a major milestone on the road to New Radio. LAA also increases Wi-Fi traffic and the need for more Wi-Fi channels.

Low Band (Sub 1 GHz) – Coverage Layer,
High Bands (1 GHz to 6 GHz) – Capacity Layer,
Very High Bands (Above 6 GHz and mmWave) – High Throughput Hotspots
Click to enlarge. Image: Ofcom">

5G will work from the lower frequency bands up to very high frequencies where large chunks of bandwidth are available. This is what will enable 5G to provide high throughput speeds and makes it different from 4G/LTE. Example divisions:
Low Band (Sub 1 GHz) – Coverage Layer,
High Bands (1 GHz to 6 GHz) – Capacity Layer,
Very High Bands (Above 6 GHz and mmWave) – High Throughput Hotspots
Click to enlarge. Image: Ofcom

High Wi-Fi Coming

The FCC recently moved to make up to 1200 MHz of spectrum available for use by unlicensed devices in the 6 GHz band (5.925-7.125 GHz). The commission granted Qualcomm an Experimental Special Temporary Authorization to perform 6 GHz building attenuation measurements in San Diego, in support of pending FCC rulemaking.

According to the 17 December 2018 Federal Register, “The Commission proposes to make the 5.925–6.425 GHz and 6.525–6.875 GHz bands, referenced as the U–NII–5 and U–NII–7 bands respectively, available for unlicensed operations under rules consistent with the existing rules for unlicensed device operations in the nearby U–NII–1 and U–NII–3 bands (5.150–5.250 GHz and 5.725–5.850 GHz bands, respectively).”

The U–NII–5 and U– NII–7 bands are heavily used for point- to-point fixed links, which support a variety of critical services. Some U–NII– 5 and U–NII–7 frequencies are also allocated to the fixed-satellite service. The proposed framework for U– NII–5 and U–NII–7 prohibits unlicensed devices from operating co-channel with any fixed link within that link’s defined exclusion zone.

The FCC is seeking comments on the 6 GHz band until 15 February 2019. Note that the band includes U– NII–5 and U–NII–7 but only the lowest 75 MHz of the 6 GHz band is in New Radio’s FR1 band. 6 GHz will be the ‘next big thing’ in Wi-Fi.

Broadcasting and wireless telecommunications are simultaneously moving into separate uncharted territories in the same markets. How New Radio will fit with ATSC 3.0, or vice-versa, remains a mystery. As both new technologies roll out, each will monitor TV audience viewing trends and react accordingly.

Broadcasters have learned that sponsors pay for eyeballs, not gee-whiz factors. The elephant in the room is content. At this early 2019 stage, virtually zero US consumers have an ATSC 3.0 TV or a New Radio device. Mark this month as the last time that's likely to be true.

Commenting is not available in this channel entry.

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