The Unlicensed National Information Infrastructure band (U-NII) is part of the 5 GHz RF spectrum used by IEEE 802.11 and its amendments.

The Wi-Fi widely available in the standard 2 and 5 GHz bands is being polluted with devices. Reportedly, some cable and DSL Wi-Fi systems providers are activating the Wi-Fi in their system’s modems for other subscriber’s mobile access. Many cable and DSL Wi-Fi modems and other consumer 5 GHz devices operate in the 5.180 to 5.240 band. There are however, some new 5 GHz options for unlicensed professional applications, such as IP video links that make professional links possible and practical.

Basic 5 GHz Wi-Fi is also known as U-NII-1, or as U-NII Low or U-NII Indoor. It provides 80 MHz of unlicensed spectrum for everyone, from 5.150 to 5.250 GHz. It was first limited to 50 mW with an integrated antenna for indoor-only use, and highly populated with Wi-Fi modems and local home WAN devices.

In 2014, the FCC U-NII-1 rules changed to allow up to 4 watts ERP (+36 dBm) for point-to-multipoint and up to 200 watts (+53 dBm) for point-to-point. Although the higher power may have to be limited due to out-of-band radiation, U-NII-1 has several high bandwidth channels available in the USA. However, finding reliable, interference-free channels in such a congested band in unfamiliar territory can be daunting.

The DFS key

The U-NII-2A band is also known as U-NII Mid, and it occupies 5.250 to 5.350 GHz. Together, the U-NII-1 and U-NII-2A bands share a total 160 MHz. U-NII-2A is intended for indoor and outdoor use. What makes U-NII-2A different is that to use its frequencies, the FCC requires the equipment employ DFS as supported by IEEE 802.11h to avoid weather radar and or military interference.

U-NII-2A Power is limited to 250 mW, but the FCC allows user-installable antennas. New FCC rules called the “New rules” were established in June 2015. It added 160 and 80 MHz channel identifiers and re-enables prohibited DFS channels. The “new rules” apply to all users as of 2 June 2016.

The “new rules” allow the certified DFS feature built into some existing pro Wi-Fi gear, such as some Ubiquiti Networks models, to be unlocked with a registration key. The “new rules” open spectrum virtually unused in most consumer Wi-Fi products to high-bandwidth IP video links.

Author’s note: My crew at the recent Offshore Powerboat World Championship in Englewood, FL was able to unlock the DFS feature in some of our Ubiquity gear to take advantage of the “new rules.” Every year we find more traffic and congestion in the 5 GHz U-NII-1 band. This year, we found and used some clear channels that were new to us and very bandwidth-friendly. There was plenty of room for our target video bandwidths of 15 MHz/IP channel.

-2B and above

U-NII Worldwide, also called U-NII-2C or U-NII-2e uses the 5.470 to 5.725 GHz band. It too requires DFS for radar avoidance. The FCC added the band in 2003 and limits usage of channels which overlap the 5.600 to 5.650 GHz band. 20 and 40 MHz channels are available in the US.

U-NII-3 or U-NII Upper uses 5.725 to 5.850 GHz. Operation of unlicensed systems under Section 15.247 of the FCC’s rules is limited to frequency hopping and digitally modulated systems operating within the 902-928 MHz, 2.4-2.4835 GHz, and 5.725-5.850 GHz bands.

U-NII-3 has 5, 40/20 MHz channels, power is allowed up to one watt, as is a user-installed antenna. It is sometimes called U-NII/ISM due to its overlap in the unlicensed industrial, scientific and medical (ISM) 5.725 to 5.875 GHz band. Because of the overlap, licensed ISM use in this otherwise unlicensed band is relatively unusual.

U-NII-4 or DSRC or ITS band is from 5.850 to 5.925 GHz. Right now, it is only available for amateur radio operators and DSRC ITS.

DSRC

In 1999, the FCC allocated 75 MHz of the 5.9 GHz band for dedicated short-range communications (DSRC). It was specifically intended for short- to medium-range wireless RF channels for vehicular communications. The 2010 802.11p amendment known as Wireless Access in Vehicular Environments (WAVE) specifies WLAN in the Intelligent Transportation Services (ITS) band.

The latest automotive solutions such as vehicle-to-vehicle (V2V), Cooperative Adaptive Cruise Control (CACC) and Electronic toll collection (ETC) use DSRC.

What does DSRC have to do with TV? Hopefully, even more video link candidate spectrum. On October 7, 2016, the Federal Communications Commission Office of Engineering and Technology (OET) issued a Public Notice, announcing a schedule for testing U-NII-4 devices.

Phase I of the Test Plan involves testing at the FCC Laboratory in Columbia, Maryland, for potential of unlicensed national infrastructure (U-NII) devices to share the 5850-5925 MHz frequency band with Dedicated Short Range Communications (DSRC) systems operating under the Intelligent Transportation Service (ITS).

If testing results are as some hope, more relatively unused spectrum may become available. This makes inexpensive unlicensed wireless IP links from a HD broadcast camera with an IP output with an ENG van, bonded cellular device or satellite vehicle even more practical. Fewer cables and less expensive RF links make better live TV.

Cognitive radio

Wi-Fi and DFS are clearing spectrum not only for broadcasters but also for other concepts such as Cognitive radio (CR). CR uses a subset of DFS for dynamic spectrum management (DSM). DSM can be programmed and configured dynamically to use the best wireless channels in its vicinity. It automatically detects available channels and changes its transmission or reception parameters to accomplish the most seamless wireless link in a given spectrum band at a particular location.

Full CR is sometimes called Mitola radio. It examines every possible parameter available in a wireless node or network. Spectrum-Sensing CR does the same but only in the RF spectrum.

Subgroups in Spectrum-Sensing CR include Licensed-Band CR and Unlicensed-Band CR. Within those groups are Spectrum Mobility which allows a user to change spectrum bands, Spectrum Sharing with restricted transmit power in licensed bands, and Sensing-based Spectrum Sharing that automatically restricts transmitter power when a licensed user is sensed on a particular channel.

There are several major areas of CR development including Visible Light Communication (VLC). Not all development areas are active yet. There is much more to CR than space in this article. Suffice to say, CR will be a big part of the future of wide-bandwidth mobile short-haul wireless communication, no matter what bands it uses.

What does U-NII mean to broadcasters?

U-NII rules open the doors for reliable point-to-point Wi-Fi IP links. High-gain antennas are allowed, and DFS and DSM guarantee its success. Figure 2 provides the details.

According to FCC compliance information on the Ubiquiti website, “If transmitting antennas of directional gain greater than 6 dBi are used, both the maximum conducted output power and the peak power spectral density shall be reduced by the amount in dB that the directional gain of the antenna exceeds 6 dBi. However, fixed point-to-point U-NII devices may employ transmitting antennas with directional gain up to 23 dBi without any reduction in the transmitter peak output power or peak power spectral density. For fixed, point-to-point U-NII transmitters that employ a directional antenna gain greater than 23 dBi, a 1 dB reduction in peak transmitter power and peak spectral density for each 1 dB of antenna gain in excess of 23 dBi is required.”

These are the kind of RF link engineering specifications that make broadcast microwave operators and technicians more comfortable working with Wi-Fi.