In the past 20 years, Wi-Fi technology has been used in 2.4 GHz (2.4-2.4835 GHz) and 5 GHz (5.15-5.35 GHz & 5.47-5.85 GHz) frequency bands for a long time. This situation has not been broken by Wi-Fi 6E (5.925-7.125 GHz) frequency band until recent years. As the first country to adopted the Wi-Fi 6E band, the FCC did not stop there, but chose to pursue the victory. In November 2020, it voted to adopt a new rule: expand the UNII band from 5.85 GHz to 5.895 GHz (UNII-4), so that unlicensed services such as Wi-Fi can be used in the new 45 MHz band. Previously, the spectrum from 5.85-5.925 GHz was designated for Intelligent Transportation System (ITS) operations under Part 90 and Part 95.

The KDB 291074 draft guidance for 5.9 GHz (UNII-4) devices was released on November 9, 2021. Just a few days ago, the official version of KDB was finally released on March 3, 2022. 

Here is the interpretation of relevant regulations:

UNII Bands ->->->->->->->->->->->->->->->->

As shown in the figure above, the UNII band of FCC at this stage is divided into:

● Wi-Fi 5 GHz：

　○ UNII-1：5.15-5.25 GHz

　○ UNII-2A：5.25-5.35 GHz

　○ UNII-2C：5.47-5.725 GHz

　○ UNII-3：5.725-5.85 GHz

● Wi-Fi 5.9 GHz（new）：

　○ UNII-4：5.85-5.895 GHz

● Wi-Fi 6E：

　○ UNII-5：5.925-6.425 GHz

　○ UNII-6：6.425-6.525 GHz

　○ UNII-7：6.525-6.875 GHz

　○ UNII-8：6.875-7.125 GHz

Channel & Frequency ->->->->->->->->->->->->->->->->

Since the UNII-4 band is close to the UNII-3 band, in addition to the channels only falling in the UNII-4 band, some channels span UNII-3 and UNII-4:

Types of Devices ->->->->->->->->->->->->->->->->

Devices operating in the U-NII-4 Band and channels that span U-NII-3 and U-NII-4 Bands are restricted to three category types:

Test Items ->->->->->->->->->->->->->->->->

FCC Wi-Fi 5.9 GHz UNII-4 / UNII-3 & UNII-4 equipment needs to perform the following test items:

For item 7 unwanted emission, the limits of harmonics above 1 GHz and band edge are as follows:

● Harmonics (Consistent with Wi-Fi 6E):

　○ In the Restricted Bands: 74 dBμV/m (Peak) & 54 dBμV/m (AVG)

　○ Outside of the Restricted Bands: 88.2 dBμV/m (Peak) & 68.2 dBμV/m (AVG)

● Band Edge (The limit below 5.725 GHz in the left band edge is consistent with the UNII-3 band edge):

　○ Left Band Edge：all emissions below 5.725 GHz shall not exceed an e.i.r.p. of −27 dBm/MHz (68.2 dBμV/m，Peak) at 5.65 GHz increasing linearly to 10 dBm/MHz (105.2 dBμV/m，Peak) at 5.7 GHz, and from 5.7 GHz increasing linearly to a level of 15.6 dBm/MHz (110.8 dBμV/m，Peak) at 5.72 GHz, and from 5.72 GHz increasing linearly to a level of 27 dBm/MHz (122.2 dBμV/m，Peak) at 5.725 GHz. As illustrated in Figure 1 below

　○ Right Band Edge：For an indoor access point or subordinate device, all emissions at or above 5.895 GHz shall not exceed an e.i.r.p. of 15 dBm/MHz (110.2 dBμV/m，AVG) and shall decrease linearly to an e.i.r.p. of −7 dBm/MHz (88.2 dBμV/m，AVG) at or above 5.925 GHz; 

Or For a client device, all emissions at or above 5.895 GHz shall not exceed an e.i.r.p. of −5 dBm/MHz (90.2 dBμV/m，AVG) and shall decrease linearly to an e.i.r.p. of −27 dBm/MHz (68.2 dBμV/m，AVG) at or above 5.925 GHz. As illustrated in Figure 1 below, the peak emissions must be limited to no more than 20 dB above the average limit

Just in February this year, ISED of Canada also publicly consulted on "the Technical and Policy Framework for Radio Local Area Network (RLAN) Devices in the 5850-5895 MHz Frequency Band and for Intelligent Transportation Systems (ITS) in the 5895-5925 MHz Frequency Band", and the closing date for comments was April 29, 2022. Then ISED replied to the comments of all parties, and the closing date for reply comments was June 3, 2022. It is expected that ISED will release new rules after this date. Please look forward to it.