It’s been 6 months since the FCC opened up the 6GHz band for unlicensed use and still the focus is on the value of ‘more bandwidth’, a tremendous value, but not the end-all of 6E. What is overlooked are the additional technology advances and advantages that are part of 6E, including new power levels, different device types, efficient Out-of-Band (OOB) Discovery, and AFC. No, not the old automatic frequency control, but new Automatic Frequency Coordination; think an arbitrator designed to make sure Wi-Fi 6E doesn’t interfere with existing 6GHz incumbents.
Starting with new device types, today most see Wi-Fi as only two (2) types of devices, access points (APs) and clients (phones, tablets, etc.). With 6GHz, we have some additional choices and they are based on the power levels allowed. Once again this has mostly to do FCC regulations associated with avoiding potential interference with existing 6GHz incumbents. The choices now are standard power APs, Low Power Indoor (LPI) APs, and even discussion around Very Low Power (VLP) Mobile APs.
So, let’s start with the Low Power Indoor APs as those will be the first to appear. The FCC has authorized the entire 6 GHz band (1200 MHz) for indoor use, these new Low Power Indoor AP device-class will be allowed to transmit indoors only with a maximum EIRP of 30 dBm, clients connecting to these APs are limited to a maximum EIRP of 24 dBm. The FCC also requires that all low-power devices incorporate permanently attached integrated antennas to prevent the potential for users to replace a device’s antenna with a higher gain antenna and the potential for interference.
Next are the standard-power APs and they will primarily be used to support outdoor communications in a subset of the 6GHz band, specifically U-NII-5 and U-NII-7 bands. The maximum EIRP for a standard-power AP will higher, at 36 dBm to support the greater distances typically required for outdoor operation. However, this also increases the chances of 6E interfering with existing users of the 6GHz band, the incumbents. To address this the FCC has mandated spectrum management services be used to protect the licensed incumbent fixed services. So prior to transmitting, a standard-power access point must consult a database to ensure non-interference. This is the new AFC system and will be discussed below.
As a final device type, the VLP APs, this is mainly focused on allowing the use of 6 GHz Wi-Fi in cars, trains, and other transportation verticals. However, this is still in discussion and nothing has been defined at this time.
Ok, back to standard power APs and the requirement for the use of automatic frequency coordination (AFC). So what is AFCs job – For outdoor Wi-Fi communications in the U-NII-5 and U-NII-7 bands, the FCC mandates the use of AFC which is a geolocation database that manages real-time frequency assignments to protect incumbent operations from RF interference. Prior to transmitting, a standard-power access point will consult a local AFC system a list of permissible frequencies or a list of prohibited frequencies on which it cannot transmit. The AFC system will identify the geographic coordinates of the access point, nearby incumbent 6GHz operation, channel/power usage, and will automatically check for possible interference. If there is an incumbent 6GHz operation nearby, an AFC protection contour will be enforced on the standard-power Wi-Fi AP. In simpler words, the AP may not be allowed to transmit or may be required to lower transmit power well below 36 dBm to avoid interference with the incumbent. If there are no nearby incumbents in the area, the AP can transmit on available channels. Note this type of function is not new Whitespace and CBRS use a similar system to allocated available channels.
Ok, so the previous sections discussed the new types of devices and deployment considerations, but we have APs operating on 3 bands, 2.4Ghz, 5GHz & 6 GHz with a potential total of over 85 possible channels to roam between. Imagine the issues and inefficiencies as a client (your phone) seeks another AP to connect to as you walk across the campus. In theory, it would need to probe all potential channels for a next-hop roam, not good, but since Wi-Fi 6 is all about efficiency so you could imaging Wi-Fi 6E would have thought this thorough a little, and they did. This is where we get something called out-of-band discovery, one-note, it’s actually not new, 802,11v standardized this years ago. With Wi-Fi 6E the APS will essentially track all the SSIDs supported by its radios and reply with this additional information allowing the client device to select the next AP/radio to connect to without an extensive search across all bands and channels. Simply put – a client, preparing to roam will ‘probe’ for APs that support their same SSID, all APs in-range will respond on the same band (I.e. 5GHz) and identify what channels they are supporting that SSID on, additionally the probe response will include additional information about other radios supporting that same SSID across other bands (I.e. 6GHz and 2.4GHz), this now provides the client with All potential information to make the best roaming decision.
Hopefully, this was information was useful and if it piqued your interest for a deeper dive into these capabilities please attend my upcoming session on this topic during the Wi-Fi NOW Virtual Wi-Fi World Congress