![]() received spectrum from the FCC, it was granted as an experiment in coexistence to align the U.S. The last time Wi-Fi technologies in the U.S. In April 2020, 35 years into this “experiment in unlicensed use,” a single announcement gave Wi-Fi 1200 MHz of spectrum, more than doubling the current Wi-Fi spectrum allocated in the U.S. Wi-Fi’s capabilities have also grown, and as a result, its use in the 2.4 and 5 GHz bands has reach its limits. Wi-Fi has steadily grown in popularity and provides demonstrable economic benefit. This spectrum accrual took place in multiple separate grants over the years. beginnings in 1985 all the way to the present, Wi-Fi has been granted a total of just 583 MHz of spectrum in both the 2.4 and 5 GHz bands combined. This announcement is a good thing, and arguably one of the best things to happen in Wi-Fi since Wi-Fi 6 and Orthogonal Frequency-Division Multiple Access (OFDMA) came about.įor some perspective on why this is such a milestone event for Wi-Fi, it should be noted that from its U.S. There are many more factors in wifi, of course( managed vs unmanaged interference, the range of the wireless clients, other interference, etc), but this question was specifically about the signal threshold for co-channel interference, so the most specific answer is Cisco's "-85 dBm threshold".In April 2020 the Federal Communications Commission (FCC) announced the opening of the 6 GHz band for Wi-Fi and other unlicensed uses. Ron's other comment of using -87 dBm as a threshold for same-channel signals at the perimeter of the network is a more-restrictive answer than Cisco's, but would certainly result in a clearer network if it's possible to achieve. Ron's answer of "If two wireless stations can hear each other well enough to identify 802.11 traffic, then they cause co-channel interference" is also valid, but a signal level is a more specific answer to the question. Specifically:Īt least -85 dBm should be considered the signal strength threshold for CCA (from Cisco's Wireless LAN planning guide, page 14) The answer appears to be that low signal may mean low co-channel interference, but only for very low signal. And I've somehow never come across what that is! If that's false, then there must be a minimum signal amount required for co-channel interference. If two AP's can hear each other, regardless of how clearly, they compete for airtime. If that's true, then the various online guides for wifi placement that make it seem as those "low signal" = "low co-channel interference" are just wrong (see Netspot's guide as an example). Each AP must compete for the same airtime, so activity in either network will necessarily degrade the performance in both networks. If you use something like tcpdump, you'd see a high number of corrupted frames from the other network's AP, but you'd still see the frames.įrom what I've gathered about this situation, this should cause co-channel interference between the APs (again, please ignore the clients). ![]() ![]() For both APs, the noise level is also low, -92 or less.Įven with the poor signal, most of the traffic from the other network's AP can be heard. ![]() Any traffic picked up from the other network only has signal strength of -80 or less. Let's ignore the client signal ranges for this question to keep it simple. The AP in each network can just barely hear the AP in the other network. Say there are two different 5Ghz networks on channel 36. Is a minimum SNR required for co-channel interference? While I've fixed my specific problems, I still have a lingering question about co-channel interference. I recently worked through a series of wifi issues and had to learn a bit in the process. ![]()
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