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Wi is Fi: Understanding Wi-Fi 4/5/6/6E/7/8 (802.11 n/AC/ax/be/bn)

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Re: Wi is Fi: Understanding Wi-Fi 4/5/6/6E/7/8 (802.11 n/AC/ax/be/bn)

#71

Post by throw0101a »

niobe wrote: post #14

An impressive attempt to summarise Wi-Fi which is a very deep topic. However I think the executive summary already missed the most critical thing about Wi-Fi: only 1 transmitter at a time per channel - across all WLANs, yours and your neighbours, with no deterministic way to avoid collisions. It's a shared medium and it's not even half duplex, unlike the dedicated full duplex you would typically get with an ethernet…

> only 1 transmitter at a time per channel - across all WLANs, yours and your neighbours, with no deterministic way to avoid collisions.

Not true with newer standards:

> Orthogonal Frequency-Division Multiple Access (OFDMA) is a multi-user wireless transmission technology that divides a single Wi-Fi or cellular channel into smaller subcarriers called Resource Units (RUs), allowing multiple devices to transmit data simultaneously.

[…]

> Instead of one device occupying the entire channel (as in OFDM), OFDMA allows parallel transmissions. As a result, network congestion decreases significantly.

* https://www.netcomlearning.com/blog/what-is-ofdma

* https://airheads.hpe.com/blogs/antar1/2020/10/19/why-is-ofdm...

> In addition, the 802.11ax standard defines the smallest subchannel as a resource unit (RU), which includes at least 26 subcarriers and uniquely identifies a user. The resources of the entire channel are divided into small RUs with fixed sizes. In this mode, user data is carried on each RU. Therefore, on the total time-frequency resources, multiple users may simultaneously send data in each time segment, as shown in the following figure.

* https://info.support.huawei.com/info-finder/encyclopedia/en/...

* https://blogs.cisco.com/networking/wi-fi-6-ofdma-resource-un...

With a 26-Tone RU Type, nine devices can operate simultaneous in even a 20 MHz channel (eighteen in 40 MHz, etc); see Figures 2 and 3:

* https://www.mpirical.com/knowledge-base/wi-fi-6-and-ofdma

Re: Wi is Fi: Understanding Wi-Fi 4/5/6/6E/7/8 (802.11 n/AC/ax/be/bn)

#72

Post by throw0101a »

ksec wrote: post #57
9x39 wrote: post #38

Earlier quoted context omitted.

The multi access story is improving, though. OFDMA on wifi7/802.11be: https://blogs.cisco.com/networking/wi-fi-7-mru-ofdma-turning...

It is not even switched on in some early version of WiFi 7 router and receivers. As a general rule of thumb, the best version of WiFi x will only come with WiFi x+1. So for all the problems to be solved and ironed out on OFDMA it will be WiFi 8 then. And for all the promises of Ultra-High Reliability, it will have to be WIFI 9. WiFi is clearly moving more towards like 4G and 5G with every version. I just hope someday…

> It is not even switched on in some early version of WiFi 7 router and receivers.

OFDMA was first used with Wifi 6:

* https://blogs.cisco.com/networking/wi-fi-6-ofdma-resource-un...

* https://www.litepoint.com/blog/wi-fi-6-ofdma/

Re: Wi is Fi: Understanding Wi-Fi 4/5/6/6E/7/8 (802.11 n/AC/ax/be/bn)

#73

Post by mbesto »

It seems the throughput has evolved over each spec but the reliability and distance hasn't, unless I'm mistaken? This is a big problem in place where concrete is used to build homes (e.g. the tropics) as the improvements to Wifi are basically not really relevant.

Re: Wi is Fi: Understanding Wi-Fi 4/5/6/6E/7/8 (802.11 n/AC/ax/be/bn)

#74

Post by mallets »

rayiner wrote: post #34
niobe wrote: post #14

An impressive attempt to summarise Wi-Fi which is a very deep topic. However I think the executive summary already missed the most critical thing about Wi-Fi: only 1 transmitter at a time per channel - across all WLANs, yours and your neighbours, with no deterministic way to avoid collisions. It's a shared medium and it's not even half duplex, unlike the dedicated full duplex you would typically get with an ethernet…

> only 1 transmitter at a time per channel - across all WLANs, yours and your neighbours, with no deterministic way to avoid collisions. That’s not correct. You and your neighbor can use the same channel at the same time. On your network, the transmissions of the other network appear will appear as noise. As long as the other devices are far enough away, however, your devices will still be able to make out their own…

Only if the difference in signal power is high (>40 dB). It’s like saying collisions aren’t a problem in situations where no collision actually occurs.

Re: Wi is Fi: Understanding Wi-Fi 4/5/6/6E/7/8 (802.11 n/AC/ax/be/bn)

#75

Post by ssl-3 »

throw0101a wrote: post #69
ssl-3 wrote: post #36

Earlier quoted context omitted.

In regulatory regions where it is usable, Wifi 6 (802.11ax) added some 6GHz channels. Wifi 6e extended that to roughly the entire 6GHz band, for ~1GHz of contiguous RF bandwidth in that area alone. The "old" cellular bands aren't generally open, at least in the States. We tend to use them for newer licensed stuff in cellular-land instead of the old licensed stuff we used to do. (Old modulation techniques die out and…

> In regulatory regions where it is usable, Wifi 6 (802.11ax) added some 6GHz channels. 'Plain' Wifi 6 (non-E) had zero 6 GHz. If you think otherwise can you produce a citation? Edit: * https://en.wikipedia.org/wiki/List_of_WLAN_channels

You're right. 6GHz wasn't usable as a part of standardized wifi until 6e.

I'd like to choose option C: I thought otherwise, and I was wrong in thinking that. I'd like to submit my previous comment, just above, as a citation demonstrating the incorrect thought process. ;)

Re: Wi is Fi: Understanding Wi-Fi 4/5/6/6E/7/8 (802.11 n/AC/ax/be/bn)

#76

Post by ipython »

mbesto wrote: post #73

It seems the throughput has evolved over each spec but the reliability and distance hasn't, unless I'm mistaken? This is a big problem in place where concrete is used to build homes (e.g. the tropics) as the improvements to Wifi are basically not really relevant.

At some point, you just can’t beat physics. For best results you need multiple aps anyway.

Re: Wi is Fi: Understanding Wi-Fi 4/5/6/6E/7/8 (802.11 n/AC/ax/be/bn)

#77

Post by Normal_gaussian »

izacus wrote: post #63
Normal_gaussian wrote: post #28

Today I set up a NWA210BE (Zyxel) to replace a unifi 6+ AP; I bought it second hand and my key metrics were: 4x4 MIMO, available used/discounted, current gen, fully functional standalone mode. The 4x4 makes all the difference. Sitting in my car the 6+ would fight with my 4G for internet and cause maps to be super slow; now I'm off the property before its unusable. I had intended to put APs in multiple rooms, but ther…

What benefit does 4x4 give you? I haven't seen a single client station with more than 1x1 or 2x2. Do you have so many clients that transmit concurrently?

From the article (which is long):

> But as a very significant bonus, the 'extra' antennas if there is a mismatch in MIMO levels between the client and router do not go unused, but are used for 'diversity' and 'beamforming', which extends range, and improves speed at range.

You don't get higher max speed, but you do get better performance in general. I hadn't expected it to be drastic - I had thought it would be more theoretical than practical - so I had been planning on adding some 2x2 APs in a few months; but I don't think I need to now.

The original drive was because I have 4x4 on my desktop which won't get wired in for at least a year now; and my homelab is wired in.

Re: Wi is Fi: Understanding Wi-Fi 4/5/6/6E/7/8 (802.11 n/AC/ax/be/bn)

#78

Post by myself248 »

mbesto wrote: post #73

It seems the throughput has evolved over each spec but the reliability and distance hasn't, unless I'm mistaken? This is a big problem in place where concrete is used to build homes (e.g. the tropics) as the improvements to Wifi are basically not really relevant.

And 802.11ah, in 900MHz which has some hope of penetrating such walls, is still very scarce and the hardware fairly expensive.

Otherwise you just have to run a wire through the wall and put an AP in the room. Your clients can still be wireless for the last few feet, which preserves the convenience of usage, just not the convenience of deployment.

Re: Wi is Fi: Understanding Wi-Fi 4/5/6/6E/7/8 (802.11 n/AC/ax/be/bn)

#79

Post by rayiner »

mallets wrote: post #74
rayiner wrote: post #34

Earlier quoted context omitted.

> only 1 transmitter at a time per channel - across all WLANs, yours and your neighbours, with no deterministic way to avoid collisions. That’s not correct. You and your neighbor can use the same channel at the same time. On your network, the transmissions of the other network appear will appear as noise. As long as the other devices are far enough away, however, your devices will still be able to make out their own…

Only if the difference in signal power is high (>40 dB). It’s like saying collisions aren’t a problem in situations where no collision actually occurs.

If I’m in the room with one of my APs, my closest neighbor is a hair under 40 dB lower. But I can see a dozen other networks on my street, which means the other signals are strong enough where my phone can decode the packets.

The point is that wireless networks can use not only the channel dimension, but the spatial dimension. That’s the basis of things like MIMO.

Re: Wi is Fi: Understanding Wi-Fi 4/5/6/6E/7/8 (802.11 n/AC/ax/be/bn)

#80

Post by Normal_gaussian »

bjoli wrote: post #54
Normal_gaussian wrote: post #28

Today I set up a NWA210BE (Zyxel) to replace a unifi 6+ AP; I bought it second hand and my key metrics were: 4x4 MIMO, available used/discounted, current gen, fully functional standalone mode. The 4x4 makes all the difference. Sitting in my car the 6+ would fight with my 4G for internet and cause maps to be super slow; now I'm off the property before its unusable. I had intended to put APs in multiple rooms, but ther…

Inwas about to buy a pair of those, but then I saw the new mikrotik wifi 7 router (and probably upcoming access point) with thread radio. Now every other brand is dead to me.

That is really interesting! (https://mikrotik.com/product/hap_be3_media for others). Its coming in at a decent price as well.
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