Wifi speed issue with SH2 Full Fibre and Disc

[stevek2]

I have Full Fibre 900 and was running into a problem where my devices would constantly switch from 5 ghz band to 2.4 ghz. 5 ghz would give me 200 - 250 mbps, but with 2.4 ghz my wifi speed would drop as low as 15 - 30 mbps. A wired connection direct to the hub gives the correct 900 + mbps speed. BT sent me a new SH2 but the results were the same.

I added a Wifi Disc and this seems to have stablised the 5 ghz connection, but my wifi speeds (200 - 250) remain unchanged. The disc is in the "excellent" location according to the app. I connected my laptop direct to the disc with a cable and got speeds of 550 mbps, but using wifi right next to the disc I am back to 250.

Should there be this much drop off in speed right next to the disc?

[Crimliar]

The drop off between connecting to WIFi on the disk, compared to connecting to the disk via a cable is exactly what you'd expect!

Why?

So lets say you want to move a 1Gbps when connected to the disk via WiFi.  Your computer transmits to the disk, and then the disk has to receive that 1Gbps and then re-transmit it.  Compared to when you connect to the disk with a cable, where that data only has to be transmitted once!

*Mesh systems do a great deal to cut down on unnecessary re-transmission, but when you have info that does need to traverse the network there's not much they can do to cut down on the quantity of that data!

[stevek2]

So generally 200 - 250 mbps is an acceptable speed over wifi for Full Fibre 900? I'm just trying to gauge what speeds I should be expecting as I've never had FTTP before.

It's weird because on my previous BT FTTC package I was getting a consistant 70 mbps over wifi on my laptop, which was near the maximum speed direct to the hub (about 80 mbps). Both the hub and laptop are still in the same positions, nothing else has changed.

[imjolly]

This is a previous post about expected speed

https://community.bt.com/t5/Home-setup-Wi-Fi-network/Re-full-fibre-100-issue/m-p/2298837#M202938

[stevek2]

I've seen this post before, but these are all theoretical max speeds. I'm just trying to get an idea of other users average wifi speeds on Fibre 900.

[c64z86]

When I was on the Fibre 500 speed boost, I was getting pretty close to that speed when an ethernet cable was connected to the disc, which was a hallway and a bit of a room upstairs diagonal from the SH2.

I was getting 450-500 on a good day and 300 on a bad day, but when I connected to that disc using wifi the maximum I could get was around 200, so yep those speeds seem pretty normal and good for wifi 5/AC wifi!

Now I'm on normal fibre 150, I'm getting that speed or close to that speed pretty much on all my devices! 

I think if you truly want gigabit wifi, then you might have to wait for wifi 7 to come out... that's supposed to over amazing speeds, but the only downside is that the 6ghz wifi range is shorter than even 5ghz though.

But I'm not sure if wifi 7 will have other technologies that will make up for this shortcoming, as it's still not finalised yet and any device that advertises itself as wifi 7 that is out now is using the draft version which may or may not have full compatibility for the full thing when it's released.

I left out wifi 6/6e as I'm just gonna skip straight to wifi 7 when it's cheap enough, so I didn't look into it too much... but others will know about it for sure!

[Crimliar]

Re WiFi speeds, if your speed connecting to a disk is 500Mbps via ethernet I would expect a fraction under half that when you connect to the same disk using WiFi!

As for theoretical speeds, I have an Asus GT-AX6000, an Asus RP-AX58(AX3000 mesh), and a couple of AX devices with 1200 PHY rates.  Over WiFi the fastest speeds using iPerf3 that I've seen are just over 900Mbps, and for speedtest.net around 730Mbps.  But with nothing else on the network, I can achieve about 90% of those speeds when using the Mesh node (RP-AX58) compared to connecting directly to the router.  *This depends on the router having acquired a 160MHz channel on 5GHz, which gives plenty of overhead, on an 80GHz channel there's not enough overhead and those speeds drop significantly when using the mesh node!

[ptrduffy]

As another data point, I had Full Fibre 900 installed yesterday, and on my 2021 Macbook Pro, sitting about 3m away from a disc, fast.com shows me getting about 210Mbps download (the Mac is connected using 802.11ac with a link speed of 866Mbps).

When I plug into an ethernet connection I get a solid 920Mbps.

There will be variability between devices, and dependent on home layout (e.g. in a different room, about the same distance from the same disc, but through a brick wall, my download tops out at 170Mbps), but I'd say 200 - 250Mbps on WiFi seems reasonable.

[Ewan1]

In short the SH2 is not powerful enough to handle 900mbps.

This is why you see stable speeds at 150mbps (which I had before upgrading to 900mbps (special offer)) as the router is operating well within its limits.

It needs to have a WIFI speed of at least 2000mbps to handle the fact that WIFI is transmit and receive whereas ethernet cable cat5e+ can do both simultaneously. 

As the SH2 does not handle WIFI 6 that also limits speeds.

The SH2 is dated now and needs to be replaced with an new model.

It would be interesting to know how the new Business SH3 compares.

[Les-Gibson]

Ethernet connections are full duplex i.e. they can transmit and receive simultaneously, Wi-Fi connections are half duplex meaning that they can only receive and transmit sequentially hence the reason why Wi-Fi is slower.

See What's the difference between half-duplex and full-duplex? | TechTarget