Dual band wifi extenders/repeaters but extending only a single (5ghz) band

[polypeptide4]

I understand that repeaters/extenders are frowned upon by purists.
My question is about a very specific usage setting.

Dual-band repeaters sometimes have a single frequency extender mode (they call it different things), where independent bands are used to communicate back to the base AP and to the client devices. So only one frequency gets "extended".
My question is about using the 2.4ghz band for backwards connection (and "extending" only 5ghz), an option which those devices allow.

Would the bandwidth of the final 5ghz signal be limited by 2.4ghz wireless-n limits, which is being used to communicate with the base AP? Is this setting recommended?
Would this still be faster than transmitting both ways on the same 5ghz band, at least for base internet subscriptions lower than the theoretical max for 2.4ghz? Would the 2.4ghz connection still be half-duplex?

Any clarification would be appreciated!

 

[Ralston18]

Seems like a homework question. Forum rules prohibit doing homework questions.

However, try the following:

Answer the question(s) you, yourself have asked. Tell the Forum what you believe are the answers.

Request some feedback accordingly.

 

[polypeptide4]

Seems like a homework question. Forum rules prohibit doing homework questions.

However, try the following:

Answer the question(s) you, yourself have asked. Tell the Forum what you believe are the answers.

Request some feedback accordingly.

Ok. Sorry if I phrased it too technically!
I think the new extended 5ghz network will alllow only half speed of the original network, because it uses the 2.4 network for one part of the connection.
I hope this is not true though, I would have thought this dedicated radio mode in dual band extenders was a good workaround to the half bandwidth problem.
But I could be wrong about how 2.4ghz works, maybe it ISN'T half duplex in this case...

So a simpler question is- does 2.4ghz always work in half duplex? Will this frequency always allow half the speed of the same network on 5ghz, or can they transmit the same?
Assuming the base internet speed is not over the limit for 2.4, say it's 100mbps...

 

[bill001g]

There are 2 forms of extenders/repeaters. The method you describe used to be the standard method. The things you find lately in the consumer stores actually retransmit the repeated data back into the same radio frequencies. So if the device is using the 2.4g radio it will also transmit a repeated 2.4g signal. If the radio has both a 2.4g radio and a 5g radio it will repeat the signal into both the 2.4g and 5g bands.

Because it retransmits into the 2.4g band you lose 1/2 your bandwidth at the very best. It is not only because it is half duplex.

WiFi is always half duplex. Even with just a single PC and router they both transmit and receive on the same exact radio frequencies. They always run the risk of transmitting over each other. The half duplex issue is a fundamental problem with wifi just made worse by the repeater. This is why the when you see a router claim 150mbps on wifi and you only get a tiny fraction of that.

Some of the newer mesh systems work different, they do not use the same radio to talk back to the main router. This is closer to the older definition of repeater but not all mesh systems work the same. This only partially solves the problem because the radio are not fully dedicated. The main router will still talk to end device with that radio.


The "repeater" function itself is not a huge issue. A huge number of cell phone tower work this way with only a master tower connected to fiber and all the other connected via point to point links. This is also used by many of the WISP providers. They use point to point to connect to their towers from other towers.

The key here is they are using a dedicated pair of radios to talk to each other. They have other radios to talk to the end users.

You could do this using the "tri" band routers using 1 of the 5g radios in each device to form the bridge leaving the other 5g radio and the 2.4g radio to end machines. You would have to carefully select the radio channels to not interfere.

The main issue with doing any of this is you are using more radio bandwidth. If you lived far away with nobody else around so you could have all the bandwidth to yourself things can work pretty well. When you live in a city where all your neighbors are putting in the tri band router along with multiple AP and multiple extenders everyone just stomps on each other. It is this competition for bandwidth that has pushed the need for extenders. The signal from the main router may actually reach the end device but there is so much crap coming in from outside it is no longer usable.

 

[polypeptide4]

Thanks Bob for your explanation, also about mesh systems and the urban interference problem. The wastage of radio space is sad.

You say wifi is always half duplex, but I thought ac wifi uses dedicated channels or something to communicate backwards and forwards? So it gets closer to providing the full bandwidth, and this was one of its advantages over n wifi?

Secondly, if you look at this example:
https://www.tp-link.com/us/faq-943.html
This is like the original repeaters you mention, but it is a possible setting on new consumer models. They advertise it as "high speed" mode here.

I am curious about using the 2.4 and 5ghz bands for bridging and rebroadcasting like this. A triband router bridges using 5ghz as you said, and I guess can transmit also on 5ghz. But if the 2.4 band is used for one function, then does it limit the practical bandwidth, because it defaults to wifi n protocol?
Interference aside, 2.4 has functional limits compared to 5 right? Or can this frequency handle the same data quantity and speed?

 

[bill001g]

802.11ac is also half duplex.

2.4g can only use 40mhz wide channels where you can use 80mhz on 5g. The wider channels is the key reason 802.11ac is faster. There is also some better encoding but that is minor compared to the increase in radio bandwidth.

Unfortunately there is no standard for any form of repeaters. All the manufacture are doing their own thing. Part of the reason for this is that it technically is impossible to run any form of repeater on "standard" 802.11n/ac. The encryption keys use the mac address so it is impossible to have mulitple devices behind a single encrypted session. The way they get around this is with a non standard feature called WDS. Most manufacture implement it in a similar way but there is no official standard so many vendors have features others do not.

 

[polypeptide4]

802.11ac is also half duplex.

2.4g can only use 40mhz wide channels where you can use 80mhz on 5g. The wider channels is the key reason 802.11ac is faster. There is also some better encoding but that is minor compared to the increase in radio bandwidth.

Thank you for this!