R e: Wi-fi dropping and range radically reduced - Hub4

[licquorice]

Although there is a school of thought that because of CSMA/CA it is better to use the same channel rather than a partially overlapping one if complete non-overlapping is not possible. I'm not sure that I subscribe to that view, particularly if one signal is being saturated due to streaming.

[Keith_Beddoe]

The problem is that you cannot see the other multiple sources that use the 2.4GHz allocation, without a spectrum analyser. You can  buy a USB wireless receiver, and suitable software, but its not cheap.

Even on my Asus Netbook, with a wireless card that has a promiscuous mode, I can see wireless routers with hidden SSIDs, that are occupying channels. These do not show up on a normal wireless  adapter. The spectrum is more crowded than people realise.

[licquorice]

Indeed, I think the only real method of selecting a good channel is trial and error!

[Keith_Beddoe]

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@licquorice wrote:

Indeed, I think the only real method of selecting a good channel is trial and error!

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Exactly, and be prepared to move a single channel up or down, to see if it improves performance.

Use Ethernet or powerline adapters as a first choice, for devices that stay in house, keeping wireless just for those roaming devices where performance is not a major issue.

Things like smart TVs, should only be connected via wireless, as an absolute last resort, as they consume vast amount of bandwidth, leaving every other wireless device stuggling.

[Gary_C]

@licquorice wrote:

Although there is a school of thought that because of CSMA/CA it is better to use the same channel rather than a partially overlapping one if complete non-overlapping is not possible. I'm not sure that I subscribe to that view, particularly if one signal is being saturated due to streaming.

Ive wondered about this.

Its been many a year since i did sideband radio at uni, but that only covered AM/FM tranmission and was before WiFi at home existed 🙂

[Gary_C]

yes, of course you are right about overlap, but essentially 1,6 & 11 is a easy way of thinking of it but your diagram is simpler

until someone uses 40mhz and spreads even more 🙂

[Keith_Beddoe]

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@Gary_C wrote:


until someone uses 40mhz and spreads even more 🙂

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Like the Virgin Media Superhubs

[Gary_C]

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@licquoricewrote:

Although there is a school of thought that because of CSMA/CA it is better to use the same channel rather than a partially overlapping one if complete non-overlapping is not possible. I'm not sure that I subscribe to that view, particularly if one signal is being saturated due to streaming.

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Looking into it, WiFi uses QAM so the spread is due to the FM part of the modulation spreading around the centre carrier frequency ? So will CSMA look for transmissions only at the carrier frequency before transmitting or the whole used spectrum ?

[Keith_Beddoe]

I would expect it to look at the centre frequency, as modern radio front ends take samples at a specific rate which relates to the centre frequency of the carrier, unlike the old radio receivers that were superhet https://en.wikipedia.org/wiki/Superheterodyne_receiver designs, and had a defined bandwidth.

But its all done by clever mathematics, which I could not start to understand. I was brought up on old radio stuff, using inductors and tuning capacitors

Anyway, getting a bit off topic now.

[Gary_C]

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@Keith_Beddoewrote:

I would expect it to look at the centre frequency, as modern radio front ends take samples at a specific rate which relates to the centre frequency of the carrier, unlike the old radio receivers that were superhet https://en.wikipedia.org/wiki/Superheterodyne_receiver designs, and had a defined bandwidth.

But its all done by clever mathematics, which I could not start to understand. I was brought up on old radio stuff, using inductors and tuning capacitors

Anyway, getting a bit off topic now.

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Known what you mean. As an instrumentation mechanic originally, all the stuff I worked on used valves not transistors as amps.

so if the carrier sense of CSMA detects the carrier, it might not be able to tell that channel 6 is active when beginning to transmit on channel 7. This seems to be the point some are making in only choosing channels 1,6 &11.