How does tx power affect wifi speed?

[netok]

AFAIK, attenuation is independent of tx power. But will changing tx power affect the Throughput vs Atten graphs? If yes, is there any article that studies the effects? If not, how does tx power change affect the speed, if the speed is dictated by the fixed attenuation between the router and my device? Thanks in advance.

 

[thiggins]

Higher link rates generally require strong signals. Signal strength depends on both transmit power and receive sensitivity on both ends of the connection.

Maximum transmit power is limited by government regulation. Limits include antenna gain.

# of MIMO streams also affect effective throughput. That's why you see 4 stream routers rank higher in the Router tanker.

Rate adjustment algorithms also play a large factor. Sometimes dropping to a lower link rate lowers error rate and retries and improves throughput.

So there are many factors affecting effective link throughput, with transmit power only one of them.

The desired effect in the throughput vs. attenuation/RvR curves is to push the curve up, but more importantly, lengthen the flat part of the curve before it falls off.

 

[netok]

Thanks for your reply. I have an unrelated question. What do 2.4Ghz and 5Ghz Range mean in Ranker? I can't find how it is computed in testing methodology.

 

[degrub]

there are two radio frequency bands allowed for these devices. 2.4 GHz will pass through more obstacles and thus have longer reach. 5 GHz will be degraded after passing through 2 walls and sometimes only 1 wall and not be usable. 5GHz band is best when there is clear line of sight over short distance - like in a large room of a house or a meeting room.

The two selections are just reflecting the test results in each of those bands.

 

[CaptainSTX]

Thanks for your reply. I have an unrelated question. What do 2.4Ghz and 5Ghz Range mean in Ranker? I can't find how it is computed in testing methodology.

Read the entire six or seven pages of commentary along with the data tables compiled when testing a router and it will show you pictures of how it is done using a chamber and then attenuation levels are increased to simulate distance. Very scientific and the results are repeatable vs the old fashioned method of just signal levels at various locations in a home.

 

[netok]

there are two radio frequency bands allowed for these devices. 2.4 GHz will pass through more obstacles and thus have longer reach. 5 GHz will be degraded after passing through 2 walls and sometimes only 1 wall and not be usable. 5GHz band is best when there is clear line of sight over short distance - like in a large room of a house or a meeting room.

The two selections are just reflecting the test results in each of those bands.

I am fully aware of the characteristics of the 2 bands. My question is how the "Range" calculation is done. Thanks.

 

[ColinTaylor]

I am fully aware of the characteristics of the 2 bands. My question is how the "Range" calculation is done. Thanks.

It's based on a predetermined attenuation value per band. The precise values have changed over the years.

https://www.smallnetbuilder.com/wir...32478-how-we-test-wireless-products-revison-8
https://www.smallnetbuilder.com/wir...2993-how-we-test-wireless-products-revision-9
https://www.smallnetbuilder.com/wir...104-how-we-test-wireless-products-revision-10

 

[netok]

Read the entire six or seven pages of commentary along with the data tables compiled when testing a router and it will show you pictures of how it is done using a chamber and then attenuation levels are increased to simulate distance. Very scientific and the results are repeatable vs the old fashioned method of just signal levels at various locations in a home.

Yes I think I have read more than a few dozens reviews fully by now, together with the various versions of testing methodology that most people might not bother reading. I enjoy reading the reviews. They are of excellent quality. But, I still miss how "Range" calculation is done.

And I raised the original question because it is rarely discussed in his articles/reviews. Like he said, there are a lot of factors. I would love to see more discussion of them. I know there is already an article on the speed difference between 3x3 and 2x2 router connecting to a 2x2 STA.("# of MIMO streams also affect effective throughput...")

 

[netok]

It's based on a predetermined attenuation value per band. The precise values have changed over the years.

https://www.smallnetbuilder.com/wir...32478-how-we-test-wireless-products-revison-8
https://www.smallnetbuilder.com/wir...2993-how-we-test-wireless-products-revision-9
https://www.smallnetbuilder.com/wir...104-how-we-test-wireless-products-revision-10

Thanks! It is mentioned in one sentence in only revision 8. That's why I missed it.

 

[thiggins]

I am fully aware of the characteristics of the 2 bands. My question is how the "Range" calculation is done. Thanks.

It's a fair question because there is no range benchmark in the charts. It is a calculated value in the Ranker.

The method used in the ranker is to choose a point on the throughput vs. attenuation/RvR curve that is far enough out (high enough attenuation value) to represent a relatively low signal level, yet far enough in on the curve so that a non-zero value will be captured for all products. The higher the throughput, the better the ranking for range.

The range values for the Revision 10 process are 39 dB for 2.4 GHz and 30 dB for 5 GHz.