WiFi throughput

ftp has very little overhead perhaps 3%

--
?? 100% natural

Generally you won't get even half of the theoretical max transfer rate specified by b,g or n

--
Dirk

http://www.neopax.com/technomage/ - My new book
http://www.transcendence.me.uk/ - Transcendence UK
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Hi Joe

My "slow" 802.11n uploads or downloads with average 8-10Mbyte/sec between two PCs.

Some time ago I accidently chose WPA, and then the 802.11n dropped to

4-5Mbyte/sec. After I found out that WPA2 is almost essentiel for higher 802.11n speed, I got high speed again.

Theoretically you can transfer 600Mbit/sec (ca. 60Mbyte/sec) if:

• both the access point and the PC wireless card supports 4 spatial streams,

• and you use 40MHz channel BW instead of the normal 20MHz

• and you are in a room with optimum multipaths for the 4 spatial streams

• and you alone the 40MHz channel - no interference from other APs:
  formatting link
  Quote: "... Data rates up to 600 Mbit/s are achieved only with the maximum of four spatial streams using a 40 MHz-wide channel ..."

I you have nearby APs you definatly need 5.4GHz support instead of only 2.4GHz.

The 2.4GHz has only 3 non-overlapping 20MHz channels (ch 1, 6, 11 ).

The 2.4GHz has 21 non-overlapping 20MHz channels (in most of EU).

On 13 Jan., 17:43, Glenn wrote: ...

Correction:

The 2.4GHz band has only 3 non-overlapping 20MHz channels (ch 1, 6,

11 ).

The 5.4GHz band has 21 non-overlapping 20MHz channels (in most of EU).

On 13 Jan., 17:43, Glenn wrote: ...

...

My test connection speed was ca. 130 or 144Mbit/s.

The 600Mbit/s is the raw capacity of the air interface; it doesn't account for gaps, preambles, headers, FEC and the protocol overhead. Even in the ideal situation, the useful point-to-point throughput of TCP over WiFi is somewhat 1/4...1/2 of the air bandwidth.

Vladimir Vassilevsky DSP and Mixed Signal Design Consultant

Also note that WiFi speed drops precipitously as you move further from the basestation. I've reads some of the reports on this, and one significant point is that the newer/faster standards fall off in speed much more rapidly (percentage-wise of peak speed vs. distance) than the older/slower standards.

SmallNetBuilder.Com is a good web site for this sort of information. See, e.g.,

. Note their point about how no WiFi standard today is as fast and robust as plain old 100Mbps Ethernet!

---Joel

Many thanks to all who contributed.... Fantastic - thank you.

The application is between a car PC and a desktop PC in a building.

I can arrange for directional antennas so the signals "point" at each other and line of site up to 40 metres.

Are there any other technologies that are faster and not more the $2k USD per WiFi (RF card)?

Regards Joseph

Look at

They have some higher power radios and directional antennas that might help.

I bought some 600mw pc cards from them, and I didn't have any problems.

Another thing you could do is to run a AP off a POE line and mount it closer to your car ;)

Cheers