WLAN signal strength - good or bad ?

Werner Almesberger werner at openmoko.org
Sat Oct 4 23:56:39 CEST 2008

One of our customers reported poor WLAN reception:


Since I'm not even sure if this is actually a bug, I'm posting it
here for broader discussion.

I can confirm that my Neos see fewer access points than, say, my
laptop. But I'm not sure if this difference isn't just a natural
consequence of having a much smaller antenna.

I really don't know what results to expect. I'll ask our hardware
team for an estimate.

Meanwhile, here's a comparison of the access points my GTA02 see
(they each see four access points while the laptop reports about
20 of them). Test done Saturday mid-afternoon, downtown Buenos
Aires, humidity around 50%.

Signal levels (dBm) reported by iwconfig:

ESSID           Neo1    Neo2    Laptop

jose            -95     -87     -89
Marin           -95     -95     -88
xyz             -53     -45     -39
ALTAMIRANO      ---     -95     -92
BaseSR          -92     ---     -84
CBSHOME         ---     ---     -45

"xyz" is just 1m from the Neos or 50cm from the laptop. Also the
Neo that generally reports stronger signals varies by up to 8dB
when I move it on my desk.

CBSHOME is perhaps the most surprising result, because the laptop
claims it's strong enough to be very visible.

Of course, the laptop also reports one other at 0dBm (that would be
about right if I was using the Arecibo antenna, but I think that's
not quite what they meant with SETI at Home :-) and another one at
-98dBm, three dB below the noise floor.

The rest of the access points are all reported with very weak signal
strengths, so I'm not surprised the Neos don't see them.

In this test setup, the Neos are not in a great place to receive
anything from the outside. If I move them closer to the window, they
also see an access point in a restaurant about 100-120m away.

- Werner

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