I have the problem as well on my netbook (Asus eeePC 1000H) running Ubuntu 10.10.
My wireless card reports negative values for the signal level for "bad" APs and positiv values for the good AP. As the noise value is not reported (noise == 0) the quality of all signals is considered as maximal.
At the moment I think that the network manager, either consider quality instead of signal level to choose an AP or that it has problems with the mixing of negative and positive values.
As those values comes from the driver, I think the easiest way is to fix the network manager to handle this situation correctly.
Here is some example output from iwlist scan. The network manager tries to connect to the AP with MAC addr 00:03:52:29:62:43, which is actually the worst one considering the signal level.
I have the problem as well on my netbook (Asus eeePC 1000H) running Ubuntu 10.10.
My wireless card reports negative values for the signal level for "bad" APs and positiv values for the good AP. As the noise value is not reported (noise == 0) the quality of all signals is considered as maximal.
At the moment I think that the network manager, either consider quality instead of signal level to choose an AP or that it has problems with the mixing of negative and positive values.
As those values comes from the driver, I think the easiest way is to fix the network manager to handle this situation correctly.
Here is some example output from iwlist scan. The network manager tries to connect to the AP with MAC addr 00:03:52:29:62:43, which is actually the worst one considering the signal level.
Cell 01 - Address: 00:03:52:29:62:43
Channel: 9
Frequency :2.452 GHz (Channel 9)
Quality= 70/70 Signal level=-188 dBm
Encryptio n key:on
ESSID: "eduroam"
Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 6 Mb/s
9 Mb/s; 12 Mb/s; 18 Mb/s
Bit Rates:24 Mb/s; 36 Mb/s; 48 Mb/s; 54 Mb/s
Mode: Master
Extra: tsf=000000086a5 38af7
Extra: Last beacon: 16ms ago
IE: Unknown: 0007656475726F616D
IE: Unknown: 010882848B960C1 21824
IE: Unknown: 030109
IE: Unknown: 2A0100
Channel: 9
Frequency :2.452 GHz (Channel 9)
Quality= 70/70 Signal level=50 dBm
Encryptio n key:on
ESSID: "eduroam"
Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 6 Mb/s
9 Mb/s; 12 Mb/s; 18 Mb/s
Bit Rates:24 Mb/s; 36 Mb/s; 48 Mb/s; 54 Mb/s
Mode: Master
Extra: tsf=00000008848 ace68
Extra: Last beacon: 460ms ago
IE: Unknown: 0007656475726F616D
IE: Unknown: 010882848B960C1 21824
IE: Unknown: 030109
IE: Unknown: 2A0100
Channel: 9
Frequency :2.452 GHz (Channel 9)
Quality= 70/70 Signal level=-182 dBm
Encryptio n key:on
ESSID: "eduroam"
Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 6 Mb/s
9 Mb/s; 12 Mb/s; 18 Mb/s
Bit Rates:24 Mb/s; 36 Mb/s; 48 Mb/s; 54 Mb/s
Mode: Master
Extra: tsf=00000009023 1fecc
Extra: Last beacon: 1168ms ago
IE: Unknown: 0007656475726F616D
IE: Unknown: 010882848B960C1 21824
IE: Unknown: 030109
IE: Unknown: 050400010000
Channel: 9
Frequency :2.452 GHz (Channel 9)
Quality= 70/70 Signal level=-182 dBm
Encryptio n key:on
ESSID: "eduroam"
Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 6 Mb/s
9 Mb/s; 12 Mb/s; 18 Mb/s
Bit Rates:24 Mb/s; 36 Mb/s; 48 Mb/s; 54 Mb/s
Mode: Master
Extra: tsf=000000089c3 63177
Extra: Last beacon: 536ms ago
IE: Unknown: 0007656475726F616D
IE: Unknown: 010882848B960C1 21824
IE: Unknown: 030109
IE: Unknown: 050400010000
Channel: 9
Frequency :2.452 GHz (Channel 9)
Quality= 70/70 Signal level=-181 dBm
Encryptio n key:on
ESSID: "eduroam"
Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 6 Mb/s
9 Mb/s; 12 Mb/s; 18 Mb/s
Bit Rates:24 Mb/s; 36 Mb/s; 48 Mb/s; 54 Mb/s
Mode: Master
Extra: tsf=00000008783 cd417
Extra: Last beacon: 548ms ago
IE: Unknown: 0007656475726F616D
IE: Unknown: 010882848B960C1 21824
IE: Unknown: 030109
IE: Unknown: 050400010000
Channel: 13
Frequency :2.472 GHz (Channel 13)
Quality= 70/70 Signal level=-183 dBm
Encryptio n key:on
ESSID: "eduroam"
Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 6 Mb/s
9 Mb/s; 12 Mb/s; 18 Mb/s
Bit Rates:24 Mb/s; 36 Mb/s; 48 Mb/s; 54 Mb/s
Mode: Master
Extra: tsf=000000087d5 25e68
--
Cell 12 - Address: 00:03:52:1C:18:43
--
Cell 16 - Address: 00:03:52:1B:F5:03
--
Cell 18 - Address: 00:03:52:1C:32:93
--
Cell 21 - Address: 00:03:52:1C:24:43
--
Cell 25 - Address: 00:03:52:1C:08:C3