On Mon, Jun 8, 2009 at 4:42 PM, Larry Finger<[email protected]> wrote: > Bo Han wrote: >> Hi, >> >> When I do iwlist scan using my BCM 4318 cards, the reported noise >> level is very high, around -57 dBm. I don't expect the card to >> measure the background noise accurately. But this value looks >> unreasonable and it is higher than the signal strength of most of the >> data packets. I noticed that in the driver code, >> b43_rssi_postprocess(...) is called for signal strength, but not for >> noise level. Are they both using dBm? How to interpret the noise >> level? > > Yes, both are in dBm after the rssi_postprocess routine is called.
I am using 2.6.29-rc2. Only the reported signal level is in dBm after rssi_postprocess routine is called. b43 passes the noise level to mac80211 without any further processing and rssinoise_postprocess routine has not been used in the driver code. >> >> PS, I also tried another card in the same room, whose reported noise >> level is around -70 dBm. > > On my system: > > lspci > > 06:00.0 Network controller: Broadcom Corporation BCM4318 [AirForce One > 54g] 802.11g Wireless LAN Controller (rev 02) > > iwlist wlan0 scan > > Cell 01 - Address: 00:1A:70:46:BA:B1 > Channel:1 > Frequency:2.412 GHz (Channel 1) > Quality=49/70 Signal level=-61 dBm > Encryption key:on > ESSID:"lwfdjf_rad" > Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 18 Mb/s > 24 Mb/s; 36 Mb/s; 54 Mb/s > Bit Rates:6 Mb/s; 9 Mb/s; 12 Mb/s; 48 Mb/s > Mode:Master > Extra:tsf=000000515a64a93f > Extra: Last beacon: 516ms ago > IE: IEEE 802.11i/WPA2 Version 1 > Group Cipher : CCMP > Pairwise Ciphers (1) : CCMP > Authentication Suites (1) : PSK > Cell 02 - Address: 00:14:BF:0C:7E:14 > Channel:6 > Frequency:2.437 GHz (Channel 6) > Quality=30/70 Signal level=-80 dBm > Encryption key:on > ESSID:"linksys" > Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 18 Mb/s > 24 Mb/s; 36 Mb/s; 54 Mb/s > Bit Rates:6 Mb/s; 9 Mb/s; 12 Mb/s; 48 Mb/s > Mode:Master > Extra:tsf=000000d993312192 > Extra: Last beacon: 380ms ago > IE: WPA Version 1 > Group Cipher : TKIP > Pairwise Ciphers (1) : TKIP > Authentication Suites (1) : PSK > > Where is the noise level in the scan? It doesn't show up on my system. > When I do the iwconfig command, wlan0 reports a signal of -43 dBm and > a noise of -72 dBm when connected to the AP with ESSID "lwfdjf_rad". > Yes that noise level is higher than the signal from the AP with ESSID > of "linksys". You must remember that channel 1 is occupied by an AP > about 2 m from the computer, whereas the AP on channel 6 is a lot > further away and the noise is lower. I am using wireless tools with version number 29 and the Noise level is reported after Signal level. It seems to me that the noise level should not depend on where the AP is. It measures the background noise when no packet is transmitted. Thanks, -Bo > > 00:00.0 Host bridge: ALi Corporation M1541 (rev 04) > 00:01.0 PCI bridge: ALi Corporation M1541 PCI to AGP Controller (rev 04) > 00:03.0 CardBus bridge: O2 Micro, Inc. OZ6832/6833 CardBus Controller (rev 34) > 00:03.1 CardBus bridge: O2 Micro, Inc. OZ6832/6833 CardBus Controller (rev 34) > 00:04.0 Communication controller: Rockwell International HSF 56k > Data/Fax/Voice/Spkp (w/Handset) Modem (rev 01) > 00:07.0 ISA bridge: ALi Corporation M1533/M1535/M1543 PCI to ISA Bridge > [Aladdin IV/V/V+] (rev 0a) > 00:0e.0 Multimedia audio controller: ESS Technology ES1969 Solo-1 Audiodrive > (rev 02) > 00:0f.0 IDE interface: ALi Corporation M5229 IDE (rev 20) > 00:11.0 Bridge: ALi Corporation M7101 Power Management Controller [PMU] (rev > 09) > 00:13.0 USB Controller: ALi Corporation USB 1.1 Controller (rev 03) > 01:00.0 VGA compatible controller: Silicon Motion, Inc. SM710 LynxEM (rev a3) > 06:00.0 Network controller: Broadcom Corporation BCM4318 [AirForce One 54g] > 802.11g Wireless LAN Controller (rev 02) > eth1 Scan completed : > Cell 01 - Address: 00:1A:70:46:BA:B1 > Channel:1 > Frequency:2.412 GHz (Channel 1) > Quality=49/70 Signal level=-61 dBm > Encryption key:on > ESSID:"lwfdjf_rad" > Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 18 Mb/s > 24 Mb/s; 36 Mb/s; 54 Mb/s > Bit Rates:6 Mb/s; 9 Mb/s; 12 Mb/s; 48 Mb/s > Mode:Master > Extra:tsf=000000515a64a93f > Extra: Last beacon: 516ms ago > IE: Unknown: 000A6C7766646A665F726164 > IE: Unknown: 010882848B9624B0486C > IE: Unknown: 030101 > IE: Unknown: 2A0100 > IE: Unknown: 2F0100 > IE: IEEE 802.11i/WPA2 Version 1 > Group Cipher : CCMP > Pairwise Ciphers (1) : CCMP > Authentication Suites (1) : PSK > IE: Unknown: 32048C129860 > IE: Unknown: DD06001018020004 > Cell 02 - Address: 00:14:BF:0C:7E:14 > Channel:6 > Frequency:2.437 GHz (Channel 6) > Quality=30/70 Signal level=-80 dBm > Encryption key:on > ESSID:"linksys" > Bit Rates:1 Mb/s; 2 Mb/s; 5.5 Mb/s; 11 Mb/s; 18 Mb/s > 24 Mb/s; 36 Mb/s; 54 Mb/s > Bit Rates:6 Mb/s; 9 Mb/s; 12 Mb/s; 48 Mb/s > Mode:Master > Extra:tsf=000000d993312192 > Extra: Last beacon: 380ms ago > IE: Unknown: 00076C696E6B737973 > IE: Unknown: 010882848B962430486C > IE: Unknown: 030106 > IE: Unknown: 2A0104 > IE: Unknown: 2F0104 > IE: Unknown: 32040C121860 > IE: Unknown: DD06001018020004 > IE: WPA Version 1 > Group Cipher : TKIP > Pairwise Ciphers (1) : TKIP > Authentication Suites (1) : PSK > > > > _______________________________________________ Bcm43xx-dev mailing list [email protected] https://lists.berlios.de/mailman/listinfo/bcm43xx-dev
