On 05/06/2010 12:36 PM, seno wrote: > Hi Larry, > > I'm running Mandriva 2010 x86_64 (2.6.31.13) and have a 8187b chipset installed: > > 0bda:8189 Realtek Semiconductor Corp. RTL8187B Wireless 802.11g 54Mbps Network > Adapter > > As many other linux users report, this chipset is supported but offers only > limited performance, especially compared to results when using windows. > > Some time ago I connected to a Linksys wrt 54 GL router with Linksys firmware > and recently I installed DD-wrt on that router, but perfomance remaind at the > same (poor) level; meaning there must be something wrong with the rtl8187 linux > modul. > > Right now the router is ~10 meters away and iwconfig wlan0 output is > > IEEE 802.11bg ESSID:"xxx" > Mode:Managed Frequency:2.412 GHz Access Point: 00:14:BF:4A:ED:F9 > Bit Rate=18 Mb/s Tx-Power=27 dBm > Retry long limit:7 RTS thr:off Fragment thr:off > Encryption key:xxxx-xxxx-xxxx-xxxx-xxxx-xxxx-xxxx-xxxx [3] > Power Management:off > Link Quality=70/70 Signal level=-33 dBm > Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0 > Tx excessive retries:0 Invalid misc:0 Missed beacon:0 > > Right after booting, I can reach a wireless download rate of ~ 10mbit/s (I have > 10 mbit cable internet). After a while, it seems that the wireless rate drops > to 1 mbit/s although iwconfig wlan0 stills shows a bit rate of 11 or 18 mbit/s. > That means, I get stuck at a download speed of ~ 130 K/s -unless I come closer > to the router, 1 meter ie, then the wireless speed goes up again. > > The router status shows > > Wireless Packet Info > Received (RX) > 45915806 OK, 10 errors > Transmitted (TX) > 81142592 OK, 746 errors > > If the machine with the 8187b chip is connected, I get a lot of TX errors on > the router. > > While linux shows good connection quality, the router indicates a bad signal > quality: > > Signal Noise SNR Signal Quality > -74 -94 20 24% > > -I installed the latest package from linux wireless, driver loaded but for some > reason it was not able to connect to a wpa2 network (iwconfig wlan0 never shot > enc key), so I uninstalled that again. > -I booted a Mandirva 2010.0 x86 live cd to see if the problem is the same on 32 > bit system, and yes, it is. > -I found a 'newer' driver rtl8187B_linux_26.1056.1112.2009.release.tar.gz on > ubuntu forum - compiled, installed but for any reason driver did not load > correctly and something ooopsed (I blacklisted rtl8187 and set r8187 as alias > for wlan0). > > Any idea what I could do to get some better performance with the 8187b chipset? I do not understand the poor performance. I have a device with the rtl8187b chip - USB IDs 0bda:8187. That is an ID for an rtl8187, but it does have the B chip. I use tcpperf to measure the transmit speed. At 2 m from the AP with an indicated signal of -17 dBm, my throughput is 13 Mb/s. At 10 m with a signal of -49 dBm, the transmit speed is 3.5 Mb/s. On the download using speedtest.net, I got 11.3 Mb/s at 2 m, and 2.64 at 10 m. I got 0.49 Mb/s upload at both distances as that is the speed of my line. What happens if you use iwconfig to force a particular rate? At what setting is your throughput maximized. I don't think there is a problem with the rate setting mechanism, but that would test it. Larry -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
