Pas de wifi après installation de ubuntu

[panierpiano]

Salut,
Je n'ai pas de wifi après avoir installer ubuntu. Par contre, l'ADSL fonctionne.
Que faire ?
Merci.
Antoine.
PS : J'ai pu obtenir les infos suivantes après avoir tapé lscpi, ifconfig et iwconfig :


En tapant lspci :

bellotonio@maison:~$ lspci
00:00.0 Host bridge: ATI Technologies Inc RS480 Host Bridge (rev 10)
00:01.0 PCI bridge: ATI Technologies Inc RS480 PCI Bridge
00:06.0 PCI bridge: ATI Technologies Inc RS480 PCI Bridge
00:07.0 PCI bridge: ATI Technologies Inc RS480 PCI Bridge
00:12.0 IDE interface: ATI Technologies Inc IXP SB400 Serial ATA Controller (rev 80)
00:13.0 USB Controller: ATI Technologies Inc IXP SB400 USB Host Controller (rev 80)
00:13.1 USB Controller: ATI Technologies Inc IXP SB400 USB Host Controller (rev 80)
00:13.2 USB Controller: ATI Technologies Inc IXP SB400 USB2 Host Controller (rev 80)
00:14.0 SMBus: ATI Technologies Inc IXP SB400 SMBus Controller (rev 83)
00:14.1 IDE interface: ATI Technologies Inc IXP SB400 IDE Controller (rev 80)
00:14.2 Audio device: ATI Technologies Inc IXP SB4x0 High Definition Audio Controller (rev 01)
00:14.3 ISA bridge: ATI Technologies Inc IXP SB400 PCI-ISA Bridge (rev 80)
00:14.4 PCI bridge: ATI Technologies Inc IXP SB400 PCI-PCI Bridge (rev 80)
00:18.0 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] HyperTransport Technology Configuration
00:18.1 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] Address Map
00:18.2 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] DRAM Controller
00:18.3 Host bridge: Advanced Micro Devices [AMD] K8 [Athlon64/Opteron] Miscellaneous Control
01:05.0 VGA compatible controller: ATI Technologies Inc RS485 [Radeon Xpress 1100 IGP]
04:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168B PCI Express Gigabit Ethernet controller (rev 01)
05:04.0 FireWire (IEEE 1394): O2 Micro, Inc. Firewire (IEEE 1394) (rev 02)
05:04.2 SD Host controller: O2 Micro, Inc. Integrated MMC/SD Controller (rev 01)
05:04.3 Mass storage controller: O2 Micro, Inc. Integrated MS/xD Controller (rev 01)
05:09.0 Network controller: RaLink RT2561/RT61 rev B 802.11g
bellotonio@maison:~$




En tapant ifconfig :
eth0 Link encap:Ethernet HWaddr 00:19:db:3a:11:35
inet addr:192.168.0.6 Bcast:192.168.0.255 Mask:255.255.255.0
inet6 addr: fe80::219:dbff:fe3a:1135/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:8279 errors:0 dropped:0 overruns:0 frame:0
TX packets:5720 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:11403671 (10.8 MB) TX bytes:515809 (503.7 KB)
Interrupt:16 Base address:0xe000

lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
inet6 addr: ::1/128 Scope:Host
UP LOOPBACK RUNNING MTU:16436 Metric:1
RX packets:2014 errors:0 dropped:0 overruns:0 frame:0
TX packets:2014 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:100700 (98.3 KB) TX bytes:100700 (98.3 KB)

wlan0 Link encap:Ethernet HWaddr 00:19:db:09:5f:15
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:29 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:5541 (5.4 KB)

wmaster0 Link encap:UNSPEC HWaddr 00-19-DB-09-5F-15-00-00-00-00-00-00-00-00-00-00
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)

bellotonio@maison:~$




En tapant iwconfig :

bellotonio@maison:~$ iwconfig
lo no wireless extensions.

eth0 no wireless extensions.

wmaster0 no wireless extensions.

wlan0 IEEE 802.11g ESSID:""
Mode:Managed Frequency:2.462 GHz Access Point: Not-Associated
Tx-Power=27 dBm
Retry min limit:7 RTS thr:off Fragment thr=2346 B
Link Quality:0 Signal level:0 Noise level:0
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:0 Missed beacon:0

bellotonio@maison:~$