My Wireless device is not working properly .

Hy everyone .

I'm new to Ubuntu , I've installed it just a few days ago and I can't get my wireless to work . On windows I have more than 4 available networks but on Ubuntu sometimes it finds my network and sometimetimes it doesn't . But even when it finds it I can't connect to it .

I have a MSI CR620 Laptop .

Here is the result of some commands that I've read about on some other posts :

                           lspci

00:00.0 Host bridge: Intel Corporation Core Processor DRAM Controller (rev 02)
00:02.0 VGA compatible controller: Intel Corporation Core Processor Integrated Graphics Controller (rev 02)
00:16.0 Communication controller: Intel Corporation 5 Series/3400 Series Chipset HECI Controller (rev 06)
00:1a.0 USB Controller: Intel Corporation 5 Series/3400 Series Chipset USB2 Enhanced Host Controller (rev 05)
00:1b.0 Audio device: Intel Corporation 5 Series/3400 Series Chipset High Definition Audio (rev 05)
00:1c.0 PCI bridge: Intel Corporation 5 Series/3400 Series Chipset PCI Express Root Port 1 (rev 05)
00:1c.1 PCI bridge: Intel Corporation 5 Series/3400 Series Chipset PCI Express Root Port 2 (rev 05)
00:1c.3 PCI bridge: Intel Corporation 5 Series/3400 Series Chipset PCI Express Root Port 4 (rev 05)
00:1c.5 PCI bridge: Intel Corporation 5 Series/3400 Series Chipset PCI Express Root Port 6 (rev 05)
00:1d.0 USB Controller: Intel Corporation 5 Series/3400 Series Chipset USB2 Enhanced Host Controller (rev 05)
00:1e.0 PCI bridge: Intel Corporation 82801 Mobile PCI Bridge (rev a5)
00:1f.0 ISA bridge: Intel Corporation Mobile 5 Series Chipset LPC Interface Controller (rev 05)
00:1f.2 SATA controller: Intel Corporation 5 Series/3400 Series Chipset 4 port SATA AHCI Controller (rev 05)
00:1f.3 SMBus: Intel Corporation 5 Series/3400 Series Chipset SMBus Controller (rev 05)
00:1f.6 Signal processing controller: Intel Corporation 5 Series/3400 Series Chipset Thermal Subsystem (rev 05)
05:00.0 Network controller: RaLink RT3090 Wireless 802.11n 1T/1R PCIe
06:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8101E/RTL8102E PCI Express Fast Ethernet controller (rev 02)
3f:00.0 Host bridge: Intel Corporation Core Processor QuickPath Architecture Generic Non-core Registers (rev 02)
3f:00.1 Host bridge: Intel Corporation Core Processor QuickPath Architecture System Address Decoder (rev 02)
3f:02.0 Host bridge: Intel Corporation Core Processor QPI Link 0 (rev 02)
3f:02.1 Host bridge: Intel Corporation Core Processor QPI Physical 0 (rev 02)
3f:02.2 Host bridge: Intel Corporation Core Processor Reserved (rev 02)
3f:02.3 Host bridge: Intel Corporation Core Processor Reserved (rev 02)

              sudo lshw -C network

  *-network
       description: Wireless interface
       product: RT3090 Wireless 802.11n 1T/1R PCIe
       vendor: RaLink
       physical id: 0
       bus info: pci@0000:05:00.0
       logical name: wlan0
       version: 00
       serial: 6c:62:6d:1f:be:eb
       width: 32 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless
       configuration: broadcast=yes driver=rt3090 latency=0 multicast=yes wireless=RT2860 Wireless
       resources: irq:19 memory:f4000000-f400ffff
  *-network
       description: Ethernet interface
       product: RTL8101E/RTL8102E PCI Express Fast Ethernet controller
       vendor: Realtek Semiconductor Co., Ltd.
       physical id: 0
       bus info: pci@0000:06:00.0
       logical name: eth0
       version: 02
       serial: 6c:62:6d:2e:bf:24
       size: 10MB/s
       capacity: 100MB/s
       width: 64 bits
       clock: 33MHz
       capabilities: pm msi pciexpress msix vpd bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd autonegotiation
       configuration: autonegotiation=on broadcast=yes driver=r8169 driverversion=2.3LK-NAPI duplex=half latency=0 link=no multicast=yes port=MII speed=10MB/s
       resources: irq:29 ioport:a000(size=256) memory:f2c10000-f2c10fff(prefetchable) memory:f2c00000-f2c0ffff(prefetchable)

iwconfig

lo no wireless extensions.

eth0 no wireless extensions.

wlan0 RT2860 Wireless ESSID:"" Nickname:"RT2860STA"
          Mode:Auto Frequency=2.412 GHz Access Point: Not-Associated
          Bit Rate:1 Mb/s
          RTS thr:off Fragment thr:off
          Link Quality=10/100 Signal level:0 dBm Noise level:-115 dBm
          Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
          Tx excessive retries:0 Invalid misc:0 Missed beacon:0

I hope that someone can help me . Thanks in advance .