Weak wireless connection on Asus X55C using Xubuntu 13.04

Weak wireless connection on Asus X55C using Xubuntu 13.04

I had windows 8 initially installed on my Asus notebook before wiping and replacing with Xubuntu 13.04. The wireless signal on windows was fairly strong, but under Ubuntu rarely goes above 50% and the internet is running very slow.
Hopefully some of the below info is helpful is resolving the problem:
lshw -C network:

*-network              
       description: Wireless interface
       product: RT5390 Wireless 802.11n 1T/1R PCIe
       vendor: Ralink corp.
       physical id: 0
       bus info: pci@0000:02:00.0
       logical name: wlan0
       version: 00
       serial: 08:3e:8e:3f:63:7b
       width: 32 bits
       clock: 33MHz
       capabilities: pm msi pciexpress bus_master cap_list ethernet physical wireless
       configuration: broadcast=yes driver=rt2800pci driverversion=3.8.0-22-generic firmware=0.34 ip=192.168.0.6 latency=0 link=yes multicast=yes wireless=IEEE 802.11bgn
       resources: irq:17 memory:f7d00000-f7d0ffff
  *-network
       description: Ethernet interface
       product: AR8161 Gigabit Ethernet
       vendor: Qualcomm Atheros
       physical id: 0
       bus info: pci@0000:03:00.0
       logical name: eth0
       version: 10
       serial: 08:60:6e:99:e2:76
       capacity: 1Gbit/s
       width: 64 bits
       clock: 33MHz
       capabilities: pm pciexpress msi msix bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt-fd autonegotiation
       configuration: autonegotiation=on broadcast=yes driver=alx dri
verversion=1.2.3 firmware=N/A latency=0 link=no multicast=yes port=twisted pair
       resources: irq:19 memory:f7c00000-f7c3ffff ioport:e000(size=128)

iwconfig

wlan0     IEEE 802.11bgn  ESSID:"virginmedia6684984" 
          Mode:Managed  Frequency:2.437 GHz  Access Point: A0:21:B7:4E:DB:DD  
          Bit Rate=6.5 Mb/s   Tx-Power=20 dBm  
          Retry  long limit:7   RTS thr:off   Fragment thr:off
          Encryption key:off
          Power Management:on
          Link Quality=39/70  Signal level=-71 dBm 
          Rx invalid nwid:0  Rx invalid crypt:0  Rx invalid frag:0
          Tx excessive retries:5531  Invalid misc:165   Missed beacon:0

lo        no wireless extensions.

eth0      no wireless extensions.
Any ideas?
Thanks