you might try this first...
aireplay-ng -9 ra0
everything else says optional, and make sure your card is in monitor mode.
from aircrack's website
aireplay-ng -9 -e teddy -a 00:14:6C:7E:40:80 -i wlan0 ath0
-9 means injection test. Long form is - -test. (Double dash)
-e teddy is the network name (SSID). This is optional.
-a 00:14:6C:7E:40:80 ath0 is MAC address of the access point (BSSID). This is optional.
-i wlan0 is interface name of the second card if you want to determine which attacks your card supports. This is optional.
ath0 is the interface name or airserv-ng IP Address plus port number. For example - 127.0.0.1:666. (Mandatory)
IMPORTANT: You must set your card to the desired channel with airmon-ng prior to running any of the tests.