Unfortunately, you didn't provide any details of the exact issue you are having but here are somethings you can try.
You can always check online services status here http://www.callofduty.com/ghosts/status
If online services are fully operational and you are still unable to connect, you may want to try the following.
- Reboot your router.
- Try using a wired connection in order to sustain the connection quality.
- Establish a static IP address and port forward.
Here are the port numbers you will need:
Should you have any questions on how to port forward, please contact your ISP or the router manufacturer.
Have you reported this issue to Activision Support? they will get their teams to look into it, however is this issue permanent? if it is then that is a issue but if it is not then it can just be your connection sometimes.