I have a couple of articles here that can help you troubleshoot this issue further. First, you may want to look over this article for troubleshooting Wi-Fi in OS X:
You may also want to check out the Wi-Fi Quick Assist, which will walk you through some basic troubleshooting steps for Wi-Fi issues. That quick assist article can be found here:
And just in case you need it, this article is about the recommended router settings for using iOS and OS X:
Thanks for using the Apple Support Communities!