Purchasing your own router is an option. You would have to put the Comcast gateway into bridge mode. Instructions on how to do this can be found here
That may not solve your issue if there is a signal issue.
Read this for suggestions on things to try Connection Troubleshooting Tips (topic at the Comcast Help Forums)
What I suggest is that you post your problem in the Comcast Help Forum.
Click the link below. The forum landing page will open. Click Sign In. Log in with your Comcast user ID (the part before .net) and your password. You will next see a first time forum users page, asking you to choose a screen name for use in the Forums. Once you set that up, you'll be taken back to the landing page. PLEASE DO NOT USE YOUR COMCAST EMAIL NAME FOR YOUR FORUM USER NAME.
Then choose the appropriate board to post in. In your case you would post in Internet/Home Networking / Router / And WiFi Gateway Help
It would be helpful if you post your signal levels as requested Information Requested for Connection-Related Posts
The Comcast forum has connection experts who can help you determine what the issue might be.
One thing to be aware of: By default you will be notified via email every time someone replies to a topic you have started or replied in. If you do not wish to receive the notifications you can disable them by clicking My Settings/Subscriptions & Bookmarks tab. Uncheck the box next to Automatically subscribe me to topics I participate in. Scroll down and click Save.
DO NOT USE THE UNSUBSCRIBE LINK IN THE REPLY NOTIFICATION EMAIL. Due to a quirk with Lithium, the forum provider, if you use the link it severs the connection between your forum user name and the email address you sign in with.
Result: your forum account no longer exists in the database and it tells you that you are banned.
(Once you get to the forum, save the page to your favorites/bookmarks. If you want to get to it from the Comcast home page, you have to jump through hoops to reach it)
If you have any questions about the Comcast forum, you can ask me here at Bleeping Computer or there, where my user name is the same as the one here.
Edited by Queen-Evie, 07 February 2016 - 09:38 PM.