If you want to use your own CDN to live stream with Uscreen, you can buy bandwidth from any CDN provider that provides an HLS playback URL.
A good option that we recommend is ScaleEngine. Once you've created an account they'll provide you with an HLS playback URL.
Send this to our support team and we'll replace our CDN provider with your CDN provider allowing you to buy bandwidth in bulk from a third party and not use Uscreen's live streaming bandwidth.