Samsung has done quite well with their Galaxy S6 products worldwide. Samsung and Sony compete heavy so unfortunately they probably don't support each other's products well. Unfortunately this means that that standards like Wi-Fi Miracast, which is supposed to work with everyone, become collateral damage. For users, this means that the Samsung Galaxy S6 Edge's Miracast does not work with the Sony Bravia 4K Ultra HD Smart LED TV with Android.
The easiest way to use Wi-Fi Miracast to do screen mirroring on the Samsung Galaxy S6 Edge is to use Quick Connect.
The Galaxy S6 Edge attempts to connect to the Sony 4K TV but is never able to successfully complete the connection.
The Sony 4K TV also has a Screen Mirroring App but that didn't seem to work either.
Even trying to use the YouTube App on the Galaxy S6 Edge to Add the Sony 4K TV was not successful.
Both the Samsung Galaxy S6 Edge's Miracast and the Sony 4K Ultra HD Smart LED TV are Android based and using a standard technology for mirroring displays. However, despite both being premium products, they together fail to live up to expectations.