I have implemented SignalR BackPlane and it seems to be working fine.
Have used this URL for reference.
I am creating a new SQL Database to achieve SingalR. My Doubt is: why do I have to create a new DB, or why can't I make use of existing Database?
You can use the same DB , however for performance it is better to have DB with Service Broker enabled. (That is why I have a seperate DB for my singlR use cases)
Permissions:
"Requires CREATE TABLE permission in the database and ALTER permission on the schema in which the table is being created."
Taken from here http://msdn.microsoft.com/en-us/library/ms188264.aspx