Relation between Wireless Power Transfer, Wireless Information Transfer and the definition of sum rate I read this paper Charge-then-Forward: Wireless Powered Communication for Multiuser Relay Networks
 ,and it said it on the second page ,and I don't really understand why is the theory ,the author said, right.


  the time of WPT, Wireless Power Transfer, should be as small as possible so that the time for wireless information transmission (WIT) can be maximized for sum-rate maximization


Does anyone know the definition of sum-rate in formula type and the relation of WPT and WIT? I think I can really understand reason if I know these first.
"sum-rate" is just the sum of all rates of communications happening in a network.

The statement is pretty self-evident: The more time your nodes can communicate, the more data they can transfer.