A method and system are provided for controlling which communication interface of a plurality of communication interfaces is used for communication between a plurality of devices that can be part of a wireless body area network for a medical device system. The communication interfaces can include a body area network communication interface and a far field communication interface. A controller can determine whether a first device is able to establish a communication link with a second device that is located in a coverage region of the wireless body area network using a first body area network communication interface. If so, the controller can determine whether a quality of service over the communication link is greater than or equal to a first threshold, and if so, the first body area network communication interface can be used to communicate data from the first device to the second device via magnetic signals.