Methods and systems for media access control allow master and slave nodes of a network to communicate using the same carrier while avoiding collisions of transmissions. At least one slave node is an implantable device. Master nodes initiate all data exchange sequences, and slave nodes are responsive to the data exchange sequences. The exchange sequences begin by master nodes contending for use of the carrier through a countdown procedure. A set order of communications occurs between a master node who won the contention and a slave node being communicated with by the master node to transfer a data frame. Contention is then repeated to determine the next master node that is allowed to transfer a data frame. New master nodes entering the network employ a discovery process to poll for existing devices in the network.