a communication system is provided for communication between network nodes and a communication controller . in the network , a reservation request is transmitted from a node to the communication controller in an assigned timeslot . in response the controller provides a grant of permission to the requesting node to transmit packet data containing a message . the timeslot assigned to the requesting node is one of a series of timeslots occurring repeatedly on a separate frequency . the timeslots will be continuously available to receive requests from nodes irrespective of transmission of data from one node to the controller , or transmission of a grant from the controller to a node .