An apparatus and method control transmission of messages over a fixed bandwidth communication link from fixed position client or communication devices to a central controller. In one exemplary embodiment, the central controller determines an identifier associated with each communication device, a reporting period during which messages are to be transmitted by the communication devices, and transmission increments within the reporting period. The central controller allocates each transmission increment to a respective group of multiple communication devices. The central controller then determines transmission times for messages from the communication devices, such that a transmission time for any particular communication device is based on (a) the identifier for the particular communication device, (b) a duration of a transmission increment allocated to a group of communication devices that includes the particular communication device, and (c) a quantity of communication devices in the group of communication devices that includes the particular communication device.