Improved apparatus and method for tracking short messages of talk group members

A subscriber device, comprising:

• a memory storing non-transitory computer-executable instructions;
• a transceiver;
• a processor configured to perform a set of functions in response to executing the instructions, the set of functions including:
• joining a talk group and receiving, via a control channel, parameters defining a plurality of assigned downlink data transmission periods associated with the talk group on a downlink short data channel;
• determining from the parameters when a next downlink short data transmission for devices in the talk group will be transmitted on the downlink short data channel;
• and
• responsive to the determining, switching, by the subscriber device, to the downlink short data channel during the next transmission period.

A radio controller comprising:

• a memory storing non-transitory computer-executable instructions;
• a transceiver;
• and
• a processor configured to perform a set of functions in response to executing the instructions, the set of functions including:
• receiving, via the transceiver, short data transmissions from radios;
• aggregating the short data transmissions by talk group;
• scheduling talk group short data transmissions on a talk group by talk group basis for transmission in a dynamically sized repeating block of time slots on a downlink short data channel, where each time slot is assigned to a particular talk group for short data transmission;
• configuring a control message including parameters identifying (i) when aggregated short data transmissions for each talk group will be made available in corresponding time slots on the short data channel in accordance with the scheduling and (ii) synchronization information for radios to synchronize to the short data channel;
• and
• transmitting, on a control channel, the control message to the radios.