Method and Apparatus for Informing a Radio of a Group-Call Started While the Radio Was Away from a Control Channel

1. A method comprising: affiliating, by a radio via a first channel, with at least one talk group the radio is interested in receiving calls from; sending, by the radio, a request to transmit location information on a separate revert channel; receiving, by the radio, a first grant time period to transmit location information on a particular revert channel in response to the request; moving, by the radio at substantially the first grant time period, away from the first channel to the particular revert channel to at least one of transmit location information and transmit a request for a second grant time period on the particular revert channel; receiving, by the radio, an announcement on the particular revert channel after the first grant time period that a call of interest associated with the at least one talk group started while the radio was on the particular revert channel; determining, by the radio, an assigned traffic channel for the call of interest; and switching, by the radio, from the particular revert channel to the assigned traffic channel in order to receive the call of interest.

2. The method of claim 1 , wherein the receiving the first grant time period comprises receiving at least one of a first grant window number, a frame number for the first grant time period, a current frame number, and a current window number in a registration acknowledgment broadcast from a control channel manager.

3. The method of claim 1 , wherein the affiliating comprises registering a plurality of talk groups and including priority information for the priority of talk groups.

4. The method of claim 3 , wherein the determining the assigned traffic channel for the call of interest includes determining the assigned traffic channel for the call of interest associated with a talk group with a highest priority.

5. The method of claim 1 , further comprising sending, by a controller, a radio identifier identifying the radio and an identity of the at least one talk group to a location repeater associated with the particular revert channel.

6. The method of claim 1 , further comprising: moving, by the radio at substantially the second grant time period, away from the first channel to the particular revert channel to transmit location information; receiving, by the radio, an announcement on the particular revert channel during the second grant time period indicating whether a call of interest associated with the at least one talk group started while the radio was on the particular revert channel; determining, by the radio, that the call of interest was not started; and switching to a current control channel.

7. The method of claim 6 , further comprising storing synchronization information for the current control channel and using stored timing information in switching to the current control channel subsequent to determining that the call of interest was not started.

8. The method of claim 1 , further comprising obtaining the second grant time period.

9. The method of claim 1 , wherein the moving to the particular revert channel comprises sending, by the radio, the location information on the particular revert channel during a first period in the first grant time period, and sending, by another radio, the request for the second grant time period during a second period in the first grant time period.

10. The method of claim 9 , further comprising one of: determining, by each of the radios, based on the receiving the announcement that calls of interest were started for each of the radios and obtaining, by each of the radios, the traffic channel for the associated call of interest; and determining, by each of the radios, based on the receiving the announcement that a call of interest was started for one of the radios and obtaining, by the radio determined to have a call of interest, the traffic channel for the call and returning, by the radio determined not to have a call of interest, to a current control channel.

11. A radio comprising; a memory configured to store a list of talk groups the radio is interested in receiving calls from; a transceiver; and a processor configured to: affiliate, via the transceiver and a first channel, with at least one talk group the radio is interested in receiving calls from; send, via the transceiver, a request to transmit location information on a separate revert channel; receive, via the transceiver, a first grant time period to transmit location information on a particular revert channel in response to the request; tune, via the transceiver, at substantially the first grant time period, away from the first channel to the particular revert channel to at least one of transmit location information and transmit a request for a second grant time period on the particular revert channel; receive, via the transceiver, an announcement on the particular revert channel after the first grant time period that a call of interest associated with the at least one talk group started while the radio was on the particular revert channel; determine an assigned traffic channel for the call of interest; and switch from the particular revert channel to the assigned traffic channel in order to receive the call of interest.

12. The radio of claim 11 , wherein the processor is configured to receive, via the transceiver, at least one of the first grant window number, a frame number for first grant time period, a current frame number, and a current window number in a registration acknowledgment broadcast from a control channel manager.

13. The radio of claim 11 , wherein the processor is configured to register a plurality of talk groups and include priority information for the priority of talk groups.

14. The radio of claim 13 , wherein the processor is configured to determine the assigned traffic channel for the call of interest associated with a talk group with a highest priority.

15. The radio of claim 11 , wherein the processor is configured to: move at substantially the second grant time period away from the first channel to the particular revert channel to transmit location information; receive an announcement on the particular revert channel during the second grant time period indicating whether a call of interest associated with the at least one talk group started while the radio was on the particular revert channel; determine that the call of interest was not started; and switch to a current control channel.

16. The radio of claim 15 , wherein the processor is configured to store, in the memory, synchronization information for the current control channel and use stored timing information in switching to the current control channel subsequent to determining that the call of interest was not started.

17. The radio of claim 11 , wherein the processor is configured to obtain the second grant time period.

18. The radio of claim 11 , wherein the processor is configured to send the location information on the particular revert channel during a first period in the first grant time period, and wherein the processor of another radio is configured to send the request for the second grant time period during a second period in the first grant time period.

19. The radio of claim 18 , wherein the processors of each of the radios are configured to: determine, based on the receiving the announcement, that calls of interest were started for each of the radios and obtain the traffic channel for the associated call of interest; and determine, based on the receiving the announcement that a call of interest was started for one of the radios and obtain, by the processor of the radio determined to have a call of interest, the traffic channel for the call and return, by the processor of the radio determined not to have a call of interest, to a current control channel.