Method and apparatus for quickly establishing a CDMA dispatch call
View Patent ↗To address the need for an apparatus and method for quickly establishing a CDMA dispatch call, the present invention provides for paging mobile stations (e.g., 120-123 ) to inform them of the call and then starting the dispatch call without waiting for page responses from the call participants. The dispatch call is first transmitted by base sites (e.g., 110-112 ) of all the service coverage areas (e.g., 101-103 ) that may have call participants, and then discontinued at those base sites where no page responses are received within a period of time. Thus, the dispatch call is established while “call setup” effectively continues.
1. A method for a base site to quickly establish a CDMA dispatch call comprising the steps of:
transmitting a broadcast page via an outbound CDMA paging channel that indicates an outbound CDMA traffic channel used for the dispatch call, without knowing a location for a mobile station (MS) targeted by the dispatch call;
beginning to transmit the dispatch call via the CDMA traffic channel without having received a page response to the broadcast page from the MS;
monitoring an inbound CDMA common access channel for page responses to the broadcast page;
when no page responses are received within a period of time,
ceasing to transmit the dispatch call via the CDMA traffic channel; and
deallocating the CDMA traffic channel.
2. The method of claim 1 further comprising the step of continuing to transmit the dispatch call via the traffic channel when at least one page response us received within the period of time.
3. The method of claim 1 wherein the period of time is equivalent to an amount of time for a base site to receive a page response to a broadcast page in a worst case scenario.
4. The method of claim 3 wherein the period of time is predetermined.
5. The method of claim 1 wherein the period of time is determined by the base site based on a history of time taken to respond to broadcast pages.
6. A base site comprising:
a transmitter;
a receiver; and
a controller, coupled to the transmitter and receiver, adapted to instruct the transmitter to transmit a broadcast page via an outbound CDMA paging channel that indicates an outbound CDMA traffic channel used for a dispatch call without knowing a location for a mobile station (MS) targeted by the dispatch call, adapted to instruct the transmitter to transmit the dispatch call via the CDMA traffic channel without having received a page response to the broadcast page from the MS, adapted to instruct the receiver to monitor an inbound CDMA common access channel for page responses to the broadcast page; and adapted to deallocate the CDMA traffic channel and to instruct the transmitter to cease transmitting the dispatch call via the CDMA traffic channel When no page responses are received within a period of time.
7. A method for a CDMA mobile station (MS) to quickly join a CDMA dispatch call comprising the steps of:
receiving a broadcast page on an outbound CDMA paging channel that indicates an outbound CDMA traffic channel used for the dispatch call;
beginning to receive the dispatch call via the CDMA traffic channel;
transmitting a page response to the broadcast page subsequent to beginning to receive the dispatch call, wherein the MS transmits the page response on an inbound CDMA common access channel.
8. The method of claim 7 further comprising the step of continuing to receive the dispatch call via the traffic channel subsequent to transmitting the page response.
9. The method of claim 7 wherein the MS transmits the page response in a manner that attempts to avoid concurrent page responses by other MSs.
10. The method of claim 9 wherein the inbound common access channel is a slotted response channel.
11. The method of claim 10 wherein the MS transmits the page response in a randomly determined slot.
12. The method of claim 10 the MS transmits the page response in a slot determined based on the MS's identification number.
13. A mobile station (MS) comprising:
a transmitter;
a receiver adapted to receive a broadcast page on an outbound CDMA paging channel that indicates an outbound CDMA traffic channel used for a dispatch call; and
a processor, coupled to the transmitter and receiver, adapted to instruct the receiver to begin to receive the dispatch call via the CDMA traffic channel and adapted to subsequently instruct the transmitter to transmit a page response to the broadcast page via an inbound CDMA common access channel.