Method for resolving call collisions in a digital conventional direct mode

Abstract

A process for resolving call collisions in a digital conventional direct mode includes monitoring a direct mode communication channel for transmissions from other direct mode radios in the plurality of direct mode radios. In response to detecting a new call request: identifying a last radio to transmit on the direct mode channel, transmitting a new call request for receipt by the last direct mode radio to transmit, monitoring the direct mode channel for a response from the last radio to transmit, and if a call grant granting the new call request is received from the last radio to transmit, initiating the new direct mode call on the direct mode communication channel. If the call grant is not received, at least temporarily refraining from initiating the new direct mode call.

1 . A method for resolving call collisions in a direct mode communication system among a plurality of direct mode radios, the method comprising, at a first direct mode radio out of the plurality of direct mode radios:
 transmitting, on a direct mode communication channel, one or more transmissions during a first direct mode call to the other direct mode radios in the plurality of direct mode radios, the transmissions including an identifier identifying the first direct mode radio;   after making the last transmission of the first direct mode call, transitioning to an arbitrating mode for the direct mode communication channel and monitoring the direct mode communication channel for any new direct mode call requests from other direct mode radios in the plurality of direct mode radios.   
     
     
         2 . The method of  claim 1 , further comprising:
 receiving, from a second direct mode radio out of the plurality of direct mode radios, a first new direct mode call request;   monitoring the direct mode communication channel for any additional new direct mode call requests from other direct mode radios in the plurality of direct mode radios; and   responsive to determining that one of (i) no other new direct mode call requests have been received and (ii) other new direct mode call requests have been received but the first new direct mode call request is entitled to priority over the other new call requests;
 broadcasting a call grant granting the first new direct mode call request of the second direct mode radio, the call grant including an identifier identifying the second direct mode radio; and 
 receiving and playing back content received from the second direct mode radio broadcast over the direct mode communication channel during the first new direct mode call generated by the acknowledgment. 
   
     
     
         3 . The method of  claim 2 , further comprising determining that no other direct mode call requests are received. 
     
     
         4 . The method of  claim 2 , further comprising receiving other new direct mode call requests, determining that other new direct mode call requests have been received, and determining that the first new direct mode call request is entitled to priority over the other new call requests; 
     
     
         5 . The method of  claim 2 , further comprising:
 responsive to receiving and playing back content received from the second direct mode radio, identifying the second direct mode radio as the last one of the other direct mode radios to transmit on the direct mode communication channel and storing an identity of the second direct mode radio for use in arbitrating future new call requests.   
     
     
         6 . The method of  claim 2 , wherein:
 the direct mode call request comprises a voice header or preamble control signaling block (CSBK) including a target device identifier field populated with a device identifier associated with the first direct mode radio.   
     
     
         7 . The method of  claim 1 , wherein:
 monitoring the direct mode communication channel for transmissions from other direct mode radios in the plurality of direct mode radios comprises monitoring the direct mode communication channel for transmissions including a particular system identifier with which the first direct mode radio is also associated with and includes in its transmissions.   
     
     
         8 . The method of  claim 1 , further comprising:
 responsive to one of a received instruction to power-off or otherwise disable its transceiver or an error condition indicative of an inability to receive transmissions over the direct mode communications channel, broadcasting an announcement indicating that the first direct mode radio will no longer be available to arbitrate new call requests on the direct mode channel.   
     
     
         9 . The method of  claim 1 , wherein the plurality of direct mode radios communicate in accordance with a European Telecommunications Standard Institute-Digital Mobile Radio (ETSI-DMR) direct mode protocol. 
     
     
         10 . The method of  claim 1 , wherein the direct mode communication system has no infrastructure equipment. 
     
     
         11 . The method of  claim 1 , wherein direct mode is a mode of operation where radios communicate directly with each other over a single shared RF frequency without the use of any infrastructure equipment. 
     
     
         12 . The method of  claim 1 , wherein infrastructure equipment comprises: base stations, repeaters, and any and all other external network infrastructure equipment.