Patent Publication Number: US-2006014555-A1

Title: Method and apparatus for determining whether a talkgroup is occupied

Description:
FIELD OF THE INVENTION  
      The present invention relates generally to radio communication systems and in particular, to the field of trunked communication systems with talkgroups.  
     BACKGROUND OF THE INVENTION  
      Trunked communication systems generally have many talkgroups. A user of the trunked communication system may have many talkgroups to choose from, but does not have knowledge of whether there are other users or the number of other users on the same talkgroup. Users prefer to use a talkgroup that is being used (also known as “occupied”) by others for a number of reasons. One reason is that using an occupied talkgroup may provide information about others and events occurring in the area. A second reason is that using an occupied talkgroup may provide a level of comfort to users in sparsely populated, such as rural, areas or at off-peak times, such as at night. In such situations, a talkgroup with only one user may present a safety issue. A third reason is that users with colleagues in the same talkgroup may share information necessary to provide assistance. For example, in a police system, police officers on the same talkgroup can keep track of colleagues and provide quick assistance if necessary. Because of all these reasons, it is necessary to provide an indication of whether a talkgroup is occupied.  
      Currently, users listen for other communications on a talkgroup to determine whether the talkgroup is occupied. This is not a reliable way to find out if the talkgroup is occupied because other users in the talkgroup may be listening and not transmitting any communications. Users may periodically transmit “anyone out there” to try to find out if a talkgroup is occupied, but this is time consuming and efficient if a user needs to quickly determine whether the talkgroup is occupied or not.  
      While there are ways to determine whether a talkgroup is occupied or not, the current methods are not reliable, are inefficient, and are relatively unsatisfactory. Accordingly, there exists a need for a better method and apparatus for determining whether a talkgroup is occupied. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      A preferred embodiment of the invention is now described, by way of example only, with reference to the accompanying figures in which:  
       FIG. 1  is a block diagram illustrating a typical trunked communication system in accordance with the invention.  
       FIG. 2  is a flow diagram illustrating the method for determining whether a talkgroup is occupied in accordance with the invention. 
    
    
      It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements are exaggerated relative to each other. Further, where considered appropriate, reference numerals have been repeated among the figures to indicate identical elements.  
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       FIG. 1  is a block diagram of an exemplary trunked communication system  100 . The subscriber units  108 ,  110 ,  112  which are a part of the trunked communication system  100  communicate over control channel  102  with a central resource such as a system controller  104  in order to receive status and control information from the system controller  104 . The subscriber units  108 ,  110 ,  112  are typically mobile or portable devices and are also known in the art as “radios.” Further, subscriber units are characterized by a talkgroup identifier where a talkgroup is a group of subscriber units that share a radio frequency channel in the trunked communication system  100 . Subscriber units with the same talkgroup identifier are able to communicate with each other and are able to monitor conversations between users in the same talkgroup whereas subscriber units with different talkgroup identifiers are not able to communicate with each other. For example in  FIG. 1 , subscribers  108 ,  112  are in the same talkgroup, namely talkgroup A, and are able to communicate with each other and monitor conversations in talkgroup A whereas subscriber  110  is in talkgroup B and is not able to communicate with subscribers  108 ,  112  or monitor conversations in talkgroup A.  
      The system controller  104  acts as the system coordinator and is responsible for assigning subscriber units  108 ,  110 ,  112  to different repeaters  106 ,  118  (also known as channels) so that they may communicate amongst each other. Each repeater  106 ,  118  has an associated control channel  102  where the associated control channel may be on a unique frequency or similar frequency. The system controller  104  is also responsible for knowing where each of the subscriber units are located (i.e. what voice channel and/or what site) and for controlling other features typically found in a modern trunked communication system (e.g. handling phone patches, coordinating groups of radios in emergency situations, etc.). Further, the system controller  104  has a database  116  for keeping track of the subscribers. Typically, the database  116  keeps track of subscriber units and information relating to the subscriber units, such as IDs, talkgroup identifiers, and site location. For example in  FIG. 1 , the database  116  may contain information of subscriber unit  108  such as the subscriber unit&#39;s ID, that subscriber unit  108  is in talkgroup A and that subscriber unit  108  is associated with repeater  106 . Further, the information in the database  116  may be updated as the subscriber units  108 ,  110 ,  112  change talkgroups and move in the trunked communications system  100 . Further yet, the typical system controller  104  includes a main processing unit such as a computer with appropriate control software that controls the operation of controller  104 . Also normally included with controller  104  is a dispatch center  114 . The dispatch console  114  allows dispatchers to communicate with the system subscriber units. The dispatch console  114  may also include a dispatch console or workstation to provide information about the trunked communications system  100 .  
      Communications between the subscriber units  108 ,  110 ,  112  and the system controller  104  can be of two directions, inbound and outbound. The signals that are sent from the system controller  104  to the subscriber units  108 ,  110 ,  112  over the control channel  102  are typically called outbound signaling communications. The control signals going from subscriber units  108 ,  110 ,  112  to the system controller  104  are called inbound signaling communications. Outbound signaling communications inform the subscriber units  108 ,  110 ,  112  when to change channels automatically so as to communicate with other members in the same talkgroup over an assigned voice channel  106  which has been assigned by the system controller  104 .  
      An example of a typical trunked communication begins when a subscriber unit (e.g.  108 ) enters a repeater (e.g.  106 ) coverage area. The subscriber unit may initiate a communication by pressing PTT (push to talk) which sends a request for a voice channel  106  to the system controller  104 . In an exemplary embodiment, the request includes information about which talkgroup the subscriber unit has selected, e.g. for subscriber unit  108 , talkgroup A has been selected. Once the request is received at the system controller  104 , the system controller  104  registers the subscriber unit with the repeater site by assigning a voice channel (e.g. voice channel on repeater  106 ) to the subscriber unit  108  and by updating the database of subscribers with information about the subscriber unit  108 . The system controller  104  sends an acknowledgement and an over-the-air message to the subscriber unit  108  with information as to whether the selected talkgroup is occupied or not. In response to the received messages, the subscriber unit provides an indicator to the user of whether the selected talkgroup is occupied or not. In an exemplary embodiment, the dispatch console also provides an indication in the dispatch centre as to the relationship between subscriber units in the trunked communication system  100  and their associated talkgroups.  
      Further, as the subscriber unit moves in the trunked communication system  100 , the system controller  104  updates the database  116  with information about the subscriber unit and the talkgroup that the subscriber unit has selected. For example, if subscriber unit  108  moves from coverage in the trunked communication system  100  where coverage is provided by repeater  106  to where coverage is provided by repeater  118 , the database  116  is updated with this new information. Also, if the subscriber unit  108  changes talkgroups, for example from talkgroup A to talkgroup B, then the database  116  is also updated with this new information.  
      An exemplary embodiment of the present invention provides an indicator on the subscriber unit, such as  108 ,  110 ,  112 , to provide a sign that the selected talkgroup is occupied or not. The indicator may be visual or audible. Further, the indicator may be programmed where an “on,” such as a light, indicates that the talkgroup is not occupied or programmed where an “on,” such as a light, indicates that the talkgroup is occupied. For example in  FIG. 1 , there is an LED visual indicator  120  that shows a user of subscriber unit  108  that the selected talkgroup, namely talkgroup A, is occupied, since subscriber unit  112  is also in talkgroup A. Another example in  FIG. 1 , there is an LED visual indicator  122  that shows a user of subscriber unit  110  that he selected talkgroup, namely talkgroup B, is not occupied. Such information may encourage the user of subscriber unit  112  to select another talkgroup or contact a dispatcher at the dispatch centre  114  for further assistance.  
      There are a number of variations of the indicator that are within the scope of the present invention. One variation is an indicator that displays the number of users in the talkgroup. Another variation is an indicator that displays the type of users in the talkgroup. An example is a display that indicates whether the users are subscriber units or dispatchers. Yet another variation, is an indicator that suggests an occupied talkgroup if the user has selected an unoccupied talkgroup.  
      In an exemplary embodiment, the subscriber unit has an internal programmable delay which allows the user&#39;s talkgroup selection to be settled before the indicator is broadcast. Thus, there is a delay between the time a user selects a talkgroup and the time that the subscriber unit transmits the selected talkgroup to the system controller.  
      Referring now to  FIG. 2 , a flow diagram showing the steps taken by one of the subscriber units in accordance with an exemplary embodiment of the invention is shown. In step  202 , the subscriber unit (for example a subscriber unit in talkgroup “A”) enters a repeater site area (for example repeater  106 ). In step  204 , the subscriber unit transmits a unit id and talkgroup id to the system controller  104  for authorization. This information comes to the system controller  104  as an inbound signaling communication. The information is then used by the system controller  104  to update a database of subscribers  116  which stores information on all the subscriber units in the system  100  and their current talkgroup affiliations. An automatic affiliation routine may also be performed by the subscriber units when they leave a service area, leave a talkgroup, or leave a repeater site. In step  206 , the system controller  206  authorizes the subscriber unit for communication.  
      In step  208 , the system controller  104  determines whether other subscriber units are in the talkgroup. If there are other subscriber units in the talkgroup, then in step  214  the subscriber unit places/receives talkgroups. If there are no other subscriber units in the talkgroup, then in step  210 , the system controller  104  sends the subscriber unit an indication that there are no other subscriber units in the talkgroup. Further, in step  210 , an indication that there are no other subscriber units in the talkgroup is sent to the dispatch centre  114 . In step  212 , the subscriber unit provides an indication to the user that there are no other subscriber units in the selected talkgroup. Further, in step  212 , an indication that there are no other subscriber units in the talkgroups is shown on a dispatch console or workstation at the dispatch centre  114 . This indication may be by on screen indicators or other similar indication.  
      In summary, the present invention provides a method for determining whether a talkgroup is occupied. It allows the user to instantly know whether others are using the same talkgroup. By having such knowledge, users can “look out for each other” and provide assistance as necessary. Users will know if others have left the talkgroup and are currently in an unoccupied talkgroup. This invention greatly increases the safety of personnel, particularly for those operating in remote coverage areas of the trunked communication system  100 , or at late hours.  
      While the invention has been described in conjunction with specific embodiments thereof, additional advantages and modifications will readily occur to those skilled in the art. The invention, in its broader aspects, is therefore not limited to the specific details, representative apparatus, and illustrative examples shown and described. For example, the subscriber unit and/or the base radio may comprise a storage medium having stored thereon a set of instructions which, when loaded into a hardware device (e.g., a microprocessor), causes the hardware device to perform the following functions of the present invention. The present invention can be implemented in at least one of hardware, firmware and/or software. Various alterations, modifications and variations will be apparent to those skilled in the art in light of the foregoing description. Thus, it should be understood that the invention is not limited by the foregoing description, but embraces all such alterations, modifications and variations in accordance with the spirit and scope of the appended claims.  
      It should be noted that the terms “a” or “an”, as used herein, are defined as one or more than one. The term “plurality”, as used herein, is defined as two or more than two. The term “another”, as used herein, is defined as at least a second or more. The terms “including” and/or “having”, as used herein, are defined as comprising (i.e., open language).