Different communications between two or more MC service users need to be distinguished in their urgency in order to appropriately or less preferably allocate 3GPP system transport resources. Also simultaneous incoming communications to a MC service user requires an indication of the urgency in order to preferentially join the communication in accordance with the urgency.
To make this distinction of urgencies, the MC system necessarily supports different types of priorities and corresponding levels within each priority category representing the relative importance of a request at the application level. The use of application priority allows the MC system to decide whether a communication establishment or modification request can be accepted or needs to be rejected (e.g. in case of transport resource limitations), or it allows the MC service client to rank simultaneous incoming communication for presentation to an MC service user. Hence the application priority can also be used to decide which existing transport resources (e.g. bearers) to pre-empt during resource limitations. Such pre-emption capability information defines whether a communication can obtain transport resources that were already assigned to another communication with a lower priority level. The pre-emption vulnerability information defines whether a communication can lose the resources assigned to it in order to admit a communication with higher priority level.
The following types of application priorities are provided by the MC system:
Communication priority involves a combination of the type of call/communication, the role of the requesting MC service user, and the predefined/requested priority of the initiating MC service user and/or group.
Presentation priority involves the determination of which communications, from within multiple simultaneous possible, are the highest priority to present to the MC service user either audibly or visibly. An example would be a private call received at the same time as an emergency call on a monitored group. This category can be configured uniquely for each MC service user.
Floor priority involves the determination of who can transmit within a communication at a particular time. This is essentially the priority of the MC service user according to its profile, and possibly modified by its role and/or mode of service (e.g. using emergency or imminent peril call). This category is used, for example, to determine the ordering of the floor control queue within an established communication.