Establishing a group call in a mobile radio system

A mobile radio system for establishing a group call extending into the respective service areas of a plurality of exchanges, comprising:

• a plurality of exchanges, including a first and a second exchange each having a respective source area,
• a plurality of mobile stations communicating via said exchanges, including via said first and second exchanges,
• a telecommunication transmission medium for establishing a group call between said first and second exchanges,
• a database which indicates, for each group call, the telecommunication transmission medium that is allocated for the respective said group call on each connection from said first to said second exchange,
• checking means for checking whether a telecommunication transmission medium has been previously allocated on the respective said connection from said first to said second exchange for said group call to be established,
• said checking means being arranged to:
• (a) allocate a telecommunication transmission medium on said connection between said first and said second exchange for said group call to be established, if said database indicates that no telecommunication transmission medium has been previously allocated for said group call on said connection between said first and said second exchange, and
• (b) route said group call to be established from the first to the second exchange respectively via said allocated or previously allocated telecommunication transmission medium.

A mobile radio system for establishing a group call extending into the respective service areas of a plurality of exchanges, comprising:

• a plurality of exchanges, including a first and a second exchange each having a respective source area,
• a plurality of mobile stations communicating via said exchanges, including via said first and second exchanges,
• a telecommunication transmission medium for establishing a group call between said first and second exchanges,
• a database which indicates, for each group call, the telecommunication transmission medium that is allocated for the respective said group call on each connection from said first to said second exchange,
• checking means for checking whether a telecommunication transmission medium has been previously allocated on the respective said connection from said first to said second exchange for said group call to be established,
• means for marking allocation of the telecommunication transmission medium between said first and said second exchange in said database, if said database, upon checking of said check means does not indicate that the telecommunication transmission medium has been previously allocated for said group call on said connection between said first and second exchanges .