Collision avoidance methods and apparatus for intercommunication systems

A collision avoidance method for subscribers to fight for the right to speak of a multi-party conversation in a digital intercommunication system, comprising:

• broadcasting a paging request from a paging subscriber to paged subscribers on a control frequency band;
• when paged subscribers receive the paging request, sending paging acknowledgements from the paged subscribers to the paging subscriber on the control frequency band;
• designating a time slot in a traffic frequency band as a designated physical channel for the multi-party conversation and broadcasting the designation to the paged subscribers;
• switching to the designated physical channel by the paging and paged subscribers and starting the multi-party conversation, the paging subscriber becoming a transmitting subscriber and the paged subscribers becoming receiving subscribers;
• after finishing transmission, broadcasting a frame of control instructions from the transmitting subscriber to declare a beginning of a fight-for phase;
• in a subset of frame moments during the fight-for phase, sending maintenance information by the transmitting subscriber via the physical channel to the receiving subscribers;
• in another subset of the frame moments during the fight-for phase, sending a request for the right to speak by at least one of the receiving subscribers via the physical channel, the fight-for phase not closing until at least one of the receiving subscribers sends out a request message;
• hearing the request message on the physical channel, ceasing fighting for the right to speak by the other receiving subscribers;
• handing over the right to speak from the transmitting subscriber to the at least one receiving subscriber that has successfully sent out the request message, the transmitting subscriber becoming a new receiving subscriber and the at least one receiving subscriber who has obtained the right to speak becoming a new transmitting subscriber;
• and
• starting a new round during which the new transmitting subscriber begins to speak.