Collision avoidance methods and apparatus for intercommunication systems

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

• (1) broadcasting a paging request from a paging subscriber to one of paged subscribers on a control frequency band, wherein the paging request comprises an identification number of one of the paged subscribers, synchronization information, and traffic types;
• (2) when one of the paged subscribers receives a corresponding paging request on the control frequency band, sending a paging acknowledgement from one of the paged subscribers to the paging subscriber in turn on the control frequency band, wherein the paging acknowledgement comprises a measurement report of a traffic frequency band and a receiving signal quality;
• (3) designating a physical channel of the traffic frequency band for the multi-party conversation, and then starting the multi-party conversation by the paging and paged subscribers on the designated physical channel of the traffic frequency band, wherein the designation comprises the paging subscriber determining all paged subscribers participating in the multi-party conversation after receiving the paging acknowledgement of one of the paged subscribers, and then selecting a time slot in the traffic frequency band as the physical channel for the multi-party conversation based on the measurement report of the traffic frequency band of one of the paged subscribers, and then broadcasting the selection to the paged subscribers, and wherein starting the multi-party conversation comprises the paging subscriber firstly speaking as a transmitting subscriber, and then broadcasting an encoded voice information frame, and then the paged subscribers receiving the encoded voice information frame as receiving subscribers;
• (4) after finishing the speak on the physical channel, sending a frame of instructions from the transmitting subscriber to the receiving subscribers for declaring a beginning of a fight-for phase;
• (5) in a first subset of frame moments during the fight-for phase, broadcasting maintenance information by the transmitting subscriber via the physical channel to the receiving subscribers;
• (6) in a second subset of the frame moments during the fight-for phase, broadcasting a fight request message for the right to speak by the receiving subscribers intending to obtain the right to speak via pressing a button on a corresponding device in turn, wherein the fight-for phase is not closed until at least one of the receiving subscribers sends out the fight request message, and wherein the first and second subsets of the frame moments are based on a same odd and even time-division multiplexing relationship;
• (7) ceasing fighting for the right to speak by the other receiving subscribers after hearing the fight request message on the physical channel;
• (8) starting a speak by one of the receiving subscribers, as a new transmitting subscriber, which has obtained the right to speak via the physical channel, wherein the original transmitting subscriber becomes a new receiving subscriber;
• and
• (9) repeating the steps (4) to (8) for completing a subsequent switch of the right to speak.