Method for collision avoidance in an asynchronous communication system

A method of avoiding collisions between transmission signals in a frequency hopping spread spectrum communications system comprising a plurality of transmitters and at least one receiver, each said transmitter including means for initiating and transmitting a message to said at least one receiver, each transmitter utilizing the same pseudo random hop sequence of N frequencies, said method comprising the steps of:

• transmitting each message N times, each message transmission occurring during a different time slot wherein transmissions during each time slot are assigned different frequencies;
• dividing each time slot into a plurality of M sub time slots;
• randomly selecting one and only one of said M sub time slots in which to transmit said message such that the time delay between successive transmissions during each time slot is random;
• transmitting said message during said randomly selected sub time slot;
• wherein each transmitter messages asynchronously with respect to and independently of transmissions from all other transmitters;
• wherein burst time slot timing for each message is determined independently by each transmitter asynchronous to other transmitters and without the use of any system time slot synchronization;
• and
• wherein N and M are positive integers and M is equal to or greater than 2.

A communications transmitter, comprising;

• means for transmitting a message a predetermined number of times N, each message transmission occurring during a time slot within a burst of N time slots;
• means for dividing each time slot into a plurality of M sub time slot;
• means for randomly selecting one of said M sub time slots in which to transmit said message such that the time delay between successive transmissions during each time slot is random;
• means for transmitting said message during said randomly selected sub time slot;
• means for transmitting messages asynchronously with respect to and independently of transmissions from all other transmitters;
• means for determining burst time slot timing for each message independently by each transmitter asynchronous to other transmitters and without the use of any system time slot synchronization;
• and
• wherein N and M are positive integers and M is equal to or greater than 2.