Method and system for contention resolution in radio frequency identification systems

A passive identification system comprising, in combination:

• a reader;
• a plurality of passive identification tags, each tag having a respective identification value, and each tag having a register value within a predetermined range;
• the reader being arranged to send a first range-instruction to the tags, the first range-instruction defining a preset value indicative of a first range of register values;
• each tag being arranged to receive the first range-instruction, to determine whether the tag's register value falls within the first range, and, in response to a determination that the tag's register value falls within the first range, to emit a signal defining the tag's respective identification value;
• the reader being further arranged to detect a contention and to responsively split the first range into a plurality of second ranges and to send a plurality of second range-instructions to the tags, each second range-instruction defining a preset value indicative of a respective second range of the plurality of second ranges;
• and
• each tag being further arranged to receive each second range-instruction, to determine whether the tag's register value falls within the second range defined by the preset value of the second range-instruction, and, in response to a determination that the tag's register value falls within the second range defined by the preset value of the second range-instruction, to emit a signal defining the tag's respective identification value.