Transponder signal collision avoidance system
First Claim
1. A transponder signal collision avoidance system comprising a reader and a plurality of wireless transponders for being interrogated by the reader within a wireless interrogation field, the reader being adapted for interrogating by transmitting power pulses through a number of cycles corresponding to a number of possible transponders in the field, the number of cycles corresponding to the addresses of each of respective possible transponders, the transponders each being adapted to respond to the reader by transmission only in response to a number of cycles determined by the transponders as corresponding to the address of the respective transponder, whereby to prevent the transponders from transmitting respective messages without interfering with each other.
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Accused Products
Abstract
Transponder signal collision avoidance system incudes a reader and wireless HDX or FDX type transponders (A, B) are disclosed, interrogated by the reader (R) by alternately powering and then reading through cycles corresponding to a number of possible transponders in the interrogation field. The cycles, which include reader power pulses, signify addresses of respective possible transponders, whether in or out of the field. The transponders for this purpose count reader power pulses by end-of-burst detection, increasing a stored count value with each reader power pulse. The transponder responds to the reader by transmission if and only if a stored count value in a read cycle matches a respective transponder address, preventing the transponders from transmitting telegrams interfering with each other. As a method of reader-transponder operation, the collision avoidance scheme thus cycles the reader interrogating through cycles having power pulses according to possible transponders in the field, not only calling the addresses of each of respective possible transponders but also shortening or lengthening read and power steps dependent upon responses received from the transponders.
154 Citations
21 Claims
- 1. A transponder signal collision avoidance system comprising a reader and a plurality of wireless transponders for being interrogated by the reader within a wireless interrogation field, the reader being adapted for interrogating by transmitting power pulses through a number of cycles corresponding to a number of possible transponders in the field, the number of cycles corresponding to the addresses of each of respective possible transponders, the transponders each being adapted to respond to the reader by transmission only in response to a number of cycles determined by the transponders as corresponding to the address of the respective transponder, whereby to prevent the transponders from transmitting respective messages without interfering with each other.
- 11. A method of wireless reader-transponder operation for interrogating possible transponders in a wireless field by the use of a reader and controlling respective ones of the transponder such as to avoid signal collision of transmissions from the respective transponders when interrogated by the reader comprising operating the reader by interrogating by transmitting power pulses through a number of cycles corresponding to a number of possible transponders in the field, the cycles corresponding to the addresses of each of respective possible transponders, and selectively permitting the respective transponders to respond to the reader by transmission only in response to a count of power pulses corresponding to the address of the respective transponder, whereby transponders in the field transmit respective messages sequentially without interfering with each other.
- 20. A method of wireless reader-transponder operation for transponder signal collision avoidance comprising providing a reader and a plurality of wireless transponders for being interrogated by the reader within a wireless interrogation field, cycling the reader interrogating by transmitting power pulses through a plurality of cycles of interrogation of possible transponders in the field, the cycles calling the addresses of each of respective possible transponders, causing the transponders each to respond to the reader by transmission only in response to a received address of the respective transponder, whereby to prevent the transponders from transmitting respective messages without interfering with each other.
Specification