Method for selecting one or more transponders

Abstract

A method and device for selecting one or more transponders, in particular backscatter-based transponders, from a plurality of transponders by a base station, which method is based on a slotted ALOHA method, in which the base station defines numbered time slots and a random number generated in a given transponder determines a time slot when the transponder transmits its transponder-specific identification to the base station. The random number is generated in a given transponder with the aid of a random number generator, the relevant random number generator is switched into a counter operating mode after reception of a selection command transmitted by the base station, while a count state of the random number generator is decremented or incremented when the base station transmits the start of a time slot, the relevant transponder transmits a transponder-specific identification to the base station if the count state of its random number generator is equal to a predetermined value, and the relevant random number generator is then switched back into the operating mode for random number generation.

1 . A method for selecting one or more transponders from a plurality of transponders by a base station, the method being based on a slotted ALOHA selection method in which the base station defines numbered time slots and a random number generated in a given transponder determines a time slot when the transponder transmits its transponder-specific identification to the base station, the method comprising the steps of: 
 generating in a transponder the random number by a random number generator;    switching the relevant random number generator into a counter operating mode after receipt of a selection command that is transmitted by the base station;    incrementing or decrementing a count state of the random number generator when the base station transmits the start of a time slot;    transmitting from the transponder a transponder-specific identification to the base station when the count state of its random number generator is equal to a predetermined value; and    switching the random number generator back into a operating mode for random number generation.    
     
     
         2 . The method according to  claim 1 , wherein the random number is generated by a linear feedback shift register.  
     
     
         3 . The method according to  claim 1 , wherein the switching into the operating mode for generating random numbers is dependent on whether the base station transmits an acknowledge command to the transponder following the transmission of the transponder-specific identification.  
     
     
         4 . The method according to  claim 1 , wherein an initial count state of the random number generator is the generated random number, and the transponder transmits its transponder-specific identification to the base station when the count state of its random number generator is zero.  
     
     
         5 . The method according to  claim 1 , wherein the generated random number is stored, then the count state of the random number generator is set to an initial value or zero, and the transponder transmits its transponder-specific identification to the base station when the count state is equal to the stored value of the random number.  
     
     
         6 . The method according to  claim 1 , wherein the transponders are backscatter-based transponders.  
     
     
         7 . A method for selecting a transponder, the method comprising the steps of: 
 detecting receipt of a selection command that is transmitted by a base station;    switching a random number generator in the transponder from a first operating mode to a second operating mode upon receipt of the selection command by the transponder;    detecting, by the transponder, a time slot command that is transmitted by the base station;    determining whether a count value of the random number generator is equal to a predetermined value;    transmitting, by the transponder, a transponder specific identification to the base station when the count value of the random number generator is equal to the predetermined value; and    incrementing or decrementing the count value of the random number generator when the count value is not equal to a predetermined value,    wherein, in the first operating mode, the random number generator generates a random number, the predetermined value being based on a value of the random number generated in the first operating mode, and    wherein, in the second operating mode, the random number generator increments or decrements the count value until the count value is equal to the predetermined value.    
     
     
         8 . A transponder comprising: 
 a zero detection unit for providing a transmission enable signal for initiating a transmission of a transponder specific identification signal to a base station; and    a random number generator having a first operating mode and a second operating mode, the random number generator generating a random number in the first operating mode, and the random number generator generating a count value in the second operating mode,    wherein the random number generator switches from the first operating mode to the second operating mode upon receipt of a selection signal transmitted from the base station, and    wherein the zero detection unit provides the transmission enable signal when the count value of the random number generator, during the second operating mode, is equal to a predetermined value.    
     
     
         9 . The transponder according to  claim 8 , wherein the predetermined value is zero.  
     
     
         10 . The transponder according to  claim 8 , wherein the random number generator increments or decrements the count value upon receipt of a time slot command signal that is transmitted by the base station.  
     
     
         11 . The transponder according to  claim 8 , wherein the random number generated by the random number generator in the first operating mode is an initial count value when the random number generator is switched into the second operating mode.  
     
     
         12 . The transponder according to  claim 8 , wherein the random number generator is switched from the second operating mode back to the first operating mode after the count value of the random number generator is equal to the predetermined value.  
     
     
         13 . The transponder according to  claim 8 , wherein the transponder receives an acknowledgement signal transmitted from the base station after transmission of the transponder specific identification signal.  
     
     
         14 . The transponder according to  claim 13 , wherein, after receipt of the acknowledgement signal, the transponder is selected so that the base station can perform write and/or read operations to the transponder.  
     
     
         15 . A communication system comprising: 
 at least one transponder that includes a random number generator that is switched between a first operating mode and a second operating mode, the random number generator generating a random number in the first operating mode, and the random number generator incrementing or decrementing a count value in the second operating mode; and    a base station for selecting the transponder and for performing write and/or read operations to the selected transponder,    wherein the random number generator switches from the first operating mode to the second operating mode upon receipt of a selection signal transmitted from the base station,    wherein the transponder transmit a transponder specific identification signal to the base station when the count value of the random number generator, during the second operating mode, is equal to a predetermined value,    wherein the base station transmits to the transponder an acknowledgement signal upon receipt of the transponder specific identification signal transmitted from the transponder, and    wherein the base station performs the write and/or read operations after the transponder receives the acknowledgement signal.    
     
     
         16 . The communication system according to  claim 15 , wherein the random number generator increments or decrements the count value in the second operating mode upon receipt of a time slot command signal that is transmitted by the base station.  
     
     
         17 . The communication system according to  claim 16 , wherein the base station transmits successive time slot command signals to the transponder until the transponder transmits the transponder specific identification signal to the base station.