Method, transponder, and circuit for selecting one or more transponders
View Patent ↗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 comprising:
generating at a transponder by a random number generator a random number in an operating mode for generating random numbers;
switching, in response to receiving a selection command from a base station, the random number generator to a counter operating mode, the random number generator configured, in the counter operating mode, as a counter without using a separate counter for implementing the counter operating mode;
modifying, when the random number generator is in the counter operating mode and in response to receiving from the base station a signal corresponding to a start of a time slot, a count state of the random number generator from an initial value to a modified value without using a separate counter for implementing the counter operating mode; and
transmitting, when the count state is a predetermined value, an identification corresponding to the transponder.
2. The method of claim 1 , further comprising switching the random number generator from the counter operating mode to the operating mode for generating random numbers in response to one or more of the following:
the count state being the predetermined value; and
transmitting, when the count state is the predetermined value, the identification corresponding to the transponder.
3. The method of claim 1 , further comprising:
receiving an acknowledge command from the base station subsequent to transmitting the identification; and
delaying, in response to receiving the acknowledgement command from the base station subsequent to transmitting the identification, switching the random number generator from the counter operating mode to the operating mode for generating random numbers.
4. The method of claim 3 , comprising delaying, in response to receiving the acknowledgement command from the base station subsequent to the transmitting the identification, switching the random number generator from the counter operating mode to the operating mode for generating random numbers until receiving an appropriate subsequent command from the base station that causes the random number generator to switch, in response to receiving the appropriate subsequent command from the base station, from the counter operating mode to the operating mode for generating random numbers.
5. The method of claim 1 , further comprising:
receiving an acknowledge command from the base station subsequent to the transmitting the identification; and
allowing, in response to receiving the acknowledge command, a write or read operation on the transponder.
6. The method of claim 1 , wherein the random number generator is configured as:
a linear feedback shift register in the operating mode; and
a ripple counter in the counter operating mode.
7. The method of claim 1 , further comprising monitoring the count state after the signal corresponding to the start of the time slot.
8. The method of claim 1 , comprising:
setting the initial value of the count state of the random number generator in the counter operating mode to the random number generated by the random number generator in the operating mode for generating numbers prior to switching the random number generator from the operating mode to the counter operating mode; and
modifying, by the random number generator in the counter operating mode and in response to receiving from the base station the signal corresponding to the start of the time slot, the count state from the initial value to the modified value.
9. The method of claim 1 , comprising:
storing the random number generated by the random number generator in the operating mode;
setting the initial value of the count state of the random number generator in the counter operating mode to an initial count state value, wherein the predetermined value is a stored random number; and
modifying, by the random number generator in the counter operating mode and in response to receiving from the base station the signal corresponding to the start of the time slot, the count state from the initial count state value to the modified value.
10. A transponder comprising:
a random number generator having an operating mode for generating random numbers and a counter operating mode in which the random number generator is configured as a counter without using a separate counter for implementing the counter operating mode, the random number generator configured to:
generate, when the random number generator is in the operating mode, a random number; and
modify, when the random number generator is in the counter operating mode and in response to receiving from a base station a signal corresponding to a start of a time slot, a count state of the random number generator from an initial value to a modified value without using a separate counter for implementing the counter operating mode;
a control unit configured to switch, in response to receiving a selection command from the base station, the random number generator from the operating mode to the counter operating mode; and
a detection unit configured to transmit, when the count state is a predetermined value, an identification corresponding to the transponder.
11. The transponder of claim 10 , wherein the control unit is further configured to switch the random number generator from the counter operating mode to the operating mode for generating random numbers in response to one or more of the following:
the count state being the predetermined value; and
transmitting, when the count state is the predetermined value, the identification corresponding to the transponder.
12. The transponder of claim 10 , further configured to:
receive an acknowledge command from the base station subsequent to transmitting the identification; and
delay, in response to receiving the acknowledgement command from the base station subsequent to transmitting the identification, switching the random number generator from the counter operating mode to the operating mode for generating random numbers.
13. The transponder of claim 12 , configured to delay, in response to receiving the acknowledgement command from the base station subsequent to the transmitting the identification, switching the random number generator from the counter operating mode to the operating mode for generating random numbers until receiving an appropriate subsequent command from the base station that causes the random number generator to switch, in response to receiving the appropriate subsequent command from the base station, from the counter operating mode to the operating mode for generating random numbers.
14. The transponder of claim 10 , wherein the control unit is further configured to:
receive an acknowledge command from the base station subsequent to the transmitting the identification; and
allow, in response to receiving the acknowledge command, a write or read operation on the transponder.
15. The transponder of claim 10 , wherein the random number generator is configured as a linear feedback shift register in the operation mode.
16. The transponder of claim 10 , wherein the random number generator is configured as a ripple counter in the counter operating mode.
17. The transponder of claim 10 , wherein the detection unit is further configured to monitor the count state after the signals corresponding to the start of the time slot.
18. The transponder of claim 10 , wherein:
an initial count state of the random number generator in the counter operating mode is the random number generated by the random number generator in the operating mode for generating numbers prior to switching the random number generator from the operating mode to the counter operating mode; and
the random number generator in the counter operating mode is configured to modify, in response to receiving from the base station the signal corresponding to the start of the time slot, the count state from the initial value to the modified value.
19. The transponder of claim 10 , configured to:
store the random number generated by the random number generator in the operating mode;
set the initial value of the count state of the random number generator in the counter operating mode to an initial count state value, wherein the predetermined value is the stored random number; and
modify, by the random number generator in the counter operating mode and in response to receiving from the base station the signal corresponding to the start of the time slot, the count state from the initial count state value to the modified value.
20. A circuit configured to:
generate at a transponder by a random number generator a random number in an operating mode for generating random numbers;
switch, in response to receiving a selection command from a base station, the random number generator to a counter operating mode, the random number generator configured, in the counter operating mode, as a counter without using a separate counter for implementing the counter operating mode;
modify, when the random number generator is in the counter operating mode and in response to receiving from the base station a signal corresponding to a start of a time slot, a count state of the random number generator from an initial value to a modified value without using a separate counter for implementing the counter operating mode; and
transmit, when the count state is a predetermined value, an identification corresponding to the transponder.