Array of very light readers for active RFID and location applications
View Patent ↗An example method includes estimating whether a collision occurred between a plurality of wide band response signals, the wide band response signals being responsive to a first interrogation signal transmitted by a first reader; when the collision is estimated to have occurred and the first reader received a first response from a particular tag, transmitting, by the first reader, a second interrogation signal, the second interrogation signal initiating a communication session between the reader and the particular tag; and transmitting, by the first reader, an acknowledgement packet to cause the tag to refrain from responding to a command during the communication session; and a second reader to refrain from interrogating the particular tag during the communication session.
1. A method comprising:
estimating whether a collision occurred between a plurality of wide band response signals at a first reader, the wide band response signals being responsive to a first interrogation signal transmitted by the first reader;
when the collision between the plurality of wide band response signals at the first reader is estimated to have occurred and the first reader received a first response from a first one of a plurality of tags:
transmitting, by the first reader, a second interrogation signal, the second interrogation signal initiating a communication session between the first reader and the first tag; and
transmitting, by the first reader, an acknowledgement packet to cause:
the first tag to refrain from responding to a command during the communication session; and
a second reader to refrain from interrogating the first tag during the communication session.
2. A method as defined in claim 1 , further comprising limiting the first reader to receive replies having a combined reader transmission and tag reply time-of-flight within a predetermined amount of time.
3. A method as defined in claim 1 , further comprising determining a round trip delay time of individual ones of the plurality of wide band response signals.
4. A method as defined in claim 1 , further comprising estimating a quantity of the plurality of wide band response signals.
5. A system comprising:
a tag configured to receive a first interrogation signal and to transmit a first wide band response signal in response to the first interrogation signal;
a first reader to transmit the first interrogation signal and to receive a plurality of wide band response signals including the first wide band response signal from the tag, the first reader configured to, in response to an estimation that a collision occurred between the plurality of response signals at the first reader:
transmit a second interrogation signal to initiate a communication session between the first reader and the tag; and
transmit an acknowledgment packet to cause the tag to refrain from responding to a command during the communication session; and
a second reader configured to, in response to receiving the acknowledgement packet, refrain from interrogating the tag during the communication session.
6. A system as defined in claim 5 , wherein the tag is a wide-band active RFID tag comprising:
a Very-Large-Scale Integration (VLSI) chip integrating an ultra wide band (UWB) front end with a digital transceiver;
a UWB antenna;
a power supply; and
a clock source.
7. A system as defined in claim 5 , further comprising a central network controller to dynamically determine overlapping coverage between the first and second readers by analyzing responses of the tag and other tags.
8. A system as defined in claim 5 , wherein the first reader is configured to determine a round trip delay time of individual ones of the plurality of wide band response signals.
9. A system as defined in claim 5 , wherein the first reader is to estimate a quantity of the plurality of wide band response signals.
10. A first reader, comprising:
communication hardware to:
transmit a first interrogation signal; and
receive a plurality of response signals in response to the first interrogation signal, the plurality of response signals including a first response signal from a tag; and
a processor to:
when a collision is estimated to have occurred between the plurality of response signals:
provide a second interrogation signal to be transmitted by the communication hardware, the second interrogation signal to initiate a communication session between the first reader and the tag; and
provide an acknowledgement packet to be transmitted by the communication hardware, the acknowledgement packet to prohibit:
the tag from responding to a command during the communication session; and
a second reader from interrogating the tag during the communication session.
11. A first reader as defined in claim 10 , further comprising:
a controller configured to implement a Media Access Control (MAC) protocol; and
a communication interface subsystem configured to operate with the controller, wherein the communication interface subsystem is to provide connection to a network through a channel separate from the tag.
12. A first reader as defined in claim 11 , wherein the communication interface subsystem providing connection to the network includes communication via one or more of WiFi, Wimax, UWB, power lines, Bluetooth®, or Ethernet.
13. A first reader as defined in claim 10 , further comprising a tag module having at least one VLSI chip integrating a UWB front end and digital transceiver.
14. A first reader as defined in claim 10 , wherein the processor is to determine a round trip delay time for individual ones of the plurality of response signals.
15. A first reader as defined in claim 10 , wherein the processor is to estimate a quantity of the plurality of wide band response signals.