Array of very light readers for active RFID and location applications

• US 9,307,554 B2
• Filed: 02/28/2008
• Issued: 04/05/2016
• Est. Priority Date: 03/01/2007
• Status: Active Grant

• Current Assignee: Zebra Technologies Corporation
• Original Assignee: ZIH Corp. (Zebra Technologies Corporation)
• Inventors: Raphaeli, Dani, Sella, Guy, Ram, Uzi, Kaplan, Gideon, Menkes, Abraham, Marinov, Izhar
• Primary Examiner(s): Lim, Steven
• Assistant Examiner(s): LITTLEJOHN JR, MANCIL H
• Application Number:
  US12/523,734
• Publication Number:
  US 20100164690A1
• Time in Patent Office: 2,959 Days
• Field of Search: 455/41.2, 455/41.1, 455/552.1, 455/553.1, 455/556.1, 455/557, 455/456.1, 340 101- 106, 3405391-53932, 3405721-5728, 340/5.1
• US Class Current: 1/1
• CPC Class Codes: G06K 7/10019 resolving collision on the communication channels between simultaneously or concurrently interrogated record carriers. collision between the communication channels used by wireless communication devices, where the solution is not particularly adapted for RFIDs or the like, H04W74/08
• CPC Class Codes: G06K 7/10306 ultra wide band
• CPC Class Codes: G06K 7/10356 using a plurality of antennas, e.g. configurations including means to resolve interference between the plurality of antennas
• CPC Class Codes: H04W 74/00 Wireless channel access

Abstract

The Very Light Readers of the present invention are based on an augmented Tag circuit with a preferred embodiment including at least one VLSI chip integrating a UWB front end, digital transceiver, and possibly an internal controller; a UWB Antenna; a power supply; a controller configured to implement the Media Access Control protocol of the system; a Communication Interface subsystem for connection to the system network and a clock source. Also described is a system capable of reducing collision occurrence in a network for communicating between multiple readers and a plurality of RF Tags. Tags are configured to receive interrogation signals and transmit response signals. Readers are configured to transmit interrogation signals, receive response signals, estimate the quantity of responses received to an interrogation, determine the round trip delay time of each response and estimates whether a collision between responses has occurred. If so, the Reader transmits an additional interrogation signal. The Reader also transmits an acknowledgment packet to responding Tags so responding Tag will not answer again to that broadcast session. Other Readers in the network also receive the acknowledge packet and do not try again to reach the responding Tags, thereby lowering congestion directed toward Tags from multiple Reader transmissions.

Claims

1. A method of reducing collision occurrence in a network for communicating between multiple readers and a plurality of radio frequency (RF) tags, the method comprising:

transmitting by at least one reader of at least one wide band interrogation signal;

receiving a response signal from a tag in response the interrogation signal;

estimating, by the reader, a quantity of wide band response signals received in response to the interrogation signal;

determining, by the reader, a round trip delay time of each of the wide band response signals;

estimating, by the reader, whether a collision occurred between a plurality of the wide band response signals;

when the collision is estimated to have occurred, transmitting, by the reader, at least one additional wide band interrogation signal, the additional wide band interrogation signal initiating a new communications session between the reader and the tag to reduce a collision probability between wide band response signals transmitted by the plurality of RF tags; and

transmitting, by the reader, an acknowledgment packet to the tag such that;

the tag will not answer again to that broadcast session in case a broadcast command has to be re-transmitted due to an estimation that some collisions occurred during a previous session; and

at least one other reader in the network receives the acknowledgement packet such that the other reader will not try again to reach the tag, thereby lowering congestion directed toward the tag from multiple reader transmissions.

2. The method of claim 1 wherein:

upon transmission of a packet from the reader and subsequent reply to the packet from a tag, the reply is received by a second reader, the second reader relays the reply to a system server and informs the reader of receipt of the reply, whereupon the reader sends a second acknowledgement to the tag.

3. The method of claim 1, further comprising limiting the reader to receive replies from tags during predetermined time intervals so as to limit reception to replies whose combined reader transmission and tag reply time-of-flight falls within a predetermined length of time, such that replies are received only from tags that are located within a predetermined distance of the reader.

4. A system capable of reducing collision occurrence in a network for communicating between multiple readers and a plurality of radio frequency (RF) tags, the system comprising:

a first one of the tags configured to receive at least one wide band interrogation signal and transmit a response signal in response the interrogation signal;

a first one of the readers configured to transmit the interrogation signal and receive the response signal, the first one of the readers further configured to;

estimate a quantity of wide band response signals received in response to the interrogation signal;

determine a round trip delay time of each of the wide band response signals;

estimate whether a collision between a plurality of the wide band response signals occurred and if so, transmit at least one additional wide band interrogation signal, the additional wide band interrogation signal initiating a new communications session between the first one of the readers and the first one of the tags to reduce a collision probability between the wide band response signals transmitted by the tags; and

transmit an acknowledgment packet to the first one of the tags such that, the first one of the tags will not answer again to that broadcast session if a broadcast command is re-transmitted due to an estimation that some collisions occurred during a previous session; and

at least a second reader in the network configured to receive the acknowledgement packet such that the second reader will not try again to reach the first one of the tags, thereby lowering congestion directed toward the at least one tag from multiple reader transmissions.

5. A system as defined in claim 4, further comprising a central network controller to dynamically determine overlapping coverage between the multiple readers in the network by analyzing at least one response of at least one of the tags to at least one broadcast message from the first one of the readers wherein the at least one response is received by more than one receiving reader in the multiple readers and each said receiving reader relays the response to the central network controller such that the central network controller determines an extent of coverage overlap between at least some readers in the multiple readers in the network.

6. The system of claim 4, wherein the first one of the readers comprises:

a wide-band active RFID tag configured to transmit and receive in a wide-band radio frequency;

a controller configured to implement a Media Access Control (MAC) protocol; and

a communication interface subsystem configured to be operated with the controller, wherein the communication interface subsystem provides connection to a system network through a channel separate from the wide-band active RFID tag.

7. The system of claim 4, wherein the first one of the readers comprises;

(a) at least one tag module having at least one Very-Large-Scale Integration (VLSI) chip integrating an ultra wide band (UWB) front end and digital transceiver; and

(b) a base module configured for interconnection with a plurality of the at least one tag module, the base module having at least;

(i) a controller configured to implement a Media Access Control (MAC) protocol; and

(ii) a communication interface subsystem configured to be operated with the controller, wherein the communication interface subsystem that provides connection to a system network through a channel separate from a wide-band active RFID tag of the first one of the readers.

8. The system of claim 6, wherein the wide-band active RFID tag includes:

at least one 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.

9. The system of claim 6, wherein the communication interface subsystem providing connection to the system network includes communication via one or more of Wifi, Wimax, UWB, power lines, Bluetooth®

, or Ethernet.

10. The system of claim 7, wherein the base module is configured for interconnection with more than one tag module to increase reception capabilities of the modular wide-band RFID.

11. The system of claim 7, wherein the tag module includes:

(i) a UWB antenna;

(ii) a power supply; and

(iii) a clock source.

12. The system of claim 7, wherein the base module includes:

(iii) a UWB antenna, such that all tags interconnected to the base module share the UWB antenna;

(iv) a power supply; and

(v) a clock source.

13. The system of claim 5, wherein the analyzing includes analyzing a plurality of responses from the plurality of tags.

14. A reader to reduce collision occurrence in a network for communicating between multiple readers and a radio frequency tags, the reader comprising:

communication hardware to;

transmit a wide band interrogation signal; and

receive response signals from one or more of the tags, the response signals being responsive to the wide band interrogation signal; and

a processor to;

estimate a quantity of the wide band response signals received in response to the interrogation signal;

determine a round trip delay time of each of the wide band response signals;

estimate whether a collision occurred between the response signals;

when the collision is estimated to have occurred, provide at least one additional wide band interrogation signal to be transmitted by the communication hardware, the additional wide band interrogation signal configured to initiate a new communications session between the reader and the one or more of the tags to reduce a collision probability between response signals transmitted by the tags; and

provide an acknowledgment packet to the one or more of the tags such that;

the one or more of the tags will not answer again to that broadcast session in case a broadcast command has to be re-transmitted due to an estimation that some collisions occurred during a previous session; and

at least one other reader in the network receives the acknowledgement packet such that the other reader will not try again to reach the one or more of the tags, thereby lowering congestion directed toward the one or more of the tags from multiple reader transmissions.