ARRAY OF VERY LIGHT READERS FOR ACTIVE RFID AND LOCATION APPLICATIONS

• US 20100164690A1
• Filed: 02/28/2008
• Published: 07/01/2010
• Est. Priority Date: 03/01/2007
• Status: Active Grant

• Current Assignee: Zebra Technologies Corporation
• Original Assignee: Sandlinks Systems Ltd.
• Inventors: Ram, Uzi, Marinov, Izhar, Kaplan, Gideon, Menkes, Abraham, Raphaeli, Dani, Sela, Guy
• Granted Patent: US 9,307,554 B2
• Time in Patent Office: Days
• US Class Current: 340/10.200
• 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 low cost RFID Very Light Reader device comprising:

(a) a wide-band Active RFID Tag;

(b) a controller configured to implement the Media Access Control (MAC) protocol of the system; and

(c) a communication interface subsystem that provides connection to a system network.

2. The device of claim 1, wherein said wide-band Active RFID Tag includes:

(a) at least one VLSI chip integrating a UWB front end and high speed digital transceiver;

(b) a UWB Antenna;

(c) a power supply; and

(d) a clock source.

3. The device of claim 1, wherein said system network includes communication via any one communication protocol or media, or a combination any from a list that includes:

Wifi, Wimax, UWB, power lines, Bluetooth®

, Ethernet.

4. A modular wide-band RFID Very Light Reader device comprising;

(a) at least one Tag module having at least one VLSI chip integrating a UWB front end and high speed digital transceiver; and

(b) a base module configured for interconnection with a plurality of said Tags modules, said base module having at least;

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

(ii) a communication interface subsystem that provides connection to a system network.

5. The device of claim 4, wherein said base module is configured for interconnection with more than one Tag module so as to increase reception capabilities of the modular wide-band RFID Very Light Reader.

6. The device of claim 4, wherein said Tag module also includes:

(i) a UWB antenna;

(ii) a power supply; and

(iii) a clock source.

7. The device of claim 4, wherein said base module also includes:

(iii) a UWB Antenna, such that all Tags interconnected to said base module share said UWB antenna;

(iv) a power supply; and

(v) a clock source.

8. A method used by a UWB active RFID system, to determine which tags are located near a reader, the method comprising, limiting a 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.

9. A method for implementing an Active RFID system that employs communication between Readers in order to improve the Backhaul reliability by utilizing reader reception overlap, the method comprising:

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

10. A method of reducing the collision occurrence in a network for communicating between multiple readers and a plurality of RF tags, the method comprising the steps of:

(a) transmission by at least one Reader of at least one wide band interrogation signal;

(b) reception of said interrogation signal by at least one Tag;

(c) transmission by said Tag of a response signal in response said interrogation signal;

(d) reception of said response signal by said Reader;

(e) estimation by said Reader as to a quantity of wide band response signals received in response to said interrogation signal;

(f) determination by said Reader of a round trip delay time of each said response signal;

(g) estimation by said Reader as to whether a collision between a plurality of the wide band response signals occurred and if so,

(i) transmission by said Reader of at least one additional wide band interrogation signal, said additional wide band interrogation signal initiating a new communications session between said Reader and said at least one RF Tag in order to reduce the collision probability between the wide band response signals transmitted by the Tags; and

(h) transmission by said Reader of an acknowledgment packet to said responding Tag such that,

(i) said 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

(ii) at least one other such Reader in the network receives said acknowledge packet such that said other Reader will not try again to reach said Tag, thereby lowering congestion directed toward said Tag from multiple Reader transmissions.

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

(a) at least one Tag configured to receive at least one wide band interrogation signal, transmit a response signal in response said interrogation signal;

(b) at least one Reader configured to transmit said interrogation signal and receive said response signal, said Reader further configured to;

(i) estimate a quantity of wide band response signals received in response to said interrogation signal;

(ii) determine a round trip delay time of each said response signal;

(iii) estimate as to 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, said additional wide band interrogation signal initiating a new communications session between said Reader and said at least one RF Tag in order to reduce the collision probability between the wide band response signals transmitted by the Tags; and

(iv) transmit an acknowledgment packet to said responding Tag such that, said responding Tag 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

(c) at least a second Reader in the network configured to receive said acknowledge packet such that said second Reader will not try again to reach said Tag, thereby lowering congestion directed toward said Tag from multiple Reader transmissions.

12. A method by which a central network controller dynamically determines overlapping coverage between a plurality of Readers in the network, the method comprising:

analyzing at least one response of at least one Tag to at least one broadcast message from a first Reader wherein said response is received by more than one receiving Reader in the plurality of Readers and each said receiving Reader relays said 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 plurality of Readers in the network.

13. The method of claim 12, wherein said analyzing includes analyzing a plurality of responses from a plurality of Tags.