MEDIA ACCESS CONTROL (MAC) FOR AN ACTIVE RFID SYSTEM

• US 20090185505A1
• Filed: 01/23/2008
• Published: 07/23/2009
• Est. Priority Date: 01/23/2008
• Status: Active Grant

• Current Assignee: Zebra Technologies Corporation
• Original Assignee: Sandlinks Systems Ltd.
• Inventors: Raphaeli, Dani, RIPSTEIN, Idit, Soffer, Yaron, Kaplan, Gideon
• Granted Patent: US 8,422,398 B2
• Time in Patent Office: Days
• US Class Current: 370/254
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs
• CPC Class Codes: G06K 7/0008 General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer
• CPC Class Codes: G06K 7/10039 interrogator driven, i.e. synchronous
• CPC Class Codes: G06K 7/10366 the interrogation device being adapted for miscellaneous applications
• CPC Class Codes: H04L 2101/604 Address structures or formats
• CPC Class Codes: H04L 2101/622 Layer-2 addresses, e.g. medium access control [MAC] addresses
• CPC Class Codes: H04L 69/324 in the data link layer [OSI layer 2], e.g. HDLC
• CPC Class Codes: H04W 52/0219 where the power saving management affects multiple terminals
• CPC Class Codes: H04W 74/004 in the uplink, i.e. towards network
• CPC Class Codes: H04W 74/006 in the downlink, i.e. towards the terminal
• CPC Class Codes: H04W 8/26 Network addressing or numbering for mobility support
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A system of radio frequency communication between Readers and Tags, the system comprising at least one tag Reader and a plurality of Tags, each tag is given a unique tag ID, deployed in a region in which at least some of the Tags are in radio communication with the tag Reader and a Media Access Control protocol such that the tag Reader is configured to send and receive radio communication to and from at least some of the plurality of Tags. The plurality of Tags are configured to send and receive radio communication to and from the tag Reader and the Media Access Control protocol is configured to control the radio communication between the tag Reader and the plurality of Tags The Media Access Control protocol includes a multi-dimensional addressing scheme allowing Readers to efficiently address tag communities ranging from small to very large in unicast, multicast and broadcast modes. The multi-dimensional addressing scheme enables division of the plurality of Tags into a number of groups for different stages of Media Access Control protocol processing, based on different portions of the tag ID. A hash function is used to transform the tag ID into a pseudo random ID, so as to achieve better spreading of tag population and lower statistical dependency between dimensions. The MAC has an inherent flexibility in the sense that it allows readers to communicate with different versions of tags and also to optimize communication parameters to reader'"'"'s capabilities, without pre-configuration of the tags. Furthermore, the MAC supports means to achieve very high access reliability, such as relay between tags, and the ability to work with tags that alternate between active and sleep mode) including means for power savings. All of these novel features, coupled with some prior art concepts like collision resolution algorithms, result in a scalable MAC protocol for an active RFID system employing multiple access.

Claims

1. A system of radio frequency communication between Readers and Tags, the system comprising;

(a) at least one tag Reader;

(b) a plurality of Tags deployed in a region in which at least some of the Tags are in radio communication with said tag Reader, and each tag is given a unique tag ID, and

(c) a Media Access Control protocol such that said tag Reader is configured to send and receive radio communication to and from at least some of said plurality of Tags, said plurality of Tags are configured to send and receive radio communication to and from said tag Reader and said Media Access Control protocol is configured to control said radio communication between said tag Reader and said plurality of Tags, and said Media Access Control protocol includes a multi-dimensional addressing scheme allowing Readers to efficiently address tag communities ranging from small to very large in unicast, multicast and broadcast modes, said multi-dimensional addressing scheme enables division of said plurality of Tags into a number of groups for different stages of Media Access Control protocol processing, based on different portions of said tag ID.

2. The system of claim 1, wherein a hash function is used to transform said tag ID into a pseudo random ID, so as to achieve better spreading of tag population and lower statistical dependency between dimensions.

3. The system of claim 2, wherein a portion of said tag ID is used for message screening in the PHY level and thereby avoid a need for at least one tag in said plurality of Tags to fully process a Media Access Control protocol portion of said radio communication.

4. The system of claim 1, wherein a portion of said tag ID is used for setting the on/off timing of at least one tag in said plurality of Tags.

5. The system of claim 1, wherein a portion of the ID is used by at least one tag to choose one reply window out of a set of possible reply windows.

6. The system of claim 1, wherein a portion of the ID is used by said tag Reader as an acknowledgement to at least one Tag of said plurality of Tags that said tag Reader received a radio communication from said at least one Tag.

7. A system of radio frequency communication between Readers and Tags, the system comprising;

(a) at least one tag Reader;

(b) a plurality of Tags deployed in a region in which at least some of the Tags are in radio communication with said tag Reader, at least some tags are in radio communication with other Tags in said plurality of Tags and each tag is given a unique tag ID, and

(c) a Media Access Control protocol such that said tag Reader is configured to send and receive radio communication to and from at least some of said plurality of Tags, said plurality of Tags are configured to send and receive radio communication to and from said tag Reader and other Tags in said plurality of Tags and said Media Access Control protocol is configured to control said radio communication between said tag Reader and said plurality of Tags, such that said Media Access Control protocol uses a combination of a session ID, acknowledgements and use of other tags as relays to achieve high reliability of radio communication, in broadcast, multicast and unicast modes.

8. The system of claim 7, wherein a portion of said tag ID is used by said tag Reader to indicate to at least one tag of said plurality of Tags that said tag Reader received a said radio communication from that particular tag.

9. The system of claim 7, wherein said tag Reader initiates a relay session after a rate of direct replies from said plurality of tags falls below a predetermined threshold.

10. The system of claim 7, wherein each broadcast message is given a session ID, and at least one tag of said plurality of tags replies to radio communications having a particular session ID until said at least one tag receives an acknowledgement radio communication having the same session ID.

11. A system of radio frequency communication between Readers and Tags, the system comprising;

(a) at least one tag Reader;

(b) a plurality of Tags deployed in a region in which at least some of the Tags are in radio communication with said tag Reader, at least some tags are in radio communication with other Tags in said plurality of Tags and

(c) a Media Access Control protocol such that said tag Reader is configured to send and receive radio communication to and from at least some of said plurality of Tags, said plurality of Tags are configured to send and receive radio communication to and from said tag Reader and other Tags in said plurality of Tags and said Media Access Control protocol is configured to control said radio communication between said tag Reader and said plurality of Tags;

wherein said Media Access Control protocol includes tag reply parameters in each said radio communication so as to enable tags to respond to said tag Reader in an optimal manner for that tag Reader'"'"'s capabilities.

12. The system of claim 11, wherein said radio communication includes an indication of the payload starting point, and each generation of tag Readers and/or Tags decode that portion of said Media Access Control protocol with which it is familiar, ignores that portion of said Media Access Control protocol with which it is unfamiliar and jumps to said payload start point, and said radio communication includes a block of variable length, such that old generation Tags forward said block without decoding, and new generation tag Readers and/or Tags decode and modify said block as needed.

13. A system of radio frequency communication between Readers and Tags, the system comprising;

(a) at least one tag Reader;

(b) a plurality of Tags deployed in a region in which at least some of the Tags are in radio communication with said tag Reader, and

(c) a Media Access Control protocol such that said tag Reader is configured to send and receive radio communication to and from at least some of said plurality of Tags, said plurality of Tags are configured to send and receive radio communication to and from said tag Reader and said Media Access Control protocol is configured to control radio said radio communication between said tag Reader and said plurality of Tags;

wherein said radio communication includes an indication of a payload start point, and each generation of tag Readers and/or Tags decode that portion of said Media Access Control protocol with which it is familiar, ignores that portion of said Media Access Control protocol with which it is unfamiliar and jumps to said payload start point, allowing reader to efficiently communicate with a mixture of tag generations and/or tag versions.

14. A system of radio frequency communication between Readers and Tags, the system comprising;

(a) at least one tag Reader;

(b) a plurality of Tags deployed in a region in which at least some of the Tags are in radio communication with said tag Reader, at least some tags are in radio communication with other Tags in said plurality of Tags and

(c) a Media Access Control protocol such that said tag Reader is configured to send and receive radio communication to and from at least some of said plurality of Tags, said plurality of Tags are configured to send and receive radio communication to and from said tag Reader and other Tags in said plurality of Tags and said Media Access Control protocol is configured to control said radio communication between said tag Reader and said plurality of Tags;

wherein said radio communication includes a block of variable length, such that old generation Tags forward said block without decoding, and new generation tag Readers and/or Tags decode and modify said block as needed.

15. The system of claim 14, wherein said radio communication includes an indication of payload start point, and each generation of tag Readers and/or Tags decode that portion of said Media Access Control protocol with which it is familiar, ignores that portion of said Media Access Control protocol with which it is unfamiliar and jumps to said payload start point, allowing reader to efficiently communicate with a mixture of tag generations and/or tag versions.