# US 2014/0191847 A1 · Media access control (mac) for an active rfid system

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- Number: US 2014/0191847 A1
- Document ID: US20140191847A1
- Status: Published application
- Kind: A1
- Application number: 13/803,494
- Filed: 2013-03-14
- Published: 2014-07-10
- Earliest claimed: 2008-01-23
- Assignees: Zebra Enterprise Solutions Corp.
- Inventors: Idit Ripstein; Yaron Soffer; Dani Raphaeli; Gideon Kaplan
- Web page: https://patentgrep.com/patent/US20140191847A1

## CPC

- G06K 7/10366: {the interrogation device being adapted for miscellaneous applications}
- G06K 7/0008: {General problems related to the reading of electronic memory record carriers, independent of its reading method, e.g. power transfer}
- G06K 7/10039: {interrogator driven, i.e. synchronous}
- 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}
- H04L 69/324: in the data link layer [OSI layer 2], e.g. HDLC
- H04W 8/26: Network addressing or numbering for mobility support
- H04L 2101/604: Address structures or formats
- H04L 2101/622: Layer-2 addresses, e.g. medium access control [MAC] addresses
- H04W 52/0219: {where the power saving management affects multiple terminals}
- H04W 74/004: {in the uplink, i.e. towards network}
- H04W 74/006: {in the downlink, i.e. towards the terminal}
- Y02D 30/70: in wireless communication networks
- G06K: GRAPHICAL DATA READING (image or video recognition or understanding G06V); PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
- H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M)
- H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72)
- Y02D: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE

## Abstract

A system of radio frequency communication between Readers and Tags having a scalable Media Access Control (MAC) protocol for an active RFID system employing multiple access. The system comprising at least one tag Reader and a plurality of Tags each having a unique tag ID and deployed in a region in which at least some of the Tags are in radio communication with the tag Reader. A multi-dimensional addressing scheme of the MAC protocol enables division of the plurality of Tags into a number of groups for different stages of MAC protocol processing, based on different portions of the tag ID. The MAC has an inherent flexibility in the sense that it allows readers to communicate with different versions of tags and also 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.

## Claims

### Claim 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 in the plurality of Tags is associated with a unique tag ID, and
(c) a Media Access Control protocol according to which:
said tag Reader is configured to send and receive radio communications to and from at least some of said plurality of Tags,
said plurality of Tags are configured to send and receive radio communications to and from said tag Reader, and
said Media Access Control protocol is configured to control said radio communications between said tag Reader and said plurality of Tags, and said Media Access Control protocol includes a multi-dimensional addressing scheme, said multi-dimensional addressing scheme using a hash function to transform said tag ID into a pseudo random ID and enabling division of said plurality of Tags into one or more groups for different stages of Media Access Control protocol processing, based on different portions of said tag pseudo random ID.

### Claim 2

(canceled)

### Claim 3 (depends on 21)

The system of claim 21, wherein a portion of said tag pseudo random 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.

### Claim 4 (depends on 1)

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

### Claim 5 (depends on 1)

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.

### Claim 6 (depends on 1)

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.

### Claim 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 in the plurality of Tags is associated with a unique tag ID, and
(c) a Media Access Control protocol according to which:
said tag Reader is configured to send and receive radio communications to and from at least some of said plurality of Tags,
said plurality of Tags are configured to send and receive radio communications to and from said tag Reader and other Tags in said plurality of Tags, wherein the plurality of Tags are assigned a pseudo-random ID based on the unique tag ID and a hash function and the plurality of Tags are divided into one or more groups based at least on one or more parts of the pseudo-random ID, and
said Media Access Control protocol is configured to control said radio communications 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.

### Claim 8 (depends on 7)

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.

### Claim 9 (depends on 7)

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.

### Claim 10 (depends on 7)

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.

### Claim 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, and wherein at least some tags are in radio communication with other Tags in said plurality of Tags, and each Tag in the plurality of Tags is associated with a unique tag ID; and
(c) a Media Access Control protocol according to which:
said tag Reader is configured to send and receive radio communications to and from at least some of said plurality of Tags,
said plurality of Tags are configured to send and receive radio communications 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 the plurality of Tags are assigned a pseudo-random ID based on the unique to ID and a hash function and the plurality of Tags are divided into one or more groups based at least on one or more parts of the pseudo-random ID; and
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 a manner that is compatible with that tag Reader's capabilities.

### Claim 12 (depends on 11)

The system of claim 11, wherein said radio communications includes an indication of a 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 a first generation Tags is configured to forward said block without modification, and a second generation tag Reader and/or Tag is configured to decode and modify said block as needed.

### Claim 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 each Tag in the plurality of Tags is associated with a unique tag ID, and
(c) a Media Access Control protocol according to which:
said tag Reader is configured to send and receive radio communications to and from at least some of said plurality of Tags,
said plurality of Tags are configured to send and receive radio communications to and from said tag Reader, wherein the plurality of Tags are assigned a pseudo-random ID based on the unique tag ID and a hash function and the plurality of Tags are divided into one or more groups based at least on one or more parts of the pseudo-random ID, 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 an indication of a payload start point, and each generation of tag Readers and/or Tags is configured to 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 tag Readers to efficiently communicate with a mixture of tag generations and/or tag versions.

### Claim 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 each Tag in the plurality of Tags is associated with a unique tag ID; and
(c) a Media Access Control protocol according to which:
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, wherein the plurality of Tags are assigned a pseudo-random ID based on the unique tag ID and a hash function and the plurality of Tags are divided into one or more groups based at least on one or more parts of the pseudo-random ID,
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, wherein a first generation Tags is configured to forward said block without modification, and a second generation tag Reader and/or Tag is configured to decode and modify said block as needed.

### Claim 15 (depends on 14)

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 tag Readers to efficiently communicate with a mixture of tag generations and/or tag versions.