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WO2012102600A1 - Portable radio frequency identification reader for real time location systems - Google Patents

Portable radio frequency identification reader for real time location systems Download PDF

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Publication number
WO2012102600A1
WO2012102600A1 PCT/MY2011/000167 MY2011000167W WO2012102600A1 WO 2012102600 A1 WO2012102600 A1 WO 2012102600A1 MY 2011000167 W MY2011000167 W MY 2011000167W WO 2012102600 A1 WO2012102600 A1 WO 2012102600A1
Authority
WO
WIPO (PCT)
Prior art keywords
rfid
rfid reader
tag
end device
reader
Prior art date
Application number
PCT/MY2011/000167
Other languages
French (fr)
Inventor
Widad Ismail
Read Mohammed Taher ABDULLA
Original Assignee
Universiti Sains Malaysia
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Universiti Sains Malaysia filed Critical Universiti Sains Malaysia
Publication of WO2012102600A1 publication Critical patent/WO2012102600A1/en

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Classifications

    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S13/00—Systems using the reflection or reradiation of radio waves, e.g. radar systems; Analogous systems using reflection or reradiation of waves whose nature or wavelength is irrelevant or unspecified
    • G01S13/74—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems
    • G01S13/76—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems wherein pulse-type signals are transmitted
    • G01S13/765—Systems using reradiation of radio waves, e.g. secondary radar systems; Analogous systems wherein pulse-type signals are transmitted with exchange of information between interrogator and responder
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S5/00—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations
    • G01S5/02—Position-fixing by co-ordinating two or more direction or position line determinations; Position-fixing by co-ordinating two or more distance determinations using radio waves
    • G01S5/0295—Proximity-based methods, e.g. position inferred from reception of particular signals
    • G01S5/02955—Proximity-based methods, e.g. position inferred from reception of particular signals by computing a weighted average of the positions of the signal transmitters
    • G—PHYSICS
    • G06—COMPUTING OR CALCULATING; COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K7/00—Methods or arrangements for sensing record carriers, e.g. for reading patterns
    • G06K7/10—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation
    • G06K7/10009—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves
    • G06K7/10366—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves the interrogation device being adapted for miscellaneous applications
    • G06K7/10475—Methods or arrangements for sensing record carriers, e.g. for reading patterns by electromagnetic radiation, e.g. optical sensing; by corpuscular radiation sensing by radiation using wavelengths larger than 0.1 mm, e.g. radio-waves or microwaves the interrogation device being adapted for miscellaneous applications arrangements to facilitate interaction with further interrogation devices, e.g. such that at least two interrogation devices may function and cooperate in a network of such devices
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B5/00—Near-field transmission systems, e.g. inductive or capacitive transmission systems
    • H04B5/70—Near-field transmission systems, e.g. inductive or capacitive transmission systems specially adapted for specific purposes
    • H04B5/77—Near-field transmission systems, e.g. inductive or capacitive transmission systems specially adapted for specific purposes for interrogation
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W64/00—Locating users or terminals or network equipment for network management purposes, e.g. mobility management
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04W—WIRELESS COMMUNICATION NETWORKS
    • H04W88/00—Devices specially adapted for wireless communication networks, e.g. terminals, base stations or access point devices
    • H04W88/02—Terminal devices
    • H04W88/06—Terminal devices adapted for operation in multiple networks or having at least two operational modes, e.g. multi-mode terminals
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • 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
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Definitions

  • the present invention generally relates to an active Radio Frequency Identification (RFID) reader for an indoor location system. More particularly, the present invention relates to a portable RFID reader that has an integrated RFID reader portion and an end device portion to communicate with a plurality of RFID tags and a remote host respectively.
  • RFID Radio Frequency Identification
  • the tracking apparatus may be bulkier than the item that is being tracked, thereby making it difficult or impossible to use in the particular environment in which the object may be located.
  • the item or the tracking apparatus must contain a wireless communications system and a power supply, which further increases bulk, or be tethered through a physical connection. Moreover, it is expensive to modify an object in this way.
  • RFID tags are relatively small, relatively inexpensive, and passive RFID tags do not require a power source.
  • Each RFID tag has a unique identifier that can be read wirelessly by RFID tag readers.
  • RFID tag readers do not require a direct line of sight to the tags to be able to read them and typically have a range of few feet for the most popular and inexpensive passive tags.
  • typical RFID tag readers cannot pinpoint the exact location of the object. Rather, they simply report the presence and absence of a tag in their field of sensitivity.
  • the RFID tag reader would have to be transported around the area in which the item is thought to be, in order to find the item.
  • the area would be divided in sections, with each section having an RFID tag reader. The sections are sized such that any item within the area is always within range of one of the RFID tag readers.
  • RFID Radio Frequency Identification
  • PC Personal Computer
  • industrial controller e.g., a PLC-Programmable Logic Controller
  • Radio Frequency Identification RFID
  • tags When these tags are excited, they produce or reflect an electromagnetic wave at some frequency, which is modulated with an identifying code or other useful information.
  • the tag may either be active or passive. Active tags have a self contained power supply. Passive tags require external excitation when they are to be read within the detection volume of a reader.
  • the interrogator or reader contains a transmitting /receiving antenna for sending an exciting frequency signal to a passive tag.
  • the transmitting/receiving antenna is positioned at the reader's portal end for receiving a modulated signal (magnetic or electromagnetic) produced by the excited tag.
  • RFID systems are radio communication systems that communicate between a radio transceiver, called an interrogator and transponders or tags.
  • the interrogator communicates to the tags using modulated radio signals and the tags respond with the modulated radio signals.
  • the interrogator transmits a continuous-wave radio signal using modulated backscattering where the antenna is electrically switched, by the modulating signal, from being an absorber of RF radiation to being a reflector of RF radiation.
  • This modulated backscatter allows communication from the tag to the interrogator (called the uplink).
  • Conventional modulated backscattering systems identify an object passing into range of the interrogator and stores data onto the tag and then retrieve that data from the tag at a later time.
  • RFID reader so as to prolong the life of the power supply.
  • the value to a company in knowing the location of the reader can be used to improve manufacturing and distribution efficiency, which translates to a more effective competitive presence in the marketplace.
  • the physical location of the RFID reader is usually provided by the human operator, or readers are fixed at known locations such that RFID-tagged material that passes within range of the reader can be read and its location determined based on the location of the reader.
  • RFID readers Another problem plaguing RFID systems used for indoor tracking applications is the amount of attenuation experienced by the transmitted signals from the tag to the reader and vice versa.
  • the RFID reader can lose its communications when it sends a command to recognize multiple tags placed inside a building due to severe attenuation of the signal and vast amounts of tag information being handled. Consequently the RFID reader loses the ability to track and to coordinate the status of the tags that thus inadvertently leads to an increase in the reader power consumption due to the need of retransmission and repeated reception to and form the tags respectively.
  • Data sent to and fro from the RFID reader and the plurality of RFID tags are only useful if the data is relayed to a host that is pre-installed with proprietary software to integrate the collected data.
  • proprietary software to integrate the collected data.
  • a portable RFID reader for use in RFID systems that is adapted for indoor real time location system applications that comprises of: a first transceiver unit integrated with a first antenna; a second transceiver unit integrated with a second antenna; an electronic buffer circuitry; a display; a controller having a RFID reader controller portion and an end device controller portion; and a power supply.
  • the first transceiver unit of the portable RFID reader is integrated with the first antenna in combination with the RFID controller portion of the controller to form a RFID reader portion that serves to enable bidirectional communication with a plurality of RFID tags in the deployed environment.
  • the second transceiver unit of the portable RFID reader is integrated with the second antenna in combination with the end device controller portion of the controller, to form an end device unit that serves to enable bidirectional communication with a host via a plurality of transceivers that act together to form a self healing mesh network.
  • an algorithm that implements a method of receiving information by the end device portion of the portable RFID reader via the end device transceiver from a remote host through a self-healing network of transceivers in an exemplary deployment environment that includes toggling the end device between a sleep mode and an active mode to minimize power consumption of the portable RFID reader.
  • an algorithm that implements a method of polling RFID tags by the RFID reader portion of the portable RFID reader of the present invention that involves indentifying the RFID tags of interest to the RFID reader with respect to the instructions relayed from the host and utilizing a spatial mechanism to reduce tag information collection time and unnecessary collection rounds.
  • an algorithm that implements a method of enabling the fast recognition of a plurality of RFID tags in a network of distributed RFID tags by making use of the knowledge of RFID tag implementation for a given deployment application and environment. More particularly, the method involves identifying each individual tag by tag type or tag family as is provided in a RFID tag's identifier string portion of the tag's transmission frame.
  • Figure 1 is a diagram depicting an exemplary environment in which the portable reader of the present invention may be deployed in;
  • FIG. 2 is a block diagram illustrating the portable reader's basic architecture as well as the interrelationship between the hardware layer, software layer and the hardware components inclusive of the RFID radio and end device radio in a preferable embodiment of the present invention
  • Figure 3 is a block diagram illustrating the various components of the software layer and the hardware layer of the portable reader in a preferable embodiment of the present invention
  • Figure 4 is a flow-chart illustrating the method in which the end-device transceiver of the portable reader receives broadcasted information from a remote host in a preferable embodiment of the present invention
  • FIG. 5 is a flow-chart illustrating the method in which the RFID reader upon receipt of commands from a remote host via the end device transceiver proceeds to communicate with a plurality of RFID tags;
  • FIG. 6 is a flow chart illustrating the method in which the RFID reader ensures that all tags in a particular deployment environment have been read in a quick and efficient manner
  • Figure 7 is a flow-chart illustrating the method in which the end device transceiver of the preferable embodiment of the portable reader relays collected RFID tag information (RFID tag identifier strings packaged into a transmission frame) to a remote host.
  • FIG. 1 to 7 which, illustrate a preferred embodiment of the portable RFID reader 102 of the present invention will now be described in detail.
  • the portable reader of the present invention is deployed in an exemplary environment that comprises of a plurality of RFID tags 126, a plurality of RFID readers 136, a plurality of transceivers that are networked to form a self- healing communications network 132 and a host computer 134 deployed within a building infrastructure such as a manufacturing facility or warehousing facility.
  • the portable reader of the present invention broadly comprising of a first transceiver unit 110 integrated with a first antenna 112 and a second transceiver unit 118 integrated with a second antenna 120, a controller that includes a RFID controller portion 108 and an end device controller portion 116, a display unit 122, quad 3-state buffers and a power source 138.
  • the RFID reader portion 106 and the end device portion 114 are physically electrically interconnected.
  • the RFID reader portion 106 and the end device portion 114 are housed within a common housing 104 of the portable reader 102 of the present invention.
  • the portable reader 102 further includes a display unit 122 to provide a means of visual feedback to an operator of said portable reader 122, and a power source 138 that serves to power the hardware components of said portable reader 122.
  • the end device portion 114 of the portable reader 102 is configured to support bi- directional wireless data communications to and from a remote host 134 via a self healing network of transceivers 132.
  • the RFID reader portion 106 is configured to support bidirectional data communication to and from a plurality of RFID tags 126 that are deployed in the exemplary deployment environment as described herein.
  • the RFID reader portion 106 and the end device portion 114 communicate with the plurality of RFID tags 126 and the host 134 via a plurality of networked transceivers that form a self-healing communications network 132 respectively by utilizing a common data communications protocol. In an exemplary embodiment of the present invention, this is the IEEE 802.15.4 (Zig-Bee) data communications protocol.
  • FIG. 2 provides a block diagram that illustrates the hardware platform 230, the hardware layer 210 and the software interface layer 205 or software layer 205 for short, of the portable RFID reader 102 of the present invention.
  • the hardware layer 210 encompasses the hardware platform 230 that comprises a RFID reader portion 106 represented by the RFID radio block 215 in figure 2, the end device portion 114 represented by the end device radio block 225 in figure 2 as well as other associated hardware components that are lumped together in the hardware component block 220 of figure 2.
  • the software layer 205 includes hardware layer 210 dependent libraries that reside on the hardware level in an exemplary architecture of the portable RFID reader 102 and are thus used to define the functionality of the portable reader 102.
  • the software layer 205 provides many of the functions associated with the reading of the plurality of RFID tags 126, making calls to library functions, receiving commands from the host 134 through the wireless transceivers networked in a self-healing mesh network 132 and transmitting data to the host 134 by enabling wireless communication between the end-device portion 114 and the remote host 134.
  • the hardware layer 210 provides the physical interface between portable reader 102 of the present invention and the plurality of RFID tags 126 via the RFID reader portion 106 of the portable reader 102 and the physical interface between the portable reader 102 and the remote host 134 via the end device portion 114 of the portable reader 102.
  • the hardware layer 210 is shown to include the RFID reader portion's transceiver 110 represented by block 324, the end device portion's transceiver 118 represented by block 322, the controller module represented by block 326, a power source interface represented by block 328, a quad 3-state buffer block 330, a user interface block 316, a peripheral block 318 and a host interface block 320.
  • the power source interface block 328 provides an interface between the power source 138 and the various hardware components requiring a power supply that make up the portable reader 102 of the present invention.
  • the quad 3-state buffer block 330 serves to switch the portable RFID reader 102 to a RFID reader mode and an end device mode.
  • the portable RFID reader 102 of the present invention can be configured to operate in either the end device mode of operation or the RFID reader mode of operation. Alternatively the portable RFID reader 102 of the present invention can also be configured to be operated in both modes concurrently to thus enable the continuous reception of transmission frames from a plurality of RFID tags 126 in an exemplary environment.
  • the driver block 332 serves the purpose of enabling the portable reader 102 of the present invention to communicate with other peripheral devices.
  • the software layer 205 that resides in the controller module that comprises of a RFID reader controller portion 110 and an end device controller portion 116 includes a RFID reader protocol library 334 and an end device protocol library 336.
  • the RFID reader protocol library 334 dictates the establishment of a RFID tags 126 node identifier list within the memory of the controller and more particularly within the software layer 205.
  • the RFID reader protocol library 334 further defines initialization of the RFID reader portion 106 of the portable reader 102, information transmission approach utilized by the RFID reader portion 106 of the portable RFID reader 102 for received commands that are received via reception by the end device portion 114 of the portable RFID reader 102 from the remote host 134.
  • the RFID reader protocol library 334 implements functions that execute commands received via the end device portion 114 of the portable RFID reader 102 from the remote host 134, execute commands that make references to look up tables, execute interrupt service routines and subroutines as well as transmission of wake-up signals for the plurality of RFID tags 126 deployed in the exemplary deployment environment as described herein.
  • the end device protocol 336 provides an interface to the end device portion 114 to communicate with the remote host 134 via the self healing communications network 132.
  • the host 134 is a server that is adapted with software to enable communication with the portable reader 102 through the plurality of wirelessly networked wireless transceivers that form a self-healing communications network 132.
  • the host 134 is configured to enable the portable reader 102 of the present invention by means of transmission of a suitable command signal to the end device portion 114 of the portable RFID reader 102.
  • the portable RFID reader 102 of the present invention operating in the end device transceiver mode of operation is illustrated.
  • a method in which the end device portion 114 communicates with a remote host 134 to receive a command signal from the host 134 is depicted.
  • the controller portion of the end device transceiver 116 upon identifying that the end device portion 114 is yet to receive a broadcast from the host 134, and is yet to gain permission to access any one of the plurality of wireless transceivers networked in the self-healing network 132, will proceed to request permission from the host 134 to secure a communications channel to said host 134 by gaining access to any one of the transceivers in the self-healing network of transceivers 132.
  • the first step of said method includes the end device portion 114 switching to a sleep mode or low power consumption mode from an active mode or high power consumption mode in the event that said end device portion 114 of the portable reader 102 does not detect the reception of a broadcast frame consisting of either commands or data from the remote host 134 via the self-healing network of transceivers 132. This corresponds to step 405 of the flowchart of figure 4.
  • step 410 the end device transceiver unit 118 of the end device portion 114 switches to a receiver mode of operation.
  • step 410 the end device transceiver 118 will switch back to sleep mode but remain in the receiver mode of operation, if within a predetermined duration of time it does not detect reception of a transmission frame from the remote host 134 via any one of the transceivers of the self healing network of transceivers 132.
  • the end device portion 114 upon detection of a received transmission frame broadcast from the remote host 134, the end device portion 114 will exit the sleep mode or the low power consumption mode and consequently enter the active mode to process the received transmission frame from the remote host 134.
  • the received transmission frame could have been received via any one of the transceivers of the self-healing communications network 132. This corresponds to steps 415 and 420 of the flow chart of figure 4.
  • the end device transceiver 118 of the end device portion 114 of said portable RFID reader 102 of the present invention switches to transmit mode and proceeds to send a confirmation of the receipt of the transmitted frame to the remote host 134 via any one of the transceivers of the self-healing network of transceivers 132.
  • the end device controller portion 116 will parse the received transmission frame received from the remote host 134 and determine if the frame contains data or commands. If the received transmission frame contains a command, the command will be executed by the end device controller portion 116.
  • the end device controller portion 116 will proceed to correlate the broadcast command with a RFID tag 126 node identifier list stored in the controller's internal database. If in another instance the received transmission frame contains data, the end device controller portion 114 will store the data into an internal data base for later retrieval and use by the RFID reader controller portion 106 if the data is intended for the RFID reader portion 106 of the portable RFID reader 102 or proceed to process the received data otherwise.
  • FIG 5 a method of the RFID reader portion 106 of the portable reader 102 communicating with a plurality of RFID tags 126 in an exemplary environment, is illustrated by the various steps/blocks of a flowchart.
  • the flowchart of figure 5 is a continuation of the flowchart of figure 4.
  • the portable RFID reader 102 of the present invention is operating in the RFID reader mode of operation.
  • the flow chart of figure 5 more particularly seeks to describe the method in which the RFID reader portion 106 of the portable RFID reader 102 of the present invention carries on with the process of transmitting broadcast command signals to a plurality of RFID tags 126 in an exemplary deployment environment in response to the end device portion 114 of the portable RFID reader 102 receiving said broadcast command from the remote host 134.
  • step 501 of the flowchart of figure 5 the end device portion 114 upon receipt of a broadcast command signal from the remote host 134, will revert to the sleep mode or low power consumption mode.
  • step 502 the software interface layer 205 will look into the RFID reader protocol library 334 to retrieve a command to be transmitted to the plurality of RFID tags 126 in the exemplary deployment environment when the portable RFID reader 102 is switched to operate in the RFID reader mode of operation.
  • the RFID transceiver 110 of said RFID reader portion 106 of the portable RFID reader 102 of the present invention is switched to the transmitter mode of operation to send the required command signals that have been retrieved from the RFID protocol library 334 of the software layer 205 to the plurality of RFID tags 126 deployed in an exemplary deployment environment. This corresponds to step 503 of the flowchart of figure 5.
  • the RFID transceiver 110 of the RFID reader portion 106 will switch to the receiver mode of operation to thus enable the reception of a signal in response to the prior transmission.
  • the RFID reader portion 106 in step 503 will transmit a "node discover" command, that once received by the plurality of RFID tags 126 in an exemplary deployment environment will prompt a response from the plurality of RFID tags 126 such that the tags 126 will respond by transmitting their respective tags module address, serial numbers and node identifier to said RFID reader portion 106 of the portable RFID reader 102 of the present invention.
  • the sequence of events described in the preceding few lines of this passage occur in step 504.
  • each RFID tag 126 of the plurality of RFID tags 126 will wait for a random duration of time, before responding to said "node discover" command.
  • the RFID reader portion 106 will, upon receipt of the respective RFID tag 126 addresses, serial numbers and node identifiers from each of the respective RFID tags 126 of the plurality of RFID tags 126, retrieve stored parameters from the RFID protocol library 334.
  • the software interface layer 205 will configure the RFID reader portion 106 of the portable RFID reader 102 of the present invention to provide optimal transmission and reception performance with relation to pre-specified instructions relayed from the remote host 134 received by the end device portion 114 of the portable RFID reader 102 of the present invention by running a spatial mechanism to reduce RFID tag 126 collection time by eliminating unnecessarily consumed collection rounds.
  • the spatial mechanism is based on information received by the plurality of RFID tags 126, more particularly the node identifier strings in the preamble portion of the received transmission frames transmitted by the plurality of RFID tags 126 to the RFID reader portion 106.
  • the node identifier strings enable the RFID reader controller portion 108 to determine how best to handle the remaining data portion of the transmission frame received from the plurality of RFID tags 126 based on the tag 126 type and configuration of the network of RFID tags 126.
  • figures 4 and figures 5 succinctly describe the overall method of communication of the portable RFID reader 102 of the present invention with a plurality of RFID tags 126 and a remote host 134 in an exemplary deployment environment.
  • a RFID tag 126 node identifier list of the network of RFID tags 126 in an exemplary deployment environment is established in the RFID protocol library 334 of the software layer 205.
  • the received transmission frames coming from the respective RFID tags 126 are read only in the identifier portion of the transmission frame that correspond to the sync bit of the RFID tag 126 transmission frame.
  • the first step of the method involves the RFID transceiver 110 of the RFID reader portion 106 to be configured in the receive mode of operation, in anticipation of receiving transmission frames from the plurality of RFID tags 126.
  • the received transmission frames are parsed out by the software interface layer 205.
  • a "RFID tag 126 counter" that resides within the software interface layer 205 which in turn resides in an area of memory belonging to the controller module, is initialized to a zero count in preparation to identifying the configuration of deployed RFID tags 126 in an exemplary deployment environment.
  • the subsequent step i.e.
  • step 615 upon receipt via the RFID reader transceiver unit 110 of a transmission frame from a RFID tag 126 of the plurality of RFID tags 126 deployed in an exemplary environment, the RFID reader protocol 334 through the execution of source code executed by the RFID controller portion 108, will compare the node identifier string encoded in the sync bits of the RFID tag 126 transmission frame pertaining to a particular RFID tag 126.
  • the received tag identifier string does not match the RFID tag 126 identifier string in the RFID tag 126 identifier node list stored in an internal database as dictated by the RFID reader protocol 334, the received transmission frame from that particular RFID tag 126 will be discarded. This corresponds to step 625 depicted in the flowchart of figure 6.
  • the further reading and processing of the subsequent string of characters within the received transmission frame as dictated by the RFID reader protocol 334 is executed.
  • This step is represented by block 640 in the flowchart of figure 6.
  • the "RFID tag 126 counter" is incremented. This corresponds to step 645 of the flowchart of figure 6.
  • the RFID tag 126 transmission frames that have been read are repackaged in another transmission frame format that as dictated by the end device protocol and contain all the RFID tag 126 node identifier tag strings that have been successfully read, for retransmission via the end device portion 114 of the portable RFID reader 102 to the remote host 134.
  • the RFID reader protocol 334 dictates the RFID reader portion 106 to continue with the reading of the next transmission frame from another RFID tag 126 of the plurality of RFID tags 126 deployed in an exemplary deployment environment. This corresponds to step 630 as is depicted in the flowchart of figure 6.
  • the RFID reader protocol 334 dictates the RFID reader portion 106 to continue with the reading of the next transmission frame from another RFID tag 126 of the plurality of RFID tags 126 deployed in an exemplary deployment environment. This corresponds to step 630 as is depicted in the flowchart of figure 6.
  • the steps inclusive of steps 615, 620, 640, 645, 650, 625, 630 and 635 will repeated until all transmission frames from all the RFID tags 126 have been read.
  • the method terminates by proceeding to the transmission of a packet frame containing all the RFID tag 126 identifier strings of all the successfully read RFID tag transmission frames that have been read, to the remote host 134 via the end device portion 114 of the portable RFID reader 102 as is illustrated in figure 7.
  • a reconfigured transmission frame containing all the RFID tag 126 identifier strings of the plurality of RFID tag 126 transmission frames of the plurality of RFID tags 126 in an exemplary environment is transmitted by the end device portion 114 of the portable RFID reader 102 of the present invention to the remote host 134.
  • step 705 entails the retrieval of data by the software interface layer 205 from the end device protocol library 336 and consequently enabling the transmitting of a transmission frame containing all the RFID tag 126 identifier strings of the plurality of RFID tags 126 in an exemplary deployment environment from the end device portion 114 to the remote host 134 via the self healing network of transceivers 132.
  • the end device protocol library 336 through the end device controller portion 116 of the controller module switches the end device transceiver unit 118 to the transmit mode of operation thus causing the end device transceiver 118 to exit the sleep mode of operation.
  • the end device transceiver unit 118 once in the transmitter mode of operation, transmits/broadcasts the thus packaged transmission frame packet containing the node identifier strings of all the RFID tags 126 of the plurality of RFID tags 126 in an exemplary deployment environment to the remote host 134 via the self healing network of transceiver 132.
  • the end device transceiver unit 118 is switched back to the receiver mode of operation in anticipation of receiving an acknowledgement from the remote host 134 via the self healing network of transceivers 132.
  • step 720 entails the determination of whether the transmission frame containing all the identifier strings of the successfully identified RFID tags 126 of an exemplary deployment environment of RFID tags 126 to the remote host 134 is successful.
  • the remote host 134 Upon receipt of the transmission frame of all the RFID node identifier strings of all the successfully read RFID tags 126 of the plurality of RFID tags 126, the remote host 134 will transmit a network level acknowledgement to the plurality of transceivers of the self healing network of transceivers 132. The transceivers of the self healing network of transceivers 132 will in turn transmit the network level acknowledgement to the RFID portable reader 102 of the present invention. The receipt of this network level acknowledgement by the end device transceiver 118 of the portable RFID reader 102, confirms that the transmission frame containing all the RFID tag 126 node identifier strings of the plurality of RFID tags 126 has been received by the remote host 134.
  • the remote host 134 would not transmit a network level acknowledgement to the plurality of transceivers of the self healing communications network of transceivers 132 and consequently the portable RFID reader 102 (the end device portion 114 of the RFID portable reader 102) will not receive said network level acknowledgement. If it has been determined in the preceding step (step 720) that the transmission frame containing all the RFID tag 126 identifier strings of the plurality of RFID tags 126 has not been successfully transmitted to the remote host 134, the steps 715 and 720 are repeated until a successful transmission occurs.

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  • Radar Systems Or Details Thereof (AREA)

Abstract

The present invention discloses a portable RFID reader device (102) that comprises of a first transceiver (110) integrated with a first antenna (112) and a second transceiver (118) integrated with a second antenna (120) housed within a common housing (104) and in communication with one another via a physical electrical interconnection. The first transceiver (110) being an RFID transceiver in combination with a portion of a controller (108) designated for RFID reader functionality perform the functions of a RFID reader (106). The second transceiver (118) being an end device transceiver is in combination with a portion of a controller (116) designated for performing computations related to the information received by the end device transceiver (118) from a host (134) from an end device (114).

Description

PORTABLE RADIO FREQUENCY IDENTIFICATION READER FOR REAL TIME
LOCATION SYSTEMS
The present invention generally relates to an active Radio Frequency Identification (RFID) reader for an indoor location system. More particularly, the present invention relates to a portable RFID reader that has an integrated RFID reader portion and an end device portion to communicate with a plurality of RFID tags and a remote host respectively. BACKGROUND TO THE INVENTION
There are many contexts in which it is useful or even necessary to know the position of an item in the physical world. For example, logistics systems need to track the movement of goods through warehouses, and assembly robots need to determine the position of cars as they move down the assembly line. Applications of such knowledge are nearly countless, because knowing the position of objects is a fundamental requirement for interacting with the physical world.
One technique for determining the position of a physical object is to have the physical object report its position through a wired or wireless connection. While this technique is useful for some applications, it does not lend itself to all such applications. The tracking apparatus may be bulkier than the item that is being tracked, thereby making it difficult or impossible to use in the particular environment in which the object may be located. The item or the tracking apparatus must contain a wireless communications system and a power supply, which further increases bulk, or be tethered through a physical connection. Moreover, it is expensive to modify an object in this way.
A relatively inexpensive technique for determining the position of an object in the physical world is to attach a Radio Frequency Identification (RFID) tag to the object. RFID tags are relatively small, relatively inexpensive, and passive RFID tags do not require a power source. Each RFID tag has a unique identifier that can be read wirelessly by RFID tag readers. RFID tag readers do not require a direct line of sight to the tags to be able to read them and typically have a range of few feet for the most popular and inexpensive passive tags. However, typical RFID tag readers cannot pinpoint the exact location of the object. Rather, they simply report the presence and absence of a tag in their field of sensitivity. Conventionally, if an item having an RFID tag is to be located, the RFID tag reader would have to be transported around the area in which the item is thought to be, in order to find the item. Alternatively, the area would be divided in sections, with each section having an RFID tag reader. The sections are sized such that any item within the area is always within range of one of the RFID tag readers.
In today's highly sophisticated, complex and intelligent industrial automation systems, RFID (Radio Frequency Identification) technology is becoming an increasingly important presence for logistics concerns, material handling and inventory management. Simply knowing that an object exists in a large warehouse is no longer sufficient. When implementing an RFID solution in a distribution center or factory, it is customary to utilize three distinct platforms: an RFID reader/antenna (e.g., a fixed implementation), RFID "middle-ware" software running on standard PC (Personal Computer), and an industrial controller (e.g., a PLC-Programmable Logic Controller). A traditional communications approach is to have the RFID reader connect to the controller via a network using, for example RS-232 serial communications, Ethernet, or any of the field busses such as DeviceNet, ControlNet, etc.
It can thus be concluded that the use of Radio Frequency Identification (RFID) transponders or tags to identify an object or objects is well known in the art of RFID systems. Typically, when these tags are excited, they produce or reflect an electromagnetic wave at some frequency, which is modulated with an identifying code or other useful information. The tag may either be active or passive. Active tags have a self contained power supply. Passive tags require external excitation when they are to be read within the detection volume of a reader. In passive tag systems, the interrogator or reader contains a transmitting /receiving antenna for sending an exciting frequency signal to a passive tag. The transmitting/receiving antenna is positioned at the reader's portal end for receiving a modulated signal (magnetic or electromagnetic) produced by the excited tag. This modulated signal identifies the tag and consequently the object attached thereto. RFID systems are radio communication systems that communicate between a radio transceiver, called an interrogator and transponders or tags. In RFID systems, the interrogator communicates to the tags using modulated radio signals and the tags respond with the modulated radio signals. When transmitting a message to a tag (called the downlink,) the interrogator transmits a continuous-wave radio signal using modulated backscattering where the antenna is electrically switched, by the modulating signal, from being an absorber of RF radiation to being a reflector of RF radiation. This modulated backscatter allows communication from the tag to the interrogator (called the uplink). Conventional modulated backscattering systems identify an object passing into range of the interrogator and stores data onto the tag and then retrieve that data from the tag at a later time.
Most interrogators are operated using a battery powered system. This modulated backscattering system consumes a lot of power. As the number of tags to be identified increase, the consumption of power increases exponentially. Continual changing of the battery interrupts workflow and when the battery is low on power the interrogator may provide incorrect reads. Therefore it is desirous to operate the RFID reader so as to prolong the life of the power supply. The value to a company in knowing the location of the reader can be used to improve manufacturing and distribution efficiency, which translates to a more effective competitive presence in the marketplace. In conventional RFID implementations, the physical location of the RFID reader is usually provided by the human operator, or readers are fixed at known locations such that RFID-tagged material that passes within range of the reader can be read and its location determined based on the location of the reader. However given the rapid technological advances in portable handheld communications devices (e.g., cell phones, and PDAs), customers are demanding such portability in RFID readers. Another problem plaguing RFID systems used for indoor tracking applications is the amount of attenuation experienced by the transmitted signals from the tag to the reader and vice versa. Generally the RFID reader can lose its communications when it sends a command to recognize multiple tags placed inside a building due to severe attenuation of the signal and vast amounts of tag information being handled. Consequently the RFID reader loses the ability to track and to coordinate the status of the tags that thus inadvertently leads to an increase in the reader power consumption due to the need of retransmission and repeated reception to and form the tags respectively.
Data sent to and fro from the RFID reader and the plurality of RFID tags are only useful if the data is relayed to a host that is pre-installed with proprietary software to integrate the collected data. When the number of RFID readers is large, in a particular deployment of a RFID system, there is a possibility for the RFID reader to lose communication with the host.
In view of the above, it is evident that there is a need to overcome the problems plaguing RFID readers of the prior art. As such it is advantageous to provide an RFID reader that overcomes at least one of the above mentioned problems.
SUMMARY OF THE INVENTION
The following presents a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is not intended to identify key/critical elements of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as prelude to the more detailed description that is presented later.
In one aspect of the present invention there is provided a portable RFID reader for use in RFID systems that is adapted for indoor real time location system applications that comprises of: a first transceiver unit integrated with a first antenna; a second transceiver unit integrated with a second antenna; an electronic buffer circuitry; a display; a controller having a RFID reader controller portion and an end device controller portion; and a power supply.
The first transceiver unit of the portable RFID reader is integrated with the first antenna in combination with the RFID controller portion of the controller to form a RFID reader portion that serves to enable bidirectional communication with a plurality of RFID tags in the deployed environment. Similarly, the second transceiver unit of the portable RFID reader is integrated with the second antenna in combination with the end device controller portion of the controller, to form an end device unit that serves to enable bidirectional communication with a host via a plurality of transceivers that act together to form a self healing mesh network.
In a second aspect of the invention there is provided an algorithm that implements a method of receiving information by the end device portion of the portable RFID reader via the end device transceiver from a remote host through a self-healing network of transceivers in an exemplary deployment environment that includes toggling the end device between a sleep mode and an active mode to minimize power consumption of the portable RFID reader.
In another aspect of the present invention, there is provided an algorithm that implements a method of polling RFID tags by the RFID reader portion of the portable RFID reader of the present invention that involves indentifying the RFID tags of interest to the RFID reader with respect to the instructions relayed from the host and utilizing a spatial mechanism to reduce tag information collection time and unnecessary collection rounds. In yet another aspect of the present invention, there is provided an algorithm that implements a method of enabling the fast recognition of a plurality of RFID tags in a network of distributed RFID tags by making use of the knowledge of RFID tag implementation for a given deployment application and environment. More particularly, the method involves identifying each individual tag by tag type or tag family as is provided in a RFID tag's identifier string portion of the tag's transmission frame.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a diagram depicting an exemplary environment in which the portable reader of the present invention may be deployed in;
Figure 2 is a block diagram illustrating the portable reader's basic architecture as well as the interrelationship between the hardware layer, software layer and the hardware components inclusive of the RFID radio and end device radio in a preferable embodiment of the present invention;
Figure 3 is a block diagram illustrating the various components of the software layer and the hardware layer of the portable reader in a preferable embodiment of the present invention;
Figure 4 is a flow-chart illustrating the method in which the end-device transceiver of the portable reader receives broadcasted information from a remote host in a preferable embodiment of the present invention;
Figure 5 is a flow-chart illustrating the method in which the RFID reader upon receipt of commands from a remote host via the end device transceiver proceeds to communicate with a plurality of RFID tags;
Figure 6 is a flow chart illustrating the method in which the RFID reader ensures that all tags in a particular deployment environment have been read in a quick and efficient manner; and Figure 7 is a flow-chart illustrating the method in which the end device transceiver of the preferable embodiment of the portable reader relays collected RFID tag information (RFID tag identifier strings packaged into a transmission frame) to a remote host. DETAILED DESCRIPTION OF THE INVENTION
The detailed description set forth below in connection with the appended drawings is intended as a description of exemplary embodiments and is not intended to represent the only forms in which these embodiments may be constructed and/or utilized. The description sets forth the functions and the sequence for constructing the exemplary embodiments. However, it is to be understood that the same or equivalent functions and sequences may be accomplished by different embodiments that are also intended to be encompassed within the scope of this disclosure.
Figures 1 to 7 which, illustrate a preferred embodiment of the portable RFID reader 102 of the present invention will now be described in detail.
With reference to figure 1 , the portable reader of the present invention is deployed in an exemplary environment that comprises of a plurality of RFID tags 126, a plurality of RFID readers 136, a plurality of transceivers that are networked to form a self- healing communications network 132 and a host computer 134 deployed within a building infrastructure such as a manufacturing facility or warehousing facility. The portable reader of the present invention broadly comprising of a first transceiver unit 110 integrated with a first antenna 112 and a second transceiver unit 118 integrated with a second antenna 120, a controller that includes a RFID controller portion 108 and an end device controller portion 116, a display unit 122, quad 3-state buffers and a power source 138. The first transceiver unit 110 integrated with the first antenna 112 in combination with a portion of the controller that forms the RFID controller portion 108 act together in a cohesive manner to thus form the RFID reader portion 106 of the portable reader 102 of the present invention. The second transceiver unit 118 integrated with the second antenna 120 in combination with a portion of the controller that forms the end device controller portion 116 act together in a cohesive manner to thus from an end device portion 114 of the portable reader 102 of the present invention. The RFID reader portion 106 and the end device portion 114 are physically electrically interconnected. The RFID reader portion 106 and the end device portion 114 are housed within a common housing 104 of the portable reader 102 of the present invention. The portable reader 102 further includes a display unit 122 to provide a means of visual feedback to an operator of said portable reader 122, and a power source 138 that serves to power the hardware components of said portable reader 122.
The end device portion 114 of the portable reader 102 is configured to support bi- directional wireless data communications to and from a remote host 134 via a self healing network of transceivers 132. Similarly the RFID reader portion 106 is configured to support bidirectional data communication to and from a plurality of RFID tags 126 that are deployed in the exemplary deployment environment as described herein. In the portable RFID reader 102 of the present invention, the RFID reader portion 106 and the end device portion 114 communicate with the plurality of RFID tags 126 and the host 134 via a plurality of networked transceivers that form a self-healing communications network 132 respectively by utilizing a common data communications protocol. In an exemplary embodiment of the present invention, this is the IEEE 802.15.4 (Zig-Bee) data communications protocol.
In the exemplary environment in which the portable reader 102 of the present invention is deployed in, there is also a plurality of other portable RFID readers 136 that are deployed within the exemplary environment. The general in depth operation of the portable RFID reader 102 of the present invention will not described in the description herein as the in depth operations of RFID readers are well known and covered in the prior art.
Figure 2 provides a block diagram that illustrates the hardware platform 230, the hardware layer 210 and the software interface layer 205 or software layer 205 for short, of the portable RFID reader 102 of the present invention. The hardware layer 210 encompasses the hardware platform 230 that comprises a RFID reader portion 106 represented by the RFID radio block 215 in figure 2, the end device portion 114 represented by the end device radio block 225 in figure 2 as well as other associated hardware components that are lumped together in the hardware component block 220 of figure 2.
The software layer 205 includes hardware layer 210 dependent libraries that reside on the hardware level in an exemplary architecture of the portable RFID reader 102 and are thus used to define the functionality of the portable reader 102. The software layer 205 provides many of the functions associated with the reading of the plurality of RFID tags 126, making calls to library functions, receiving commands from the host 134 through the wireless transceivers networked in a self-healing mesh network 132 and transmitting data to the host 134 by enabling wireless communication between the end-device portion 114 and the remote host 134. The hardware layer 210 provides the physical interface between portable reader 102 of the present invention and the plurality of RFID tags 126 via the RFID reader portion 106 of the portable reader 102 and the physical interface between the portable reader 102 and the remote host 134 via the end device portion 114 of the portable reader 102.
With reference to figure 3, the hardware layer 210 is shown to include the RFID reader portion's transceiver 110 represented by block 324, the end device portion's transceiver 118 represented by block 322, the controller module represented by block 326, a power source interface represented by block 328, a quad 3-state buffer block 330, a user interface block 316, a peripheral block 318 and a host interface block 320.
The power source interface block 328 provides an interface between the power source 138 and the various hardware components requiring a power supply that make up the portable reader 102 of the present invention. The quad 3-state buffer block 330 serves to switch the portable RFID reader 102 to a RFID reader mode and an end device mode. The portable RFID reader 102 of the present invention can be configured to operate in either the end device mode of operation or the RFID reader mode of operation. Alternatively the portable RFID reader 102 of the present invention can also be configured to be operated in both modes concurrently to thus enable the continuous reception of transmission frames from a plurality of RFID tags 126 in an exemplary environment.
The driver block 332, serves the purpose of enabling the portable reader 102 of the present invention to communicate with other peripheral devices. The software layer 205 that resides in the controller module that comprises of a RFID reader controller portion 110 and an end device controller portion 116 includes a RFID reader protocol library 334 and an end device protocol library 336. The RFID reader protocol library 334 dictates the establishment of a RFID tags 126 node identifier list within the memory of the controller and more particularly within the software layer 205.
The RFID reader protocol library 334 further defines initialization of the RFID reader portion 106 of the portable reader 102, information transmission approach utilized by the RFID reader portion 106 of the portable RFID reader 102 for received commands that are received via reception by the end device portion 114 of the portable RFID reader 102 from the remote host 134.
The RFID reader protocol library 334 implements functions that execute commands received via the end device portion 114 of the portable RFID reader 102 from the remote host 134, execute commands that make references to look up tables, execute interrupt service routines and subroutines as well as transmission of wake-up signals for the plurality of RFID tags 126 deployed in the exemplary deployment environment as described herein. The end device protocol 336 provides an interface to the end device portion 114 to communicate with the remote host 134 via the self healing communications network 132. It also defines the handling of data received by the RFID reader portion 106 of the portable RFID reader 102 and may make calls to functions in the RFID reader protocol library 334 to hence transfer the collected data received by the RFID reader portion 106 to a remote host 134 via wireless transmission from the end device portion 114 of the portable RFID reader 102.
In the exemplary deployment environment as described herein, the host 134 is a server that is adapted with software to enable communication with the portable reader 102 through the plurality of wirelessly networked wireless transceivers that form a self-healing communications network 132. The host 134 is configured to enable the portable reader 102 of the present invention by means of transmission of a suitable command signal to the end device portion 114 of the portable RFID reader 102.
With reference to figure 4, the portable RFID reader 102 of the present invention operating in the end device transceiver mode of operation is illustrated. With reference to figure 4, a method in which the end device portion 114 communicates with a remote host 134 to receive a command signal from the host 134 is depicted. Initially the controller portion of the end device transceiver 116, upon identifying that the end device portion 114 is yet to receive a broadcast from the host 134, and is yet to gain permission to access any one of the plurality of wireless transceivers networked in the self-healing network 132, will proceed to request permission from the host 134 to secure a communications channel to said host 134 by gaining access to any one of the transceivers in the self-healing network of transceivers 132. The first step of said method includes the end device portion 114 switching to a sleep mode or low power consumption mode from an active mode or high power consumption mode in the event that said end device portion 114 of the portable reader 102 does not detect the reception of a broadcast frame consisting of either commands or data from the remote host 134 via the self-healing network of transceivers 132. This corresponds to step 405 of the flowchart of figure 4. In the subsequent step, step 410, the end device transceiver unit 118 of the end device portion 114 switches to a receiver mode of operation. In this step, i.e., step 410, the end device transceiver 118 will switch back to sleep mode but remain in the receiver mode of operation, if within a predetermined duration of time it does not detect reception of a transmission frame from the remote host 134 via any one of the transceivers of the self healing network of transceivers 132.
On the other hand, upon detection of a received transmission frame broadcast from the remote host 134, the end device portion 114 will exit the sleep mode or the low power consumption mode and consequently enter the active mode to process the received transmission frame from the remote host 134. The received transmission frame could have been received via any one of the transceivers of the self-healing communications network 132. This corresponds to steps 415 and 420 of the flow chart of figure 4. Upon receipt of the transmission frame, from the remote host 134, the end device transceiver 118 of the end device portion 114 of said portable RFID reader 102 of the present invention switches to transmit mode and proceeds to send a confirmation of the receipt of the transmitted frame to the remote host 134 via any one of the transceivers of the self-healing network of transceivers 132. This corresponds to step 425 of the flowchart of figure 4. In the subsequent step, i.e. step 430, the end device controller portion 116 will parse the received transmission frame received from the remote host 134 and determine if the frame contains data or commands. If the received transmission frame contains a command, the command will be executed by the end device controller portion 116. If on the other hand the transmission frame has been determined to contain a broadcast command issued by the remote host 134, the end device controller portion 116 will proceed to correlate the broadcast command with a RFID tag 126 node identifier list stored in the controller's internal database. If in another instance the received transmission frame contains data, the end device controller portion 114 will store the data into an internal data base for later retrieval and use by the RFID reader controller portion 106 if the data is intended for the RFID reader portion 106 of the portable RFID reader 102 or proceed to process the received data otherwise.
With reference to figure 5, a method of the RFID reader portion 106 of the portable reader 102 communicating with a plurality of RFID tags 126 in an exemplary environment, is illustrated by the various steps/blocks of a flowchart. The flowchart of figure 5 is a continuation of the flowchart of figure 4. In the flow chart of figure 5, the portable RFID reader 102 of the present invention is operating in the RFID reader mode of operation.
The flow chart of figure 5 more particularly seeks to describe the method in which the RFID reader portion 106 of the portable RFID reader 102 of the present invention carries on with the process of transmitting broadcast command signals to a plurality of RFID tags 126 in an exemplary deployment environment in response to the end device portion 114 of the portable RFID reader 102 receiving said broadcast command from the remote host 134.
In the step 501 of the flowchart of figure 5, the end device portion 114 upon receipt of a broadcast command signal from the remote host 134, will revert to the sleep mode or low power consumption mode. In the subsequent step, step 502 the software interface layer 205 will look into the RFID reader protocol library 334 to retrieve a command to be transmitted to the plurality of RFID tags 126 in the exemplary deployment environment when the portable RFID reader 102 is switched to operate in the RFID reader mode of operation. Next, the RFID transceiver 110 of said RFID reader portion 106 of the portable RFID reader 102 of the present invention is switched to the transmitter mode of operation to send the required command signals that have been retrieved from the RFID protocol library 334 of the software layer 205 to the plurality of RFID tags 126 deployed in an exemplary deployment environment. This corresponds to step 503 of the flowchart of figure 5.
In the subsequent step, i.e. step 504, just after transmitting to the plurality of RFID tags 126, the RFID transceiver 110 of the RFID reader portion 106 will switch to the receiver mode of operation to thus enable the reception of a signal in response to the prior transmission. Generally prior to reception of signals from the plurality of RFID tags 126, the RFID reader portion 106 in step 503, will transmit a "node discover" command, that once received by the plurality of RFID tags 126 in an exemplary deployment environment will prompt a response from the plurality of RFID tags 126 such that the tags 126 will respond by transmitting their respective tags module address, serial numbers and node identifier to said RFID reader portion 106 of the portable RFID reader 102 of the present invention. The sequence of events described in the preceding few lines of this passage, occur in step 504.
In an exemplary deployment environment, each RFID tag 126 of the plurality of RFID tags 126 will wait for a random duration of time, before responding to said "node discover" command. In the following step, i.e. step, 505, the RFID reader portion 106 will, upon receipt of the respective RFID tag 126 addresses, serial numbers and node identifiers from each of the respective RFID tags 126 of the plurality of RFID tags 126, retrieve stored parameters from the RFID protocol library 334. Next at step 506, the software interface layer 205 will configure the RFID reader portion 106 of the portable RFID reader 102 of the present invention to provide optimal transmission and reception performance with relation to pre-specified instructions relayed from the remote host 134 received by the end device portion 114 of the portable RFID reader 102 of the present invention by running a spatial mechanism to reduce RFID tag 126 collection time by eliminating unnecessarily consumed collection rounds.
The spatial mechanism is based on information received by the plurality of RFID tags 126, more particularly the node identifier strings in the preamble portion of the received transmission frames transmitted by the plurality of RFID tags 126 to the RFID reader portion 106. The node identifier strings enable the RFID reader controller portion 108 to determine how best to handle the remaining data portion of the transmission frame received from the plurality of RFID tags 126 based on the tag 126 type and configuration of the network of RFID tags 126.
In combination, figures 4 and figures 5 succinctly describe the overall method of communication of the portable RFID reader 102 of the present invention with a plurality of RFID tags 126 and a remote host 134 in an exemplary deployment environment.
With reference to figure 6, disclosed, is a method of optimizing the fast recognition of multiple RFID tags 126 that have been p re-configured to form a network of RFID tags 126 in an exemplary deployment environment and consequently minimizing power consumption of the portable RFID reader 102 of the present invention by utilizing the knowledge of RFID tag 126 deployment in an exemplary environment. More particularly the method involves identifying each individual RFID tag 126 by tag type or tag family as is provided by information encoded in the identifier string portion of the transmission frame of each individual RFID tag 126 in a network of RFID tags 126 deployed in an exemplary deployment environment.
In the method disclosed herein, a RFID tag 126 node identifier list of the network of RFID tags 126 in an exemplary deployment environment is established in the RFID protocol library 334 of the software layer 205. The received transmission frames coming from the respective RFID tags 126 are read only in the identifier portion of the transmission frame that correspond to the sync bit of the RFID tag 126 transmission frame.
The first step of the method, i.e. step 605 involves the RFID transceiver 110 of the RFID reader portion 106 to be configured in the receive mode of operation, in anticipation of receiving transmission frames from the plurality of RFID tags 126. Upon receipt of the transmission frames from each of the RFID tags 126 of the plurality of RFID tags 126 in the exemplary deployment environment, the received transmission frames are parsed out by the software interface layer 205. Next at step 610, a "RFID tag 126 counter" that resides within the software interface layer 205 which in turn resides in an area of memory belonging to the controller module, is initialized to a zero count in preparation to identifying the configuration of deployed RFID tags 126 in an exemplary deployment environment. In the subsequent step, i.e. step 615, upon receipt via the RFID reader transceiver unit 110 of a transmission frame from a RFID tag 126 of the plurality of RFID tags 126 deployed in an exemplary environment, the RFID reader protocol 334 through the execution of source code executed by the RFID controller portion 108, will compare the node identifier string encoded in the sync bits of the RFID tag 126 transmission frame pertaining to a particular RFID tag 126.
Based on the comparison made, if the received tag identifier string does not match the RFID tag 126 identifier string in the RFID tag 126 identifier node list stored in an internal database as dictated by the RFID reader protocol 334, the received transmission frame from that particular RFID tag 126 will be discarded. This corresponds to step 625 depicted in the flowchart of figure 6.
If on the other hand, the received RFID tag 126 identifier string does indeed match the RFID tag 126 identifier string in the RFID tag 126 identifier node list stored in the internal database, the further reading and processing of the subsequent string of characters within the received transmission frame as dictated by the RFID reader protocol 334 is executed. This step is represented by block 640 in the flowchart of figure 6. Subsequently upon completion of reading the RFID tag 126 transmission frame of a particular RFID tag 126 that contains an node identifier string that matches the an entry in the list of node identifier strings stored in an internal database of the portable RFID reader 102 of the present invention, the "RFID tag 126 counter" is incremented. This corresponds to step 645 of the flowchart of figure 6. Following step 645, the RFID tag 126 transmission frames that have been read are repackaged in another transmission frame format that as dictated by the end device protocol and contain all the RFID tag 126 node identifier tag strings that have been successfully read, for retransmission via the end device portion 114 of the portable RFID reader 102 to the remote host 134. This corresponds to step 650 of the flowchart of figure 6.
Upon completion of discarding the RFID tag 126 transmission frame with the non- matching node identifier string, the RFID reader protocol 334 dictates the RFID reader portion 106 to continue with the reading of the next transmission frame from another RFID tag 126 of the plurality of RFID tags 126 deployed in an exemplary deployment environment. This corresponds to step 630 as is depicted in the flowchart of figure 6.
Similarly upon completion of step 650, the RFID reader protocol 334 dictates the RFID reader portion 106 to continue with the reading of the next transmission frame from another RFID tag 126 of the plurality of RFID tags 126 deployed in an exemplary deployment environment. This corresponds to step 630 as is depicted in the flowchart of figure 6.
In the final step of the method illustrated by the flowchart of figure 6, a determination of whether all the RFID tags 126 of the plurality of RFID tags 126 deployed in an exemplary deployment environment have been read by the portable RFID reader 102 of the present invention is made. This step corresponds to step, 635 of the flowchart of figure 6.
If all the transmission frames corresponding to all the RFID tags 126 of the plurality of RFID tags 126 deployed in an exemplary environment have not been read by the RFID reader portion 106 of the portable RFID reader 102 of the present invention, the steps inclusive of steps 615, 620, 640, 645, 650, 625, 630 and 635 will repeated until all transmission frames from all the RFID tags 126 have been read. On the other hand if all transmission frames corresponding to the plurality of RFID tags 126 have been read, the method terminates by proceeding to the transmission of a packet frame containing all the RFID tag 126 identifier strings of all the successfully read RFID tag transmission frames that have been read, to the remote host 134 via the end device portion 114 of the portable RFID reader 102 as is illustrated in figure 7.
With reference to figure 7, illustrated is the process in which a reconfigured transmission frame containing all the RFID tag 126 identifier strings of the plurality of RFID tag 126 transmission frames of the plurality of RFID tags 126 in an exemplary environment is transmitted by the end device portion 114 of the portable RFID reader 102 of the present invention to the remote host 134.
The first step of the process illustrated by the flowchart of figure 7 i.e. step 705 entails the retrieval of data by the software interface layer 205 from the end device protocol library 336 and consequently enabling the transmitting of a transmission frame containing all the RFID tag 126 identifier strings of the plurality of RFID tags 126 in an exemplary deployment environment from the end device portion 114 to the remote host 134 via the self healing network of transceivers 132.
In the subsequent step, i.e. step 710, the end device protocol library 336 through the end device controller portion 116 of the controller module switches the end device transceiver unit 118 to the transmit mode of operation thus causing the end device transceiver 118 to exit the sleep mode of operation. In the subsequent step, i.e. step 715, the end device transceiver unit 118 once in the transmitter mode of operation, transmits/broadcasts the thus packaged transmission frame packet containing the node identifier strings of all the RFID tags 126 of the plurality of RFID tags 126 in an exemplary deployment environment to the remote host 134 via the self healing network of transceiver 132. After transmission, the end device transceiver unit 118 is switched back to the receiver mode of operation in anticipation of receiving an acknowledgement from the remote host 134 via the self healing network of transceivers 132.
Following step 715, the subsequent step, i.e. step 720 entails the determination of whether the transmission frame containing all the identifier strings of the successfully identified RFID tags 126 of an exemplary deployment environment of RFID tags 126 to the remote host 134 is successful.
Upon receipt of the transmission frame of all the RFID node identifier strings of all the successfully read RFID tags 126 of the plurality of RFID tags 126, the remote host 134 will transmit a network level acknowledgement to the plurality of transceivers of the self healing network of transceivers 132. The transceivers of the self healing network of transceivers 132 will in turn transmit the network level acknowledgement to the RFID portable reader 102 of the present invention. The receipt of this network level acknowledgement by the end device transceiver 118 of the portable RFID reader 102, confirms that the transmission frame containing all the RFID tag 126 node identifier strings of the plurality of RFID tags 126 has been received by the remote host 134. On the other hand, if said transmission frame was not received by the remote host 134, the remote host 134 would not transmit a network level acknowledgement to the plurality of transceivers of the self healing communications network of transceivers 132 and consequently the portable RFID reader 102 (the end device portion 114 of the RFID portable reader 102) will not receive said network level acknowledgement. If it has been determined in the preceding step (step 720) that the transmission frame containing all the RFID tag 126 identifier strings of the plurality of RFID tags 126 has not been successfully transmitted to the remote host 134, the steps 715 and 720 are repeated until a successful transmission occurs.

Claims

1. A portable RFID reader (102) for use in RFID systems that is adapted for indoor real time location system applications, comprising: a first transceiver unit (110) integrated with a first antenna (112); a second transceiver unit (118) integrated with a second antenna (120); an electronic buffer circuitry; a display (122); a controller having a RFID reader controller portion (108) and an end device controller portion (116); and a power supply (138); characterized in that; the first transceiver unit (110) that is integrated with the first antenna (112) in combination with the RFID reader controller portion (108) cooperate to enable bidirectional communication with a plurality of RFID tags (126) in the deployed environment; and the second transceiver unit (118) that is integrated with the second antenna (120) in combination with the end device controller portion (116) cooperate to enable bidirectional communication with a host (134) via a plurality of transceivers that act together to form a self healing mesh network (132).
2. A portable RFID reader (102) according to claim 1 , wherein the first transceiver unit (110) and the first antenna (112) in combination with the RFID reader controller portion (108) form an RFID reader portion (106) that has the functionality of conventional RFID readers (102).
3. A portable RFID reader (102) according to claim 1 , wherein the second transceiver unit (118) and the second antenna (120) in combination with the end device controller portion (116) form an end device portion (114) that is designated to performing computations based on information received by wireless transmission from a remote host (134).
4. A portable RFID reader (102) according to claim 1 , further comprising a software layer (205) that resides within the memory of the controller, wherein the software layer (205) includes a RFID reader protocol library (334) and an end device protocol library (336).
5. A portable RFID reader (102) according to claim 4, wherein the software layer (205) dictates the communication between the RFID reader portion (106) and the plurality of RFID tags (126) and the communication between the end device portion (114) and the remote host (134) by way of a common data communication protocol that includes the IEEE 802.15.4 protocol.
6. A portable RFID reader (102) according to claim 5, wherein the end device portion (114) or the RFID reader portion (106) transmit or receive information at any one time from a remote host (134) or a plurality of RFID tags (126).
7. A portable RFID reader (102) according to claim 4 or 5, wherein the RFID reader protocol library (334) includes a RFID tag (126) node identifier list, source code that define the initialization of the RFID reader portion (110), an information transmission approach utilized for different commands received from a remote host (134) via the end device portion (114) and detection and comparison of received tag information via wireless transmission.
8. A portable RFID reader (102) according to claim 4 or 5, wherein the RFID reader protocol library (334) further includes an algorithm that implements a method of polling RFID tags (126) by the RFID reader portion (106) that involves indentifying the RFID tags (106) of interest to the RFID reader with respect to the instructions relayed from the host (134) and utilizing a spatial mechanism to reduce RFID tag (126) information collection time and unnecessary collection rounds.
9. A portable RFID reader (102) according to claim 4, wherein the end device protocol library (336) includes a method of receiving information by the end device portion (114) via the end device transceiver (118) from a remote host (134) that includes toggling the end device portion (114) between a sleep mode and active mode to minimize power consumption.
10. A portable RFID reader (102) according to claim 4, wherein the RFID reader protocol library (334) further includes an algorithm that implements a method of enabling the fast recognition of a plurality of RFID tags (126) in a network of distributed RFID tags (126) by making use of the knowledge of RFID tag (126) implementation for a given deployment application and environment.
11. A portable RFID reader (102) according to claim 10, wherein the method involves identifying each individual RFID tag (126) by tag type or tag family as is provided (encoded) in a RFID tag's (126) identifier string portion (sync bits) of the RFID tag's (126) transmission frame.
12. A portable RFID reader (102) according to claim 10, wherein the method involves comparing each individual RFID tag (126) identifier string portion encoded in the sync bit of the RFID tag's transmission frame with a corresponding entry in a RFID tag node identifier list that resides in the RFID reader protocol library (334).
13. A method of enabling the fast recognition of a plurality of RFID tags (126) in a network of distributed RFID tags (126) by identifying each individual tag by tag type or tag family as is provided (encoded) in a RFID tag's identifier string portion (sync bits) of the tag's (126) transmission frame comprising of the steps of: i.) configuring the RFID reader portion (106) in the receive mode of operation, in anticipation of receiving transmission frames from the plurality of RFID tags (126); parsing the received transmission frames from the plurality of RFID tags (126); initializing a "RFID tag counter" to a zero count, the counter residing in an area of memory belonging to the controller module; comparing a node identifier string encoded in the sync bits of the received RFID tag (126) transmission frame pertaining to a particular RFID tag (126) with a corresponding entry in a RFID tag (126) node identifier list; v.) discarding the received RFID tag (126) transmission frame if the identifier string of the transmission frame does not exist in the RFID tag (126) node identifier list; vi.) extending the reading and processing of the subsequent characters following the sync bits of the received RFID tag (126) transmission frame, if the RFID tag (126) identifier string matches with an entry in the RFID tag
(126) node identifier list; incrementing the "RFID tag counter" upon a successful reading of a RFID tag (126) transmission frame with a node identifier string that matches with an entry available in the RFID tag (126) node identifier list; repackaging the successfully read RFID tag (126) transmission frame's identifier string portion into another transmission frame for transmission to a remote host (134) for administration purposes; and receiving a subsequent RFID tag (126) transmission frame and repeating steps (iv.) to (viii.) until all the RFID tags (126) in an exemplary deployment environment have been read.
PCT/MY2011/000167 2011-01-28 2011-06-30 Portable radio frequency identification reader for real time location systems WO2012102600A1 (en)

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