WO2008030446A2 - Systèmes de lecteurs rfid et procédés pour sauter d'un canal de fréquence avec une interference rf - Google Patents

Systèmes de lecteurs rfid et procédés pour sauter d'un canal de fréquence avec une interference rf Download PDF

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Publication number
WO2008030446A2
WO2008030446A2 PCT/US2007/019323 US2007019323W WO2008030446A2 WO 2008030446 A2 WO2008030446 A2 WO 2008030446A2 US 2007019323 W US2007019323 W US 2007019323W WO 2008030446 A2 WO2008030446 A2 WO 2008030446A2
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WIPO (PCT)
Prior art keywords
channel
detected
channels
interference
chosen
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Application number
PCT/US2007/019323
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English (en)
Other versions
WO2008030446A3 (fr
Inventor
Christopher J. Diorio
Aanand Esterberg
Thomas G. Anderl
Scott A. Cooper
Original Assignee
Impinj, Inc.
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
Priority claimed from US11/849,737 external-priority patent/US7592897B2/en
Priority claimed from US11/849,804 external-priority patent/US7589618B2/en
Application filed by Impinj, Inc. filed Critical Impinj, Inc.
Publication of WO2008030446A2 publication Critical patent/WO2008030446A2/fr
Publication of WO2008030446A3 publication Critical patent/WO2008030446A3/fr

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Classifications

    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/003—Arrangements for allocating sub-channels of the transmission path
    • H04L5/0058—Allocation criteria
    • H04L5/0062—Avoidance of ingress interference, e.g. ham radio channels
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/713—Spread spectrum techniques using frequency hopping
    • H04B1/715—Interference-related aspects
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L5/00—Arrangements affording multiple use of the transmission path
    • H04L5/0001—Arrangements for dividing the transmission path
    • H04L5/0003—Two-dimensional division
    • H04L5/0005—Time-frequency
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04B—TRANSMISSION
    • H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
    • H04B1/69—Spread spectrum techniques
    • H04B1/713—Spread spectrum techniques using frequency hopping
    • H04B1/715—Interference-related aspects
    • H04B2001/7154—Interference-related aspects with means for preventing interference
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
    • H04L1/00—Arrangements for detecting or preventing errors in the information received
    • H04L1/004—Arrangements for detecting or preventing errors in the information received by using forward error control
    • H04L1/0045—Arrangements at the receiver end

Definitions

  • RFID Radio Frequency IDentification
  • Radio Frequency IDentification (RFID) systems typically include RFID tags and RFID readers. RFID readers are also known as RFID reader/writers or RFID interrogators. RFID systems can be used in many ways for locating and identifying objects to which the tags are attached. RFED systems are particularly useful in product-related and service-related industries for tracking large numbers of objects being processed, inventoried, or handled. In such cases, an RFE) tag is usually attached to an individual item, or to its package.
  • RFID techniques entail using an RFID reader to interrogate one or more RFE) tags.
  • the reader transmitting a Radio Frequency (RF) wave performs the interrogation.
  • RF Radio Frequency
  • a tag that senses the interrogating RF wave responds by transmitting back another RF wave.
  • the tag generates the transmitted back RF wave either originally, or by reflecting back a portion of the interrogating RF wave in a process known as backscatter.
  • Backscatter may take place in a number of ways.
  • the reflected-back RF wave may further encode data stored internally in the tag, such as a number.
  • the response is demodulated and decoded by the reader, which thereby identifies, counts, or otherwise interacts with the associated item.
  • the decoded data can denote a serial number, a price, a date, a destination, other attribute(s), any combination of attributes, and so on.
  • An RFE tag typically includes an antenna system, a radio section, a power management section, and frequently a logical section, a memory, or both.
  • the power management section included an energy storage device, such as a battery.
  • RFE) tags with an energy storage device are known as active tags. Advances in semiconductor technology have miniaturized the electronics so much that an RFE) tag can be powered solely by the RF signal it receives. Such RFE) tags do not include an energy storage device, and are called passive tags.
  • RFE Radio Fidelity
  • the present invention provides RFE) readers, systems, and methods for overcoming the effects of RF interference. While a system is communicating in a channel, RF interference is monitored. If it is low, then the next channel to be hopped onto is chosen in an unbiased manner. But if interference is high, then the next channel to be hopped onto is chosen in a biased manner that disfavors at least one channel over another, in view of the detected interference.
  • FIG. 1 is a block diagram of components of an RFID system.
  • FIG. 2 is a diagram showing components of a passive RFID tag, such as a tag that can be used in the system of FIG. 1.
  • FIG. 3 is a conceptual diagram for explaining a half-duplex mode of communication between the components of the RFID system of FIG. 1.
  • FIG. 4 is a block diagram of a whole RFID reader system according to embodiments.
  • FIG. 5 is a flowchart for illustrating methods according to embodiments.
  • FIG. 6 is a flowchart for illustrating performing an operation of a method of FIG. 5.
  • FIG. 7 is a diagram showing a spectrum of frequency channels available for transmitting, and a channel among them that is being used in an embodiment of a method of FIG. 5.
  • FIG. 8 is a diagram showing probabilities among the channels of FIG. 7 for being the next one to be hopped on to from the present one.
  • FIG. 9 A is a diagram showing a history of chosen channels made by various embodiments.
  • FIG. 9B is a diagram showing how probabilities among the channels of FIG. 9 A are determined.
  • FIG. 10 is a diagram for illustrating attempting to detect a specific interferer channel according to embodiments.
  • FIG. 11 is a diagram for illustrating an interferer channel detected according embodiments.
  • the present invention provides RFID readers, systems, and performance-based methods for overcoming the effects of RF interference.
  • the invention is now described in more detail.
  • FIG. 1 is a diagram of components of a typical RFID system 100, incorporating aspects of the invention.
  • An RFID reader 110 transmits an interrogating Radio Frequency (RF) wave 112.
  • RFID tag 120 in the vicinity of RFID reader 110 may sense interrogating RF wave 112, and generate wave 126 in response.
  • RFID reader 110 senses and interprets wave 126.
  • RF Radio Frequency
  • Reader 110 and tag 120 exchange data via wave 112 and wave 126.
  • the data is modulated onto, and decoded from, RF waveforms.
  • Encoding the data in waveforms can be performed in a number of different ways. For example, protocols are devised to communicate in terms of symbols, also called RFID symbols. A symbol for communicating can be a delimiter, a calibration symbol, and so on. Further symbols can be implemented for ultimately exchanging binary data, such as "0" and "1", if that is desired. In turn, when the waveforms are processed internally by reader 110 and tag 120, they can be equivalently considered and treated as numbers having corresponding values, and so on.
  • Tag 120 can be a passive tag or an active tag, i.e. having its own power source. Where tag 120 is a passive tag, it is powered from wave 112.
  • RFID reader 110 also receives RF interference 128. This may be generated by other readers in the vicinity, and so on. Sometimes, interference 128 is detected, and in some instances it is determined to be objectionable, as per embodiments of the invention.
  • FIG. 2 is a diagram of an RFID tag 220, which can be the same as tag 120 of FIG. 1.
  • Tag 220 is implemented as a passive tag, meaning it does not have its own power source. Much of what is described in this document, however, applies also to active tags.
  • Tag 220 is formed on a substantially planar inlay 222, which can be made in many ways known in the art.
  • Tag 220 includes an electrical circuit, which is preferably implemented in an integrated circuit (IC) 224.
  • IC 224 is arranged on inlay 222.
  • Tag 220 also includes an antenna for exchanging wireless signals with its environment.
  • the antenna is usually flat and attached to inlay 222.
  • IC 224 is electrically coupled to the antenna via suitable antenna ports (not shown in FIG. 2).
  • the antenna may be made in a number of ways, as is well known in the art.
  • the antenna is made from two distinct antenna segments 227, which are shown here forming a dipole. Many other embodiments are possible, using any number of antenna segments.
  • an antenna can be made with even a single segment. Different places of the segment can be coupled to one or more of the antenna ports of IC 224. For example, the antenna can form a single loop, with its ends coupled to the ports. When the single segment has more complex shapes, it should be remembered that, at the frequencies of RFID wireless communication, even a single segment could behave like multiple segments.
  • a signal is received by the antenna, and communicated to IC 224.
  • IC 224 both harvests power, and responds if appropriate, based on the incoming signal and its internal state, hi order to respond by replying, IC 224 modulates the reflectance of the antenna, which generates the backscatter from a wave transmitted by the reader. Coupling together and uncoupling the antenna ports of IC 224 can modulate the reflectance, as can a variety of other means.
  • antenna segments 227 are separate from IC 224. hi other embodiments, antenna segments may alternately be formed on IC 224, and so on.
  • the components of the RFID system of FIG. 1 may communicate with each other in any number of modes.
  • One such mode is called full duplex.
  • Another such mode is called half-duplex, and is described below.
  • FIG. 3 is a conceptual diagram 300 for explaining the half-duplex mode of communication between the components of the RFED system of FIG. 1, especially when tag 120 is implemented as passive tag 220 of FIG. 2.
  • the explanation is made with reference to a TIME axis, and also to a human metaphor of "talking” and “listening”. The actual technical implementations for "talking" and “listening” are now described.
  • RFID reader 110 and RFID tag 120 talk and listen to each other by taking turns.
  • TIME when reader 110 talks to tag 120 the communication session is designated as "R->T”, and when tag 120 talks to reader 110 the communication session is designated as "T->R”.
  • R->T when reader 110 talks to tag 120 the communication session is designated as "R->T”
  • T->R When tag 120 talks to reader 110 the communication session is designated as "T->R”.
  • TIME a sample R- ⁇ T communication session occurs during a time interval 312, and a following sample T->R communication session occurs during a time interval 326.
  • interval 312 is typically of a different duration than interval 326 - here the durations are shown approximately equal only for purposes of illustration.
  • RFID reader 110 talks during interval 312, and listens during interval 326.
  • RFID tag 120 listens while reader 110 talks (during interval 312), and talks while reader 110 listens (during interval 326).
  • reader 110 talks to tag 120 as follows.
  • reader 110 transmits wave 112, which was first described in FIG. 1.
  • tag 120 receives wave 112 and processes it, to extract data and so on.
  • tag 120 does not backscatter with its antenna, and according to block 382, reader 110 has no wave to receive from tag 120.
  • tag 120 talks to reader 110 as follows.
  • reader 110 transmits a Continuous Wave (CW), which can be thought of as a carrier signal that ideally encodes no information.
  • CW Continuous Wave
  • this carrier signal serves both to be harvested by tag 120 for its own internal power needs, and also as a wave that tag 120 can backscatter.
  • tag 120 does not receive a signal for processing.
  • tag 120 modulates the CW emitted according to block 356, so as to generate backscatter wave 126.
  • reader 110 receives backscatter wave 126 and processes it.
  • an RFID reader / interrogator may communicate with one or more RFID tags in any number of ways. Some such ways are called protocols.
  • a protocol is a specification that calls for specific manners of signaling between the reader and the tags.
  • Gen2 Spec One such protocol is called the Specification for RFID Air Interface - EPC (TM) Radio-Frequency Identity Protocols Class- 1 Generation-2 UHF RFID Protocol for Communications at 860 MHz - 960 MHz, which is also colloquially known as "the Gen2 Spec".
  • the Gen2 Spec has been ratified by EPCglobal, which is an organization that maintains a website at: ⁇ http://www.epcglobalinc.org/> at the time this document is initially filed with the USPTO.
  • reader 110 and tag 120 communicate in terms of time.
  • communications between reader 110 and tag 120 may be restricted according to frequency.
  • One such restriction is that the available frequency spectrum may be partitioned into divisions that are called channels. Different partitioning manners may be specified by different regulatory jurisdictions and authorities (e.g. FCC in North America, CEPT in Europe, etc.).
  • Reader 110 typically transmits with a transmission spectrum that lies within one channel.
  • the authorities permit aggregating multiple channels into one or more larger channels, but for all practical purposes an aggregate channel can again be considered a single, albeit larger, individual channel.
  • Tag 120 can respond with a backscatter that is modulated directly onto the frequency of the reader's emitted CW, also called baseband backscatter.
  • tag 120 can respond with a backscatter that is modulated onto a frequency, developed by tag 120, that is different from the reader's emitted CW, and this modulated tag frequency is then impressed upon the reader's emitted CW.
  • This second type of backscatter is called subcarrier backscatter.
  • the subcarrier frequency can be within the reader's channel, can straddle the boundaries with the adjacent channel, or can be wholly outside the reader's channel.
  • a number of jurisdictions require a reader to hop to a new channel on a regular basis. When a reader hops to a new channel it may encounter RF energy there that could interfere with communications.
  • Embodiments of the present disclosure can be useful in different RFED environments, for example, in the deployment of RFID readers in sparse- or dense-reader environments, in environments with networked and disconnected readers such as where a hand-held reader may enter the field of networked readers, in environments with mobile readers, or in environments with other interference sources. It will be understood that the present embodiments are not limited to operation in the above environments, but may provide improved operation in such environments.
  • FIG. 4 is a block diagram of a whole RFID reader system 400 according to embodiments.
  • System 400 includes a local block 410, and optionally remote components 470.
  • Local block 410 and remote components 470 can be implemented in any number of ways. It will be recognized that reader 110 of FIG. 1 is the same as local block 410, if remote components 470 are not provided. Alternately, reader 110 can be implemented instead by system 400, of which only the local block 410 is shown in FIG. 1.
  • Local block 410 is responsible for communicating with the tags.
  • Local block 410 includes a block 451 of an antenna and a driver of the antenna for communicating with the tags.
  • Some readers like that shown in local block 410, contain a single antenna and driver. Some readers contain multiple antennas and drivers and a method to switch signals among them, including sometimes using different antennas for transmitting and for receiving. And some readers contain multiple antennas and drivers that can operate simultaneously.
  • a demodulator/decoder block 453 demodulates and decodes backscattered waves received from the tags via antenna block 451.
  • Modulator/encoder block 454 encodes and modulates an RF wave that is to be transmitted to the tags via antenna block 451.
  • Local block 410 additionally includes an optional local processor
  • Processor 456 may be implemented in any number of ways known in the art. Such ways include, by way of examples and not of limitation, digital and/or analog processors such as microprocessors and digital-signal processors (DSPs); controllers such as microcontrollers; software running in a machine such as a general purpose computer; programmable circuits such as Field Programmable Gate Arrays (FPGAs), Field-Programmable Analog Arrays (FPAAs), Programmable Logic Devices (PLDs), Application Specific Integrated Circuits (ASIC), any combination of one or more of these; and so on. In some cases some or all of the decoding function in block 453, the encoding function in block 454, or both, may be performed instead by processor 456.
  • DSPs digital-signal processors
  • controllers such as microcontrollers
  • software running in a machine such as a general purpose computer
  • programmable circuits such as Field Programmable Gate Arrays (FPGAs), Field-Programmable Analog Arrays (FPAAs),
  • Local block 410 additionally includes an optional local memory
  • Memory 457 may be implemented in any number of ways known in the art. Such ways include, by way of examples and not of limitation, nonvolatile memories (NVM), read-only memories (ROM), random access memories (RAM), any combination of one or more of these, and so on. Memory 457, if provided, can include programs for processor 456 to run, if provided.
  • NVM nonvolatile memories
  • ROM read-only memories
  • RAM random access memories
  • memory 457 stores data read from tags, or data to be written to tags, such as Electronic Product Codes (EPCs), Tag Identifiers (TIDs) and other data.
  • EPCs Electronic Product Codes
  • TIDs Tag Identifiers
  • Memory 457 can also include reference data that is to be compared to the EPC codes, instructions and/or rules for how to encode commands for the tags, modes for controlling antenna 451, and so on.
  • local memory 457 is provided as a database.
  • Some components of local block 410 typically treat the data as analog, such as the antenna / driver block 451.
  • Other components such as memory 457 typically treat the data as digital.
  • remote components 470 are indeed provided, they are coupled to local block 410 via an electronic communications network 480.
  • Network 480 can be a Local Area Network (LAN), a Metropolitan Area Network (MAN), a Wide Area Network (WAN), a network of networks such as the internet, and so on.
  • local block 410 then includes a local network connection 459 for communicating with network 480.
  • remote component(s) 470 there can be one or more remote component(s) 470. If more than one, they can be located at the same location, or in different locations. They can access each other and local block 410 via network 480, or via other similar networks, and so on. Accordingly, remote component(s) 470 can use respective remote network connections. Only one such remote network connection 479 is shown, which is similar to local network connection 459, etc.
  • Remote component(s) 470 can also include a remote processor
  • Processor 476 can be made in any way known in the art, such as was described with reference to local processor 456.
  • Remote component(s) 470 can also include a remote memory
  • Memory 477 can be made in any way known in the art, such as was described with reference to local memory 457.
  • Memory 477 may include a local database, and a different database of a Standards Organization, such as one that can reference EPCs.
  • Block 490 includes those that are provided of the following: local processor 456, remote processor 476, local network connection 459, remote network connection 479, and by extension an applicable portion of network 480 that links connection 459 with connection 479. The portion can be dynamically changeable, etc.
  • block 490 can receive and decode RF waves received via antenna 451, and cause antenna 451 to transmit RF waves according to what it has processed.
  • Block 490 includes either local processor 456, or remote processor 476, or both. If both are provided, remote processor 476 can be made such that it operates in a way complementary with that of local processor 456. In fact, the two can cooperate. It will be appreciated that block 490, as defined this way, is in communication with both local memory 457 and remote memory 477, if both are present.
  • block 490 is location agnostic, in that its functions can be implemented either by local processor 456, or by remote processor 476, or by a combination of both. Some of these functions are preferably implemented by local processor 456, and some by remote processor 476. Block 490 accesses local memory 457, or remote memory 477, or both for storing and/or retrieving data.
  • Reader system 400 operates by block 490 generating communications for RFID tags. These communications are ultimately transmitted by antenna block 451, with modulator/encoder block 454 encoding and modulating the information on an RF wave. Then data is received from the tags via antenna block 451, demodulated and decoded by demodulator/decoder block 453, and processed by processing block 490.
  • the invention also includes methods. Some are methods of operation of an RFE) reader or RFK) reader system. Others are methods for controlling an RFED reader or RFID reader system.
  • Another optional way is for one or more of the individual operations of the methods to be performed in conjunction with one or more human operators performing some. These human operators need not be collocated with each other, but each can be only with a machine that performs a portion of the program.
  • the invention additionally includes programs, and methods of operation of the programs.
  • a program is generally defined as a group of steps or operations leading to a desired result, due to the nature of the elements in the steps and their sequence.
  • a program is usually advantageously implemented as a sequence of steps or operations for a processor, such as the structures described above.
  • Performing the steps, instructions, or operations of a program requires manipulation of physical quantities.
  • these quantities may be transferred, combined, compared, and otherwise manipulated or processed according to the steps or instructions, and they may also be stored in a computer-readable medium.
  • These quantities include, for example, electrical, magnetic, and electromagnetic charges or particles, states of matter, and in the more general case can include the states of any physical devices or elements. It is convenient at times, principally for reasons of common usage, to refer to information represented by the states of these quantities as bits, data bits, samples, values, symbols, characters, terms, numbers, or the like. It should be borne in mind, however, that all of these and similar terms are associated with the appropriate physical quantities, and that these terms are merely convenient labels applied to these physical quantities, individually or in groups.
  • the invention furthermore includes storage media. Such media, individually or in combination with others, have stored thereon instructions of a program made according to the invention.
  • a storage medium according to the invention is a computer-readable medium, such as a memory, and is read by a processor of the type mentioned above. If a memory, it can be implemented in a number of ways, such as Read Only Memory (ROM), Random Access Memory (RAM), etc., some of which are volatile and some non- volatile.
  • the program may be stored in a computer-readable medium, it should be clear to a person skilled in the art that it need not be a single memory, or even a single machine. Various portions, modules or features of it may reside in separate memories, or even separate machines. The separate machines may be connected directly, or through a network such as a local access network (LAN) or a global network such as the Internet.
  • LAN local access network
  • the Internet a global network
  • the software can be unitary, or thought in terms of various interconnected distinct software modules.
  • FIG. 5 is flowchart 503 illustrating a method according to an embodiment of the invention.
  • the method of flowchart 503 is for communicating with RFID tags using the available communication channels, and may be practiced by different embodiments of the invention, including but not limited to RFID reader system 400, operational block 490, software according to embodiments, and so on.
  • a first wireless signal is transmitted to the RFID tags at a present channel. Transmission can be accomplished by causing a first wireless RF signal to be transmitted to the RFID tags via an antenna of an RFID reader system.
  • This first wireless signal has a frequency carrier in the present channel, which is also called a first one of the available channels for purposes of when frequency hopping starts to be considered.
  • a system could be hopping through many channels, and at some point in time, operation 510 would be at a channel considered the first or present channel.
  • tag signals are received. These received tag signals are typically backscattered from the RFID tags in response to the first signal. When they are received by local block 410, there is an attempt to decode them, also by using error correction codes. This can be performed in a number of ways, for example as is described in copending U.S. Patent Application Ser. No. 11/388,235, published on 2006-10-19 as document No. 2006/0236203, due to be assigned to the same assignee.
  • Operation 540 is optional, in that it need not take place in every embodiment of the invention, although it is preferred.
  • RF energy is received, which is associated with transmitting in the first channel. This RF energy could include the tag signals of operation 530, and also other energy such as noise and other signals, and will be elaborated on later in this document.
  • a next operation 550 it is determined whether or not objectionable interference has been detected for communicating in the first channel of operation 510.
  • This can be performed in any number of ways, and some exemplary such ways are described later in this document.
  • the level of interference that is found objectionable can usually be set to optimize system performance.
  • it can be adjusted in some embodiments, sometimes dynamically. For example, higher interference tolerance thresholds may be established where strong interference is detected in many of the available communication channels.
  • execution may return to operation 510, or proceed to operation 560.
  • execution always returns to operation 510, until there is an ordinary decision to hop to another channel. Such an ordinary decision may be arrived at in any number of ways.
  • One such way includes that a determination is made from decoded tag signals, of the type of signals that can be optionally received as described in operation 530 later in this document. From such tag signals it can be determined that an inventory round of the RFID tags is complete. Inventory rounds are discussed in U.S. Patent Application Ser. No. 11/210,384, published on 2005-Dec-22 as Publication No. 2005/0280505 Al, with one of many possible examples given in FIG. 9 of that document.
  • Another such way includes that a determination is made that the first signal has been transmitted for a first dwell time, which further approaches a preset limit dwell time for dwelling in a single channel continuously.
  • Each system would have its own ways of so determining.
  • execution may proceed to operation 560.
  • the ordinary decision will be bypassed.
  • the second signal is transmitted without transmitting any more signals in the first channel. Li others, the first signal is continued to be transmitted for some time interval in the first channel, and then there is the hopping that is now described.
  • a next or second one of the available channels is chosen, other than the first channel.
  • the second channel can be chosen in an unbiased manner if it is determined that no objectionable interference has been detected at operation 550.
  • This unbiased manner includes not favoring any channel over another so as to avoid any interference.
  • the second channel is alternately chosen in a biased manner, which is different from the unbiased manner if it is determined that objectionable interference has been detected at operation 550.
  • This biased manner includes disfavoring at least one channel over another in view of the detected interference.
  • the biased and unbiased manners can be implemented in any number of ways. Some examples as to how this choice is made are described later in this document.
  • an RFID reader system can hop to the next channel chosen at operation 560. After that, execution can return to operation 510, and cause a second signal to be transmitted to the RFID tags, where the present channel will now be the second or next chosen channel.
  • the second signal has a frequency carrier in the chosen second channel. Then there could be a repetition for the next hop, e.g. with determining whether subsequent objectionable interference is detected, etc. It will be understood that these full •iterations of flowchart 503 can happen many times, as an RFID reader hops channels.
  • a quality metric of a tag signal For example, a quality metric is computed in association with one or more of the received tag signals. Then it can be determined whether or not objectionable interference has been detected at least from the quality metric.
  • the quality metric can measure any suitable attribute, such as a signal-to-noise ratio, or a measured signal from a decision threshold. The latter reflects a confidence in the decisions made using the threshold, for example as to whether a received waveform segment is really a "high” or a "low”.
  • a tag preamble matching metric can be computed in association with one or more of the received tag signals.
  • This metric can be computed in any number of ways, for example reflecting how well a preamble of one or more of the received tag signals matches an expected preamble. Then it can be determined whether or not objectionable interference has been detected from the tag preamble matching metric, either as computed, or further modified. For example, if the metric crosses a threshold the interference is deemed objectionable, and so on.
  • Errors are indicative of the presence of interference, and their rates are indicative of the level or amount of interference.
  • FIG. 6 is flowchart 650 illustrating a method according to an embodiment of the invention.
  • the method of flowchart 650 can be used for operation 550 of FIG. 5.
  • the method of flowchart 650 may be practiced by different embodiments of the invention, including but not limited to RFID reader system 400, operational block 490, software according to embodiments, and so on.
  • an error detection count is updated.
  • the error detection count is a statistic that can be implemented in any number of ways. For example, the error detection count can be treated as just a number. Or it can be rendered as a ratio with a total number of the tag signals, for example by counting all the replies received at operation 530. Or, as per optional operation 657, the error detection count can be modified according to a channel dwell time.
  • next operation 659 it is determined whether or not the detected interference is objectionable, at least from the error detection count. It will be understood that the method of flowchart 650 can be practiced many times, for updating the error detection count. So, at operation 651 for example, it is determined whether an error has been detected in more of the received tag signals. Operation 659 can be performed in a number of ways, which in turn depend on how the error detection count has been determined in the first place. Some such ways are now described.
  • the determination of whether the level of interference is objectionable can be made from any RF energy received at operation 540.
  • This energy can be received from any of the channels available for communicating with the RFID tags, e.g. all of them, only the present channel, or a group of them, such as a neighborhood of detected channels.
  • the determination of whether the level of interference is objectionable can be made from a combination of factors, including the above factors.
  • an aggregate score can be maintained, which is affected by one or more factors, like missing replies, quality metrics, tag preamble metrics, error counts, and received RF energy.
  • a second one of the available channels is chosen per operation 560.
  • the second channel can be chosen in any number of ways, as is now described in more detail.
  • a diagram 700 has horizontal axis that shows frequency, as it may have been divided in channels.
  • the channels available for communication are shown as 710.
  • Diagram 700 also has a vertical axis showing amplitude or intensity of transmission per channel.
  • Channel 720 is the channel considered as the present channel of operation 510, the only one in which there is transmission.
  • the interferer has been guessed to be near present channel 720, or in a neighborhood around present channel 720.
  • This neighborhood is not necessarily the same as was described above with reference to operation 540, although they are related.
  • the neighborhood of FIG. 7 is described as the channels within a number Nl of present channel 720. It has been found that a good value for number Nl is 3 or 4, absent more information. Of course, the number Nl can be adjusted. Adjustment can be depending on what works for the system, and also depending on other factors, such as a history of detecting objectionable interference in an environment of the RFED tags.
  • a size of the neighborhood of FIG. 7 can also be determined from a manner of receiving or detecting the RF energy, or the amount of received RF energy, or both. For example, if the total received RF energy is larger than a suitable threshold, the neighborhood has at least 11 channels, with Nl being equal to 5. Such a suitable threshold can be -20 dBm. For another example, if the total detected RF energy is less than a suitable threshold, the neighborhood has at least 7 channels, with Nl being equal to 3. Such a suitable threshold again can be -20 dBm.
  • the interferer Since the interferer has been guessed to be a neighborhood of present channel 720, it is optional but preferred that the second channel is chosen per operation 560 in a manner that disfavors all of the channels in the neighborhood. For example, the channels in the neighborhood could have much less chance of being chosen, than the remaining ones of the available channels. In some instances, they could have no chance of being so chosen, as illustrated in the following two examples.
  • FIG. 8 is a diagram 800 that shows probabilities among the channels of FIG. 7 for being the next one to be hopped on to from channel 720. There is zero probability that the next channel will be 720. According to profiles 875, every one of the channels other than channel 720 has a substantially equal chance of being chosen as the second channel.
  • FIG. 8 shows what is also known as the neutral manner, and has to do with the fact that prior choices have made it so that all channels are being used with the same frequency.
  • One way for example, is to have hopping tables that always make enough of a hop, for example the next channel is always 5 or more channels away.
  • compensation is performed.
  • FIG. 9 A is a diagram 910 showing channels 710, and a history of which ones have been chosen in the past and how often, as a bar chart. It will be noted that, according to a comment 973, there are two regions that have been used with lesser preference than the others. Such can happen if there are interferers that are localized, i.e. don't hop channels themselves.
  • FIG. 9B is a diagram 980 showing how probabilities among the channels of FIG. 9A can be determined, so as to avoid the channels in the neighborhood of present channel 720, and so as to further compensate for the lesser preference.
  • the probabilities are a bar chart 985, which are the complement of the bar chart of FIG. 9 A. Thus, it favors heavily channels that are pointed out in comment 973.
  • an effort is made to detect one of the channels as the interferer's channel.
  • the interferer could be an RFID reader operating according to the same channel scheme as shown in FIG. 7, and the RF interference would be ideally confined to a single channel.
  • Detection can be attempted in any number of ways. For example, RF energy can be received for measuring in individual channels, and the RF energy of neighboring channels can be contrasted. In some embodiments, for example, a certain channel can be detected as the interferer's channel if the certain channel has RF energy above a preset high threshold, while the energy in at least one of its neighboring channels are below a preset low threshold. An example is now described.
  • FIG. 10 is a diagram 1000 for illustrating attempting to detect a specific interferer channel according to embodiments.
  • the horizontal axis is the same as in FIG. 7, showing the available channels.
  • the vertical axis shows RF energy detection thresholds.
  • a pattern 1015 is used to detect the interferer ' s channel, which spans a neighborhood of 9 detected channels. It has a high threshold of -20 dBm, and a low threshold of -70 dBm, although different values can be used, and a different pattern can be used.
  • Pattern 1015 is optimized for detecting the interferer' s channel in the event the interferer is another RFED reader, as per the above.
  • Pattern 1015 can be applied in the neighborhood of comment 773. Its center channel (channel "0") can be at present channel 720, or at another channel near it. Ideally, pattern 1015 is swept, to detect the interferer. Sweeping is preferably near the neighborhood of present channel 720.
  • FIG. 11 is a diagram 1194 for illustrating an interferer channel detected according embodiments.
  • the interferer unknown for FIG. 7, has now been located and is indicated by comment 1196.
  • the second channel is chosen in such a way that a resulting tag backscatter avoids a center frequency of the interferer's channel.
  • This can be accomplished in any number of ways.
  • the second channel can be chosen in a manner that disfavors all of the channels in a neighborhood of the interferer's channel.
  • the interferer's channel can be chosen as the second channel, and the RFID tags can be commanded to backscatter on the subcarrier instead of on the carrier.
  • the invention includes combinations and subcombinations of the various elements, features, functions and/or properties disclosed herein.
  • the following claims define certain combinations and subcombinations, which are regarded as novel and non-obvious. Additional claims for other combinations and subcombinations of features, functions, elements and/or properties may be presented in this or a related document.

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Mobile Radio Communication Systems (AREA)
  • Near-Field Transmission Systems (AREA)
  • Noise Elimination (AREA)
  • Monitoring And Testing Of Transmission In General (AREA)

Abstract

L'invention concerne des lecteurs RFID, des systèmes et des procédés pour surmonter les effets d'une interférence RF. Tandis qu'un système est en communication dans un canal, une interférence RF est surveillée. Si elle est faible, alors le prochain canal sur lequel on sautera est choisi de manière impartiale. Mais si l'interférence est élevée, alors le canal suivant sur lequel on sautera est choisi de façon partiale, défavorisant au moins un canal par rapport à un autre, compte tenu de l'interférence détectée. Le choix du canal suivant peut ainsi conduire à une diminution de la communication dans les canaux avec beaucoup d'interférences RF.
PCT/US2007/019323 2006-09-07 2007-09-05 Systèmes de lecteurs rfid et procédés pour sauter d'un canal de fréquence avec une interference rf WO2008030446A2 (fr)

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US84280906P 2006-09-07 2006-09-07
US60/842,809 2006-09-07
US91998907P 2007-03-26 2007-03-26
US60/919,989 2007-03-26
US11/849,737 US7592897B2 (en) 2006-04-25 2007-09-04 RFID readers system and methods for early hopping out of a frequency channel in the presence of RF interference
US11/849,737 2007-09-04
US11/849,804 2007-09-04
US11/849,804 US7589618B2 (en) 2006-04-25 2007-09-04 RFID readers systems and methods for hopping away from a frequency channel with RF interference

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3697003A1 (fr) * 2019-02-13 2020-08-19 ABB Schweiz AG Détecteur basé sur radio et procédé pour protéger contre des interférences imprévisibles dans des communications industrielles sans fil

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7589618B2 (en) 2006-04-25 2009-09-15 Diorio Christopher J RFID readers systems and methods for hopping away from a frequency channel with RF interference
US7592897B2 (en) 2006-04-25 2009-09-22 Impinj, Inc. RFID readers system and methods for early hopping out of a frequency channel in the presence of RF interference

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060006986A1 (en) * 2004-07-09 2006-01-12 Kelly Gravelle Multi-protocol or multi-command RFID system
US20060022800A1 (en) * 2004-07-30 2006-02-02 Reva Systems Corporation Scheduling in an RFID system having a coordinated RFID tag reader array

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5394433A (en) * 1993-04-22 1995-02-28 International Business Machines Corporation Frequency hopping pattern assignment and control in multiple autonomous collocated radio networks
US5471469A (en) * 1994-02-08 1995-11-28 Metricon, Inc. Method of resolving media contention in radio communication links
US5828693A (en) * 1996-03-21 1998-10-27 Amtech Corporation Spread spectrum frequency hopping reader system
JP3478062B2 (ja) * 1997-06-12 2003-12-10 三菱電機株式会社 移動通信システム、移動局、及び基地局

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20060006986A1 (en) * 2004-07-09 2006-01-12 Kelly Gravelle Multi-protocol or multi-command RFID system
US20060022800A1 (en) * 2004-07-30 2006-02-02 Reva Systems Corporation Scheduling in an RFID system having a coordinated RFID tag reader array

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP3697003A1 (fr) * 2019-02-13 2020-08-19 ABB Schweiz AG Détecteur basé sur radio et procédé pour protéger contre des interférences imprévisibles dans des communications industrielles sans fil
WO2020164977A1 (fr) * 2019-02-13 2020-08-20 Abb Schweiz Ag Détecteur radioélectrique et procédé de protection contre les brouillages imprévisibles dans des communications sans fil industrielles
US11664922B2 (en) 2019-02-13 2023-05-30 Hitachi Energy Switzerland Ag Radio-based detector and method to protect against unpredictable interference in industrial wireless communications

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