WO2024167987A1

WO2024167987A1 - Collided reply recovery using parallel rfid tag responses

Info

Publication number: WO2024167987A1
Application number: PCT/US2024/014712
Authority: WO
Inventors: Christopher J. Diorio; Rene Dominic Martinez
Original assignee: Impinj Inc
Current assignee: Impinj Inc
Priority date: 2023-02-07
Filing date: 2024-02-07
Publication date: 2024-08-15
Anticipated expiration: 2025-08-07
Also published as: CN120641906A; EP4662588A1

Abstract

A Radio Frequency Identification (RFID) tag integrated circuit (IC), an RFID reader, and methods for an RFID tag IC and an RFID reader are described for collided reply recovery using parallel RFID tag responses. A suitably configured RFID reader may be able to recover multiple tag replies from the collision, for example using error correction techniques or similar approaches. The reader may then be able to serially or simultaneously acknowledge multiple tags using the recovered replies in an inventory round. To enable such serial or simultaneous acknowledgement, RFID tags or tag ICs may be configured to wait for subsequent acknowledgement or access commands upon receiving an incorrect or inapplicable command, instead of immediately effectively exiting the inventory round.

Description

COLLIDED REPLY RECOVERY USING PARALLEL RFID TAG RESPONSES

CROSS REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of U.S. Provisional Patent Application Serial No. 63/443,753 filed on February 7, 2023 and U.S. Provisional Patent Application Serial No. 63/510,264 filed on June 26, 2023. The disclosures of the applications are hereby incorporated by reference for all purposes.

BACKGROUND

[0002] Radio-Frequency Identification (RFID) systems typically include RFID readers, also known as RFID reader/writers or RFID interrogators, and RFID tags. RFID systems can be used in many ways for locating and identifying objects to which the tags are attached. RFID systems are useful in product-related and service-related industries for tracking objects being processed, inventoried, or handled. In such cases, an RFID tag is usually attached to an individual item, or to its package. The RFID tag typically includes, or is, a radio-frequency (RF) integrated circuit (IC).

[0003] In principle, RFID techniques entail using an RFID reader to inventory one or more RFID tags, where inventorying involves singulating a tag, receiving an identifier from a tag, and/or acknowledging a received identifier (e.g., by transmitting an acknowledgement command). “Singulated” is defined as a reader singling-out one tag, potentially from among multiple tags, for a reader-tag dialog. “Identifier” is defined as a number identifying the tag or the item to which the tag is attached, such as a tag identifier (TID), electronic product code (EPC), etc. An “inventory round” is defined as a reader staging RFID tags for successive inventorying. The reader transmitting a Radio-Frequency (RF) wave performs the inventory. The RF wave is typically electromagnetic, at least in the far field. The RF wave can also be predominantly electric or magnetic in the near or transitional near field. The RF wave may encode one or more commands that instruct the tags to perform one or more actions. The operation of an RFID reader sending commands to an RFID tag is sometimes known as the reader “interrogating” the tag. [0004] In typical RFID systems, an RFID reader transmits a modulated RF inventory signal (a command), receives a tag reply, and transmits an RF acknowledgement signal responsive to the tag reply. A tag that replies to the interrogating RF wave does so by transmitting back another RF wave. The tag either generates the transmitted back RF wave 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.

[0005] The reflected-back RF wave may encode data stored 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 time, a destination, an encrypted message, an electronic signature, other attribute(s), any combination of attributes, and so on. Accordingly, when a reader receives tag data it can learn about the item that hosts the tag and/or about the tag itself.

[0006] An RFID tag typically includes an antenna section, a radio section, a powermanagement section, and frequently a logical section, a memory, or both. In some RFID tags the power-management section includes an energy storage device such as a battery. RFID tags with an energy storage device are known as battery-assisted, semiactive, or active tags. Other RFID tags can be powered solely by the RF signal they receive. Such RFID tags do not include an energy storage device and are called passive tags. Of course, even passive tags typically include temporary energy- and data/flag-storage elements such as capacitors or inductors.

BRIEF SUMMARY

[0007] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended as an aid in determining the scope of the claimed subject matter.

[0008] When an RFID reader inventories RFID tags in a population, two or more tags may reply at around the same time, resulting in a "collision”. If the reader is suitably configured, it may be able to recover multiple tag replies from the collision, for example using error correction techniques or similar approaches. The reader may then be able to serially or simultaneously acknowledge multiple tags using the recovered replies in an inventory round. To enable such serial or simultaneous acknowledgement, RFID tags or tag ICs may be configured to wait for subsequent acknowledgement or access commands upon receiving an incorrect or inapplicable command, instead of immediately effectively exiting the inventory round.

[0009] According to some examples, a method for a Radio Frequency Identification (RFID) integrated circuit (IC) includes receiving, via a transceiver block configured to receive commands and send replies, a query command; entering a reply state and sending, via the transceiver block, a first reply to the query command; receiving, via the transceiver block, a first acknowledgement command; determining whether the first acknowledgement command specifies the RFID IC; in response to determining that the first acknowledgement command does not specify the RFID IC, one of waiting in the reply state if the reply state is set to a wait mode; and exiting the reply state if the reply state is set to a go mode.

[0010] According to other examples, the method further includes receiving, via the transceiver block, a first command setting the reply state to one of the wait mode and the go mode. The first command is one of a query command, an acknowledgement command, or a broadcast command. The method further includes determining whether an acknowledgement command specifies the RFID IC by determining whether the acknowledgement command includes a parameter that corresponds to at least part of another parameter sent by the RFID IC in response to the query command; or a special acknowledgement code that specifies all RFID ICs that replied to the query command. The parameter is an RN16.

[0011] According to further examples, the method further includes waiting in the reply state by disabling an existing timeout. The method further includes, while waiting in the reply state: receiving another acknowledgement command; determining that the other acknowledgement command does not include the first parameter or specify the RFID IC; and continuing waiting in the reply state. The method further includes, while waiting in the reply state: in response to receiving an acknowledgement command that specifies the RFID IC, sending an identifier; and waiting for another command specifying the RFID IC or another query command. The method further includes, after sending the identifier, exiting the reply state and entering an acknowledged state in which the RFID IC waits for the other command specifying the RFID IC or another query command. [0012] According to yet other examples, a Radio Frequency Identification (RFID) integrated circuit (IC) includes a transceiver block configured to receive commands and send replies; and a processing block coupled to the transceiver block, where the processing block is configured to perform the actions of method described herein.

[0013] These and other features and advantages will be apparent from a reading of the following detailed description and a review of the associated drawings. It is to be understood that both the foregoing general description and the following detailed description are explanatory only and are not restrictive of aspects as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The following Detailed Description proceeds with reference to the accompanying drawings, in which:

[0015] FIG. l is a block diagram of components of an RFID system.

[0016] 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.

[0017] FIG. 3 is a conceptual diagram for explaining a half-duplex mode of communication between the components of the RFID system of FIG. 1.

[0018] FIG. 4 is a block diagram showing a detail of an RFID tag, such as the one shown in FIG. 2.

[0019] FIG. 5A and 5B illustrate signal paths during tag-to-reader and reader-to-tag communications in the block diagram of FIG. 4.

[0020] FIG. 6 is a block diagram depicting an RFID reader system according to examples.

[0021] FIG. 7 is a diagram depicting query-acknowledgement interactions between an RFID reader system and multiple RFID tags during an inventory round.

[0022] FIG. 8 is a diagram depicting query-acknowledgement interactions between an RFID reader and multiple RFID tags enabled to wait in their current states during an inventory round, according to examples.

[0023] FIG. 9 is a diagram depicting query-acknowledgement interactions between an RFID reader system and multiple RFID tags, where the RFID reader is configured to acknowledge multiple, specified RFID tags, according to examples. [0024] FIG. 10 is a diagram depicting query-acknowledgement interactions between an RFID reader system and multiple RFID tags, where the RFID reader is configured to acknowledge all responding RFID tags, according to examples.

[0025] FIG. 11 is a diagram depicting query-acknowledgement interactions between an RFID reader system and multiple RFID tags, where the RFID reader is configured to initially acknowledge all responding RFID tags, according to examples.

[0026] FIG. 12 depicts a flowchart of a method for an RFID reader to interact with tags modified to wait in certain states, according to examples.

[0027] FIG. 13 depicts a flowchart of a method for an RFID reader system to recover multiple RFID tag responses, according to examples.

DETAILED DESCRIPTION

[0028] In the following detailed description, references are made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments or examples. These embodiments or examples may be combined, other aspects may be utilized, and structural changes may be made without departing from the spirit or scope of the present disclosure. The following detailed description is therefore not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims and their equivalents.

[0029] As used herein, “memory” is one of ROM, RAM, SRAM, DRAM, NVM, EEPROM, FLASH, Fuse, MRAM, FRAM, and other similar volatile and nonvolatile information-storage technologies. Some portions of memory may be writeable and some not. “Instruction” refers to a request to a tag to perform a single explicit action (e.g., write data into memory). “Command” refers to a reader request for one or more tags to perform one or more actions, and includes one or more tag instructions preceded by a command identifier or command code that identifies the command and/or the tag instructions. “Program” refers to a request to a tag to perform a set or sequence of instructions (e.g., read a value from memory and, if the read value is less than a threshold then lock a memory word). “Protocol” refers to an industry standard for communications between a reader and a tag (and vice versa), such as the Class- 1 Generation-2 UHF RFID Protocol for Communications at 860 MHz - 960 MHz by GS1 EPCglobal, Inc. (“Gen2 Protocol”), versions 1.2.0, 2.0, and 3.0 of which are hereby incorporated by reference. [0030] In some examples, an RFID tag responds to an interrogating RFID reader in a backscatter time interval, by modulating symbols representing data values onto backscattered or reflected portions of a reader-transmitted RF wave during the backscatter time interval. The way in which the RFID tag modulates data symbols onto the backscattered RF wave portions may be defined by one or more protocols. For example, the RFID tag may modulate data symbols onto backscattered RF waves using amplitude-shift keying (ASK) or phase-shift keying (PSK), as described in the Gen2 Protocol. In other examples, any other suitable modulation scheme may be used as will be known to one of ordinary skill in the art.

[0031] During the backscatter time interval, the RFID tag may modulate data symbols onto a backscattered RF wave by switching an associated impedance between two or more different values in patterns corresponding to the data symbols. For example, the RFID tag may switch a tag front-end impedance presented to an antenna of the RFID tag between a first impedance value and a second impedance value, thereby switching the reflectance of the antenna, to modulate data symbols onto a backscattered RF wave.

[0032] Data symbols may be modulated onto a backscattered RF wave as patterns of impedance values and/or transitions between impedance values. For example, a data symbol that corresponds to a binary data value of “0” may be represented by a first series of impedance values and/or impedance value transitions, and a data symbol that corresponds to a binary data value of “1” may be represented by a second series of impedance values and/or impedance value transitions.

[0033] FIG. 1 is a diagram of the components of a typical RFID system 100, incorporating examples. An RFID reader 110 and a nearby RFID tag 120 communicate via RF signals 112 and 126. When sending data to tag 120, reader 110 may generate RF signal 112 by encoding the data, modulating an RF waveform with the encoded data, and transmitting the modulated RF waveform as RF signal 112. In turn, tag 120 may receive RF signal 112, demodulate encoded data from RF signal 112, and decode the encoded data. Similarly, when sending data to reader 110 tag 120 may generate RF signal 126 by encoding the data, modulating an RF waveform with the encoded data, and causing the modulated RF waveform to be sent as RF signal 126. The data sent between reader 110 and tag 120 may be represented by symbols, also known as RFID symbols. A symbol may be a delimiter, a calibration value, or implemented to represent binary data, such as “0” and “1”, if desired. Upon processing by reader 110 and tag 120, symbols may be treated as values, numbers, or any other suitable data representations.

[0034] The RF waveforms transmitted by reader 110 and/or tag 120 may be in a suitable range of frequencies, such as those near 900 MHz, 13.56 MHz, or similar. In some examples, RF signals 112 and/or 126 may include non-propagating RF signals, such as reactive near-field signals or similar. RFID tag 120 may be active or battery- assisted (i.e., possessing its own power source), or passive. In the latter case, RFID tag 120 may harvest power from RF signal 112.

[0035] FIG. 2 is a diagram of an RFID tag 220, which may function as tag 120 of FIG. 1. Tag 220 may be formed on a substantially planar inlay 222, which can be made in any suitable way. Tag 220 includes a circuit which may be implemented as an IC 224. In some examples IC 224 is fabricated in complementary metal-oxide semiconductor (CMOS) technology. In other examples IC 224 may be fabricated in other technologies such as bipolar junction transistor (BJT) technology, metalsemiconductor field-effect transistor (MESFET) technology, and others as will be well known to those skilled in the art. IC 224 is arranged on inlay 222.

[0036] Tag 220 also includes an antenna for transmitting and/or interacting with RF signals. In some examples the antenna can be etched, deposited, and/or printed metal on inlay 222; conductive thread formed with or without a substrate; nonmetallic conductive (such as graphene) patterning on the substrate; a first antenna coupled inductively, capacitively, or galvanically to a second antenna; or can be fabricated in myriad other ways that exist for forming antennas to receive RF waves. In some examples the antenna may even be formed in IC 224. Regardless of the antenna type, IC 224 is electrically coupled to the antenna via suitable IC contacts (not shown in FIG. 2). The term “electrically coupled” as used herein may mean a direct electrical connection, or it may mean a connection that includes one or more intervening circuit blocks, elements, or devices. The “electrical” part of the term “electrically coupled” as used in this document shall mean a coupling that is one or more of ohmic/galvanic, capacitive, and/or inductive. Similarly, the terms “electrically isolated” or “electrically decoupled” as used herein mean that electrical coupling of one or more types (e.g., galvanic, capacitive, and/or inductive) is not present, at least to the extent possible. For example, elements that are electrically isolated from each other are galvanically isolated from each other, capacitively isolated from each other, and/or inductively isolated from each other. Of course, electrically isolated components will generally have some unavoidable stray capacitive or inductive coupling between them, but the intent of the isolation is to minimize this stray coupling when compared with an electrically coupled path.

[0037] IC 224 is shown with a single antenna port, comprising two IC contacts electrically coupled to two antenna segments 226 and 228 which are shown here forming a dipole. Many other examples are possible using any number of ports, contacts, antennas, and/or antenna segments. Antenna segments 226 and 228 are depicted as separate from IC 224, but in other examples the antenna segments may alternatively be formed on IC 224. Tag antennas according to examples may be designed in any form and are not limited to dipoles. For example, the tag antenna may be a patch, a slot, a loop, a coil, a horn, a spiral, a monopole, microstrip, stripline, or any other suitable antenna.

[0038] Diagram 250 depicts top and side views of tag 252, formed using a strap. Tag 252 differs from tag 220 in that it includes a substantially planar strap substrate 254 having strap contacts 256 and 258. IC 224 is mounted on strap substrate 254 such that the IC contacts on IC 224 electrically couple to strap contacts 256 and 258 via suitable connections (not shown). Strap substrate 254 is then placed on inlay 222 such that strap contacts 256 and 258 electrically couple to antenna segments 226 and 228. Strap substrate 254 may be affixed to inlay 222 via pressing, an interface layer, one or more adhesives, or any other suitable means.

[0039] Diagram 260 depicts a side view of an alternative way to place strap substrate 254 onto inlay 222. Instead of strap substrate 254’ s surface, including strap contacts 256/258, facing the surface of inlay 222, strap substrate 254 is placed with its strap contacts 256/258 facing away from the surface of inlay 222. Strap contacts 256/258 can then be either capacitively coupled to antenna segments 226/228 through strap substrate 254, or conductively coupled using a through-via which may be formed by crimping strap contacts 256/258 to antenna segments 226/228. In some examples, the positions of strap substrate 254 and inlay 222 may be reversed, with strap substrate 254 mounted beneath inlay 222 and strap contacts 256/258 electrically coupled to antenna segments 226/228 through inlay 222. Of course, in yet other examples strap contacts 256/258 may electrically couple to antenna segments 226/228 through both inlay 222 and strap substrate 254.

[0040] In operation, the antenna couples with RF signals in the environment and propagates the signals to IC 224, which may both harvest power and respond if appropriate, based on the incoming signals and the IC’s internal state. If IC 224 uses backscatter modulation then it may generate a response signal (e.g., signal 126) from an RF signal in the environment (e.g., signal 112) by modulating the antenna’s reflectance. Electrically coupling and uncoupling the IC contacts of IC 224 can modulate the antenna’s reflectance, as can varying the admittance or impedance of a shunt-connected or series-connected circuit element which is coupled to the IC contacts. If IC 224 is capable of transmitting signals (e.g., has its own power source, is coupled to an external power source, and/or can harvest sufficient power to transmit signals), then IC 224 may respond by transmitting response signal 126. In the examples of FIG. 2, antenna segments 226 and 228 are separate from IC 224. In other examples, the antenna segments may alternatively be formed on IC 224.

[0041] An RFID tag such as tag 220 is often attached to or associated with an individual item or the item packaging. An RFID tag may be fabricated and then attached to the item or packaging, may be partly fabricated before attachment to the item or packaging and then completely fabricated upon attachment to the item or packaging, or the manufacturing process of the item or packaging may include the fabrication of the RFID tag. In some examples, the RFID tag may be integrated into the item or packaging, and portions of the item or packaging may serve as tag components. For example, conductive item or packaging portions may serve as tag antenna segments or contacts. Nonconductive item or packaging portions may serve as tag substrates or inlays. If the item or packaging includes integrated circuits or other circuitry, some portion of the circuitry may be configured to operate as part or all of an RFID tag IC. Thus, an “RFID IC” need not be distinct from an item, but more generally refers to the item containing an RFID IC and antenna capable of interacting with RF waves and receiving and responding to RFID signals. Because the boundaries between IC, tag, and item are thus often blurred, the term “RFID IC”, “RFID tag IC”, or “RFID tag” as used herein may refer to the IC, the tag, or even to the item as long as the referenced element is capable of RFID functionality. [0042] 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, where both reader 110 and tag 120 can transmit at the same time. In some examples, RFID system 100 may be capable of full duplex communication. Another such mode, which may be more suitable for passive tags, is called half-duplex, and is described below.

[0043] FIG. 3 is a conceptual diagram 300 for explaining half-duplex communications between the components of the RFID system of FIG. 1, in this case with tag 120 implemented as a passive tag. 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.

[0044] In a half-duplex communication mode, RFID reader 110 and RFID tag 120 talk and listen to each other by taking turns. As seen on axis TIME, reader 110 talks to tag 120 during intervals designated “R- T”, and tag 120 talks to reader 110 during intervals designated “T- R”. For example, a sample R- T interval occurs during time interval 312, during which reader 110 talks (block 332) and tag 120 listens (block 342). A following sample T~>R interval occurs during time interval 326, during which reader 110 listens (block 336) and tag 120 listens (block 346). Interval 312 may be of a different duration than interval 326 - here the durations are shown approximately equal only for purposes of illustration.

[0045] During interval 312, reader 110 transmits a signal such as signal 112 described in FIG. 1 (block 352), while tag 120 receives the reader signal (block 362), processes the reader signal to extract data, and harvests power from the reader signal. While receiving the reader signal, tag 120 does not backscatter (block 372), and therefore reader 110 does not receive a signal from tag 120 (block 382).

[0046] During interval 326, also known as a backscatter time interval or backscatter interval, reader 110 does not transmit a data-bearing signal. Instead, reader 110 transmits a continuous wave (CW) signal (block 356), which is a carrier that generally does not encode information. The CW signal provides energy for tag 120 to harvest as well as a waveform that tag 120 can modulate to form a backscatter response signal. Accordingly, during interval 326 tag 120 is not receiving a signal with encoded information (block 366) and instead modulates the CW signal (block 376) to generate a backscatter signal such as signal 126 described in FIG. 2. Tag 120 may modulate the CW signal to generate a backscatter signal by adjusting its antenna reflectance, as described above. Reader 110 then receives and processes the backscatter signal (block 386).

[0047] FIG. 4 is a block diagram showing a detail of an RFID IC, such as IC 224 in FIG. 2. Electrical circuit 424 may be implemented in an IC, such as IC 224. Circuit 424 implements at least two IC contacts 432 and 433, suitable for coupling to antenna segments such as antenna segments 226/228 in FIG. 2. When two IC contacts form the signal input from and signal return to an antenna they are often referred-to as an antenna port. IC contacts 432 and 433 may be made in any suitable way, such as from electrically-conductive pads, bumps, or similar. In some examples circuit 424 implements more than two IC contacts, especially when configured with multiple antenna ports and/or to couple to multiple antennas.

[0048] Circuit 424 includes signal -routing section 435 which may include signal wiring, signal-routing buses, receive/transmit switches, and similar that can route signals between the components of circuit 424. IC contacts 432/433 may couple galvanically, capacitively, and/or inductively to signal -routing section 435. For example, optional capacitors 436 and/or 438 may capacitively couple IC contacts 432/433 to signal -routing section 435, thereby galvanically decoupling IC contacts 432/433 from signal -routing section 435 and other components of circuit 424.

[0049] Capacitive coupling (and the resultant galvanic decoupling) between IC contacts 432 and/or 433 and components of circuit 424 is desirable in certain situations. For example, in some RFID tag examples, IC contacts 432 and 433 may galvanically connect to terminals of a tuning loop on the tag. In these examples, galvanically decoupling IC contact 432 from IC contact 433 may prevent the formation of a DC short circuit between the IC contacts through the tuning loop.

[0050] Capacitors 436/438 may be implemented within circuit 424 and/or partly or completely external to circuit 424. For example, a dielectric or insulating layer on the surface of the IC containing circuit 424 may serve as the dielectric in capacitor 436 and/or capacitor 438. As another example, a dielectric or insulating layer on the surface of a tag substrate (e.g., inlay 222 or strap substrate 254) may serve as the dielectric in capacitors 436/438. Metallic or conductive layers positioned on both sides of the dielectric layer (i.e., between the dielectric layer and the IC and between the dielectric layer and the tag substrate) may then serve as terminals of the capacitors 436/438. The conductive layers may include IC contacts (e.g., IC contacts 432/433), antenna segments (e.g., antenna segments 226/228), or any other suitable conductive layers.

[0051] Circuit 424 includes a rectifier and PMU (Power Management Unit) 441 that harvests energy from the RF signal incident on antenna segments 226/228 to power the circuits of IC 424 during either or both reader-to-tag (R->T) and tag-to-reader (T- R) intervals. Rectifier and PMU 441 may be implemented in any way known in the art, and may include one or more components configured to convert an alternating-current (AC) or time-varying signal into a direct-current (DC) or substantially time-invariant signal.

[0052] Circuit 424 also includes a demodulator 442, a processing block 444, a memory 450, and a modulator 446. Demodulator 442 demodulates the RF signal received via IC contacts 432/433, and may be implemented in any suitable way, for example using a slicer, an amplifier, and other similar components. Processing block 444 receives the output from demodulator 442, performs operations such as command decoding, memory interfacing, and other related operations, and may generate an output signal for transmission. Processing block 444 may be implemented in any suitable way, for example by combinations of one or more of a processor, controller, processing circuitry, memory, decoder, encoder, and other similar components.

Memory 450 stores data 452, and may be at least partly implemented as permanent or semi -permanent memory such as nonvolatile memory (NVM), EEPROM, ROM, or other memory types configured to retain data 452 even when circuit 424 does not have power. Processing block 444 may be configured to read data from and/or write data to memory 450.

[0053] Modulator 446 generates a modulated signal from the output signal generated by processing block 444. For example, processing block 444 may cause modulator 446 to modulate data symbols onto a backscattered RF wave, as described above. In one example, modulator 446 generates the modulated signal by driving the load presented by antenna segment(s) coupled to IC contacts 432/433 to form a backscatter signal as described above. In another example, modulator 446 includes and/or uses a transmitter to generate and transmit the modulated signal via antenna segment(s) coupled to IC contacts 432/433. Modulator 446 may be implemented in any suitable way, for example using a switch, driver, amplifier, and other similar components. Demodulator 442 and modulator 446 may be separate components, combined in a single transceiver circuit, and/or part of processing block 444.

[0054] In some examples, particularly in those with more than one antenna port, circuit 424 may contain multiple demodulators, rectifiers, PMUs, modulators, processing blocks, and/or memories.

[0055] FIG. 5 A shows version 524-A of components of circuit 424 of FIG. 4, further modified to emphasize a signal operation during a R- T interval (e.g., time interval 312 of FIG. 3). During the R- T interval, demodulator 442 demodulates an RF signal received from IC contacts 432/433. The demodulated signal is provided to processing block 444 as C_IN, which in some examples may include a received stream of symbols. Rectifier and PMU 441 may be active, for example harvesting power from an incident RF waveform and providing power to demodulator 442, processing block 444, and other circuit components. During the R- T interval, modulator 446 is not actively modulating a signal, and in fact may be decoupled from the RF signal. For example, signal routing section 435 may be configured to decouple modulator 446 from the RF signal, or an impedance of modulator 446 may be adjusted to decouple it from the RF signal.

[0056] FIG. 5B shows version 524-B of components of circuit 424 of FIG. 4, further modified to emphasize a signal operation during a T->R interval (e.g., time interval 326 of FIG. 3). During the T~>R interval, processing block 444 outputs a signal C OUT, which may include a stream of symbols for transmission. Modulator 446 then generates a modulated signal from C OUT and sends the modulated signal via antenna segment(s) coupled to IC contacts 432/433, as described above. During the T- R interval, rectifier and PMU 441 may be active, while demodulator 442 may not be actively demodulating a signal. In some examples, demodulator 442 may be decoupled from the RF signal during the T~>R interval. For example, signal routing section 435 may be configured to decouple demodulator 442 from the RF signal, or an impedance of demodulator 442 may be adjusted to decouple it from the RF signal.

[0057] In typical examples, demodulator 442 and modulator 446 are operable to demodulate and modulate signals according to a protocol, such as the Gen2 Protocol mentioned above. In examples where circuit 424 includes multiple demodulators modulators, and/or processing blocks, each may be configured to support different protocols or different sets of protocols. A protocol specifies, in part, symbol encodings, and may include a set of modulations, rates, timings, or any other parameter associated with data communications. A protocol can be a variant of an internationally ratified protocol such as the Gen2 Protocol, for example including fewer or additional commands than the ratified protocol calls for, and so on. In some instances, additional commands may sometimes be called custom commands.

[0058] FIG. 6 is a block diagram depicting an RFID reader system 600 according to examples. Reader system 600 is configured to communicate with RFID tags and optionally to communicate with entities external to reader system 600, such as a service 632. Reader system 600 includes at least one reader module 602, configured to transmit signals to and receive signals from RFID tags. Reader system 600 further includes at least one local controller 612, and in some examples includes at least one remote controller 622. Controllers 612 and/or 622 are configured to control the operation of reader module 602, process data received from RFID tags communicating through reader module 602, communicate with external entities such as service 632, and otherwise control the operation of reader system 600.

[0059] In some examples, reader system 600 may include multiple reader modules, local controllers, and/or remote controllers. For example, reader system 600 may include at least one other reader module 610, at least one other local controller 620, and/or at least one other remote controller 630. A single reader module may communicate with multiple local and/or remote controllers, a single local controller may communicate with multiple reader modules and/or remote controllers, and a single remote controller may communicate with multiple reader modules and/or local controllers. Similarly, reader system 600 may be configured to communicate with multiple external entities, such as other reader systems (not depicted) and multiple services (for example, services 632 and 640).

[0060] Reader module 602 includes a modulator / encoder block 604, a demodulator / decoder block 606, and an interface block 608. Modulator / encoder block 604 may encode and modulate data for transmission to RFID tags. Demodulator / decoder block 606 may demodulate and decode signals received from RFID tags to recover data sent from the tags. The modulation, encoding, demodulation, and decoding may be performed according to a protocol or specification, such as the Gen2 Protocol. Reader module 602 may use interface block 608 to communicate with local controller 612 and/or remote controller 624, for example to exchange tag data, receive instructions or commands, or to exchange other relevant information.

[0061] Reader module 602 and blocks 604/606 are coupled to one or more antennas and/or antenna drivers (not depicted), for transmitting and receiving RF signals. In some examples, reader module 602 is coupled to multiple antennas and/or antenna drivers. In these examples, reader module 602 may transmit and/or receive RF signals on the different antennas in any suitable scheme. For example, reader module 602 may switch between different antennas to transmit and receive RF signals, transmit on one antenna but receive on another antenna, or transmit and/or receive on multiple antennas simultaneously. In some examples, reader module 602 may be coupled to one or more phased-array or synthesized-beam antennas whose beams can be generated and/or steered, for example by reader module 602, local controller 612, and/or remote controller 622.

[0062] Modulator / encoder block 604 and/or demodulator / decoder block 606 may be configured to perform conversion between analog and digital signals. For example, modulator / encoder block 604 may convert a digital signal received via interface block 608 to an analog signal for subsequent transmission, and demodulator / decoder block 606 may convert a received analog signal to a digital signal for transmission via interface block 608.

[0063] Local controller 612 includes a processor block 612, a memory 616, and an interface 618. Remote controller 622 includes a processor block 622, a memory 626, and an interface 628. Local controller 612 differs from remote controller 622 in that local controller 612 is collocated or at least physically near reader module 602, whereas remote controller 622 is not physically near reader module 602. For example, local

[0064] Processor blocks 612 and/or 622 may be configured to, alone or in combination, provide different functions. Such functions may include the control of other components, such as memory, interface blocks, reader modules, and similar; communication with other components such as reader module 602, other reader systems, services 632/640, and similar; data-processing or algorithmic processing such as encryption, decryption, authentication, and similar; or any other suitable function. In some examples, processor blocks 612/622 may be configured to convert analog signals to digital signals or vice-versa, as described above in relation to blocks 604/606; processor blocks 612/622 may also be configured to perform any suitable analog signal processing or digital signal processing, such as filtering, carrier cancellation, noise determination, and similar.

[0065] Processor blocks 612/622 may be configured to provide functions by execution of instructions or applications, which may be retrieved from memory (for example, memory 616 and/or 626) or received from some other entity. Processor blocks 612/622 may be implemented in any suitable way. For example, processor blocks 612/622 may be implemented using 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 equivalents.

[0066] Memories 616/626 are configured to store information, and may be implemented in any suitable way, such as the memory types described above, any combination thereof, or any other known memory or information storage technology. Memories 616/626 may be implemented as part of their associated processor blocks (e.g., processor blocks 614/624) or separately. Memories 616/626 may store instructions, programs, or applications for processor blocks 614/624 to execute. Memories 616/626 may also store other data, such as files, media, component configurations or settings, etc.

[0067] In some examples, memories 616/626 store tag data. Tag data may be data read from tags, data to be written to tags, and/or data associated with tags or tagged items. Tag data may include identifiers for tags such as electronic product codes (EPCs), tag identifiers (TIDs), or any other information suitable for identifying individual tags. Tag data may also include tag passwords, tag profiles, tag cryptographic keys (secret or public), tag key generation algorithms, and any other suitable information about tags or items associated with tags. [0068] Memories 616/626 may also store information about how reader system 600 is to operate. For example, memories 616/626 may store information about algorithms for encoding commands for tags, algorithms for decoding signals from tags, communication and antenna operating modes, encryption / authentication algorithms, tag location and tracking algorithms, cryptographic keys and key pairs (such as public/private key pairs) associated with reader system 600 and/or other entities, electronic signatures, and similar.

[0069] Interface blocks 608, 618, and 628 are configured to communicate with each other and with other suitably configured interfaces. The communications between interface blocks occur via the exchange of signals containing data, instructions, commands, or any other suitable information. For example, interface block 608 may receive data to be written to tags, information about the operation of reader module 602 and its constituent components, and similar; and may send data read from tags. Interface blocks 618 and 628 may send and receive tag data, information about the operation of other components, other information for enabling local controller 612 and remote controller 622 to operate in conjunction, and similar. Interface blocks 608/618/628 may also communicate with external entities, such as services 632, 640, other services, and/or other reader systems.

[0070] Interface blocks 608/618/628 may communicate using any suitable wired or wireless means. For example, interface blocks 608/618/628 may communicate over circuit traces or interconnects, or other physical wires or cables, and/or using any suitable wireless signal propagation technique. In some examples, interface blocks 608/618/628 may communicate via an electronic communications network, such as a local area network (LAN), a metropolitan area network (MAN), a wide area network (WAN), a network of networks such as the internet. Communications from interface blocks 608/618/628 may be secured, for example via encryption and other electronic means, or may be unsecured.

[0071] Reader system 600 may be implemented in any suitable way. One or more of the components in reader system 600 may be implemented as integrated circuits using CMOS technology, BJT technology, MESFET technology, and/or any other suitable physical implementation technology. Components may also be implemented as software executing on general -purpose or application-specific hardware. [0072] In one example, a “reader” as used in this disclosure may include at least one reader module like reader module 602 and at least one local controller such as local controller 612. Such a reader may or may not include any remote controllers such as remote controller 622. A reader including a reader module and a local controller may be implemented as a standalone device or as a component in another device. In some examples, a reader may be implemented as a mobile device, such as a handheld reader, or as a component in a mobile device such as a laptop, tablet, smartphone, wearable device, or any other suitable mobile device.

[0073] Remote controller 622, if not included in a reader, may be implemented separately. For example, remote controller 622 may be implemented as a local host, a remote server, or a database, coupled to one or more readers via one or more communications networks. In some examples, remote controller 622 may be implemented as an application executing on a cloud or at a datacenter.

[0074] Functionality within reader system 600 may be distributed in any suitable way. For example, the encoding and/or decoding functionalities of blocks 604 and 606 may be performed by processor blocks 614 and/or 624. In some examples, processor blocks 614 and 624 may cooperate to execute an application or perform some functionality. One of local controller 612 and remote controller 622 may not implement memory, with the other controller providing memory.

[0075] Reader system 600 may communicate with at least one service 632. Service 632 provides one or more features, functions, and/or capabilities associated with one or more entities, such as reader systems, tags, tagged items, and similar. Such features, functions, and/or capabilities may include the provision of information associated with the entity, such as warranty information, repair/replacement information, upgrade/update information, and similar; and the provision of services associated with the entity, such as storage and/or access of entity -related data, location tracking for the entity, entity security services (e.g., authentication of the entity), entity privacy services (e.g., who is allowed access to what information about the entity), and similar. Service 632 may be separate from reader system 600, and the two may communicate via one or more networks.

[0076] In some examples, an RFID reader or reader system implements the functions and features described above at least partly in the form of firmware, software, or a combination, such as hardware or device drivers, an operating system, applications, and the like. In some examples, interfaces to the various firmware and/or software components may be provided. Such interfaces may include application programming interfaces (APIs), libraries, user interfaces (graphical and otherwise), or any other suitable interface. The firmware, software, and/or interfaces may be implemented via one or more processor blocks, such as processor blocks 614/624. In some examples, at least some of the reader or reader system functions and features can be provided as a service, for example, via service 632 or service 640.

[0077] RFID techniques may entail using an RFID reader to inventory one or more tags by successively singulating individual tags and receiving backscattered identifiers from the singulated tags. RFID systems typically schedule or queue tag responses using anticollision algorithms to avoid multiple tags backscattering at the same time (known as a “collision”). These anticollision algorithms may include slotted-Aloha, random timeslotting, and other scheduling algorithms known to those skilled in the art. For example, the Gen2 Protocol uses a slotted-Aloha scheduling algorithm, in which individual RFID tags each generate a pseudorandom number to determine an appropriate time to respond.

[0078] FIG. 7 is a diagram depicting query-acknowledgement interactions between an RFID reader system and multiple RFID tags during an inventory round.

[0079] As shown in FIG. 7, at time 700 an RFID reader system 702 may transmit a query command to RFID tags 704, 706, and 708 during an inventory round. The query command instructs tags that meet certain criteria to participate or continue to participate in an inventory round by replying at an appropriate time with collisionresolution codes (CR codes). A collision-resolution code is a code that an RFID reader system can use to indicate or specify a particular RFID tag during an inventory round, in situations when multiple RFID tags may reply at around the same time. A collision-resolution code may be an identifier for an RFID tag or an item associated with an RFID tag, or a portion of such an identifier. Such an identifier may be a permanent identifier, described in more detail below. In some embodiments, the CR code may be a temporary identifier, such as a random or pseudorandom number, an example of which is a 16-bit number or “RN16”, as described in the Gen2 Protocol. In some embodiments, the query command may be a Query, Query Adj, or Query Rep command as described in the Gen2 Protocol. [0080] Tags that receive the query command may then each independently select a particular time to reply with CR codes. For example, a tag operating according to the Gen2 Protocol may generate a pseudorandom number to determine when it should respond. In some instances, two or more tags may end up replying at the same time. For example, RFID tags 704, 706, and 708 may reply with CR codes CR-1, CR-2, and CR-3, respectively, at around the same time. This may result in a “collided reply” or “collision” 710.

[0081] If reader system 702 is suitably configured, it may be able to recover two or more of CR-1, CR-2, and CR-3 from the collision 710, for example using error correction, source separation, or other suitable techniques. For example, one or more of the techniques described in commonly owned U.S. Pat. Nos. 9,715,605, 9,881,186, and 10,037,444 (hereby incorporated by reference in their entireties) may be used to recover multiple codes from a collision. However, even if reader system 702 can recover multiple replies from a collision, it may not be able to further interact with all three of the RFID tags 704, 706, and 708. For example, the Gen2 Protocol specifies that an RFID reader further interacts with an RFID tag that has replied with a collision-resolving RN16 by sending an acknowledgement (“ACK”) command including the RN16, thereby causing the tag to transition from a “Reply” state to an “Acknowledged” state. If an RFID tag receives an ACK command including an RN16 matching the one it provided, then it transitions to the Acknowledged state and continues to interact with the RFID reader. On the other hand, if the RFID tag receives an ACK command including a nonmatching RN16 (i.e., an RN16 it did not provide), then the Gen2 Protocol requires that the tag effectively exits the current inventory round by transitioning to an “Arbitrate” state. If the CR codes in the diagram for time 700 are RN16s, then at time 720 the reader system 702 can send an ACK command with CR-1, CR-2, or CR-3. If reader system 702 sends an ACK command with CR-1, then tag 704 will continue to interact with reader system 702, but tags 706 and 708 will effectively exit the inventory round. Similarly, if reader system 702 sends an ACK command with CR-2, then tag 706 will continue to interact with reader system 702, but tags 704 and 708 will effectively exit the inventory round.

[0082] In some embodiments, RFID tags can be configured such that if a tag detects a nonmatching acknowledgement command (e.g., an ACK command with a nonmatching RN16), instead of exiting the inventory round (e.g., transitioning to the Arbitrate state) the tag will wait in its current state (Reply or Acknowledged). In this case, the tag may be referred to as being in a “wait” mode of its current state, as opposed to a “go” mode in which the tag exits the inventory round or transitions to a different state as described by the Gen2 Protocol. A suitably configured RFID tag may implement wait and go modes for the Reply state, the Acknowledged state, or any other suitable operating state. The wait modes may also be referred to as a “reply wait” mode or an “acknowledged wait” mode, depending on whether the tag is waiting in the Reply or Acknowledged state.

[0083] FIG. 8 is a diagram depicting query-acknowledgement interactions between an RFID reader and multiple RFID tags enabled to wait in their current states during an inventory round, according to examples.

[0084] At time 800, an RFID reader system 802 may transmit a query command to RFID tags 804 and 806 during an inventory round. In this instance, tags 804 and 806 end up replying at the same time, and both tags 804 and 806 reply with CR-1 and CR- 2, respectively, at around the same time, resulting in collision 810. Reader system 802 is suitably configured to and therefore does recover both CR-1 and CR-2 from collision 810. Tags 804 and 806 are both now operating in the wait mode of the Reply state (“reply wait mode” 812).

[0085] At time 820, the RFID reader system 802 acknowledges tag 804 by sending its CR-1, for example in an ACK command. Tag 804 then responds with, for example, an identifier ID-1, and subsequently transitions from the wait mode of the Reply state to the wait mode of the Acknowledged state (“acknowledged wait mode” 822). Tag 806 also detects the acknowledgement with CR-1. Upon determining that the CR-1 is not what it sent, tag 806 remains or waits in the Reply state (“reply wait mode” 812), as opposed to transitioning to the Arbitrate state as described above in relation to FIG. 7. This allows tag 806 to remain available for acknowledgement by the RFID reader system 802.

[0086] Subsequently at time 840 the RFID reader system 802 acknowledges tag 806 by sending CR-2, for example in another ACK command. Tag 806 then responds with, for example, an identifier ID-2, and subsequently transitions from the wait mode of the Reply state to the wait mode of the Acknowledged state (“acknowledged wait mode” 822). Tag 804 also detects the acknowledgement with CR-2. Upon determining that CR-2 is not its collision-resolution code, tag 804 remains or waits in the Acknowledged state (“acknowledged wait mode” 822), as opposed to transitioning back to the Arbitrate state according to the Gen2 Protocol.

[0087] At this point, tags 804 and 806 are both in the wait mode of the Acknowledged state (“acknowledged wait mode” 822), and can be further accessed by the reader system 802.

[0088] While FIG. 8 only explicitly describes two individual tags, implementations involving three or more suitably configured tags are possible and within the scope of this disclosure.

[0089] In situations where an RFID reader system can recover two or more replies from a collided reply, the RFID reader system may also be configured to acknowledge multiple tags at once. This acknowledgement, which may be referred to as a “multiacknowledgement”, may cause the multiple tags to respond at around the same time, resulting in a subsequent collided reply. The reader system may then be able to resolve two or more subsequent tag responses from the subsequent collided reply.

[0090] FIG. 9 is a diagram depicting query-acknowledgement interactions between an RFID reader system and multiple RFID tags, where the RFID reader is configured to acknowledge multiple, specified RFID tags, according to examples.

[0091] At time 900, an RFID reader system 902 may transmit a query command to RFID tags 904, 906, and 908 during an inventory round. In this instance, tags 904, 906, and 908 up end replying at the same time, resulting in collision 910. When replying, tags 904, 906 and 908 reply with CR codes CR-1, CR-2, and CR-3, respectively. RFID reader system 902 successfully recovers all the CR codes from the collision 910.

[0092] At time 920, the RFID reader system 902 acknowledges tags 904 and 906 by sending at least portions of their CR codes, denoted as CR-1* and CR-2*, respectively. The RFID reader system 902 may send the CR code portions in an acknowledgement (ACK) command, as depicted in diagram 900. In some examples, the CR code portions are as named and only include portions of the CR codes (e.g., CR-1* may only include part of CR-1), while in other examples the CR code portions may include the entire CR codes (e.g., CR-1* may include the entirety of CR-1). The former reduces the amount of information included in the acknowledgement, whereas the latter may reduce the ambiguity of the tags being acknowledged. In some situations, a balance may be struck between the two options - for example, the CR code portions may be the portions of the CR codes that are most likely to differ between tags. This does mean that the CR code portions included in the ACK command will usually differ from each other, although this is not strictly necessary.

[0093] RFID tags 904 and 906, upon determining that the RFID reader system 902 has acknowledged them (using at least portions of their respective CR codes), respond with their respective permanent identifiers ID-1 and ID-2. An RFID tag’s permanent identifier is an identifier known to, encoded on, or stored on the tag that is intended to be permanent. The permanent identifier may identify the tag or an item associated with the tag. In some examples, permanent identifiers may include a tag identifier (TID), an electronic product code (EPC), a unique item identifier (UID), and/or versions of any of the foregoing. At time 920, RFID tag 908, upon determining that the RFID reader system 902 did not acknowledge it, does not respond with its permanent identifier.

[0094] In some situations, such as when operating strictly according to the Gen2 Protocol, after time 920 RFID tag 908 would exit the inventory round, for example by transitioning to the Arbitrate state, because it detected a nonmatching acknowledgement (e.g., an acknowledgement command with a nonmatching CR code). However, in some embodiments RFID tags can be modified as described above in relation to FIG. 8 such that if a tag detects a nonmatching acknowledgement, instead of exiting the inventory round (e.g., transitioning to the Arbitrate state) the tag will wait in a wait mode. In the example depicted in diagram 900, RFID tag 908 is in fact configured with wait modes, and upon detecting the nonmatching acknowledgement it enters or remains in a reply wait mode 922 (i.e., the wait mode of the Reply state). In fact, RFID tag 908 may have entered the reply wait mode 922 after sending CR code CR-3 at time 900.

[0095] When RFID tags 904 and 906 respond with ID-1 and ID-2 at time 920, a collision 924 may occur. As with collision 910, reader system 902 may successfully recover both ID-1 and ID-2 from collision 924. Being able to recover two or more tag responses from a collision allows reader-tag interactions to be sped up and streamlined. [0096] At time 940, the RFID reader system 902 acknowledges RFID tag 908 by sending at least portions of its CR code, denoted CR-3*. In response, RFID tag 908 responds with its permanent identifier ID-3, and transitions to an Acknowledged state.

[0097] In some situations, the nonmatching acknowledgement at time 940 may cause RFID tags 904 and 906 to exit the inventory round, for example by transitioning to the Arbitrate state. However, RFID tags 904 and 906 may be modified such that if they detect nonmatching acknowledgements, instead of exiting the inventory round they will wait in their current state (in this case, the Acknowledged state). So, at time 940, instead of exiting the inventory round upon detected the nonmatching acknowledgement RFID tags 904 and 906 enter or remain in an acknowledged wait mode 942 (i.e., the wait mode of the Acknowledged state). In fact, RFID tags 904 and 906 may have entered the acknowledged wait mode 942 after sending their identifiers at time 920.

[0098] After time 940, all three RFID tags 904, 906, and 908 are in the Acknowledged states, and RFID reader system 902 may further interact with one or none of them.

[0099] In the example process of FIG. 9, the RFID reader system 902 first acknowledges RFID tags 904 and 906, then acknowledges RFID tag 908. In order to do so and retain the ability to further access one of those tags, the RFID tags may implement reply and acknowledged wait modes. In some examples, the RFID reader system 902 may base its usage of tag wait modes on whether replying RFID tags implement wait modes. The RFID reader system 902 may determine whether replying RFID tags implement wait modes based on, for example, received CR codes.

[0100] While the RFID reader system 902 in FIG. 9 first acknowledges RFID tags 904 and 906 (by sending CR-1* and CR-2* in an acknowledgement command), then acknowledges RFID tag 908 (by sending CR-3* in another acknowledgement command), the RFID reader system 902 may also be able to acknowledge all three RFID tags at once, by sending CR-1*, CR-2*, and CR-3* in the same acknowledgement command. In another example, an RFID reader system could acknowledge all replying RFID tags at once, without having to specify individual CR codes. [0101] FIG. 10 is a diagram depicting query-acknowledgement interactions between an RFID reader system and multiple RFID tags, where the RFID reader is configured to acknowledge all responding RFID tags, according to examples.

[0102] At time 1000, an RFID reader system 1002 may transmit a query command to RFID tags 1004, 1006, and 1008 during an inventory round. In this instance, tags 1004, 1006, and 1008 all end up replying at the same time, resulting in a collision 1010. When replying, tags 1004, 1006, and 1008 reply with CR codes CR-1, CR-2, and CR-3, respectively. The RFID reader system 1002 successfully recovers all the CR codes from the collision 1010.

[0103] At time 1020, the RFID reader system 1002 acknowledges all the replying tags by sending a special acknowledgement code (shown as “ALL”), for example in an acknowledgement command as depicted in diagram 1000. An RFID tag may be configured to treat an acknowledgement command as matching if it either includes (a) at least a portion of a CR code previously provided by the RFID tag or (b) a special acknowledgement code. In diagram 1000, RFID tags 1004, 1006, and 1008 are configured in this way, and therefore treat the acknowledgement command with the special acknowledgement code as matching. In response, all three tags reply with their permanent identifiers (or portions thereof) ID-1, ID-2, and ID-3, respectively. This may result in a collision 1022, from which the RFID reader system 1002 may be able to recover one of more of ID-1, ID-2, and ID-3.

[0104] Depending on its length, using a special acknowledgement code in an acknowledgement command instead of individual CR codes to acknowledge all responding tags may speed up the inventory process, with speed benefits increasing as the number of individual tags increase.

[0105] In some examples, a special acknowledgement code in an acknowledgement may take the place of the CR codes that would otherwise be in a multiacknowledgement. In other examples, the multi -acknowledgement may include a parameter that indicates whether it is directed to all replying tags or only to tags specified with CR codes.

[0106] In general, an RFID reader system may expect to recover a certain number of permanent identifiers, based on the number of CR codes it has successfully recovered. For example, if an RFID reader system recovers two CR codes from a collision, it may expect to recover two permanent identifiers in response to a subsequent acknowledgement. However, in certain circumstances the number of recovered CR codes may not match the number of recovered permanent identifiers. For example, an RFID reader system may simply fail to recover a CR code from a collision, but subsequently successfully recover a corresponding permanent identifier. In another example, an RFID reader system may successfully recover all CR codes but subsequently fail to recover one or more permanent identifiers.

[0107] FIG. 11 illustrates the former example. FIG. 11 is a diagram depicting queryacknowledgement interactions between an RFID reader system and multiple RFID tags, where the RFID reader is configured to initially acknowledge all responding RFID tags, according to examples.

[0108] At time 1100, an RFID reader system 1102 may transmit a query command to RFID tags 1104, 1106, and 1108 during an inventory round. In this instance, tags 1104, 1106, and 1108 select the same time to reply, resulting in a collision 1110. When replying, tags 1104, 1106, and 1108 reply with CR codes CR-1, CR-2, and CR- 3, respectively. The RFID reader system 1102 successfully recovers at least CR-1 and CR-2 from the collision 1110, but may not successfully recover CR-3.

[0109] At time 1120, the RFID reader system 1102 acknowledges all the replying tags by sending a special acknowledgement code (shown as “ALL”), for example in an acknowledgement command as depicted in diagram 1100. This is somewhat similar to the situation depicted at time 1020 in FIG. 10, except that the RFID reader system 1102 may not have successfully recovered CR codes from all replying RFID tags.

[0110] In response to the acknowledgement, RFID tags 1104, 1106, and 1108 reply with their permanent identifiers (or portions thereof) ID-1, ID-2, and ID-3, respectively. This may result in a collision 1122.

[OHl] The RFID reader system 1102, upon recovering one or more identifiers (or identifier portions) from the collision 1122, may determine that at least one unexpected RFID tag has replied. An RFID tag may be unexpected if a reader system has not previously received a CR code from the tag.

[0112] In response to detecting an unexpected RFID tag reply, at time 1140 RFID reader system 1102 sends a second acknowledgement command, this time specifying the RFID tags whose CR codes were successfully recovered. Specifically, the second acknowledgement command includes at least portions of CR-1 and CR-2 (denoted as CR-1* and CR-2*, respectively).

[0113] RFID tags 1104 and 1106, upon determining that the RFID reader system 1102 has specifically acknowledged them, respond again with their respective permanent identifiers ID-1 and ID-2. RFID tag 1108, upon detecting a nonmatching acknowledgement, may transition to acknowledged wait mode 1142, similar to acknowledged wait mode 842 in FIG. 8. In some examples, RFID tag 1108 may instead exit the inventory round.

[0114] When an RFID tag is in a reply wait mode, an acknowledgement command specifying the tag may cause it to exit the reply wait mode and enter, e.g., an acknowledged wait mode. The RFID tag may also exit the reply wait mode upon receiving a query command or upon losing power.

[0115] When an RFID tag is in an acknowledged wait mode, an access command specifying the tag may cause it to exit the acknowledged wait mode. Access commands may be configured to access additional features or functionalities of the RFID tag. Some example Gen2 access commands include Req RN, Read, and Write, as well as other access commands described in the Gen2 Protocol. The RFID tag may also exit the acknowledged wait mode upon receiving a query command or upon losing power.

[0116] In some examples, tags enabled with wait modes as described above may also be configured to exceed, disregard, or disable wait times (also known as “timeouts”) specified in their relevant communications protocols (e.g., the Gen2 Protocol). As one specific example, the Gen2 Protocol specifies a T2 timeout for the Reply or the Acknowledged state. If a tag in the Reply or Acknowledged state does not receive an appropriate command before the T2 timeout expires, then the tag transitions to the Arbitrate state. Tags configured with wait modes as described above may be configured to wait beyond timeouts such as the T2 timeout in certain circumstances, to allow a reader to communicate with multiple, collided tags. The extent to which such tags will wait beyond a timeout may be built into the tag or indicated by a reader, for example in the form of one or more command parameters. In some embodiments, such tags may be configured to wait indefinitely, until power loss or until receiving a command that causes the tags to stop waiting.

[0117] Tags with the wait modes described above may further be configured to enable or disable their wait modes. For example, a suitably configured tag may enable or disable using wait modes upon receiving a custom command, a proprietary command, a standard protocol command with custom fields, and/or any other suitable command. In some embodiments, such commands could include a query command, an acknowledgement command, or a broadcast command intended for multiple tags but not requesting replies from those tags (e.g., a selection command like the Select command described in the Gen2 Protocol). In other embodiments, a tag may always enable wait modes, or enable or disable wait modes based on some internal determination.

[0118] In one specific embodiment, a Query command according to the Gen2 Protocol may be used to cause receiving tags to enable or disable wait modes. Specifically, the Query command includes a 2 -bit “Sei” field whose value chooses which RFID tags respond to the Query. An Sei value of “11” chooses all RFID tags with SL flag values of “1” to respond, an Sei value of “10” chooses all RFID tags with SL flag values of “0” to respond, and an Sei value of “00” or “01” chooses all RFID tags, irrespective of SL flag values, to respond. In one embodiment, either the Sei value of “00” or “01” can be used to cause receiving tags to enable or disable wait modes. However, in other embodiments any suitable field value of any suitable command may be used to enable or disable wait modes.

[0119] When suitably configured tags have wait modes enabled, they may enter the corresponding wait mode when transitioning to different states. For example, a suitably configured tag may transition to the Reply state and enter a wait mode for the Reply state (“reply wait mode”) upon replying to a query command. Similarly, a suitably configured tag may transition to the Acknowledged state and enter a wait mode for the Acknowledged state (“acknowledge wait mode”) upon receiving an acknowledgement command. In some embodiments, a tag may have wait modes enabled for some states but not other states. [0120] While the examples above with respect to FIGS. 9-11 only explicitly describe three individual tags, implementations involving four or more suitably configured tags are possible and within the scope of this disclosure.

[0121] The example processes in FIGS. 8-11 may vary in different situations. In some situations, RFID tags may refrain from replying with their permanent identifiers upon matching acknowledgements. For example, if an RFID tag replies to a query with a CR code that includes a portion or all of its permanent identifier, then the RFID tag may subsequently refrain from sending its permanent identifier, thereby reducing the transmission of duplicative or redundant information. In the specific situation where a tag’s CR code includes only a portion of its permanent identifier, the tag may then be configured to subsequently send another portion of its permanent identifier, for example in response to a matching acknowledgement. If a tag does not reply with its permanent identifier upon receiving a matching acknowledgement, it may nevertheless transition to an acknowledged or acknowledged wait mode.

[0122] Similarly, in some situations an RFID tag may reply to a matching acknowledgement with only part of its permanent identifier. This may occur if the RFID tag had previously provided a portion of its permanent identifier (as described above), if a reader system had instructed the RFID tag to do so, or based on any other suitable criteria. In this document, “permanent identifier” and “permanent identifier portion” should be treated as interchangeable.

[0123] The functionalities described above of RFID tags refraining from providing duplicative or redundant portions of permanent identifiers are independent from wait modes and/or multi-acknowledgements. In other words, an RFID tag may refrain from replying with duplicative or redundant portions of its permanent identifier regardless of whether wait modes and/or multi -acknowledgements are used.

[0124] FIG. 12 depicts a flowchart of a method 1200 for an RFID reader to interact with tags modified with wait modes, according to examples.

[0125] An RFID reader may begin at optional step 1202 by enabling the wait modes described above in certain tags. For example, the reader may transmit a custom, proprietary, or standard protocol command with special field values, a query, acknowledgement, or broadcast command, or other suitable command that cause receiving and suitably configured tags to enable wait modes. [0126] At step 1204, the RFID reader may transmit an inventorying command requesting that tags that match certain criteria participate or continue to participate in an inventory round. The command may be a singulation or query command. The query command may be a Query, Query Adj, or Query Rep command as described in the Gen2 Protocol, and an RFID tag receiving the command may respond with a CR code, as described above.

[0127] At step 1206, multiple RFID tags reply with CR codes, and the RFID reader receives these replies at around the same time, resulting in collided replies. The RFID reader may employ error correction or other techniques to recover the replies at step 1208. The recovered replies may include tag-specific CR codes.

[0128] At step 1210, the RFID reader may transmit a tag-specific acknowledgement (ACK) command associated with one of the recovered CR codes. RFID tags that receive this tag-specific ACK command may determine whether the ACK command includes their respective CR codes. If an RFID tag determines that the ACK command includes the CR code it replied with, then the RFID tag will respond. For example, the RFID tag may respond with the same CR code or a different code or identifier. Upon responding, the RFID tag may transition to a different state (e.g., the Acknowledged state), and in some situations may wait there (e.g., in a wait mode of the Acknowledged state or an acknowledged wait mode), as described above. On the other hand, if an RFID tag determines that the ACK command does not include the CR code it replied with, then the RFID tag may wait in its current state, for example in a wait mode of the Reply state or a reply wait mode.

[0129] At step 1212, the RFID reader receives a response from the RFID tag whose CR code was included in the previously transmitted ACK command. At step 1214, the RFID reader attempts to interact with one of the other RFID tags that replied at step 1206, by transmitting a second ACK command associated with another one of the CR codes recovered in step 1208. The RFID tags that replied at step 1206 but determined that the previously transmitted ACK command did not include their respective CR codes may be in the reply wait mode, and upon receiving the second ACK command will determine whether the second ACK command includes their respective CR codes. One of those RFID tags may determine that the second ACK command includes its CR code, and that RFID tag may respond, similar to the RFID tag that responded at step 1210. The other RFID tags will continue to wait in their current states. In particular, the RFID tag that responded at step 1210 and may now be in a different state (e.g., the Acknowledged state) will also wait in its current state, so as to remain available for further interactions with the RFID reader.

[0130] The RFID reader then returns to step 1212, receiving the response to the second ACK command, and continues transitioning between steps 1212 and 1214 until all the RFID tags that replied at step 1206 have been acknowledged (i.e., received an ACK command including their respective CR code) or the RFID reader determines that no additional tags should be acknowledged. Subsequently, the RFID reader may further interact with one of the tags, for example by sending an access command such as those described in the Gen2 Protocol. Upon detecting such a command, the other tags may exit their various wait modes.

[0131] FIG. 13 depicts a flowchart of a method 1300 for an RFID reader system to recover multiple RFID tag responses, according to examples.

[0132] An RFID reader system may begin at optional step 1302 by enabling the multi-response functionality described above in certain tags. For example, the reader system may transmit a custom, proprietary, or standard protocol command with special field values, a query, acknowledgement, or broadcast command, or other suitable command that cause receiving and suitably configured tags to enable relevant functionality. Such functionality could include, for example, recognition of acknowledgements containing multiple CR codes, multiple CR code portions, and/or special acknowledgement codes. Such functionality may also include wait modes as described above.

[0133] At step 1304, the RFID reader system may transmit an inventorying command requesting that tags that match certain criteria participate or continue to participate in an inventory round. The command may be a singulation or query command. For example, the query command may be a Query, Query Adj, or Query Rep command as described in the Gen2 Protocol. An RFID tag receiving the command may respond with a CR code, as described above.

[0134] At step 1306, multiple RFID tags reply with CR codes, and the RFID reader system receives these replies at around the same time, resulting in collided replies. The RFID reader system may employ error correction or other techniques to recover CR codes from the replies at step 1308. [0135] At step 1310, the RFID reader system may transmit an acknowledgement associated with multiple recovered CR codes. For example, the acknowledgement may be an ACK command as described in the Gen2 Protocol. The acknowledgement may include specific CR codes / code portions, or a special acknowledgement code. An RFID tag that receives this acknowledgement may determine whether the acknowledgement is applicable. For example, an RFID tag may determine that a received acknowledgement is applicable if the acknowledgement includes (a) a CR code or code portion that the tag previously sent, or (b) a special acknowledgement code, as described above. If an RFID tag determines that the acknowledgement is applicable, then the RFID tag may respond. For example, the RFID tag may respond with its permanent identifier or a portion of its permanent identifier. In some examples, as described above, an RFID tag may not respond to an applicable acknowledgement with its permanent identifier. Whether or not the RFID tag responds, the RFID tag may transition to a different state after receiving an applicable acknowledgement. In some examples, the RFID tag may transition to the Acknowledged state, and further enter the wait mode of the Acknowledged state as described above. If an RFID tag determines that the acknowledgement is not applicable, then the RFID tag may wait in its current state, for example in a wait mode of the Reply state described above. In some examples, the RFID tag may instead exit the inventory round upon determining that a received acknowledgement is not applicable.

[0136] At step 1312, the RFID reader system receives collided responses from multiple RFID tags specified in the previously transmitted acknowledgement. At step 1314, the RFID reader may attempt to interact with one or more of the RFID tags that replied at step 1306 or 1312 by transmitting a refined acknowledgement. For example, if the RFID reader was unable to recover one or more responses from the collided responses received at step 1312, the RFID reader may transmit an acknowledgement at step 1314 that specifies the same RFID tags as the acknowledgement at step 1310 or specifies fewer tags. As another example, if the RFID reader transmitted a special acknowledgement code at step 1310 but received more tag replies than expected at step 1312, then the RFID reader may transmit an acknowledgement at step 1314 that specifies only the expected tags. Then, the RFID reader may return to step 1312 to receive responses to the acknowledgement transmitted at step 1314. The RFID reader may then continue transitioning between steps 1312 and 1314 until the RFID reader determines that no more acknowledgements need to be transmitted. For example, the RFID reader may determine that all tags that replied in step 1306 have been acknowledged, or no additional tags should be acknowledged.

[0137] In some examples, the RFID tags are configured with wait modes. In these examples, the RFID tags that replied at step 1306 but determined that the acknowledgement transmitted at step 1310 specified them may transmit the replies received at step 1312 and enter the wait mode associated with the Acknowledged state, so as to remain available for further interactions with the reader. Any RFID tags that replied at step 1306 but determined that the acknowledgement transmitted at step 1310 did not specify them may remain in the wait mode of the Reply state. Upon receiving any acknowledgement transmitted at step 1314, these tags in the may determine whether the received acknowledgement specifies them. If so, then the tags will reply and enter the wait mode of the Acknowledged state. Otherwise, they may remain in the wait mode of the Reply state. After the RFID reader has determined that no more acknowledgements need to be transmitted, it may further interact with one of the tags, for example by sending an access command such as those described in the Gen2 Protocol. Upon detecting such a command, the other tags may exit their various wait modes.

[0138] According to some examples, a Radio Frequency Identification (RFID) reader system includes a transceiver configured to transmit commands to and receive replies from RFID tags; and a processing block coupled to the transceiver. The processing block is configured to cause the transceiver to transmit a query command; receive, via the transceiver, collided replies to the query command from a first RFID tag and a second RFID tag; recover, from the collided replies to the query command, a first reply from the first RFID tag and a second reply from the second RFID tag; cause the transceiver to transmit a first multi-acknowledgement acknowledging both the first and second RFID tags; and receive, via the transceiver, collided replies to the first acknowledgement.

[0139] According to other examples, the first reply includes a first collisionresolution (CR) code; the second reply includes a second CR code; and the first multiacknowledgement includes at least a portion of the first CR code and at least a portion of the second CR code. The first CR code includes a 16-bit pseudorandom number. The first multi-acknowledgement includes a special acknowledgement code applicable to both the first RFID tag and the second RFID tag. The processing block is further configured to determine that the collided replies to the first multiacknowledgement potentially includes a reply from a third RFID tag; and in response, cause the transceiver to transmit a second multi -acknowledgement acknowledging the first and second RFID tags but not the third RFID tag.

[0140] According to further examples, the processing block is configured to recover the first reply and the second reply using an error detection technique. The processing block is further configured to cause the transceiver to send a command instructing the first RFID tag and the second RFID tag to utilize wait states. The wait states include at least one of a reply wait state, in which an RFID tag waits for an applicable acknowledgement from an RFID reader system, and an acknowledged wait state, in which an RFID tag waits after providing a permanent identifier to an RFID reader.

[0141] According to yet other examples, the first RFID tag has a first permanent identifier; the second RFID tag has a second permanent identifier; and the processing block is further configured to recover at least a portion of the first permanent identifier and at least a portion of the second permanent identifier from the collided replies to the first acknowledgement. The first permanent identifier includes one of an electronic product code (EPC), a tag identifier (TID), or a unique item identifier (UTD). The processing block is further configured to cause the transceiver to transmit a command instructing the first RFID tag and the second RFID tag to process the first multi-acknowledgement. The processing block is further configured to forgo transmitting a command instructing the first RFID tag and the second RFID tag to provide a remainder of their respective permanent identifiers following the first multiacknowledgment. The processing block is further configured to cause the transceiver to transmit a second multi-acknowledgement acknowledging at least one of the first and second RFID tags in response to failing to resolve an identifier received from one of the first or second RFID tags.

[0142] According to some examples, a Radio Frequency Identification (RFID) integrated circuit (IC) configured to be coupled to an antenna, includes a transceiver configured to communicate with RFID reader systems; and a processing block coupled to the transceiver. The processing block is configured to receive, via the transceiver, a query command; send, via the transceiver, a first reply to the query command, the first reply including a collision-resolution (CR) code; receive, via the transceiver, a multi-acknowledgement; determine whether the acknowledgement specifies the RFID IC by determining whether the multi-acknowledgement includes either a portion of the CR code or a special acknowledgement code applicable to multiple RFID ICs; and in response to determining that the multi-acknowledgement specifies the RFID IC, send, via the transceiver, at least a portion of a permanent identifier of the RFID IC.

[0143] According to other examples, the permanent identifier includes one of an electronic product code (EPC), a tag identifier (TID), or a unique item identifier (UID). The processing block is further configured to at least one of cause the RFID IC to enter a first wait state in response to determining that the multi-acknowledgement is not applicable; and cause the RFID IC to enter a second wait state in response to sending at least the portion of the permanent identifier, the first wait state is a reply wait state, in which the RFID IC waits for an applicable acknowledgement, and the second wait state is an acknowledged wait state, in which the RFID IC waits after providing at least a portion of the permanent identifier, the processing block is further configured to have received, via the transceiver, a command instructing the RFID IC to utilize the first and second wait states.

[0144] According to some examples, another Radio Frequency Identification (RFID) reader system includes a transceiver configured to transmit commands to and receive replies from RFID tags; and a processing block coupled to the transceiver. The processing block is configured to cause the transceiver to transmit a first command requesting an identifier; receive, via the transceiver, collided replies to the first command from a plurality of RFID tags; recover, from the collided replies, a first reply from a first RFID tag and a second reply from a second RFID tag of the plurality of RFID tags; cause the transceiver to transmit a first acknowledgement command acknowledging the first RFID tag, wherein the first acknowledgement command causes the first RFID tag to respond and the second RFID tag to enter a first wait state; and receive a response to the first acknowledgment command from the first RFID tag.

[0145] According to other examples, a further Radio Frequency Identification (RFID) reader system includes a reader block configured to transmit commands to and receive replies from RFID tags; and a processing block coupled to the reader block and configured to cause the reader block to transmit a query command; receive, via the reader block, collided replies to the query command from a first RFID tag and a second RFID tag; recover, from the collided replies, a first reply from the first RFID tag and a second reply from the second RFID tag; cause the reader block to transmit consecutive first and second acknowledgement commands, wherein the first acknowledgement command specifies the first RFID tag and the second acknowledgement command specifies the second RFID tag.

[0146] According to further examples, the processing block is further configured to cause the transceiver to transmit a second acknowledgement command acknowledging the second RFID tag, wherein the second acknowledgement command causes the second RFID tag to exit the first wait state and to respond to the second acknowledgement command; and receive a response to the second acknowledgment command from the second RFID tag. The processing block is configured to recover the first reply and the second reply using an error detection technique. The processing block is further configured to cause the transceiver to send a second command instructing the first RFID tag and the second RFID tag to utilize wait states. The wait states include at least one of a reply wait state, in which an RFID tag waits for an applicable acknowledgement from the RFID reader system, and an acknowledged wait state, in which the RFID tag waits after providing a permanent identifier to the RFID reader system.

[0147] According to yet other examples, the first wait state has a predefined expiration time period. The processing block is further configured to extend the first wait state using a parameter in one of the first command or the first acknowledgment command. The first reply includes a first collision-resolution (CR) code; the second reply includes a second CR code; and the first acknowledgement includes at least a portion of the first CR code and at least a portion of the second CR code. The first CR code includes a 16-bit pseudorandom number. The first RFID tag stores a first permanent identifier; the second RFID tag has a second permanent identifier; and the processing block is further configured to recover at least a portion of the first permanent identifier and at least a portion of the second permanent identifier from the collided replies to the first acknowledgement command. The first permanent identifier includes one of an electronic product code (EPC), a tag identifier (TID), or a unique item identifier (UID). [0148] According to further examples, a method is described for an RFID reader to perform actions of the processing block of the RFID reader as described herein. Another method is described for an RFID tag to perform actions of the processing block of the RFID tag IC as described herein. A further method is described for an RFID reader system to perform actions of the processing block of the RFID reader system as described herein.

[0149] As mentioned previously, examples are directed to tag wait states and collided tag reply recovery. Examples additionally include 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, but may be implemented in other processing elements such as FPGAs, DSPs, or other devices as described above.

[0150] Performing the steps, instructions, or operations of a program requires manipulating physical quantities. Usually, though not necessarily, 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. Information represented by the states of these quantities may be referred-to as bits, data bits, samples, values, symbols, characters, terms, numbers, or the like. However, these and similar terms are associated with and merely convenient labels applied to the appropriate physical quantities, individually or in groups.

[0151] Examples furthermore include storage media. Such media, individually or in combination with others, have stored thereon instructions, data, keys, signatures, and other data of a program made according to the examples. A storage medium according to examples is a computer-readable medium, such as a memory, and can be read by a processor of the type mentioned above. If a memory, it can be implemented in any of the ways and using any of the technologies described above.

[0152] Even though it is said that a program may be stored in a computer-readable medium, it does not need to 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.

[0153] Often, for the sake of convenience only, it is desirable to implement and describe a program as software. The software can be unitary, or thought of in terms of various interconnected distinct software modules.

[0154] The foregoing detailed description has set forth various examples of the devices and/or processes via the use of block diagrams and/or examples. Insofar as such block diagrams and/or examples contain one or more functions and/or aspects, each function and/or aspect within such block diagrams or examples may be implemented individually and/or collectively, by a wide range of hardware, software, firmware, or virtually any combination thereof. Some aspects of the examples disclosed herein, in whole or in part, may be equivalently implemented employing integrated circuits, as one or more computer programs running on one or more computers (e.g., as one or more programs running on one or more computer systems), as one or more programs running on one or more processors (e.g. as one or more programs running on one or more microprocessors), as firmware, or as virtually any combination thereof, and that designing the circuitry and/or writing the code for the software and/or firmware would be well within the skill of one of skill in the art in light of this disclosure.

[0155] The present disclosure is not to be limited in terms of the particular examples described in this application, which are intended as illustrations of various aspects. Many modifications and variations can be made without departing from its spirit and scope. Functionally equivalent methods and apparatuses within the scope of the disclosure, in addition to those enumerated herein, will be apparent to those skilled in the art from the foregoing descriptions. Such modifications and variations are intended to fall within the scope of the appended claims. The present disclosure is to be limited only by the terms of the appended claims, along with the full scope of equivalents to which such claims are entitled. It is to be understood that this disclosure is not limited to particular methods, configurations, antennas, transmission lines, and the like, which can, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular examples only, and is not intended to be limiting. [0156] With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

[0157] In general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). If a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases "at least one" and "one or more" to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles "a" or "an" limits any particular claim containing such introduced claim recitation to examples containing only one such recitation, even when the same claim includes the introductory phrases "one or more" or "at least one" and indefinite articles such as "a" or "an" (e.g., “a” and/or “an” should be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, such recitation should be interpreted to mean at least the recited number (e.g., the bare recitation of "two recitations," without other modifiers, means at least two recitations, or two or more recitations).

[0158] Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). Any disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms. For example, the phrase “A or B” will be understood to include the possibilities of “A” or “B” or “A and B.”

[0159] For any and all purposes, such as in terms of providing a written description, all ranges disclosed herein also encompass any and all possible subranges and combinations of subranges thereof. Any listed range can be easily recognized as sufficiently describing and enabling the same range being broken down into at least equal halves, thirds, quarters, fifths, tenths, etc. As a non-limiting example, each range discussed herein can be readily broken down into a lower third, middle third and upper third, etc. All language such as “up to,” “at least,” “greater than,” “less than,” and the like include the number recited and refer to ranges which can be subsequently broken down into subranges as discussed above. Finally, a range includes each individual member. Thus, for example, a group having 1-3 cells refers to groups having 1, 2, or 3 cells. Similarly, a group having 1-5 cells refers to groups having 1, 2, 3, 4, or 5 cells, and so forth.

Claims

CLAIMS WE CLAIM:

1. A method for a Radio Frequency Identification (RFID) integrated circuit (IC), the method comprising: receiving, via a transceiver block configured to receive commands and send replies, a query command; entering a reply state and sending, via the transceiver block, a first reply to the query command; receiving, via the transceiver block, a first acknowledgement command; determining whether the first acknowledgement command specifies the RFID IC; in response to determining that the first acknowledgement command does not specify the RFID IC, one of: waiting in the reply state if the reply state is set to a wait mode; and exiting the reply state if the reply state is set to a go mode.

2. The method of claim 1, further comprising receiving, via the transceiver block, a first command setting the reply state to one of the wait mode and the go mode.

3. The method of claim 2, wherein the first command is one of a query command, an acknowledgement command, or a broadcast command.

4. The method of claim 1, further comprising determining whether an acknowledgement command specifies the RFID IC by determining whether the acknowledgement command includes: a parameter that corresponds to at least part of another parameter sent by the RFID IC in response to the query command; or a special acknowledgement code that specifies all RFID ICs that replied to the query command.

5. The method of any of the claims 1 through 4, wherein the parameter is an

6. The method of any of the claims 1 through 5, further comprising waiting in the reply state by disabling an existing timeout.

7. The method of any of the claims 1 through 6, further comprising, while waiting in the reply state: receiving another acknowledgement command; determining that the other acknowledgement command does not include the first parameter or specify the RFID IC; and continuing waiting in the reply state.

8. The method of any of the claims 1 through 7, further comprising, while waiting in the reply state: in response to receiving an acknowledgement command that specifies the RFID IC, sending an identifier; and waiting for another command specifying the RFID IC or another query command.

9. The method of claim 8, further comprising, after sending the identifier, exiting the reply state and entering an acknowledged state in which the RFID IC waits for the other command specifying the RFID IC or another query command.

10. A Radio Frequency Identification (RFID) integrated circuit (IC) comprising: a transceiver block configured to receive commands and send replies; and a processing block coupled to the transceiver block, wherein the processing block is configured to perform the actions of any of the claims 1 through 9.