Pulse width encoding and interference rejection transmission method based on variable high level length

Abstract

The present application relates to a pulse width encoding and anti-interference transmission method based on variable high level length, which is suitable for one-way communication from a host to a tag in a radio frequency identification system, and comprises: configuring a frame structure, the frame structure comprising a synchronization prefix, a main data sequence and an end prefix, in the main data sequence, the duration of a high level pulse is taken as a data carrier, a low level interval is set as a fixed length, the synchronization prefix is set to comprise a first preset high level length and a first fixed low level length, and the end prefix is set to comprise a second preset high level length and a second fixed low level length; the host generates an encoded signal by using the configured frame structure, and transmits the encoded signal through a radio frequency signal; the tag receives the radio frequency signal, and when detecting the synchronization prefix, enables a main data decoding mode, records the duration of each high level in the main data sequence through a counter, and obtains the main data sequence through analysis.

Description

Technical Field

[0001] This invention relates to the field of radio frequency identification (RFID) communication technology, and more specifically to a pulse width coding and anti-interference transmission method based on variable high-level length. Background Technology

[0002] In RFID systems, baseband coding is the core supporting technology for reliable data interaction between the host (e.g., reader) and the tag. Its coding method directly determines the efficiency and reliability of data transmission, as well as the complexity of tag decoding, and has a decisive impact on the communication performance of the entire RFID system. Among these, the ultra-high frequency (UHF) RFID band, due to its outstanding characteristics such as long transmission distance, strong anti-interference capability, and fast read / write speed, has become a research hotspot and mainstream application in the RFID field, widely used in logistics warehousing, smart retail, intelligent transportation, access control and security, and many other areas.

[0003] Currently, in the field of ultra-high frequency (UHF) RFID, Pulse Interval Encoding (PIE) is a widely adopted baseband encoding method, suitable for forward link communication scenarios where readers transmit data to tags. Its core working principle is as follows: First, a fixed base time unit T is defined. Data information is carried through pulses of fixed width and different lengths of low-level intervals following the pulses. Specifically, logic "0" is represented by a combination of "1 fixed-width pulse + 1T low-level interval", and logic "1" is represented by a combination of "1 fixed-width pulse + 3T low-level interval". Simultaneously, to achieve frame synchronization and ensure that the tag can accurately identify the start and end of the data frame, PIE completes the synchronous positioning of the data frame by setting a specific synchronization prefix and end marker (the end marker is a 7T low-level interval), ensuring the accuracy of data transmission.

[0004] PIEs, with their advantages of simple structure, low implementation cost, and strong anti-interference capabilities, have been widely used in UHF RFID bidirectional communication and some unidirectional communication scenarios, and can basically meet the needs of conventional data transmission. However, in specific scenarios where the reader transmits data unidirectionally to the tag (such as issuing access card instructions, configuring RFID tag parameters, and transmitting one-time instructions), as RFID systems continuously increase their requirements for data transmission efficiency, tag lightweighting, and scenario adaptability, existing PIEs have gradually revealed many limitations, specifically in the following three aspects: First, the data transmission efficiency is low. Each symbol in PIE can only carry 1 bit of data information, and its data transmission efficiency is strictly limited by the binary mapping rule of "1T / 3T" interval length. It cannot realize the parallel transmission of multi-bit data, which is difficult to meet the actual application requirements in unidirectional communication scenarios that need to transmit a large amount of data or have strict requirements on transmission latency.

[0005] Secondly, tag decoding involves a large amount of computation. In one-way transmission scenarios, numerical data is often required to be transmitted, but existing PIEs can only directly transmit binary bit streams. Therefore, when transmitting such numerical data, the decimal or other base values ​​must first be converted into binary bit streams before PIE transmission. After the tag receives the data, it also needs to perform a reverse conversion from the binary bit stream to the target value. This undoubtedly increases the computational load of the tag decoding module, not only increasing the tag's power consumption but also potentially affecting the decoding speed, which is not conducive to the application of lightweight tags.

[0006] Third, it lacks flexibility in adapting to different scenarios. PIE uses a fixed interval length rule, that is, the low-level intervals corresponding to logic "0" and logic "1" are fixed at 1T and 3T respectively, which cannot dynamically adjust the coding efficiency according to changes in actual application scenarios.

[0007] In summary, the PIE baseband encoding method widely used in existing UHF RFID systems suffers from drawbacks such as low transmission efficiency, high computational load for tag decoding, and insufficient flexibility in scenario adaptation when data is transmitted unidirectionally from the reader to the tag. These shortcomings make it difficult to meet the current demands for higher efficiency, lighter weight, and greater flexibility in RFID systems. Therefore, there is an urgent need to propose a baseband encoding technology that can address these shortcomings and improve the communication performance of UHF RFID in unidirectional communication scenarios.

[0008] The above description of the background technology is only for the purpose of facilitating a deeper understanding of the technical solution of the present invention (the technical means used, the technical problems solved, and the technical effects produced, etc.), and should not be regarded as an admission or in any form an implication that the information constitutes prior art known to those skilled in the art. Summary of the Invention

[0009] This invention aims to provide a pulse width encoding and anti-interference transmission method based on variable high-level length, which solves the problems of low transmission efficiency, complex decoding, and insufficient flexibility of traditional PIE encoding in one-way communication scenarios. On this basis, this invention further provides an anti-interference optimization method to solve the problem of data misjudgment that is prone to occur in variable high-level encoding in strong interference scenarios, and achieves a balance between encoding efficiency and communication reliability.

[0010] According to an embodiment of the present invention, a pulse width encoding and anti-interference transmission method based on variable high-level length is provided, which is applicable to one-way communication from host to tag in a radio frequency identification system. The method includes: configuring a frame structure, wherein the frame structure includes a synchronization prefix, a main data sequence, and an end prefix; in the main data sequence, the duration of a high-level pulse is used as the data carrier, the low-level interval is set to a fixed length, the synchronization prefix is ​​set to include a first preset high-level length and a first fixed low-level length, and the end prefix is ​​set to include a second preset high-level length and a second fixed low-level length; the host generates an encoded signal using the configured frame structure and transmits the encoded signal via a radio frequency signal; the tag receives the radio frequency signal, and when the synchronization prefix is ​​detected, it activates the main data decoding mode, records the duration of each high-level pulse in the main data sequence using a counter, and parses the main data sequence to obtain the main data sequence.

[0011] Preferably, the frame structure further includes: a transition marker and a PIE-encoded check information sequence, wherein the transition marker is configured to include a third preset high-level length and a third fixed low-level length. The method further includes: the host calculating a redundancy check value for the master data sequence, converting the redundancy check value into a binary bit stream, and converting the binary bit stream into a PIE-encoded check information sequence using a PIE encoding mode; the host generating an encoded signal according to a frame structure configured in the order of synchronization prefix, master data sequence, transition marker, PIE-encoded check information sequence, and end suffix, and transmitting the encoded signal via a radio frequency signal.

[0012] Preferably, the third preset high-level length is set to 3μs; the third fixed low-level length is set to 10μs.

[0013] Preferably, the pulse width encoding and anti-interference transmission method based on variable high-level length according to an embodiment of the present invention further includes: when a transition marker is detected in the main data decoding mode, the tag switches to PIE decoding mode; in the PIE decoding mode, the tag parses the binary check bit stream by detecting the pulse interval to restore the check value; the tag recalculates the redundant check value for the parsed main data sequence, compares the recalculated redundant check value with the restored check value, and determines the validity of the data based on the comparison result.

[0014] Preferably, the pulse width coding and anti-interference transmission method based on variable high-level length according to an embodiment of the present invention further includes: when the comparison results are consistent, the tag determines that the data is valid, and thus executes the instruction corresponding to the main data sequence; when the comparison results are inconsistent, the tag determines that the data is invalid, and thus triggers a retransmission request.

[0015] Preferably, the redundancy check value is a CRC check value, and the number of bits in the CRC check is dynamically adjusted according to the length of the main data sequence; when the main data sequence includes less than 3 data symbols, an 8-bit CRC check is used, and when the main data sequence includes more than 10 data symbols, a 16-bit CRC check is used.

[0016] Preferably, the rules for the PIE encoding mode are set as follows: binary 0 represents a fixed-width high-level pulse plus a 1T interval, and binary 1 represents a fixed-width high-level pulse plus a 3T interval; wherein, T is the basic time unit, and the value of T is less than the fixed length of the low-level interval of the main data sequence.

[0017] Preferably, the main data sequence consists of N variable high-level data symbols, where N is an integer greater than or equal to 1; each variable high-level data symbol includes a high-level t. n And a fixed-length low-level interval, t n The high-level duration corresponding to the data value, where n is an integer greater than or equal to 1 and less than or equal to N.

[0018] Preferably, in the main data decoding mode, the tag starts the counter by detecting the rising edge of the high level and stops the counter by detecting the falling edge, reads the duration of the high level and parses the corresponding data value.

[0019] Preferably, the fixed length of the low-level interval of the main data sequence is set to 6 μs; the first preset high-level length is set to 50 μs; the first fixed low-level length is set to 20 μs; the second preset high-level length is set to 10 μs; and the second fixed low-level length is set to 30 μs.

[0020] Preferably, the pulse width coding and anti-interference transmission method based on variable high-level length according to an embodiment of the present invention further includes: during the parsing of the main data sequence, the tag sets a fault tolerance interval for the duration of the high level, wherein the fault tolerance interval is set to ±3μs.

[0021] The present invention adopts the above technical solution, which has the following beneficial effects: 1. High encoding efficiency: Variable high-level encoding directly maps numerical values ​​or multi-base information to multiple bits by mapping the duration of the high level. A single symbol can carry more than 1 bit of information, which increases the amount of data transmitted per unit time. At the same time, no additional encoding conversion is required for numerical data, which reduces transmission redundancy.

[0022] 2. Simplified decoding logic: Tag decoding does not require complex binary bit stream conversion. The main data can be parsed simply by detecting the length of the high level using a counter, which reduces the hardware cost and computational load of the tag, making it especially suitable for low-cost passive tags.

[0023] 3. High flexibility and compatibility: The variable high-level encoding can dynamically adjust the absolute length of the high / low level according to the communication distance. Increasing the length at long distances improves detection stability, while shortening the length at short distances increases the transmission rate. The anti-interference optimization scheme only adds a PIE check field to the end of the frame without changing the core encoding logic of the main data. It can be seamlessly adapted to the original tag hardware and only requires adding a simple PIE decoding module to the tag, which has low complexity.

[0024] 4. Significantly improved anti-interference capability: A layered protection system of "soft check + hard check" is constructed. The fault tolerance range of the master data solves the numerical deviation caused by slight interference, and the CRC redundancy check of PIE encoding solves the data error caused by severe interference. At the same time, it integrates the high efficiency of variable high-level encoding and the strong anti-interference capability of PIE encoding, taking into account both transmission efficiency and communication reliability.

[0025] 5. Highly efficient retransmission mechanism: Data validity can be determined by quickly comparing the check value, avoiding the tag from executing invalid commands. It is especially suitable for one-way communication scenarios with high requirements for command correctness, such as access control cards and industrial identity recognition. Attached Figure Description

[0026] The exemplary embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. For clarity, the same components in different drawings are shown with the same reference numerals. It should be noted that the drawings are for illustrative purposes only and are not necessarily drawn to scale. In these drawings: Figure 1 A schematic diagram illustrating a frame structure according to an embodiment of the present invention; Figure 2 A flowchart illustrating a pulse width encoding and anti-interference transmission method based on a variable high-level length according to an embodiment of the present invention is provided. Figure 3 A schematic diagram illustrating a frame structure according to another embodiment of the present invention; Figure 4 The flowchart illustrates a pulse width encoding and anti-interference transmission method based on a variable high-level length according to another embodiment of the present invention. Detailed Implementation

[0027] The following is a detailed description of the embodiments of the present invention. These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes. However, the scope of protection of the present invention is not limited to the following embodiments.

[0028] In the following, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0029] This invention proposes a pulse width encoding method based on variable high-level length carrying data, which is applicable to one-way communication from host to tag in radio frequency identification systems. Figure 1 A schematic diagram illustrating a frame structure according to an embodiment of the present invention. See also Figure 1 The frame structure may include a synchronization prefix, a main data sequence, and an end prefix.

[0030] In the main data sequence, the duration t of the high-level pulse can be used as the data carrier, and the low-level interval can be set to a fixed length as a separation between symbols and a synchronization reference. The fixed-length low-level interval can be set to 6μs, but this is only an example and the invention is not limited thereto.

[0031] The main data sequence can consist of N variable high-level data symbols, where N is an integer greater than or equal to 1. Each variable high-level data symbol includes a high-level duration t. n and a fixed-length low-level interval.

[0032] The high-level duration t can be directly mapped to data values. For example, the physical duration t in microseconds can be directly mapped to the numerical data value to be transmitted, with the high-level duration being the data value itself, without any base conversion or encoding conversion. In this mapping method, the high-level duration t can be flexibly adjusted according to the magnitude of the numerical data value. For example, t=6μs directly corresponds to the data value 6, t=136μs directly corresponds to the data value 136, and t=2793μs directly corresponds to the data value 2793. This allows for seamless adaptation to the transmission needs of various pure numerical data, such as integer command parameters, thresholds, and identity code values.

[0033] Alternatively, data values ​​can be mapped using multi-level bits. The high-level duration *t* is hierarchically planned according to a preset fixed duration. Each fixed high-level duration *t* corresponds to a unique set of binary bit streams. This method allows a single variable high-level data symbol to carry multiple bits of information, breaking through the traditional single-symbol, single-bit transmission limitation and significantly improving data transmission efficiency per unit time. Under this mapping method, the preset fixed duration can be flexibly set according to communication rate requirements. A typical fixed duration can be set to 6μs; for example, t=6μs maps to binary 00, t=12μs maps to binary 01, and t=18μs maps to binary 10. Subsequent levels can be expanded according to this fixed duration to adapt to the transmission requirements of 2-bit, 3-bit, and higher multi-bit data, meeting the needs of short-frame, high-speed binary data transmission scenarios.

[0034] This invention achieves full coverage adaptation for both numerical and binary data by designing two encoding methods for high-level duration t: direct numerical mapping and multi-level bit mapping. Direct numerical mapping eliminates the conversion step between numerical and binary data, simplifies the decoding operation of tags, and reduces the hardware power consumption of passive tags, making it particularly suitable for the transmission of numerical data such as access control instructions and device thresholds. Multi-level bit mapping enables single-symbol multi-bit transmission, greatly improving data transmission efficiency and adapting to scenarios with high transmission rate requirements, such as identification codes and short-frame binary instructions.

[0035] The synchronization prefix serves as the start identifier of the data frame, triggering the tag to begin reception and complete clock synchronization. Its structure can be configured as a continuous combination of a first preset high-level length and a first fixed low-level length. The end suffix serves as the end identifier of the data frame, marking the completion boundary of data transmission. Its structure can be configured as a continuous combination of a second preset high-level length and a second fixed low-level length. The high-level lengths of both the synchronization prefix and end suffix are differentiated, specific preset values, clearly distinguishing them from the high-level duration t in the main data sequence. This avoids confusion between frame boundaries and data symbols during tag decoding, ensuring the accuracy of frame synchronization.

[0036] According to an embodiment of the present invention, the first preset high-level length of the synchronization prefix is ​​configured to be 50 μs and the first fixed low-level length is configured to be 20 μs, and the second preset high-level length of the suffix is ​​configured to be 10 μs and the second fixed low-level length is configured to be 30 μs. However, the present invention does not impose a unique limitation on the specific level length values ​​of the synchronization prefix and the suffix. In practical applications, the first preset high-level length, the first fixed low-level length, the second preset high-level length, and the second fixed low-level length can be adaptively adjusted according to the actual scenario requirements such as the communication distance of the RFID system, the hardware detection accuracy, and the intensity of electromagnetic interference. Only two core constraints need to be met: First, the first preset high-level length of the synchronization prefix and the second preset high-level length of the suffix need to maintain a significant numerical difference (no overlapping interval) from the high-level duration t of the main data sequence to ensure that the tag can accurately identify the frame start and end signals; Second, the low-level lengths of the synchronization prefix and the suffix are fixed values ​​and are adapted to the fixed low-level interval of the main data sequence, without affecting the data symbol separation logic.

[0037] Figure 2 The flowchart illustrates a pulse width coding and anti-interference transmission method based on a variable high-level length according to an embodiment of the present invention. In the unidirectional communication between the host and the tag in a radio frequency identification system, the pulse width coding and anti-interference transmission method based on a variable high-level length may include the following steps: In step S210, the frame structure is configured, which includes a synchronization prefix, a master data sequence, and an end prefix.

[0038] In step S220, the host (e.g., a reader) can generate an encoded signal using the frame structure configured above and transmit the encoded signal via a radio frequency signal. Specifically, the host generates a pulse sequence with a corresponding high-level length based on the data to be transmitted, inserts a synchronization prefix and an end suffix, and then transmits it via a radio frequency signal.

[0039] In step S230, the tag receives an RF signal. When a synchronization prefix is ​​detected, the main data decoding mode is activated. The duration of each high level in the main data sequence is recorded by a counter to parse the main data sequence. Specifically, after receiving the signal, the tag starts the counter by detecting the rising edge of the high level and stops counting on the falling edge, directly reads the high level duration to parse the data, and achieves frame synchronization through the synchronization prefix / suffix.

[0040] Furthermore, this invention addresses the issue of slight deviations in low-interference scenarios by employing a soft-verification method with a tolerance range. Specifically, the tag and the host (e.g., a reader) pre-agree on the mapping rules, tolerance ranges, and related frame structure parameters between the high-level duration and data value during system initialization. During data parsing, the tag matches the actual high-level duration measured by the counter with the tolerance range corresponding to each theoretical mapping value according to the built-in preset mapping rules. When the measured high-level duration falls within the tolerance range of a certain theoretical mapping value, it is determined that the measured value corresponds to that theoretical mapping value. This compensates for high-level detection deviations caused by minor hardware timing errors and weak electromagnetic noise, achieving anti-interference parsing under slight interference.

[0041] The pulse width coding and anti-interference transmission method based on variable high-level length of the present invention will be described in detail below with reference to specific embodiments.

[0042] In this embodiment, the parameters are configured as follows: the fixed-length low-level interval of the main data sequence is 6μs; the synchronization prefix is ​​50μs high level + 20μs low level; the end suffix is ​​10μs high level + 30μs low level; and the parsing tolerance range of the main data sequence is ±3μs.

[0043] This embodiment is applicable to a one-way command transmission scenario for indoor access control. This scenario has no strong electromagnetic interference and only slight hardware timing errors exist. The host (e.g., a reader) transmits a single access control command parameter 136” to the tag. The high-level duration is achieved through direct numerical mapping. The specific implementation steps are as follows: 1. Frame structure configuration: Configure the frame structure as synchronization prefix + main data sequence + end suffix.

[0044] 2. Host Encoding and Transmission: Based on the instruction parameter "136" to be transmitted, the host generates the corresponding master data sequence. This master data sequence is a variable high-level data symbol (N=1), specifically 136μs high level + 6μs fixed low level. The sequence is concatenated in the order of "synchronization prefix → master data sequence → end suffix" to form a complete encoded signal. The timing of the concatenated signal is: 50μs high level + 20μs low level → 136μs high level + 6μs low level → 10μs high level + 30μs low level. The host modulates this encoded signal into an radio frequency signal and transmits it unidirectionally to the tag. 3. Tag Reception and Parsing: After receiving the RF signal, when the tag detects a synchronization prefix of 50μs high level + 20μs low level, it determines that the data frame has started and immediately activates the main data decoding mode to prepare for parsing the subsequent main data sequence. In the main data decoding mode, when the tag detects the rising edge of the subsequent high level, it starts the built-in counter and stops the counter when it detects the falling edge of the high level. The high level duration recorded by the counter is read. The high level duration is read as 134μs. The tag matches the tolerance range of this measured value with the theoretical mapping value. That is, 134μs falls within the tolerance range of 136μs ± 3μs (133μs-139μs). Therefore, the theoretical mapping value corresponding to this measured high level is determined to be 136, and the parameter to be transmitted is directly parsed as 136. After the tag completes the parsing of the main data sequence, it continues to detect the subsequent signal. When it recognizes the ending suffix of 10μs high level + 30μs low level, it determines that the data frame transmission is complete, confirms that the parsed data is valid, and then executes the access control door opening command corresponding to parameter 136.

[0045] This embodiment addresses the low-interference, one-way command transmission scenario for indoor access control. Based on a high-level direct numerical mapping encoding method, it achieves efficient and accurate transmission of command parameters. The ±3μs error tolerance range effectively corrects slight detection deviations caused by hardware timing, ensuring decoding accuracy without additional redundant verification. This significantly simplifies tag decoding logic and reduces the power consumption and hardware cost of passive tags. The standardized level configuration of the synchronization prefix and suffix, along with the design of a fixed low-level interval in the main data sequence, enables accurate frame synchronization and clear separation of data symbols. The method of directly mapping single symbols to single values ​​eliminates the number system conversion step, reducing transmission redundancy while improving overall transmission efficiency in low-interference scenarios. This perfectly meets the practical application needs of short-range, low-interference RFID one-way communication scenarios such as indoor access control.

[0046] In the pulse width encoding based on variable high-level length of this invention, the duration of the high-level signal is susceptible to noise, multipath interference, or hardware timing errors, leading to data misjudgment by the tag (for example, the actual transmission time t = 136μs may be detected as 133μs or 139μs due to interference). Although setting a fault tolerance interval can reduce the probability of misjudgment to some extent, in complex scenarios such as dense metal areas and strong electromagnetic interference, relying solely on a single encoding method is still insufficient to meet the requirements of reliable transmission, and the anti-interference capability is significantly limited.

[0047] To address this, this invention further proposes an optimized scheme that integrates master data and check information into a dual-encoding layer. In the master data layer, variable high-level pulse width encoding is used to transmit core information such as instruction parameters and numerical data, retaining its advantages of high encoding efficiency and simple tag decoding logic. In the check information layer, cyclic redundancy check (CRC) is performed on the master data sequence. The resulting check value is converted into a binary bit stream, and a PIE-encoded check information sequence is generated using traditional pulse interval encoding (PIE), appended to the end of the data frame. This invention fully utilizes the strong anti-interference capability and good synchronization stability of PIE encoding to complete the correctness verification and validity determination of the master data. Through the complementary advantages of the two encoding layers, the reliability of data transmission in strong interference and complex electromagnetic environments is significantly improved without sacrificing transmission efficiency.

[0048] Figure 3 A schematic diagram illustrating a frame structure according to another embodiment of the present invention. See also Figure 3 The frame structure may further include: a transition marker and a PIE-encoded checksum sequence. Accordingly, the complete frame structure includes, in order: a synchronization prefix, a master data sequence, a transition marker, a PIE-encoded checksum sequence, and an end suffix.

[0049] As mentioned above, the synchronization prefix may include a continuous combination of a first preset high level length and a first fixed low level length; the end suffix may include a continuous combination of a second preset high level length and a second fixed low level length.

[0050] The main data sequence can consist of N variable high-level symbols, each variable high-level symbol being a "high-level t" symbol. n + Fixed-length low-level interval", where t n For specific data values, 1 ≤ n ≤ N. For example, t1 = 136 μs represents the value 136, t2 = 24 μs represents the value 24, and so on.

[0051] The transition marker can be set to include a third preset high-level length and a third fixed low-level length, used to distinguish the main data sequence from the check information sequence, and to indicate the decoding mode switch to the tag, that is, to switch from the high-level length detection mode of the main data to the PIE decoding mode.

[0052] According to an embodiment of the present invention, the fixed-length low-level interval of the main data sequence can be set to 6 μs, the first preset high-level length of the synchronization prefix can be set to 50 μs, the first fixed low-level length can be set to 20 μs, the second preset high-level length of the end suffix can be set to 10 μs, the second fixed low-level length can be set to 30 μs, the third preset high-level length of the transition mark can be set to 3 μs, and the third fixed low-level length can be set to 10 μs, but the present invention is not limited to the above specific values.

[0053] To ensure that the tag can be uniquely identified, the third preset high-level length of the transition mark, the first preset high-level length of the synchronization prefix, the second preset high-level length of the end suffix, and the high-level length of the main data sequence (usually not less than 6μs) are all different from each other.

[0054] The PIE-encoded check information sequence is obtained as follows: the redundancy check value is calculated on the master data sequence, the redundancy check value is converted into a binary bit stream, and the binary bit stream is converted into a PIE-encoded check information sequence through the PIE encoding mode.

[0055] Specifically, for the master data sequence (t1, t2, ..., t... n Calculate the CRC checksum, choosing either 8-bit or 16-bit CRC. Convert the obtained checksum into a binary bit stream and transmit it using PIE encoding. The PIE encoding rules are set as follows: A binary "0" corresponds to "1 pulse + 1T interval"; A binary "1" corresponds to "1 pulse + 3T interval".

[0056] Here, T is the basic time unit, for example, 1 μs. Its value is adapted to the fixed-length low-level interval (6 μs) of the main data sequence, satisfying 1T < fixed-length low-level interval (6 μs), thus avoiding confusion with the fixed low-level interval of the main data. The pulse is a short high-level pulse of fixed width used to mark the start of a bit. Its width is less than the minimum high-level length of the main data sequence to avoid confusion with the main data symbols.

[0057] In this invention, the redundancy check value is the CRC check value, and the number of bits of the CRC is dynamically adjusted according to the length of the main data sequence. When the main data sequence includes less than 3 data symbols, an 8-bit CRC check is used, and when the main data sequence includes more than 10 data symbols, a 16-bit CRC check is used.

[0058] For a main data sequence containing 4 to 9 data symbols, this invention preferentially uses an 8-bit CRC checksum. This is because an 8-bit CRC is sufficient for the checksum requirements under normal interference environments, and it avoids the problems of increased checksum length and reduced transmission efficiency associated with a 16-bit CRC. If the application scenario is a strong electromagnetic interference environment (such as an industrial workshop or a metal-intensive environment), the CRC checksum bit length for the main data sequence containing 4 to 9 data symbols can be upgraded to 16 bits to further improve anti-interference capabilities. This adjustment is an equivalent implementation of this invention.

[0059] Figure 4 The flowchart illustrates a pulse width coding and anti-interference transmission method based on variable high-level length according to another embodiment of the present invention. In the unidirectional communication between the host and the tag in a radio frequency identification system, the pulse width coding and anti-interference transmission method based on variable high-level length may include the following steps: In step S410, the frame structure is configured, which includes a synchronization prefix, a master data sequence, a transition marker, a PIE-encoded check information sequence, and an end suffix.

[0060] In step S420, the host calculates the redundancy check value for the master data sequence, converts the redundancy check value into a binary bit stream, and converts the binary bit stream into a PIE encoded check information sequence through PIE encoding mode. The host constructs a frame structure in the order of synchronization prefix, master data sequence, transition mark, PIE encoded check information sequence, and end suffix, generates an encoded signal, and sends it to the tag through a radio frequency signal.

[0061] In step S430, the tag receives an RF signal and activates the master data decoding mode when a synchronization prefix is ​​detected. A counter records the duration of each high-level signal in the master data sequence to parse the master data sequence. In master data decoding mode, when a transition marker is detected, the tag switches to PIE decoding mode. In PIE decoding mode, the tag parses the binary check bit stream by detecting pulse intervals to reconstruct the check value. The tag recalculates the redundancy check value for the parsed master data sequence, compares the recalculated redundancy check value with the reconstructed check value, and determines the data validity based on the comparison result.

[0062] When the comparison results match, the tag determines that the data is valid and executes the instruction corresponding to the master data sequence; when the comparison results do not match, the tag determines that the data is invalid and triggers a retransmission request.

[0063] The pulse width coding and anti-interference transmission method based on variable high-level length of the present invention will be described in detail below with reference to specific embodiments.

[0064] In this embodiment, the parameters are configured as follows: the fixed-length low-level interval of the main data sequence is 6μs; the synchronization prefix is ​​50μs high level + 20μs low level; the end suffix is ​​10μs high level + 30μs low level; the transition marker is 3μs high level + 10μs low level; the parsing tolerance range of the main data sequence is ±3μs, and T is 1μs.

[0065] This embodiment is applicable to one-way command transmission scenarios in industrial access control, where metal equipment is densely packed and electromagnetic interference is strong. The reader transmits the main data sequence "136, 24, 58" (3 data symbols, N=3) to the tag. The high-level duration adopts a direct numerical mapping method and uses 8-bit CRC check. The specific implementation steps are as follows: 1. Frame structure configuration: Configure the frame structure as synchronization prefix + main data sequence + transition marker + PIE encoded checksum sequence + end suffix; 2. Host encoding and transmission: a) Generate the main data sequence: Convert the data to be transmitted "136, 24, 58" into three variable high-level data symbols, namely 136μs high level + 6μs low level, 24μs high level + 6μs low level, and 58μs high level + 6μs low level; b) Calculate and convert the check value: Calculate the CRC check value 0x5A using an 8-bit CRC check algorithm (generator polynomial 0x07) on the main data sequence, and convert it into a binary bit stream "01011010"; c) PIE Encoding Check Information: According to the PIE encoding rules (0 → pulse + 1μs interval, 1 → pulse + 3μs interval), the binary bit stream "01011010" is converted into a PIE encoding check information sequence. d) Concatenation and transmission: Concatenate the synchronization prefix, main data sequence, transition marker (3μs high level + 10μs low level), PIE encoded check information sequence, and end suffix in sequence to generate an anti-interference coded signal and transmit it through radio frequency signal; 3. Tag reception and parsing: a) Master data decoding: After the tag detects the synchronization prefix, it enables the master data decoding mode. It detects the high level durations of 135μs (falling into the ±3μs fault tolerance range, resolved as 136), 24μs, and 59μs (falling into the ±3μs fault tolerance range, resolved as 58) in sequence, and obtains the master data sequence "136, 24, 58". b) Decoding mode switching: After detecting a transition marker of 3μs high level + 10μs low level, immediately switch to PIE decoding mode; c) Restore the check value: By parsing the PIE-encoded check information sequence through the detection pulse interval, the binary bit stream "01011010" is restored and further converted into an 8-bit CRC check value 0x5A; d) Verification and execution: The tag recalculates the 8-bit CRC check value of the parsed master data sequence. The result is 0x5A, which is consistent with the restored check value. The data is deemed valid, and the corresponding industrial access control door opening command is executed.

[0066] Additionally, if strong electromagnetic interference causes a deviation in the main data sequence of the tag parsing, the specific handling of the tag is as follows: a) Master data decoding: Due to electromagnetic interference, the high-level durations parsed by the tag are 129μs (exceeding the ±3μs tolerance range), 24μs, and 58μs, respectively, resulting in the biased master data sequence "129, 24, 58". b) Decoding mode switching: After detecting a transition marker of 3μs high level + 10μs low level, the mode switches from main data decoding mode to PIE decoding mode; c) Restore the check value: In PIE decoding mode, the PIE encoded check information sequence is parsed by detecting the pulse interval to restore the binary bit stream "01011010", which is then converted into an 8-bit CRC check value 0x5A. d) Verification and execution: The tag recalculates the 8-bit CRC check value for the parsed master data sequence with the deviation, and compares the result with the restored check value 0x5A. Since the two are inconsistent, the data is determined to be interfered with and invalid. The tag maintains a specific load state and triggers a retransmission request. After the host detects the communication failure, it retransmits the encoded signal until the tag receives valid data and executes the instruction.

[0067] This invention adopts a layered anti-interference architecture of soft verification + hard verification: soft verification is achieved by setting a ±3μs fault tolerance range in the main data parsing, which can effectively offset slight noise and hardware timing errors; at the same time, hard verification is achieved by using PIE encoding to carry CRC verification information, which can correct data errors caused by strong interference, forming a dual protection mechanism.

[0068] This invention deeply integrates the advantages of high efficiency and simple decoding of variable high-level encoding with the stable pulse interval and strong anti-interference characteristics of PIE encoding, significantly improving data reliability while ensuring high-speed transmission. Since only a PIE check field is added to the end of the frame structure, no changes are needed to the core encoding logic of the main data, resulting in strong compatibility and seamless adaptation to existing tag hardware. It only requires the addition of a simple PIE decoding module, making the overall modification cost low. Tags can quickly determine data validity based on the check result, avoiding the execution of erroneous instructions and effectively improving system operational stability.

[0069] This invention is particularly suitable for RFID one-way communication scenarios in environments with strong interference and complex conditions, such as industrial access control (dense metal equipment, strong electromagnetic interference), parking lot card instruction transmission (vehicle engines generate strong electromagnetic noise), and outdoor equipment identification (weather and temperature changes cause signal attenuation and fluctuations). Through a dual-encoding layer fusion design of the main data layer and the verification information layer, this invention can fully leverage the high-efficiency transmission advantages of variable high-level encoding and rely on PIE encoding to improve the system's anti-interference capability, significantly improving the communication reliability and instruction execution accuracy of RFID devices in harsh environments.

[0070] The present invention also provides a pulse width coding and anti-interference transmission system based on variable high-level length, which may include a host and a tag. The host and the tag communicate via radio frequency identification.

[0071] The host unit may include a main control module, an encoding module, a verification encoding module, a frame structure splicing module, an RF transmission module, and an RF antenna. The main control module controls the overall data processing flow; the encoding module generates a main data sequence based on a variable high-level length; the verification encoding module calculates the CRC check value and generates a PIE-encoded check information sequence; the frame structure splicing module splices complete data frames in a preset order; and the RF transmission module and RF antenna modulate the encoded signal and transmit it to the tag in the form of an RF signal.

[0072] The tag may include an RF antenna, an RF receiving module, a level detection module, a counter, a control module, a storage module, and an execution module. The RF antenna and RF receiving module are used to receive and demodulate the RF signals sent by the host; the level detection module and counter are used to detect level transitions and obtain the duration of the high level; the storage module is used to pre-store mapping rules, frame structure parameters, and fault tolerance intervals; the control module is used to complete master data parsing, decoding mode switching, CRC verification, and data validity determination; the execution module is used to execute corresponding operations or trigger retransmission requests based on valid instructions.

[0073] The specific processing procedures of each module in the host and tag have been described in detail above and will not be repeated here. It should be understood that the host and tag of the present invention are not limited to the modules listed above. Any device structure that can implement the pulse width coding and anti-interference transmission method based on variable high-level length of the present invention should be covered within the protection scope of the present invention.

[0074] The various embodiments of the present invention are not an exhaustive list of all possible combinations, but are intended to describe representative aspects of the invention, and the contents described in the various embodiments can be applied independently or in two or more combinations.

[0075] The description of the exemplary embodiments presented above is merely illustrative of the technical solutions of the present invention and is not intended to be exhaustive, nor is it intended to limit the invention to the precise forms described. Obviously, those skilled in the art can make many changes and variations based on the above teachings. The exemplary embodiments were chosen and described to explain the specific principles of the invention and its practical application, thereby enabling others skilled in the art to understand, implement, and utilize the various exemplary embodiments of the invention and their various alternatives and modifications. The scope of protection of the present invention is intended to be defined by the appended claims and their equivalents.

Claims

1. A pulse width encoding and anti-interference transmission method based on variable high-level length, applicable to one-way communication from host to tag in a radio frequency identification system, comprising: Configure a frame structure, which includes a synchronization prefix, a main data sequence, and an end prefix. In the main data sequence, the duration of the high-level pulse is used as the data carrier, the low-level interval is set to a fixed length, the synchronization prefix is ​​set to include a first preset high-level length and a first fixed low-level length, and the end prefix is ​​set to include a second preset high-level length and a second fixed low-level length. The host generates an encoded signal using the configured frame structure and transmits the encoded signal via a radio frequency signal; The tag receives the radio frequency signal and, when a synchronization prefix is ​​detected, enables the main data decoding mode. It records the duration of each high level in the main data sequence using a counter to parse and obtain the main data sequence.

2. The pulse width coding and anti-interference transmission method based on variable high-level length according to claim 1, wherein, The frame structure further includes: a transition marker and a PIE-encoded check information sequence, wherein the transition marker is configured to include a third preset high-level length and a third fixed low-level length. The method further includes: The host calculates a redundancy check value for the main data sequence, converts the redundancy check value into a binary bit stream, and converts the binary bit stream into a PIE-encoded check information sequence through PIE encoding mode. The host generates an encoded signal according to a frame structure set in the order of synchronization prefix, master data sequence, transition marker, PIE encoded check information sequence, and end suffix, and transmits the encoded signal via radio frequency signal.

3. The pulse width coding and anti-interference transmission method based on variable high-level length according to claim 2, wherein, The third preset high-level length is set to 3μs; The third fixed low-level length is set to 10μs.

4. The pulse width coding and anti-interference transmission method based on variable high-level length according to claim 2, further comprising: When a transition marker is detected in the main data decoding mode, the tag switches to PIE decoding mode. In PIE decoding mode, the tag parses the binary check bit stream by detecting the pulse interval in order to reconstruct the check value; The tag recalculates the redundancy check value of the parsed master data sequence, compares the recalculated redundancy check value with the restored check value, and determines the validity of the data based on the comparison result.

5. The pulse width coding and anti-interference transmission method based on variable high-level length according to claim 4, further comprising: When the comparison results match, the tag determines that the data is valid and executes the instruction corresponding to the master data sequence. When the comparison results are inconsistent, the tag determines that the data is invalid, thereby triggering a retransmission request.

6. The pulse width coding and anti-interference transmission method based on variable high-level length according to claim 2, wherein, The redundancy check value is the CRC check value, and the number of bits in the CRC check is dynamically adjusted according to the length of the master data sequence. When the main data sequence includes three or fewer data symbols, an 8-bit CRC check is used. When the main data sequence includes more than 10 data symbols, a 16-bit CRC check is used.

7. The pulse width coding and anti-interference transmission method based on variable high-level length according to claim 2, wherein, The rules for the PIE encoding mode are set as follows: Binary 0 represents a high-level pulse of fixed width plus a 1T interval, and binary 1 represents a high-level pulse of fixed width plus a 3T interval; Where T is the basic time unit, and the value of T is less than the fixed length of the low-level interval of the main data sequence.

8. The pulse width coding and anti-interference transmission method based on variable high-level length according to claim 1 or 2, wherein, The main data sequence consists of N variable high-level data symbols, where N is an integer greater than or equal to 1; Each variable high-level data symbol includes a high-level t. n And a fixed-length low-level interval, t n The high-level duration corresponding to the data value, where n is an integer greater than or equal to 1 and less than or equal to N.

9. The pulse width coding and anti-interference transmission method based on variable high-level length according to claim 8, wherein, In the main data decoding mode, the tag starts the counter by detecting the rising edge of the high level and stops the counter by detecting the falling edge. It reads the duration of the high level and parses the corresponding data value.

10. The pulse width coding and anti-interference transmission method based on variable high-level length according to claim 1 or 2, wherein, The fixed length of the low-level interval in the main data sequence is set to 6μs; The first preset high-level length is set to 50μs; The first fixed low-level length is set to 20μs; The second preset high-level length is set to 10μs; The second fixed low-level length is set to 30μs.

11. The pulse width coding and anti-interference transmission method based on variable high-level length according to claim 1 or 2, further comprising: During the parsing of the main data sequence, the tag sets a tolerance range for the duration of the high level, which is set to ±3μs.

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