Data receiving apparatus and data receiving method

Abstract

A data receiving device and a corresponding data receiving method are provided. The data receiving device includes: path control logic configured to store L symbol paths, where L is a natural number equal to or greater than 2; L feedback filters configured to calculate L inter-symbol interference (ISI) for each of the L symbol paths; L arithmetic units configured to remove the L ISI from the output of a feedforward equalizer; and a path metric calculator configured to receive the outputs of the L arithmetic units and calculate a path metric for each of the L symbol paths, wherein the path control logic is further configured to select L values ​​from the calculated path metrics of the L symbol paths to update the L symbol paths.

Description

[0001] Cross-references to related applications

[0002] This application claims priority to Korean Patent Application No. 10-2020-0142237, filed on October 29, 2020, with the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure relates to a data receiving apparatus and a data receiving method. Background Technology

[0004] Techniques for removing inter-symbol interference (ISI) experienced by signals or data received through wireless communication channels have been investigated. Equalizers can be applied to improve the reliability of multilevel signals received through wireless communication channels, such as, but not limited to, a low bit error rate (BER). Summary of the Invention

[0005] The embodiments of this disclosure provide a data receiving apparatus capable of improving the detection accuracy of unit symbols transmitted by the transmitting device without unduly increasing the computational load of the receiving device.

[0006] The embodiments of this disclosure also provide a data receiving method that can improve the detection accuracy of unit symbols transmitted by the transmitting device without unduly increasing the computational load of the receiving device.

[0007] According to an embodiment of this disclosure, a data receiving apparatus includes: path control logic configured to store L symbol paths, where L is a natural number greater than or equal to 2; L feedback filters configured to calculate L inter-symbol interference (ISI) for each of the L symbol paths; L arithmetic units configured to remove the L ISI from the output of a feedforward equalizer; and a path metric calculator configured to receive the outputs of the L arithmetic units and calculate a path metric for each of the L symbol paths, wherein the path control logic is further configured to select L values ​​from the calculated path metrics of the L symbol paths to update the L symbol paths respectively.

[0008] According to embodiments of this disclosure, a data receiving apparatus includes: a feedforward equalizer configured to receive a multilevel signal through a channel; and a list decision feedback equalizer configured to generate a recovered multilevel signal using the output of the feedforward equalizer, wherein the list decision feedback equalizer calculates inter-symbol interference (ISI) for L symbol paths, where L is a natural number equal to or greater than 2, wherein after removing the L ISI from the output of the feedforward equalizer, the list decision feedback equalizer calculates a path metric for each of the L symbol paths, and wherein the list decision feedback equalizer generates the recovered multilevel signal by repeatedly selecting L values ​​from the calculated path metrics of the L symbol paths to update the L symbol paths.

[0009] According to an embodiment of this disclosure, a data receiving method includes: storing L symbol paths, where L is a natural number equal to or greater than 2; calculating L inter-symbol interference (ISI) for each of the L symbol paths; after removing the L ISI from the output of a feedforward equalizer, calculating a path metric for each of the L symbol paths; and selecting L values ​​from the calculated path metrics of the L symbol paths to update the L symbol paths.

[0010] However, the embodiments of this disclosure are not limited to those set forth herein. The above and other embodiments of this disclosure will become more apparent to those skilled in the art upon which this disclosure pertains from the detailed description of this disclosure given below. Attached Figure Description

[0011] The above and other embodiments and features of this disclosure will become more apparent from the detailed description of the various embodiments of this disclosure with reference to the accompanying drawings, in which:

[0012] Figure 1 This is a block diagram of a data transmission and reception system according to some embodiments;

[0013] Figure 2 To describe by Figure 1 A graph of a multilevel signal generated by a multilevel signal generator;

[0014] Figure 3 To show Figure 1 A graph showing the characteristics of the channel;

[0015] Figure 4 for Figure 1 A block diagram of an equalizer;

[0016] Figure 5 A block diagram illustrating the configuration of unit symbols determined on a block-by-block basis;

[0017] Figure 6 A graphic illustrating the effect of a data receiving device according to some embodiments; and

[0018] Figure 7 This is a block diagram illustrating a data receiving method according to some other embodiments. Detailed Implementation

[0019] In the following description, various embodiments of the present disclosure will be described with reference to the accompanying drawings.

[0020] Figure 1 A data transmission and reception system according to some embodiments is shown. Figure 2 To describe by Figure 1 A diagram illustrating the multilevel signals generated by the multilevel signal generator.

[0021] refer to Figure 1 The data transmission and reception system 1 may include a transmitting device TX and a receiving device RX.

[0022] The transmitting device TX can generate a multi-level signal MS in the form of a digital signal from user data UD. Furthermore, the transmitting device TX can convert the multi-level signal MS into an analog signal and transmit it to the receiving device RX via channel CH.

[0023] The transmitting device TX of the data transmitting and receiving system 1 may include a multi-level signal generator 110, a digital-to-analog converter (DAC) 120, and a driver 130. In some embodiments, the transmitting device TX may also include similar and additional components without limitation.

[0024] The multilevel signal generator 110 can generate a multilevel signal MS in the form of a digital signal from user data UD.

[0025] refer to Figure 2 A multilevel signal MS can include multiple unit symbols from US0 to USQ.

[0026] One unit symbol US is maintained during the unit period UI. In this embodiment, one unit symbol US can have M signal levels S1 to S2. M Any signal level, where M is a natural number equal to or greater than 2.

[0027] For example, in some embodiments, the multi-level signal MS may include: a unit symbol US0 having signal level S1, a unit symbol US1 having signal level S2 following the unit symbol US0, a unit symbol US2 having signal level S3 following the unit symbol US1, and a unit symbol US2 having signal level S3. M The unit symbol is USQ.

[0028] Furthermore, in some embodiments, the multi-level signal MS may include: a unit symbol US0 having signal level S2, a unit symbol US1 having signal level S1 following the unit symbol US0, and a unit symbol US1 having signal level S2 following the unit symbol US1. M The unit symbol US2 and the unit symbol US3 with signal level S1 following the unit symbol US2.

[0029] That is, a multi-level signal MS can be defined as a set of consecutive unit symbols US0 to USQ, each of which has M signal levels S1 to S2. M Any of the signal levels.

[0030] Return to reference Figure 1 The digital-to-analog converter 120 can convert a multi-level signal MS into an analog signal. The driver 130 can perform the task of sending the converted analog signal from the digital-to-analog converter 120 to the receiving device RX via the channel CH.

[0031] Analog signals can be transmitted from the transmitting device TX to the receiving device RX via the channel CH. In the signal transmitted to the receiving device RX via the channel as described above, inter-symbol interference (ISI) may exist, depending on the characteristics of the channel CH. That is, in addition to the data, specifically the unit symbol US that the transmitting device TX intends to transmit, the signal transmitted to the receiving device RX may also include noise caused by inter-symbol interference.

[0032] The receiving device RX can remove inter-symbol interference from the signal transmitted by the transmitting device TX to generate a recovered multilevel signal MSR. In the recovered multilevel signal MSR, the unit symbol US of the multilevel signal MS that the transmitting device TX intended to transmit has been recovered.

[0033] The receiving device RX of the data transmission and reception system 1 may include a conditioning block 210, an analog-to-digital converter (ADC) 220, an equalizer 230, and a calibration block 240. In some embodiments, the receiving device RX may also include similar and additional components without limitation.

[0034] The adjustment block 210 can perform analog adjustment processing on the signal received through the channel CH. The analog-to-digital converter 220 can convert the adjusted analog signal into a digital signal.

[0035] Equalizer 230 can receive the output of analog-to-digital converter 220 to generate a recovered multilevel signal MSR, from which inter-symbol interference generated in the channel CH has been removed. For this purpose, equalizer 230 may include a feedforward equalizer (FFE) 232 and a list decision feedback equalizer (List DFE) 234. This will be described in more detail later. Calibration block 240 can perform the calibration operations required to generate the recovered multilevel signal MSR.

[0036] Figure 3 Show Figure 1 The characteristics of the channel. Figure 4 Show Figure 1 The equalizer. Figure 5 This shows the configuration of determining unit symbols on a block-based basis.

[0037] In the following text, we will assume Figure 1 The channel CH has Figure 3 The features shown in the figure will be used to continue the description, but these are merely examples for explaining the technical spirit of this disclosure, and the embodiments are not limited thereto.

[0038] Figure 3 This indicates the weight or magnitude of inter-symbol interference of the post-cursor PC in the channel CH as time (in units of period UI) elapses.

[0039] When the current time point is considered to be time point 0, for example, the data received by the receiving device RX through the channel CH at the current time point may include unit symbols US transmitted from the transmitting device TX and inter-symbol interference.

[0040] When channel CH has Figure 3 When the characteristics shown are given, the data received by the receiving device RX through the channel CH at time point 0 may include, for example, inter-symbol interference of unit symbols US transmitted through the channel CH before time point D, where D is a natural number and D*UI represents the maximum delay spread.

[0041] Inter-symbol interference can include: interference equal to the weight f0 of the unit symbol US transmitted at time point-1, which is one unit period UI preceding time point 0; interference equal to the weight f1 of the unit symbol US transmitted at time point-2, which is two unit periods UI preceding time point 0; interference equal to the weight f2 of the unit symbol US transmitted at time point-3, which is three unit periods UI preceding time point 0; and interference equal to the weight f1 of the unit symbol US transmitted at time point-D. D-1 With the same amount of interference, time point -D is D unit periods UI before time point 0.

[0042] That is, the data received by the receiving device RX through the channel CH at time point 0 may include: the unit symbol US transmitted by the transmitting device TX and the interference of the unit symbol US transmitted through the channel CH during D unit periods UI.

[0043] When inter-symbol interference is removed, the unit symbol US transmitted by the transmitting device TX can be accurately determined.

[0044] refer to Figure 4 The List DFE 234 of the equalizer 230 may include path control logic 235, feedback filters 2361 to 236L, arithmetic units 2391 to 239L, path metric calculator 237, and path metric classifier 238.

[0045] When the output of equalizer 230's FFE 232 is y k At that time, y k This can be expressed as Equation 1 below.

[0046] y k =a k +f0a k-1 +f1a k-2 +…+f D-1 a k-D +n k (Equation 1)

[0047] Here, y k Let a be a signal sample received by the receiving device RX at time point k (e.g., UI = k), and a k This is the raw data of the unit symbol US transmitted by the transmitting device TX at time point k.

[0048] f k In order to be in Figure 3 The diagram shows the magnitude of inter-symbol interference or backcurve (PC) weights at each time point k, and n k For thermal noise. D is the maximum delay spread that depends on the characteristics of the channel CH.

[0049] Used from y k One method for removing inter-symbol interference includes: targeting z from which inter-symbol interference has been removed. k Perform a slice (hard decision), as shown in Equation 2 below, to calculate z. k To detect For a k The estimation results; and in calculating z k+1 Time use detection Therefore, estimate a at time point k+1 immediately following time point k. k+1 .

[0050]

[0051] In this method, at time point k, the inter-symbol interference has been removed. The unit symbol US (i.e., ) was detected and identified as being transmitted by the transmitting device TX at time point k. Figure 1 The recovered multi-level signal MSR is determined and generated. It is used to calculate the estimate at time point k+1. That is, this method is a method for generating the recovered multilevel signal MSR for each unit symbol US (e.g., using the DFE algorithm).

[0052] However, when the value detected at time point k is inaccurate (i.e., when the recovered multilevel signal MSR generated at time point k is inaccurate), the error that occurred at that time continues to affect subsequent time points k+1, k+2, etc. (error propagation).

[0053] On the other hand, to prevent such error propagation, at time point k, inter-symbol interference has been removed. The unit symbol US is detected but not identified as being transmitted by the transmitting device TX (i.e., the recovered multilevel signal MSR is not generated), and the symbol path defined by the detected value can be continuously extended for a certain period of time, such as using a maximum likelihood sequence detection (MLSD) algorithm. In this case, the detection accuracy of each unit symbol US in the receiving device RX can be increased, but as the symbol path lengthens, the amount of computation that must be performed in the receiving device RX increases exponentially, and the size of the data storage space in the receiving device RX used to assist in such computation also increases.

[0054] Therefore, the equalizer 230 according to this embodiment can use a data recovery method that can improve the detection accuracy of the unit symbol US transmitted by the transmitting device TX without excessively increasing the computational load of the receiving device RX. This will be described in more detail below.

[0055] Path control logic 235 can store L predetermined symbol paths, where L is a natural number equal to or greater than 2. Here, L is the number of symbol paths held by List DFE 234 when a unit symbol US corresponding to a block is received, which will be described in more detail below. This L can be determined, for example, to be equal to or greater than 2 and less than M. B Within the range. Here, M is the number of signal levels that a unit symbol US can have, and B is a natural number equal to or greater than 2 and is the number of unit symbols US included in a block.

[0056] L feedback filters 2361 to 236L can be used to calculate the L inter-symbol interference (ISI) of the L symbol paths respectively.

[0057] L arithmetic units 2391 to 239L can remove the L inter-symbol interferences calculated by L feedback filters 2361 to 236L from the output of the feedforward equalizer (FFE) 232 to generate z as described in Equation 2. k .

[0058] The path metric calculator 237 is provided with the outputs of L arithmetic units 2391 to 239L, and can calculate the path metric for each of the L symbolic paths.

[0059] The path metric classifier 238 can classify the path metric of each of the L symbolic paths calculated by the path metric calculator 237 based on predetermined criteria. In some embodiments, the path metric classifier 238 can classify the calculated path metrics of each of the L symbolic paths in ascending order.

[0060] The path control logic 235 can select L values ​​from the results of the path metric classifier 238, determine the estimated value at time point k, and update the L symbol paths used at time point k+1.

[0061] This operation will be described in more detail below.

[0062] First, the size of the list (the number of symbolic paths) is defined as L, and the symbolic path of each component of the list is defined as... Furthermore, the path metric calculated by the path metric calculator 237 is defined as follows:

[0063] Since each unit symbol US of the transmitting device TX can have M signal levels S1 to S2 as described above. M Any one of them, so a set of symbols transmitted by the transmitting device TX is defined as {s1, s2, ..., s...} M}

[0064] Here, when the multilevel signal generator 110 adopts, for example, PAM4, M=4 is true; when the multilevel signal generator 110 adopts, for example, PAM8, M=8 is true; and when the multilevel signal generator 110 adopts, for example, PAM16, M=16 is true. PAM stands for Pulse Amplitude Modulation.

[0065] In this embodiment, the equalizer 230 determines the unit symbol US on a block-based basis. That is, referring to... Figure 5When receiving consecutive unit symbols US from the transmitting device TX, the equalizer 230 can determine the symbol in units of B (where B is a natural number equal to or greater than 2) unit symbols US. For example... Figure 5 As shown, when B=5, equalizer 230 determines the value of the unit symbol US in a block by setting the five unit symbols US into a block. In other words, the multilevel signal MSR recovered from the five unit symbols US is generated. Since this operation is repeated on a block-by-block basis, k=1,2,…,B holds true.

[0066] Next, whenever input is received from FFE 232, the path metric calculator 237 calculates the path metric using Equation 3.

[0067]

[0068] Here, It holds true, l = 1, 2, ..., L. The outputs of L arithmetic units 2391 to 239L.

[0069] At time point k, since the path control logic 235 stores the L paths calculated at time point k-1, based on Equation 3, the path metric calculator 237 calculates M path metrics for each symbolic path, that is, a total of L×M path metrics.

[0070] Additionally, in some embodiments, whenever input is received from FFE 232, the path metric calculator 237 can calculate the path metric using the following Equation 4.

[0071]

[0072] Compared to using Equation 3, the computational complexity can be reduced when using Equation 4.

[0073] Next, the path metric classifier 238 is used to classify the L×M results calculated by the path metric calculator 237 in ascending order, and the L results with the smallest values ​​are... The path and symbol for the corresponding metric are selected.

[0074] If the selected path and symbol indices are represented as l1, l2, ..., l L ,m1,m2,…,m L Then the path metrics and list are updated by Equation 5 below and stored in path control logic 235. That is, the L symbolic paths stored in path control logic 235 are updated.

[0075]

[0076] Since the value of the unit symbol US is determined on a block-by-block basis, this process is repeated continuously until k = B. Furthermore, when k = B, a value with a minimum is found. The path and symbol for the corresponding metric are selected. The selected symbol path. As a final result, it is output and used to generate the recovered multilevel signal MSR (i.e., the value of the unit symbol US from time point k=1 to time point k=B is determined).

[0077] Figure 6 The effects of a data receiving apparatus according to some embodiments are shown.

[0078] exist Figure 6 In the diagram, after the predetermined data signal is sent, curve A shows the result of data recovery using the DFE algorithm, curve B shows the result of data recovery using the List DFE algorithm according to this embodiment, and curve C shows the result of data recovery using the MLSD algorithm.

[0079] refer to Figure 6 It can be seen that, at the same signal-to-noise ratio (Es / N0), the List DFE algorithm according to this embodiment has a significantly lower symbol error rate than the DFE algorithm. That is, the List DFE algorithm is superior to the DFE algorithm, at least in terms of the detection accuracy of unit symbols transmitted by the transmitting device.

[0080] At the same signal-to-noise ratio (Es / N0), the List DFE algorithm according to this embodiment may be inferior to the MLSD algorithm in terms of symbol error rate. However, since the List DFE algorithm only maintains L symbol paths when estimating B unit symbols US, it requires significantly less storage space and a substantial reduction in computation compared to the MLSD algorithm. In contrast, in the case of the MLSD algorithm, as the number of received unit symbols US increases, the number of symbol paths increases exponentially, causing the computational load to increase exponentially as well.

[0081] Figure 7 A data receiving method according to some other embodiments is shown.

[0082] In the following text, redundant descriptions of the above embodiments will be omitted, and the differences will be described in detail.

[0083] refer to Figure 7 In this embodiment, when transmitting from the transmitting device TX, a parity check symbol PS is generated for each of the B unit symbols US. The parity check symbol PS is added at position B+1 and then transmitted.

[0084] In some embodiments, the transmitting device TX can perform an XOR operation on B unit symbols US and generate a parity check symbol PS from the result. Furthermore, in some embodiments, the transmitting device TX can perform a Cyclic Redundancy Check (CRC) operation on the B unit symbols US and generate a parity check symbol PS from the result.

[0085] In this case, the path control logic 235 and the path metric calculator 237 repeat the process of updating the L symbol paths described above for each unit cycle UI for k = 1, 2, ..., B. That is, in this embodiment, even when k = B, the L symbol paths are updated instead of selecting the symbol path with the smallest path metric size. Furthermore, when k = B+1, the path metric calculator 237 calculates the path metric of the parity symbol PS using Equation 6 below.

[0086]

[0087] Here, p l For use The parity symbol PS is calculated in the transmitting device TX using the same method, and the equation... Established.

[0088] As a result of this calculation, path control logic 235 can enable... Lowest (minimum) As the final output, the recovered multilevel signal MRS can be generated based on this.

[0089] In summarizing the detailed description, those skilled in the art will understand that many variations and modifications can be made to the disclosed embodiments without substantially departing from the principles of this disclosure. Therefore, the disclosed embodiments are provided in a broad descriptive sense and are not intended for limiting purposes.

Claims

1. A data receiving device, the data receiving device comprising: Path control logic, configured to store L symbolic paths, where L is a natural number greater than or equal to 2; L feedback filters, wherein the L feedback filters are configured to calculate the inter-symbol interference of the L symbol paths respectively; L arithmetic units, wherein the L arithmetic units are configured to remove the L inter-symbol interferences from the output of the feedforward equalizer; and A path metric calculator, configured to receive the outputs of the L arithmetic units and calculate the path metric for each of the L symbolic paths. The path control logic is further configured to select L values ​​from the calculated path metrics of the L symbolic paths to update the L symbolic paths respectively.

2. The data receiving apparatus according to claim 1, further comprising a path metric classifier, the path metric classifier being configured to classify the calculated path metric of each of the L symbolic paths according to a predetermined criterion. in, The path control logic is further configured to select L values ​​from the results of the path metric classifier to update the L symbolic paths.

3. The data receiving device according to claim 2, wherein: The path metric classifier classifies the calculated path metrics for each of the L symbol paths in ascending order, and The path control logic is further configured to: select L path metrics with smaller values ​​from the calculated path metrics classified in ascending order to update the L symbolic paths.

4. The data receiving device according to claim 1, wherein, The path control logic receives B unit symbols and generates a multi-level signal recovered from the B unit symbols, where B is a natural number equal to or greater than 2.

5. The data receiving device according to claim 4, wherein, When the path control logic receives the B unit symbols, it selects one of the calculated path metrics of the L symbol paths and generates the recovered multilevel signal by using the unit symbols included in the symbol paths with the selected path metrics.

6. The data receiving device according to claim 1, wherein, The path metric calculator calculates the path metric for each of the L symbolic paths using the following equation: ， ， ， in, , , For the L path metrics at time point k-1, For the data receiving device at a certain time point The received signal samples, M is the number of signal levels that a unit symbol can have, S m Where D is the value of the unit symbol, and D is the maximum delay spread that depends on the channel characteristics. For at a certain point in time The magnitude of inter-symbol interference, and For the data receiving device to the data sent by the transmitting device at a time point The original data of the unit symbol sent The estimated value.

7. The data receiving device according to claim 1, wherein, The path metric calculator calculates the path metric for each of the L symbolic paths using the following equation: ， ， ， in, , For the L path metrics at time point k-1, For the data receiving device at a certain time point The received signal samples, M is the number of signal levels that a unit symbol can have, S m Where D is the value of the unit symbol, and D is the maximum delay spread that depends on the channel characteristics. For at a certain point in time The magnitude of inter-symbol interference, and For the data receiving device to the data sent by the transmitting device at a time point The original data of the unit symbol sent The estimated value.

8. The data receiving device according to claim 1, wherein, The path control logic receives B unit symbols and a parity symbol, and uses the parity symbol to generate a multi-level signal recovered from the B unit symbols, where B is a natural number equal to or greater than 2.

9. The data receiving device according to claim 8, wherein, The parity check symbol is the XOR operation data of the B unit symbols.

10. The data receiving apparatus according to claim 8, wherein, The parity check symbol is the cyclic redundancy check operation data of the B unit symbols.

11. A data receiving device, the data receiving device comprising: A feedforward equalizer, the feedforward equalizer being configured to receive multi-level signals via a channel; as well as A list-based decision feedback equalizer, configured to generate a recovered multi-level signal using the output of the feedforward equalizer. The list-based decision feedback equalizer calculates the inter-symbol interference for each of the L symbol paths, where L is a natural number equal to or greater than 2. Wherein, after removing the L inter-symbol interferences from the output of the feedforward equalizer, the list decision feedback equalizer calculates the path metric for each of the L symbol paths, and The list decision feedback equalizer generates the recovered multilevel signal by repeatedly selecting L values ​​from the calculated path metrics of the L symbol paths to update the L symbol paths.

12. The data receiving apparatus according to claim 11, wherein: The multilevel signal received through the channel includes a first block and a second block. The first block includes a first B unit symbols, and the second block includes a second B unit symbols, where B is a natural number equal to or greater than 2. After receiving the first B unit symbols included in the first block, the list decision feedback equalizer generates a first recovered multilevel signal including the first B unit symbols.

13. The data receiving apparatus according to claim 12, wherein, After generating the first recovered multilevel signal, the list decision feedback equalizer generates a second recovered multilevel signal including the second B unit symbols after receiving the second B unit symbols included in the second block.

14. The data receiving apparatus of claim 11, further comprising an analog-to-digital converter configured to convert an analog multilevel signal received through the channel into a digital signal and provide the digital signal to the feedforward equalizer.

15. A data receiving method, the data receiving method comprising: Store L symbolic paths, where L is a natural number equal to or greater than 2; Calculate the inter-symbol interference of the L symbols for each of the L symbol paths; After removing the inter-symbol interference of the L symbols, the path metric of each of the L symbol paths is calculated; and Select L values ​​from the calculated path metrics of the L symbolic paths to update the L symbolic paths.

16. The data receiving method according to claim 15, further comprising: The calculated path metric for each of the L symbol paths is classified according to a predetermined standard. The step of updating the L symbol paths includes selecting L values ​​from the classification results to update the L symbol paths.

17. The data receiving method according to claim 15, wherein, The update of the L symbol paths includes: selecting one of the calculated path metrics of the L symbol paths when B unit symbols are received, and generating a recovered multilevel signal by using the unit symbols included in the symbol paths having the selected path metrics.

18. The data receiving method according to claim 15, wherein, The update of the L symbol paths includes: receiving B unit symbols and a parity symbol, and using the parity symbol to generate a multi-level signal recovered from the B unit symbols, where B is a natural number equal to or greater than 2.

19. The data receiving method according to claim 18, wherein, The parity check symbol is the XOR operation data of the B unit symbols.

20. The data receiving method according to claim 18, wherein, The parity check symbol is the cyclic redundancy check operation data of the B unit symbols.

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