JP5428387B2 - Data transmission method and system, and data reception method and apparatus - Google Patents

Description

  The present invention relates to a data transmission method and system for estimating a transmission data sequence using a nonlinear equalization technique such as Maximum Likelihood Sequence Estimation (MLSE), which is a representative nonlinear equalization technique, and data reception The present invention relates to a method and an apparatus.

  2. Description of the Related Art Conventionally, a signal receiving apparatus is known in which a transmission signal sequence is estimated from a received signal sequence based on the principle of MLSE, thereby improving reception performance against waveform distortion that occurs during transmission (Patent Document 1, Non-Patent Document 1, 2).

JP 2002-118473 A

John G. Proakis, "Digital Communications, Fourth Ed.," New York, McGraw-Hill, 2001 Joan M. Gen, et al., "ISI Mitigation Capability of MLSE Direct-Detection Receivers," IEEE Photonics Technology Letters, vol. 20, No. 8, pp.656-658, 2008

  The methods described in Non-Patent Document 1 and Patent Document 1 are methods for improving reception performance against waveform distortion caused by delayed waves. For example, temporally like inter symbol interference (ISI: Inter Symbol Interference) due to band limitation. The effect is limited when the subsequent data string also contributes to waveform distortion.

  On the other hand, the method described in Non-Patent Document 2 is based on the premise that one symbol that moves back and forth in time contributes to waveform distortion. Therefore, when the range covered by intersymbol interference is unknown or when the range covered by intersymbol interference is asymmetric on the time axis (for example, when the preceding 1 symbol and the succeeding 3 symbols contribute as interference components) The effect is limited when the range of interference varies with time due to a change in transmission path conditions.

  Optical fiber transmission lines and wireless transmission lines not only have various deterioration factors, but also vary greatly in time, and a method for improving reception performance effective for such transmission lines is desired.

  The present invention provides a data transmission method and system, and a data reception method and apparatus capable of ensuring high estimation accuracy of a transmission data sequence for a transmission path that has various deterioration factors and greatly varies with time. The purpose is to present.

The data transmission method according to the present invention includes an output step of outputting transmission data to a transmission line following a reference signal composed of a PN code sequence, a clock recovery step of recovering a clock from a reception signal from the transmission line, and the clock the received signal was digitized at multivalue conversion step and the reception processing characteristics determining step of determining a reception processing characteristics from the portion for housing the reference signal of the multi-level signal by the conversion step of outputting the multi-level signal in accordance with And a reception processing step of reproducing the transmission data from a portion of the multilevel signal accommodating the transmission data of the multi-level signal according to the reception processing characteristic determined in the reception processing characteristic determination step. Be

A data transmission system according to the present invention comprises: a data transmission apparatus comprising means for generating a reference signal composed of a PN code sequence ; and a multiplexing means for multiplexing transmission data following the reference signal and outputting the multiplexed data to a transmission line A data transmission system comprising a data receiving device for reproducing the transmission data from an input signal from the transmission line, wherein the data receiving device reproduces a clock from the input signal from the transmission line; The A / D converter that digitizes the input signal from the transmission path according to the clock and outputs a multi-value signal, and the reference signal of the multi-value signal that is generated by the A / D converter In accordance with the reception processing characteristic determining means for determining the reception processing characteristic from the portion to be accommodated, and according to the reception processing characteristic determined by the reception processing characteristic determination means, Receiving processing means for reproducing the transmission data from a portion of the multilevel signal generated by the conversion means that accommodates the transmission data.

A data reception method according to the present invention includes a reference signal composed of a PN code sequence , an input step in which transmission data subsequent thereto is input from a transmission path, a clock recovery step of recovering a clock from an input signal by the input step, an input signal by the input step to digitize multi-valued according to the clock, a conversion step of outputting the multi-level signal, received to determine the reception processing characteristics from the portion for housing the reference signal of the multi-level signal by the conversion step A processing characteristic determination step, and a reception processing step of reproducing the transmission data from a part accommodating the transmission data of the multilevel signal by the conversion step according to the reception processing characteristic determined in the reception processing characteristic determination step. It is characterized by having.

A data receiving apparatus according to the present invention includes a reference signal composed of a PN code sequence , input means for transmitting transmission data subsequent thereto from a transmission path, clock recovery means for recovering a clock from an input signal by the input means, A / D conversion means for digitizing the input signal by the input means in accordance with a clock and outputting a multi-value signal, and the reference signal for the multi-value signal generated by the A / D conversion means are accommodated. A reception processing characteristic determining unit for determining a reception processing characteristic from the portion, and the transmission data of the multilevel signal generated by the A / D conversion unit according to the reception processing characteristic determined by the reception processing characteristic determination unit. Receiving processing means for reproducing the transmission data from the accommodating portion.

  According to the present invention, even in a data transmission system in which various degradation factors such as band limitation and intersymbol interference coexist and the effect of each factor fluctuates with time, reception is performed with reception processing characteristics corresponding to the immediately preceding transmission state. Since transmission data is estimated from a signal, higher estimation accuracy can be secured.

It is a schematic block diagram of one Example of this invention. It is an example of a waveform of a present Example. It is an example of amplitude change of a received signal with respect to a 3-bit signal 100,000. It is a timing chart in the data receiver of a present Example. It is an operation | movement flowchart of the parameter determination apparatus which determines the MSLE process parameter of a present Example. It is a calculation result table | surface of the average value calculated with respect to 3 bit value in a parameter determination apparatus, and dispersion | distribution. It is a trellis figure (k = 3) which shows the transition information of data from the combination of the data of 2 time.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows a schematic block diagram of a data transmission system using one embodiment of the present invention.

  The data transmission device 10 transmits data Dt to the data reception device 20 via the transmission path 16. The transmission line 16 is a transmission line whose data transmission characteristics fluctuate with time, such as intersymbol interference, multiple reflection, and waveform distortion due to dispersion, for example, an optical transmission line such as an optical fiber, and a wireless transmission line of a mobile communication system. . In an optical fiber transmission line, for example, fluctuations in polarization due to temperature, wind, or the like cause large waveform fluctuations particularly in a high-speed data transmission line.

  The data transmitting apparatus 10 monitors the deterioration state of the transmission line 16 and transmits a reference signal for determining the optimum reception processing characteristic according to the deterioration state immediately before the transmission data Dt. In this embodiment, a PN code sequence is employed as the reference signal. That is, the PN code generator 12 generates a fixed-length, for example, 127-bit PN code sequence for each fixed-length data Dt to be transmitted. The multiplexer 14 arranges the fixed-length PN code sequence from the PN code generator 12 prior to the fixed-length transmission data Dt. In other words, the data transmission device 10 accommodates the transmission data Dt in a data frame having a PN code sequence as a header and outputs the transmission data Dt to the transmission path 16.

  In the data reception device 20, the reception signal input from the transmission path 16 is input to an A / D (analog / digital) converter 22 and a clock recovery device 24. The clock recovery device 24 recovers the clock from the received signal and supplies the recovered clock to the A / D converter 22 as a sampling clock. The A / D converter 22 multi-digitizes the received signal from the transmission line 16 into 4 to 8 bits according to the recovered clock from the clock recovery device 24. Although details will be described later, the data reception device 20 determines parameters for MLSE processing using the PN code sequence portion of the multilevel signal output from the A / D converter 22, and transmits the determined parameters. Data Dt is estimated.

  FIG. 2 shows a waveform example in the data receiving apparatus 20. 2A shows a binary value of transmission data, and FIG. 2B shows a transmission signal waveform corresponding to the transmission data shown in FIG. FIG. 2C shows a waveform of a signal received by the data receiving device 20. The transmission signal waveform shown in FIG. 2B is deteriorated as shown in FIG. 2C in the process of propagating through the transmission line 16. FIG. 2D shows the result of digitizing the received signal waveform shown in FIG. 2C by the A / D converter 22. That is, FIG. 2 (d) shows a multilevel signal output from the A / D converter 22. FIG. 2 (e) shows the result of estimating transmission data Dt by applying MLSE processing to the multilevel signal shown in FIG. 2 (d), and FIG. 2 (f) shows the binary waveform shown in FIG. 2 (d). Indicates the binary value for. The binary value sequence shown in FIG. 2 (f) is received data.

  FIG. 3 shows an example of reception levels for the 3-bit transmission bit strings 100 and 000. The horizontal axis indicates time, and the vertical axis indicates the amplitude level. If the deterioration in the transmission path becomes severe, the reception level will vary more greatly.

  FIG. 4 shows a timing chart of waveform examples after the A / D converter 22. FIG. 4A shows the timing of the multilevel signal output from the A / D converter 22. PN (i) indicates the i-th PN code sequence, and D (i) indicates the i-th received data D. When there is no transmission error, the reception data D (i) matches the transmission data Dt (i).

  The multi-value waveform signal (FIG. 4A) output from the A / D converter 22 is input to the buffer memory 26 and the PN code detector 28. The buffer memory 26 temporarily stores at least the multilevel signal output from the A / D converter 22 for the time required for the PN code detector 28 to detect the PN code sequence preceding the data portion of the data frame.

  The PN code detection device 28 detects a reference signal portion consisting of a PN code sequence from the multilevel signal (FIG. 4A) output from the A / D converter 22, and the PN code detection signal is stored in the buffer memory 26 and This is supplied to the switch control device 30. FIG. 4B shows a PN code detection signal. In the waveform example shown in FIG. 4A, the PN code portions PN (0) to PN (3) and the data portions D (0) to D (2) of the data frame in the buffer memory 26 are detected by the PN code detection signal. Can be identified.

The buffer memory 26 sequentially outputs the stored multi-level signal to the switch 32 in accordance with the PN code detection signal from the PN code detection device 28. A PN code portion, if there is a gap between the data frames preceding this, when reading from the buffer memory 26, so that this gap is discarded.

  The switch 32 supplies the PN code portions PN (0) to PN (3) of the output data of the buffer memory 26 under control of the switch control device 30 from the terminal A to the parameter determination device 34, and the data portion D (0 ) To D (2) are supplied from the terminal B to the buffer memory 36. FIG. 4C shows a multilevel signal read from the buffer memory 26, and FIG. 4D shows a switching control signal for the switch 32. In FIG. 4D, PN indicates connection to the terminal A, and DATA indicates connection to the terminal B. As can be seen from FIGS. 4C and 4D, the switch control device 30 follows the PN code detection signal from the PN code detection device 28 (FIG. 4B) from the buffer memory 26 to the PN code portion PN (0 ) To PN (3) are output at the timing when the switch 32 is connected to the terminal A, and at the timing when the data portions D (0) to D (3) are output from the buffer memory 26, the switch 32 is connected to the terminal B. . As a result, among the received signals, a multilevel signal indicating the PN code portions PN (0) to PN (3) is input to the parameter determination device 34, and the multilevel signal indicating the data portions D (0) to D (3) is input. Is input to the buffer memory 36.

  The PN code portions PN (0) to PN (3) and the data portions D (0) to D (3) are separated by the buffer memory 26, the switch control device 30 and the switch 32, and the parameter determination device 34 and the buffer memory are respectively separated. It is obvious that the function distributed to 36 can be realized by a random access memory or FIFI (First-In First-Out) memory and a memory control device for controlling the reading position.

  The switch control device 30 also supplies a switch control signal (FIG. 4D) for controlling the switch 32 to the parameter determination device 34. The parameter determination device 34 can know the timing at which the PN code portion is input from the switch 32 by the switch control signal from the switch control device 30, and the PN code portions PN (0) to PN (3) from the switch 32. Capture multilevel signals. The PN code generator 38 generates a PN code sequence on the same basis as the PN code generator 12 of the data transmitter 10. Then, the parameter determination unit 34 refers to the PN code sequence from the PN code generation unit 38, and performs optimum processing for removing intersymbol interference on the captured PN code part (multilevel signal) by a method described later. Determination position and path metric calculation parameters for MLSE processing are determined. When the determination position and the MLSE processing parameter are determined, the parameter determination device 34 sets the determined determination position and MLSE processing parameter in the MLSE processing device 40 and instructs the MLSE processing device 40 to start the MLSE processing.

  The buffer memory 36 is provided to compensate for the time delay of the parameter determination operation in the parameter determination device 34. The MLSE processing device 40 sequentially fetches the multi-value waveform signal from the buffer memory 36 in accordance with the start command from the parameter determining device 34, and uses the determination position and the parameter for MLSE processing from the parameter determining device 34 to transmit data by MLSE processing. Dt is estimated (reproduced). That is, the MLSE processing device 40 performs binary discrimination on the multilevel signals of the data portions D (0) to D (3) stored in the buffer memory 36. FIG. 4F shows the estimation results Dr (0), Dr (1), Dr (2) by the MLSE processor 40. The estimation results Dr (0), Dr (1), Dr (2),... Are supplied to the subsequent apparatus as received data.

  In the case of a PN code sequence, the determination position and MLSE parameter determination method in the parameter determination device 34 will be described in detail. FIG. 5 shows an operation flowchart of the parameter determination device 34.

  The parameter determination device 34 takes in the PN code sequence (multilevel signal) from the switch 32 in accordance with the switch control signal from the switch control device 30 (S1).

Cycle through successive k bits {a ₁ , a ₂ ,..., A _k } from {0, 0,..., 0} to {1, 1,. , S6), Steps S3 and S4 are executed for each combination of k bits {a ₁ , a ₂ ,..., A _k }.

First, from the captured PN code sequence (multi-level signal), a signal sequence {r _1j , r _2j ,..., R _kj } corresponding to a _k- bit sequence {a ₁ , a _{2 ,.} j = 1, 2,..., m) are extracted (S3). Here, m indicates the number of times that consecutive k bits {a ₁ , a ₂ ,..., A _k } appear in the PN code sequence attached to the head of the data frame.

Then, the influence of intersymbol interference is calculated based on the signal sequence {r _1j , r _2j ,..., R _kj } (where j = 1, 2,..., M) extracted in step S3. To do. First, the average for the p-th (1 ≦ p ≦ k) signal level under the condition that the first to k-th signal bit strings are {a ₁ , a ₂ ,..., A _k }. u and variance v are calculated (S4).

で算出される。 In the following, the average u is expressed as u (a ₁ ... A _p-1 xa _{p + 1} ... A _k , a _p ), and the variance v is expressed as v (a ₁ ... A _p−1 xa _{p + 1.} -It describes with _ak , _ap ). When p = 1, the average u and the variance v from the signal sequence extracted in step S3 are expressed by the following equations:

Is calculated by

により計算される。 As an example, it is assumed that k = 3 and a 7-stage (127 bits) PN sequence is included for two periods as a PN code sequence. In this case, since the 3-bit sequence {a ₁ , a ₂ , a ₃ } appears 16 times in one cycle of the 7-stage PN sequence, m = 32. For example, under the condition that the transmission bit string is “000”, the average u (x00,0) and variance v (x00,0) of the signal level for the first bit are expressed by the following equations:

Is calculated by

  The parameter determination device 34 stores the average value u and the variance v calculated in this way in a list form. FIG. 6 is an example of a list of average values u and variances v stored in the parameter determination device 34.

によりパラメータＱｐを、ｐ＝１からｋまで順に計算し、Ｑｐの値が最大となるｐを求める。これにより、受信信号の１レベルの分布と０レベルの分布が最も分離するビット位置ｐ（１≦ｐ≦ｋ）が決定する。 When the calculation of the average value u and the variance v is finished up to k bits {a ₁ , a ₂ ,..., a _k } = {1, 1,..., 1} (S5), the obtained average value u From the variance v, the bit position p at which the degree of separation of the 1-level and 0-level signals among the k bits is maximized is calculated (S7). This is equivalent to evaluating the degree of separation of 1-level and 0-level signals for the p-th bit. The higher the degree of separation, the larger the eye opening. Specifically, for the average value u and the variance v calculated in Equation 2,

Thus, the parameter Qp is calculated in order from p = 1 to k, and p that maximizes the value of Qp is obtained. Thereby, the bit position p (1 ≦ p ≦ k) at which the 1-level distribution and the 0-level distribution of the received signal are most separated is determined.

  The parameter determination device 34 sets the obtained (p, u, v) in the MLSE processing device 40 as a parameter of the MLSE processing, and starts the binary discrimination processing of the received data portion (multi-value signal). (S8).

  The MLSE processing device 40 uses the parameters (p, u, v) from the parameter determination device 34 and applies a Viterbi algorithm to the received data (multi-value signal) stored in the buffer memory 36 to receive the received data (multi-value data). Signal) is estimated or binary discriminated. The Viterbi algorithm is described in detail in “The Viterbi algorithm” (GD Forney, Jr., Proc. IEEE, vol. 61, pp. 268-278, (1973)).

  The MLSE processing device 40 sequentially reads the received data (multilevel signal) stored in the buffer memory 36 in accordance with the processing start signal from the parameter determination device 34. By using the trellis diagram indicating the data transition information for 2k-1 states for the determination position p for the k-bit unit described above, it is possible to best estimate the transmission bit based on the received signal by the Viterbi algorithm. . As an example, FIG. 7 shows a trellis diagram when k = 3.

で表される。 In the trellis diagram, a branch metric is calculated for each branch (line segment in FIG. 7). For example, when k = 3 and p = 1 and the data reception level is r, the branch metric M0 from state 00 to state 00 and the branch metric M1 from state 00 to state 10 are

It is represented by

  Next, branch metrics are cumulatively added for all paths indicating state transitions up to a state at a certain time, a path having the maximum cumulative value is selected, and a path metric value is stored. The path thus selected is the most probable path and is called a survival path.

  The above processing is performed every time, and a final surviving path is searched. The survival path thus determined represents the most probable transmission data sequence estimated based on the received signal sequence. The MLSE processing device outputs the surviving paths thus determined as estimated reception data Dr (0), Dr (1), Dr (2),.

  In this embodiment, the transmission characteristic of the transmission line is monitored, and a reference signal for determining the optimum reception characteristic is transmitted prior to the transmission data. On the receiving side, the reception processing characteristic, concretely, is determined by the received reference signal. Controls the MLSE processing characteristics. By adopting an N-stage PN code sequence as a reference signal, the degree of separation of 1-level and 0-level signals for each bit position is calculated with the same accuracy for an arbitrary number of bits of N-1 bits or less. It becomes possible. For this reason, there is also an advantage that it is possible to flexibly cope with the change of the value of k within a range of N−1 or less without changing the reference signal portion in accordance with the range where the intersymbol interference reaches.

  The present invention can be applied to a data transmission system in which various deterioration factors such as wave propagation and intersymbol interference are mixed and the state of the transmission path varies with time. More specifically, the present invention can be applied to an optical fiber transmission system in which a signal waveform is distorted due to the influence of chromatic dispersion or polarization mode dispersion. Since the polarization state of the optical signal changes from moment to moment, the influence of distortion due to polarization mode dispersion also varies with time. The present invention is also applicable to a mobile communication system in which the influence of distortion due to multipath interference (MPI) changes every moment.

  Although the invention has been described with reference to specific illustrative embodiments, various modifications and alterations may be made to the above-described embodiments without departing from the scope of the invention as defined in the claims. This is obvious to an engineer in the field to which the present invention belongs, and such changes and modifications are also included in the technical scope of the present invention.

10: Data transmitter 12: PN code generator 14: Multiplexer 16: Transmission line 20: Data receiver 22: A / D (analog / digital) converter 24: Clock recovery device 26: Buffer memory 28: PN code detection Device 30: Switch control device 32: Switch 34: Parameter determination device 36: Buffer memory 38: PN code generator 40: MLSE processing device

Claims (10)

An output step of outputting transmission data to the transmission line following the reference signal consisting of a PN code sequence ;
A clock recovery step of recovering a clock from a received signal from the transmission line;
A conversion step of digitizing the received signal in a multi-value according to the clock and outputting a multi-value signal;
A reception processing characteristics determining step of determining a reception processing characteristics from the portion for housing the reference signal of the multi-level signal by the conversion step,
A reception processing step of reproducing the transmission data from a portion of the multilevel signal accommodating the transmission data of the multi-level signal according to the reception processing characteristic determined in the reception processing characteristic determination step. Data transmission method. The reception processing step estimates the transmission data from the transmission data portion of the multilevel signal by the conversion step by maximum likelihood sequence estimation (MLSE),
The data transmission method according to claim 1, wherein the reception processing characteristic determination step determines a bit position and a parameter of MLSE processing as the reception processing characteristic. 3. The data transmission method according to claim 1, wherein the output step outputs the data frame in which the reference signal is accommodated in the header portion and the transmission data is accommodated in the data portion to the transmission path. Means for generating a reference signal composed of a PN code sequence , and a data transmission device comprising a multiplexing means for multiplexing transmission data following the reference signal and outputting the multiplexed data to a transmission line;
A data transmission system comprising a data receiving device for reproducing the transmission data from an input signal from the transmission path,
The data receiving device is
A clock recovery means for recovering a clock from an input signal from the transmission line;
A / D conversion means for digitizing an input signal from the transmission line according to the clock in a multi-value and outputting a multi-value signal;
A reception processing characteristic determining unit that determines a reception processing characteristic from a portion that accommodates the reference signal of the multilevel signal generated by the A / D conversion unit;
A reception processing means for reproducing the transmission data from a portion accommodating the transmission data of the multilevel signal generated by the A / D conversion means according to the reception processing characteristics determined by the reception processing characteristic determination means; A data transmission system comprising: The reception processing means is an MLSE processing means for estimating the transmission data from the data portion of the multilevel signal generated by the A / D conversion means by maximum likelihood sequence estimation (MLSE).
5. The data transmission system according to claim 4 , wherein the reception processing characteristic determining means is means for determining a bit position and a parameter of MLSE processing as the reception processing characteristic. 6. The data transmission system according to claim 4 , wherein the multiplexing means accommodates the reference signal in a header part and outputs a data frame containing the transmission data in a data part to the transmission line. A reference signal composed of a PN code sequence, and an input step in which transmission data following the reference signal is input from the transmission line;
A clock recovery step of recovering a clock from the input signal by the input step;
A conversion step of digitizing the input signal by the input step according to the clock in a multi-value and outputting a multi-value signal;
A reception processing characteristics determining step of determining a reception processing characteristics from the portion for housing the reference signal of the multi-level signal by the conversion step,
A reception processing step of reproducing the transmission data from a portion of the multilevel signal accommodating the transmission data of the multi-level signal according to the reception processing characteristic determined in the reception processing characteristic determination step. Data reception method. The reception processing step estimates the transmission data from the transmission data portion of the multilevel signal by the conversion step by maximum likelihood sequence estimation (MLSE),
The data reception method according to claim 7 , wherein the reception processing characteristic determination step determines a bit position and a parameter of MLSE processing as the reception processing characteristic. A reference signal composed of a PN code sequence, and input means for transmitting transmission data subsequent thereto from the transmission path;
Clock recovery means for recovering a clock from an input signal by the input means;
A / D conversion means for digitizing the input signal by the input means according to the clock in a multi-value and outputting a multi-value signal;
A reception processing characteristic determining unit that determines a reception processing characteristic from a portion that accommodates the reference signal of the multilevel signal generated by the A / D conversion unit;
A reception processing means for reproducing the transmission data from a portion accommodating the transmission data of the multilevel signal generated by the A / D conversion means according to the reception processing characteristics determined by the reception processing characteristic determination means; A data receiving apparatus comprising: The reception processing means is an MLSE processing means for estimating the transmission data from the data portion of the multilevel signal generated by the A / D conversion means by maximum likelihood sequence estimation (MLSE).
10. The data receiving apparatus according to claim 9 , wherein the reception processing characteristic determination unit is a unit that determines a bit position and a parameter of MLSE processing as the reception processing characteristic.

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