JP2003051749A - Branch metric calculation device and its calculation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a branch metric calculation device and its calculation method that use no ROM table. SOLUTION: The branch metric calculation device is provided with a first branch metric calculation circuit that calculates a first branch metric on the basis of multi-value data, a second branch metric calculation circuit that applies 45-degree rotation processing clockwise to the multi-value data and calculates a second branch metric on the basis of the obtained data, a third branch metric calculation circuit that applies 45-degree rotation processing counter clockwise to the multi-value data and calculates a third branch metric on the basis of the obtained data, and a fourth branch metric calculation circuit that applies 45-degree rotation processing clockwise to the multi-value data and calculates a fourth branch metric on the basis of the obtained data.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a branch metric calculation device and a calculation method thereof.

[0002]

2. Description of the Related Art The Viterbi decoding system is well known as a decoding system for a received signal in digital broadcasting. In particular, the Viterbi decoding method is effectively used in the case of a decoding method with a large noise margin.

Viterbi decoding is one method of decoding convolutionally encoded data. In digital broadcasting services, trellis coded modulation, which is a combination of convolutional coding and multilevel modulation, is applied. .

Such a Viterbi decoding system is disclosed in, for example, Japanese Patent Laid-Open No. 2000-313234.

FIG. 8 is a structural example of a signal flow from the transmitter 801 to the receiver 802, and FIG. 9 is a circuit diagram illustrating trellis coding.

The transmitter 801 performs Silipara conversion (11) on the information source (10) which is the data to be transmitted, performs trellis coding (12), and then performs orthogonal modulation (14),
Transmission 803 is performed by using an artificial satellite system.

The receiver 802 demodulates (1
5) Then, the demodulated data 815 is subjected to Viterbi decoding (16) to obtain the decoded information 17, so that the most probable data can be received.

Since the transmitter 801 has a large margin for noise that can be superimposed, as shown in FIG.
C is assigned to the modulation signal point so that the Euclidean distance of the original data (B1, B0) to be transmitted becomes large.
2, C1 and C0 are mapped and transmitted.

Referring to FIG. 10, the signal point arrangement is all combinations of 3-bit encoded data C2, C1, C0 at positions separated by 45 ° along the circumference of the unit circle. It is defined as a street coordinate position. Also,
Since the arrangement takes a large Euclidean distance, for example, (C2, C1, C0) = (0, 0, 1) and (C2, C
1, C0) = (1,1,0) is based on the origin 0.
They are arranged symmetrically.

An outline of the operation of the decoding device 1101 will be described with reference to FIG.

The decoding device 1101 calculates a branch metric (hereinafter abbreviated as BM) and a sector number (hereinafter abbreviated as SN) for each decoding step, and a BM / SN calculation device 40 and the above-mentioned BM. Based on
Viterbi decoding 41 for decoding the original data B0 and re-encoding block 42 for re-encoding the decoded original data B0
And a trellis decoding device 43 for decoding the original data B1 from the re-encoded data and the data obtained by delaying the SN.
And a delay device 44 for delaying SN.

Next, the BM / SN calculating means 40 will be described. For the calculation of BM / SN, the ROM table storing the conversion table data shown in FIG. 12 is used, BM00, with the received data (I, Q) as the ROM input address.
It is general to read BM01, BM10, BM11, and SN.

[0013]

However, in such a conventional BM generation method using a ROM table, the higher the received data is multi-valued data, the more accurate the BM value (bit extension) is. The more you improve, the more R
OM size becomes enormous, LSI large scale, high price,
There is a problem that it leads to an increase in current consumption.

Further, in the BM generation method described in Japanese Patent Laid-Open No. 2000-313234, the ROM table is 1 /
There was also a problem that it could only be reduced to 2.

[0015]

A branch metric calculation device of the present invention is a branch metric and multi-valued data from multi-valued data encoded by a trellis coded modulation method in which convolutional coding and multi-valued modulation are combined. A branch metric calculation device for calculating sector numbers divided along a circumference in a coordinate system of the signal arrangement, and a first branch metric calculation for calculating a first branch metric based on the multivalued data. A circuit, and rotates the multi-valued data clockwise by 45 degrees to calculate clockwise 45-degree rotation data of the multi-valued data, and based on the clockwise 45-degree rotation data, a second branch A second branch metric calculation circuit for calculating a metric, and the multivalued data are processed by rotating the multivalued data counterclockwise by 45 degrees, A third branch metric calculation circuit that calculates counterclockwise 45 ° rotation data of the data, and calculates a third branch metric based on the counterclockwise 45 ° rotation data, and the multivalued data clockwise. Rotate 90 degrees to rotate the multivalued data clockwise 90
A fourth step of calculating a degree rotation data, and calculating a fourth branch metric based on the clockwise 90 degree rotation data.
And a branch metric calculation circuit.

Furthermore, the multi-valued data of the branch metric calculation device of the present invention has a configuration of a first reception signal and a second reception signal which are orthogonal to each other.

Furthermore, in the branch metric calculation device of the present invention, the multi-valued data is rotated clockwise by 45 degrees, and a first process for subtracting the second received signal from the first received signal is performed. The branch metric calculation apparatus according to the present invention is configured to include one processing unit and a second processing unit that performs a second process of adding the first received signal and the second received signal. Rotating the value data counterclockwise by 45 degrees, second processing means for performing second processing for adding the first received signal and the second received signal,
A third processing means for performing a third processing for subtracting the first reception signal from the second reception signal,
The processing for rotating the multi-valued data in the clockwise direction by 90 degrees in the branch metric calculation device of the present invention includes a fourth processing means for performing a fourth processing for subtracting the second received signal from a 0 signal, and the first processing means. Fifth process of directly inputting received signals
This is a configuration provided with a processing means.

The branch metric calculation method applied to the branch metric calculation device of the present invention is the first received signal (hereinafter abbreviated as signal I) and the second received signal (hereinafter signal Q). (Abbreviated) regions are divided into n (n is a positive integer) regions, and the upper and lower determinations of the divided regions of the signal I and the signal Q are determined by the first determination.
At the boundary line of the signal Q and the signal I * tan
(The angle information of the first boundary line) is compared (hereinafter, the angle information indicating the boundary line number n is tan (θn)).

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described in detail below with reference to the drawings.

The embodiment of the present invention uses the symmetry of the ROM table to reduce the ROM table,
The calculation is performed using an arithmetic circuit.

First, the concept of branch metric will be described. First, the calculation of BM of BM00 will be described.

All the data in the ROM table is symmetric about the origin. Therefore, the received data is I-axis and Q-axis.
By folding back to the first quadrant with respect to the axis, the ROM table can be represented only by the area shown in FIG.

Next, the BM value is calculated.

First, the area of the received data I and the area of the received data Q is determined by the boundary line 4 shown in FIG. The upper and lower judgments are made by comparing Q and I * tan (θ4).
(Hereinafter, tan (θ4) is the angle information of the boundary line number shown in the figure. For example, in the figure, the angle information representing boundary 2 is tan (θ2).) Next, Q> = If I * tan (θ4), Q * tan
(Θ6) is compared with I, and when Q <I * tan (θ4), Q is compared with I * tan (θ2).

Next, when Q * tan (θ6)> = I,
Q * tan (θ7) is compared with I, Q * tan (θ
6) If <I, compare Q * tan (θ5) with I.

When Q * tan (θ2)> = I, Q is compared with I ″ * tan (θ3), and Q * tan (θ
2) If <I, compare Q with I ″ * tan (θ1).

From the above results and the past determination results, when Q * tan (θ7)> = I, the branch metric value becomes 7, and when Q * tan (θ7) <I,
The value of the branch metric becomes 6, and Q * tan (θ
When 5)> = I, the branch metric value is 5, when Q * tan (θ5) <I, the branch metric value is 4, and when Q> = I * tan (θ7),
The value of branch metric becomes 3, and Q <I * tan
In the case of (θ7), the branch metric value becomes 2,
When Q> = I * tan (θ5), the branch metric value becomes 1, and when Q <I * tan (θ5), the branch metric value becomes 0.
This means that the same ROM table data that is generally used has been calculated.

Next, B of BM01, BM10 and BM11
The M calculation will be described. As shown in FIGS. 12 and 13, the three ROM table data are the R of BM00.
With respect to the OM table, the table of BM01 rotates 45 ° clockwise, the table of BM10 rotates 45 ° counterclockwise, and the table of BM11 rotates 9 ° clockwise.
It is the same as that rotated by 0 °.

Therefore, the received data I and the received data Q are
The BM of each of BM01, BM10, and BM11 can be calculated by performing the following processing and the same processing as that of BM00 described above (see FIG. 6).

[0030]

[Equation 1]

Since the actual processing requires only the relative amounts of I and Q, each BM can be performed by performing only the following simple calculation.
Is calculated.

[0032]

[Equation 2]

Next, a branch metric calculation device according to the first embodiment of the present invention will be described.

FIG. 1 is a block diagram of a branch metric calculation device according to the first embodiment of the present invention.
The received data (I, Q) of the branch metric calculation device of the embodiment is assumed here to be multi-valued data of 8 bit data.

Referring to FIG. 1, the branch metric calculation apparatus 100 according to the first embodiment of the present invention uses each BM0.
0, BM01, BM10, BM11, and BM calculation circuits 101 to 104 for calculating branch metric values, and a circuit for processing (I-Q) in order to rotate each of the received data (I, Q). 105, and a circuit 106 for processing (I + Q) to perform rotation processing,
A circuit 107 for performing (-I + Q) processing for performing rotation processing and a circuit 108 for performing (0-Q) processing for performing rotation processing are provided.

Next, regarding the BM calculation circuit, the configuration of the circuit shown in FIG. 2 will be described.

I1 and Q1 are the above-mentioned data obtained by rotating the received data, I2 and Q2 are the data obtained by delaying I1 and Q1 by one step for each received data step, and I3 and Q3 are the same. The data is delayed by 2 steps.

Reference numeral 210 is the first angle information, which is a value (hereinafter referred to as angle information) at the boundary of the fourth BM, tan θ (here, represented by tan (θ4)).
Further, in the present configuration example, it is data of 8 bits, and 1 is stored in the MSB when it is larger than 45 °, and 0 is stored when it is smaller.

Similarly, reference numeral 211 is the second angle information, reference numeral 212 is the fifth angle information, reference numeral 213 is the first angle information, and reference numeral 214 is the third angle. Information, reference numeral 215 is fifth angle information, and reference numeral 216 is seventh angle information.

The BM calculation circuit 200 of the branch metric calculation device according to the first embodiment of the present invention is the selection circuit 20.
1 to 208 and 8 bit × 7 bit multipliers 220 to 2
22, data holding elements 230 to 235 for updating data in units of received data, and comparison devices 240 to 24.
2 and.

Next, the operation of the branch metric calculation device 100 according to the first embodiment of the present invention will be described.

First, in the BM calculation block configuration example of FIG. 1, as described above, the received data is subjected to the following processing and input to the BM calculation circuits 101 to 104, respectively.

[0043]

[Equation 3]

Next, the following processing is performed inside the BM calculation circuit (see FIG. 2).

At the reception data step unit time t, the selection circuit 201 outputs I if the MSB of tan (θ4) is 0.
Select 1 and if MSB is 1, select Q1.

Similarly, the selection circuit 202 uses tan (θ
If the MSB of 4) is 0, Q1 is selected, and if the MSB is 1, I1 is selected.

Next, the multiplier 220 uses the above-mentioned selected data, that is, the angle information 21 of tan (θ4).
If the MSB of 0 is 0, I1 * tan (θ4) is executed,
If the MSB of tan (θ4) is 1, Q1 * tan (θ
4) is performed.

Next, in the comparison device 240, the above-mentioned multiplication result of the multiplier 220 and the selection result of the selection circuit 202 are compared in size, and the comparison result is stored in the data holding element 230. As the data to be stored, 1 is stored when the multiplication result is larger, and 0 is stored when the multiplication result is smaller.

Next, the time (t
In +1), the selection circuit 207 selects the angle information 211 of tan (θ2) when the comparison result at the previous time t is 0, and when it is 1, the angle information 2 of tan (θ6).
Twelve selections are made.

If the MSB of the angle information selected by the selection circuit 207 is 0, the selection circuit 203 selects I2 and selects 1
If so, select Q2.

Similarly, the selection circuit 204 is the selection circuit 20.
When the MSB of the angle information selected by 7 is 0, Q2 is selected, and when it is 1, I2 is selected.

Next, the multiplier 221 calculates I2 * (angle information selected by the selection circuit 207) based on the selected data, that is, if the MSB of the angle information selected by the selection circuit 207 is 0. ) Is performed and the MSB of the angle information selected by the selection circuit 207 is 1, Q2 * (selection circuit 207
Angle information selected by.

Next, in the comparison device 241, the above-mentioned multiplication result and the selection result of the selection circuit 204 are compared in size, and the comparison result is stored in the data holding element 233. Similarly, as the data to be stored, 1 is stored when the multiplication result is larger, and 0 is stored when the multiplication result is smaller.

The data stored in the data holding element 230 is stored in the data holding element 231. Further, the data holding element 230 also performs the same processing on the data received at time (t + 1) and stores new data.

Next, the time (t
At +2), the selection circuit 208 determines that the comparison result (data holding element 231) at time t 2 before is 0, and the comparison result at time t 2 before (t +).
When the comparison result (data holding element 233) of 1) is 0,
The angle information 213 of tan (θ1) is selected.

Further, if the comparison result (data holding element 231) at time t before two times is 0 and the comparison result (data holding element 233) at time before (t + 1) is 1, tan (θ3).
214 angle information is selected.

Further, when the comparison result (data holding element 231) at time t 2 before two is 1 and the comparison result (data holding element 233) at time t + 1 before 0 is 0, the angle information tan (θ5) 215 is selected. .

Further, when the comparison result (data holding element 231) at time t 2 before two is 1 and the comparison result (data holding element 233) at time t + 1 before 2 is 1, angle information 216 of tan (θ7) is selected. .

The selection circuit 205 selects I3 when the MSB of the angle information selected by the selection circuit 208 is 0, and Q when the MSB of the angle information selected by the selection circuit 208 is 1.
Select 3.

Similarly, the selection circuit 206 selects Q3 if the MSB of the angle information selected by the selection circuit 208 is 0, and if it is 1, selects I3.

Next, the multiplier 222, based on the preselected data, that is, if the MSB of the angle information selected by the selection circuit 208 is 0, I3 * (angle information selected by the selection circuit 208) If the MSB of the angle information selected by the selection circuit 208 is 1, Q3 * (angle information selected by the selection circuit 208) is performed.

Next, in the comparison device 242, the above-mentioned multiplication result and the selection result of the selection circuit 206 are compared in size, and the comparison result is stored in the data holding element 235. Similarly, as the data to be stored, 1 is stored when the multiplication result is larger, and 0 is stored when the multiplication result is smaller.

Further, the data stored in the data holding element 231 is stored in the data holding element 232. Then, again, the data stored in the data holding element 233 is stored in the data holding element 234.

Next, a branch metric calculation device according to a second embodiment of the present invention will be described with reference to FIG.

FIG. 3 shows a branch metric calculation apparatus according to the second embodiment of the present invention, which is an example of a circuit for outputting 4 bits in order to improve the accuracy of BM and the accuracy of Viterbi decoding.

As shown in FIG. 3, the BM calculation circuit of the branch metric calculation apparatus 300 according to the second embodiment of the present invention is such that a circuit 250 for 3-bit output is further provided with a region determination circuit 350. .

Next, regarding the BM calculation circuit, the configuration of the circuit shown in FIG. 3 will be described.

I1 and Q1 are the above-mentioned data obtained by rotating the received data, I2 and Q2 are the data obtained by delaying I1 and Q1 by one step for each received data step, and I3 and Q3 are the same. 2 is delayed by 2 steps, and I4 and Q4 are similarly delayed by 3 steps.

Reference numeral 210 denotes the eighth angle information, which is a value (hereinafter, referred to as angle information) at the boundary of the eighth BM, tan θ (here, represented by tan (θ8)).
Further, in the present configuration example, it is 16-bit data, and 1 is stored in the MSB when it is larger than 45 °, and 0 is stored when it is smaller.

Similarly, reference numeral 211 is the fourth angle information, reference numeral 212 is the twelfth angle information, reference numeral 213 is the second angle information, and reference numeral 214.
Is the sixth angle information, reference numeral 215 is the tenth angle information, and reference numeral 216 is the fourteenth angle information.

The BM calculation circuit 250 of the branch metric calculation device 300 according to the second embodiment of the present invention includes selection circuits 201 to 208 and an 8-bit × 7-bit multiplier 22.
0 to 222, data holding elements 230 to 235 that update data in units of received data steps, and a comparison device 240.
˜242.

Furthermore, the BM calculation circuit 35 of the branch metric calculation device 300 according to the second embodiment of the present invention.
0 is the selection circuits 301 and 302 and the selection circuit 303.
, 8-bit × 7-bit multiplier 323, and comparison device 3
24.

Furthermore, the branch metric calculation apparatus 300 according to the second embodiment of the present invention includes a data holding element 326 that holds the output of the data holding element 232 that updates data in units of received data, and a received data step. A data holding element 327 that holds the output of the data holding element 234 that updates the data in units, a data holding element 328 that holds the output of the data holding element 235 that updates the data in units of received data steps, and the comparison device 32.
Data holding element 329 which holds the output of No. 4 of FIG.

Next, the operation of the branch metric calculation device according to the second embodiment of the present invention will be described.

First, in the diagram of the BM calculation block configuration example of FIG. 1, as described above, the same processing as that of the branch metric calculation apparatus 100 of the first embodiment of the present invention is performed on the received data, and BM is calculated. Calculation circuit 101
To 104 respectively.

Next, the following processing is performed inside the BM calculation circuit (see FIG. 3).

At the reception data step unit time t, the selection circuit 201 outputs I if the MSB of tan (θ8) is 0.
Select 1 and if MSB is 1, select Q1.

Similarly, the selection circuit 202 outputs tan (θ
If the MSB of 8) is 0, Q1 is selected, and if the MSB is 1, I1 is selected.

Next, the multiplier 220 uses the selected data described above, that is, the angle information 21 of tan (θ8).
If the MSB of 0 is 0, I1 * tan (θ8) is executed,
If the MSB of tan (θ8) is 1, Q1 * tan (θ
Perform 8).

Next, in the comparison device 240, the above-mentioned multiplication result of the multiplier 220 and the selection result of the selection circuit 202 are compared in size, and the comparison result is stored in the data holding element 230. As the data to be stored, 1 is stored when the multiplication result is larger, and 0 is stored when the multiplication result is smaller.

Next, the time (t
In +1), the selection circuit 207 selects the angle information 211 of tan (θ4) when the comparison result at the previous time t is 0, and selects the angle information 212 of tan (θ12) when it is 1. To do.

The selection circuit 203 selects I2 if the MSB of the angle information selected by the selection circuit 207 is 0, and Q if the MSB of the angle information selected by the selection circuit 207 is 1.
Select 2.

Similarly, the selection circuit 204 is similar to the selection circuit 20.
When the MSB of the angle information selected by 7 is 0, Q2 is selected, and when it is 1, I2 is selected.

Next, based on the selected data, that is, if the MSB of the angle information selected by the selection circuit 207 is 0, the multiplier 221 outputs I2 * (angle information selected by the selection circuit 207). ) Is performed and the MSB of the angle information selected by the selection circuit 207 is 1, Q2 * (selection circuit 207
Angle information selected by.

Next, the comparison device 241 compares the above-mentioned multiplication result with the selection result of the selection circuit 204, and stores the comparison result in the data holding element 233. Similarly, as the data to be stored, 1 is stored when the multiplication result is larger, and 0 is stored when the multiplication result is smaller.

Further, the data stored in the data holding element 230 is stored in the data holding element 231. Further, the data holding element 230 also performs the same processing on the data received at time (t + 1) and stores new data.

Next, the time (t
At +2), the selection circuit 208 determines that the comparison result (data holding element 231) at time t 2 before is 0, and the comparison result at time t 2 before (t +).
When the comparison result (data holding element 233) of 1) is 0,
The angle information 213 of tan (θ2) is selected.

Further, if the comparison result (data holding element 231) at time t 2 before two is 0 and the comparison result (data holding element 233) at time t before (t + 1) is 1, tan (θ6).
214 angle information is selected.

Further, when the comparison result (data holding element 231) at time t 2 before two is 1 and the comparison result (data holding element 233) at time 2 before (t + 1) is 0, tan (θ1
The angle information of 0) is selected 215.

Further, when the comparison result (data holding element 231) at time t two before the previous time is 1 and the comparison result (data holding element 233) at the previous time (t + 1) is 1, tan (θ1
216 is selected as the angle information of 4).

The selection circuit 205 selects I3 if the MSB of the angle information selected by the selection circuit 208 is 0, and selects Q3 if it is 1.

Similarly, the selection circuit 206 selects Q3 if the MSB of the angle information selected by the selection circuit 208 is 0 and I3 if the MSB of the angle information is 1.

Next, the multiplier 222, based on the preselected data, that is, if the MSB of the angle information selected by the selection circuit 208 is 0, I3 * (angle information selected by the selection circuit 208) If the MSB of the angle information selected by the selection circuit 208 is 1, Q3 * (angle information selected by the selection circuit 208) is performed.

Next, the comparison device 242 compares the above-mentioned multiplication result with the selection result of the selection circuit 206, and stores the comparison result in the data holding element 232. Similarly, as the data to be stored, 1 is stored when the multiplication result is larger, and 0 is stored when the multiplication result is smaller.

Further, the data stored in the data holding element 231 is stored in the data holding element 232. Then, again, the data stored in the data holding element 233 is stored in the data holding element 234.

Next, the time (t
+3), the operation of the selection circuit 303 will be described.

That is, in the selection circuit 303, the comparison result (data holding element 232) at time t two before two is 0, and the comparison result (data holding element 234) at time two before (t + 1).
Is 0 and the comparison result (data holding element 235) at the previous time (t + 2) is 0, the angle information 305 of tan (θ1) is selected.

Further, the comparison result (data holding element 232) at time t before two times before is 0, and the comparison result (data holding element 234) at time t before two (t + 1) is 0 and at time t before.
When the comparison result (data holding element 235) of +2) is 1, the angle information 306 of tan (θ3) is selected.

Further, the comparison result (data holding element 232) at the time t before two times before is 0, and the time before the time before (t + 1).
Is 1 and the comparison result (data holding element 235) at the previous time (t + 2) is 0.
In the case of, the angle information 307 of tan (θ5) is selected.

Further, the comparison result (data holding element 232) at the time t before two times before is 0, and the comparison result (data holding element 234) at the time before two times (t + 1) is 1 and at the time before t (t).
When the comparison result (data holding element 235) of +2) is 1, the angle information 308 of tan (θ7) is selected.

Further, the comparison result (data holding element 232) at time t two before two times is 1, and the comparison result (data holding element 234) at time two hours before (t + 1) is 0, and the time t before time (t).
When the comparison result (data holding element 235) of +2) is 0, the angle information 309 of tan (θ15) is selected.

Further, the comparison result (data holding element 232) at the time t2 before two times is 1, and the comparison result (data holding element 234) at the time two hours before (t + 1) is 0, and the time t before the time (t).
When the comparison result (data holding element 235) of +2) is 1, the angle information 310 of tan (θ13) is selected.

Further, the comparison result (data holding element 232) at the time point t before two times before is 1, and the comparison result (data holding element 234) at the time point before two times (t + 1) is 1, and at the time point before t (t).
When the comparison result (data holding element 235) of +2) is 0, the angle information 311 of tan (θ11) is selected.

Then, the comparison result (data holding element 232) at the time t before two times before is 1 and the comparison result (data holding element 234) at the time before two times (t + 1) is 1, and at the time before (t + 2). When the comparison result (data holding element 235) is 1, the angle information 312 of tan (θ9) is selected.

The selection circuit 301 selects I4 if the MSB of the angle information selected by the selection circuit 303 is 0, and Q if the MSB of the angle information selected by the selection circuit 303 is 1.
Select 4.

Similarly, if the MSB of the angle information selected by the selection circuit 303 described above is 0, the selection circuit 302 outputs Q4.
And the MSB of the angle information selected by the selection circuit 303.
If is 1, I4 is selected.

Next, based on the above-mentioned selected data, that is, if the MSB of the angle information selected by the selection circuit 303 is 0, the multiplier 323 outputs I4 * (angle information selected by the selection circuit 208). ) Is performed and the MSB of the angle information selected by the selection circuit 303 is 1, Q4 * (selection circuit 208
Angle information selected by.

Next, the comparison device 324 compares the above-mentioned multiplication result with the selection result of the selection circuit 302, and stores the comparison result in the data holding element 329. Similarly, as the data to be stored, 1 is stored when the multiplication result is larger, and 0 is stored when the multiplication result is smaller.

Further, the data stored in the data holding element 232 is stored in the data holding element 326. Also,
The data stored in the data holding element 234 is stored in the data holding element 327. Then, again, the data stored in the data holding element 235 is transferred to the data holding element 32.
Store in 8.

The angle information tan (θ shown in FIG.
1) to angle information tan (θ7) or the angle information tan (θ1) to angle information tan (θ15) shown in FIG.
It can be easily and arbitrarily changed.

Therefore, even if the transmission system is changed, it can be changed efficiently and suitably.

[0112]

As described above, the branch metric calculation apparatus of the present invention performs the BM calculation to reduce the size of the LSI while avoiding the decrease in accuracy and processing speed, that is, the ROM table is set to 1 / 8 or less, and there is an effect that a low price and a low current consumption can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram of a branch metric calculation device according to a first embodiment of this invention.

FIG. 2 is an example of a branch metric calculation circuit of the branch metric calculation device according to the first embodiment of the present invention.

FIG. 3 is an example of a branch metric calculation circuit of a branch metric calculation device according to a second embodiment of the present invention.

FIG. 4 is a diagram showing a compact body of a ROM table.

FIG. 5 is a diagram illustrating calculation of a branch metric.

FIG. 6 is a diagram illustrating a rotation process of the branch metric calculation device according to the first embodiment of this invention.

FIG. 7 is a diagram illustrating the calculation of a branch metric value in the case of 16 values.

FIG. 8 is a configuration example of a signal flow from a transmitter 801 to a receiver 802.

FIG. 9 is a circuit diagram illustrating trellis encoding.

FIG. 10 is a diagram showing a configuration example of signal points.

FIG. 11 is a diagram illustrating a configuration example of a decoder.

FIG. 12 is a diagram showing a configuration example of a ROM.

FIG. 13 is a diagram showing branch metric values centered on ROM origin coordinates.

[Explanation of symbols]

10 information sources 11 Siripara conversion 12 Convolutional coding 13 Mapping 14 Quadrature modulation 15 demodulation 16 Viterbi decoding 17 Decryption information 20, 21, 22, 23, 24, 25 Delay element 26,27 Exclusive OR 40 BM / SN calculation device 41 Viterbi decoding 42 Re-encoding block 43 Trellis Decoding Device 44 Delay device 100 Branch metric calculation device 101, 102, 103, 104 BM calculation circuit 105, 106, 107, 108 Received signal processing circuit 200 BM calculation circuit

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04L 27/22 H04N 5/44 Z 27/38 H04L 27/00 G H04N 5/44 27/22 F F term (Reference) 5B001 AA10 AA13 AC02 5B056 BB00 HH00 5C025 DA01 5J065 AA01 AB01 AC02 AD10 AF03 AG05 AH03 AH06 AH09 5K004 AA05 AA08 FG02 JG01

Claims (9)

[Claims] 1. A multi-valued data encoded by a trellis coded modulation method that combines convolutional coding and multi-valued modulation, and is divided along a circumference in a coordinate system of a branch metric and a signal arrangement of the multi-valued data. A branch metric calculation device for calculating a sector number, the first branch metric calculation circuit calculating a first branch metric on the basis of the multi-valued data, and the multi-valued data clockwise by 45 degrees. A second branch metric calculation circuit that performs rotation processing to calculate clockwise 45 degree rotation data of the multi-valued data, and calculates a second branch metric based on the clockwise 45 degree rotation data; Rotate multi-valued data counterclockwise by 45 degrees,
Counterclockwise 45 ° rotation data of the multi-valued data is calculated, and based on the counterclockwise 45 ° rotation data, a third
A third branch metric calculation circuit for calculating a branch metric of the multivalued data, and rotating the multivalued data clockwise by 90 degrees to calculate clockwise 90 degree rotation data of the multivalued data. And a fourth branch metric calculation circuit that calculates a fourth branch metric based on the rotation data. 2. The multi-valued data are first orthogonal to each other.
2. The branch metric calculation device according to claim 1, wherein the branch metric calculation device and the second reception signal. 3. The first processing means for performing a first processing of subtracting the second reception signal from the first reception signal in the processing of rotating the multi-valued data clockwise by 45 degrees, and the first processing means. 3. The branch metric calculation device according to claim 1, further comprising a second processing unit that performs a second process of adding a received signal and the second received signal. 4. A second processing means for performing a second processing for adding the first reception signal and the second reception signal to the counterclockwise rotation of 45 degrees of the multi-valued data, Second
3. A third processing means for performing a third process of subtracting the first received signal from the received signal of 1.
The described branch metric calculation device. 5. The fourth processing means for performing a fourth processing of subtracting the second received signal from a zero value for directly rotating the multi-valued data by 90 degrees clockwise and the first received signal directly 5. A fifth processing means for processing inputting, comprising:
The branch metric calculation device described in 2, 3 or 4. 6. A branch metric calculation method applied to the branch metric calculation device according to claim 1, wherein the first received signal (hereinafter abbreviated as signal I) and the first received signal are used. A region of two reception signals (hereinafter abbreviated as signal Q) is divided into n (n is a positive integer) regions, and upper and lower determinations of the divided regions of the signal I and the signal Q are performed. , And the signal I * tan (angle information of the first boundary line) is compared (hereinafter, the angle information indicating the boundary line number n is ta.
n (θn)) branch metric calculation method. 7. When the signal Q is greater than or equal to the signal I * tan (θ4), the signal Q * tan (θ6) is compared with the signal I. When the signal Q is less than the signal I * tan (θ4), Q is compared with the signal I * tan (θ2). Next, when the signal Q * tan (θ6) is equal to or greater than the signal I, the signal Q * tan (θ7) is compared with the signal I to obtain the signal Q.
If * tan (θ6) is less than the signal I, the signal Q * tan
(Θ5) is compared with the signal I. If the signal Q * tan (θ2) is equal to or more than the signal I, at the time (t + 1) of the received data step unit of the signal I (hereinafter, this signal is referred to as the signal I2). , Signal Q and signal I2 *
tan (θ3) and compare the signal Q * tan (θ
If 2) is less than signal I, signal Q and signal I2 * tan
The branch metric calculation method according to claim 6, wherein a comparison with (θ1) is performed. 8. A first selection circuit and a second selection circuit for selecting the first reception signal or the second reception signal according to the angle information.
Selection circuit, a multiplier that multiplies the output of the first selection circuit and the angle information, a comparator that compares the output of the multiplier and the output of the second selection circuit, and the first and A data holding element that updates data in units of second received data steps.
6. The branch metric calculation device according to 6 or 7. 9. The branch metric calculation device according to claim 8, wherein the multiplier has a configuration of 8 bits × 7 bits.