JPH0234553B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a received signal discrimination method when demodulating a received signal in a modulator/demodulator in a communication system.

[Technical Background] For example, in a communication system that integrates a CPU 10 and a terminal device 40 (hereinafter referred to as DTE 40) as shown in FIG.
Modulators 20a, 30a and demodulator 20 on each side
b, 30b, and modulators 20 and 30
(hereinafter referred to as modems 20 and 30), and the CPU
Modulators 20a and 30a modulate carrier waves based on information from 10 or information from DTE 40,
For example, amplitude phase modulation is performed on the DTE40 side or
The received wave is sent to the CPU 10 side and the received wave is sent to the demodulator 30.
a, 20a demodulates and the DTE 40 or CPU 10 recognizes the information from the CPU 10 or the information from the DTE 40 based on the demodulated information.

By the way, when information from the CPU 10 or DTE 40 is output at 9600 bits/second, which is the general high-speed mode, the modulation speed specified in the communication line is 2400 times/second, so it is output as 4-bit parallel data. In this case, there are 16 types of information, that is, modulation information. Therefore, on the transmitting side, the above-mentioned
16 transmission signal points corresponding to 16 types of modulation information are arranged, and on the receiving side, as shown in Fig. 2, for example, a receiving signal point P corresponding to the above transmission signal points specified on the receiving side is arranged. are doing. Here, the received signal point P1 expresses amplitude information by, for example, its X coordinate value X1, and expresses phase information by an angle θ1 formed between the X axis and OP1.

In such a communication system, for example, a carrier wave modulated based on modulation information expressed by a transmission signal point corresponding to reception signal point P1 is distorted within the line, and the carrier wave (reception wave) is changed to the reception signal point on the reception side. When demodulated as P2, this received signal point P2
must be determined to be the received signal point P1. Therefore, the reception plane is divided into divided areas E (determination plane) corresponding to the transmission signal points,
For example, a received signal determination method is required in which all received signal points within divided area E1 are determined to be received signal points P1, and furthermore, high-speed data transfer, such as 14,400 bits/second, is required for receiving signal points (transmission signal points). In realizing a communication system with 128 or 256 signal points as shown in Figure 3, for example,
A more efficient determination method is desired.

[Prior art and problems] The simplest method of this type assigns a number to each divided area E obtained by dividing the reception plane corresponding to the transmission signal point. Considering that each of the coordinate values X and Y is expressed as a 4-bit numerical value, there are a total of 1024 received signal points on the reception plane considering their positive and negative areas, so the received signal of these 1024 points A table is provided in which the number of the divided area E to which the received signal point belongs is assigned to each point, and the table is searched based on the received signal point obtained by demodulation to find the received signal point. The purpose is to determine the divided area E to which it belongs, and determine that the received signal point corresponding to the transmitted signal point within this divided area E is a true received signal point.

However, in order to implement such a determination method, it is necessary to provide a ROM table that shows the correspondence between received signal points and divided areas E.
In the above case, this ROM table has a 10-bit input because the X and Y coordinate values representing the received signal point including its positive and negative information are 10 bits in total, and its contents are 1024 (bytes). Therefore, there is a problem that the size of the ROM table becomes extremely large.

[Object of the Invention] The present invention has been made in view of the above, and it is an object of the present invention to provide a received signal determination method that minimizes the size of a table to be searched based on coordinate values representing received signal points. The purpose is

[Structure of the Invention] In order to achieve the above object, the present invention determines carrier wave modulation information based on a transmission signal point expressed by a point on a transmission plane defined on the transmission side, and The receiving side demodulates the modulation information of the received wave modulated and transferred based on the received signal as a received signal point expressed by a point on the receiving plane corresponding to the above-mentioned transmitting plane defined on the receiving side, This received signal determination method determines the true received signal point corresponding to the transmitted signal point indicating modulation information on the transmitting side based on the received signal point demodulated corresponding to the actual received wave. Then, a predetermined area on the reception plane, which is a rectangular coordinate system, is designated as a fourth
As shown in the figure, the orthogonal coordinate axes (X axis, Y
The two orthogonal axes (X axis, Y
From the divided area that includes the received signal point expressed by the origin coordinates (S, S) of the axis) and is located at the corner of the divided area group, for each divided area of the divided area group,
One of the two orthogonal axes, for example Y
A predetermined initial value p and a predetermined tolerance q in the same direction as the axial direction.
While sequentially assigning numbers that form an arithmetic progression of , the number of area divisions N (N =
m), the initial value p, and the tolerance q, from the starting point coordinate value S in the orthogonal coordinate system to the coordinate value belonging to each same section for each section pitch l (for example,
S to S+l, S+l+1 to S+2, etc.), in order from the section containing the origin coordinate value S (p+
i・q・N) value (i=0, 1, 2, ..., n-
A table as shown in FIG. 5 in which 1) is assigned is provided, and the received signal points demodulated corresponding to the actual received waves are plotted on the axis (Y-axis) that is in the same direction as the numbering direction of the divided areas. Search the above table based on the coordinate values to find the (p+i・q・N) value, and then subtract the initial value p of the number given to the divided area from this search value (p+i・q・N) ( i, q, N) by the N value to find the (i, q) value, and the other axis (X axis) of the received signal point.
Search the above table based on the coordinate values in (p+j・q・N) values (j=0, 1, 2,...
..., n-1), and (i・
q) The relevant reception signal point exists within a divided region assigned the same number as the {p+q・(i+j・N)} value obtained by adding the value and the (p+j・q・N) value. The received signal point corresponding to the transmitted signal point within this divided area is determined as the true received signal point.

In addition, in FIG. 4, even if the numbering direction of the divided regions is the same as the X-axis direction, the configuration of the present invention does not change, and the above N value becomes N=n. Further, the situation does not change even if the Y-axis direction is divided into n divisions and the X-axis direction is divided into m divisions. Furthermore, when the axial directions of the X-axis and Y-axis are changed, the divided area to which the initial value is to be assigned is determined as one of the divided areas located in the squares of the divided area group as the position of the starting point coordinate changes.

[Operation] For example, in the examples shown in FIGS. 4 and 5, the X coordinate of the received signal point is (S+l+1) to (S+2l)
, and the Y coordinate is from (S+2l+1) to (S
+3l), based on the X coordinate value,
Search the table shown in Figure 5 to find the (p+m・q) value, search the table based on the Y coordinate to find the (p+2・m・q) value, and then use this search value (p+2・m・q) to find the (p+2・m・q) value. Subtract the initial value p from q) and divide the (2・m・q) value by m to find the (2q) value, and then combine the (p+m・q) value and (2・q) value found above. {p+(m+
2) It is determined that the received signal point exists within the divided area assigned the same number as the q} value.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described based on the drawings.

FIG. 6 is a block diagram showing the basic configuration of an example of a demodulator employing the received signal determination method according to the present invention. In this example, the receiving signal points corresponding to the 128 transmitting signal points shown in Figure 3 are arranged on the receiving plane defined on the receiving side, and the X and Y coordinate data of the receiving signal points are is expressed as 4-bit data (0, 1, . . . , E, F) (positive and negative information is separate).

In FIG. 6, for example, a modulated carrier wave is input from the CPU to the input port 51 via a line, and a received wave input to the input port 51 is input to the demodulation circuit 53 via the A/D conversion circuit 52. ing. Then, the demodulation circuit 53 demodulates the received wave to determine the X and Y points of the received signal point corresponding to the received wave.
The equalization circuit 54 outputs the coordinate data, and furthermore, the equalization circuit 54 corrects the effects of distortion and the like on the X and Y coordinate data from the demodulation circuit 53, and outputs new X and Y coordinate data. On the other hand, 55 is a ROM table for data retrieval based on each of the X and Y coordinate data from the equalization circuit 54 as will be described later, and 56 is a register for storing the search value Rx of the ROM table 55 based on the X coordinate data. A data register 57 includes a register for storing the search value Ry of the ROM table 55 based on the Y coordinate data, and a data register 57 performs a predetermined calculation based on the search values Rx and Ry stored in the data register 56, as will be described later. This is an arithmetic unit that performs the following. Then, the output from the calculation unit 57 is used as information on the true received signal point,
The coded data obtained by searching the code conversion table 58 based on this information is sent to the output port 5.
For example, the signal is output to the DTE 40 via the 9. Note that 50 is a processor that controls the entire system.

Here, as shown in FIG. 7, the receiving plane defined on the receiving side is (±7), (+
8) as the boundary, each quadrant has (A-1), (A-
2), (A-3), and (A-4). As shown in FIG. 8 which shows the first quadrant in particular, each quadrant has areas (A-1) of X,
At the same pitch l=2 in both directions of the Y coordinate axis, it is divided into 4×4 divided areas corresponding to the transmission signal points,
Starting from the divided area located at the corner of the divided area group that includes the received signal point expressed by the origin coordinates (0, 0) of the X, Y coordinate axes, initialization is performed for each divided area in the same direction as the Y-axis direction. Numbers forming an arithmetic progression with value p=0 and intersection q=1 are sequentially assigned (the assigned numbers are expressed in hexadecimal). (A-2) For the area, the X-axis direction corresponds to the transmission signal point, and the coordinate value is 9, between A and Y.
By dividing the axial direction with pitch l = 2,
It is divided into 8 divided area groups, and each divided area is (A
-1) Following the last assigned number (OF) of the area (A-1) from the side in contact with the area, numbers forming an arithmetic progression with a tolerance q=1 are sequentially assigned in the same direction as the Y-axis direction. Also, regarding area (A-3),
By dividing the X-axis direction at pitch l=2 and the Y-axis direction between coordinate values 9 and A corresponding to the transmission signal point, it is divided into 8 divided area groups, and each divided area is divided into (A -1) Above (A-) from the side touching the area
2) Following the area final assigned number (17), numbers are assigned sequentially in the same direction as the X-axis direction, forming an arithmetic progression with a tolerance of q=1. Furthermore, regarding the area (A-4), the divided area where the coordinate value X≧Y and the
<Y, the divided area where X≧Y is given the same number as the final assigned number (17) for the (A-2) area, and the divided area where X<Y is (A-3) Final assigned number in area (1F)
The same number has been assigned.

On the other hand, the specific contents of the ROM table 55 are the first table shown in FIG. 9 and the second table shown in FIG. =2
For the coordinate values belonging to the same section in each case, (p+i・q・
N) values, i.e. p=0, q=1, N=4 to (0+
4・i) Values (i=0, 1, 2, 3) are assigned, and the second table is “10” for coordinate values 8 and 9, and “14” for coordinate values A to F. It has been assigned.

Next, the operation will be explained.

The basic flow of operation is as shown in the flowchart shown in FIG.

First, from the X, Y coordinate output (equalized output) of the received signal point corresponding to the actual received wave, the quadrant information to which this received signal point belongs is determined based on the positive and negative bits of the X, Y coordinate output, and , calculate the absolute value of the Y coordinate value. The purpose of this absolute value calculation is to limit the target reception plane to the first quadrant shown in FIG.

Next, based on the absolute values of the X and Y coordinate values, the received signal points are (A-1), (A-2), (A-3), (A
-4) Determine which region it belongs to. Specifically, since the above absolute value is expressed in 4 bits, the most significant bit of the 4-bit data is
The separation at coordinate values 7 and 8 is determined by determining whether the MSB is “0” or “1”. In this way, after determining the areas (A-1) to (A-4), individual processing as described below is performed for each area,
The divided area (see FIG. 8) to which the received signal expressed by the absolute value coordinate belongs is determined. and,
Based on the initially obtained quadrant information, it is determined to which quadrant the divided area identified above belongs, and the received signal corresponding to the transmitted signal point in the divided area whose quadrant is finally determined is determined as the true It is determined as the received signal point.

Next, individual processing in the above areas (A-1) to (A-4) will be explained.

(1) Area A-1 Search the first table (Fig. 9) based on the X coordinate value (absolute value, the same applies hereinafter) of the received signal point, and send the search value Rx to the data register 56.
Store in.

The first table is searched based on the Y coordinate value (absolute value, the same applies hereinafter) of the received signal point, and the search value Ry is stored in the data register 56.

Search value Ry stored in data register 56
The calculation of Ry/4 is performed on that to create a new Ry (Ry←Ry/4).

The divided area assigned the same number as the value obtained by adding the search value Rx and the new Ry is determined.

For example, if the received signal point is (4, 6),
Since Rx=08 and Ry=OC, 08+OC/4=OB, and the divided area to which the received signal point (4, 6) belongs is determined to be the divided area assigned the number OB.

(2) A-2 area Search the second table (Fig. 10) based on the X coordinate value of the received signal point, and find the search value Rx
is stored in the data register 56.

The first table is searched based on the Y coordinate value of the received signal point, and the search value Ry is stored in the data register 56.

Search value Ry stored in data register 56
The calculation of Ry/4 is performed on the R to create a new R (Ry←Ry/4).

The divided area assigned the same number as the value obtained by adding the search value Rx and the new Ry is determined.

For example, if the received signal point is (8, 3),
Since Rx=10 and R=04, 10+04/4=11, and the divided area to which the received signal point (8, 3) belongs is determined to be the divided area assigned the number 11.

(3) Area A-3 The first table is searched based on the X coordinate value of the received signal point, and the search value Rx is stored in the data register 56.

The second table is searched based on the Y coordinate value of the received signal point, and the search value Ry is stored in the data register 56.

Search value Ry stored in data register 56
Add 08 to to create a new Ry (Ry←Ry/
08).

Search value Rx stored in data register 56
The calculation of Rx/4 is performed on the current Rx to obtain a new Rx (Rx←Rx/4).

The divided area assigned the same number as the value obtained by adding the newly obtained Rx and Ry as described above is determined.

For example, if the received signal point is (4, 9), Rx
=08, Ry=10, so 10+8+08/4=1A, and the divided area to which the received signal point (4, 9) belongs is determined to be the divided area assigned the number 1A.

(4) Area A-4 Compare the X and Y coordinate values of the received signal point.

When X≧Y, the divided area numbered 17 is determined.

When X<Y, the divided area numbered 1F is determined.

As mentioned above, according to this embodiment, small-scale
By using the 4-bit input ROM table 55 with 16-byte content, it becomes possible to discriminate the receiving signal points corresponding to the 128 transmitting signal points, and this is realized in the process of this discrimination. As for calculations, only addition and division by "4" can be performed by a 2-bit shift operation, and the processing is easy.

[Effects of the Invention] As explained above, according to the present invention, a predetermined area on the receiving plane is arranged at the same pitch l in both directions of the orthogonal coordinate axes, m×n (n≧m ), and when determining the divided area to which the received signal point corresponding to the received wave belongs, what conventionally required an m x n byte table can now be done with a simple n byte table. This makes it possible to make the determination simply by using a smaller table.

The present invention is more effective as the number of transmission signal points in the same area increases, that is, in a communication system where data transfer becomes faster.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the basic configuration of the communication system, Figure 2 is an explanatory diagram showing an example of reception signal points corresponding to transmission signal points on the reception plane defined on the reception side, and Figure 3 is an illustration of 128 points. FIG. 4 is an explanatory diagram showing an example of the arrangement of received signal points, FIG. 4 is an explanatory diagram showing more generally the state of numbering divided areas in the received signal determination method according to the present invention, and FIG. 5 is an explanatory diagram according to the present invention. An explanatory diagram more generally showing the state of the table in the received signal determination method, FIG. 6 is a block diagram showing the basic configuration of an example of a demodulator that employs the received signal determination method according to the present invention, and FIG. An explanatory diagram showing the state of region division of the plane, FIG. 8 is an example in which the first quadrant of the reception plane is divided into a group of divided regions corresponding to the transmission signal points,
and an explanatory diagram showing an example of numbering divided areas, No. 9
10 are explanatory diagrams showing tables to be provided corresponding to the divided area groups shown in FIG.
This figure is a flowchart showing the flow of received signal determination operation in the apparatus shown in FIG. 50... Processor, 51... Input port, 5
2...A/D conversion circuit, 53...Demodulation circuit, 54
... Equalization circuit, 55 ... ROM table, 56 ...
...Data register, 57...Arithmetic unit, 58...Code conversion table, 59...Output port.

Claims (1)

[Claims] 1. Modulation information of a carrier wave is determined based on a transmission signal point expressed by a point on a transmission plane defined on the transmission side, and reception modulated and transferred based on this modulation information. While demodulating the modulation information of the received wave at the receiving side as a received signal point represented by a point on the receiving plane corresponding to the above-mentioned transmitting plane defined by the receiving side, A received signal determination method that determines the true received signal point corresponding to the transmitted signal point indicating modulation information on the transmitting side based on the demodulated received signal point, and the received signal point is a rectangular coordinate system. A predetermined area on a plane is m×n (n≧m) corresponding to the transmission signal point at the same pitch in both directions of the orthogonal coordinate axes.
divided into a group of divided areas, including the received signal point expressed by the origin coordinates of two orthogonal axes in the predetermined area, and from the divided area located at the corner of the group of divided areas to each divided area of the group of divided areas. On the other hand, numbers forming an arithmetic progression of a predetermined initial value p and a predetermined tolerance q are sequentially assigned in the same direction as either one of the orthogonal two axes, while the number of area divisions N (N = m or n), the above initial value p, and the tolerance q, from the starting point coordinate value in the orthogonal coordinate system to the coordinate value belonging to each same section for each section pitch, from the section containing the starting point coordinate value. (p+i・q・N) values (i=0, 1, 2, ...,
n-1) is provided, and the table is searched based on the coordinate value of the received signal point demodulated corresponding to the actual received wave on the axis that is in the same direction as the numbering direction of the divided area. (p
+i・q・N) value, and further calculate this search value (p+
The value (i, q, N) obtained by subtracting the initial value p of the number assigned to the divided area from the number (i, q, N) is divided by the N value to obtain the (i, q) value, and the received signal point Search the above table based on the coordinate value on the other axis of (p+j・q・N) value (j=0,
1, 2, ..., n-1), and add the (i・q) value obtained above and the (p+j・q・N) value to obtain {p+q・(i+j・N) } determine that the relevant reception signal point exists within the divided area assigned the same number as the value, and determine the reception signal point corresponding to the transmission signal point within this divided area as the true reception signal point. A received signal determination method characterized by: