JPH07112208B2 - Multi-level amplitude modulation / demodulation communication system - Google Patents

Description

The present invention relates to a multi-level amplitude modulation / demodulation communication system, which is capable of increasing the multi-level number without deteriorating the transmission quality and significantly increasing the transmission power, thereby providing a communication system with high practicality. A transmitter having a modulator for use in a communication system for performing multi-level amplitude modulation / demodulation using honeycomb-shaped signal point constellation for the purpose of configuring, wherein the modulator is a signal point constellation for in-phase data and quadrature data. And a quadrature amplitude modulation unit for quadrature amplitude modulating the in-phase data and the quadrature data converted into the honeycomb arrangement, and the receiving device. Also in the above, the demodulator is configured to correspond to the modulator.

[Industrial application field]

The present invention has a transmitter having a honeycomb-shaped modulator for converting a multi-valued quadrature amplitude modulation signal used in a digital communication system, particularly digital radio, and a demodulation device for performing a multi-valued quadrature amplitude demodulation on a honeycomb reception signal from the transmitter. The present invention relates to a receiver and a multilevel amplitude modulation communication system having the transmitter and the receiver.

In digital communication systems, especially digital wireless communication systems, multi-value modulation is effective in order to improve frequency utilization efficiency. For this reason, I and Q data that are orthogonal to each other can be independently D / A converted for modulation, and the circuit configuration is simple, so quadrature amplitude modulation (QA
M) method is adopted. The demodulation side is also A independently
A demodulator can be realized relatively easily by performing / D conversion.
Further, in the QAM system, the interval between adjacent signal points can be set relatively large and the reception error rate can be reduced.

From the viewpoint of improving frequency utilization, the modulation level is increasing from 4 levels to 16 levels and further to 256 levels.
However, the transmission power is remarkably increased with the multi-value.
Therefore, it is desired to develop a modulation device that can perform efficient modulation to secure a required reception level without reducing the error rate, in other words, without reducing the interval between orthogonal signals. There is. The same situation applies to the demodulation device provided on the reception side corresponding to the modulation device on the transmission side. Therefore, the development of an economical and practical multi-level amplitude modulation / demodulation wireless communication system using the modulation and demodulation devices, which uses the modulation and demodulation devices and has excellent frequency utilization efficiency and power efficiency Is desired.

[Prior art and problems to be solved by the invention]

FIG. 15 shows an example of the configuration of a conventional multi-level quadrature amplitude modulation type modulator provided in the transmitter. 11 and
12 is a D / A converter, 2 is a quadrature amplitude modulation circuit, and includes roll-off filters 21 and 22, multipliers 23 and 24, adder 2
5, the carrier oscillator 26, and the π / 2 phase shifter 27 are included, and the modulator output is frequency-converted into a predetermined radio frequency band by the frequency converter 31 and the local oscillator 32 that function as a mixer. 3 is a transmission power amplifier. In this modulator, in-phase input data D (i) and quadrature input data D (q) are independently input to D / A converters 11 and 12, respectively, and D / A-converted independently, and their outputs are rolled. It is applied to the multipliers 23 and 24 through the off-filters 21 and 22, modulated by the carrier wave fc and its π / 2 phase-shifted carrier wave fc ′ in the multipliers 23 and 24, respectively added by the adder 25, and added by the adder 25. The QAM modulated wave from 25 is output to the transmission power amplifier 3 via the frequency converter 31. The signal point arrangement of the QAM-modulated signal in this case is a right-angle grid arrangement as shown in FIG. The example in FIG. 16 is for 64-value QAM. In the figure, in-phase input data is plotted on the abscissa and orthogonal input data is plotted on the ordinate.

FIG. 17 is a diagram showing the increase in the S / N ratio with the multi-valued for the QAM system and the PSK (Phase Shift Keying) system. The ordinate shows the S / N increase amount compared to the two-phase PSK. Multi-valued number n on the abscissa
Has been taken. As is clear from this figure, the QAM system has a smaller S / N ratio to obtain the same error rate than the PSK system,
Although this is an efficient modulation method, it requires a large S / N ratio as the number of multivalued n increases. Therefore, in order to secure the required S / N ratio, it is necessary to keep the signal point interval constant, and a larger transmission power is required as the number of multivalues increases.

The signal points of the modulation signal of the conventional QAM system are arranged in a rectangular grid as shown in FIG. In the figure, among the signal points, the signal points that give the peak power are a (1) to a at the four corners.
(4). The ratio of the average power to the peak power of the signal increases as the number of multi-values n increases, and as the number of multi-values n increases as described above, a larger S / N ratio is required, so the same transmission power When an amplifier is used, the multi-valued number n increases and the transmission power amplifier requires a larger backoff. That is, the power amplifier must be used in a portion having linearity, but a power amplifier having a wide margin as well as wide linearity is required as the transmission power increases. FIG. 18 is a diagram showing the C / N deterioration characteristics of the 4-phase PSK system (the same as the 4-level QAM system) and the 16-level QAM system for explaining this. The output backoff is shown on the abscissa. The equivalent C / N deterioration amount is plotted on the ordinate. As is clear from the figure, the output backoff that gives the same C / N deterioration amount is larger in the 16-value QAM method than in the 4-phase PSK (4 value QAM) method.

As described above, in the conventional quadrature amplitude modulation type modulator, when the multi-valued number n is increased in order to improve the frequency utilization efficiency, the transmission power increases accordingly. For example, in the case of 256-level modulation, 80 times the transmission power of 4-level modulation is required. Moreover, as the multi-valued value n increases, the back-off of the transmission power amplifier also increases, so that a large power of the transmission power amplifier,
There is a problem in that a backoff that is sufficiently large is required.

Furthermore, increasing the transmission power causes a new problem of interfering with other systems and causing radio interference.

The problem described above is the Q that receives and demodulates a QAM-modulated signal.
The same occurs in the AM demodulator. Therefore, these QA
Even in a digital wireless communication system using the M modulator and the QAM demodulator, the above-mentioned problem is caused by increasing the multi-valued number n.

A honeycomb type signal point arrangement has been proposed as a signal point arrangement for reducing the ratio of the average power to the peak power of a signal. In the honeycomb-shaped signal point arrangement, the intervals between adjacent signal points are all the same, and the outer ring of the signal point that draws a boundary line by a perpendicular bisector of the adjacent signal points has a hexagonal shape. If multi-valued quadrature amplitude modulation / demodulation is performed using such a honeycomb-shaped signal point arrangement, signal points with the same intervals can be arranged within a circle with a smaller radius, so the transmission power amplification on the transmission side should be reduced. You can However, heretofore, a digital wireless communication system has not been known which discloses a specific configuration for performing quadrature amplitude modulation / demodulation with such a honeycomb-shaped signal point arrangement. Therefore, with a relatively simple circuit configuration, a large number of multi-values can be taken in order to improve the frequency utilization efficiency, and a multi-level amplitude modulation / demodulation communication system that is excellent in transmission power efficiency without lowering transmission quality and the communication concerned. There is a need for modulators and demodulators for use in the system.

[Means and Actions for Solving Problems]

FIG. 1 shows a principle block diagram of a multilevel amplitude modulation communication system of the present invention. The communication system includes a transmitter 100 including a modulator 100a, which is coupled via a transmission path 300.
And a receiver 200 having a demodulator 200a. Hereinafter, the modulation device 100a and the demodulation device 20 according to the gist of the present invention
The description will focus on 0a.

The quadrature amplitude modulation device 100a according to the present invention uses the in-phase data D (i).
And a signal point arrangement conversion unit 101 for converting the signal arrangement of the orthogonal data D (q) from the rectangular lattice arrangement to the honeycomb arrangement,
Further, it is provided with a quadrature amplitude modulation section 102 that quadrature amplitude modulates the in-phase data and the quadrature data converted into the honeycomb arrangement.

The signal point arrangement conversion unit 101 converts the signal point arrangement of the in-phase data and the quadrature data from the rectangular lattice arrangement to the honeycomb arrangement. The honeycomb arrangement is as shown in FIG.
The signal point arrangement is such that the intervals between adjacent signal points of the signals are all the same, and the ratio of the average power to the peak power of the signal is smaller than that in the rectangular grid type arrangement. The in-phase data and the quadrature data thus arranged in the honeycomb form are converted into the quadrature amplitude modulation signal 102.
Then, the signal is quadrature amplitude modulated and sent to the transmission power amplifier.

This makes it possible to reduce the backoff of the transmission power amplifier. Further, since the in-phase and quadrature data are input, quadrature amplitude modulated and transmitted, and only the honeycomb deformation is performed inside, the circuit configuration is simple and the implementation is easy.

Note that the signal point arrangement conversion unit 101 and the quadrature amplitude modulation unit 102 may be integrated to perform signal point arrangement and honeycomb arrangement conversion at the same time.

The demodulator 200a of the communication device for performing multi-valued quadrature amplitude modulation / demodulation using the honeycomb-shaped signal point arrangement of the present invention synchronously detects the received multi-valued quadrature amplitude-modulated wave QAM, and the in-phase signal _xb and the quadrature signal y. _The synchronous detection unit 201 that obtains _b , the in-phase signal x _b, and the quadrature signal y _b are calculated by converting the quadrature coordinate axes into three coordinate axes connecting adjacent signal points in the honeycomb signal point arrangement. A coordinate transformation unit 202 that obtains three corresponding coordinate transformation output signals x, u, v, and a signal that determines the signal point of the received signal based on the three coordinate transformation output signals x, u, v to obtain output data. The determination unit 203 is provided.

Obtaining a phase signal x _b and the quadrature signal y _b by detecting the received multi-level quadrature amplitude modulation and demodulation wave QAM by the synchronous detector 201. For these, the coordinate conversion unit 202 performs an operation to convert the orthogonal coordinate axes into three coordinate axes connecting adjacent signal points in the honeycomb-shaped signal point arrangement, and performs three coordinate conversion output signals x, u, v corresponding to the respective coordinate axes. To get The signal determination unit 203 determines the signal point of the output signal x, u, v, and outputs the output data corresponding to the signal point.

A demodulator of another form of the present invention inserts an equalizer 204 for automatically equalizing in-phase signals and quadrature signals between the synchronous detector 201 and the coordinate converter 202 of the above-mentioned demodulator. It is arranged so that the control signal of the equalization unit 204 is created based on the output signal after the determination by the signal determination unit. This improves the quality of the received signal.

〔Example〕

 Embodiments of the present invention will be described below with reference to the drawings.

FIG. 3 is a block diagram showing a modulator using a multi-level quadrature amplitude modulation / demodulation method provided in a transmitter as an embodiment of the present invention. This modulator is 64-valued. In the figure, 51 and 52 are mapping ROMs, 11 and 12 are D / A
A converter, 4 is a coordinate conversion circuit, 2 is a quadrature amplitude modulation circuit, and a roll-off filter 21 as a low-pass filter and
22, multipliers 23 and 24, adder 25, carrier oscillator 26, π
1/2 comprising a phase shifter 27, 31 is a frequency converter,
32 is a local oscillator, and 3 is a transmission power amplifier.
ROM51 and 52, D / A converters 11 and 12, coordinate conversion circuit 4
Corresponds to the signal point arrangement conversion unit 101 in FIG.

Mapping ROMs 51 and 52 are used for in-phase input data D
(I) and the quadrature input data D (q) are used to move a part of the arrangement of the signal points of the rectangular lattice type. FIG. 4 is a diagram for explaining the movement of the signal points, and shows a signal point arrangement of a 64-ary QAM rectangular grid. In the figure, the in-phase input data D (i) is taken on the abscissa, and the quadrature input data D (q) is taken on the ordinate, and the single circle (○) mark indicates the rectangular grid signal point arrangement by 64QAM. Double circles (⊚) indicate the signal points after moving the signal points of regions I and II to region III. Mapping ROMs 51 and 52 shown in FIG.
The signal points of the in-phase input data D (i) and the quadrature input data D (q) are rearranged so that the signal points of the broken lines I and II in the figure are moved to the position of the broken line III. Input data D (i) and orthogonal input data D
In-phase and quadrature data x _a using (q) as an address input
And y _a to D / A converters 11 and 12, respectively. D
/ A converters 11 and 12 respectively input data x _a, converts the y _a coordinate data I _a analog, the Q _a.

The coordinate conversion circuit 4 performs coordinate conversion of the coordinates I _a and Q _a of the signal point arrangement of the input data according to the relationship of the following equation.

The coordinate conversion circuit 4 has a coefficient Coefficient multiplier 41 for multiplying by, coefficient multiplier 4 for multiplying coefficient β _a = 1/2
2 and a subtractor 43.

The operation of the modulator of this embodiment will be described below.

In-phase input data D (i) and quadrature input data D (q)
The signal point arrangement is moved by the mapping ROMs 51 and 52, and the broken line I and II portions of the rectangular grid type arrangement are moved to the broken line III portion as shown in FIG. As a result, the signal point constellation of 64QAM is a regular quadrangle before the movement, while it is almost an ellipse after the movement. The data x _a and y _a after the signal point arrangement conversion are input to the D / A converters 11 and 12 and converted into the analog signals I _a and Q _a , and then to the coordinate conversion circuit 4, and the first (1) Further, based on the equation (2), it is further converted into the signal point constellation surrounded by the broken line IV in FIG. At this time, the signal point surrounded by the broken line III in FIG. 4 after movement is conceptually arranged at the signal point indicated by a star (★) in FIG. In this way, the adjacent signal point arrangement after coordinate conversion is a regular triangle, the adjacent signal point intervals are the same, and the boundary between the signal point arrangements is a hexagonal honeycomb shape. In FIG. 5, the signal points include one central signal point C ₀ , six first outer ring signal points C _{11 to} C ₁₆ , and second outer ring signal points C _{201 to} C _16.
There are 12 _212, 18 signal points on the 3rd outer ring, 23 signal points on the 4th outer ring (1 point is missing in region II '4), 4 signal points on the 5th outer ring, total 64 points. Yes, it supports 64 QAM points.
As a result, the ratio of the average power of the signal to the peak power defined by the outermost signal point is small compared to the conventional rectangular grid type, which can reduce the backoff of the transmission power amplifier.

On the other hand, since the interval between adjacent signal points is the same as the interval of one side of the conventional rectangular grid, the error rate does not decrease.

Note that FIG. 5 shows an example of a honeycomb-shaped signal point arrangement,
The honeycomb-shaped signal point arrangement is not limited to that shown in FIG.

FIG. 6 is a diagram showing the characteristics of the amplifier back-off vs. C / N ratio deterioration for the cases of the rectangular grid signal point arrangement and the honeycomb signal point arrangement. As is clear from this figure,
For the same C / N ratio, the honeycomb signal point arrangement can reduce the amplifier backoff more than the rectangular lattice arrangement.

When the signal points are not moved by the mapping ROMs 51 and 52, the signal points indicated by broken lines I and II in FIG. 4 are arranged at the positions indicated by broken lines I'and II 'in FIG. In this case, the outer ring of the signal point arrangement is a parallelogram and does not become a honeycomb hexagon surrounded by the region IV in FIG. 5, and the ratio of the average power of signals to the peak power is not small. Therefore, it is necessary to move the signal points by the mapping ROMs 51 and 52.

The output data from the coordinate conversion circuit 4 is sent to the QAM modulation circuit 2 having the conventional structure, subjected to quadrature amplitude modulation, mixed by the frequency converter 31, and sent from the transmitter to the receiving side via the amplifier 3.

What is clear from the above is that when a signal having a signal point arrangement having a honeycomb shape is transmitted, the same in-phase input data D (i) and quadrature input data D (q) which are independent from each other as in the conventional case are transmitted.
, And the signals x _a and y _a are generated by moving the signal points in the ROMs 51 and 52, and the analog signals I _a and By converting into Q _a , and further coordinate conversion in the coordinate conversion circuit 4 based on the equations (1) and (2), the modulation is performed in the QAM modulation circuit 2 as in the conventional case, and then the transmission power amplifier is transmitted via the frequency converter 31. 3 is applied, and with a relatively simple circuit configuration,
That is, the honeycomb modulator is configured. Moreover, the above-described effect can be obtained by transmitting the signal of the honeycomb-shaped signal point arrangement.

Regarding the demodulation device in the reception device that demodulates the data signal that is transmitted from the transmission device having the modulation device converted into the honeycomb configuration as described above and is received by the transmission device through the transmission path 300 and converted into the honeycomb configuration is as follows: Explained.

FIG. 7 is a block diagram showing a demodulation device by such a multilevel quadrature amplitude modulation / demodulation system, and this demodulation device is assumed to be of 64 values. In the figure, 7 is a synchronous detection circuit, 8 is a coordinate conversion circuit, and 9
Is an identification circuit, and 10 is a signal determination circuit. Synchronous detection circuit 7
Is a well-known device that includes multipliers 71 and 72, low-order filters 73 and 74, a regenerated carrier wave generator 75, and a π / 2 phase shifter 76, and synchronously detects a received multilevel quadrature amplitude modulation wave. And outputs a baseband in-phase signal x _b and a quadrature signal y _b .

The coordinate conversion circuit 8 includes coefficient units 81 and 82, an adder 83, and a subtractor.
Composed of 84. Coefficient multiplier 81 coefficients in-phase signal x _b alpha _b
= Multiplier of 1/2, coefficient unit 82 calculates quadrature signal y _b It is a circuit to multiply by. The coordinate conversion circuit 8 has the orthogonal coordinate axes x _b and y for the in-phase signal x and the in-phase signal x _b.
As shown in FIG. 8, _b is converted into three coordinate axes X, U, V connecting adjacent signal points in the honeycomb signal point arrangement, and the in-phase signal x _b and the quadrature signal are converted for each coordinate axis. The coordinate conversion signals x, u, v obtained by converting y _b are transmitted. This coordinate conversion is performed according to the following formula.

The discriminating circuit 9 comprises three A / D converters 91 to 93, discriminates the signal level on the coordinate axes X, U, V with respect to the coordinate conversion signals x, u, v, and has a 4-bit digital format in the case of 64 values. Output as level signals x ', u', v '. The level signals x ′, u ′, v ′ after identification by the identification circuit 9 are sent to the signal determination circuit 10. The signal decision circuit 10 is composed of a ROM, and the level signals x ', u', v'are used as input addresses for the level signals x ',
Output data corresponding to the signal points in the arrangement of FIG. 8 designated by u ', v'is output.

The operation of this demodulator will be described below.

Multilevel quadrature amplitude modulated wave received in the synchronous detection circuit 7 is synchronous detection in in-phase signal x _b and the quadrature signal y _b are obtained, it is converted to the coordinate axes in the coordinate conversion circuit 8 coordinate conversion signal
x, u, v. Then, the discrimination circuit 9 discriminates the signal levels of these coordinate conversion signals x, u, v. The identified level signals x ', u', v'are sent to the signal determination circuit 10 to determine the signal points corresponding to those signals. FIG. 8 shows the state of this signal determination. That level signal x ', u', if v 'values of _{x' 1, u '1,} v' 1 to signal points corresponding to these levels become point A, the output data corresponding to the signal point A Is obtained. In this way, when the signal level is judged for the coordinate axes X, U, V and the signal is judged, the distance between the signal point to be judged and the adjacent signal point becomes the maximum in each axis, and therefore the judgment threshold is maximized. Therefore, the margin for noise and the like is increased.

As described above, the transmission device having the modulation device shown in FIG. 3 and the reception device having the demodulation device shown in FIG. It is possible to realize an economical and practical digital wireless communication system which is excellent in frequency utilization efficiency and power efficiency.

In implementing the present invention, various modifications of the modulator are possible. FIG. 9 is a block diagram showing such a modification. In the figure, blocks having the same reference numerals as in FIG. 3 are blocks having the same function. The difference is that the device of FIG. 9 does not have the coordinate conversion circuit 4, and the conversion from the rectangular grid with the signal point arrangement to the honeycomb shape is done by the mapping ROM6.
Do at 1 and 62. That is, in-phase input data D (i)
And the orthogonal input data D (q) are used as input addresses, and the coordinate values such that the output data of the mapping ROMs 61 and 62 have the honeycomb signal point arrangement are given as the storage data of the mapping ROMs 61 and 62.

As a demodulator for this, the one shown in FIG. 7 may be used.

On the other hand, in implementing the present invention, the demodulator can be modified in various ways. FIG. 10 shows another embodiment of the present invention. The difference from the demodulator shown in FIG. 7 is that the positions of the coordinate conversion circuit and the discrimination circuit are interchanged, and in this embodiment, the output signal from the synchronous detection circuit 7 is sent to the discrimination circuit 9 '. The signal after the signal level is discriminated by the discriminating circuit 9'is subjected to coordinate conversion by the coordinate converting circuit 8 '. In this case, since the coordinate conversion circuit 8'is provided in the subsequent stage of the identification circuit 9 ', it has a digital configuration.
The demodulator of the present embodiment having the circuit as described above can eliminate one A / D converter in the identification circuit as compared with the embodiment of FIG. The demodulation performance is the same as that of the above-mentioned embodiment.

FIG. 11 shows still another embodiment of the demodulation device of the present invention.
In this embodiment, an automatic equalizer 15 is added to the apparatus of FIG. 7, and the automatic equalizer 15 having an analog structure is inserted and arranged between the synchronous detection circuit 7 and the coordinate conversion circuit 8. ing. The control signals of the automatic equalizer 15 are X-axis and Y-axis.
Polarity and error signals for the axes are used. That is, for the X-axis, the 4-bit level signal x ′ of the discrimination circuit 9 ″ having the four A / D converters 91 to 93, 95 is subtracted from the 4-bit ideal obtained by the signal determination circuit 10 ′. Bowl 16
The error signal .epsilon.x obtained by subtracting and the polarity signal (that is, the most significant bit signal) of the output signal x'from the discrimination circuit 9 "are used as the control signals of the X-axis side equalizer. A new A / D converter 95 for discriminating the level of the quadrature signal y is provided, and the level signal y ′ from the discriminating circuit 9 ″ and the ideal value obtained by the signal judging circuit 10 ′ are subtracted by the subtractor 18. The obtained error signal εy and the polarity signal (that is, the most significant bit signal) of the output signal y ′ from the A / D converter 95 are Y.
This is the control signal for the shaft-side equalizer.

By adding the automatic equalizer as in the present embodiment, it becomes possible to remove the inter-symbol interference by following the temporal variation of the transmission path characteristics such as frequency selective fading, and improve the received signal quality.

FIG. 12 shows still another embodiment of the present invention. In this embodiment, an automatic equalizer 15 'is added to the demodulator shown in FIG. 10, and an automatic equalizer 15' having a digital structure is inserted and arranged between the discrimination circuit 9'and the coordinate conversion circuit 8 '. is doing. In this case, the number of bits of the digital output signal of the discrimination circuit 9'is
Although the number of bits is small in FIG. 11, it is increased to 10 bits, for example. Therefore, in order to reduce the number of bits for signal determination by the signal determination circuit 10, the ROMs 141 to 14
A bit number low frequency circuit 14 composed of 3 is inserted and arranged between the coordinate conversion circuit 8 ′ and the signal determination circuit 10.

As for the control signal of the automatic equalizer 15 ', for the X-axis side equalizer, the higher-order 4-bit signal of the 10-bit output of the automatic equalizer 15' and the 4-bit signal obtained by the signal determination circuit 10 are used. Error signal εx obtained by subtracting the ideal value of
And the polarity signal of the output signal from the automatic equalizer 15 '(that is, the signal of the most significant bit) is used as the control signal. As for the Y-axis side equalizer, the subtractor 18 'subtracts the 4-bit high-order signal of the 10-bit output of the automatic equalizer 15' and the 4-bit ideal value obtained by the signal determination circuit 10. The error signal εy obtained as a result and the polarity signal of the output signal from the automatic equalizer 15 '(that is, the signal of the most significant bit) are used as control signals.

In order to obtain the error signal, its input signal may be used instead of the output signal of the automatic equalizer 15 '.

FIG. 13 shows a block diagram of a modulator as still another embodiment of the present invention. The modulator shown in FIG. 13 is obtained by replacing the functions of the coordinate conversion circuit 4 and the quadrature amplitude modulation circuit 2 of the modulator shown in FIG. 3 with a coordinate conversion amplitude modulation circuit 2a. Π / 2 in the quadrature amplitude modulation circuit 2
The phase shifter 27 is replaced with a 2π / 3 mover 28, and the coordinate conversion circuit 4 of FIG. 3 is deleted. Therefore, the circuit configuration of the modulator of FIG. 13 is significantly simplified as compared with the circuit configuration of the modulator of FIG.

The operation of the modulator shown in FIG. 13 will be described below.

The signal points are arranged by the ROMs 51 and 52 as shown in FIG. 4 and converted into analog values through the D / A converters 11 and 12, which is the same as the operation of the modulator shown in FIG. Next, in the modulator shown in FIG. 3, the coordinate conversion circuit 4 converts the orthogonal I and Q data.
After once converting to the honeycomb-shaped signal point arrangement shown in the area IV in FIG. 5 based on the equations (1) and (2), the quadrature amplitude modulation circuit 2 again amplitude-modulates the I and Q components, respectively. ing. Therefore, the coordinate conversion circuit 4 and the quadrature amplitude modulation circuit 2
In the combination function of, the coordinate conversion is performed by 120 ° (2π / 3 radians) in the counterclockwise direction with respect to the I axis as shown in FIG. 14. Therefore, in the modulator of FIG.
The coordinate conversion is directly performed by the 2π / 3 phase shifter 28 to obtain the signal point arrangement shown in FIG. To obtain the same signal point arrangement, instead of the 2π / 3 mobile unit 28, 60 ° (π / 3 radian)
A π / 3 phase shifter that shifts the phase may be used.

As the demodulation device using the modulation device shown in FIG. 13, various devices described above can be used. The reason is that the signal wirelessly transmitted via the transmission power amplifier 3 is the same as that shown in FIG.

The above embodiment has been described with respect to the case of 64QAM.
The same applies to QAM and others.

In constructing the digital wireless communication system of the present invention, a transmitter including any of the various modulators described above and a receiver including any of the various demodulators described above are used in an arbitrary combination. You can

〔The invention's effect〕

As described above, in the transmitter having the modulator of the present invention, the signal point arrangement of the transmission data can be converted from the rectangular lattice type to the honeycomb type in the modulator, whereby the backoff of the transmission power amplifier can be achieved. Can be made smaller. As a result, it can be economically adapted to the increase in the number of multi-values in the multi-valued quadrature amplitude modulation system.

Further, the receiving device having the demodulation device of the present invention, in the demodulation device, it is possible to demodulate a multi-valued quadrature amplitude modulation wave having a honeycomb-shaped signal point arrangement, and therefore the multi-valued quadrature amplitude modulation wave to be transmitted on the transmission side A honeycomb arrangement can be used as the signal point arrangement of, and thereby the backoff of the transmission power amplifier can be reduced. As a result, it can be economically adapted to the increase in the number of multi-values in the multi-valued quadrature amplitude modulation system.

Therefore, the multilevel amplitude modulation communication system of the present invention using these transmitters and receivers can increase the number of multilevels to improve the frequency utilization efficiency, and transmit without deteriorating the transmission quality. Excellent power efficiency.

[Brief description of drawings]

FIG. 1 is a principle block diagram of a transmitter having a modulator of the present invention, a receiver having a demodulator, and a multilevel amplitude modulation communication system using them, and FIG. 2 is a honeycomb type signal point used in the present invention. FIG. 3 is a diagram showing the arrangement, FIG. 3 is a block diagram of a quadrature amplitude modulation device as one embodiment of the present invention, FIGS. 4 and 5 are diagrams for explaining the operation of the device of FIG. 3 embodiment, and FIG. FIG. 3 is a diagram showing the amplifier backup vs. C / N deterioration characteristic in the case of a rectangular grid signal point arrangement and a honeycomb type signal point arrangement in FIG. 3, and FIG. 7 is a configuration diagram of a demodulation device as one embodiment of the present invention, FIG. 8 is an explanatory view of a signal determination method of the demodulator, FIG. 9 is a block diagram of a modulator of another embodiment of the present invention, and FIGS. 10 to 12 are other embodiments of the present invention. Fig. 13 is a block diagram of a demodulator of Fig. 13, and Fig. 13 is a modulator of still another embodiment of the present invention. Configuration diagram, FIG. 14 is an operation explanatory diagram of the modulation device in FIG. 13, FIG. 15 is a configuration diagram of a conventional quadrature amplitude modulation device, FIG. 16 is a rectangular grid signal point arrangement diagram, and FIG. 17 is multi-valued. Fig. 18 is a diagram for explaining the increase in the signal-to-noise ratio accompanying Fig. 18, Fig. 18 is a diagram showing the C / N ratio deterioration characteristics of the QAM system and the PSK system,
Is. (Description of Codes) 2 ... Quadrature amplitude modulation circuit, 3 ... Transmission power amplifier, 4 ... Coordinate conversion circuit, 7 ... Synchronous detection circuit, 8 ... Coordinate conversion circuit, 9 ...
Identification circuit, 10 ... Signal determination circuit, 51, 52 ... RO for mapping
M.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Morihiko Minowa 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor, Yoshimasa, 1015, Kamedotachu, Nakahara-ku, Kawasaki, Kanagawa Prefecture, Fujitsu Limited ( 72) Inventor Hiroshi Nakamura 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (56) References JP-A-57-176867 (JP, A) JP-A-56-52954 (JP, A) JP-A 61-112431 (JP, A)

Claims (2)

[Claims] 1. A transmitter having a modulator used in a communication system for performing a multi-level amplitude modulation / demodulation using a honeycomb signal point arrangement, wherein the modulator (100a) has an arrangement of signal points of in-phase data and quadrature data. A signal point arrangement conversion unit (101) for converting a rectangular grid arrangement to a honeycomb arrangement, and a quadrature amplitude modulation unit (102) for quadrature amplitude modulation of the in-phase data and the quadrature data converted to the honeycomb arrangement. The signal point arrangement conversion unit (101) moves the position of a predetermined signal point among the signal points arranged by the in-phase data and the quadrature data of the digital signal to another signal point position using the ROM table, and For a signal point, a position conversion unit (51, 52) that outputs in-phase data and quadrature data in the same position, in-phase data and direct data from the position conversion unit (51, 52). Digital / analog conversion means (11, 12) for converting data from digital signals to analog signals, and coordinates of the in-phase data and quadrature data converted into analog signals by the digital / analog conversion means (11, 12) A coordinate conversion unit (4) for converting the signal point arrangement from a rectangular lattice arrangement to a honeycomb lattice arrangement, and the quadrature amplitude modulation unit (102) coordinates by the coordinate transformation unit (4). Quadrature amplitude modulation unit (2) that quadrature modulates the converted signals of the honeycomb lattice arrangement
A transmitter having: 2. A receiving device having a demodulating device used in a communication system for performing multi-level amplitude modulation / demodulation using a honeycomb-shaped signal point arrangement, wherein the demodulating device (200a) comprises a received multi-level quadrature amplitude modulated wave ( A synchronous detection unit (201) that synchronously detects QAM) to obtain an in-phase signal (x) and a quadrature signal (y), and outputs the in-phase signal (x) and the quadrature signal (y) from the synchronous detection unit (201). An equalization unit (204) that performs automatic equalization processing, and an in-phase signal (x) and a quadrature signal (y) that have been equalized by the equalization unit (204) are adjacent to each other in a honeycomb-shaped signal point arrangement from a rectangular coordinate axis. A coordinate conversion unit (202) that performs an operation of converting into three coordinate axes connecting points and gives three coordinate conversion output signals (x, u, v) corresponding to each coordinate axis, and the coordinate conversion unit. Based on the three coordinate conversion output signals (x, u, v) from (202) When a signal point of the received signal is determined, the signal determination section (203) that gives output data (Dout) is provided. Further, the signal for performing equalization control in the equalization section (204) is the signal determination section. A receiving device, which is created based on the output signal after the determination in the section (203).