JP2002064580A - Modulating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a modulating device that divides transmission data formed to be a frame into two sub frames, modulates them with a carrier having a frequency different from each sub-frame and synthesizes the modulated signals so as to attain a high transmission rate. SOLUTION: The modulating device that modulates data and transmits the modulated data is provided with a divider that divides data into first and second data, a first modulator that modulates the first data with a first carrier, a second modulator that modulates the second data with a second carrier, and an adder that sums the first data modulated by the first modulator and the second data modulated by the second modulator.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a modulation device. In particular, the present invention relates to a modulation device that divides framed transmission data into two subframes, modulates the data with a carrier having a different frequency for each subframe, and combines the modulated data to increase the transmission speed.

[0002]

2. Description of the Related Art In an analog wireless communication system, a modem for converting digital data into analog data is used to realize digital data communication. The modulation scheme of the modem includes ASK (Amplitude Shim).
ft Keying), FSK (Frequency)
Shift Keying), PSK (Phase S
shift Keying), QAM (Quadratu)
reAmplitude Modulation).

An analog wireless communication system has a narrow band because it is used for transmitting an analog voice signal. Specifically, it generally has a band of 2400 Hz in a range from 300 Hz to 2700 Hz. An analog wireless communication system has a narrow correlation bandwidth and an S / N (Si
(Gnal to Noise ratio) is bad. In addition, propagation conditions in an analog wireless communication system dynamically change. Therefore, it is difficult to increase the speed of the analog wireless communication system.

As a method of increasing the speed of an analog wireless communication system, there are a method of increasing the modulation speed, a method of increasing the number of levels, and a method of increasing both the modulation rate and the number of levels. If it is difficult to increase the modulation speed with a single carrier, an OFDM (Orthogonal Fr) that increases the speed by arranging a plurality of low-speed and narrow-band subcarriers.
equipment Division Multiple
xing) method is used. By using the OFDM method, high-speed transmission can be performed even on a transmission path with a narrow correlation bandwidth.

[0005]

However, in the method of increasing the modulation speed, if the transmission speed is to be doubled, the modulation speed must be doubled. Therefore,
In the narrow band of the analog wireless communication system, it is difficult to realize the band shortage.

In the method of increasing the number of multi-values, the distance between data is reduced by increasing the number of multi-values, so that the bit error rate characteristic is significantly deteriorated with the deterioration of S / N. FIG.
The theoretical bit error rate characteristics of the multi-level modulation scheme are shown. 16
In QAM, 64QAM, and 256QAM, BPSK (Binary Phase Shi) with a small number of multi-values is used.
ft Keying) and QPSK (Quatern)
ary / Phase Shift Keying), E _b / N ₀ (energy of signal per 1 bit /
The bit error rate is deteriorated as the noise power per 1 Hz is deteriorated. Comparing 256QAM and 16QAM,
256 QAM when the bit error rate is 10 ⁻⁷
It is required _E b / _{N 0} 9dB about extra than 16QAM is.

In the method of increasing both the modulation speed and the multi-level number, distortion occurs on the receiving side because components outside the band are cut off by the transmission band of the transmitter, and the bit error rate deteriorates. FIG. 2 shows the spectrum of a single carrier modulated wave.
Since the frequency bandwidth of the transmission data is widened by increasing the modulation speed, the component 72 outside the transmission band 70 is removed.

In the OFDM system, when used in a multipath environment, a section called a guard time must be inserted between data in order to reduce the influence of a delay wave. Insertion reduces the information speed. Further, in the OFDM system, since no band limitation is applied, components outside the band of the transmitter are removed, distortion occurs on the receiving side, and the bit error rate deteriorates. FIG. 3 (a)
Indicates the spectrum of the OFDM modulated wave. FIG. 3 (b)
Shows the spectrum of the band-limited OFDM modulated wave. Due to the band limitation, the component 74 outside the band of the transmission band 76 is removed.

Accordingly, an object of the present invention is to provide a modulation device that can solve the above-mentioned problems. This object is achieved by a combination of features described in the independent claims. The dependent claims define further advantageous embodiments of the present invention.

[0010]

According to a first aspect of the present invention, there is provided a modulation apparatus for modulating and transmitting data, wherein the data is divided into first data and second data. Modulator, a first modulator that modulates first data with a first carrier, a second modulator that modulates second data with a second carrier, and a modulator that is modulated by the first modulator. An adder is provided for adding the first data and the second data modulated by the second modulator.

The processing by the divider, the first modulator, the second modulator, and the adder is a digital arithmetic processing, and further includes a converter for converting the digital data added by the adder into analog data. Is also good.

[0012] The first modulator may quadrature modulate the first data, and the second modulator may quadrature modulate the second data.

[0013] The apparatus may further include a frame buffer for temporarily storing data and transmitting the data to the divider, wherein the divider divides the data received from the frame buffer into first data and second data.

According to a second aspect of the present invention, there is provided a demodulation device for demodulating received data, wherein a first data modulated by a first carrier is extracted from the received data.
And a second filter for extracting second data modulated by the second carrier from the received data,
A first demodulator for demodulating the second data, a second demodulator for demodulating the second data, the first data demodulated by the first demodulator, and the second demodulator demodulated by the second demodulator. A synthesizer for synthesizing the second data.

The above summary of the present invention does not list all of the necessary features of the present invention, and a sub-combination of these features may also be an invention.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described through embodiments of the present invention. However, the following embodiments do not limit the claimed invention and have the features described in the embodiments. Not all combinations are essential to the solution of the invention.

FIG. 4 shows a configuration example of an analog radio communication system including the modulation device 10 of the present invention. When the digital data to be transmitted is input to the modulation device 10 of the transmission side terminal, the modulation device 10 modulates the input digital data, converts it into analog data, and converts the digital data into an AGC (Autom
atic Gain Control) 12. Further, the microphone 11 receives an audio signal as analog data and outputs it to the AGC 12. The AGC 12 amplifies the input signal, adjusts the gain of the transmitted signal to be constant, and outputs the signal to the limiter 14. The limiter 14
The power is adjusted by limiting the amplitude of the input signal and output to the transmitter 18. The signal output from the transmitter 18 is P
A (Power Amplifier) 16 is input. The PA 16 amplifies the input signal and transmits the amplified signal to the receiving terminal via the transmitting antenna 19.

The receiver 24 of the receiving terminal receives the transmitted signal via the receiving antenna 22 and receives the signal.
Output to 0. The demodulation device 20 converts the input analog data into digital data, and then demodulates and outputs the digital data. The speaker 26 outputs analog data as an audio signal.

FIG. 5 shows a modulation device 10 according to this embodiment.
The function of is shown. In this embodiment, the transmission data speed is 9.6 kbps, and the frequency band is 300 Hz to 2700.
The description will be made on the assumption that the frequency is 2400 Hz, the multilevel modulation method is 32 QAM, and the number of carriers is 2.

The frame buffer 30 receives a binary data sequence (S1) as transmission data and generates a transmission frame. The length of one frame is set to about several hundred bits so that the number of symbols changes from several tens of symbols to one hundred and several tens of symbols after multi-level modulation. In this embodiment, since 32QAM is used, mapping is performed with 5 bits per symbol.
If one frame has 64 symbols, the number of bits in one frame is 320 bits. Further, since the number of carriers is 2, the number is doubled to 640 bits.

The divider 32 divides the data string (S1 ') framed by the frame buffer 30 into two data strings (S1'L, S1'H). As a method of division, any of a method of dividing into two before and after, and a method of distributing every one bit or several bits may be used. Here, a description will be given using a method of dividing the image into two in the front and the rear. Below, 2
The divided parts are referred to as L side and H side, respectively. The data sequence S1'L is input to the 32QAM mapper 34, and the data sequence S1'H is
Is input to

32QAM mappers 34 and 36
Arranges the input data sequence (S1'L, S1'H) on a 32QAM diagram with one symbol every 5 bits,
The symbol sequence (S2L) is divided into an I-phase signal and a Q-phase signal.
I, S2LQ, S2HI, S2HQ), and inputs the unique word adder 38 or 40.

The unique word adders 38 and 40
The input symbol sequence (S2LI, S2LQ, S2H
(I, S2HQ) with a unique word added to the head and output (S2LIU, S2LQUA, S2HIU, S2HQ)
U). The unique word is a symbol sequence having a pattern known in advance on the transmission side and the reception side, and is used for frame synchronization acquisition and training of the adaptive equalizer. Symbol string (S2LIU, S2LQ
U, S2HIU, S2HQUA) are input to the roll-off filters 42, 44, 46, or 48.

The roll-off filters 42, 44, 46, and 48 suppress the interference between codes by limiting the band of the input symbol sequence. In digital modulation, the roll-off rate is generally set to 0.5,
In the present embodiment, interference between adjacent carriers is suppressed by setting the width as narrow as 0.2 to 0.3. Data strings (S3LI, S3LQ, S3HI, S3) whose band is limited by the roll-off filters 42, 44, 46, and 48
HQ) is input to the quadrature modulator 50 or 52.

The quadrature modulator 50 applies the 900 Hz subcarrier (S) generated by the 900 Hz generator 51 to the input I-phase and Q-phase data strings (S3LI, S3LQ).
4) to generate a sub-modulated wave (S6). The quadrature modulator 52 generates a sub-modulated wave (S7) by multiplying the input I-phase and Q-phase data strings (S3HI, S3HQ) by a 2100-Hz sub-carrier (S5) generated by a 2100-Hz generator. I do.

The adder 54 comprises quadrature modulators 50 and 52
Synthesize the sub-modulation waves (S6, S7) generated by
A modulated wave (S8) is generated. The D / A converter 56 converts the modulated wave (S8), which is digital data, into an analog modulated wave (S8).
Convert to 9). Further, the low-pass filter 58 folds and removes the analog modulated wave (S9) and returns the final modulated wave (S9).
10) is generated.

FIG. 6 shows a spectrum of a dual carrier modulated wave (S10) according to the modulation method of the present invention. FIG.
The spectrum of the single carrier modulated wave shown in Fig. 3 and Fig. 3
Compared with the spectrum of the OFDM modulated wave shown in
Since the dual-carrier modulated wave (S10) has a small out-of-band component 78 reduced by the transmission band 80 of the transmitter,
The distortion on the receiving side can be reduced.

FIG. 7 shows the configuration of the quadrature modulator 50 or 52 of the modulation device 10. The product modulator 500 has 900H
The sub-carriers (S4, S5) output by the z generator 51 or the 2100 Hz generator
2 or 46 from the I-phase signal (S3LI, S3
HI). Also, the product modulator 502 has a 900
The sub-carriers (S4, S5) output from the Hz generator 51 or the 2100 Hz generator 53 are phases shifted by π / 2, and are roll-off filters 44 or 4.
8 modulates the Q-phase signal (S3LQ, S3HIQ) input. Then, the combining circuit 504 includes the product modulator 50
The two signals modulated by 0 and 502 are combined to generate a sub-modulated wave (S6, S7).

FIG. 8 shows a demodulator 20 according to this embodiment.
The function of is shown. When the modulation wave (S11) is input to the demodulation device 20, the A / D converter 60 converts the modulation wave (S11), which is analog data, into a digital data sequence (S12). The data string (S12) digitized by the A / D converter 60 is supplied to the 900 Hz bandpass filters 62 and 2
It is input to a 100 Hz bandpass filter 64. The 900 Hz bandpass filter 62 outputs a modulated wave (S
13L) is filtered and output. The 2100 Hz bandpass filter 64 outputs a modulated wave (S13) having a frequency of 2100 Hz.
H) is filtered and output. The filtered modulated wave (S13
L, S13H) are input to the quadrature detector 66 or 68.

The quadrature detector 66 includes a 900 Hz generator 67
900 Hz subcarrier generated by (S14)
Is multiplied by the input modulated wave (S13L) to generate I-phase and Q-phase data strings (S16LI, S16LQ). Further, the quadrature detector 68 has a 2100 Hz generator 69.
2100 Hz subcarrier generated by (S15)
Is multiplied by the input modulated wave (S13H) to generate I-phase and Q-phase data strings (S16HI, S16HQ).

The adaptive equalizers 70 and 72 estimate how the transmission / reception known unique word added to the transmission side is distorted after reception, and form a filter having characteristics reverse to those of the distortion to obtain the received data. Column (S16LI, S16LQ,
S16HI, S16HQ) are removed.

The 32 QAM demappers 74 and 76
Are the I- and Q-phase symbol sequences (S17LI, S17L) from which distortion has been removed by the adaptive equalizers 70 and 72.
Q, S17HI, S17HQ) are demapped and converted into bit strings (S18L, S18H). Reconstructor 78
Arranges two bit strings (S18L, S18H) converted by the 32QAM demappers 74 and 76 before and after to form a bit string (S19) having a frame configuration before being divided on the transmission side. The frame buffer 80 temporarily stores the bit string (S19) reconstructed by the reconstructor 78, adjusts the speed, and outputs it as 9.6 kbps bit stream data (S20).

FIG. 9 shows the configuration of the quadrature detector 66 or 68 of the demodulator 20. The product modulator 600 has 900H
The modulated wave (S13I, S13H) input from the z-band filter 62 or the 2100 Hz band filter 64 has 900H
The subcarriers (S14, S15) output by the z generator 67 or the 2100 Hz generator 69 are multiplied. Next, the low-pass filter 604 removes the multiplied subcarrier components and outputs a baseband I-phase signal (S16L
I, S16HI). Further, the product modulator 602 has a 900
The modulated waves (S13I, S13H) input from the Hz band filter 62 or the 2100 Hz band
The phase of the subcarriers (S14, S15) output by the Hz generator 67 or the 2100Hz generator 69 is set to π / 2.
Multiply the shifted subcarriers. Next, the low-pass filter 6
08 removes the multiplied subcarrier component and outputs a baseband Q-phase signal (S16LQ, S16HQ).
Thus, the quadrature detectors 66 and 68 can generate a baseband wave from the received modulated wave.

FIG. 10 shows the experimental results of the static error rate characteristics of the modulation system according to the present invention, which were carried out under the following specifications. Dual carrier 32QAM, transmission bandwidth 2.4
kHz (0.3 kHz to 2.7 kHz), symbol rate 1200 baud × 2, information rate 9.6 kbps, additional information rate 2.4 kbps, roll-off rate 0.2, carrier frequency 900 Hz and 2100 Hz. The static characteristic error rate of the dual carrier 32QAM according to the present invention is about 3 d less than the theoretical value when the bit error rate is 10 ⁻⁵ .
B is holding it down. Therefore, according to the dual carrier 32QAM according to the present invention, it is possible to realize a transmission rate similar to that of the conventional 256 QAM with an error rate characteristic similar to that of the conventional 32 QAM.

Although the present invention has been described with reference to the embodiment, the technical scope of the present invention is not limited to the scope described in the above embodiment. Various changes or improvements can be added to the above embodiment. It should be noted that such modified or improved embodiments may be included in the technical scope of the present invention.
It is clear from the description of the claims.

[0036]

As is apparent from the above description, according to the present invention, the transmission data framed is divided into two subframes, and each subframe is modulated by a carrier having a different frequency and synthesized. Thus, it is possible to provide a modulation device that increases the transmission speed.

[Brief description of the drawings]

FIG. 1 shows theoretical bit error rate characteristics of a multi-level modulation scheme.

FIG. 2 shows a spectrum of a single carrier modulation wave.

FIG. 3 shows a spectrum of an OFDM modulated wave.

FIG. 4 shows a configuration example of an analog wireless communication system including a modulation device 10.

FIG. 5 shows the function of a modulation device 10 according to the invention.

FIG. 6 shows a spectrum of a dual carrier modulated wave (S10).

7 shows a configuration of a quadrature modulator 50 or 52 of the modulation device 10. FIG.

FIG. 8 shows functions of the demodulation device 20 according to the present invention.

9 shows a configuration of a quadrature detector 66 or 68 of the demodulation device 20. FIG.

FIG. 10 shows an experimental result of a static error rate characteristic of a modulation system according to the present invention.

[Explanation of symbols]

 Reference Signs List 10 Modulator 20 Demodulator 30 Frame buffer 32 Divider 34 32 QAM mapper 38 Unique word adder 42 Roll-off filter 50 Quadrature modulator 51 900 Hz generator 53 2100 Hz generator 54 Adder 56 D / A converter 58 Low-pass filtering Unit 60 A / D converter 62 900 Hz bandpass filter 64 2100 Hz bandpass filter 66 Quadrature detector 67 900 Hz generator 69 2100 Hz generator 70 Adaptive equalizer 74 32 QAM demapper 78 Reconstructor 80 Frame buffer

Claims (5)

[Claims] 1. A modulator for modulating and transmitting data, comprising: a divider that divides the data into first data and second data; and a modulator that modulates the first data with a first carrier. A first modulator that modulates the second data with a second carrier; a first modulator that is modulated by the first modulator; and a second modulation that modulates the second data with a second carrier. A modulator for adding the second data modulated by the modulator. 2. The processing by the divider, the first modulator, the second modulator, and the adder is a digital arithmetic processing, and converts the digital data added by the adder into analog data. The modulator according to claim 1, further comprising a converter that performs the conversion. 3. The apparatus according to claim 1, wherein the first modulator quadrature-modulates the first data, and the second modulator quadrature-modulates the second data. Modulation device. 4. A frame buffer for temporarily storing the data and transmitting the data to the divider, wherein the divider converts the data received from the frame buffer into first data and second data. 2. The modulation device according to claim 1, wherein the signal is divided into two. 5. A demodulation device for demodulating received data, comprising: a first filter for extracting first data modulated by a first carrier from the received data; and a demodulator for demodulating the received data by a second carrier. A second filter that extracts the second data from the received data, a first demodulator that demodulates the first data, a second demodulator that demodulates the second data, A demodulator, comprising: a combiner that combines the first data demodulated by a first demodulator and the second data demodulated by the second demodulator.