JPS63141424A - Data transmission equipment - Google Patents

Abstract

PURPOSE:To improve the transmission characteristic by sending a signal being the modulated transmission signal by 1st modulator and a signal modulated by a 2nd modulator with a delay of 1-bit or over from a sender side and eliminating multi-path distortion by an equalizer at the receiver side. CONSTITUTION:A signal obtained by modulating (26) a transmission signal from a terminal 25 without any modification and a signal obtained y modulating (28) the transmission signal with a delay (27) of one-bit or over are added (29), amplified (30) and sent from antenna 31. A reflected wave from the transmission antenna 31 and a building B is received (32), amplified (33) and demodulated An output of a linear equalizer comprising delay devices 35-37 and multipliers 38-40 is given to an adder 41. A comparator 42 decides the output of the adder 41 to output '0' or 1' and gives it to a decision feedback equalizer comprising delay devices 43-45 and multipliers 46-48 and its output is given to the adder 41. The input and output of the comparator 42 are added (49) to the coefficient of a coefficient revision device 50 and to give it to the multipliers 38-40, 46-48. Thus, the variance in delay time of radio wave propagation with respect to radio wave propagation is larger than the data transmission interval to improve the reception characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a data transmission device used in a digital mobile radio device or the like that transmits data via a radio line.

BACKGROUND ART Conventionally, in this type of data transmission apparatus, as shown in FIG. 2, on the transmitting side, when transmission data S1 such as two pages as shown in FIG.
K (Amplitude 5hift Keying)
The signal is modulated by a modulator (MOD) 2 into a modulated signal S2 as shown in FIG.

On the other hand, when the receiving side receives this signal directly via the receiving antenna 5, and also receives the signal reflected and delayed by building B etc., and amplifies it with the amplifier 6, this amplified signal S3 becomes as shown in FIG. When the waveform has a distortion (multipath distortion) and is then demodulated by the demodulator (DEM) 7, the demodulated signal S4 becomes as shown in FIG.
The resulting waveform has multipath distortion.

Similarly, this multipath distortion occurs because radio waves reflected by various obstacles cancel or intensify each other, resulting in line distortion that fluctuates over time.

This demodulated signal S4 having multipath distortion is processed by a delay unit (1)) if the delay time dispersion due to multipath is longer than the data transmission interval.8.9.1 Multipliers 11, 12.
13, a decision feedback equalizer consisting of a delay 16°3 hepar 17.18, a multiplier 19, 20, 21, an adder 14, a comparator 15, and a coefficient updater 2.
3, a signal S5 without multipath distortion is obtained as shown in FIG. 3.

Then, the signal S5 is set to "0" or "1" by the comparator 15.
” and the received data is restored.

Problems to be Solved by the Invention However, the conventional data transmission device described above has the following problems.

First, the error rate when there is no fading due to multipath distortion in the wireless line is as shown in the static characteristic CI in Figure 4.
As the S/N ratio of the amplified signal S3 increases, it rapidly deteriorates.

On the other hand, if fading due to multipath exists, the S/N of the signal S3 will change as shown in the dynamic characteristic C2 in the absence of the linear equalizers 8 to 13 and the decision feedback equalizers 16 to 21.
Even if the ratio is increased, the error rate cannot be improved to below a predetermined error rate, but if the dispersion of delay time of radio wave propagation due to multipath is longer than the data transmission interval, linear equalizers 8 to 13 and decision feedback type The equalizers 16 to 21 can improve the error rate, as shown in characteristic C3.

Therefore, in the conventional data transmission device described above, when the dispersion of the delay time of radio wave propagation due to multipath is shorter than the data transmission interval, there is a problem that the error rate cannot be improved as shown in characteristic C3. .

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a data transmission device that can achieve good transmission characteristics regardless of the delay time of radio wave propagation due to multipath.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention includes, on the transmitting side, a first modulator that modulates transmission data, a delay device that delays the transmission data by at least one bit, and the A second modulator that modulates the transmission data delayed by the delay device is provided, and the first and second modulated signals are transmitted to the receiving side.

Operation Page 5 According to the present invention, with the above configuration, the signal received by the receiving side becomes a signal in which the dispersion of the delay time of radio wave propagation is longer than the data transmission interval. Therefore, the receiving side uses a linear equalizer and a decision feedback equalizer. Therefore, it is possible to receive data with a small error rate.

EXAMPLES Hereinafter, the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a data transmission device according to the present invention, with the lower left side of the figure showing the transmitting side and the right side showing the receiving side.

In the lower left of FIG. 1, 25 is an input terminal for transmission data, 26 is a modulator (MOD) that modulates transmission data,
27, a delay device (D) that delays transmission data by at least one bit; 28, a modulator that modulates the transmission data delayed by the delay device 27; 29, a modulator 26.27;
An adder 30 for adding modulated signals from the adder 29
an amplifier (Amp) for amplifying the modulated signal from the
It is a transmitting antenna.

Also, on the right side of FIG. 1, 32, a receiving antenna,
33, an amplifier that amplifies the 6-page modulated signal received via the receiving antenna 32; 34, a demodulator (DEM) that demodulates the modulated signal from the amplifier 33; 35, samples the demodulated signal from the demodulator 34; A delay device that delays each time, 3
6 is the output signal r1(n
) for each sample, 37 is a delay device 36
This is a delay device that delays the output signal r2(n) from sample by sample and outputs the signal r3(n).

Further, 38 is a multiplier that multiplies the output signal r1(n) of the delay device 35 by a coefficient γ1(n), and 39 is a multiplier that multiplies the output signal r2(n) of the delay device 36 by a coefficient γ2(n). A multiplier 40 adds a coefficient γ to the output signal r3(n) of the delay device 37.
3(n), and each output signal is input to the adder 41. These delay devices 35, 36 .
37, multipliers 38, 39, 40 are linear equalizers 35 to 4
It constitutes 0.

42C, determine the output signal of the adder 41 and determine whether it is "0" or "
A comparator 43 is a comparator 43 which restores the received data to "1".
A delay device 44 delays the output signal of No. 2 for each sample.
A delay device 45 delays the output signal 51(n) of the delay device 43 to the sample 7 on a pulse-by-pulse basis, and a delay device 45 delays the output signal 52(0) of the delay device 44 on a sample-by-sample basis and outputs a signal 53(n). The delay device 46 outputs the output signal S1 of the delay device 43.
A multiplier 47 for multiplying the coefficient (n) by the coefficient (n)
) A multiplier that multiplies the output signal 52 (n) of the delay 44 by a coefficient b2 (n), 48 is the output signal 53 (n) of the delay device 45
is a multiplier that multiplies the coefficient b3(n) by a coefficient b3(n), and each output signal is input to the adder 41. These delay devices 43
．． 44, 45, and multipliers 46, 47, and 48 constitute decision feedback equalizers 43 to 48.

49, an adder 5 that adds the output signal of the adder 41 and the output signal of the comparator 42 and outputs a signal 6 (n);
0 is the output signal e (n) of the adder 49 and the following formula % formula %
)() yoshi, coefficient multiplier 38.39.40.46.47 respectively
．． 48(n+1) (n+1) (n+1
) of the next sample coefficient γ] , γ2 , γ3
, b, (n+1), b2 (n+1), b3 (n+1) are updated coefficient updaters, and 51 c is an output terminal for receiving data.

Next, the operation of the embodiment according to the above configuration will be explained.

On the transmission side in FIG. 1, when transmission data is input to the input terminal 25, it is modulated by the modulator 26, and the delay
7, the signal is delayed by one bit or more and then modulated by the modulator 28. The signals modulated by modulators 26 and 28 are summed by adder 29, amplified by amplifier 30,
It is transmitted via the transmitting antenna 31.

On the other hand, when the receiving side receives this signal directly via the receiving antenna 32 and also receives the reflected signal from Building B etc., this received signal is affected by multipath and The delay modulation signal causes a signal whose delay time dispersion is longer than the data transmission interval.

The signal input via the receiving antenna 32 is amplified by the amplifier 33, demodulated by the demodulator 34, and then processed by linear equalizers 35 to 40, decision feedback equalizers 41 to 48.9, A-PA adder 41, and a comparator. 42, adder 49, coefficient updater 50
The data is restored to received data and output to the output terminal 51.

Therefore, even if the output signal of the amplifier 33 is a signal having the dynamic characteristic C2 shown in FIG.
, the decision feedback equalizers 43 to 48 can convert the received data into data having a characteristic C3 with a low error rate.

That is, in the above embodiment, the delay device 27°28 on the transmitting side
However, it provides the same effect of making the dispersion of the delay time of the received signal due to multipath longer than the data transmission interval, and can realize good transmission characteristics regardless of the delay time of radio wave propagation due to multipath.

Similarly, in the above embodiment, the adder 29 on the transmitting side is configured to add the normal modulated signal and the delayed modulated signal and transmit it, but two transmitting antennas are provided and each modulated signal is added in the air. It may be configured as follows.

As described above in Advantage 10 of the Invention, the present invention includes a first modulator that modulates transmission data, and at least one modulator that modulates transmission data on the transmission side.
A delay device that delays by at least one bit and a second modulator that modulates the transmission data delayed by the delay device are provided, and the first and second modulated signals are transmitted to the receiving side. The signal received by the receiving side is a signal in which the dispersion of the radio wave propagation delay time is longer than the data transmission interval, and therefore good transmission characteristics can be achieved regardless of the radio wave propagation delay time due to multipath.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of a data transmission device according to the present invention, FIG. 2 is a block diagram showing a conventional example, and FIG. 3 is a waveform diagram of main signals of the circuit shown in FIG. Figure 4 shows
FIG. 3 is a graph showing the S/N ratio versus error rate characteristic of a received signal. 25, transmission data input terminal, 26.28...modulator,
27... Delay device, 29. Adder, 35-38... Linear equalizer, 43-48... Decision feedback equalizer.

Claims (1)

[Claims] a first modulator for modulating transmission data on the transmitting side; a delay device for delaying the transmission data by at least one bit; a second modulator for modulating the transmission data delayed by the delay device; and means for transmitting a second modulated signal to a receiving side, the receiving side having a linear equalizer and a decision feedback equalizer for removing multipath distortion from a signal transmitted from the transmitting side.