JPH02215237A - Data transmitter - Google Patents

Abstract

PURPOSE:To attain excellent transmission under the frequency selective fading by using a reference signal sent while being added to a transmission data at a reception section, estimating the characteristic of a radio line and using the estimated value so as to apply maximum likelihood decoding to the received data. CONSTITUTION:A timing detector 13 uses a correlation calculated by a correlation device 12 to detect a timing of a reference signal inserted by a transmission section and uses the timing so as to segment a signal with a prescribed correlation from the correlation device 12. A line estimate device 14 estimates the characteristic of a radio line with the signal with a prescribed correlation segmented by the detector 13. A maximum likelihood decoder 15 applies maximum likelihood decoding to a base band signal detected by an orthogonal detector 11 based on the estimated value of the characteristic of the radio line estimated by the estimate device 14 and recovers the decoded data. A rate converter 16 extracts a reference signal from the decoded data recovered by the decoder 15, decreases the transmission rate to the original transmission rate and outputs an output from an output terminal 17.

Description

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

2. Description of the Related Art Conventionally, as shown in FIG. 3, this type of data transmission apparatus includes a modulator 18 that modulates a carrier frequency signal with transmission data, and an antenna 2o that amplifies the signal modulated by the modulator 18. a transmitting unit including an amplifier 19 that transmits radio waves via an antenna 21; an amplifier 22 that receives and amplifies the radio waves from the transmitting unit via an antenna 21; and demodulating the received signal amplified by the amplifier 22 into received data. demodulator 2
3, and is configured to transmit data via a wireless line.

Problems to be Solved by the Invention However, in the conventional data transmission device described above, as shown by the arrows in FIG. When multipath distortion, so-called frequency selective fading, occurs, there is a problem in that the error rate characteristics of received data are extremely degraded.

SUMMARY OF THE INVENTION In view of the above-mentioned conventional problems, it is an object of the present invention to provide a data transmission device that can transmit data satisfactorily even when frequency selective fading occurs.

Means for Solving the Problems In order to achieve the above object, the present invention includes, in a transmitting section,
A reference signal for estimating the characteristics of the wireless line is added to the transmitted data and transmitted, and the receiving section estimates the characteristics of the wireless line using this reference signal and performs maximum likelihood decoding of the received data using this estimated value. This is what I did.

Effects With the above configuration, the present invention performs maximum likelihood decoding of received data according to the characteristics of the radio channel in case frequency selective fading occurs, so that data can be transmitted satisfactorily.

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, and FIG. 2 is an explanatory diagram showing a format of a transmission signal of the data transmission device of FIG.

In the upper part of FIG. 1, 1 is an input terminal for transmission data, 2
4 is a rate converter that increases the transmission rate of transmission data under the control of the controller 3 and generates a predetermined period of time during which there is no transmission data, for example, every fixed period of each frame; As shown in FIG. 2, a reference signal generator 6 generates a reference signal for estimating the characteristics of a wireless channel. This is an adder for inserting the reference signal from the signal generator 4.

Further, 6 is a modulator that modulates the carrier frequency signal with the signal from the adder 6, 7 is an amplifier that amplifies the signal modulated by the modulator 6, and 8 is a radio wave that modulates the signal modulated by the amplifier 7. These members 1 to 8 constitute a transmitter.

In the lower part of FIG. 1, 9 is an antenna that receives the radio signals from the transmitting units 1 to 8, 10 is an amplifier that amplifies the received signal from the antenna 9, and 11 is the received signal amplified by the amplifier 10. This is a quadrature detector that detects baseband signals.

Further, 12 is a correlator that calculates a correlation value between the baseband signal detected by the orthogonal detector 11 and the reference signal inserted in the transmitter, and 13 is a correlator that calculates a correlation value between the baseband signal detected by the quadrature detector 11 and the reference signal inserted in the transmitter. A timing detector 14 detects the timing of the reference signal inserted in the section and uses this timing to extract a predetermined signal of the correlation value from the correlator 12. A channel estimator 16 that estimates the characteristics of the radio channel based on the signal estimates the baseband signal detected by the orthogonal detector 11 based on the estimated value of the radio channel characteristics estimated by the channel estimator 14. The maximum likelihood decoder 1e that decodes and reproduces decoded data extracts a reference signal from the decoded data reproduced by the maximum likelihood decoder 16, lowers it to the original transmission rate, and outputs it via the output terminal 17. These members 9 to 17 constitute a receiving section.

Next, the operation of the above embodiment will be explained.

As shown by the arrows in Figure 1, multipath distortion that cannot be ignored with respect to the Nyquist interval of data transmission is caused by the difference in delay time of radio waves on each propagation path in the wireless line.
So-called frequency selective fading occurs.

Therefore, the receiving section calculates a correlator between the detected baseband signal and the reference signal inserted in the transmitting section, estimates the characteristics of the wireless line using a predetermined signal of this correlation value, and uses this estimated value. Since the baseband signal is maximum-likelihood decoded based on the baseband signal and reproduced as decoded data, the error rate characteristics of the received data can be improved, and therefore the received data can be reproduced with fewer errors.

DETAILED DESCRIPTION OF THE INVENTION As described above, in the present invention, a reference signal for estimating the characteristics of a wireless channel is added to transmission data in a transmitting section, and the receiving section estimates the characteristics of the wireless channel using this reference signal. is estimated and the received data is subjected to maximum likelihood decoding using this estimated value, so that data can be transmitted satisfactorily even if frequency selective fading occurs.

[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 an explanatory diagram showing the format of a transmission signal of the data transmission device of FIG. 1, and FIG. FIG. 2 is a block diagram showing a data transmission device. 2, 16...Rate converter, 3...Controller, 4...
・Reference signal generator, 6... Adder, 6... Modulator,
7,1o...Amplifier, 8,9...Antenna, 11.
... Quadrature detector, 12... Correlator, 13... Timing detector, 14... Line estimator, 16... Maximum likelihood decoder.

Claims (1)

[Claims] A transmitting section that adds a reference signal to transmission data to estimate the characteristics of a wireless channel, and estimates the characteristics of the wireless channel using the reference signal added by the transmitting section, and uses this estimated value to optimize the received data. A data transmission device comprising a receiving unit that performs decoding.