JPH0834450B2 - Data transmission equipment - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data transmission device used for digital mobile communication and the like.

2. Description of the Related Art Conventionally, as shown in FIG. 2, in the data transmission apparatus of this type, in the transmission type T, when transmission data S ₁ as shown in FIG. (Amp
When using the litudeShift Keying) converter (MOD) 2,
The modulated signal S ₂ as shown in FIG. 3 (2) is modulated, amplified by the amplifier (Amp) 3, and then transmitted via the transmission antenna 4.

On the other hand, when the receiving side R ₀ receives this signal directly via the receiving antenna 5, receives the signal reflected and delayed by the building B, etc., and amplifies it by the amplifier (Amp) 6,
The received signal S ₃ has a waveform having distortion (multipath distortion) as shown in FIG. 3C, and then the demodulator (DEM) 7
When demodulated by, the demodulated signal S ₄ has a waveform having multi-pulse distortion as shown in FIG. 3 (4).

In addition, this multi-pulse distortion is such that radio waves reflected by various obstacles cancel each other with a delay difference or are strengthened (especially in a situation where the delay difference is a main factor of distortion and causes distortion, frequency selective fading It occurs because of.

The demodulated signal S ₄ having this multi-pulse distortion is an adder of delay devices (D) 8, 9, 10 and multipliers 11, 12, 13 and 14 when the dispersion of the delay time due to the multi-pulse is longer than the data transmission interval. Linear equalizer consisting of, delay device 16,17,18, multiplier 19,20,
A decision feedback equalizer composed of 21 and an adder 14, a comparator 15 and a coefficient updater 23 produce a signal S ₅ without multipulse distortion as shown in FIG. 3 (5).

Then, the signal S ₅ is judged to be “0” or “1” by the comparator 15, and the received data is restored.

The error rate in the above conventional example is, as shown in FIG.
Even if the static characteristic C ₁ is deteriorated to the dynamic characteristic C ₂ by the multi-pulse distortion, the characteristic C ₃ is improved, and the error rate can be reduced as much as possible by increasing the S / N.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the above-mentioned conventional data transmission apparatus, when the SN ratio becomes smaller and the error rate becomes larger than a certain value, the decision feedback equalizer diverges, which causes a problem that the error rate is rapidly deteriorated. there were.

Means for Solving the Problems In order to achieve the above object, the present invention is provided with a means for detecting an error rate, and when the error rate is equal to or more than a predetermined value, the coefficient updating of a decision feedback equalizer is stopped. It is the one.

Effect According to the present invention, therefore, when the error becomes worse than a certain value, the divergence can be prevented by stopping the coefficient update of the decision feedback equalizer, so that the error characteristic when there are more errors than the value is improved. can do.

Embodiment FIG. 1 shows an embodiment of the present invention, in which the left side of the drawing shows a transmitting side T and the right side of the drawing shows a receiving side R.

In the transmission side T of FIG. 1, 25 is an input terminal for the transmission data S ₁ , and 26 is a modulator (MO that modulates the transmission data S _1).
D), 27 are amplifiers (Amps) for amplifying the transmission data S ₂ modulated by the converter 26, and 28 is a transmission antenna for transmitting the transmission data from the amplifier 27.

In the receiving side R of FIG. 1, 29 is a receiving antenna for receiving data from the transmitting side T, and 30 is a receiving antenna 29.
Amplifier (Amp), which amplifies the modulated signal received via
1 is a demodulator (DE that demodulates the modulated signal S ₃ from the amplifier 30).
M), 32 is a delay device that delays the demodulated signal S ₄ from the demodulator 31 for each sample, 33 is a delay device that delays the output signal r ₁ ⁽ⁿ⁾ of the sample n from the delay device 32 for each sample, 34 delays the output signal r ₂ ⁽ⁿ⁾ from the delay unit 33 for each sample and
_This is a delay device that outputs ₃ ⁽ⁿ⁾ .

Further, 35 is a coefficient γ ₁ ^{(n) in} the output signal r ₁ ⁽ⁿ⁾ of the delay device 32.
Is a multiplier for multiplying the output signal r ₂ ⁽ⁿ⁾ of the delay unit 33 by a coefficient γ ₂ ⁽ⁿ⁾ , and 37 is a multiplier for multiplying the output signal γ ₃ ⁽ⁿ⁾ of the delay unit 34 by a coefficient γ ₃ ^(n). It is a multiplier that multiplies ₃ ⁽ⁿ⁾ , and each output signal is input to the adder 38. These delayed calls
32, 33, 34, multiplier, 35, 36, 37, adder 38 are linear equalizers (3
2 to 38).

39 is a comparator that determines the output signal of the adder 38 and restores the received data of "0" or "1", and 40 is a comparator 39
A delay device that delays the output signal of the sample for each sample, 41 is a delay device that delays the output signal S ₁ ⁽ⁿ⁾ of the delay device 40 for each sample, 4
2 is a delay device that delays the output signal S ₂ ⁽ⁿ⁾ of the delay device 41 for each sample to output a signal S ₃ ⁽ⁿ⁾ , and 43 is a coefficient b to the output signal S ₁ ⁽ⁿ⁾ of the delay device 40. Multiplier for multiplying ₁ ⁽ⁿ⁾ , 44 is a delay unit 41
Is a multiplier that multiplies the output signal S ₂ ⁽ⁿ⁾ of the delay b by the coefficient b ₂ ⁽ⁿ⁾ , and 45 is a multiplier that multiplies the output signal S ₃ ⁽ⁿ⁾ of the delay device 42 by the coefficient b ₃ ^(n). Is output to the adder 38.

In addition, these delay devices 40, 41, 42, multipliers 43, 44, 45, adder
The reference numeral 38 constitutes a decision feedback equalizer (38, 40 to 45).

Also, 46 is an adder for adding the output signal of the adder 38 and the reverse polarity signal of the output of the comparison call 39 to output a signal e ⁽ⁿ⁾ , 47
Is the output signal e ⁽ⁿ⁾ of the adder 46 and the following equation γ ₁ ^{(n + 1)} = γ ₁ ⁽ⁿ⁾ + αr ₁ ⁽ⁿ⁾ e ⁽ⁿ⁾ γ ₂ ^{(n + 1)} = γ ₂ ⁽ⁿ⁾ + αr ₂ ⁽ⁿ⁾ e ⁽ⁿ⁾ γ ₃ ^{(n + 1)} = γ ₃ ⁽ⁿ⁾ + αr ₃ ⁽ⁿ⁾ e ⁽ⁿ⁾ b ₁ ^{(n + 1)} = b ₁ ⁽ⁿ⁾ + βS ₁ ⁽ⁿ⁾ e ^{( n)} b ₂ ^{(n + 1)} = b ₂ ⁽ⁿ⁾ + βS ₂ ⁽ⁿ⁾ e ⁽ⁿ⁾ b ₃ ^{(n + 1)} = b ₃ ⁽ⁿ⁾ + βS ₃ ⁽ⁿ⁾ e ⁽ⁿ⁾ The coefficients γ ₁ ^{(n + 1)} , γ ₂ ^{(n + 1)} and γ ₃ ^{(n + 1)} of the next sample of the converters 35, 36 and 37 and the coefficient b ₁₀ ^{(n + )} output to the coefficient selector 49. ^This is a coefficient updater that updates ¹⁾ , b ₂₀ ^{(n + 1)} , and b ₃₀ ^{(n + 1)} . 49 indicates coefficients b _1,0 ^{(n + 1)} , b _2,0 ^{(n + 1)} , b _depending on the signal corresponding to the input signal level detected by the amplifier 30.
_{Use 3,0} ^{(n + 1)} as the coefficients b ₁ ^{(n + 1)} , b ₂ ^{(n + 1)} and b ₃ ^{(n + 1)} , or use the original coefficients b ₁ ⁽ⁿ⁾ and b ₂ ^{( n)} and b ₃ ⁽ⁿ⁾ are used as they are, and the coefficient selectors (SEL) and 48 for outputting to the coefficient terminals of the multipliers 43, 44 and 45 are equalized and restored from the comparator 39. This is an output terminal for receiving data.

 Next, the operation of the embodiment having the above configuration will be described.

In FIG. 1, on the transmitting side T, the transmission data S ₁ is input terminal
Input to 25 and then modulated by modulator 26
S ₂ is amplified by the amplifier 30 and sent out via the transmitting antenna 28.

On the other hand, the receiving side R directly receives this signal via the receiving antenna 29 and also receives a reflected signal from the building B or the like. In this case, this delay difference is longer than the data transmission interval.

The signal input via the receiving antenna 29 is amplified by the amplifier 30, demodulated by the demodulator 31 and linearly equalized (32 to
38), a decision feedback equalizer (38, 40 to 45), a comparator 39, an adder 46, a coefficient updater 47, and a coefficient selector 49, which decode the received data and output it to an output terminal 48.

In this case, the coefficient selector 49 outputs a signal corresponding to the signal input level obtained by the amplifier 30 (the error rate is estimated by this signal).
When the value is smaller than a certain set value (error rate is a predetermined value or more) based on, the coefficient b _1,0 ^{(n + 1) to} b _3, from the coefficient updater 47 to the decision feedback equalizer. Instead of ₀ ^{(n + 1)} , it is replaced with a value when it is larger than a certain set value, and the decision feedback equalizer (38,40
~ 45) to prevent divergence.

As shown in FIG. 4, the static characteristic C ₁ when there is no multi-pulse distortion does not become better than the value with an error rate even if the S / N is improved like the dynamic characteristic C ₂ when the distortion exists. If linear and decision feedback equalizers (32 to 38, 40 to 45) are added to this and multipath distortion is compensated for, characteristic C ₃ can be improved. However, if the S / N is good to some extent and the error rate is better than a certain value, a good error rate characteristic can be obtained, but if the S / N becomes less than that, the decision feedback equalizer (38, 40 ~ 45 ) Is diverged, and the error rate characteristic deteriorates rapidly. The present invention prevents this deterioration, and stops the divergence by stopping the update of the coefficient of the decision feedback equalizer (38, 40 to 45) when the error rate becomes worse than a certain set value, and the characteristic C ₄ is shown. Like all S /
A good error characteristic can be obtained for each N value.

EFFECTS OF THE INVENTION The present invention, as is clear from the above embodiment, prevents the divergence by stopping the coefficient update of the decision feedback type equalizer when the error rate becomes worse than a certain set value, and all S / N There is an advantage that a good error rate characteristic can be obtained throughout.

[Brief description of drawings]

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 data transmission device, and FIG. 3 is a block diagram of FIG. 1 and FIG. FIG. 4 is a waveform diagram showing a main signal of the apparatus, and FIG. 4 is an SN ratio versus error rate characteristic diagram of a received signal. 25 ... Transmission data input terminal, 26 ... Modulator, 27 ... Amplifier (Amp), 28 ... Transmission antenna, 29 ... Reception antenna, 30 ...
Amplifier, 31 ... Demodulator (DEM), 32, 33, 34 ... Delay device, 35, 3
6, 37 ... Multiplier, 38 ... Adder, 39 ... Comparator, 40, 41, 42 ... Delay device, 43, 44, 45 ... Multiplier, 46 ... Adder, 47 ... Coefficient updater, 48 ... Received data Output terminal, 49 ... Coefficient selector (SE
L).

Claims (1)

[Claims] 1. A demodulator for demodulating a received modulated signal, a linear equalizer and a decision feedback equalizer for equalizing the signal demodulated by the demodulator with a coefficient, and a coefficient updating for updating the coefficient. And a means for controlling the coefficient updater so as to detect whether the error rate of the received modulated signal is a predetermined value or more and stop the coefficient update of the decision feedback equalizer when the error rate is a predetermined value or more. Data transmission device having a.