JPS58116847A - Data transmission system - Google Patents

Abstract

PURPOSE:To prevent the detection output of a reception side from containing a phase error due to frequency variation of a carrier, by regarding three adjacent symbols as a unit of modulation and demodulation and carrying out logical processing at every unit. CONSTITUTION:A binary transmitted data string is converted by a binary-to-L scale converter 110 into an L-scale data string, which is further converted by a logical converter 120 into a data string which has specific correspondence relation between transmitted data and a phase angle phii+phii-2-2phii-1. This data string is modulated by a modulator 130 into a modulated wave corresponding to L phase angles. This modulated wave is transmitted to the reception side through a transmission circuit. On the reception side, the phase angle phii+phii-2-2phii-1 is detected from the modulated wave received by a detector 150. Then, a decoder 160 regenerates an L-scale data string corresponding to the phase angle, and further an L scale-to-binary converter 170 regenerates a binary data string. This phase string contains no phase error due to frequency variation of a carrier, so the regenerated data string is the same as the transmitted data string.

Description

[Detailed Description of the Invention] (1) Technical Field of the Invention The present invention relates to a data transmission system in a communication line, etc.
In particular, it relates to improving transmission quality by reducing the effects of carrier wave frequency fluctuations.

(2) Background of the Technology Carrier frequencies for data transmission in communication lines and the like, for example in wireless lines, are selected and used within the range of channels allocated by regulations.

The bit error rate ri caused by frequency fluctuations of the carrier wave tends to deteriorate as the carrier frequency increases, and a technical solution for obtaining high data quality is desired, especially when using a channel with a high carrier frequency.

(3) Prior Art and Problems As a typical method for detecting a received modulated wave on the receiving side of a data transmission system, there is a delay detection method with a simple circuit configuration.

FIG. 1 is a block diagram of an example of a conventional delay detector, which in principle obtains a detection output from the difference in phase angles corresponding to two adjacent symbols of a modulated wave.

In the figure, llt'! 12 is a phase shifter, 13 is a multiplier, and 14 is a low-frequency r-wave generator.

Now, 5l at terminal 10==ACO5(W t +p(t)) ・++++
When a modulated wave of ＋＋＋＋−・−・−・・■ is input,
■ passes through the delay device 11 and the phase shifter 12 and becomes S z =Acos[w (heavy-T)+J21(1-T
)+θ〕・・・・・・・・・・・・・・・・・・
■It becomes. Here, A is the amplitude of the modulated wave, W is the angular frequency,
yJ(1) is a phase modulated corresponding to transmission data. Further, T is a set delay time of a delay device, and this time is selected to be, for example, the modulation period, that is, the length of one symbol. 0
Assuming that 0 is a spider whose phase angle is appropriately adjusted by the phase shifter 12, ■ and ■ are multiplied by the multiplier 13, and from this output, the difference component is calculated by the low-frequency f-wave filter]4. Taken out 53=A2CO3(j!I(t)-521(t-T)+
ΔwT)......■ is output to the terminal 15. Here, △W is the angular frequency of the carrier wave changing, and if the center angular frequency of the carrier wave is WO, then
The relationship is Δw = w − w O.

However, it is well known that the Keyaki phase error is caused by the frequency fluctuation of the carrier wave, and is caused by a large amount that degrades the code rate of data transmission.

One way to reduce the phase error has conventionally been to stabilize the frequency fluctuations of the oscillator that generates the carrier wave as much as possible, but the configuration of the oscillator is complicated and expensive, and there are technical limitations. This is a problem that hinders the improvement of data transmission quality.

(4) Purpose of the present invention The present invention was made to solve this problem, and its purpose is to prevent the detection output on the receiving side from changing due to the frequency fluctuation even if there is a frequency fluctuation of the carrier wave. It is an object of the present invention to provide a data transmission system that obtains high data transmission quality without particularly stabilizing the frequency of a carrier wave oscillator by using a logic processing means that does not include a phase error.

(5) Structure of the Invention The present invention changes the conventional system in which two adjacent symbols are used as a unit of modulation and demodulation, but the unit of modulation and demodulation is changed to three adjacent symbols, including the previous one symbol, for each unit of modulation and demodulation. By performing certain logical processing on the signal, the detection output on the receiving side does not include phase errors due to frequency fluctuations of the carrier wave. That is, the phase angle of the modulated wave corresponding to the first symbol is 1, and then the symbol data is converted to the phase angle of the transmitted data and the modulated wave i+!
1-z-2j! 11-1, and then modulates and transmits the modulated wave. On the receiving side, the phase angle d i + d 2 - 2 i - 1 is detected from the received modulated wave. The present invention provides a data transmission system that achieves the object of the present invention by reproducing transmission data with reference to the phase angle and the correspondence relationship.

(6) Embodiments of the invention Hereinafter, embodiments of the invention will be described in more detail with reference to the drawings.

FIG. 2 is a diagram for explaining the basic idea of the present invention. In FIG. 2, 21, 30 and 31 are delay devices, 2
2 and 32 are phase shifters, 23 and 33 are multipliers, and 24 and 34 are low-frequency P wave shifters. In the following explanation, symbols etc. in the section (3) Prior Art and Problems explained above will be cited. When the modulated wave ■ is input to the terminal 20, the terminal 25 receives S s =A cos(521(t)-93(t-T
)+ΔW-T]......■, and 54=A cos(p(t-T)-0(t-2T)+Δ
W-T] . . . Φ are output respectively.

Here, the phases of the modulated waves corresponding to the 1st, i-]th and i-2th symbols are respectively l'+IzII
-1 and ter2, 52Ii=yj(t) l
Since r −1=l21(t−T) and 91i −2=da(t −2T ), the phase angle door of ■ and ■
and da4beam3=da1-doori-1+Δw-'f...
・・・・・・・・・[Phase] Da4-Da1-1-Da1-2+Δ
w −'f ・・・・・・・・・・・・■. Here, if we calculate the difference between ■ and ■, 96s −fh
= Gummy Tocho - 2-2 Dai i -1・・・・・・・・・・・・
・It becomes ■. That is, the difference ■ between the phase difference ■ corresponding to the modulated waves of the i-th symbol and the i-1th symbol and the phase difference ■ corresponding to the modulated waves of the i-th symbol and the i-2th symbol. It is shown that this does not include phase errors due to frequency fluctuations of the carrier wave.

Therefore, on the receiving side, the phase of the transmitted data and the modulated wave is detected in advance from the received modulated wave, and so that the transmitted data can be reproduced from this phase. 1'+1i-2-2yJi-1
If we perform logical conversion based on a certain correspondence relationship before modulating and transmitting the data, we can theoretically obtain high-quality data that is not affected by frequency fluctuations of the carrier wave. Transmission becomes possible. FIG. 3 shows the configuration of a transmission system when the present invention is applied to an L-phase modulation method (L=2°3.4...). #! In Figure 3, 2
The base number transmission data string (1) is converted from binary to L base converter 110
, it is converted into an L-adic data string (bl), and then in the logic converter 130, ci=bi-cl-2+2cH-1(
It is converted into a data string (Ci) under conditions that satisfy the relationship mod L). Next, the data string (CI) is associated with L phase angles by the modulator 130 and becomes a modulated wave.

The transmission data sequence is folded into the modulated wave as a phase sequence (phantom), and is transmitted to the receiving side via a transmission line. The phase sequence (Fi) inserted into the received modulated wave is
This shows that if noise or the like is mixed in during the transmission process, some errors will occur and the result will be 9 different from (gl+) at the time of transmission. From the phase sequence (ai), the detector 150 F1=12” +
52'1-2-2yJi-t phase sequence (Fi) Force is detected. Next, an L-adic data string (al) corresponding to the phase sequence (Fi) is reproduced in a post-encoder 160, and a binary data string (aI) is reproduced in an L-adic to binary converter.

In the above process, if the modulated wave is transmitted without error, the phase sequence +#+) will be equal to the phase sequence (%i), and the phase sequence (vl) detected from the phase sequence will include the carrier wave. Since phase errors due to frequency fluctuations are not included, the reproduced data sequence (ai) is the same as the transmitted data sequence (ai).

Next, an example in which the present invention is applied to a quadrature phase keying (QPSK) system will be described using FIGS. 3 to 7.
This will be explained more specifically.

In the QPSK system, a binary data string (m
i)=0.1.0.0. l, l, l, 1.0
．． 1.0.1.0.0.0゜0, 1.1.・・・・・・
Taking the case of transmitting ... as an example, this data example is binary → L
The path conversion circuit 110 performs quaternary encoding to obtain (bi)=1.
0.3, 3, 1, 1, 0, 0, 3.・・・・・・・・・
becomes. Next, the logic conversion circuit 120 (an example block diagram is shown in FIG. 4) performs conversion to satisfy the condition ci==bi-cl-2+2cl-1 (mod 4), so that (c i )=1 .0.2.3. ], 0.3.2.
0. ---...-... Here, the modulator 130
The quaternary numbers 1141 and 2°3 are respectively 0°, 90°,
Assuming that four-phase phase modulation is performed in association with 180° and 270°, the phase sequence (#i) of the modulated wave corresponding to (ci) is (yJi
)-0°, o', 1so°, 270°, 90', 0
°, 2700°180', 0°, etc.

The modulated wave transmitted via the line 140 is processed by a detector 150 (block diagrams of the embodiments are shown in FIG. 5 and FIG. 6) on the receiving side, where the phase sequence (Fi)=Fi
-z -2521! -0 is detected and (Fi)=2
70°, 2700, 900.90°, 0°, o',
2717°, . . . are output. Here, the demodulator 16
Assuming that 0 is decoded by corresponding to the phase 00°90°, 180°, 270°t, respectively, with the quaternary numbers 0.1, 2.3, the quaternary code string (bi) corresponding to the phase sequence (Fi) is get. The reproduced data string (ai) is the transmission data string (a
The content is the same as i).

Note that the first 4 bits of the transmission data string (11) have no meaning as decoded data because of the so-called delayed detection method. The above is summarized in Table 1.

Table 1 Note that the present invention is not limited to the above examples. For example, other polyphase modulation methods such as 4-phase modulation (K111), 8 out of 2 phases (off 7), P8 modulation method may be used as the Takeho method. Furthermore, the present invention is not limited to the polyphase phase modulation method, but is also applicable to horse wave number modulation (also known as MS) with a modulation index of 0.5, for example.
It is also possible to implement the present invention using other modulation methods such as the K method in which the transmission data and the phase of the modulated wave can correspond.

(7) Effects of the Invention As explained in detail above, the data transmission method according to the present invention is a method that theoretically does not suffer from the influence of carrier wave frequency fluctuations, and particularly improves data transmission quality on lines with high carrier frequencies. The improvement effect is significant. Furthermore, the frequency stability of the carrier wave oscillator on the transmitting side can be relaxed, and 1+
The detector at the receiving station uses a so-called delayed detection method and requires a simple circuit configuration, which also provides the advantage of making the equipment more economical and improving its reliability.

[Brief explanation of the drawing]

Figure 1 is a professional diagram of a delay detector, Figure 2 is a diagram for explaining the basic idea of the present invention, and Figure 3 is a transmitting and receiving system in which the present invention is applied to a phase modulation method. FIG. 4 is a block diagram of the logic converter in FIG. 3; FIGS. 5 and 6 are block diagrams of the embodiment of the detector 350 in FIG. 3. . In the figure, 110 is a binary to L-ary converter, 120 is a logic converter, 130 is a modulator, 14o is a line, 150 is a detector, 1
60 is a decoder,] 7oFiL base to binary converter. Mushroom S 21 Ootome

Claims (1)

[Claims] We will discuss a data transmission method in which transmission data is modulated and demodulated by associating it with multiple phases.Let the phase angle of the modulated wave corresponding to the i-th symbol be i, and then 41 symbols and 2
A certain correspondence relationship is established for the i=]th symbol before the symbol, and the transmission side logically converts the transmission data based on the correspondence relationship, modulates and transmits it, and the reception side calculates the phase from the received modulated wave. Detect Kakudo i+J21i-2-2 da i-1,
A data transmission method in which transmission data is reproduced with reference to the phase angle and the correspondence relationship.