JPH06232922A - Communication method and its system - Google Patents

Abstract

PURPOSE:To obtain the communication method and its device in which a transmission level is controlled corresponding to a data transmission error rate of a transmission line or the coding system is adaptively revised. CONSTITUTION:A convolution coding circuit 11 executes parallel convolution coding corresponding to a coding modulation system of a transmitter 1. A signal allocation circuit 12 allocates a signal about a parallel coding output signal. A modulation circuit 23 applies quadrature modulation to a carrier signal. A control information reception circuit 21 receives a control information signal. An output level control circuit 22 controls output power of an output amplifier circuit 24 based on the control information. A demodulation circuit 30 applies quadrature detection to a reception signal from the transmitter 1. A Viterbi decoder 41 decodes data by the Viterbi decoding system based on the I and Q signals received from the demodulation circuit 30. A respectively estate monitor circuit 42 evaluates the data transmission error rate on a transmission line 50 based on a path metric to generate a control signal. A control information transmission circuit 43 sends the control signal to the transmitter 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication method and a method thereof which can improve the transmission efficiency of data communication by a trellis coded modulation method.

[0002]

2. Description of the Related Art In a communication system on a communication path with severe power limitation, power is generally reduced by using an error correction code to obtain a coding gain. In such a communication system, it is common to perform convolutional coding on the transmitter side and Viterbi decoding on the receiver side, but the trellis coded modulation method that combines the modulation method and the coding method is particularly noted. Has been done.

This trellis coded modulation system convolutionally codes input data, and also uses this convolutional code as a user code.
This is a method of allocating to modulation signal points so that the maximum Crid distance is maximized, and the receiver side uses the Viterbi algorithm for decoding. Specific trellis coded modulation methods include, for example, the coded 8PSK method, the coded 16QAM method, the coded 32QAM method, and the coded 64QAM method.

The structures of a conventional transmitter 9 and a conventional receiver 7 which transmit data by trellis code modulation will be described by taking data transmission by the coded 16QAM system as an example. FIG. 12 is a diagram showing a configuration of a general conventional transmitter 9 that transmits data by the trellis code modulation method. FIG. 13 is a diagram showing a configuration of a conventional receiver 7 that receives data encoded by the trellis code modulation method. FIG. 14 is a diagram showing the configuration of the conventional Viterbi decoding circuit 8 of the conventional receiver 7.

In FIG. 12, the convolutional encoder 91 is
The data input to be transmitted is subjected to parallel convolutional coding at a rate corresponding to the coding method set from the outside, and is input to the signal allocation circuit 92.

The signal allocation circuit 92 includes a convolutional encoder 91.
A signal is assigned to the parallel convolutional code output of and is input to the QAM modulation circuit 93 as an I signal and a Q signal.
The local oscillation circuit 94 generates a carrier signal and inputs it to the hybrid circuit 95 and the mixer 96a. The hybrid circuit 95 delays the phase of the carrier wave signal generated by the local oscillation circuit 94 by 90 ° and inputs the delayed carrier wave signal to the mixer 96b.

The mixers 96a and 96b respectively perform multiplication of the I signal and the carrier signal, and multiplication of the Q signal and the carrier signal delayed in phase by 90 ° in the hybrid circuit 95.
The adder circuit 97 adds the output signals of the mixers 96a and 96b and inputs them to the BPF 98. The BPF 98 filters a predetermined frequency component of the output signal of the adder circuit 97 to obtain a modulated output signal.

The configuration of the receiver 7 will be described below with reference to FIG. The receiver 7 is composed of a QAM demodulation circuit 70 and a Viterbi demodulation circuit 80.

In the QAM demodulation circuit 70, the carrier wave reproduction circuit 75 reproduces a carrier wave signal based on the output signals of the A / D conversion circuits 73a and 73b, and inputs it to the mixer 71a and the hybrid circuit 74. The hybrid circuit 74 phase shifts the carrier signal reproduced by the carrier reproducing circuit 75 by 90 ° and inputs the carrier signal to the mixer 71b.

Each of the mixers 71a and 71b multiplies the carrier signal regenerated by the carrier regenerating circuit 75 by the modulated output signal of the transmitter 9 and inputs it to the LPF 72a, and the regenerated carrier shifted by 90 ° in the hybrid circuit 74. The signal is multiplied by the modulated output signal of the transmitter 9 to be converted into a base band, and the result is input to the LPF 72b.

The LPFs 72a and 72b filter the frequency components below a predetermined high cutoff frequency of the output signals of the mixers 71a and 71b, respectively, and the A / D conversion circuit 73.
a and 73b. A / D conversion circuits 73a and 73b
Respectively perform analog / digital (A / D) conversion on the output signals of the LPFs 72a and 72b, and input them to the Viterbi demodulation circuit 80 as digital I and Q signals.

The Viterbi demodulation circuit 8 will be described below with reference to FIG.
The configuration of 0 will be described. Branch metric generation circuit 81
Is the I signal and Q input from the QAM demodulation circuit 70.
The square of the Euclidean distance (branch metric) is calculated based on the signal.

The ACS circuit 83 performs maximum likelihood path calculation based on the input branch metric, calculates the branch with the highest likelihood, controls the path memory 84, and stores the state already stored in this branch metric. A metric is added, the minimum value of the state metric is subtracted from the added value, and the normalized value is stored as a new state metric.

The path memory 84 stores the path selected under the control of the ACS circuit 83. The P / S conversion circuit 85 performs parallel / serial conversion on the maximum likelihood path in parallel format, which is the output of the path memory 84, and outputs it in the format of serial data.

The operation of the conventional transmitter 9 and the conventional receiver 7 will be described below. The conventional transmitter 9 performs convolutional coding on a data input by a convolutional encoder 91 at a rate corresponding to, for example, a coded 8PSK system, and a signal allocation circuit 92 for the convolutionally coded data.
Signal allocation corresponding to the encoding method set so that the minimum Euclidean distance between the signals becomes maximum, and I
It is input to the QAM modulation circuit 93 as a signal and a Q signal.

Further, the QAM modulation circuit 93 modulates the I signal and the Q signal input from the signal allocation circuit 92 and sends them to the receiver 7. In the QAM modulation circuit 93, the local oscillation circuit 94 generates a carrier signal. This carrier signal is directly used for the mixer 96a and the hybrid circuit 95.
Entered in.

The carrier signal input to the hybrid circuit 95 is phase-shifted by 90 ° and input to the mixer 96b. The mixers 96a and 96b multiply the carrier signals having different phases by the I signal and the Q signal output from the signal allocation circuit 92, respectively. The two multiplication results are added by the adding circuit 99, band-limited by filtering in the BPF 98, and sent to the receiver 7.

The receiver 7 which receives the signal from the conventional transmitter 9 is driven by the mixers 71a and 71b.
The carrier wave signal reproduced in 1 and this carrier wave signal are respectively multiplied by the signal shifted in phase by 90 ° in the hybrid circuit 74. The multiplication results are LPFs 72a and 72b, respectively.
Filtered by the A / D conversion circuit 7
A / D conversion is performed by 3a and 73b. The output signals of the A / D conversion circuits 73a and 73b are input to the Viterbi demodulation circuit 80 as an I signal and a Q signal, respectively.

The branch metric generation circuit 81 has a QA
I signal (cos axis signal) input from the M demodulation circuit 70
And a branch metric is calculated based on the Q signal (sin axis signal). The ACS circuit 83 calculates the maximum likelihood branch based on the branch metric calculated by the branch metric generation circuit 81, and controls the path memory 84 to store the selected path for a predetermined number of stages. Path memory 8
Since the output data of No. 4 is in parallel format, it is converted into a serial format signal by the P / S conversion circuit 85 and output as decoded data.

[0020]

DISCLOSURE OF INVENTION Problems to be Solved by the Invention In the above-described device for performing data communication by the trellis coded modulation system,
Generally, a transmission error is less likely to occur when the reception signal level in the receiver is high, and conversely, a transmission error is likely to occur when the reception signal level is low.

From the above, when the received signal level at the receiver is high, it is possible to reduce the transmitted output signal level of the transmitter to reduce the transmitted energy. Also,
It is effective to improve the transmission efficiency by using the higher-efficiency multilevel modulation method while keeping the transmission signal level unchanged. Therefore, if the data transmission error rate is low enough,
It is preferable to reduce the transmission output and perform the transmission by a multilevel coded modulation method.

However, although the data transmission error occurring between the transmitter and the receiver is closely related to the received signal level, for example, it is greatly affected by noise mixed from the outside on the transmission line, and only the received signal level is present. There has been a problem that the data transmission error rate cannot be properly evaluated.

Therefore, conventionally, it is difficult to adaptively control the transmission level or change the coding method according to the data transmission error rate of the transmission path, and it is not actually performed at present. However, there is a problem that efficient transmission is not always performed according to the state of the transmission path.

The present invention has been made in view of the above-mentioned problems of the prior art, and it is possible to appropriately evaluate the state of the transmission line, that is, the data transmission error rate, and thus to cope with the data transmission error rate of the transmission line. To provide a communication method and a method capable of adaptively controlling the transmission level or changing the coding method and always performing efficient transmission corresponding to the state of the transmission path. With the goal.

[0025]

In order to achieve the above object, a communication method and method according to the present invention transmit a signal code-modulated by a trellis code modulation method, and transmit the code-modulated signal. And the minimum state metric is cumulatively added a predetermined number of times, and the transmission power of the code-modulated signal is set based on the cumulative addition result.

In addition, one of the plurality of trellis coded modulation systems is selected to perform coded modulation of the signal, the coded modulated signal is transmitted, and the coded modulation system is assumed. Then, the code-modulated signal is received, the minimum state metric is cumulatively added a predetermined number of times, the coding / modulation method is selected and the transmission power is set based on the cumulative addition result, or Do one of the two.

Further, the phase of the code-modulated signal is further corrected based on the result of the cumulative addition.

Further, the assumption of the coded modulation method is further changed based on the result of the cumulative addition.

Further, the selection of the coded modulation method and the assumption of the coded modulation method, or any one of these is at least once from the start to the end of reception of the coded and modulated signal. It is characterized by being performed only.

Further, the plurality of trellis coded modulation schemes are characterized by including at least 8PSK, 16QAM, 32QAM, and 64QAM, or any combination thereof.

When the result of the cumulative addition increases, a coded modulation system having a lower transmission rate than the coded modulation system used at that time is selected from the plurality of trellis coded modulation systems. It is characterized by doing.

Further, when the result of the cumulative addition decreases, a coding modulation system having a higher transmission rate than the coding modulation system used at that time is selected from the plurality of trellis coding modulation systems. It is characterized by doing.

Further, a signal code-modulated by the trellis code-modulation system is received, the minimum state metric is cumulatively added a predetermined number of times, the state of the transmission line is evaluated based on the cumulative addition result, and the evaluation is performed. Based on the results of
And, it controls reception or one of these.

Further, it has a transmitter and a receiver, and the transmitter has a control signal receiving means for receiving a control signal from the receiver, and a transmission power for setting the transmission power based on the control signal. The receiver includes a setting means, a code modulation means for code-modulating data by trellis code modulation, and a signal sending means for sending the code-modulated signal to the receiver at the transmission power. Is a cumulative addition device that receives the code-modulated signal and cumulatively adds a minimum state metric a predetermined number of times, and a control that generates the control signal based on the result of the cumulative addition and sends the control signal to the transmitter. Signal transmission means.

The transmitter further includes a control signal receiving means for receiving a control signal from the receiver, a transmission power setting means for setting the transmission power based on the control signal, and a trellis code. It is characterized in that it has a code modulation means for code-modulating data by code modulation and a signal sending means for sending the code-modulated signal to the receiver at the transmission power.

Further, a receiver is provided, and the receiver receives the code-modulated signal and cumulatively adds the minimum state metric for a predetermined number of times, and a cumulative addition device based on a result of the cumulative addition. Control signal transmitting means for generating the control signal and transmitting it to the transmitter.

Further, the receiver is further characterized by further comprising phase shift means for correcting the phase of the code-modulated signal with respect to the reproduced carrier signal based on the result of the cumulative addition.

Further, the receiver is characterized by further comprising a hypothesis changing means for changing a coding modulation scheme assumed for performing the cumulative addition based on a result of the cumulative addition.

Further, the receiver is characterized by further comprising means for evaluating a signal transmission state between the transmitter and the receiver based on a result of the cumulative addition.

Further, the transmitter is further provided with means for selecting one of the trellis coded modulation systems from the plurality of trellis coded modulation systems based on the control signal. .

[0041]

[Operation] The minimum state metric is calculated on the receiver side,
The data transmission error rate on the transmission path is evaluated by monitoring the increase amount of this minimum state metric. Further, the information on the data transmission error rate is transmitted from the receiver side to the transmitter side, and the transmitter side changes the transmission output level and the coding modulation method based on the information on the data transmission error rate.

[0042]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the communication method and system of the present invention will be described below. FIG. 1 is a diagram showing a configuration of a communication method and a communication system to which the method of the present invention in the first embodiment is applied. FIG. 2 is a diagram showing the configuration of the Viterbi decoding circuit 41 of the receiver 3 of the present invention in the first embodiment. The configurations of the transmitter 1 and the receiver 3 will be described below with reference to FIGS. 1 and 2.

The communication system shown in FIG. 1 comprises a transmitter 1, a receiver 3 and transmission lines 50 and 51. The transmitter 1 encodes the data input by the trellis coded modulation method and sends it to the receiver 3 via the transmission line 50. Further, the transmission output level is changed based on the control information input from the receiver 3 via the transmission path 51. Transmitter 1
Is an encoding circuit 10 that encodes input data by a trellis encoding method, and I output from the encoding circuit 10.
A quadrature modulation circuit 20 which quadrature modulates a carrier signal with a signal (cos axis signal) and a Q signal (sin axis signal) and sends it out to a transmission line 50.

In FIG. 1, the convolutional coding circuit 11
Performs parallel convolutional coding corresponding to the coding scheme of the transmitter 1, for example, coded 8PSK. Signal allocation circuit 12
Is assigned to the parallel coded output signal of the convolutional coding circuit 11 and input to the quadrature modulation circuit 20 which performs quadrature modulation as I and Q signals which are orthogonal to each other. Here, the convolutional coding in the convolutional encoder 11 will be described by taking the coding 8PSK as an example. FIG. 3 shows the encoded 8P
It is a figure which shows the Euclidean distance between the signals of SK. Figure 3
As shown in, the Euclidean distance Δ ₀ = Δ ₂ sin (π / 8) ≈0.3
827 Δ ₂ Euclidean distance Δ ₁ = Δ ₂ / √2 ≈0.7
071 Δ ₂ Euclidean distance Δ ₀ = Δ ₂ cos (π / 8) ≈0.9
The relationship is 839Δ ₂ .

FIG. 4 is a diagram showing an example of the trellis representation of the convolutional encoder 11 when the constraint length is 3 and the number of registers ν is 2. Under this condition, the convolutional encoder 11 outputs a 3-bit output signal (y ₂ , y ₁ , y ₀ ) for a 2-bit input signal (x ₁ , x ₀ ). This output signal (y
₂ , y ₁ , y ₀ ) correspond to the signals S _{0 to} S ₇ in FIG.

In FIG. 4, register states (0, 0,
0) to the third time slot again (0,0,0)
Rejoining path (0-0-0), and path (6-7
-6) Find the inter-signal distance for the two paths. Here, as to the Euclidean distance of the path (6-7-6), referring to FIG. 4, one signal point is S ₀ and the other signal point is S ₆ in the first branch. The distance is Δ ₁ .

Similarly, the Euclidean distance of the second branch is Δ ₀ , and the Euclidean distance of the second branch is Δ ₁ . Therefore, the square of the Euclidean distance of the path (6-7-6) is d ₀ ² = Δ ₂ (6−√2) / 2.

In addition to this path (6-7-6), the path from the register state (0,0,0) to the register state (0,0,0) after 3 time slots is the path (0-0-0). ),
There are a path (6-5-2), a path (4-1-2), and a path (4-3-6), and the square of the Euclidean distance of each of these paths is larger than d ₀ ² . Coding is performed by allocating to each signal point in FIG. 3 so that the minimum value of the square of the minimum Euclidean distance obtained in this way becomes maximum.

The modulation circuit 23 quadrature-modulates the carrier signal with the I signal and the Q signal input from the encoding circuit 10 and inputs it to the output amplification circuit 24. Control information receiving circuit 2
1 receives a control information signal input from the receiver 3 via the transmission path 51 and inputs it to the output level control circuit 22.

The output level control circuit 22 controls the output power (level) of the output amplifier circuit 24 based on the control information from the control information receiving circuit 21. The output amplifier circuit 24 is
The output level is set under the control of the output level control circuit 22, the modulated output signal input from the modulation circuit 23 is amplified, and the amplified signal is sent to the transmission line 50.

The configuration of the receiver 3 will be described below.
The receiver 3 includes a demodulation circuit 30 and a Viterbi decoding circuit 40, and decodes the received signal from the transmitter 1 by the Viterbi decoding method. Also, the data error rate on the transmission line 50 is evaluated by monitoring the increase amount of the minimum state metric, and the information on the data error rate is transmitted to the transmitter 1 via the transmission line 51.

The demodulation circuit 30 quadrature-detects the received signal from the transmitter 1 and demodulates the I signal and the Q signal. The Viterbi decoder 41 decodes data from the I signal and Q signal input from the demodulation circuit 30 by the Viterbi decoding method.
The configuration of this Viterbi decoder 41 will be described later.

The reception state monitoring circuit 42 is used by the Viterbi decoder 4
The data transmission error rate on the transmission line 50 is evaluated based on the path metric calculated in 1, and the information on the data transmission error rate is input to the control information transmission circuit 43. The control information transmission circuit 43 sends the data transmission error rate information input from the reception state monitoring circuit 42 to the transmitter 1 via the transmission line 51.

The transmission line 50 transmits a signal encoded by the trellis coded modulation method in the transmitter 1. The transmission path 51 transmits the control signal sent from the receiver 3 to the transmitter 1.

The configuration of the Viterbi decoder 41 will be described below with reference to FIG. Branch metric generation circuit 411
Calculates the square of the Euclidean distance (branch metric) for the coded modulation method (coded 8PSK in this embodiment) based on the input I and Q signals.

The ACS circuit 412 performs maximum likelihood path calculation based on the branch metric calculated by the branch metric generation circuit 411, selects the branch with the highest likelihood and controls the path memory 413.

The path memory 413 stores the path selected under the control of the ACS circuit 412. The P / S conversion circuit 414 converts the parallel format decoded data output from the path memory 413 into serial format data and outputs the serial format data as decoded data.

The operation of the transmitter 1 and the receiver 3 will be described below. In the trellis coded modulation method used in the transmitter 1 and the receiver 3, the square of the Euclidean distance (branch metric) between the received signal and each signal point is obtained on the receiving side, and the Viterbi decoding circuit is based on this value. To operate. Therefore, the sequence with the lowest noise power is determined as the data on the transmitting side. Value (path metric) of this series (maximum likelihood path)
Based on the above, the data error rate on the transmission path at that time can be appropriately evaluated.

The convolutional coding circuit 11 performs parallel convolutional coding corresponding to the coded 8PSK on the data input, and inputs the coded data to the signal allocation circuit 12. The signal allocation circuit 12 allocates signals to the encoded data and inputs them to the quadrature modulation circuit 20 as I signals and Q signals. In the quadrature modulation circuit 20, the carrier signal is quadrature-modulated by the I signal and the Q signal, and the transmission line 5
It is sent to the receiver 3 via 0. On the transmission line 50, this signal causes a data transmission error due to the influence of noise or the like.

The demodulation circuit 30 uses the transmission line 50 as described above.
Received a signal with a data transmission error in and quadrature detected,
Demodulate the I and Q signals. The branch metric generation circuit 411 calculates the square of the Euclidean distance (branch metric) corresponding to the coded 8PSK method for the demodulated I signal and Q signal.

The ACS circuit 412 performs maximum likelihood path calculation based on this branch metric, selects the branch with the highest likelihood, controls the path memory 413, and determines the state metric already stored in this branch metric. The values are added, the minimum value of the state metric is subtracted from the added value, and the normalized value is set as a new state metric.

On the other hand, the minimum value of the state metric is also input to the reception state monitoring circuit 42. Reception status monitoring circuit 4
2 evaluates the data transmission error rate on the transmission path 50 by cumulatively adding the normalized minimum state metric a predetermined number of times and determining the cumulative addition value. This normalized minimum cumulative value of the state metric is the data error rate on the transmission line 50 when the receiver 3 is normally decoding the data without phase shift of the reproduced carrier wave. The cumulative addition value increases as the data error rate increases.

That is, when the above-mentioned cumulative addition value of the normalized minimum state metric changes with time, the data transmission error rate on the transmission line 50 also changes with time. Therefore, the data transmission error rate on the transmission line 50 can be evaluated by monitoring the cumulative value of the normalized minimum state metric. That is, when this cumulative addition value increases, the amount of noise energy received by the signal on the transmission path 50 increases, and when this cumulative addition value decreases, the amount of noise energy received by the signal on the transmission path 50 decreases. It can be evaluated as done.

The reception state monitoring circuit 42 generates information on the data transmission error rate based on the normalized cumulative addition value of the state metric, and transmits this information via the control information transmission circuit 43 and the transmission line 51. Transmitter 1 as control information
To transmit. Here, since the amount of control information on the transmission line 51 is much smaller than the information on the transmission line 50, the data transmission rate of the transmission line 51 can be made much lower than the data transmission rate of the transmission line 50. is there. Therefore, transmission line 5
The data transmission error rate of the control information on the transmission line 51 can be easily and sufficiently kept low as compared with the signal on 0.

This control information is received by the control information receiving circuit 21 of the transmitter 1 and input to the output level control circuit 22. The output level control circuit 22 controls the output amplifier circuit 24 so as to output a transmission output corresponding to the data transmission error rate on the transmission line 50 indicated by the control information.

The value of the output power of the output amplifier circuit 24 may be determined by, for example, a ROM table showing the correspondence between the data transmission error rate and the output signal or an appropriate calculation of the data transmission error rate. By providing such a control loop between the transmitter 1 and the receiver 3, it is possible to perform energy-efficient transmission without using unnecessary transmission power.

It is not always necessary to use two transmission lines for transmission of encoded data and transmission of control information between the transmitter 1 and the receiver 3. For example, the control information is multiplexed with the encoded data for transmission. However, in order to improve the reliability of the control information, the transmitter 1 may be configured to control the transmission output only when the same control information is continuously received a predetermined number of times.
In addition, the transmission method of the control signal and the encoded data may not be the same. For example, the control information may be transmitted by FSK modulation.

The transmitter 1 will be described below with reference to the flowchart.
The operation of the receiver 3 will be described. FIG. 5 is a flowchart showing the processing of the transmitter 1 in the first embodiment. In FIG. 5, in step 00 (S00),
The output level control circuit 22 sets the initial output level of the transmission signal in the output amplification circuit 24. Step 01 (S01)
In, the encoding circuit 10 encodes the data input, and the quadrature modulation circuit 20 outputs the encoded data to the receiver 3 at the initial output level.

In step 02 (S02), the output level control circuit 22 determines whether or not the control information is received from the transmitter 1 via the control information receiving circuit 21. If received, the process of S03 is performed. If not received, S02
Continue processing.

FIG. 6 is a diagram showing the processing of the receiver 3 in the first embodiment. In FIG. 6, step 10 (S
In 10), the branch metric generation circuit 411 calculates the square of Euclidean distance (branch metric) for the received signal. In step 11 (S11), the ACS circuit 412 calculates the path metric which is the minimum state metric normalized based on the branch metric. In step 12 (S12), the reception state monitoring circuit 42 cumulatively adds the path metric which is the minimum state metric normalized based on the calculation result of the ACS circuit 412.

In step 13 (S13), the reception state monitoring circuit 42 determines whether or not the specified number of cumulative additions has been performed. If the cumulative addition is performed the specified number of times, the process proceeds to S14. If the cumulative additions have not been performed the specified number of times, the process proceeds to S10.

In step 14 (S14), it is determined whether or not the cumulative addition value is less than or equal to a fixed reference value. If it is equal to or less than a certain standard value, it is determined that the data decoding is normally performed, the cumulative addition value is reset (S15), the cumulative addition value is judged (S18), and the cumulative addition value is dealt with. A control signal is sent to the transmitter 1 (S19). If it is equal to or more than a certain reference value, it is determined that the data decoding is not normally performed, the cumulative addition value is reset (S16), and the phase shift of the received signal is performed for phase matching of the reproduced carrier signal. (S17).

In the judgment in S14, when the cumulative addition value is equal to or larger than the predetermined reference value, it is judged that the reproduction carrier signal and the carrier signal of the transmitter 1 are out of phase and the data is not normally decoded. Because it is possible. in this case,
The Viterbi decoder 41 is preceded by means for phase shifting the input signal under the control of the reception state monitoring circuit 42. However, this means is not an essential component in the first embodiment.

A second embodiment of the communication method and method of the present invention will be described below. FIG. 7 is a diagram showing the configuration of a communication method of the present invention and a communication system to which the method is applied in the second embodiment.

In the transmitter 1 of the second embodiment, the output power is kept constant and its control is not performed, and the coding / modulation method is changed according to the data transmission error rate on the transmission line 50, so that the time Among the data transmission rates possible in the state of the transmission line 50, the data transmission is performed at the highest data transmission rate.

In FIG. 7, the coding circuit 15 has a plurality of different coding and modulation schemes, for example, coding 8PSK, coding 16QAM, coding 32QAM, and coding 64Q.
An AM circuit and a signal allocating circuit corresponding to these coding circuits are included, the data input is coded by a coding method under the control of the coding control circuit 16, and further signal allocation is performed to modulate as an I signal and a Q signal. Input to the circuit 23. The coding and modulation schemes supported by the transmitter 1 and the receiver 3 of the present embodiment are not limited to the above four types, and may be configured to support only an arbitrary combination thereof.

FIG. 8 is a diagram showing the configuration of the encoding circuit 15. The shift register 151 and the register 152 are
A P / S conversion circuit is configured. This shift register 151
The register 152 converts the serial format data input into the parallel format.

The convolutional coding circuit 153, under the control of the reception state monitoring circuit 42, performs coding at a coding rate of 3/4 in the case of performing coding 16QAM, for example.
When QAM is performed, the coding rate is 5/6. R
The OM 159 stores a signal allocation table and stores output information of the convolutional coding circuit 153, a signal from the redundant bit generation unit (not shown), and a signal from the reception state monitoring circuit 42 that specifies the coding method. The signals are input to the ROM 159 and signal allocation according to the modulation method is performed.

That is, for example, in the case of coded 16QAM, a 4-bit signal including redundant bits is assigned, and in the case of coded 64QAM, similarly a 6-bit signal including redundant bits is assigned.

The demodulation circuit 30 demodulates data corresponding to coded 8PSK, coded 16QAM, coded 32QAM, and coded 64QAM under the control of the reception state monitoring circuit 42. The Viterbi decoder 41 phase-shifts the I signal and the Q signal input under the control of the reception state monitoring circuit 42 to perform phase compensation with the reproduced carrier signal, and
Coded 8PSK, Coded 16QAM, Coded 32QA
Data corresponding to M and encoded 64QAM is decoded.

Viterbi decoder 41 in the second embodiment
Is preceded by a phase correction circuit 415 in the branch metric generation circuit 411, and is controlled by the reception state monitoring circuit 42 in 90 ° units (encoding 16, encoding 32, and encoding 6).
4QAM) or 45 ° unit (encoded 8PSK)
In the case of), the phase is corrected.

The reception state monitoring circuit 42 evaluates the data transmission error rate of the transmission line 50 as in the first embodiment, and the control information transmission circuit 43 uses the information of the data transmission error rate as control information. And the transmitter 1 via the transmission line 51.
Send to. Other parts of the transmitter 1 and the receiver 3 shown in FIG. 7 are the same as the parts with the same reference numerals as the parts of the transmitter 1 and the receiver 3 shown in FIGS. 1 and 2.

The operation of the transmitter 1 and the receiver 3 of the second embodiment will be described below. First, the transmitter 15 of the transmitter 1
Is, for example, the encoding 64 preset as the initial condition.
Data is encoded by the QAM method, and the encoded data is sent to the transmitter 1 via the quadrature modulation circuit 20.

The control information transmission circuit 43 sets the demodulation circuit 30 and the Viterbi decoder 41 so as to demodulate and decode the data corresponding to the encoded 64QAM system set as the initial condition in advance, and the receiver 3 The signal from the transmitter 1 is received. Branch metric generation circuit 411
Calculates a branch metric for received data.

The ACS circuit 412 performs maximum likelihood path calculation based on this branch metric, selects the branch with the highest likelihood, and controls the path memory 413. on the other hand,
The reception state monitoring circuit 42 cumulatively adds the normalized minimum state metric in the ACS circuit 412 a predetermined number of times, and when the cumulative addition value is equal to or larger than a predetermined reference value, the received signal is not normally decoded. It is determined that the reproduction carrier signal is not performed and the phase correction circuit 415 is controlled to correct the phase of the reproduced carrier signal and the input I signal and Q signal.

When the cumulative addition value does not fall below a certain level, the reception state monitoring circuit 42 performs the above encoding 16 to encoding 64Q.
In the case of AM, the phase correction is performed in units of 90 °, so four times corresponding to one coded modulation method, and coded 8P.
In the case of SK, the phase correction is performed in units of 45 °, so that the phase correction is performed eight times corresponding to one coding modulation method.

Further, if the cumulative addition value does not fall below the predetermined reference value even after performing the phase correction for the number of times corresponding to each of the coded modulation systems, the demodulation circuit 30 and the Viterbi decoding are performed assuming the next coded modulation system. The device 41 is set and the data corresponding to this coded modulation method is decoded. This phase correction and the change of the assumption of the coded modulation method are continued until the cumulative addition value becomes equal to or less than the reference value set for each coded modulation method.

Further, when the cumulative addition value becomes equal to or less than the standard value, the reception state monitoring circuit 42 evaluates the data transmission error rate of the transmission line 50 based on the cumulative addition value and controls the control information transmission circuit as control information. It is sent to the transmitter 1 via 43 and the transmission path 51.

The control information receiving circuit 21 receives this control signal and inputs it to the encoding circuit 15. Encoding circuit 15
Based on the data transmission error rate of the control signal, the coding modulation method corresponding to the state of the transmission line 50 is 8PSK,
16QAM, 32QAM, and 64QAM are selected, the encoding circuit 15 is set, the input data is encoded by the selected encoding modulation method, and the encoded data is sent to the receiver 3.

That is, when the state of the transmission line 50 is poor and the cumulative addition value becomes large, the coding modulation system having a low transmission rate and strong against disturbance such as noise is selected, and conversely, the transmission line 50 is selected.
When the state is good and the cumulative addition value becomes small, a coding modulation system with a low transmission rate and a high transmission efficiency is selected, and the optimum coding modulation system is always used corresponding to the state of the transmission path 50. Performs data transmission.

FIG. 9 is a flowchart showing the processing of the transmitter 1 in the second embodiment. In FIG. 9, in step 20 (S20), the encoding circuit 15 sets the initial encoding method in the transmitter 15. Step 21 (S
In 21), the transmitter 15 performs encoding according to the encoding method set for data input.

In step 22 (S22), the coding circuit 15 determines whether or not the control signal from the transmitter 1 is received. When received, the coding and modulation method is changed. If not received, the process proceeds to S21.

FIG. 10 shows the receiver 3 in the second embodiment.
It is a flowchart which shows the process of. In FIG.
In step 30 (S30), the reception state monitoring circuit 4
2 assumes each of the initial coded modulation schemes, and makes settings corresponding to the coded modulation schemes in each part of the receiver 3.

In step 31 (S31), the square of the Euclidean distance of the received signal and the assumed coded modulation method is calculated. In step 32 (S32), ACS
The circuit 412 calculates the minimum normalized state metric.

In step 33 (S33), the reception state monitoring circuit 42 cumulatively adds this path metric. In step 34 (S34), the reception state monitoring circuit 42
Determines whether or not the specified number of cumulative additions has been performed. When the cumulative addition is performed the specified number of times, the process proceeds to S35. If the cumulative addition has not been performed the specified number of times, the process proceeds to S31.

In step 35 (S35), the reception state monitoring circuit 42 determines whether the cumulative addition value is less than or equal to the reference value. If it is less than the reference value, the process proceeds to S39. If it is not less than the standard value, the cumulative addition value is reset (S3
6) Judge the cumulative addition value and send a control signal (S3).
8).

The receiver 3 may also determine the coding and modulation scheme in the transmitter 1 and transmit it to the transmitter 1 as a control signal. Further, in this case, the setting of the coded modulation method designated for the transmitter 1 may be performed for each part of the receiver 3.

In step 39 (S39), the reception state monitoring circuit 42 resets the cumulative addition value. Step 4
At 0 (S40), it is determined whether all the phase states of the assumed coded modulation method have been checked. When all are checked, the following coding and modulation scheme is assumed and the setting is performed in each part of the receiver 3. When all are not checked, the phase correction circuit 415 is caused to shift the phase of the input signal.

In the flowchart of FIG. 10, S35
The determination is made by using the cumulative addition value of the path metric and whether or not the currently assumed coding and modulation scheme and the received signal are synchronized. In other words, the cumulative addition value is equal to or less than the reference value when synchronized. On the other hand, when they are not synchronized, the cumulative addition value becomes a value larger than the reference value. This is used to determine the synchronization.

By the above processing, the received signal can be matched with the assumed coded modulation method, and the phase of the reproduced carrier signal can be synchronized with the phase of the carrier signal on the transmission side. Further, by providing such a control loop between the transmitting side and the receiving side, it is possible to select a modulation method having high transmission efficiency according to the state of the transmission line 50.

The communication method of the second embodiment and a modification of the method will be described below. In the communication method and system thereof shown in the second embodiment, when the state of the transmission line 50 changes every moment, the transmission coding modulation system changes according to the state of this transmission line. In such a case, synchronization must be re-acquired every time the modulation scheme changes on the receiving side, and it may be inconvenient because actual information cannot be transmitted until the synchronization is established. In the case of a transmission line in which such a situation is expected, the modulation method may be determined in advance only when the communication between the transmitting side and the receiving side is established in anticipation of fluctuations in the transmission line.

FIG. 11 is a flowchart showing a modified example of the processing of the receiver 3 in such a case. That is, in the processing of the receiver 3 shown in FIG. 10, the modulation method may always change depending on the state of the transmission line 50 after the communication is started. However, depending on the application, it may not be possible to take time for resynchronization accompanying a change in the coding and modulation scheme.

Therefore, when a flag is prepared and the synchronization state is detected by the determination condition 2, it is determined whether it is the first synchronization supplement or not.
If it is the first synchronization acquisition, the control signal for controlling the modulation method on the transmission side is transmitted by determining the magnitude of the accumulated value of the path metric. If it is not the first synchronization acquisition, the cumulative value of the path metric is not analyzed and the operation of controlling the transmission modulation method is not performed, but the cumulative value is reset and the square of the Euclidean distance to each signal point is calculated. Return to processing.

By introducing the determination processing of this flag, the level of noise, distortion or interference of the transmission line is measured as a training period from the start of the receiving operation to the first establishment of synchronization, and only at this time. The result is fed back to the transmission side to control the transmission modulation method.

In FIG. 11, step 40 (S40)
In, the reception state monitoring circuit 42 assumes the initial coded modulation method. In step 41 (S41), the reception state monitoring circuit 42 clears the flag. Step 42
In (S42), the branch metric generation circuit 41
1 calculates the square of the Euclidean distance between the assumed coded modulation method and the received signal. In step 43 (S43), the ACS circuit 412 calculates the normalized minimum state metric as a path metric. In step 44 (S44), the reception state monitoring circuit 42 cumulatively adds the path metrics.

In step 45 (S45), the reception state monitoring circuit 42 determines whether or not the cumulative addition has been performed the specified number of times. When the cumulative addition is performed the specified number of times, the process proceeds to S46. If the cumulative addition of the specified number of times has not been performed, the process proceeds to S47. In step 46 (S46), the reception state monitoring circuit 42 determines whether the cumulative addition value has come and is 1 or less. If it is less than the reference value, the process proceeds to S47. If it is not less than the reference value, the process proceeds to S49.

In step 47 (S47), the reception state monitoring circuit 42 checks the flag. If the flag is 1, the process proceeds to S48. If the flag is 0, the flag is set to 1 (S53) and the cumulative addition value is determined (S53).
54), and sends the result to the transmitter 1 (S55). Here, similarly to the above, the receiver 3 side may be configured to specify the coding and modulation scheme of the transmitter 1.

In step 48 (S48), the reception state monitoring circuit 42 resets the cumulative addition value. Step 4
In 9 (S49), the reception state monitoring circuit 42 resets the cumulative addition value. In step 50 (S50),
The reception state monitoring circuit 42 determines whether or not the determination in S46 has been performed for all the phases corresponding to the coded modulation method. When all the phases are determined, the phase correction circuit 415 shifts the phases (S51). If all the phases have not been determined, the following coding and modulation scheme is assumed, and each unit of the receiver 3 is set.

The change of the transmission output described in the first embodiment and the change of the coding and modulation method described in the second embodiment can be used in an appropriate combination. In addition to the above-described embodiments, the communication method and method of the present invention can have various configurations, for example, as described as modifications in the embodiments. The embodiments described above are merely examples.

[0110]

As described above, according to the present invention, it is possible to appropriately evaluate the state of the transmission line, that is, the data transmission error rate. Therefore, the transmission level of the transmission line can be changed corresponding to the data transmission error rate of the transmission line. It is possible to provide a communication method and a method capable of adaptively changing the control or coding / modulation method and always performing efficient transmission corresponding to the state of the transmission path.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a communication method and a communication system to which the method of the present invention is applied in a first embodiment.

FIG. 2 is a diagram showing a configuration of a Viterbi decoding circuit of the receiver of the present invention in the first embodiment.

FIG. 3 is a diagram showing a Euclidean distance between 8PSK signals.

FIG. 4 is a diagram showing an example of a trellis representation of a convolutional encoder when the constraint length is 3 and the number of registers ν is 2.

FIG. 5 is a flowchart showing the processing of the transmitter in the first embodiment.

FIG. 6 is a diagram showing processing of a receiver in the first embodiment.

FIG. 7 is a diagram showing a configuration of a communication method of the present invention and a communication system to which the method is applied in a second embodiment.

FIG. 8 is a diagram showing a configuration of an encoding circuit.

FIG. 9 is a flowchart showing the processing of the transmitter in the second embodiment.

FIG. 10 is a flowchart showing the processing of the receiver in the second embodiment.

FIG. 11 is a diagram showing a flow chart of a modified example of the processing of the receiver in the second embodiment.

FIG. 12 is a diagram showing a configuration of a general conventional transmitter that transmits data by a trellis coded modulation method.

FIG. 13 is a diagram showing a configuration of a conventional receiver that receives data encoded by the trellis coded modulation method.

FIG. 14 is a diagram showing a configuration of a conventional Viterbi decoding circuit of a conventional receiver.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Transmitter 10 ... Encoding circuit 11 ... Convolutional encoding circuit 12 ... Signal allocation circuit 15 ... Encoding circuit 151 ... Shift register 152 ... Register 153 ... Convolutional encoding circuit 159 ... ROM 16 ... Control circuit 20 ... Quadrature modulation circuit 21 ... Control information receiving circuit 22 ... Output level control circuit 23 ... Modulation circuit 24 ... Output amplification Circuit 3 ... Receiver 30 ... Demodulation circuit 40 ... Viterbi decoding circuit 41 ... Viterbi decoder 411 ... Branch metric generation circuit 412 ... ACS circuit 413 ... Path memory 414 ... .P / S conversion circuit 415 ... phase correction circuit 42 ... reception state monitoring circuit 43 ... control information transmission circuit

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display location H04L 27/34 27/18 A 9297-5K

Claims (16)

[Claims] 1. A signal code-modulated by a trellis code-modulation method is transmitted, the code-modulated signal is received, a minimum state metric is cumulatively added a predetermined number of times, and based on a result of the cumulative addition. Communication method for setting the transmission power of the code-modulated signal. 2. A coded modulation method is selected from among a plurality of trellis coded modulation methods to code-modulate a signal,
This code-modulated signal is transmitted, the code-modulated signal is received assuming a code-modulation method, the minimum state metric is cumulatively added a predetermined number of times, and the minimum state metric is cumulatively added based on a result of the cumulative addition. A communication method for selecting an encoding and modulation method and / or setting a transmission power, or one of them. 3. The communication method according to claim 1, further comprising correcting the phase of the code-modulated signal based on the result of the cumulative addition. 4. The communication method according to claim 2, wherein the assumption of the coded modulation method is further changed based on the result of the cumulative addition. 5. The selection of the coded modulation method and / or the assumption of the coded modulation method is performed at least once from the start to the end of reception of the coded and modulated signal. It is carried out only.
4. The communication method and method according to any one of 4 above. 6. The plurality of trellis coded modulation schemes are at least 8PSK, 16QAM, 32QAM, and 6.
The communication method according to any one of claims 1 to 5, comprising 4QAM or any combination thereof. 7. When the result of the cumulative addition increases, a coded modulation system having a lower transmission rate than the coded modulation system used at that time is selected from among the plurality of trellis coded modulation systems. The communication method and method according to any one of claims 2 to 6, wherein 8. When the result of the cumulative addition decreases, a coded modulation system having a higher transmission rate than the coded modulation system used at that time is selected from among the plurality of trellis coded modulation systems. The communication method and method according to any one of claims 2 to 7, characterized in that. 9. A signal which is code-modulated by a trellis code-modulation system is received, a minimum state metric is cumulatively added a predetermined number of times, and a state of a transmission line is evaluated based on the cumulative addition result. A communication method for performing transmission and / or reception, or controlling one of these based on the result of. 10. A transmitter and a receiver, the transmitter comprising a control signal receiving means for receiving a control signal from the receiver, and a transmission power for setting transmission power based on the control signal. The receiver includes a setting means, a code modulation means for code-modulating data by trellis code modulation, and a signal sending means for sending the code-modulated signal to the receiver at the transmission power. Is a cumulative addition device that receives the code-modulated signal and cumulatively adds a minimum state metric a predetermined number of times, and a control that generates the control signal based on the result of the cumulative addition and sends the control signal to the transmitter. A communication system having a signal transmitting means. 11. A transmitter, the transmitter comprising a control signal receiving means for receiving a control signal from the receiver, a transmission power setting means for setting transmission power based on the control signal, and a trellis code. A communication system comprising: a code modulation means for code-modulating data by code modulation, and a signal sending means for sending the code-modulated signal to the receiver at the transmission power. 12. A receiver, comprising: a receiver, which receives the code-modulated signal and cumulatively adds a minimum state metric a predetermined number of times; and a cumulative addition device based on a result of the cumulative addition. And a control signal transmitting unit for generating the control signal and transmitting the control signal to a transmitter. 13. The receiver according to claim 10, further comprising phase shifting means for correcting a phase of the code-modulated signal with respect to a reproduced carrier signal based on a result of the cumulative addition. Item 12. The communication method according to Item 12. 14. The receiver according to claim 10, further comprising hypothesis changing means for changing a coding modulation scheme assumed for performing the cumulative addition based on a result of the cumulative addition. The communication system according to claim 11 or 13. 15. The receiver according to claim 10, further comprising means for evaluating a signal transmission state between the transmitter and the receiver based on a result of the cumulative addition. The communication method according to any one of 1. 16. The transmitter further comprises means for selecting one coded modulation system used for coded modulation of a signal from a plurality of trellis coded modulation systems based on the control signal. Claim 10 or Claim 11
Communication method described in.