JPH11252031A - Receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately estimate a transmission data sequence without lowering the efficiency of transmitting data. SOLUTION: A transmitter 100 transmits transmission signals for which plural data symbol sequences for indicating the respective plural transmission data sequences are multiplexed and a receiver 10A1 receives the transmission signals. An orthogonal transformation part 12A1 transforms the received transmission signals to plural signal sequences for respectively indicating the prescribed number of the transmission data sequences among the plural transmission data sequences shown by the transmission signals. A transmission data sequence estimation part 14A1 estimates the transmission data sequence shown by the transmission signals based on the respective plural signal sequences and respective predicted signal sequences predicted for the respective signal sequences.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiver, and more particularly, to a receiver for receiving a transmission signal obtained by multiplexing a plurality of data symbol sequences representing a plurality of transmission data sequences, and representing the received transmission signal. And a receiver for estimating a plurality of transmission data sequences to be performed.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 38, a plurality of data symbol sequences respectively representing a plurality of transmission data sequences are multiplexed using an orthogonal transform unit 116 to form a transmission signal. Each of the multiplexed signal sequences is transmitted using a transmitter 100 for transmission and an orthogonal transform unit 16 that receives the transmission signal and performs the orthogonal transform reverse to the orthogonal transform performed by the transmitter 100. Are separated into respective signal sequences before multiplexing so as not to interfere with each other, and the separated signal sequences are subjected to code (phase-amplitude) determination by each determiner 84, and the parallel. A communication system including a receiver 10 that outputs decoded data through a serial conversion circuit 86 has been proposed.

[0003] Here, a communication system in which a discrete inverse Fourier transform is performed by an orthogonal transform on a transmitting side and a discrete Fourier transform is performed by an orthogonal transform on a receiving side is known as an orthogonal frequency division multiplexing system which is a kind of a multicarrier modulation system. Has been decided for digital terrestrial television broadcasting (John A.
C. Bingham: "Multicarrier Modulation for Data Tra
nsmission: An Idea Whose Time Has Come, "IEEE Comm
unications Magazine, pp.5-14, May 1990. Aiichiro Tsutake: “OFDM modulation and demodulation method,” IEICE, vo.
l.79, No.8, pp.831-834, 1996).

[0004] Further, there has been proposed a communication system in which a discrete inverse wavelet transform or a wavelet packet is synthesized by orthogonal transform on a transmitting side and a discrete wavelet transform or division by wavelet packet is used for orthogonal transform on a receiving side (GWWornell, AVOppenheim). :
"Wavelet-Based Representation for a Class of Self
-Similar Signals with Application to Fractal Modul
ation, "IEEE Trans.Information Theory, vol.38, pp.
785-800, 1992 March. MATzannes, MCTzannes, J. Proakis, PNHeller: "
DMT systems, DWMT Systems and Digital Filter Bank
s, "IEEE Proceedings of ICC'94. ARLindsey, et al .:" Wavelet Packet Modulations:
A generalized method for orthogonally multiplexed c
ommunications, "IEEE Proceedings of SSST'95, 1995
See March. Et al.).

FIG. 39 shows a configuration example of the transmitter 100 and the receiver 10 in the case of multiplexing a signal sequence using division and synthesis by wavelet packets as orthogonal transform. FIG.
9 shows an example in which a division pattern for equally dividing the band into four is used as the division pattern in the time / frequency domain of the wavelet packet. The orthogonal transform unit 116 of the transmitter 100 combines the four signal sequences to create a transmission signal. In the receiver 10, after receiving the transmission signal, the orthogonal transform unit 16 divides the signal by the same wavelet packet division pattern as the orthogonal transform of the transmitter 100 to obtain a signal sequence before multiplexing.

[0006] Here, the orthogonal transform unit for performing division and synthesis using wavelet packets can be constituted by a plurality of band combining filters 120 on the transmitter 100 side and by a band dividing filter 20 on the receiver 10 side.

Here, as shown in FIG. 40, the band synthesis filter 120 on the transmitter 100 side includes a sampling circuit 1
In 20A1 and 120A2, the sampling rate of the signal for allocating the frequency band to the high frequency side and the signal for allocating to the low frequency side are double-sampled, and the signals sampled by the sampling circuits 120A1 and 120A2 are converted into high-frequency filters Low-pass filter 120B2
Then, the signal is converted into a signal in a high-frequency band and a signal in a low-frequency band, respectively.
The signal passing through B2 is synthesized by the synthesizer 120C. High-pass filter 120B1 and low-pass filter 120B
The filter characteristic of No. 2 is appropriately set according to the basis function of the wavelet to be used. For example, in the case of Dobshizu wavelet (construction by 4-tap FIR filter),

[0008]

(Equation 1)

## EQU1 ## On the other hand, as shown in FIG. 41, the band synthesis filter 20 of the receiver 10 passes the input signal through the high-pass filter 20A1 and the low-pass filter 20A2, and halves the sampling rate by the sampling circuits 20B1 and 20B2. Down-sampling to divide the signal into high-frequency signals and low-frequency signals. The filter characteristics of the high-pass filter 20A1 and the low-pass filter 20A2 are appropriately set according to the wavelet basis function used. For example, in the case of Dobshizu wavelet (construction by 4-tap FIR filter),

[0010]

(Equation 2)

## EQU1 ## By the way, the configuration of the orthogonal transform unit when the orthogonal transform unit 16 of the receiver 10 performs division by wavelet packets is shown in FIGS.
It is shown in (C). As shown in FIG. 42A, if a configuration is adopted in which a band division filter is sequentially connected to the lower band side output of the band division filter, a normal wavelet transform is performed. In a normal wavelet transform, the input signal is as shown in FIG.
It is divided into division patterns as shown in the right area of FIG. This division pattern indicates that the signal is divided into a signal having a wider frequency bandwidth and a shorter time interval on the higher frequency side, and a signal having a smaller frequency bandwidth and a longer time interval on the lower frequency side. Further, as the number of connection stages of the band division filter is increased, the lower frequency band is finely divided.
Since the sampling rates are sequentially converted, one signal is output for each square indicating the divided area on the time axis. The division by the wavelet packet is obtained by connecting band division filters in an arbitrary combination. As shown in FIGS. 42B and 42C, various division patterns can be realized depending on the connection method. . A great advantage of the wavelet packet is that the division pattern in the time / frequency domain can be set according to the purpose.

In the case of the inverse wavelet transform, band synthesis filters are sequentially connected from the lower band side. In the synthesis using wavelet packets, the band synthesis filters are connected in the order corresponding to the connection of the band division filters on the receiver side.

Other typical orthogonal transforms include a discrete cosine transform, a discrete sine transform, a Walsh-Hadamard transform, a Karhunen-Loeve transform, and the like.

By the way, in the above communication system, there is a high possibility that noise, distortion, and the like are mixed in a transmission signal in a communication channel, and a transmission data sequence is erroneously transmitted. Therefore, the decoding error rate is high. Therefore, it is necessary to suppress the influence of errors occurring in the communication path and improve the reliability of the use of the communication path. Therefore, conventionally, error correction coding is performed on transmission data (report) in advance, and the receiver performs decoding by decoding processing corresponding to error correction coding. For example, FIG.
As shown in (A), the convolutional encoder 200 on the transmitter side
Then, as shown in FIG. 43B, the maximum likelihood sequence estimation unit 300 on the receiver side performs maximum likelihood sequence estimation, which is a type of decoding method of convolutional codes, as shown in FIG. Note that the convolutional code divides a plurality of transmission data sequences into a plurality of transmission data sequence blocks, and performs coding of the transmission data sequence of each block independently of each block separately. Is a method that depends on the transmission data sequence. It is known that the maximum likelihood sequence estimation is a decoding method that can minimize the error rate when information on the transmission side is random. In maximum likelihood sequence estimation, the Viterbi algorithm is an algorithm that efficiently estimates the most likely sequence ("Information Theory," Shokodo
(1987), "Code theory," IEICE (1990)). In addition, the maximum posterior probability method (MA
P) or the like may be used. There is also a method of estimating a sequence by an iterative operation based on information reliability information.

Further, when the communication system is used in an environment in which the transmission path characteristics between the transmitter and the receiver fluctuate with time, such as in a mobile communication environment, the transmission signal in the transmission path between the transmitter and the receiver has large distortion and signal strength. Variations and the like occur, and there is a high possibility that a transmission data sequence is erroneously transmitted. Therefore, the decoding error rate is high. Therefore, conventionally, transmission path characteristics are estimated and the influence of the transmission path is corrected. For example, as shown in FIG. 44, a receiver has been proposed in which a transmission path characteristic estimating unit 400 is added to the receiver of FIG. 43B. In the receiver of FIG. 44, the transmission path characteristics are estimated based on the received signal and the decoded data as a result of the determination of the received signal in transmission path characteristic estimation section 400, and the transmission path estimated in maximum likelihood sequence estimation section 300 Estimate the most likely sequence, including the effects of the characteristics. For the transmission path estimation, the steepest gradient method, the least squares (LMS) algorithm, the recursive least squares (RLS) algorithm, and the like are used (“Basics of Digital Signal Processing”, IEICE (1988)). )reference).

[0016]

However, if error correction coding is performed to improve the reliability of data transmission, the transmission signal becomes redundant and the efficiency of data transmission is reduced. On the other hand, if error correction coding is not performed so as not to reduce the efficiency of data transmission, the transmission data sequence cannot be accurately estimated.

Further, in a communication environment in which the transmission path characteristics fluctuate over time, even if the transmission path estimation is performed, the transmission path characteristics cannot be accurately estimated if the time fluctuation is fast. That is, the transmission data sequence cannot be accurately estimated.

The present invention has been made in view of the above-described circumstances, and has as its object to propose a receiver capable of accurately estimating a transmission data sequence without lowering data transmission efficiency.

[0019]

In order to achieve the above object, a receiver according to the present invention comprises: receiving means for receiving a transmission signal obtained by multiplexing a plurality of data symbol sequences representing a plurality of transmission data sequences; Converting means for converting the transmission signal received by the means into a plurality of signal sequences each representing a predetermined number of transmission data sequences among the plurality of transmission data sequences represented by the transmission signal; Sequence estimating means for estimating a plurality of transmission data sequences represented by the received transmission signal based on each of the plurality of signal sequences and each of the plurality of expected signal sequences expected for each of the plurality of signal sequences; , Is provided.

That is, the receiving means receives a transmission signal obtained by multiplexing a plurality of data symbol sequences representing each of the plurality of transmission data sequences. The conversion unit converts the transmission signal received by the reception unit into a plurality of signal sequences each representing a predetermined number of transmission data sequences among the plurality of transmission data sequences represented by the transmission signal.

Each of the plurality of signal sequences converted by the conversion means represents a predetermined number of transmission data sequences among the plurality of transmission data sequences represented by the transmission signals. Therefore, each of the plurality of signal sequences converted by the conversion unit is
This is considered to be a signal sequence in which a kind of interference occurs between data symbols of a data symbol sequence representing a predetermined number of transmission data sequences.

If the transmission signal is multiplexed by a predetermined first orthogonal transform, the conversion means
The transmission signal may be converted into a plurality of signal sequences by at least one or more different second orthogonal transforms different from the inverse transform of the first orthogonal transform. In addition, the transforming means converts the transmission signal into a plurality of signals by using an inverse transform of the first orthogonal transform in addition to at least one or more different second orthogonal transforms different from the inverse transform of the first orthogonal transform. You may make it convert into a series. In these cases, the second orthogonal transform may be performed using division by wavelet packets or may be performed using Fourier transform.

[0023] The sequence estimating means expresses the received transmission signal based on each of the plurality of signal sequences converted by the converting means and each of the plurality of predicted signal sequences expected for each of the plurality of signal sequences. Estimating a plurality of transmission data sequences to be performed.

As described above, the received signal sequence is determined based on each of the plurality of signal sequences that are considered to have a type of interference between data symbols and the plurality of predicted signal sequences predicted for each of the plurality of signal sequences. Since a plurality of transmission data sequences represented by the transmission signals are estimated, the transmission data sequences represented by the transmission signals can be estimated without performing error correction coding processing when generating the transmission signals. Therefore, the transmission data sequence can be accurately estimated without lowering the data transmission efficiency.

[0025] Further, the receiver according to the present invention provides an inter-transmitter / receiver based on each of a plurality of signal sequences converted by the conversion means and a plurality of predicted signal sequences predicted for each of the plurality of signal sequences. Transmission path estimating means for estimating the transmission path characteristics of the plurality of signal sequences converted by the conversion means and a plurality of predicted signals predicted for each of the plurality of signal sequences. A plurality of transmission data sequences represented by the received transmission signals are estimated based on each of the sequences and the transmission channel characteristics estimated by the transmission channel estimation means.

That is, the transmission path estimating means determines the transmission path between the transmitter and the receiver based on each of the plurality of signal sequences converted by the conversion means and each of the plurality of predicted signal sequences predicted for each of the plurality of signal sequences. Estimate characteristics.

The sequence estimating means includes a plurality of signal sequences converted by the converting means, a plurality of predicted signal sequences predicted for each of the plurality of signal sequences, and a transmission path characteristic estimated by the transmission path estimating means. , A plurality of transmission data sequences represented by the received transmission signal are estimated.

As described above, since the transmission path estimating means is provided, a plurality of transmission data sequences represented by the received transmission signal are estimated while estimating the transmission path characteristics between the transmitter and the receiver. It is possible to accurately estimate the transmission data sequence represented by the transmission signal even when the characteristics of the transmission path vary with time.

As described above, a transmitter for transmitting a transmission signal obtained by multiplexing a plurality of data symbol sequences representing each of a plurality of transmission data sequences, a receiving means for receiving a transmission signal transmitted by the transmitter, Conversion means for converting the transmission signal received by the reception means into a plurality of signal sequences each representing a predetermined number of transmission data sequences among the plurality of transmission data sequences represented by the transmission signal, and conversion by the conversion means; Estimating means for estimating a plurality of transmission data sequences represented by the received transmission signal based on each of the plurality of signal sequences thus obtained and each of the plurality of prediction signal sequences predicted for each of the plurality of signal sequences. And a communication system including the receiver.

A transmitter for transmitting a transmission signal obtained by multiplexing a plurality of data symbol sequences representing each of a plurality of transmission data sequences, receiving means for receiving the transmission signal transmitted by the transmitter, and receiving means A converting unit that converts the received transmission signal into a plurality of signal sequences each representing a predetermined number of transmission data sequences among the plurality of transmission data sequences represented by the transmission signal; and a plurality of conversion units that are converted by the conversion unit. Transmission path estimation means for estimating transmission path characteristics between the transceiver based on each signal sequence and each of a plurality of expected signal sequences expected for each of the plurality of signal sequences, and a plurality of conversion means Based on each signal sequence and each of the plurality of expected signal sequences expected for each of the plurality of signal sequences and the transmission path characteristics estimated by the transmission path estimation means, the received A receiver having a sequence estimation means for estimating a plurality of transmission data sequence represented by the signal signal, the communication system comprising the proposed.

Further, a plurality of data symbol sequences representing each of the plurality of transmission data sequences are multiplexed and the received transmission signal is converted into a predetermined number of transmission data sequences of the plurality of transmission data sequences represented by the transmission signal. Are converted into a plurality of signal sequences each representing a corresponding one of the plurality of signal sequences, and based on each of the plurality of converted signal sequences and each of the plurality of expected signal sequences expected for each of the plurality of signal sequences, a table is represented by the received transmission signal. A decoding method for estimating a plurality of transmission data sequences to be performed is proposed.

A plurality of data symbol sequences representing each of the plurality of transmission data sequences are multiplexed and the received transmission signal is converted into a predetermined number of transmission data sequences of the plurality of transmission data sequences represented by the transmission signal. Are converted to a plurality of signal sequences each representing the respective, based on each of the plurality of converted signal sequences and each of a plurality of expected signal sequences expected for each of the plurality of signal sequences, transmission path characteristics between the transceivers Estimating, based on each of the converted plurality of signal sequences, each of the plurality of expected signal sequences expected for each of the plurality of signal sequences, and the estimated transmission path characteristics, a table is represented by the received transmission signal. A decoding method for estimating a plurality of transmission data sequences to be performed is proposed.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a first embodiment of the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1, receiver 10A according to the present embodiment receives a transmission signal obtained by multiplexing a plurality of data symbol sequences representing each of a plurality of transmission data sequences by a predetermined first orthogonal transform. The transmission signal received by the reception circuit is represented by the reception circuit by a receiving circuit (not shown) and at least one or more different second orthogonal transformations different from the inverse transformation of the first orthogonal transformation. Transform unit 12A (orthogonal transform circuits 16A, 16B,..., 16X) for converting into a plurality of signal sequences each representing a predetermined number of transmit data sequences among the plurality of transmit data sequences, and outputs from the orthogonal transform unit 12A. Estimating a plurality of transmission data sequences represented by a transmission signal based on each of the plurality of signal sequences to be performed and each of the plurality of expected signal sequences predicted for each of the plurality of signal sequences A transmission data sequence estimating unit 14A that,
It has. In FIG. 1, the orthogonal transform circuit 16A,
Although the orthogonal transformation unit 12A including 16B,..., 16X is shown, only the orthogonal transformation circuit 16A may be used. That is,
The orthogonal transform unit 12A may be configured by a single orthogonal transform circuit 16A that performs an orthogonal transform different from the inverse transform of the first orthogonal transform.

FIG. 2 shows a transmitter 100 having the same configuration as a conventional transmitter (see FIG. 39 (A)), and a receiver 10 which performs an orthogonal transform different from the inverse transform of the orthogonal transform performed on the transmitter side.
A1.

Here, the orthogonal transformation performed on the transmitter side will be described by taking as an example a case where four data symbol sequences are multiplexed by combining them with wavelet packets. Note that the modulation method is BPSK modulation, and the basis function of the wavelet is Dobshi's wavelet (configured by a 4-tap FIR filter).

On the other hand, the receiver 10A1
A1 and a transmission data sequence estimation unit 14A1. The orthogonal transform unit 12A1 includes a single band division filter 2
0A. This results in a wavelet packet division pattern different from that of the transmission side. Therefore, an orthogonal transform output (signal sequence) different from that on the transmitting side is obtained.

Next, the operation of the first embodiment will be described. As shown in FIG. 3A, transmission data to be transmitted is input to the serial / parallel conversion circuit 186 of the receiver 100.

The serial / parallel conversion circuit 186 converts each of the input four transmission data A to D into a parallel transmission data sequence, and then inputs the data to each modulator 184. Note that FIG.
(A) shows a case where four parallel transmission data sequences A to D are 0110 at first and 1110 next. As shown in FIG. 3B, each modulator 184 converts each input transmission data sequence into a symbol representing transmission data, and inputs the symbol to the orthogonal transform unit 116 as a transmission data symbol sequence.

As shown in FIG.
Input transmitted data symbol sequence A _n~ D_n(A₁~ D
₁, A_Two~ D_Two, A_Three~ D_Three...)
Symbol sequence A_n, B_nIs the band for the first frequency band
Input to the synthesis filter 120 and transmitted
Row C_n, D_nIs a second frequency lower than the first frequency band.
It is input to the band synthesis filter 120 for several bands.

Band synthesis filter 1 for first frequency band
At 20, the input transmission data symbol sequences A _n , B
_n (Sampling time interval T /
2), and the band synthesis filter 120 for the second frequency band outputs the input transmission data symbol sequence C _n , D
_n (Sampling time interval T /
Output 2).

That is, after passing through the band synthesis filter 120 (in the case of a 4-tap FIR filter), two signal points input simultaneously at the sampling interval T become signal points of four samples at the sampling interval T / 2. Is converted to

For example, if the data symbols A ₁ and B ₁ are
When input to the band synthesis filter represented by the equation (1), the output is

[0044]

(Equation 3)

It can be understood that a signal of 4 samples can be obtained. Here, the sampling interval of the input signal points corresponds to two samples on the output side. Therefore, the four-sample signals output for each sequentially input signal point overlap each other with a displacement of two samples, and the added signal is output.

That is, as shown in FIG.
Amber A₁, B₁Is entered, then the data symbol
A_Two, B_TwoIs input, the data symbol A₁, B
₁As shown in FIG. 5 (B), the four intervals of the time interval T / 2
Signal point (A₁, B₁)₁, (A₁, B₁)_Two,
(A₁, B₁)_Three, (A₁, B₁)_FourIs output and the data
Ta symbol A_Two, B_TwoFrom the time shown in FIG.
Four sample signal points (A at interval T / 2)_Two, B_Two)₁,
(A_Two, B_Two)_Two, (A_Two, B_Two)_Three, (A_Two, B _Two)
_FourAre output, and they are shifted by 2 samples and
No, they are added together, and finally, as shown in FIG.
Thus, at time interval T / 2, the signal sequence (A₁, B₁)₁,
(A₁, B₁)_Two, (A₁, B₁)_ThreeAnd output (A_Two, B
_Two)₁And the signal sequence ((A₁, B₁)_Three, (A
_Two, B_Two)₁) Is output, and so on. In addition,
Communication data symbol sequence C_n, D_nThe same applies to
Is done.

Then, in the second stage band synthesis filter,
A similar process is repeated. That is, as shown in FIG.
As shown, data symbol A₁, B₁, Data symbol
C₁, D₁Considering that only the
Each of the time intervals T / 2 of 4
The signal point of the sample ((A₁, B₁)₁, (A₁, B₁)
_Two, (A₁, B₁)_Three, (A₁, B₁)_Four),as well as
((C₁, D₁)₁, (C₁, D₁)_Two, (C₁,
D₁)_Three, (C₁, D₁)_Four). And the second stage
Are synthesized by the band synthesis filters of
[(A₁, B₁)₁(C₁, D₁)₁]₁ [(A₁, B₁)₁(C₁, D₁)₁]_Two [(A₁, B₁)₁(C₁, D₁)₁]_Three+ [(A₁,
B₁)_Two(C₁, D₁) _Two]₁ [(A₁, B₁)₁(C₁, D₁)₁]_Four+ [(A₁,
B₁)_Two(C₁, D₁) _Two]_Two.. Are output.

Further, as shown in FIG.
Amber A_Two, B_Two, Data symbol C_Two, D_TwoOnly
Assuming that the power is
Respectively, signal points of 4 samples at time interval T / 2
((A_Two, B_Two)₁, (A_Two, B_Two)_Two, (A_Two,
B_Two)_Three, (A_Two, B_Two)_Four), Sampled signal
((C_Two, D _Two)₁, (C_Two, D_Two)_Two, (C_Two,
D_Two)_Three, (C_Two, D_Two)_Four). And the second stage
Are synthesized by the band synthesis filters of
At interval T / 4, [(A_Two, B_Two)₁(C_Two, D_Two)₁]₁ [(A_Two, B_Two)₁(C_Two, D_Two)₁]_Two [(A_Two, B_Two)₁(C_Two, D_Two)₁]_Three+ [(A_Two,
B_Two)_Two(C_Two, D_Two) _Two]₁ [(A_Two, B_Two)₁(C_Two, D_Two)₁]_Four+ [(A_Two,
B_Two)_Two(C_Two, D_Two) _Two]_Two.. Are output.

As described above, transmission data symbol sequences A _n to
Output signal when the D _n is input all in order, the output signal when the transmission data symbol A ₁ to D ₁ is input, the output signal ... in the case where the transmitted data symbols A ₂ to D ₂ is input Are added to generate a transmission signal, which is transmitted.

The transmitted transmission signal (transmission data synth)
Bol series A_n~ D_nAre synthesized and during the sampling time
The interval T / 4) is connected to a receiving circuit (not shown) of the receiver 10A1.
More received. The transmission signal is orthogonal as shown in FIG.
Single band splitting filter 20A of conversion unit 12A1 (details
The configuration is input to FIG. The transmission signal
Is a band division filter 20A, and a transmission data symbol system
Row A_n, B_nSignal sequence (sampling time
Interval T / 2) and transmission data symbol sequence C_n, D _nGo
To the generated signal sequence (sampling time interval T / 2)
Separated.

That is, a band division filter (a 4-tap FI
In the case of an R filter 20A, the inverse conversion of the band synthesis filter is performed, and as shown in FIG.
As shown in (B), the corresponding converted signal points of one sample are output. Thereafter, every time there are two sample inputs, signal points after conversion are obtained using the signal points of the four samples input so far, and are output. The signal sequence output from the band division filter 20A of the receiver 10A1 and the band synthesis filter 12
The signal sequence output from 0 is exactly the same signal if the delay due to the processing is ignored. That is, as shown in FIG. 9C, the signal sequence output from the band division filter 20A of the receiver 10A1 includes the outputs (A _{1 to} D ₁ ) (4 sample signal points at the time interval T / 2) as shown in FIG. , FIG. 9 (D)
As shown in FIG. 5 (B) and FIG. 5 (C), the output relating to (A _{2 to} D ₂ ) (four samples of the signal points at the time interval T / 2) has components. , And a signal sequence output from the first-stage band synthesis filter 120 of the transmitter 100.

Here, the output from the band division filter 20A
Focusing on only the components A and B of the signal sequence to be
0, output from the band division filter 20A.
The signal sequence is₁, B₁Component (time interval T /
2 signal points 4 samples) and A_Two, B_TwoIngredients for
(4 signal points at time interval T / 2)
You. Therefore, output from the band division filter 20A,
For example, the signal point S₁, S _TwoIs S₁= (A₁B₁)_Three+ (A_TwoB_Two)₁ S_Two= (A₁B₁)_Four+ (A_TwoB_Two)_Two Becomes

Thus, transmission data sequence estimating section 14A1
Starts the control routine (based on the Viterbi algorithm) shown in FIG. 11 when the signal sequence is input from the orthogonal transform unit 12A1.

In step 22 of FIG. 11, a trellis diagram of a portion corresponding to the time t = k at which the signal sequence is input is formed.

Here, as described above, the signal point S₁, S
_TwoIs the transmission data symbol as shown in FIG.
A₁, B₁, A_Two, B_TwoSignal determined by the combination of
Are complex signal points having amplitude and phase, respectively.
You. Since BPSK modulation is used as described above,
Data symbol A₁, B₁, A_Two, B_TwoRespectively
Represents 0,1. Input to the orthogonal transformer of the transmitter at the same time
Two data symbols A₁, B ₁And A_Two, B_TwoIt
Think in pairs.

(A₁, B₁) Is (00,
01, 10, 11), (A _Two, B_Two) Combination
There are four types (00, 01, 10, 11).
Therefore, a total of 16 combinations are conceivable.

By setting each combination of (A ₁ , B ₁ ) and (A ₂ , B ₂ ) as a state, 16 combinations can be represented as state transition branches, as shown in FIG. It can be represented by a trellis diagram.

Note that at the previous time t = k−1,
Since a trellis diagram is formed as shown in FIG. 14A, at this time t = k, the trellis diagram already formed (see FIG. 14A) is added to the trellis diagram shown in FIG. As shown in (2), the part corresponding to the current time t = k is extended.

In step 24, a branch metric is calculated for each branch indicating each state transition of the trellis diagram. In step 26, a path metric up to each state at the time t = k is calculated, and a surviving path (described later) is selected. That is, in this embodiment, a path metric is calculated by adding branch metrics along a plurality of paths that follow branches connecting state points at each time up to each state at the time t = k. Which path is the sequence most likely to be transmitted is evaluated by the magnitude of the value of the path metric, which is the sum of the branch metrics of the branches followed by the path. The path with the largest path metric value is the most likely path (most likely path). In order to find the maximum likelihood path, only the path having the largest path metric is selected from the plurality of paths reaching each state at each time, and the other paths are removed.
The remaining paths are called surviving paths. That is, the number of surviving paths is equal to the number of states in the trellis diagram. Then, in step 28, the transmission data sequence corresponding to the portion determined as the maximum likelihood path is output as decoded data.

Next, the branch metric calculation processing in step 24 will be described in detail with reference to FIG.

In step 34, when signal points S ₁ and S ₂ and a transmission data symbol determined according to the state transition of each branch are transmitted, expected signal points K output as signal points S ₁ and S _{2. The} squared Euclidean distance between ₁ and K ₂ is calculated. In order to calculate the squared Euclidean distance,
The expected signal points K ₁ and K ₂ are obtained in advance. That is, the signal points S _1, the signal point K ₁ ⁰⁰ ~ 16 different for each branch
The K ₁ ^15, the signal point S _2, when obtaining the signal point K ₂ ⁰⁰ ~K ₂ ¹⁵ 16 different in each branch, as follows.

[0062] The signal point _{S 1, S 1 = (A} 1 B 1) 3 + (A 2 B 2) 1 K 1 00 = (00) 3 + (00) 1 K 1 01 = (01) 3 + ( ^{_{00) 1 K 1 02 = (}} 10) 3 + (00) 1 · · · K 1 15 = (11) 3 + (11) 1 , where the signal point of the signal point S types ₁ and 16 K ₁ ⁰⁰ ~K ₁
^{When 15} is displayed on the complex plane, it becomes as shown in FIG. The distance between the signal points S ₁ and the signal point K ₁ ⁰⁰ ~K ₁ ¹⁵ r ₁
⁰⁰ ~r ₁ ¹⁵ square of the square Euclidean distance. If there is no influence of noise or the like, the signal point S ₁ is a signal point K ₁ ⁰⁰ ~
It matches any of K ₁ ¹⁵ .

[0063] Incidentally, for the signal point _{S 2, S 2 = (A} 1 B 1) 4 + (A 2 B 2) 2 K 2 00 = (00) 4 + (00) 2 K 2 01 = (01) ₄ + (00) ₂ K ₂ ⁰² = (10) ₄ + (00) ₂ ... K ₂ ¹⁵ = (11) ₄ + (11) Transmission data determined according to the state transition of each branch, such as ₂ obtains a signal point K ₂ is output as the signal point S ₂ if the symbol has been sent, in the same manner as described above finds square Euclidean distance.

In step 38, the sum of the squared Euclidean distances calculated for each of the signal points S ₁ and S ₂ corresponding to each branch is calculated as a branch metric.

Next, the path metric calculation processing in step 26 will be described in detail with reference to FIG.

At step 42 in FIG. 17, the current time t = k
, A variable s for identifying each state of the trellis diagram corresponding to the above is initialized, and in step 44, the path metric PM of each surviving path reaching each state at the previous time t = k-1.
_{o, k-1 to} PM3 _{, k-1} are taken. In step 46, the path metric of each surviving path at the previous time t = k-1 is
At time t = k, the branch metrics of each branch that transitions to state s are added. That is, in the case of this embodiment, as shown in FIG. 18, there are four branches b = 0, 4, 8, and 12 leading to the state (00) (when s = 0), and each branch has the state (00), (01), (10),
(11) is connected. Therefore, time t = k
There are four paths that reach state (00), and the path metrics for each are PM _{0, k-1} + BM ₀₀ PM _{1, k-1} + BM ₀₄ PM _{2, k-1} + BM ₀₈ PM _{3, k-1} four + BM ₁₂ have been computed.

In step 48, the path having the smallest value of the four path metrics, that is, the path that is most likely, is selected as the surviving path, and the other paths are deleted. Then, the path metric having the smallest value is calculated at time t = k.
Is the path metric of the surviving path that reaches the state (00). That is, assuming that the value of PM _{0, k-1} + BM ₀₀ among the four path metrics is the smallest, the path metric PM _{0, k} of the surviving path that reaches state (00) at time t = _k is PM _{0 ,} and _{k = PM 0, k-1} + BM 00.

Then, in step 50, the variable s is compared with the total number of states s _o (s _o = 4 in the present embodiment), and if there is still a state in which the surviving path at time t = k has not been obtained yet. Increases the variable s by 1 in step 52,
The flow returns to step 44 to perform the calculation for obtaining the path metric of the path reaching the next state, and the above processing (steps 44 to 50) is executed. When the calculation for obtaining the path metrics of all the paths reaching each state is completed in step 50, that is, the addition, comparison, and selection of the surviving paths from the previous time to the current time are performed for all the branches from the previous time to the current time. It has ended.

In the decoded data output process in step 28 (see FIG. 11), all of the surviving paths reaching the respective states at the current time among the states at the time following the time of the decoded data output at the previous time are described. Data representing the state at the time when the path becomes a common path and is determined as the maximum likelihood path is output as decoded data.

That is, as shown in FIG.
At = k-1, the state in which all surviving paths that reach each state up to time t = k-1 are common paths is the state (00) at time t = k-3. Therefore, (0
0) is output as decoded data. At this time, time t
= The state (00) and (01) at k-2 are at time t =
The surviving path has reached the state up to k−1, and it is not known which surviving path is the maximum likelihood path. Therefore, it cannot be output as decoded data.

However, the state at time t = k−2 (0
As shown in FIG. 19 (B), among the states (0) and (01), at time t = k, the state in which all paths surviving to each state until time t = k become a common path is (00). is there. Therefore, (00) is output as decoded data.

As described above, in the present embodiment, each of a plurality of signal sequences obtained by conversion by the orthogonal conversion unit is
2 of the plurality of transmission data sequences represented by the transmission signal
It is considered that each of the plurality of signal sequences is a signal sequence in which a kind of interference occurs between the data symbols of the data symbol sequence representing the two transmission data sequences. This interference is determined by a combination of orthogonal transforms performed on the transmission side and the reception side. Further, what kind of interference occurs is known in advance by the combination of orthogonal transforms to be used. Therefore, it is possible to estimate the maximum likelihood sequence on the receiving side by regarding the interference generated in the output signal from the orthogonal transform unit of the receiver as the interference generated by convolutional coding. Then, it is considered that error rate characteristics can be further improved by performing maximum likelihood sequence estimation by combining a plurality of orthogonal transform outputs on the receiving side.

As described above, since it is not necessary to perform special error correction coding or the like on the transmission side, maximum likelihood sequence estimation can be performed without lowering the data transmission efficiency, and the error rate characteristic is improved. be able to.

Next, a second embodiment of the present invention will be described. As shown in FIG. 20, the orthogonal transform unit 12B1 of the receiver 10B1 according to the second embodiment performs at least two different orthogonal transforms, and one of the two orthogonal transforms is performed by the transmitter side. A plurality of orthogonal transform circuits 16A to 16X, which are orthogonal transforms that are the inverse of the orthogonal transform performed, and a transmission data sequence estimation unit 14B1 that estimates a transmission data sequence based on the outputs of the plurality of orthogonal transform circuits 16A to 16X. Have.

For example, when an orthogonal transform unit (not shown) of a transmitter performs synthesis using wavelet packets as orthogonal transform, the orthogonal transform unit 12B2 of the receiver includes a plurality of band division filters 20 as shown in FIG. The division by wavelet packets may be performed in combination with the stages. As described above, since the band division filter 20 is combined in a plurality of stages, the division pattern in the time / frequency domain can be different in each stage.
Therefore, it has a function of performing at least one or more different orthogonal transforms.

FIG. 22 shows a receiver 10B3 constructed by combining band division filters in two stages.
The receiver 10B3 includes a first-stage band division filter 20.
K1 and second-stage band division filters 20K2 and 20K3 connected to the band division filter 20K1, and an orthogonal transformation unit 12B3 including the first-stage band division filter 20K1
A transmission data sequence estimator 14B3 connected to the first and second stage band division filters 20K2 and 20K3. Note that the band division filter 20K2 is configured so that the signal sequence on the high frequency band side separated by the first stage band division filter 20K1 is input.
0K3 is connected to each of the band division filters 20K1 so that the signal sequence on the low frequency band side separated by the first stage band division filter 20K1 is input. Note that the band division filters 20K1, 20K2, 20
K3 is the aforementioned band division filter 20 (see FIG. 41).
Therefore, the description is omitted.

Next, the operation of the second embodiment will be described. The signal sequence output from the first-stage band division filter 20 is the same as the signal sequence output from the band division filter 20 in the first embodiment described above, and a description thereof will be omitted.

The signal sequence output from the second-stage band division filter 20 is a signal that has been subjected to the orthogonal transform reverse to that on the transmitting side, so each transmission data symbol sequence A before being multiplexed.
~ D.

The band division filters 20K1, 20K2, 2
The transmission data sequence estimating unit 14B3 to which the signal sequence has been input from 0K3 executes the control routine shown in FIG. This control routine has the same parts as the control routine of the first embodiment described above (see FIG. 11). Therefore, the same parts are denoted by the same reference numerals and detailed description thereof will be omitted. That is, the control routine according to the present embodiment corresponds to FIG.
As shown in FIG. 3, steps 22 and 24 are executed, and in the next step 60, the state metric of each state point at the time is calculated, and steps 26 and 28 are sequentially executed.

Next, the state metric calculation processing in step 60 will be described with reference to FIG.

At step 64 in FIG. 24, the signal points (2) of the signal sequences A and B of the four signal sequences A to D input from the second-stage band division filters 20K2 and 20K3.
(In the present embodiment, since the same processing is performed on the signal sequences A and B and the signal sequences C and D,
Processing for signal sequences A and B will be described, and signal sequences C and D will be described.
, And the square Euclidean distance between each data symbol point representing each data expected to be output is calculated. Note that signal sequences A and B
This is because the data symbols are separated into transmission data symbols before being multiplexed, so that they become either 0 or 1 data symbols. Since the BPSK modulation is used as described above, the signal point of the data symbol representing 0 or 1 is ± 1.
Point. FIG. 25 shows the arrangement of signal points on a complex plane. The distances r _A0 , r _A1 , r _B0 , r in FIG.
The square of _B1 is the required squared Euclidean distance. When there is no influence of noise or the like, the signal points A and B coincide with either a data symbol representing 0 or 1.

In step 68, the sum of the squared Euclidean distances obtained for each signal point AB corresponding to each state (state) is calculated as a state metric.

That is, the state metric is calculated from AB = 00: distances r _A0 and r _B0 . AB = 01: _Obtained from the distances r _A0 and r _B1 . AB = 10: _Obtained from distances r _A1 and r _B0 . AB = 11: _Obtained from distances r _A1 and r _B1 .

By the way, in the path metric calculation process of step 26 (see FIG. 23) in the present embodiment, as shown in FIG. 26, the path metric is set to the branch metric calculated for each branch, The state metrics calculated in the corresponding state are added.

As described above, in the present embodiment, the search for the maximum likelihood path is performed by combining two types of outputs from the orthogonal transform unit of the receiver, and the error rate characteristics can be further improved. It becomes possible.

Next, a third embodiment of the present invention will be described. The transmitter (not shown) according to the present embodiment performs a discrete inverse Fourier transform.

As shown in FIG. 27, a receiver 10C according to the present embodiment includes a plurality of Fourier transform circuits 18A to 18X for performing Fourier transforms having different time window widths.
An orthogonal transform unit 12C and Fourier transform circuits 18A to 18X
And a transmission data sequence estimating unit 14C for predicting a transmission data sequence of the received signal based on the output output from the transmission data sequence.

FIG. 28 shows two Fourier transform circuits 18A1 and 18B for performing Fourier transforms having different time window widths.
1 based on the outputs output by the orthogonal transform unit 12C1 and the Fourier transform circuits 18A1 and 18B1.
A transmission data sequence estimating unit 14C1 for predicting the transmission data sequence of the received signal.

Next, the operation of the present embodiment will be described. The Fourier transform circuits 18A1 and 18B1 perform Fourier transforms 1 and 2 having different time window widths. Therefore, two types of orthogonal transform outputs are obtained. That is, the Fourier transform circuit 18A1
Is the same as the time window width of the discrete inverse Fourier transform of the transmitter. Therefore, as shown in FIG. 29, a transmission data symbol sequence separated into a transmission data symbol sequence before being multiplexed on the transmitter side is output. On the other hand, the time window width of the Fourier transform circuit 18B1 is 1/2 of the time window width of the discrete inverse Fourier transform of the transmitter. Therefore, the number of divisions of the frequency band is 2 as shown in the lower part of FIG. Since the time window width is half, by performing the Fourier transform twice with the time shifted so that the time windows do not overlap,
Two signal sequences are output in the time direction. The output signal of the Fourier transform 2 is a signal whose frequency is separated by a bandwidth corresponding to the two signal sequences multiplexed on the transmission side, and the output signal is determined by the two transmission data sequences included in this band.

The transmission data sequence estimating unit 14C1 receiving the above signals from the Fourier transform circuits 18A1 and 18B1
Starts the control routine shown in FIG.

In step 72 of FIG. 30, the signal point of each signal and each data symbol point are evaluated based on the four output signals of the Fourier transform 1 in order to evaluate which transmission data sequence has been transmitted on the transmitting side. To find the squared Euclidean distance of In step 74, the four output signals of the Fourier transform 1 are divided into two combinations of two output signals respectively corresponding to the output signals of the Fourier transform 2, and the signal points corresponding to each combination and the data symbol points described above are divided. From the squared Euclidean distance of と, the signal point corresponding to each combination and the data symbol point
The sum of the squared Euclidean distance is calculated and used as the first metric.

In step 76, the square Euclidean distance between the signal point of the previous output signal in Fourier transform 2 and each of the predicted signal points predicted when each data symbol is combined is calculated as the second metric. . Step 7
In step 8, the square Euclidean distance between the signal point of the output signal after the Fourier transform 2 and each of the predicted signal points predicted when each data symbol is combined is calculated.
Calculate the metric of

In step 80, the first metric
The sum of the third metric is calculated, and at step 82, the first
A combination of digital symbols having the smallest sum of the metric to the third metric is determined, and a transmission data sequence corresponding to the combination is output as decoded data (transmission data sequence).

As described above, in the present embodiment, the discrete inverse Fourier transform is performed on the transmitter side, the plurality of Fourier transforms having different time window widths are performed on the receiver side, and the output by each of the plurality of Fourier transforms is performed. , The transmission data sequence of the received signal is predicted, so that it is not necessary to perform special error correction coding or the like on the transmission side, so that the maximum likelihood sequence estimation is performed while maintaining the maximum efficiency of channel use. It is possible,
The error rate characteristics can be improved.

Next, a fourth embodiment of the present invention will be described. In the first embodiment, a single band division filter 20 is provided as the orthogonal transformation unit 12A1, and the Dobci's wavelet (4
Although the case of a tap FIR filter is shown), other basis functions may be used. As an example, an example in the case of using a Dobshizu wavelet constituted by a 6-tap FIR filter will be described.

As shown in FIG. 31, the orthogonal transform section 12D1 of the receiver 10D1 according to the fourth embodiment has a single-stage band division filter 20D1. The band division filter 20D1 is different from the band division filter 20 described above (FIG. 41).
), Except that the characteristics of the high-pass filter 20A1 and the reduction filter 20A2 are the characteristics shown by the following equation.

[0097]

(Equation 4)

When the orthogonal transform unit of the transmitter (not shown) synthesizes four data symbol sequences using wavelet packets as orthogonal transform, the band synthesis filter of the orthogonal transform unit of the transmitter uses the band synthesis filter 12 described above.
0 (see FIG. 40), the high-pass filter 120B1 and the reduction filter 120B of the band synthesis filter.
It is assumed that the characteristic of No. 2 is a characteristic shown by the following equation.

[0099]

(Equation 5)

Except for the characteristics of each filter, the configuration is the same as that of the first embodiment, and a description thereof will be omitted.

Next, the operation of the fourth embodiment will be described. The signal sequence output from the first-stage band division filter 20D1 is the same as the output of the first-stage band synthesis filter of the transmitter 100, as in the first embodiment. FIG. 32 shows only the components A and B of the signal sequence output from the band division filter 20D1. Signal points S ₁ and S ₂ shown in FIG. 32 are different from those in the first embodiment in that
One transmission data symbol A ₁ , B ₁ , A ₂ , B ₂ ,
This signal is determined by the combination of A ₃ and B ₃ . That is, S ₁ = (A ₁ B ₁ ) ₅ + (A ₂ B ₂ ) ₃ + (A ₃ B ₃ )
₁ S ₂ = (A ₁ B ₁ ) ₆ + (A ₂ B ₂ ) ₄ + (A ₃ B ₃ )
It becomes ₂ .

In this case, four data symbols A ₁ , B
₁ , A ₂ , and B ₂ into one set of four data symbols A
₂ , B ₂ , A ₃ , and B ₃ are considered as another set. 2
The two sets have a relationship in which the time input to the orthogonal transform unit of the transmitter is shifted by one symbol.

(A ₁ , B ₁ , A ₂ , B ₂ ), (A ₂ , B
₂ , A ₃ and B ₃ ) are 16 combinations each. By keeping this combination in a state, a trellis diagram shown in FIG. 33 may be formed. The signal points S ₁ and S ₂ can be represented by state transition branches that connect states common to the data symbols A ₂ and B ₂ . Note that there is no branch between states where the data symbols A ₂ and B ₂ are different.

In the subsequent processing, similar to the first embodiment, the same processing can be performed by calculating the predicted signal points of the signal points S ₁ and S ₂ , calculating the branch metric, and performing the same processing.

Therefore, it was shown that the present invention can be implemented even in the case of a Dob's wavelet in which the basis function of the wavelet is composed of 6 taps. Similarly, different wavelet basis functions can be used.

Next, a fifth embodiment of the present invention will be described. As shown in FIG. 34, the receiver 10E1 according to the fifth embodiment does not directly convert the received signal sequence into the output signal of the orthogonal transformer 12A1 of the receiver 10A1 of the first embodiment. The output signal to be output is added. As one of the output signals from the orthogonal transform unit 12E1, the received signal is directly output as a converted output signal sequence. This can be considered as a special case of orthogonal transformation. The other configuration is the same as that of the first embodiment, and a description thereof will be omitted.

The operation of the fifth embodiment will be described. Since the received signal sequence is the transmission signal itself described in the first embodiment, the description is omitted.

FIG. 35 shows a trellis diagram according to the present embodiment.
Show some. The signal sequence that outputs the received signal as it is
Signal sequences A, B, C, and D are synthesized. This message
Since the signal sequence is a signal sequence with a time interval of T / 4, four
Signal point S₁~ S_Fourthink of. Signal point S₁~ S_FourAre each
12 data symbols A₁~ D₁, A_Two~ D_Two, A _Three
~ D_ThreeIs represented by Think in the same way as in the fourth embodiment
FIG. 35 shows a part of the formed trellis diagram.

The calculation of the branch metric can be performed in the same manner as described in the embodiment.

Next, the processing of the output of the band division filter 20E1 of the orthogonal transformer 12A1 will be described. The output of the band division filter 20E1 performs the same processing as the calculation of the branch metric in the first embodiment. The branch metric in the first embodiment is a value determined for a combination of data symbols A ₁ , B ₁ , A ₂ , and B ₂ . In the present embodiment, data symbols A ₁ ,
Any of the states corresponds to the combination of B ₁ , A ₂ , and B ₂ . Therefore, the value obtained by performing the same processing as the calculation of the branch metric in the first embodiment is converted to the first metric in the state corresponding to the combination of the data symbols A ₁ , B ₁ , A ₂ , and B _2. May be used. The same processing is performed on the combination of the data symbols C ₁ , D ₁ , C ₂ , and D ₂ , and the combination is used as the second metric. By using the sum of the first metric and the second metric as the state metric of each corresponding state, processing can be performed in the same manner as in the second embodiment.

Next, a sixth embodiment of the present invention will be described. As shown in FIG. 36, a receiver 10F1 according to the sixth embodiment further includes a transmission path estimator 400F1 in addition to the receiver 10A1 of the first embodiment. FIG.
, The transmission path estimating unit 400F1 includes a one-sample delay element 404 and a coefficient 40 representing the estimated transmission path characteristic.
6 and an estimated transmission path characteristic updating unit 402 for updating the coefficient
Consists of

The operation of the sixth embodiment will be described. The transmission channel estimation unit 400F1 estimates transmission channel characteristics using the signal sequence output from the orthogonal transformation unit 12F1 and the expected signal sequence obtained from each surviving path output from the transmission data sequence estimation unit 14F1, Output the estimated transmission path characteristics.

In transmission data sequence estimating section 14F1, the signal output from orthogonal transform section 12F1 and transmission path estimating section
A transmission data sequence is estimated using the estimated transmission path characteristics output from 0F1.

The transmission path estimating section 400F1 will be described with reference to FIG. The channel estimation unit 400F1 can use various algorithms similar to the conventional channel estimation. However, the present embodiment is characterized in that the input signal used for channel estimation is different from the conventional case. Transmission path estimation unit 4
FIG. 37 shows a configuration example in which the transmission path characteristics are estimated by the LMS algorithm as 00F1.

The transmission path estimating section sends the signal having the distortion or the fluctuation of the signal strength in the transmission path as the signal of the orthogonal transform section 12F.
Inputting the output signal x _k from 1. At the same time, a signal d _k which is a reference when distortion and fluctuation do not occur is input. Here, the characteristics of the estimated transmission path at time t = k are

[0116]

(Equation 6)

Will be described. Transmission line characteristics are correct
If estimated, the transmission path estimated for the reference signal
, The one-sample delay element 404
By combining the estimated transmission path characteristic coefficient 406
Signal d '_kAnd the output signal x from the orthogonal transform unit _kWhen
Should be equal. Therefore, the following equation holds
One.

[0118]

(Equation 7)

However, when the characteristics of the transmission path fluctuate with time, the above equations are not equal, and an error occurs. Therefore, the error signal e _k

[0120]

(Equation 8)

Is obtained. Estimated transmission path characteristic update unit 40
In step 2, using the error signal e _k , the coefficients g ⁰ _k , g ¹ _k , and g ² _k of the channel characteristics are sequentially updated according to the following equation.

[0122]

(Equation 9)

Here, Δ represents a step size at the time of updating, and * represents a complex conjugate. Output signal x from orthogonal transform unit
By repeating the above processing every time _k and the reference signal d _k are input, it is possible to estimate a transmission path characteristic that fluctuates with time.

The reference signal d _k is a signal expected to be output from the orthogonal transform unit 12F1 when it is not affected by the transmission path characteristics. This sequence of the reference signal is the same signal as the expected signal points K ₁ and K ₂ used for calculating the branch metric of the branch on the path representing the correct transmission data sequence in the transmission data sequence estimation unit 14F1.
Therefore, the sequence of the expected signal points is transmitted to the transmission path estimating section 400F.
Enter 1 To do so, it is necessary to know the path representing the correct transmission data sequence.
Each surviving path at the stage of obtaining the most likely path that is likely to be a path representing a correct transmission data sequence is used. The expected signal points K ₁ and K ₂ used in calculating the branch metric of each surviving path are determined by the transmission path estimation unit 400F.
1 to estimate a transmission path characteristic that fluctuates with time. Since there are the same number of surviving paths as the number of states in the trellis diagram, transmission path estimation also estimates each surviving path.

Next, a description will be given of a process of performing sequence estimation in transmission data sequence estimation section 14F1 using the estimated transmission path characteristics. The expected signal points K ₁ K ₂ used when calculating the branch metric do not include the influence of the transmission path characteristics. Therefore, the expected signal points K ₁ and K ₂ are corrected using the transmission path characteristics estimated at that time. The predicted signal points after the correction are K ′ ₁ and K ′ ₂ . The branch metric is calculated using the corrected predicted signal point.

Since the transmission path characteristics used for correction are estimated for each surviving path, the transmission path characteristics estimated for each surviving path are used for each branch connected from each surviving path. Good.

Each branch metric is calculated, the path metric is calculated, and when a new surviving path is selected, the expected signal points K ₁ and K ₂ used for calculating the branch metric corresponding to the selected surviving path are calculated. , To the transmission path estimation unit 400F1.

Therefore, transmission data sequence estimation is performed using the transmission path characteristics estimated at a certain point in time, and when a new surviving path is selected, the expected signal is used as a reference signal for estimating the transmission path characteristics at the next point in time. Points K ₁ and K ₂ are used. That is, for each surviving path, the processing proceeds while alternately repeating the transmission data sequence estimation and the transmission path estimation.

As described above, in the present embodiment, by providing the transmission path estimating section for estimating the transmission path characteristic that fluctuates over time, even in a communication environment where the transmission path characteristic fluctuates over time, Good error rate characteristics can be obtained. Further, in the present embodiment, transmission path estimation is performed using a signal sequence whose time interval is half (T / 2) of the data symbol. Therefore, compared to the conventional case where the transmission path is estimated for each data symbol, the transmission path characteristics can be accurately estimated even when the transmission path fluctuates quickly, and the error rate characteristics can be improved. .

In the present embodiment, transmission path estimation is performed using a signal having a time interval half that of a data symbol. However, orthogonal transform that can obtain a signal with a shorter interval is used, and the output signal is It is also possible to estimate transmission path characteristics.

In the above-described embodiment, the 4-tap and 6-tap wavelet wavelet basis functions have been described. However, the present invention is not limited to this.
It may be applied to a basis function such as tapped decimation.

In the embodiment described above, the BP
Although the case of SK modulation is shown, the present invention is not limited to this, and other modulation methods, for example, QPSK modulation, 8P
SK modulation, 16QAM modulation and the like can also be used. Although the case where four data symbol sequences are multiplexed as the multiplexing of a plurality of data symbol sequences is shown, the present invention is not limited to this, and can be used even when the number of multiplexing is different. That is, a plurality of data symbol sequences other than 4 may be multiplexed. The division is not limited to the equal division, and may be applied to a case where the division is not equal.
Further, in the present invention, it is not necessary to perform error correction coding in advance, but it is also possible to use a case where error correction coding has already been performed.

In the above-described embodiment, the orthogonal transform is used to convert a transmission signal into a plurality of signal sequences each representing a predetermined number of transmission data sequences among a plurality of transmission data sequences represented by the transmission signal. However, the present invention is not limited to this, and any conversion method can be used as long as the conversion result is expected in advance.

[0134]

As described above, according to the present invention, a plurality of transmission data sequences represented by a transmission signal can be estimated without performing error correction coding processing when generating a transmission signal. It is possible to accurately estimate the transmission data sequence without lowering the data transmission efficiency,
It has the effect of.

Further, according to the present invention, since the transmission path estimating means is provided, a plurality of transmission data sequences represented by the received transmission signals are estimated while estimating the transmission path characteristics between the transmitter and the receiver. The transmission data sequence represented by the transmission signal can be accurately estimated even when the characteristics of the transmission path between the devices change with time.

[Brief description of the drawings]

FIG. 1 is a block diagram of a receiver according to a first embodiment.

FIG. 2 is a block diagram of a communication system including another receiver according to the first embodiment.

FIG. 3 is a diagram illustrating a process of forming a transmission signal.

FIG. 4 is another diagram showing a process of forming a transmission signal.

FIG. 5 is a diagram showing a process of converting a transmission signal.

FIG. 6 is another diagram showing a process of converting a transmission signal.

FIG. 7 is yet another diagram showing a transmission signal conversion process.

FIG. 8 is a diagram illustrating conversion by a band division filter.

FIG. 9 is another diagram showing conversion by a band division filter.

FIG. 10 is yet another diagram illustrating conversion by a band division filter.

FIG. 11 is a flowchart showing a main control routine.

FIG. 12 is a diagram illustrating components of a signal sequence input to a transmission data sequence estimation unit.

FIG. 13 is a trellis diagram.

FIG. 14 is a diagram showing a process of forming a trellis diagram.

FIG. 15 is a flowchart showing a subroutine of step 24 of the main control routine.

FIG. 16 is a diagram for describing a square Euclidean distance in the first embodiment.

FIG. 17 is a flowchart showing a subroutine of step 26 of the main control routine.

FIG. 18 is a diagram illustrating a method of calculating a path metric according to the first embodiment.

FIG. 19 is a diagram illustrating a method of selecting decoded data.

FIG. 20 is a block diagram of a receiver according to a second embodiment.

FIG. 21 is a block diagram of another receiver according to the second embodiment.

FIG. 22 is a block diagram of still another receiver according to the second embodiment.

FIG. 23 is a flowchart illustrating a main control routine according to the second embodiment.

FIG. 24 is a flowchart showing a subroutine of step 60 of the main control routine.

FIG. 25 is a diagram for describing a squared Euclidean distance in the second embodiment.

FIG. 26 is a diagram illustrating a method of calculating a path metric according to the second embodiment.

FIG. 27 is a block diagram of a receiver according to a third embodiment.

FIG. 28 is a block diagram of another receiver according to the third embodiment.

FIG. 29 is a diagram showing output contents by two Fourier transforms having different time window widths.

FIG. 30 is a flowchart showing a main control routine.

FIG. 31 is a block diagram of a receiver according to a fourth embodiment.

FIG. 32 is a diagram illustrating conversion by a band division filter according to the fourth embodiment.

FIG. 33 is a trellis diagram according to the fourth embodiment.

FIG. 34 is a block diagram of a receiver according to a fifth embodiment.

FIG. 35 is a diagram showing a part of a trellis diagram according to the fifth embodiment.

FIG. 36 is a block diagram of a receiver according to a sixth embodiment.

FIG. 37 is a detailed block diagram of a transmission path characteristic estimation unit.

FIG. 38 is a block diagram of a communication system according to the related art.

FIG. 39 is a block diagram of another communication system according to the related art.

FIG. 40 is a detailed block diagram of a band synthesis filter.

FIG. 41 is a detailed block diagram of a band division filter.

FIG. 42 is a block diagram illustrating a configuration of various orthogonal transform units when division is performed using a wavelet packet.

FIG. 43 is a schematic block diagram of a communication system when performing error correction encoding and decoding processing corresponding to the error correction encoding.

FIG. 44 is a schematic block diagram of a receiver that performs decoding processing corresponding to error correction encoding and estimates transmission path characteristics.

[Explanation of symbols]

 10A1 Receiver 12A1 Orthogonal Transformation Unit (Conversion Means) 14A1 Transmission Data Sequence Estimation Unit (Sequence Estimation Means) 10B3 Receiver 12B3 Orthogonal Transformation Unit (Conversion Means) 14B3 Transmission Data Sequence Estimation Unit (Sequence Estimation Means) 10C1 Receiver 12C1 Orthogonal Transform Unit (conversion unit) 14C1 Transmission data sequence estimation unit (sequence estimation unit) 10D1 receiver 12D1 Orthogonal conversion unit (conversion unit) 14D1 Transmission data sequence estimation unit (sequence estimation unit) 10E1 receiver 12E1 Orthogonal conversion unit (conversion unit) 14E1 Transmission data sequence estimation unit (sequence estimation unit) 10F1 receiver 12F1 orthogonal transformation unit (conversion unit) 14F1 transmission data sequence estimation unit (sequence estimation unit) 400F1 transmission channel estimation unit (transmission channel estimation unit)

Claims (5)

[Claims] 1. A receiving means for receiving a transmission signal obtained by multiplexing a plurality of data symbol sequences representing each of a plurality of transmission data sequences, and transmitting a transmission signal received by the receiving means to a plurality of transmission signals represented by the transmission signal. Conversion means for converting a plurality of transmission data sequences into a plurality of signal sequences each representing a predetermined number of transmission data sequences; and a plurality of signal sequences converted by the conversion means and each of the plurality of signal sequences are predicted. Sequence estimation means for estimating a plurality of transmission data sequences represented by the received transmission signal based on each of the plurality of expected signal sequences. 2. A transmission for estimating a transmission path characteristic between a transmitter and a receiver based on each of a plurality of signal sequences converted by the conversion unit and each of a plurality of predicted signal sequences predicted for each of the plurality of signal sequences. Further comprising channel estimating means, wherein the sequence estimating means estimates each of the plurality of signal sequences converted by the converting means, each of a plurality of predicted signal sequences expected for each of the plurality of signal sequences, and the transmission path estimating means The receiver according to claim 1, wherein a plurality of transmission data sequences represented by the received transmission signal are estimated based on the obtained transmission path characteristics. 3. The transmission signal is multiplexed by a predetermined first orthogonal transform, and the transform unit is different from an inverse transform of the first orthogonal transform and at least one or more different from each other. 3. The receiver according to claim 1, wherein the received transmission signal is converted into a plurality of signal sequences by a second orthogonal transform. 4. The transmission signal is multiplexed by a predetermined first orthogonal transform, and the transforming means is different from an inverse transform of the first orthogonal transform and has at least one or more The receiver according to claim 1, wherein the received transmission signal is converted into a plurality of signal sequences by different second orthogonal transform and inverse transform of the first orthogonal transform. 5. The receiver according to claim 3, wherein the second orthogonal transform is performed using division by a wavelet packet or performed using Fourier transform.