JP3420642B2 - Transmission method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a transmission system using multicarrier.

[0002]

2. Description of the Related Art In recent years, a multi-carrier transmission system has attracted attention as a digital transmission system. The multi-carrier transmission method uses a large number of carriers that are orthogonal to each other.
In this method, the signal speed per carrier is slow and the bandwidth is narrow, so that it is resistant to multipath.

The technology related to the multi-carrier transmission system is
For example, the document "Bingham, JAC," Multicarrier Modulatio
n for Data Transmission: An Idea Whose Time Has Co
me ", IEEE Commu. Mag., vol.28, no.5, pp.5-14, May 1990
"It is described in.

FIG. 11 shows an example of the configuration on the transmitting side and the receiving side that realizes this method.

[0005] As shown in FIG.
The information data of the block (block length M) is converted by the serial / parallel converter 30, each data is modulated (for example, PSK, QAM) by the modulator 31, and transmitted by the inverse discrete Fourier transformer (IDFT) 32. A block is created. The IDFT 32 converts a signal on the frequency axis into a signal on the time axis, and thus generates a signal in which M carriers arranged in equal frequency intervals are combined. The transmit signal block is
The signal is converted into an analog signal by the D / A converter 33, unnecessary frequency components are removed by the filter 34, converted into a radio frequency band by the amplifier 35, amplified, and then transmitted from the antenna.

As shown in FIG. 11B, on the receiving side, the received radio signal is converted / amplified into a base band band by an amplifier 31 and an unnecessary frequency component is removed by a filter 37, and then an A / D converter. At 38, it is converted into a digital signal.
Further, this signal is decomposed into equal frequency intervals by a discrete Fourier transformer (DFT) 39 for each block, and each signal is demodulated by a demodulator 40. Then, the parallel / serial converter 41 reproduces the information data.

The transmission signal is a noise-like signal in which a large number of carriers are added, but each carrier is a modulated sine wave.

In the multi-carrier transmission system, as the number of data in one block is increased, in other words, the number of carriers is increased, the signal speed per carrier becomes slower and the bandwidth per carrier becomes narrower, resulting in fading. It is possible to reduce the distortion caused by the above, and an equalizer having a complicated structure is unnecessary.

[0009]

In the conventional multicarrier transmission system, since block transformation is performed by orthogonal transformation such as DFT in block processing, block synchronization is required, but the received multicarrier signal is a noise-like signal. There is a problem that the method of block synchronization is not established.

Further, the inverse discrete Fourier transform is a block process, and each carrier signal becomes a discontinuous signal between blocks as in the example of each carrier signal of the transmission signal shown in FIG. 12, and the bandwidth is expanded. There is a problem.

Further, the conventional multicarrier transmission system has the following problems. That is, in recent years, in digital transmission, the transmission information is hierarchized into highly important information and less important information, and the receiving side responds to receiving conditions such as signal level, noise level, and fading, if the receiving conditions are good, for example. Hierarchical signal transmission is important in that all information is reproduced, and at least the information of high importance can be reproduced when reception conditions are bad. However, in the conventional multi-carrier transmission system, the reception performance is improved as the number of carriers is increased and the bandwidth of each carrier is narrowed, but the bandwidth of each carrier is uniform as shown in FIG. Therefore, it is impossible to perform efficient transmission by allocating a carrier having a narrow bandwidth to information having high importance and allocating a carrier having a wide bandwidth to information having low importance. In addition, the conventional multi-carrier transmission method has a drawback that block synchronization is required because block processing is performed. The larger the number of carriers, the more processing for synchronization.

The present invention has been made to solve such a problem, and an object thereof is to provide a transmission system capable of obtaining highly accurate timing information.

It is another object of the present invention to provide a transmission method capable of reducing discontinuity between blocks of each carrier signal and suppressing an increase in bandwidth.

Further, according to the present invention, a carrier having a narrow bandwidth can be assigned to information having high importance, and a carrier having a wide bandwidth can be assigned to information having low importance, so that efficient signal transmission can be realized. The purpose is to provide a transmission method.

The present invention also eliminates the need for block processing,
It is an object of the present invention to provide a transmission method that does not require even block synchronization.

[0016]

In order to solve such a problem, the transmission system of the present invention has a transmitter and a receiver, and in the transmitter, at least a transmission signal is divided into blocks of a predetermined length. Then, the transmission block signal is generated, the transmission block signal is input to the inverse orthogonal transformer, the transmission conversion signal is generated, and in the receiving device, at least the reception signal is input to the wavelet transformer, and the reception signal is predetermined. The reception block signal is generated by dividing the block into blocks having a predetermined length at a timing, the reception block signal is input to an orthogonal transformer to generate a reception conversion signal, and the predetermined timing is given from the wavelet transformer. And In such a transmission method, the predetermined timing may be obtained from time-by-time synthesis of arbitrary one or more output signals of the plurality of output signals of the wavelet transformer. The predetermined timing may be obtained by synthesizing an arbitrary one or more output signals of the plurality of output signals in a predetermined time interval.

A transmission system according to another aspect has a transmitter and a receiver, and in the transmitter, at least the transmission signal is divided into blocks of a predetermined length to generate a transmission block signal, and the transmission signal is transmitted. An inverse orthogonal transformer generates a transmission transformed signal from the block signal, the receiving device divides at least the received signal into blocks of a predetermined length to generate a received block signal, and the received block signal is received by the orthogonal transformer. It is characterized in that a transformed signal is generated, and the inverse orthogonal transformer and the orthogonal transformer have a basis function that extends over an arbitrary plurality of blocks.

Furthermore, another aspect of the transmission system has a transmitter and a receiver, and in the transmitter, at least a plurality of transmission signals are input to a signal combiner and combined into one transmission signal, In the receiving device, at least a received signal is input to a signal analyzer, decomposed into a plurality of received signals, and the signal analyzer has a function of dividing one signal into a plurality of signals having different bandwidths, The signal combiner has a function of combining a plurality of signals having different bandwidths into one signal. In such a transmission method, the plurality of transmission signals are signals that are layered according to importance, and the higher the importance, the more the signal synthesizer and the signal analyzer are made to correspond to the signal having a narrower bandwidth. Alternatively, the signal synthesizer may use wavelet inverse transform means, and the signal analyzer may use wavelet transform means.

[0019]

According to the present invention, since the wavelet transform is used to extract the block synchronization timing information from the received signal in the multi-carrier transmission based on the orthogonal transformation by the block processing, it is possible to obtain highly accurate timing information. .

Further, by using the orthogonal transform in which the basis function is spread over a plurality of blocks for the orthogonal transform and the inverse orthogonal transform, the discontinuity between the blocks of each carrier signal is reduced and the expansion of the bandwidth is suppressed. To be done.

Further, by using a wavelet transform means having a non-constant bandwidth pass characteristic, a carrier with a narrow bandwidth is assigned to information of high importance, and a carrier with a wide bandwidth is assigned to information of low importance. It becomes possible to allocate, efficient signal transmission is realized, and block synchronization becomes unnecessary.

[0022]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a diagram showing a configuration of a transmitting side and a receiving side according to a first embodiment of the present invention.

As shown in FIG. 1A, on the transmitting side,
Similar to the conventional technique shown in FIG. 1, one block (block length M) of transmission information data is converted in parallel by the serial / parallel converter 30, and each data is modulated by the modulator 11 (for example, PSK, QAM). And the inverse discrete Fourier transformer (I
A transmission signal block is generated by the DFT) 12. I
The DFT 12 converts a signal on the frequency axis into a signal on the time axis, and thus generates a signal in which M carriers arranged at equal frequency intervals are combined. The transmission signal block is converted into an analog signal by the D / A converter 13, and unnecessary frequency components are removed by the filter 14. Then, after being converted / amplified into a radio frequency band by the amplifier 15, it is transmitted from the antenna.

As shown in FIG. 1B, on the receiving side, the received radio signal is converted into a baseband band by the amplifier 16.
After being amplified and the unnecessary frequency component is removed by the filter 17, it is converted into a digital signal by the A / D converter 18. Further, this digital signal is decomposed into equal frequency intervals by a discrete Fourier transformer (DFT) 19 for each block, and each signal is demodulated by a demodulator 20. Then, the parallel / serial converter 21 reproduces the received information data.

Since the DFT 19 performs block processing, it requires a timing signal for blocking. Therefore, the A / D converted signal is input to the wavelet transformer 22, and the timing signal is obtained from the output. The wavelet transform is used in the field of signal processing and signal analysis, for example, the document "O. Rioui and M. Vetterli:" Wavelets a
nd Signal Processing ", IEEE SP Magazine, pp.14-38, O
The technology is described in "ct. 1991.".

FIG. 2 shows the configuration of a 4-division orthogonal wavelet transformer 22 which performs such wavelet transformation. As shown in the figure, in the orthogonal wavelet transformer 22, the input signal x is input to a high pass filter (HPF) 201 and a low pass filter (LPF) 202, and divided into two bands. Furthermore, the sampling circuit 203,
Every other signal is thinned out by 204 and down-sampled to ½. The output on the high frequency side is again HPF20.
5 and the LPF 206, and further downsampled to 1/2 by the sampling circuits 207 and 208. After that, the HPF 209, the LPF 210, and the sampling circuits 211 and 212 perform the same processing as above. In the example of FIG. 2, as a result, as shown in FIG. 3, band division of octave intervals with a ratio of 1: 1: 2: 4 is realized from the low band to the high band. Here, the output X shown in FIG.
₀ , X ₁ , X ₂ , and X ₃ are 1 /
Filtering operation downsampled to 8, 1/4, 1/2, 1/2 with impulse response of 1:
It can be seen as the result of processing in which the filters of 2: 4: 4 are arranged in parallel and the input x is passed. On the other hand, the filtering is a linear transformation using the impulse response as a transformation basis. From the above, as shown in FIG. 4, it can be seen that in the wavelet transform, the conversion base length differs depending on the frequency, and the higher the conversion base, the shorter the base length.

It can be seen from FIGS. 3 and 4 that the frequency resolution is high for low frequency signals and the time resolution is high for high frequency signals. Generally, a signal discontinuity point includes a high frequency, but the wavelet transform makes it possible to detect the time position of the discontinuity point.

In FIG. 1B, the received signal is a noise-like signal in which many carriers are added, but each carrier is a modulated sine wave. P as the modulation method
When SK or QAM is used, each carrier has a discontinuity at the change point of the data symbol, and this change point of the data symbol becomes the block synchronization timing. Therefore,
When the received signal is input to the wavelet transformer 22, the time when discontinuity occurs can be detected from the output, and the synchronization timing can be obtained from this. Specifically, FIG.
As shown in (a), the power of any one or more of the outputs X ₀ , X ₁ , X ₂ , and X ₃ of the orthogonal wavelet transformer is added at each time to exceed the predetermined reference value. The timing information can be obtained from the time.

Further, since the time width (T) of one block is predetermined, the discontinuity is generated periodically, so that FIG.
As shown in (b), the power of the correlation value of each T-time delayed signal of any one or more outputs of the outputs X ₀ , X ₁ , X ₂ , and X ₃ of the orthogonal wavelet transformer is calculated at each time. , And timing information can be obtained from the time when a predetermined reference value is exceeded.

Further, when the received signal is a complex number, the timing information can be detected by the wavelet transform from either the real number component or the imaginary number component, and the timing information can be obtained from the complex number signal by using the wavelet transform extended to the complex number. You can also The number of divisions of the orthogonal wavelet transformer is not limited to four. Also, other wavelet transforms such as non-orthogonal wavelet transform can be applied.

Next, a second embodiment of the present invention will be described.
FIG. 6 is a diagram showing the configurations of the transmitting side and the receiving side according to this embodiment.

As shown in FIG. 6A, on the transmitting side, one block of information data is converted in parallel by the serial / parallel converter 610, and each parallel data is modulated by the modulator 611. The modulation method is BPSK, QPSK, Q
Although there are various types such as AM, BPSK is used here as an example. Next, the modulation signal is subjected to inverse orthogonal transform, but an overlap transformer 612, which is an orthogonal transform having a basis function across a plurality of blocks, is used. The overlap transformer 612 is developed for the purpose of reducing block distortion, which is a problem in image / speech encoding using the discrete cosine transform (DCT), and there are various types, for example, the document “Malvar,
HS, "Lapped Transform for EfficientTransform / Subb
and Coding ", IEEE Trans. ASSP, Vol.38, No.6, June 199
0, pp. 969-978. "Can be used. The configuration of the overlap inverse orthogonal transformer 612 is shown in FIG. The processing here is performed by the following equation (1).
According to (4), the signal X _m (k) (k =
0, ..., M-1) is converted into a signal x _m (n) (n = 0, ..., M-1) on the time axis.

[0034] _{x m (n) = y m} -1 (n + M / 2) h (M-1-n) -y m (M / 2-1-n) h (n) (2) n = 0, ..., _{M / 2-1 x m (n)} = y m-1 (3M / 2-1-n) h (M-1-n) + y m (nM / 2) h (n) (3) n = M / 2, ..., M-1 However, h (n) = sin [(π / 2M) (n + 0.5)] (4) In these equations (1) to (4), the signal of the current block (block length M) The signal y _m (n) (n = 0, ..., M / 2-1) generated by discrete sine transform of X _m (k) (k = 0, ..., M-1) and the signal of the previous block (block A signal y _m-1 (n) (n = M / 2, ..., M-1) generated by performing a discrete sine transform of a length M) X _m-1 (k) (k = 0, ..., M-1) And are combined to generate a signal x _m (n) (n = 0, ..., M-1). Therefore, the processing spans two blocks (the block length is 2M), which is the current block and the previous block. In FIG. 7A, ↑ M is upsampling to M times, and Z ^−M is 1
The block long delay, Z ⁻¹ , represents the delay of 1 / M time of one block length. In FIG. 6A, the overlap inverse-orthogonal-transformed signal is converted into an analog signal by the D / A converter 613 as in the prior art, and the filter 6
After removing unnecessary frequency components by 14, the amplifier 6
The signal is converted into a radio frequency band and amplified by 15 and is transmitted from the antenna.

As shown in FIG. 6B, on the receiving side, as in the prior art, the received radio signal is converted and amplified by the amplifier 616 into a baseband band, and after unnecessary frequency components are removed by the filter 617, A / D converter 618
Are converted into digital signals by. Then, the converted digital signal is input to the overlap orthogonal converter 619. Here, as shown in FIG. 7 (b), a signal x _m (n) (n = 0, ..., M-1) on the time axis of the block length M is overlapped and orthogonally transformed by transposing with the transmitting side. Signal X
Convert to _m (k) (k = 0, ..., M-1). ↓ M represents downsampling to 1 / M. The above discrete sine transform (DST) can be easily processed by a high speed algorithm. In FIG. 6B, each signal is further demodulated by the demodulator 620, and then the parallel / serial converter 621 reproduces the data.

FIG. 8 shows a transmission signal in this embodiment which has been subjected to overlap processing. In the present embodiment, the discontinuity of each carrier between blocks is reduced and the band spread is suppressed. In the above-described embodiment, the overlap processing of two blocks is performed, but the invention is not limited to this, and it is possible to extend to the overlap processing of an arbitrary block length in which the length of the basis function is increased. Continuity is further reduced.

Further, in the above-mentioned embodiment, BPSK is used as the modulation method, but the present invention is not limited to this, and by expanding the overlap processing to a complex number, QPSK, Q
Various modulation methods such as AM can be used. In this case, the overlap processing can be extended to complex numbers.

Next, a third embodiment of the present invention will be described.
FIG. 9 is a diagram showing the configurations of the transmitting side and the receiving side according to this embodiment.

As shown in FIG. 9A, on the transmitting side, the information to be transmitted is, for example, 4 according to the importance by the information decomposer 910.
It is decomposed into hierarchies and four types of information sequences are generated, each of which has P
Modulation such as SK or QAM is performed by the modulator 11,
Four types of modulated signal sequences X ₀ (k), X ₁ (k), X ₂ (k), X
₃ (k) is generated. Where the bandwidth of each signal is B
₀ [Hz], B ₁ [Hz], B ₂ [Hz], B ₃ [H
z]. Then, B ₁ = B ₀ , B ₂ = 2B ₀ , B ₃
= 4B ₀ , the relationship of octave intervals is assumed, and the narrower the signal bandwidth and the slower the speed, the more important the information is.
Four types of transmission signal sequences X ₀ (k), X ₁ (k), X ₂ (k), X
₃ (k) is input to the orthogonal wavelet inverse transformer 912 having a non-constant bandwidth pass characteristic.

FIG. 10 shows the configuration of the 4-input orthogonal wavelet inverse transformer 912. As shown in FIG. 10, in the orthogonal wavelet inverse transformer 912, 0 is interpolated between the signal points of the upsampling circuits 1001 and 1002 to upsample twice, and then the HPF 1003.
And the process of inputting into the LPF 1004 are repeated.

The orthogonal wavelet transformer 919
Has the same configuration as that shown in FIG.

When the signal is input by directly connecting the orthogonal wavelet transformer and the orthogonal wavelet inverse transformer, the original signal can be obtained as an output.

In FIG. 9, four types of transmission signal sequences X ₀
If (k), X ₁ (k), X ₂ (k), and X ₃ (k) are input signals to the orthogonal wavelet inverse transformer 912, X ₀ (k), X ₁ (k), X
₂ (k) and X ₃ (k) correspond to signals of bandwidths B ₀ , B ₁ , B ₂ and B ₃ , respectively, as shown in FIG.
(n) is a multicarrier signal that combines them.

X (n) is converted into an analog signal by the D / A converter 913 as in the prior art, and is filtered by the filter 914.
After the unnecessary frequency component is removed by the amplifier 15,
Is converted and amplified by the radio frequency band by and transmitted from the antenna.

As shown in FIG. 9B, on the receiving side, as in the prior art, the received radio signal is converted and amplified by the amplifier 916 to the baseband, and unnecessary frequency components are removed by the filter 917, It is converted into a digital signal by the A / D converter 918. Next, this signal is input to the orthogonal wavelet transformer 919, decomposed into four signals, demodulated by the demodulator 920, and information layered according to the degree of importance is generated. The information is played.

In this embodiment, since a signal of higher importance is assigned to a carrier in a narrow band, it is possible to avoid the influence of deterioration of reception quality due to fading or the like. Therefore,
Depending on the receiving conditions such as signal level, noise level, and fading, for example, if the receiving conditions are good, all the information can be reproduced, and if the receiving conditions are bad, at least highly important information can be reproduced. Hierarchical signal transmission is easily realized. In addition, since the present embodiment does not use orthogonal transform by block processing as in the conventional technique, there is also an advantage that block synchronization is unnecessary.

In the above-mentioned embodiment, the wavelet transform / inverse transform means is not limited to the orthogonal wavelet transform and the orthogonal wavelet inverse transform with the division number 4, and various kinds of wavelet transform and inverse transform means can be used. . When the signal has a complex number, the wavelet transform and the inverse transform can be extended to support a complex number. Furthermore, it is possible to perform stronger error correction coding and improve transmission characteristics for a signal assigned to a carrier having a wider bandwidth.

[0048]

As described above, according to the present invention,
By using the wavelet transform to extract the block synchronization timing information from the received signal in multicarrier transmission based on orthogonal transform by block processing,
Obtaining highly accurate timing information is realized.

Further, by using the orthogonal transform in which the basis function spanning a plurality of blocks is used for the orthogonal transform and the inverse orthogonal transform, the discontinuity between blocks of each carrier signal is reduced and the expansion of the bandwidth is suppressed. It

Further, by using a wavelet transform means having a non-constant bandwidth pass characteristic, a carrier with a narrow bandwidth is assigned to information of high importance, and a carrier with a wide bandwidth is assigned to information of low importance. Allocation is possible, efficient signal transmission is realized, and in this case, since block processing is not performed, block synchronization is unnecessary.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a first exemplary embodiment of the present invention.

FIG. 2 is a diagram showing an orthogonal wavelet transformer used in the first embodiment of the present invention.

FIG. 3 is a diagram showing band division characteristics of orthogonal wavelets.

FIG. 4 is a diagram showing a conversion base of an orthogonal wavelet transform.

FIG. 5 is a specific configuration of a timing extraction circuit used in the first embodiment of the present invention.

FIG. 6 is a diagram showing a configuration of a second exemplary embodiment of the present invention.

FIG. 7 is a diagram showing an overlap converter used in a second embodiment of the present invention.

FIG. 8 is a diagram showing a transmission signal according to a second embodiment of the present invention.

FIG. 9 is a diagram showing a configuration of a third exemplary embodiment of the present invention.

FIG. 10 is a diagram showing an orthogonal wavelet inverse transformer used in the third embodiment of the present invention.

FIG. 11 is a diagram showing a conventional multi-carrier transmission system.

FIG. 12 is a diagram showing a conventional transmission signal.

FIG. 13 is a diagram showing band division characteristics of a conventional technique.

[Explanation of symbols]

10 ... Serial / parallel converter, 11 ... Modulator, 12 ... Orthogonal wavelet inverse converter, 13 ... D / A converter, 14 ...
Filter, 15 ... Amplifier, 16 ... Amplifier, 17 ... Filter, 18 ... A / D converter, 19 ... Orthogonal wavelet converter, 20 ... Demodulator, 21 ... Parallel / serial converter, 22 ...
Wavelet transformer.

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Claims (7)

(57) [Claims] 1. A transmission device and a reception device, wherein the transmission device divides at least a transmission signal into blocks of a predetermined length to generate a transmission block signal, and the transmission block signal is processed by an inverse orthogonal transformer. Input, to generate a transmission conversion signal, in the receiving device, at least the reception signal is input to the wavelet transformer, the reception signal is divided into blocks of a predetermined length at a predetermined timing to generate a reception block signal, A transmission method, wherein the reception block signal is input to an orthogonal transformer to generate a reception conversion signal, and the predetermined timing is given from the wavelet transformer. 2. The predetermined timing is obtained from time-wise synthesis of arbitrary one or more output signals among a plurality of output signals of the wavelet transformer.
The described transmission method. 3. The transmission according to claim 1, wherein the predetermined timing is obtained by synthesizing any one or more output signals of the plurality of output signals of the wavelet transformer at a predetermined time interval. method. 4. A transmission device and a reception device, wherein the transmission device divides at least a transmission signal into blocks of a predetermined length to generate a transmission block signal, and the transmission block signal is processed by an inverse orthogonal transformer. A transmission conversion signal is generated, and in the reception device, at least the reception signal is divided into blocks of a predetermined length to generate a reception block signal, the reception block signal is generated by an orthogonal transformer, and the inverse conversion is performed. A transmission method characterized in that an orthogonal transformer and the orthogonal transformer have a basis function that extends over an arbitrary plurality of blocks. 5. A transmission device and a reception device are provided, wherein the transmission device inputs at least a plurality of transmission signals to a signal combiner and combines them into one transmission signal, and the reception device has at least a reception signal. To a signal analyzer and decomposed into a plurality of received signals, the signal analyzer has a function of dividing one signal into a plurality of signals having different bandwidths, and the signal combiner has a bandwidth A transmission method having a function of combining a plurality of different signals into a single signal. 6. The plurality of transmission signals are signals hierarchized according to importance, and the higher the importance, the more the signal synthesizer and the signal analyzer correspond to the narrower bandwidth signals. The transmission method according to claim 5, wherein 7. The transmission system according to claim 5, wherein the signal synthesizer uses wavelet inverse transform means and the signal analyzer uses wavelet transform means.