JPH07143110A - Communication system using pseudo period series - Google Patents

Abstract

PURPOSE:To provide a communication system using a pseudo period series in which the reception signal similar to the input of an infinite length period series is obtained from the input signal of the period series of a finite length. CONSTITUTION:Let information to be transmitted be (b), then the information (b) is received through a matching filter with respect to a signal (a0, a1,..., aN-1) whose length is N which receives a transmission signal (an-L, aN-1, a0,..., aL-1) whose length is N+2L.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a communication system suitable for a mobile communication system and the like, and particularly, a communication using a pseudo-periodic sequence which enables a signal designed as a periodic sequence to be used in an approximately synchronized state. Regarding the scheme.

[0002]

2. Description of the Related Art Periodic signals are used in a system for communicating between mobile stations whose distance to a terminal station changes, such as mobile communication known as a cellular radio communication system. At present, the above communication system uses an analog frequency division multiplexing or time division multiplexing modulation method, but in the future a digital code division communication method such as a digital code division multiple access method will be adopted. Is certainly seen.

It is known that a periodic sequence is easier to design in signal design for this kind of code division multiplex communication.
For example, 1985, Computer Science
Published by Press, M.I. K. Simon, J .; K. O
mura, R.M. A. Scholtz, B .; K. Levi
tt, "Spread Spectrum Com"
"Munications".

[0004]

Commonly used for this type of spread spectrum communication system is a periodic sequence with no side lobes in the autocorrelation. For example, a periodic series ...
・ 1,1,1, -1,1,1,1, -1,1,1,1,
When -1, ..., (1, 1, 1, -1 is 1 cycle) is input to the matched filter, ..., 0, 4, 0,
A beautiful output of 0,0,4,0,0,0,4,0, ... Is obtained.

However, one cycle (1,
1,1, -1) is input to the above matched filter,
The output becomes (-1, 0, 1, 4, 1, 0, -1), which is messy. That is, a desired reception output is obtained for an input of an infinite length period sequence, but an output different from the desired output is obtained for an input of finite length.

An object of the present invention is to provide a communication system using a quasi-periodic sequence which is a signal system capable of obtaining a received signal similar to the input of an infinite-length periodic sequence even for an input signal of a finite-length periodic sequence. To provide.

[0007]

In order to achieve the above object, the present invention is such that when the information to be transmitted is b, b (a
_NL , ..., a _N-1 , a ₀ , ..., a _N-1 , a ₀ ,
, A _L-1 ) having a length N + 2L as a transmission signal, and having a length N (a ₀ , a ₁ , ..., A _N-1 )
The information b is received through a matched filter for the signal of.

That is, one period (1,
For example, (1, -1,1,1,1, -1, -1,1,1) in which a repeating portion having a length of 2 is added before and after (1,1, -1) is created. The repetitive part of the length 2 to be added is a part of one cycle (···· −1), which is added before the one cycle, and a part of one cycle (1,1 ···) is added. It is added after the one cycle. Note that this additional portion has a length of at least 1.

When this is input to the matched filter, (-
The output of 1, 2, -1, 0, 0, 4, 0, 0, 1, 2, 1) is obtained, and the central portion of length 5 (... 0, 0,
4, 0, 0 ...) is the same as when the periodic sequence is input. This property is suitable for a code division multiplex communication system (such as an approximate synchronous cellular CDMA) that can be synchronized to some extent but is not perfect.

The present invention can be further configured as follows. (1) Let A be a finite length sequence of length N, and let the periodic sequence (...
.. A, A, A, ...), which is a part of A, A, A ...), has a length longer than N and includes A in it is A ', and a signal obtained by multiplying A'by information to be transmitted is used as a transmission signal. Information is obtained by transmitting and providing a matched filter of A on the receiving side and passing the received A ′ through this matched filter.

・ ・ ・ ・, ───A───, ───A───, ・ ・ ・ ・ ・ │ ← ───A'─── → │ (2) Cross correlation There are no n periodic sequences ・ ・ ・ ・ A ₁ , A ₁ , A ₁ , A ₁・ ・ ・ ・ ・ ・ ・ A ₂ , A ₂ , A ₂ , A ₂・ ・ ・ ・ ・ ・··· A _i , A _i , A _i , A _i ········· A _n , A _n , A _n , A _n . The i-th set is a transmission signal obtained by modulating A _i ′ with information to be transmitted, and information is obtained by demodulating with a matched filter of A _i provided on the receiving side. (3) In the above (1) and (2), when the modulation information is a and b, a signal obtained by adding aA ′ and bA ′ with a time shift is used as a transmission signal.

[0012]

In the above-mentioned configuration of the present invention, the periodic sequence ...
・ ・ 、 ───A─── 、 ───A─── 、 ・ ・ ・ ・ ・ ・
Assuming that the finite length sequence A designed so that its autocorrelation function has a special property is the transmission signal and the matched filter of A is the receiver, the autocorrelation function of the finite length sequence A is output. This is a periodic sequence ... A, A, A ,.
.. has a property different from that of the autocorrelation function, the conventional problem that there is no design-dependent effect is solved as follows.

A = (a _0, a _1, ... a _N-1 ), (length N) A ′ = (a _NL, a _{N-L + 1,} ... A _{N-1 ,} a _0, a ₁ ...
-A _N-1, a _0, a ₁ ... a _L-1 ), (length N + 2L), A'connects the L component from before A after A,
The result is that the L component is connected before A and after A.

When A is input to the matched filter of A ', the length of the output signal becomes (2N + 2L-1), and the central portion (2L + 1) has a periodic sequence ...
The characteristics of the autocorrelation function of A───, ───A───, ... The same applies to the cross-correlation function. A periodic sequence with no cross correlation can be created as follows.

That is, the periodic sequence ... A ₁ ...
a _{a N a 1 ···· a N ····} , , It is written as a cyclic matrix.

A periodic sequence can be expressed as a cyclic normal matrix by cyclically cycling through one period to form each row of a square matrix and normalizing the norm. By this notation, orthogonal sequences are represented as unitary matrices, and polyphase periodic sequences are represented as polyphase matrices. By the way, as is well known, the cyclic convolution is expressed by a cyclic matrix, but it can also be considered as multiplication in a Fourier transformed region. Therefore, assuming that a certain cyclic matrix is A and a diagonal matrix having a sequence obtained by Fourier transforming one row of A as a diagonal component is B, A = F ⁻¹ BF (...) ). However, F is a DFT matrix.

If A is a unitary matrix, the diagonal matrix B must also be a unitary matrix according to equation (1). That is, the absolute value of the diagonal component of B must be 1. Therefore, Fourier transform of the orthogonal sequence results in a polyphase periodic sequence. Further, if the absolute value of the diagonal component of B is 1, A becomes a unitary matrix, so if the inverse Fourier transform of the polyphase periodic series is performed, it becomes an orthogonal series.

When the time axis is reversed and considered, the polyphase periodic series is Fourier transformed to form a polyphase periodic series. Next, a polyphase periodic sequence having no cross correlation will be described. Now, when there are two periodic sequences and they are represented by cyclic matrices A and C, respectively, there are diagonal matrices B and D having a relationship of A = F ⁻¹ BF C = F ⁻¹ DF.

Since the cross-correlation function of A and C is expressed as A ^* C ^* = F ^-1 BD ^* F, if all the diagonal elements of the diagonal matrix BD ^* are 0, then they are expressed by A and C. The cross-correlation function of the two periodic sequences is 0 at all shifts. This condition can be restated as that the spectra of the two periodic sequences represented by A and C do not overlap. However, C
^* Is an adjoint matrix of C (a matrix in which the components are transposed into a complex conjugate).

For example, (1,0,1,0,1,0,-
1,0) and (0,1,0,1,0,1,0, -1) such that multiple orthogonal sequences such that the product of each component is 0 are set in the frequency domain and these are inverted. The Fourier transform yields a plurality of periodic sequences in which the absolute value of the component is constant in the time domain and the cross-correlation function is 0 at every shift.

The Nth-order discrete Fourier transform matrix is F _N = [f _N (i, j)], 0 ≦ i ≦ N−1, 0 ≦ j ≦ N−1, f _N ((i, j) = (1 / √N) exp {(-2π√-1) · ij / N)} However, by the two orthogonal sequences in the above example and the 8th order discrete inverse Fourier transform, However, W _N = exp {(2π√-1) / N}.

As described above, the cross-correlation function of two periodic sequences obtained by repeating each of the two columns on the right side of the equation (2) should be 0 at every shift. On the other hand, the autocorrelation functions of these two periodic sequences are 0
When the shift component is normalized to 1, it is (1,0,0,0,1,0,0,0) and (1,0,0,0, -1,0,0,0).

This is because the component of j of F ₆ ^-1 is an even number (j =
0,2,4,6) is a repetition of the cycle 4, while a component with an odd j has the following relationship: if a component satisfying 0 ≦ i ≦ 3 is multiplied by −1, a component satisfying 4 ≦ i ≦ 7 is obtained. This is because it can be obtained. Similarly, in general, there are M orthogonal sequences with a period MN, and an appropriate one period is extracted from these M orthogonal sequences as M finite length sequences, and any of these M finite length sequences is selected. When the product of the corresponding components of the two finite-length sequences of M can be made 0, the M finite-length Fourier transform of these M finite-length sequences yields M polyphase finite-length sequences. In the M polyphase periodic sequences obtained by repeating the M finite length sequences, any two cross-correlation functions become 0 at any shift.

In particular, the orthogonal sequence of the period MN is 0 ≦ k ≦ M.
For k of −1, 0 except for the k-th (Mod M) component,
When the k-th (Mod M) component is extracted and becomes an orthogonal sequence of period N, the autocorrelation function of the multi-phase periodic sequence obtained by MN-order inverse Fourier transform of the orthogonal sequence of period N is
It becomes 0 at all shifts other than a multiple of N, and 0 ≦ t ≦ M
−1, the tN shift becomes exp {(2π√−1) kt / M}.

For example, The autocorrelation functions of the four polyphase periodic sequences obtained by repeating each of the four columns on the right side of are (1, 0, 0,
1,0,0,1,0,0,1,0,0), (1,0,
0, √-1, 0, 0, -1, 0, 0, -√-1, 0, 0),
(1,0,0, -1,0,0,1,0,0, -1,0,
0), (1, 0, 0, -√-1, 0, 0, -1, 0, 0, √-
It becomes 1,0,0).

The four columns in the above equation (3) are sequences of length 12 (N = 12). Here, when L = 2, weak synchronization code division multiplex communication in which both the side lobe of autocorrelation and the cross-correlation are 0 for deviations within 2 can be realized.

[0027]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 is a schematic block diagram for explaining an embodiment of a main part configuration of a transmitter to which a communication system using a pseudo-periodic sequence of the present invention is applied. 1 is a data buffer for storing information to be transmitted, 2 Is a data set generating means for generating a data set for each modulation unit, 3 to 6 are memories # 1 to # 4 for storing code modulated data, and 7 to 10 are information 1 in the data set from the data set generating means 2. , -1 corresponds to a multiplier for multiplying by "1" or "-1", 11 is an adder, and 12 is a transmitting means.

In the figure, memories # 1 to # 4 are multipliers 7
10 to 10 are shown by being shifted by the amount corresponding to the timing of transmitting the modulated data B. In the figure, the data of the transmission information is once stored in the data buffer 1, and then is sequentially supplied to the multipliers 7 to 10 as a set of modulation units by the data set generation means 2 at a predetermined timing.

From the # 1 memory 3 to # 4 memory 6, the path train of the modulated signal B is output from the multipliers 7 to 7 in synchronization with the above timing.
10 of the data from the data set generation means 2
1 "or" -1 "is multiplied by" 1 "or" -1 ". The outputs of the multipliers 7 to 10 are added in the adder 11 and given to the transmitting means 12 as a time series signal. The means 12 transmits this time-series signal by carrying it on an appropriate carrier signal.

FIG. 2 is a schematic diagram for explaining an example of the structure of the modulated signal, where B is a modulated signal of length N, and this modulated signal B
In addition, one unit of the transmission signal (length N + 2) is obtained by adding the rear end signal B _R for the length L to the front part and adding the front end signal B _F for the length L.
L) and store them in the # 1 memory 3 to # 4 memory 6 of FIG. 1, respectively. When actually designing the circuit, it is preferable that only one memory is provided and the signal output timing thereof is controlled by a separately provided control means to sequentially output.

FIG. 3 is a schematic diagram for explaining an example of the transmission signal supplied to the transmission means of FIG. 1, and here shows the transmission signal corresponding to the data (1, 1, -1, 1). Figure 4
2 is a schematic block diagram for explaining an embodiment of the main configuration of a receiver to which the communication system using the pseudo-periodic sequence of the present invention is applied, in which 21 is receiving means and 22 is the modulated signal B shown in FIG.
The matched filter 23 is a time axis adjusting means.

In the figure, the transmission signal received by the receiving means 21 as shown in FIG.
Passed through 2. The demodulated signal passed through the B matched filter 22 is reproduced as follows. 5A and 5B are explanatory diagrams of the signal processing of the receiver. FIG. 5A is a data “1” signal that has passed through the matched filter B, and FIG. 5B is a data “−1” signal.
(C) shows the addition signal of (a) and (b), and (d) shows the reproduction information data which was subjected to the shaping process after the time axis adjusting means 23 adjusted the time axis of the pulse train to the same as the transmission information data.

As described above, according to the present embodiment, it is possible to obtain a reception signal which is synchronized with the input of the infinite length cyclic sequence by using the signal of the cyclic sequence of finite length.

[0034]

As described above, according to the present invention,
A signal that can be beautifully designed for an input signal of a finite-length periodic sequence as well as an input of an infinite-length periodic sequence, and a signal that is designed as a periodic sequence can be used in an approximate synchronization state. It is possible to provide a communication method having an excellent function by using the pseudo-periodic sequence as the method.

[Brief description of drawings]

FIG. 1 is a schematic block diagram illustrating an example of a main configuration of a transmitter to which a communication method using a pseudo-periodic sequence of the present invention is applied.

FIG. 2 is a schematic diagram illustrating one configuration example of a modulation signal used in one embodiment of a communication system using a pseudo periodical sequence of the present invention.

FIG. 3 is a schematic diagram illustrating an example of a transmission signal supplied to the transmission unit of FIG.

FIG. 4 is a schematic block diagram illustrating an example of a main configuration of a receiver to which a communication method using a pseudo-periodic sequence of the present invention is applied.

FIG. 5 is an explanatory diagram of signal processing of a receiver.

[Explanation of symbols]

1 data buffer for storing information to be transmitted 2 data set generating means for generating a data set for each modulation unit 3 to 6 memory # 1 to memory # 4 for storing code modulated data 7 to 10 from data set generating means 2 A multiplier for multiplying a data set by "1" or "-1" corresponding to the information 1 or -1. 11 adder 12 transmitting means 21 receiving means 22 matched filter of modulated signal B 23 time axis adjusting means.

[Procedure amendment]

[Submission date] June 23, 1993

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0026

[Correction method] Change

[Correction content]

The four columns of the above equation (3) are sequences of length 12 (N = 12). Here, when L = 2, weak synchronization code division multiplex communication in which both the side lobe of autocorrelation and the cross-correlation are 0 for deviations within 2 can be realized. In the above description, L is L and L ′ having the same length, and L = L ′, that is, L = 2L, but it is also possible to set L ≠ L ′ and the length of the transmission signal. Can be represented by {N + (L + L ')} in the general formula.

Claims (1)

[Claims] 1. When the information to be transmitted is b, b (a
_NL , ..., a _N-1 , a ₀ , ..., a _N-1 , a ₀ ,
, A _L-1 ) having a length N + 2L as a transmission signal, and having a length N (a ₀ , a ₁ , ..., A _N-1 )
A communication system using a pseudo-periodic sequence, characterized in that the information b is received through a matched filter for the signal of.