JPH09168003A - Detector using shift register and dft to detect synchronization sequence set having excellent correlation characteristic - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make synchronization by configuring the detector with a shift register shifting an input signal of a prescribed pseudo period sequence, an N-point DFT hardware providing an orthogonal sequence with a prescribed period from the signal, an inverter and a complex adder so as to detect the sequence. SOLUTION: The filter has a shift register 1, a DFT hardware 2, some inverters 3 and complex adder 4. Then the signal adopts a pseudo period sequence whose length is N+2L and whose pseudo period is N and the filter employs a definite length sequence with respect to the definite length sequence with a length N. Then each of N output terminals of the shift register 1 connects to one input terminal of the N-point DFT hardware 2. Furthermore, the some inverters 3 are connected to output terminals of the DFT hardware 2 so that the output of the inverters 3 is a binary spectrum of a matched signal. Then all outputs are collected by the complex adder 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pseudo polyphase periodic sequence and a method for detecting a finite length sequence called a pseudo periodic sequence having a length of N + 2L and a pseudo period of N.

[0002]

2. Description of the Related Art The present inventors have proposed a kind of pseudo-polyphase periodic sequence set having very good autocorrelation and cross-correlation (N. Suehiro, "Pseudo").
-Polyphase orthogonal seq
ounce sets with good cros
correlation property ”, Ap
plied Algebra, Algebraic A
lgorithms and Error-Corre
cting Codes, Lecture Notes
in Computer Science 508,
pp. 106-112, Springer-Verla
g, 1990). A sequence set is obtained from m sequences by a digital filter (DFT). The present inventors have further proposed a method for designing a finite length sequence called a pseudo period sequence having a length N + 2L and a pseudo period N (N. Suehiro, “Signal d”).
design without co-channel
interface for approxim
ately synchronized CDMA s
systems ”, IEEE Journal on S
elected Areas in Communic
ations, vol. 12, pp. 837-841
June 1994).

Hereinafter, these sequences will be described.

<Pseudo Polyphase Orthogonal Sequence Set> When the autocorrelation function is zero for all terms except the periodic multiplex, the periodic sequence is called an orthogonal sequence. Hereinafter, a method for obtaining a certain class of pseudo-polyphase orthogonal sequence set will be described (N. Suehiro). N
Each set of P pseudo-orthogonal sequences is D
It is introduced from the m sequence by FT. However, N is the period of the sequence. To transform a shifted m sequence of period N by an N-point inverse DFT matrix, N
There is a street way. For example, if N is 3,

[0005]

[Equation 1] The polyphase periodic sequence is converted into an orthogonal sequence by DFT. By converting the shifted m sequence using the N-point inverse DFT matrix, N orthogonal sequences of period N can be obtained. The absolute value of each element in the obtained pseudo-polyphase orthogonal sequence is

[0006]

(Equation 2) Becomes The autocorrelation function of each sequence is (10 ... 0). The absolute value of the cross-correlation function between any two sequences in the set is

[0007]

(Equation 3) Becomes

<Polyphase Periodic Sequence Set without Cross Correlation> The inventors have proposed a method of forming a class of polyphase periodic sequence sets without a cross correlation function.
In each set, the cross-correlation function between any two sequences is zero for all terms. For example,
x ₁ , x ₂ , x ₃ , x ₄

[0009]

(Equation 4) And Since (111-1) becomes an orthogonal sequence when iterates, (100010001000-1000) also becomes an orthogonal sequence when iterates. Therefore, (... tx1 ^t x1 ^t x1 ...) is a polyphase periodic sequence, and (... ^t x2 ^t x2 ^t x2 ...), (... ^t x3 ^t x3 ^t x3 ...). .),
(... ^t x4 ^t x4 ^t x4 ...) is also a polyphase periodic sequence for the same reason. However, ^t (.) Indicates transposed (.). The cross-correlation function between any two of these polyphase periodic sequences will be zero for all terms.

<Pseudo Periodic Sequence> The correlation characteristic of the periodic sequence is easier than that of the finite length sequence. The inventors of the present application have proposed the concept of pseudo-periodic sequences in order to easily design the correlation characteristics of finite-length sequences (N. Suehiro). Let A = (a ₀ , a ₁ , ..., A _N-1 ) be a finite length sequence of length N. It is designed to have good cyclic correlation properties. A '= (a _N-1 , ..., a _N-1 , a ₀ , a ₁ , ..., a _N-1 , a ₀ , a ₁ ,
Let ..., a _L-1 ) be a finite sequence of length N + 2L. here,
Its central part of length N corresponds to A. When the sequence A'is input to the filter matched to the sequence A, the cross-correlation function between A'and A has length 2N.
The output signal of + 2L-1 corresponds. The central portion of length 2L + 1 in the output signal of the filter is from the -L shift term to L
Periodic sequence (... AAA) up to the shift term
A. . . ) Autocorrelation function of. Let B be a finite length sequence of length N. Sequence A'is sequence B
When input to the matched filter, the central part of the output signal of the filter of length 2L + 1 is likewise composed of two periodic sequences (... AAAAA ...) And (... BBB).
B. . . ), The cross-correlation function between

For example, assume that A = (111-1), N = 4 and L = 2. When (... AAAAA ...) Is input to the matched filter for A, the output signal is (... 40004000 ...). When A is input to the same filter, the output signal is (-1014
10-1). When A '= (1-1A11) is input to the same filter, the output signal is (-12-1004
00121). A ′ is called a pseudo-periodic sequence of length N + 2L and pseudo-period N. <Approximately Synchronized CDMA System> The present inventors have proposed a signal design method without co-channel interference for an approximately synchronized CDMA system (N. Suehiro). This signal design is good for cellular automobile personal communication systems. By this method,
A pseudo-periodic sequence set obtained from the polyphase periodical sequence set without cross-correlation is designed. Length N + 2L
And a pseudo-period sequence of pseudo-period N is input to a filter matched to a finite-length sequence of length N corresponding to the input signal, the center of the output signal is a pulse,
The side lobes are zero for small shifts.
The sidelobe characteristics are very good for multipath effects. On the other hand, when the pseudo period sequence of length N + 2L and the pseudo period N is input to the filter matched with the finite length sequence of length N that does not correspond to the input signal, the central part (small shift part) of the output signal becomes zero. Become. This property means that there is no co-channel interference. The above method for signal design is a solution to the near / far problem. However, when the near / far problem is less severe, a more efficient quasi-polyphase quasi-periodic sequence set is obtained, which is obtained from the quasi-polyphase quasi-periodic sequence set obtained from the DFT shifted m-sequence.

[0012]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method for detecting the above sequence using a shift register, a DFT, and an inverter and providing the synchronization.

[0013]

In order to achieve the above object, a filter for a binary spectrum or a four-phase spectrum sequence according to the present invention, for an input signal of a pseudoperiodic sequence of length N + 2L and pseudoperiod N, A shift register for shifting this signal, one input terminal connected to each of the N output terminals of this shift register, N point DFT hardware for giving N orthogonal sequences of period N from the signal, and this N point It consists of an inverter connected to the DFT hardware and forming the binary spectrum of the matched signal, and a complex adder connected to this inverter and adding its outputs.

[0014]

The above-mentioned sequence is a pseudo-polyphase complex sequence, but the output of the DFT is 1 or-when synchronized.
Becomes 1. Therefore, no multiplier is needed to detect these sequences. The method of the present invention can be used for synchronization in CDMA systems.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of a synchronization sequence detector according to the present invention will be described below. Matched Filters for Binary Spectral or Quadrature Spectral Sequences Above, we have described several sets of binary spectral sequences with very good correlation properties. In general, it is possible to design a binary spectral or 4-phase sequence set with good correlation properties that is easier than a binary or 4-phase sequence set. Here, a filter design method for a binary spectrum or a four-phase spectrum sequence is proposed. This filter has a shift register, DFT hardware, some inverters and a complex adder. Signal length N + 2
Let L and the pseudo period sequence of pseudo period N, and let the filter be a finite length sequence for a finite length sequence of length N. Each of the N output terminals of the shift register is connected to one of the input terminals of the N-point DFT hardware. Some inverters are connected to the output terminals of the DFT hardware such that they consist of the binary spectrum of the matched signal. All outputs are collected in the complex adder. This filter uses DFT hardware and inverters instead of multiple complex multipliers.

[0016]

As described above, according to the present invention,
Aligned with a shift register for shifting an input signal of pseudo-period sequence of length N + 2L and pseudo-period N, and DFT hardware providing N orthogonal sequences of period N from the shifted signal. By providing the inverter that configures the binary spectrum of the signal, it is possible to detect the synchronization sequence set with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a synchronization sequence detector according to the present invention.

[Explanation of symbols]

 1 shift register 2 DFT hardware 3 inverter 4 complex adder

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshikatsu Naito 2-1-1 Otani, Samukawa-cho, Takaza-gun, Kanagawa Toyo Communication Equipment Co., Ltd.

Claims (1)

[Claims] 1. A shift for inputting a quasi-multiphase periodic sequence set which is obtained from an m sequence by DFT and has good autocorrelation and cross-correlation, and a finite length sequence called a pseudoperiodic sequence, and shifts this signal One input terminal is connected to each of the register and the N output terminals of this shift register, and the signal is connected to N-point DFT hardware for giving N orthogonal sequences of period N and the N-point DFT hardware. A detector comprising: an inverter that forms a binary spectrum of a matched signal; and a complex adder that is connected to the inverter and adds the outputs thereof.