KR100766866B1 - Apparatus for Searching Cell in Orthogonal Frequency Division Multiple Access System and Method for Making Cell Searching Code by Using the Same - Google Patents

Abstract

The present invention relates to a cell search apparatus of an orthogonal frequency division multiplexing system and a method for constructing a cell search code using the same.

The present invention provides a terminal cell search apparatus and an implementation method in an orthogonal frequency division multiplexing system, and provides a code structure capable of efficient cell search even in the presence of a timing offset.

The present invention can be expected to implement an efficient cell search code that is less sensitive to timing offset in a modulation / modulation scheme using multiple carriers.

Orthogonal Frequency Division Multiplexing System, Cell Search Code, Cell Number, Cell Group Number

Description

Apparatus for Searching Cell in Orthogonal Frequency Division Multiple Access System and Method for Making Cell Searching Code by Using the Same}

1 is a diagram illustrating a frame structure of a conventional OFDMA system.

FIG. 2 is a diagram illustrating a structure of a CCP-P in the frame structure of the OFDMA system of FIG. 1.

3 is a block diagram schematically illustrating an internal configuration of a cell search apparatus according to an exemplary embodiment of the present invention.

4 is a block diagram schematically illustrating an internal configuration of a cell number determining unit of a cell search apparatus according to an exemplary embodiment of the present invention.

5 is a block diagram schematically illustrating an internal configuration of a cell group number determination unit of a cell search apparatus according to an embodiment of the present invention.

6 is a diagram illustrating a cell number continuous arrangement of CN0 according to an embodiment of the present invention.

7 is a diagram illustrating a cell number continuous arrangement of CN1 according to an embodiment of the present invention.

8 is a diagram showing a cell group number continuous array CGN0 consisting of CN0 and CN1 according to an embodiment of the present invention.

9 is a diagram illustrating a cell group number continuous array CGN5 consisting of CN3 and CN4 according to an embodiment of the present invention.

10 is a flowchart illustrating a code configuration method for cell search using a cell search apparatus according to an embodiment of the present invention.

The present invention relates to an apparatus for generating a code for cell searching, and more particularly, to a cell searching apparatus of an orthogonal frequency division multiplexing system and a method for constructing a cell searching code using the same.

The implementation of a cell searcher in a modulation / demodulation method using multiple carriers is mainly performed by obtaining a cell number and a cell group number through cross correlation using a cell search code. Conventional apparatus for generating code for cell search is a cell search apparatus and method of the patent application No. 10-1999-0015224 mobile communication system. This technique includes a base station group designation code predeterminer for preforming a base station group designation code of a slot time-synchronized synchronization channel, an operator for performing a cyclic shift operation based on the base station group designation code table based on the predetermined base station group code, A base station group designation code detector for detecting a code having a distance evaluation amount as a base station group designation code.

However, the related art relates to an apparatus and method for searching a cell of an asynchronous mobile communication system, and is not applicable to an orthogonal frequency division multiplexing system. In addition, such a method has a problem of degrading system performance by causing phase distortion because it is sensitive to the influence of timing offset and noise.

In order to solve the above problems, an object of the present invention is to provide a cell search apparatus for generating a code for cell search in an orthogonal frequency division multiplexing system and a method for constructing a cell search code using the same.

According to an aspect of the present invention, a cell search apparatus for generating a code for cell search in an orthogonal frequency division multiplexing system according to a feature of the present invention receives a radio signal input from a base station and performs cell search according to frame synchronization. A fast Fourier transform unit for fast Fourier transforming an Orthogonal Frequency Division Multiplexing (OFDM) symbol; A cell number determination unit determining cell number data through power measurement based on an output value of the fast Fourier transform unit; And a cell group number determination unit determining cell group number data through power measurement based on the determined cell number data.

According to an aspect of the present invention, a method for constructing a code for cell search in an orthogonal frequency division multiplexing system includes: Fast Fourier transforming the symbols; (b) determining cell number data by calculating power information based on the fast Fourier transformed output value according to a cell number code; And (c) separately extracting and synthesizing valid data from the determined cell number data to form a cell number continuous array.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

In addition, when a part is said to "include" a certain component, this means that it may further include other components, except to exclude other components unless otherwise stated.

Now, a cell search apparatus of an orthogonal frequency division multiplexing system and a cell search code configuration method using the same according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a diagram illustrating a frame structure of a conventional OFDMA system, and FIG. 2 is a diagram illustrating a structure of a CCP-P among the frame structures of the OFDMA system of FIG. 1.

As shown in FIG. 1, the frame structure of an OFDMA system includes a Cell Common Packet Preamble (CCP-P) 1 and data 1 '. And the data 1 'includes n DTPs 2. In addition, one frame is composed of a length of α ms and the portion except for the CCP-P (1) is a data part.

Each DTP 2 has a length of β ms, and each DTP 2 is composed of 10 OFDM symbols 3. One OFDM symbol 3 has a length of r ms. The OFDM symbol 3 repeatedly inserts a Cyclic Prefix (CP) 4 longer than a delay spread back and forth. As described above, the CP 4 is repeatedly inserted before and after the OFDM symbol 3 to remove intersymbol interference (ISI) and inter-channel interference (ICI), thereby protecting the guard. Role and autocorrelation operations to enable initial symbol timing to be estimated. In addition, the CP 4 may obtain a peak value through autocorrelation calculation using a moving average of 452 chips.

Next, referring to FIG. 2, the CCP-P 1 includes an S field 5, a C field 6, and an indicator resource space (IRS) 7. The S field 5, the C field 6, and the IRS 7 each have a length of r ms. Thus, CCP-P (1) occupies three OFDM symbols (3) long.

The S field 5 includes an S symbol 8 and an IS symbol 9. That is, the S symbol 8 is repeated four times and the IS symbol 9 is repeated once. The IS symbol 9 is a portion having the S symbol 8 in a 180 degree phase difference. That is, the IS symbol 9 is a phase shift of the S symbol 8 by 180 degrees. In this way, time synchronization and frequency synchronization can be efficiently performed, and frame detection and frequency offset can be estimated.

The C field 6 and the IRS 7 are used for fine frequency offset estimation, and the C field 6 inserts the CP 4 into the CN (Cell Number) and CGN (Cell Group Number) symbols and the CN and CGN symbols. It is configured.

Next, an apparatus for detecting a cell number and a cell group number in a next generation wireless communication modulation and demodulation system will be described in detail with reference to FIG. 3.

3 is a block diagram schematically showing an internal configuration of a cell search apparatus according to an embodiment of the present invention, and FIG. 4 is a block briefly showing an internal configuration of a cell number determination unit in a cell search apparatus according to an embodiment of the present invention. 5 is a block diagram schematically illustrating an internal configuration of a cell group number determination unit of a cell search apparatus according to an exemplary embodiment of the present invention.

For convenience of description, the present invention assumes that frame synchronization has already been obtained and performs only a cell search part.

The cell search apparatus according to an exemplary embodiment of the present invention includes a fast Fourier transform unit 100, a cell number determiner 110, and a cell group number determiner 120.

As shown in Fig. 2, in the C field 6 of the CCP-P 1, a cell number and a cell group number symbol, a cell number and a CP 4 are inserted.

The fast Fourier transform unit 100 removes the CP 4 of the C field 6 data when the C field 6 data of the CCP-P 1 is input in accordance with frame synchronization. In addition, the fast Fourier transform unit 100 receives a radio signal input from the base station and performs a fast Fourier transform on an Orthogonal Frequency Division Multiplexing (OFDM) symbol related to cell search in accordance with frame synchronization.

The fast Fourier transform unit 100 performs a fast Fourier transform on a frame received signal including a data subcarrier and a pilot subcarrier to convert the data received into a data symbol in a frequency domain.

The cell number determiner 110 includes a first power calculator 112, a first peak detector 114, and a cell number synthesizer 116.

The first power calculation unit 112 calculates power information according to each cell number data such as CN0, CN1, CN2, CN3, etc. received from the fast Fourier transform unit 100 to the first peak detection unit 114. send.

The first peak detector 114 detects a peak of power information of each cell number data and determines cell number data CN.

The cell number synthesizing unit 116 separately extracts and combines only valid data among the determined cell number data to form a cell number sequence (M-Sequence). Here, the cell number consecutive arrangements are referred to below with reference to (CN0 # 1, CN0 # 2 ...), (CN1 # 1, CN1 # 2 ...) and the like.

The cell group number determiner 120 according to an exemplary embodiment of the present invention includes a second power calculator 122, a preamble register unit 124, a cross correlator 126, and a second peak detector 128.

The second power calculator 122 calculates power information according to each cell number consecutive arrangement generated by the cell number determiner 110 to determine cell group number data (CGN).

The preamble register unit 124 transmits the pre-stored synchronization preamble code to the cross correlation unit 126.

The cross correlation unit 126 performs cross correlation between the received synchronization preamble and the transmitted synchronization preamble. That is, when the cross correlator 126 receives the cell group number data from the second power calculator 122, the cross correlation unit 126 performs cross correlation using the preamble code received from the preamble register unit 124.

The second peak detector 128 detects the peak of each cell group number data on which the cross correlation operation is performed to determine the final cell group number data.

The second peak detector 128 determines the portion where the peak occurs from the cross correlation unit 126 and then detects the frame start point. The second peak detector 128 compares the cross-correlation value with a predetermined threshold to determine whether a peak is generated.

The cell group number synthesizing unit 129 separately extracts and combines only valid data among the final cell group number data to form a cell group number continuous sequence (M-Sequence). Here, the cell group number consecutive arrangement will be described with reference to FIGS. 8 and 9 below.

FIG. 6 is a diagram illustrating a cell number sequence arrangement of CN0 according to an embodiment of the present invention, and FIG. 7 is a diagram showing a cell number sequence arrangement of CN1 according to an embodiment of the present invention.

In the cell number determining unit 110 according to the embodiment of the present invention, as shown in FIG. 4, data is filled only in the CN0 portion, and the remaining CN1, CN2, and the like are all filled with 0. The cell number data may be determined by calculating the power of the output data. As shown in Fig. 4, CN0 # 1, CN0 # 2, .., etc., in which data is present, are combined to form one final cell number data (cell number contiguous arrangement), and with this, a Cell Group Number: CGN).

In the cell number determination unit 110 according to the embodiment of the present invention, as shown in FIG. 5, data is filled only in the CN1 portion, and the remaining CN0, CN2 and the like are all filled with 0. The cell number data may be determined by calculating the power of the output data. As illustrated in FIG. 5, CN1 # 1, CN1 # 2, .., etc., in which data exists, are combined to form one final cell number data (cell number continuous array), and with this, a cell group number (Cell Group Number: CGN).

8 is a diagram illustrating a cell group number sequence array CGN0 consisting of CN0 and CN1 according to an embodiment of the present invention, and FIG. 9 is a diagram of a cell group number sequence array composed of CN3 and CN4 according to an embodiment of the present invention. ).

The cell group number determination unit 120 according to an embodiment of the present invention calculates the power of the final cell number data (cell number continuous arrangement) from the cell number determination unit 110 to determine the cell group number data. Then, when the cell group number data is determined, the final cell group number data is determined by performing cross-correlation operation on each cell group number data to detect peaks.

8 and 9 illustrate a new cell group number detection structure, in which only valid data of the final cell group number data is separately extracted and synthesized to form a cell group number continuous sequence (M-Sequence). FIG. 8 shows a cell group number sequential arrangement CGN0 consisting of CN0 and CN1 where data is present, and FIG. 9 shows a cell group number sequential arrangement CGN5 consisting of CN3 and CN4 where data exists.

10 is a flowchart illustrating a code configuration method for cell search using a cell search apparatus according to an embodiment of the present invention.

The fast Fourier transform unit 100 receives a radio signal input from a base station and performs fast Fourier transform on an Orthogonal Frequency Division Multiplexing (OFDM) symbol related to cell search in accordance with frame synchronization.

The first power calculator 112 calculates power information based on the cell number code of the output value of the fast Fourier transform unit 100 and transmits the power information to the first peak detector 114 (S100).

The first peak detector 114 detects a peak of power information of each cell number data and determines cell number data (CN) (S102).

The cell number synthesizing unit 116 extracts and combines valid data from the determined cell number data to form a cell number continuous array (S104).

The second power calculator 122 calculates power information based on the formed cell number continuous array to determine cell group number data (S106).

The cross correlator 126 performs cross correlation on the determined cell group number data and transmits it to the second peak detector 128.

The second peak detector 128 detects the peak of each cell group number data on which the cross correlation operation is performed and determines the final cell group number data (S108).

The cell group number synthesizing unit 129 extracts and combines valid data from the determined final cell group number data separately to form a cell group number continuous array (S110).

Although the embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements of those skilled in the art using the basic concepts of the present invention defined in the following claims are also provided. It belongs to the scope of rights.

According to the above-described configuration, the present invention can expect the effect of implementing an efficient cell search code that is less sensitive to timing offset in a modulation / modulation scheme using multiple carriers.

Claims (10)

delete delete delete delete delete delete delete A method for constructing a code for cell search in an orthogonal frequency division multiplexing system, (a) receiving a radio signal input from a base station and performing fast Fourier transform on an Orthogonal Frequency Division Multiplexing (OFDM) symbol related to cell search in accordance with frame synchronization; (b) determining cell number data by calculating power information based on the fast Fourier transformed output value according to a cell number code; (c) separately extracting and synthesizing valid data from the determined cell number data to form a cell number continuous array; (d) determining cell group number data by calculating power information based on the formed cell number consecutive arrangements; (e) performing cross-correlation operations on the determined cell group number data and detecting peaks to determine final cell group number data; And (f) extracting and synthesizing valid data separately from the determined final cell group number data to form a cell group number continuous array; Cell navigation code configuration method comprising a. delete The method of claim 8, Extracting cell number codes in which data exists among the determined cell number data and arranged at the same position to form the cell number continuous array; And Extracting the number of one or more cell number codes based on the cell number consecutive array to construct the cell group number continuous array Cell navigation code configuration method comprising a.

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