KR100895101B1 - Apparearus and method for synchronization channel transmission in wireless communication system - Google Patents

Abstract

The present invention relates to a method and apparatus for transmitting a synchronization channel in an OFDM cellular system. The present invention relates to a multiplexing synchronization channel signal including a plurality of primary synchronization channel signals and a secondary synchronization channel signal, and to be used when precoding the synchronization channel signal. After selecting a coding vector, the sync channel signal is multiplied with the precoding vector.

Synchronous Channel Transmission, OFDM Cellular System, Beamforming

Description

Method and apparatus for transmitting synchronization channel in mobile communication system {APPAREARUS AND METHOD FOR SYNCHRONIZATION CHANNEL TRANSMISSION IN WIRELESS COMMUNICATION SYSTEM}

The present invention relates to a method and apparatus for transmitting a sync channel, and more particularly, to a method and apparatus for transmitting a sync channel in an OFDM cellular system.

The synchronization channel of an OFDM cellular system is composed of a primary synchronization channel and a secondary synchronization channel, and the cell searcher of the terminal acquires synchronization using the primary synchronization channel and uses the same to frequency the secondary synchronization channel signal through a fast fourier transform (FFT). The cell group or cell number is found using the sub-channel signal in the frequency domain by converting to the domain.

Prior art that obtains diversity gain in a sync channel is called Frequency Switching Transmit Diversity (FSTD). FSTD is a method of transmitting two preambles from different antennas. At this time, the frequency used by each antenna is also different. That is, the two preambles are loaded on different frequencies and transmitted by different antennas.

However, the prior art has a disadvantage that the search time of the cell searcher of the terminal is long.

An object of the present invention is to provide a method and apparatus for transmitting a synchronization channel capable of reducing a cell search time of a terminal of a mobile communication system.

In order to achieve the above object, a synchronization channel transmission method of a mobile communication system according to an aspect of the present invention multiplexes a synchronization channel signal including a plurality of primary synchronization channel signals and a secondary synchronization channel signal and frees the synchronization channel signal. After selecting a precoding vector to be used for coding, the sync channel signal is multiplied with the precoding vector.

In order to achieve the above object, a synchronization channel transmission apparatus of a mobile communication system according to an aspect of the present invention is a synchronization channel signal multiplexer for multiplexing a synchronization channel signal including a plurality of primary and secondary synchronization channel signals, A precoding vector multiplexer for selecting a precoding vector to use when precoding a sync channel signal and a precoder for multiplying the sync channel signal with the precoding vector.

As described above, according to the present invention, two main sync channel signals are transmitted in different beams, and different precoder vectors are used for each frame to increase diversity gain, thereby reducing cell search time of the terminal.

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.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, without excluding other components unless specifically stated otherwise. In addition, the terms “… unit”, “… group” described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware or software or a combination of hardware and software.

A synchronization channel transmission method and apparatus in a mobile communication system according to an embodiment of the present invention will now be described in detail with reference to the accompanying drawings.

1 is a block diagram of a synchronization channel transmission apparatus of a base station according to an embodiment of the present invention. Although FIG. 1 illustrates a case in which a synchronization channel transmitting apparatus of a base station includes four antennas, the present invention can be applied to the case of using two antennas.

As shown in FIG. 1, the apparatus for transmitting synchronization channels according to an embodiment of the present invention includes a controller 110, a synchronization channel signal multiplexer 120, a precoding vector multiplexer 130, and a precoder. 140), a buffer 150, an Inverse Fast Fourier Transformer (IFFT) 160, a Radio Frequency (RF) transmitter 170, and an antenna 180.

The controller 110 generates a synchronization channel signal multiplexer control signal for determining a synchronization channel signal to be transmitted at a specific frequency and at a specific time and a precoding vector multiplexer control signal for selecting a precoding vector to be used for precoding. The sync channel signal multiplexer 120 multiplexes two main sync channel signals and one sub sync channel signal according to frequency (subcarrier) and time. The precoding vector multiplexer 130 selects a precoding vector to use when precoding a sync channel. The precoder 140 performs precoding by multiplying the sync channel signal by the precoding vector.

The buffer 150 stores the precoded sync channel signal and transmits it to the IFFT.

IFFT 160 converts the precoded sync channel signal into a transmission signal in the time domain through inverse fast Fourier transform. The RF transmitter 170 converts the transmission signal in the time domain into a radio frequency and transmits the same through the antenna 180.

Hereinafter, a synchronization channel transmission method in a mobile communication system according to an embodiment of the present invention will be described in detail with reference to FIGS. 2 to 4. 2 is a flowchart illustrating a synchronization channel transmission method of a mobile communication system according to an embodiment of the present invention.

The sync channel signal multiplexer 120 multiplexes two primary sync channel signals and one sub sync channel signal (S210). Although an embodiment of the present invention has been described in the case of transmitting two main synchronization channel signals, the present invention can be applied to both the case of transmitting a plurality of main synchronization channel signals.

3 is a diagram illustrating a precoding vector selected according to a structure of a frame and a method of selecting a first precoding vector according to an embodiment of the present invention. Although FIG. 3 illustrates a case of transmitting two sync channel signals per frame, the present invention can be applied regardless of the number of sync channel signals transmitted per frame.

The primary synchronization channel and the secondary synchronization channel may be frequency division multiplexed (FDM) or time division multiplexed (EDM). In the embodiment of the present invention, time division multiplexing will be described as an example.

As shown in FIG. 3, one frame is composed of several OFDM symbols, and a primary sync channel signal (P-SCH) and a secondary sync channel signal (S-SCH) are located in different OFDM symbols. Two primary sync channels are located at different frequencies in one OFDM symbol. That is, the 0 th main sync channel signal (P-SCH # 0) is located at two subcarrier intervals, and the 1 st main sync channel signal (P-SCH # 1) is located at a subcarrier where the 0 th main sync channel signal is not located. do.

The precoding vector multiplexer 130 selects a precoding vector to be used for precoding (S220). An embodiment of the present invention proposes a method of selecting two precoding vectors.

은 n 번째 주 동기 채널 신호 전송 시간에 i(i=0,1) 번째 주 동기 채널 신호를 프리코딩할 때 사용하는 프리코딩 벡터를 의미한다. 즉,

는 0번째 주 동 기 채널 전송 시간에 0번째 주 동기 채널 신호를 프리코딩할 때 사용하는 프리코딩 벡터이고,

는 0번째 주 동기 채널 전송 시간에 1번째 주 동기 채널 신호를 프리코딩할 때 사용하는 프리코딩 벡터이다. A first precoding vector selection method will be described with reference to FIG. 3. In Figure 3,

Denotes a precoding vector used when precoding the i (i = 0,1) th main synchronization channel signal at an nth main synchronization channel signal transmission time. In other words,

Is a precoding vector used to precode the 0 th main sync channel signal at the 0 th main sync channel transmission time,

Is a precoding vector used when precoding the first main sync channel signal at the 0 th main sync channel transmission time.

There are N precoding vectors used for precoding the 0th main sync channel signal and N precoding vectors used for precoding the 1st main sync channel signal.

As shown in FIG. 3, the first precoding vector selection method performs precoding with respect to the 0 th main sync channel signal and the 1 st main sync channel signal by changing N precoding vectors for each transmission channel signal transmission time. Select the precoding vector to use. When precoding the same main sync channel signal in one sync channel signal transmission time, the same precoding vector is used.

)와 1번째 주 동기 채널 신호를 프리코딩할 때 사용하는 프리코딩 벡터(

)는 서로 직교하거나 상관성이 작은 것을 사용한다. 또한, 탐색 시간을 더욱 단축시키기 위해서는 인접한 동기 채널 신호를 프리코딩할 때 사용하는 프리코딩 벡터도 서로 직교하거나 상관성이 작은 것을 사용한다. In order to increase the diversity gain, a precoding vector used to precode the 0 th main sync channel signal at one sync channel signal transmission time (

) And the precoding vector used to precode the first main sync channel signal (

) Uses orthogonal or less correlated ones. In order to further shorten the search time, precoding vectors used when precoding adjacent sync channel signals are also orthogonal to each other or have low correlation.

A second precoding vector selection method will be described with reference to FIG. 4. 4 is a diagram illustrating a precoding vector selected according to a structure of a frame and a method of selecting a second precoding vector according to an embodiment of the present invention.

4 illustrates N frames in which a synchronization channel signal is transmitted twice. Each sync channel signal includes two main sync channel signals (P-SCH # 0, P-SCH # 1) and one sub-sync channel signal (S-SCH).

As shown in FIG. 3, the second precoding vector selection method is a vector to be used for precoding while changing N precoding vectors every frame for the 0 th main sync channel signal and the 1 st main sync channel signal. Choose. That is, the first precoding vector selection method uses different precoding vectors when transmitting two sync channel signals in one frame, while the second precoding vector selection method uses the same precoding vector when transmitting two sync channel signals in one frame. Use

In this way, diversity gain cannot be obtained within one frame. However, in a frame in which the precoding vector used for the synchronization channel signal precoding matches the channel vector of the terminal, the signal-to-noise ratio of the synchronization channel signal in the terminal increases by the beamforming gain. This beamforming gain has an effect of reducing the search time in a terminal having a low signal-to-noise ratio.

Like the first precoding vector selection method, in order to increase diversity gain, two precoding vectors used in one sync channel signal transmission time use orthogonal or small correlation vectors, and in order to further shorten the search time, Adjacent frames use precoding vectors that are orthogonal or less correlated with each other.

Now, an example of setting the precoding vector according to the second precoding vector selection method will be described with reference to the table. Table 1 shows an example of setting a precoding vector according to the second precoding vector selection method when four antennas are used.

If a matrix having a precoding vector as a column vector is defined as a precoding matrix, the precoding matrix used in the embodiment of the present invention is as follows.

은 0번째 주 동기 채널 신호를 프리코딩할 때 사용하는 프리코딩 행렬이고,

는 1번째 주 동기 채널 신호를 프리코딩할 때 사용하는 프리코딩 행렬이다.

의 세 번째와 네 번째 열벡터는 모두 0인데, 이는 0번째 주 동기 채널 신호는 실제로 안테나 0번과 안테나 1번만을 통하여 전송된다는 것을 의미한다. From here

Is a precoding matrix used for precoding the 0th main sync channel signal,

Is a precoding matrix used for precoding the first main sync channel signal.

The third and fourth column vectors of are both zero, which means that the zeroth primary sync channel signal is actually transmitted only through antenna 0 and antenna 1.

]_j는 i 번째 프리코딩 행렬의 j 번째 열벡터를 의미한다. 표 1이 나타내는 바와 같이, 프레임 단위로 프리코딩 벡터가 바뀌고 있고, 하나의 프레임 내의 두 개의 프리코딩벡터는 직교하고, 인접한 프레임의 프리코딩 벡터는 직교한다. 즉, 프레임 0의 0번째 주 동기 채널 신호를 프리코딩할 때 사용하는 프리코딩 벡터([

]₀)와 프레임 0의 1번째 주 동기 채널 신호를 프리코딩할 때 사용하는 프리코딩 벡터([

]₀)은 직교하고, 프레임 0의 0번째 주 동기 채널 신호를 프리코딩할 때 사용하는 프리코딩 벡터([

]₀)와 프레임 1의 0번째 주 동기 채널 신호를 프리코딩할 때 사용하는 프리코딩 벡터([

]₁)는 직교한다. In Table 1

] _j is the j th column vector of the i th precoding matrix. As shown in Table 1, the precoding vector is changed in units of frames, two precoding vectors in one frame are orthogonal, and the precoding vectors of adjacent frames are orthogonal. That is, the precoding vector ([

₀ ) and the precoding vector ([

] ₀ is orthogonal, and the precoding vector ([

] ₀ ) and the precoding vector ([

₁ ) is orthogonal.

Frame 0 Frame 1 Frame 2 Frame 3 w ⁽⁰⁾ (0) w ⁽¹⁾ (0) w ⁽⁰⁾ (1) w ⁽¹⁾ (1) w ⁽⁰⁾ (2) w ⁽¹⁾ (2) w ⁽⁰⁾ (3) w ⁽¹⁾ (3) [P ⁽⁰⁾ ] ₀ [P ⁽¹⁾ ] ₀ [P ⁽⁰⁾ ] ₁ [P ⁽¹⁾ ] ₁ [P ⁽⁰⁾ ] ₂ [P ⁽¹⁾ ] ₂ [P ⁽⁰⁾ ] ₃ [P ⁽¹⁾ ] ₃

The precoder 140 performs precoding by multiplying the sync channel signal by the precoding vector (S230). The IFFT 160 converts the precoded sync channel signal into a transmission signal in the time domain through an inverse fast Fourier transform (S240). The RF transmitter 170 converts the analog transmission signal into a radio frequency and transmits it through the antenna 180 (S250).

Embodiments of the present invention are not implemented only through the above-described apparatus and / or method, but may be implemented through a program for realizing a function corresponding to the configuration of the embodiments of the present invention, a recording medium on which the program is recorded, and the like. Such implementations may be readily implemented by those skilled in the art from the description of the above-described embodiments.

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.

1 is a block diagram of a synchronization channel transmission apparatus of a base station according to an embodiment of the present invention.

2 is a flowchart illustrating a synchronization channel transmission method of a mobile communication system according to an embodiment of the present invention.

3 is a diagram illustrating a precoding vector selected according to a structure of a frame and a method of selecting a first precoding vector according to an embodiment of the present invention.

4 is a diagram illustrating a precoding vector selected according to a structure of a frame and a method of selecting a second precoding vector according to an embodiment of the present invention.

Claims (19)

Multiplexing a plurality of primary sync channel signals; And Multiplying the plurality of main sync channel signals by a different first plurality of precoding vectors, respectively, The multiplexing step, And positioning the plurality of main sync channel signals at different frequencies. The method of claim 1, And the first plurality of precoding vectors are orthogonal to each other. The method of claim 1, And the first plurality of precoding vectors are different from the second plurality of precoding vectors used when precoding the main sync channel signal at a previous sync channel signal transmission time. The method of claim 3, And the first plurality of precoding vectors and the second plurality of precoding vectors are orthogonal to each other. The method of claim 1, And the first plurality of precoding vectors are different from the third plurality of precoding vectors used when precoding the main sync channel signal in a previous frame. The method of claim 5, And the first plurality of precoding vectors and the third plurality of precoding vectors are orthogonal to each other. The method according to any one of claims 1 to 6, The multiplexing may include multiplexing the plurality of main sync channel signals and sub-sync channel signals. Precoding the sub-sync channel signal. The method of claim 7, wherein The multiplexing step, And a time division multiplexing (TDM) multiplexing the primary sync channel to which the plurality of primary sync channel signals are allocated and the sub sync channel to which the sub sync channel signal is allocated. delete The method according to any one of claims 1 to 6, Inverse Fourier transforming the output value of the multiplying step into a transmission signal in a time domain; And Transmitting the transmission signal in the time domain. In the synchronization channel transmission apparatus of the mobile communication system, A synchronization channel signal multiplexer for multiplexing a plurality of main synchronization channel signals; A precoding vector multiplexer for selecting different first plurality of precoding vectors to use when precoding the plurality of main sync channel signals; And A precoder to multiply the plurality of main synchronization channel signals by the first plurality of precoding vectors, The sync channel signal multiplexer places the plurality of main sync channel signals at different frequencies. The method of claim 11, And the first plurality of precoding vectors are orthogonal to each other. The method of claim 11, And the first plurality of precoding vectors are different from the second plurality of precoding vectors used when precoding the main sync channel signal at a previous sync channel signal transmission time. The method of claim 13, And the first plurality of precoding vectors and the second plurality of precoding vectors are orthogonal to each other. The method of claim 11, And the first plurality of precoding vectors are different from the third plurality of precoding vectors used when precoding the main sync channel signal in a previous frame. The method of claim 15, And the first plurality of precoding vectors and the third plurality of precoding vectors are orthogonal to each other. The method according to any one of claims 11 to 16, And a controller for generating a synchronization channel signal multiplexer control signal for determining the primary synchronization channel signal and a precoding vector multiplexer control signal for selecting the first plurality of precoding vectors. The method according to any one of claims 11 to 16, An inverse Fourier transformer which inversely transforms an output value of the precoder into a transmission signal in a time domain; And And a radio frequency transmitter for converting the transmission signal in the time domain into a radio frequency and transmitting the same through an antenna. The method according to any one of claims 11 to 16, The sync channel signal multiplexer, And a time division multiplexing (TDM) for multiplexing the primary sync channel to which the plurality of primary sync channel signals are allocated and the sub sync channel to which the sub sync channel signal is allocated.

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