KR100657506B1 - Method for embodying downlink frame in wireless communication system using orthogonal frequency division multiple access method - Google Patents

Abstract

The present invention relates to a method for constructing a downlink frame for an OFDMA signaling scheme that can be used for designing a downlink frame structure in a mobile data communication system using an orthogonal frequency division multiple access (OFDMA) scheme. In order to configure this downlink frame, one preamble is placed in front of the downlink frame, and a plurality of data symbols are arranged after the preamble. Subsequently, a plurality of pilot symbols are inserted between the data symbols by repeating at regular intervals over the downlink frame. According to the present invention, it is possible to track fast channel changes using a preamble and a pilot symbol, and to minimize and equalize interference between adjacent cells, thereby facilitating the layout design of a plurality of cells with a frequency reuse ratio of 1. .

OFDMA, downlink, frame, preamble, pilot, symbol, channel estimation, mobile communication

Description

How to configure downlink frame in wireless communication system using PFDMA system {METHOD FOR EMBODYING DOWNLINK FRAME IN WIRELESS COMMUNICATION SYSTEM USING ORTHOGONAL FREQUENCY DIVISION MULTIPLE ACCESS METHOD}

1 is a diagram illustrating a downlink frame structure of a wireless communication system using an OFDMA scheme according to an embodiment of the present invention.

2 is a diagram illustrating a time domain form of a preamble of a downlink frame in a wireless communication system using an OFDMA scheme according to an embodiment of the present invention.

3 is a diagram illustrating allocating subcarriers for one slot period and one subchannel in a downlink frame of a wireless communication system using an OFDMA scheme according to an embodiment of the present invention.

4 is a diagram illustrating allocating resources given to two slots and four subchannels of a downlink frame in a wireless communication system using an OFDMA scheme according to an embodiment of the present invention.

5 is a diagram illustrating resource allocation in a downlink frame of a wireless communication system using an OFDMA scheme according to an embodiment of the present invention.

6 (a) and 6 (b) are diagrams illustrating performance of initial synchronization using a preamble of a downlink frame in a wireless communication system using an OFDMA scheme according to an embodiment of the present invention.

7 is a diagram illustrating channel estimation performance using a preamble of a downlink frame in a wireless communication system using an OFDMA scheme according to an embodiment of the present invention.

The present invention relates to a method for configuring a downlink frame of a mobile data communication system, and more particularly, to a downlink of a mobile data communication system using an orthogonal frequency division multiple access (OFDMA) scheme. Frame configuration method.

When a signal is transmitted through a multipath channel, the received signal generates inter-symbol interference ("ISI") by multipath. In particular, in high-speed data transmission, since the period of the symbol is smaller than the delay spread of the channel, the ISI becomes more severe, and a complicated reception technique is required to compensate for the distortion caused by the ISI and accurately recover the transmission signal.

Orthogonal frequency division multiplexing (hereinafter referred to as 'OFDM') has been proposed as a modulation scheme for compensating for distortion in such a multipath channel.

The basic concept of the OFDM scheme is to increase the data rate by converting serially input data streams into N parallel data streams and transmitting them on separate sub-carriers. In this case, the subcarriers should be appropriately selected to maintain orthogonality. Because of this orthogonality, since each subcarrier can be transmitted by overlapping at the same time, the symbol period in each subcarrier can be made longer by the number of subcarriers than when data is sequentially transmitted using one carrier.

As such, the OFDM scheme uses subcarriers having mutual orthogonality, and thus has better bandwidth efficiency than the conventional frequency division multiplexing (FDM) and has a longer symbol period. Thus, the OFDM scheme is stronger in ISI than the single carrier modulation scheme.

On the other hand, in broadband mobile communication systems, radio channels are frequency selective and time varying. This indicates that the channels in the OFDM system are not the same on both the frequency axis and the time axis. In addition, when using multiple transmit antennas, received symbols in each subcarrier are superimposed after the symbols transmitted from the multiple transmit antennas undergo fading independently. Therefore, in a mobile OFDM communication system using multiple transmit antennas, since the channel is frequency selective and time-varying, effective channel estimation is necessary before demodulating the OFDM symbol.

In such an OFDM system, channel estimation is typically performed by inserting a pilot into a subcarrier already known in the time and frequency axis grids.

Channel estimation in the OFDM scheme can be largely divided into pilot-symbol-aided (PSA) channel estimation and decision-directed (DD) channel estimation according to the type of data used for channel estimation. have. The PSA scheme is suitable for fast fading channels, where pilots are placed in consideration of the coherence bandwidth of the channel, the coherence time, and the reduction of bandwidth efficiency due to the use of pilot tones. The DD technique estimates the channel of the next symbol period using the detection data and is suitable for a slow fading channel having a fixed or time correlation.

On the other hand, when the OFDM transmission method is used for cellular mobile communication, wireless LAN, and wireless portable Internet, which is not for broadcasting, a multiple access method for multiple users is required like the single carrier transmission method. Representative methods of the multiple access method include TDMA, FDMA, and CDMA, and OFDM and these multiple access methods are used in combination.

The dual OFDM / TDMA / FDMA (OFDMA) scheme allows each user to use some subchannels and some OFDM symbols among all subchannels and OFDM symbols. Resource allocation can be efficiently performed by differently assigning the number and the number of OFDM symbols. In particular, the OFDMA method is advantageous when using a large FFT.

IEEE 802.16, which is a typical wireless data communication system standard adopting the OFDMA method, is for fixed data communication and does not support mobility of a terminal. IEEE 802.16e, which will be a mobile data communication system standard, is currently being standardized.

However, in the frame structure used in the IEEE 802.16e OFDMA mode, since the mobility of the terminal is only partially supported, channel estimation is performed using only the preamble. Therefore, although channel estimation is possible in a decision-directed manner for data signals transmitted after the preamble, the reliability thereof is very low compared to channel estimation using the preamble.

SUMMARY OF THE INVENTION The present invention has been made in an effort to solve such a problem, and to provide a method for configuring a downlink frame for an OFDMA communication system capable of highly reliable channel estimation.

The present invention also provides a method for constructing a downlink frame for an OFDMA communication system supporting a frequency reuse rate of 1 for mobile packet data communication in a mobile data communication system using an OFDMA method.

Method for configuring a downlink frame of a wireless communication system according to an aspect of the present invention for achieving the above object is

a) disposing a preamble in front of the downlink frame;

b) placing a plurality of data symbols after the preamble; And

c) inserting a pilot symbol between the data symbols throughout the downlink frame.

Here, the pilot symbols may be arranged between the data symbols at regular intervals.

The preamble may include a cyclic prefix and two identical patterns repeated in the time domain. In this case, the pilot symbol may use one of two identical patterns of CP and the preamble.

On the other hand, the downlink frame configuration method of the wireless communication system according to another aspect of the present invention

a) disposing one preamble at the front of the downlink frame;

b) placing a plurality of data symbols after the preamble; And

c) inserting a plurality of pilot symbols between the data symbols by repeating at regular intervals over the downlink frame.

The method may further include minimizing and equalizing interference between adjacent cell subchannels by defining a subchannel in a downlink period excluding the preamble, and the subchannel defining step includes:

i) defining a subchannel using a basic permutation for the downlink frame interval excluding the preamble; And

ii) changing the position of a physical subcarrier for each symbol period for the same subchannel and slot defined above.

Meanwhile, according to a method of operating a terminal using a downlink frame of the OFDMA method according to an aspect of the present invention, the downlink frame received by the terminal includes a preamble disposed at the front, a plurality of data symbols disposed after the preamble, And a pilot symbol disposed between the data symbols.

And, the terminal operating method using the downlink frame

Receiving the downlink frame;

Acquiring frame timing synchronization, symbol timing synchronization, and carrier frequency synchronization using the preamble of the received downlink frame, and performing automatic gain adjustment using the received preamble; And

Performing channel estimation using the received preamble or pilot symbol.

Meanwhile, the downlink frame structure of the OFDMA scheme according to the feature of the present invention is

A preamble disposed at the front;

A plurality of data symbols disposed after the preamble; And

It includes a pilot symbol disposed between the data symbols.

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. Like parts are designated by like reference numerals throughout the specification.

Hereinafter, an operation of a downlink frame structure and various utilization methods of a wireless communication system using an OFDMA scheme 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 downlink frame structure of a wireless communication system using an OFDMA scheme according to an embodiment of the present invention.

As shown in FIG. 1, the first OFDM symbol section of the downlink frame 7 is used for transmission of the preamble 1, and an integer number of data symbols are provided in the OFDM symbol section of the downlink frame section after the preamble 1. (3) are assigned.

A plurality of pilot symbols 5 are inserted between the data symbols 3 repeatedly at regular intervals throughout the downlink frame, wherein the pilot symbols are approximately one-half the OFDM symbol size.

In addition, according to an embodiment of the present invention, one or more OFDM symbols may be used for transmission of a control signal such as a common control channel between the preamble 1 and the data symbols 3 allocated for data transmission, if necessary.

According to an embodiment of the present invention, the preamble 1 transmitted to the first portion of the downlink 7 may be utilized for various purposes as follows by the receiver of the terminal receiving the downlink frame signal.

(1) Initial synchronization: includes frame timing synchronization, symbol timing synchronization, and carrier frequency synchronization.

(2) automatic gain adjustment

(3) Cell Search and Classification: Performed during initial cell search and cell search during handoff.

(4) channel estimation

Meanwhile, the pilot symbol according to the embodiment of the present invention is inserted between the data symbols 3 at regular intervals so that the receiver can estimate the distortion degree of the channel. The channel estimation result using the pilot symbol is combined with the channel estimation result using the preamble to track the channel change or obtain more reliable channel estimation. In an embodiment according to the present invention, one pilot symbol is inserted into three OFDM data symbols. The pilot symbols are used for channel estimation or channel change tracking. The shorter the period in which the pilot symbols are inserted, the faster the terminal mobility. Support. On the other hand, there is a disadvantage in that overhead caused by pilot symbols increases, so in actual system specification design, it is desirable to minimize the number of pilot symbols within the range in which the maximum serviceable terminal moving speed is supported.

2 is a diagram illustrating a time domain form of a preamble of a downlink frame in a wireless communication system using an OFDMA scheme according to an embodiment of the present invention.

As shown in FIG. 2, in the preamble according to the embodiment of the present invention, the same pattern p _c and 13 are repeated twice in the time domain, and a CP (cyclic prefix, 11) is added to the front of the preamble. And, the pilot symbol according to the embodiment of the present invention is the same as the signal from the beginning of the CP 11 to the end of the first pattern p _c (13) of the preamble signal shown in FIG.

According to an embodiment of the present invention, each length of the same pattern may have a length of 1024 samples. Frequency domain pattern P _{IDcell, s} [ k ], k = -N _FFT / 2, -N _FFT / 2 + 1, ..., N _FFT / 2-1 for generating the preamble signal and the pilot signal Is given by 1.

는 프리앰블 이후의 데이터 신호의 전송 전력에 대한 프리앰블 신호의 상대적인 전력에 해당하는 상수값으로 예를 들어

일 수 있으며,

은 총

개의 서로 다른 셀들을 구분하는 번호이며,

는 길이가

인 왈쉬(Walsh) 부호의 번호이며,

는 부반송파 번호를 나타내며, 신호 전송에 사용되는 유효 부반송파의 개수는 N _used 개며, 신호 전송에 사용하지 않는 널(null) 부반송파와 신호 전송에 사용하는 유효 부반송파를 포함한 전체 부반송파의 개수는

개다. here,

Is a constant value corresponding to the relative power of the preamble signal with respect to the transmission power of the data signal after the preamble.

Can be,

Silver gun

Number that distinguishes two different cells,

Has a length

Is the number of Walsh signs,

Denotes the subcarrier number, the number of effective subcarriers used for signal transmission is N _used , and the total number of subcarriers including null subcarriers not used for signal transmission and effective subcarriers used for signal transmission is

fold.

가 IFFT(Inverse Fast Fourier Transform) 처리되면, 시간 도메인에서 자체적으로 패턴이 반복되는 결과가 발생된다.Defined by Equation 1

Inverse Fast Fourier Transform (IFFT) processing results in a pattern repeating itself in the time domain.

는 수학식 2와 같이 주어지는 주파수 영역 프리앰블 패턴을 나타낸다.Also,

Denotes a frequency domain preamble pattern given by Equation 2.

는

비트 연산자를 의미하며,

는 0 또는 1의 값을 가지며 길이가

이고 번호가

인 Walsh 부호의

번째 부호 심벌 값을 나타내며,

는 0 또는 1의 값을 가지는 길이가

인 PN 부호의 k번째 부호 심벌 값을 나타낸다. 본 발명의 실시예에서 PN 부호는 PRBS(pseudo-random binary sequence)에 의해 생성되며, PRBS 다항식의 예로 X¹¹+X⁹+1이 있다. 그리고, 프리앰블 변조를 위한 PRBS의 초기 벡터의 예로는 [01010101010]이 있다. here

Is

Means a bitwise operator,

Has a value of 0 or 1 and has a length

And number

Of Walsh code

Represents the first sign symbol value,

Has a length of 0 or 1

Represents the k-th symbol value of the PN code. In an embodiment of the present invention, the PN code is generated by a pseudo-random binary sequence (PRBS). An example of the PRBS polynomial is X ¹¹ + X ⁹ +1. An example of an initial vector of PRBS for preamble modulation is [01010101010].

As described above, the preamble provided in the embodiment of the present invention is uniform in frequency interval pattern generated by the combination of the PN code and the Walsh code at two subcarrier intervals centering on the subcarriers corresponding to the center frequency to distinguish different cells. Is generated by OFDM modulation. Since the preamble signal transmits one of the signals of a predetermined pattern over one OFDM symbol period, the terminal receiving the preamble signal can obtain reliable information for the above-described purposes.

Meanwhile, subchannels and slots are defined for the remaining downlink frame intervals except for the preamble and used for resource allocation. The subchannel is a frequency domain allocation unit of a resource allocated to a common control signal or each data signal, and a slot is a time domain allocation unit. Subchannel allocation should be designed so that interference signals from neighboring cells are evenly distributed across multiple subchannels. In the embodiment of the present invention, for example, a total of 97 subchannel definition patterns are provided, the number of effective subcarriers is 1552, the slot is three OFDM symbol intervals excluding pilot symbols, and the size of the subchannel is defined in each OFDM symbol interval. Assume that 16 subcarriers (G ₀ to G ₁₅ ) are used for the above. An example of the result of the design for the above condition is shown in Equation 3.

은 부반송파 번호를 의미하는데, 구체적으로 하향 링크 프레임의 한 슬롯에 속하는

번째 OFDM 심벌 구간에 대한

번째 부채널의

번째 부반송파의 부반송파 번호를 의미하며, 한 슬롯에 속하는 총 1552 × 3 = 4656개의 부반송파에 대해 0~4655의 값으로 해당 부반송파를 가리킨다. 상기 수학식 3에서 n은 m/16보다 크지 않은 최대 정수이며,

는 슬롯 번호가 짝수인 경우에는 0, 홀수인 경우에는 48의 값을 가지는 부반송파 할당 오프셋(offset)이며,

는 수학식 4와 같이 주어지는 기본 순열을 s회 왼쪽으로 회전 쉬프트(cyclic shift) 시킨 것의

번째 원소를 가리킨다.here,

Means a subcarrier number, specifically, belonging to one slot of a downlink frame

For the first OFDM symbol interval

Of the first subchannel

It means the subcarrier number of the first subcarrier, and indicates the corresponding subcarrier with a value of 0 to 4655 for a total of 1552 × 3 = 4656 subcarriers belonging to one slot. In Equation 3, n is a maximum integer not greater than m / 16,

Is a subcarrier allocation offset having a value of 0 for even numbers and 48 for odd numbers.

Is the cyclic shift of the basic permutation given by Eq.

Point element.

Such a subcarrier allocation pattern minimizes and equalizes interference with a subcarrier allocation pattern for each subchannel of a different cell. That is, when one subchannel is selected from the total of 97 subchannels for two different cells, a set of 48 subcarriers belonging to the two subchannels overlap only one or more subcarriers during one slot period. This local interference is also averaged across the subchannels by error correcting codes, resulting in leveling of interference between cells and a frequency reuse rate of one.

3 is a diagram illustrating allocating subcarriers for one slot section and one subchannel in a downlink frame of a wireless communication system using an OFDMA scheme according to an embodiment of the present invention, and FIG. A diagram illustrating allocating resources given to two slots and four subchannels of a downlink frame in a wireless communication system using an OFDMA scheme according to an embodiment.

That is, FIG. 3 illustrates an example of allocating subcarriers according to the definition of the subchannel for one slot section in the time and subcarrier regions. FIG. 4 is a view illustrating the subchannels and slots defined as described above. An example of allocating time and frequency resources to a terminal or a terminal group is shown in the time and subchannel regions. The example of FIG. 4 shows a case in which resources having sizes of two slots in the time domain and four subchannels in the subchannel region are allocated.

Meanwhile, FIG. 5 is a diagram illustrating resource allocation in a downlink frame of a wireless communication system using an OFDMA scheme according to an embodiment of the present invention. FIG. 5 is a diagram illustrating each terminal or each terminal group over a downlink frame. The following shows an example of the result of resource allocation for transmitting data to a server. In the example of FIG. 5, preambles and pilot symbols are not represented in order to avoid confusion and express only logical control signals and traffic allocations.

In addition, the first part of the traffic period after the common control channel is used for transmission of frame and resource allocation information such as IEEE 802.16a and IEEE 802.16e, for example, DL-MAP, UL-MAP, and the other downlink frame period. All are used to transmit downlink data based on the allocation information delivered to each terminal by the DL-MAP.

Meanwhile, according to the embodiment of the present invention, the pilot symbol may be selectively used by the base station, and the terminal may identify the base station by transmitting whether the base station configures a frame using the pilot symbol on a common control channel.

Next, a preamble generation method, a pilot symbol generation method, a subchannel definition method, and a terminal operation method according to an embodiment of the present invention will be described.

According to an embodiment of the present invention, a preamble is generated by the following method.

First, the frequency domain pattern given by Equation 1 is modulated to generate a preamble in which the same pattern is repeated an integer number of times in the time domain. In the frequency domain pattern of the preamble, a PN code that can distinguish a plurality of cells is generated and used, and a preamble pattern group having a strong orthogonality is generated by additionally modulating a Walsh code.

The pilot symbol is generated in the following manner.

Pilot symbols are inserted at a predetermined number of OFDM symbol interval intervals, and the pilot symbols are composed of a CP and a repetitive pattern of the preamble. Subsequently, the channel estimation result using the pilot symbol is combined with the channel estimation result using the preamble to track the channel change, and the channel estimation result using the pilot symbol is combined with the cell search or channel estimation result using the preamble or the cell search or The reliability of the channel estimation result is improved.

In addition, according to an embodiment of the present invention, a subchannel definition method according to a time-varying channel may be given as follows.

In the downlink interval excluding the preamble, subchannels are defined using Equation 3 to minimize and equalize interference between adjacent cell subchannels. Then, the basic permutation using Equation 4 is used to change the position of the physical subcarriers for each symbol period for the same subchannel and slot for the defined subchannel.

Meanwhile, according to an embodiment of the present invention, a method of operating a terminal using a preamble and a pilot symbol of the downlink frame may be given as follows.

First, each terminal acquires frame timing synchronization, symbol timing synchronization, and carrier frequency synchronization using the received preamble, and then performs automatic gain adjustment using the received preamble. Each terminal performs channel estimation using the received preamble or pilot symbol.

A terminal newly accessing a wireless communication system or a terminal in a handoff process identifies and searches an optimal cell using the received preamble or pilot symbol. In addition, the terminal operating normally by accessing the system determines whether to handoff by identifying and measuring the preamble signals of the cell to which the cell belongs and the neighbor cells.

The following describes a simulation result for the initial synchronization and channel estimation method using a preamble and a pilot symbol according to an embodiment of the present invention.

6 (a) and 6 (b) are diagrams illustrating performance of initial synchronization using a preamble of a downlink frame in a wireless communication system using an OFDMA scheme according to an embodiment of the present invention.

Referring to Figure 6, AWGN, ITU-Ped-B and ITU-Veh-A models were used in this simulation. 6 (a) shows an accurate preamble detection probability. Automatic correlation of time domain replicas was used for preamble detection. The start point of the frame or initial FFT window is determined by the detection of the correct preamble. As shown, the preamble was detected with a high probability in a very low SNR range. Since the SINR at the cell / sector edge is very low (very less than 0 dB) under the condition that the frequency reuse rate is '1', the preamble according to the embodiment of the present invention sets the frequency reuse rate to '1' in the existing mobile communication system. It can be seen that it can be used.

6B is a diagram illustrating the performance of the initial frequency estimation after frame detection. The conjugate product of the time domain replica was used for frequency estimation. Due to the frequency domain allocation of the subcarriers of the preamble, the estimation range is set to [-1, 1] for the subcarrier space. By extending the range of estimation, the complexity of cell identification in the frequency domain is reduced. In addition, due to the length of the time domain replica, it shows stable estimation performance in spite of the relatively long delay spread of the fading channel. Simulation results show a very satisfactory estimation result in a very low SNR range. Since the SINR at the cell / sector edge is very low (very less than 0 dB) under the condition that the frequency reuse rate is '1', the preamble according to the embodiment of the present invention sets the frequency reuse rate to '1' in the existing mobile communication system. It can be seen that it can be used.

7 is a diagram illustrating channel estimation performance (packet error rate (PER)) using a preamble of a downlink frame in a wireless communication system using an OFDMA scheme according to an embodiment of the present invention.

It is assumed here that a periodic (every fourth) pilot symbol is inserted. The ITU-Veh-A model was used for this simulation. In the frequency domain, despreading of PN-Wash is used for noise cancellation. Time domain interpolation was used for symbols between pilot symbols. In order to verify cell edge performance under the condition of reuse rate '1', a low ratio (1/2 to 1/12) convolutional turbo code (CTC) and QPSK were used in this simulation. In this case, at the cell / sector edge under the condition of '1' of frequency reuse rate, the SINR is often lower than 0 dB. Simulation results show that cell / sector edge coverage is guaranteed by performing a low rate encoding using a preamble structure according to an embodiment of the present invention. If the sectors in the cell use a preamble with an orthogonal Walsh different from the PN, the interference between the sectors is reduced, resulting in improved channel estimation performance.

As described above, according to an embodiment of the present invention, a method of improving both channel estimation performance and terminal mobility support by inserting a pilot symbol having a higher reliability than a pilot tone using a predetermined period throughout the downlink frame is provided. can do.

In addition, the embodiment of the present invention provides a structure in which the frequency reuse rate is 1 by providing a design in which the interference between adjacent cell subchannels is minimized and averaged in the subchannel design, thereby maximizing efficiency of frequency resource utilization And high speed mobile data communication.

Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited thereto, and various other changes and modifications are possible.

According to the present invention, channel estimation performance can be improved for a wireless data communication system using OFDMA in a multiple access scheme, and efficiency of frequency resource utilization can be maximized.

Claims (25)

In the downlink frame configuration method of a wireless communication system, a) disposing a preamble in front of the downlink frame; b) placing a plurality of data symbols after the preamble; And c) inserting a pilot symbol between the data symbols throughout the downlink frame Including; The preamble includes two or more identical patterns repeated in the time domain, and the pilot symbol uses the same pattern of one of two or more identical patterns of the preamble. The method of claim 1, d) disposing one or more symbols for the common control channel between the preamble and the data symbols assigned for data transmission. The method of claim 1, And the size of the pilot symbol is approximately one half of the size of the data symbol. The method of claim 1, And the pilot symbols are arranged between the data symbols at regular intervals. The method of claim 4, wherein And the pilot symbol is inserted every three data symbols. The method of claim 1, The preamble includes a cyclic prefix (CP) and two identical patterns repeated in the time domain. The method of claim 6, And the pilot symbol uses one of two identical patterns of a CP and the preamble. The method of claim 6, The preamble is generated by uniformly arranging and modulating a frequency domain pattern generated by a combination of a PN code and a Walsh code at two subcarrier intervals around a subcarrier corresponding to a center frequency. How to configure link frame. The method of claim 1, The preamble is used for initial synchronization acquisition, cell classification, channel estimation and automatic gain adjustment. The method of claim 1, And the plurality of pilot symbols are used for channel estimation and channel change tracking. The method of claim 1, The preamble is Modulating the frequency domain pattern to generate a preamble in which the same pattern is repeated an integer number of times in the time domain; Modulating a PN code capable of distinguishing a plurality of cells into a frequency domain pattern of the preamble; And Generating a orthogonal preamble pattern group by modulating a Walsh code in addition to the PN code modulated to the frequency domain pattern of the preamble A downlink frame configuration method of a wireless communication system, characterized in that it is generated by performing. The method of claim 11, The frequency domain pattern (

) Is the relation

here,

Is a constant value corresponding to the relative power of the preamble signal to the transmit power of the data signal after the preamble,

Silver gun

Number that distinguishes two different cells,

Has a length

Is the number of the Walsh code,

Indicates the subcarrier number. The downlink frame configuration method of the wireless communication system, characterized in that follows. A method of configuring a downlink frame in a wireless communication system supporting mobility using an orthogonal frequency division multiple access (OFDMA) method, a) disposing one preamble at the front of the downlink frame; b) placing a plurality of data symbols after the preamble; And c) inserting a plurality of pilot symbols between the data symbols repeatedly at regular intervals over the downlink frame; Including; The preamble includes two or more identical patterns repeated in the time domain, and the pilot symbol uses the same pattern of one of two or more identical patterns of the preamble. The method of claim 13, d) disposing one or more symbols for the common control channel between the preamble and the data symbols assigned for data transmission. The method of claim 14, Defining a subchannel in a downlink period excluding the preamble to minimize and equalize interference between adjacent cell subchannels; The subchannel definition step, i) defining a subchannel using a basic permutation for the downlink frame interval excluding the preamble; And ii) changing the position of a physical subcarrier for each symbol period for the same subchannel and slot defined above Downlink frame configuration method of a wireless communication system comprising a. The method of claim 15, The subchannel is a relational expression

here,

Denotes the subcarrier number of the m th subcarrier of the s th subchannel for the n th OFDM symbol period belonging to one slot of the downlink frame,

Is a subcarrier allocation offset having a value of 0 for even numbers and 48 for odd numbers.

Denotes the jth element of the cyclic shift of the base permutation left by s times. The downlink frame configuration method of the wireless communication system, characterized in that defined by. The method according to claim 15 or 16, The basic permutation defining the subchannels is as follows.

The downlink frame configuration method of the wireless communication system, characterized in that follows. A method of operating a terminal using a downlink frame of an orthogonal frequency division multiple access (OFDMA) method, The downlink frame is A preamble including two or more identical patterns disposed at the front and repeated in the time domain, a plurality of data symbols disposed after the preamble, and the same pattern of one or more of the same patterns of the preamble disposed between the data symbols Includes a pilot symbol using, The terminal operation method Receiving the downlink frame; Acquiring frame timing synchronization, symbol timing synchronization, and carrier frequency synchronization using the preamble of the received downlink frame, and performing automatic gain adjustment using the received preamble; And And performing channel estimation using the received preamble or pilot symbol. The method of claim 18, And determining whether to handoff using the preamble or pilot symbol received from the cell to which the cell belongs and neighboring cells. In a downlink frame structure of Orthogonal Frequency Division Multiple Access (OFDMA) scheme, A preamble including two or more identical patterns disposed in front and repeated in the time domain; A plurality of data symbols disposed after the preamble; And And a pilot symbol disposed between the data symbols and using the same pattern of one or more of two or more identical patterns of the preamble. The method of claim 20, And the pilot symbol size is approximately one half of the data symbol size. The method of claim 20, And the pilot symbols are arranged between the data symbols at regular intervals. The method of claim 20, The preamble includes a cyclic prefix (CP) and two identical patterns repeated in the time domain. The method of claim 23, wherein The pilot symbol is a downlink frame structure of the OFDMA scheme, characterized in that using one of two patterns of the same pattern of the CP and the preamble. The method of claim 23, wherein The preamble is generated by uniformly arranging and modulating a frequency domain pattern generated by a combination of a PN code and a Walsh code at two subcarrier intervals around a subcarrier corresponding to a center frequency. Frame structure.

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