KR101479776B1 - Method for performing cell search procedure in wireless communication system - Google Patents

Abstract

A method for performing a cell search process in a wireless communication system includes searching for a Primary-Synchronization Channel (P-SCH), receiving a Primary Synchronization Signal (PSS) through the P-SCH, And detecting an MBMS indicator indicating whether a dedicated MBMS (Multicast Broadcast Multimedia Service) is available. It is possible to indicate whether the dedicated MBMS is indicated by using the P-SCH or the S-SCH used in the initial cell search, and to know whether the dedicated MBMS is performed without additional complexity so that the cell search of the UE can be performed more efficiently .

Description

[0001] The present invention relates to a method for performing a cell search procedure in a wireless communication system,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to wireless communication, and more particularly, to a method for a UE to perform a cell search process.

A WCDMA (Wideband Code Division Multiple Access) system of the 3rd Generation Partnership Project (3GPP) uses a total of 512 long pseudo noise scrambling codes for distinguishing the base stations. The base stations use different long PN scrambling codes as the scrambling codes of the downlink channels.

When power is applied to the UE, the UE performs system synchronization of the initial cell and acquires a long PN scrambling code identifier of the initial cell. This is called a cell search process. Here, the initial cell is determined according to the location of the UE when the power is applied. Generally, the cell of the BS corresponding to the largest signal component among the signal components of the BS included in the downlink received signal of the UE do.

In the WCDMA system, 512 long PN scrambling codes are divided into 64 code groups in order to facilitate cell search, and a primary synchronization channel (P-SCH) and a secondary synchronization channel (S-SCH) ) In the downlink channel. The primary synchronization channel is used to allow the terminal to acquire slot synchronization, and the secondary synchronization channel is used to allow the terminal to acquire frame synchronization and scrambling code groups.

In general, a cell search is performed by performing an initial cell search that is performed initially after the UE is powered on, a non-initial cell search that performs a handover or a neighbor cell measurement, .

In the WCDMA system, the initial cell search method is largely a three-step method. Step 1 is a step in which the UE acquires slot synchronization using a Primary Synchronization Signal (PSS) transmitted through a P-SCH. In a WCDMA system, a frame includes 15 slots, and each base station transmits a PSS in a frame. Here, the same PSS is used for all 15 slots, and all base stations use the same PSS. The UE acquires slot synchronization using a matched filter for the PSS. In step 2, a long PN scrambling code group and frame synchronization are obtained using slot synchronization and SSS (Secondary Synchronization Signal) transmitted through the S-SCH. In step 3, a long PN scrambling code identifier corresponding to a long PN scrambling code used by the initial cell is detected using a common pilot channel code correlator based on the frame synchronization and the long PN scrambling code group . That is, since eight long PN scrambling codes are mapped to one long PN scrambling code group, the UE calculates the correlation value of each of eight long PN scrambling codes belonging to its code group, and based on the calculated result, And detects a long PN scrambling code identifier of the cell.

Meanwhile, a Multicast Broadcast Multimedia Service (MBMS) is a service in which a plurality of base stations transmit the same downlink signal in a Single Frequency Network (SFN) system. The MBMS may perform MBSFN (Multicast Broadcast Single Frequency Network) to obtain a SFN combining gain between cells. The SFN combining gain means that the same information is transmitted on a cell-by-cell basis to obtain a diversity gain without any special operation at the receiving end. When a plurality of base stations transmit the same signal, the same signals transmitted from multi-cells do not act as inter-cell interference but act as a self signal and multipath fading The frequency diversity gain and the macro diversity gain can be obtained. On the other hand, a unicast service is a service in which a terminal accesses a base station and transmits / receives data to / from the base station. Only a unicast service may be provided in a specific cell, an MBMS may be provided together with a unicast service, or only an MBMS may be provided. A service in which only MBMS is provided is called a dedicated MBMS (MBMS).

When searching for an initial cell, the UE does not know whether the service provided in the cell is unicast or dedicated MBMS. The base station transmits basic system configuration information through a physical broadcast channel (P-BCH). When whether the cell service is a dedicated MBMS service is transmitted through a physical broadcast channel, the UE performs blind decoding on unicast and dedicated MBMS in a physical broadcast channel to obtain service information of the system. This may degrade the performance of the system by delaying the initial cell search execution time of the terminal.

There is a need for a method in which a UE can more efficiently perform cell search in a wireless communication system in which a unicast service and an MBMS can coexist.

SUMMARY OF THE INVENTION The present invention provides a method for a UE to perform a cell search process in a wireless communication system.

A method for performing a cell search process in a wireless communication system according to an embodiment of the present invention includes searching for a Primary-Synchronization Channel (P-SCH), receiving a Primary Synchronization Signal (PSS) And detecting an MBMS indicator indicating whether a dedicated MBMS (Multicast Broadcast Multimedia Service) is available by obtaining a correlation value of the PSS.

A method for performing a cell search process in a wireless communication system according to another aspect of the present invention includes receiving a PSS through a P-SCH, receiving a PSS through a S-SCH using a channel estimated through the P- Receiving an SSS for synchronization and detecting an MBMS indicator indicating whether dedicated MBMS is represented by the phase modulation of the SSS.

A method for transmitting a downlink synchronization signal in a wireless communication system according to another aspect of the present invention includes transmitting a first PSS through a P-SCH and transmitting a second PSS through the P-SCH, , And the first PSS and the second PSS are conjugate symmetry relationships in which a correlation value is obtained by one operation.

It is possible to indicate whether the dedicated MBMS is indicated by using the P-SCH or the S-SCH used in the initial cell search, and to know whether the dedicated MBMS is performed without additional complexity so that the cell search of the UE can be performed more efficiently .

1 is a block diagram illustrating a wireless communication system. Wireless communication systems are widely deployed to provide various communication services such as voice, packet data, and the like.

Referring to FIG. 1, a wireless communication system includes a user equipment (UE) 10 and a base station (BS) 20. The terminal 10 may be fixed or mobile and may be referred to by other terms such as a mobile station (MS), a user terminal (UT), a subscriber station (SS), a wireless device, The base station 20 generally refers to a fixed station that communicates with the terminal 10 and may be referred to in other terms such as a Node-B, a Base Transceiver System (BTS), an Access Point Can be called. One base station 20 may have more than one cell.

Hereinafter, downlink refers to communication from the base station 20 to the terminal 10, and uplink refers to communication from the terminal 10 to the base station 20. In the downlink, the transmitter may be part of the base station 20, and the receiver may be part of the terminal 10. [ In the uplink, the transmitter may be part of the terminal 10, and the receiver may be part of the base station 20.

The wireless communication system may be an Orthogonal Frequency Division Multiplexing (OFDM) / Orthogonal Frequency Division Multiple Access (OFDMA) based system. OFDM uses multiple orthogonal subcarriers. OFDM utilizes the orthogonality property between IFFT (inverse fast Fourier transform) and FFT (fast Fourier transform). In the transmitter, data is transmitted by performing IFFT. The receiver performs an FFT on the received signal to recover the original data. The transmitter uses an IFFT to combine multiple subcarriers, and the receiver uses a corresponding FFT to separate multiple subcarriers.

2 shows an example of a radio frame structure. And a radio frame using a normal cyclic prefix (CP).

Referring to FIG. 2, a radio frame is composed of 10 subframes, and one subframe may include two slots. One slot may comprise a plurality of OFDM symbols in the time domain. The number of OFDM symbols included in one slot can be variously determined according to the CP structure. In a radio frame using a general CP size, one OFDM symbol may be included in one slot. In the 10ms radio frame, when the OFDM symbol is 2048 Ts, the general CP size may be 144 Ts (Ts = 1 / (15000 * 2048) sec).

The P-SCH (Primary Synchronization Channel) is located in the last OFDM symbol of the 0th slot and the 10th slot. The same PSS (Primary Synchronization Signal) is transmitted through the two P-SCHs. The P-SCH is used to obtain time domain synchronization and / or frequency domain synchronization such as OFDM symbol synchronization, slot synchronization, and the like. The Zadoff-Chu (ZC) sequence can be used as the PSS, and the wireless communication system has at least one PSS.

ZC sequences are orthogonal sequences of CAZAC one of (Constant Amplitude Zero Auto-Correlation) sequence, and N _ZC a positive integer length of the CAZAC sequence, compare the root index (root index) u in N _ZC (relatively) small number (prime) Speaking (u is a natural number of N or less N _{ZC ZC} and each other is a small number), k-th element (element) of the u-th CAZAC sequence can be expressed as shown in equation 1 (k = 0,1, ... , N _ZC -1).

The CAZAC sequence d (k) has the following three characteristics.

Equation (2) means that the CAZAC sequence is always 1 in size, and Equation (3) means that the auto correlation of the CAZAC sequence is represented by the Dirac-delta function. Where the autocorrelation is based on circular correlation. Equation (4) means that the cross correlation is always constant.

The S-SCH (Secondary Synchronization Channel) is located immediately before the last OFDM symbol of the 0th slot and the 10th slot. The S-SCH and the P-SCH may be located in contiguous OFDM symbols. Different secondary synchronization signals (SSS) are transmitted through the two S-SCHs. The S-SCH is used to obtain frame synchronization and / or cell CP configuration, i.e., usage information of a general CP or an extended CP. One S-SCH uses two SSSs. The m-sequence can be used in SSS. That is, one m-sequence is included in one S-SCH. For example, when one S-SCH includes 63 subcarriers, two m-sequences of length 31 are mapped to one S-SCH.

The m-sequence is one of the PN sequences, and the PN sequence is reproducible and has characteristics similar to a random sequence. The PN sequence has the following characteristics. (1) Repeat cycle is long enough. If the repetition period is infinitely long, it is a random sequence. (2) The number of 0's and 1's in one cycle is similar. (3) The run length 1 is 1/2, the 2 is 1/4, the 3 is 1/8, ... A run length is a sequence of numbers with the same sign. (4) Cross-correlation between each sequence in one period is very small. (5) The entire sequence can not be reproduced with a small sequence fragment. (6) Playback is possible by an appropriate playback algorithm. The PN-sequence includes an m-sequence, a Gold sequence, and a Kasami sequence. The m-sequence has, in addition to the above-mentioned characteristics, an additional characteristic of a side lobe of periodic auto-correlation of -1.

The P-SCH and the S-SCH are used to obtain physical-layer cell identities (ID). The physical layer cell ID can be represented by 168 physical layer cell ID groups and three physical layer IDs belonging thereto. That is, the total physical layer cell ID is 504, represented by a physical layer cell ID group having a range of 0 to 167 and a physical layer ID having a range of 0 to 2 included in each physical layer cell ID group. Three ZC sequence root indexes are used for the P-SCH, and 168 S-SCH indexes for the physical layer cell ID group can be used for the S-SCH.

The P-BCH (Physical-Broadcast Channel) is located in the 0th subframe in the radio frame. The P-BCH starts from the third OFDM symbol of the 0th subframe (starting from the 0th OFDM symbol) and occupies four OFDM symbols except for the P-SCH and the S-SCH. The P-BCH is used to obtain basic system configuration information of the base station. The P-BCH may have a period of 40 ms.

3 shows another example of the radio frame structure. A wireless frame using an extended CP (CP).

Referring to FIG. 3, six OFDM symbols are included in one slot of a radio frame using an extended CP, as compared with a radio frame using a general CP. When the OFDM symbol is 2048 Ts in the 10 ms radio frame, the size of the extended CP may be 512 Ts (Ts = 1 / (15000 * 2048) sec).

In the radio frame using the extended CP, the P-SCH is located in the last OFDM symbol of the 0th slot and the 10th slot, and the S-SCH is located in the immediately previous OFDM symbol in the 0th slot and the 10th slot. The P-BCH is located in the 0th subframe in the radio frame, and occupies 4 OFDM symbols excluding the P-SCH and the S-SCH starting from the 3rd OFDM symbol in the 0th subframe.

Fig. 4 shows another example of the radio frame structure. It is a radio frame for dedicated MBMS. Dedicated MBMS is a service that provides only MBMS, and the performance of P-BCH decoding is improved by SFN (single frequency network) combining because the P-BCHs transmitted in all the cells are the same.

Referring to FIG. 4, a radio frame for dedicated MBMS includes 10 subframes, one slot includes two slots, and one slot may include 3 OFDM symbols.

In a radio frame of a system providing a unicast service, a subcarrier has a spacing of 15 kHz and an effective OFDM symbol is 2048 Ts. In a radio frame for dedicated MBMS, a subcarrier has a space of 7.5 kHz and an effective OFDM symbol 4096 Ts (Ts = 1 / (15000 * 2048) sec). That is, the space of the subcarrier is reduced by half and the effective OFDM symbol is doubled. The size of the CP may be 1024 Ts which is twice the size of the expanded CP. Therefore, one OFDM symbol may be included in one slot in the 10ms radio frame for dedicated MBMS.

The P-SCH may be located in the last OFDM symbol of the 0th slot and the 10th slot, and the S-SCH may be located immediately before the last OFDM symbol of the 0th slot and the 10th slot. The P-BCH is not shown, but the P-BCH is located in the 0th subframe in the radio frame and may occupy at least one OFDM symbol except for the P-SCH and the S-SCH.

The structure of the above-described radio frame, i.e., a radio frame using a general CP, a radio frame using an extended CP, or a radio frame for a dedicated MBMS is merely an example, and the number of sub- The number of slots that can be varied may vary. The number or position of the OFDM symbols in which the P-SCH and the S-SCH are arranged in the slot is only an example, and may be variously changed depending on the system.

FIG. 5 shows an example of mapping a sequence to a P-SCH. FFT window size (size) Nf = 64.

Referring to FIG. 5, a ZC sequence having a length N _ZC = 63 is mapped to 64 subcarriers including DC subcarriers. The ZC sequence is mapped sequentially from the leftmost subcarrier so that the center element of the ZC sequence, here, the 31st element P (31), is mapped to the DC subcarrier. A NULL value is inserted in a subcarrier in which no sequence is mapped in the mapping section (-32 subcarriers in this case). The sequence P (31) mapped to the DC subcarrier is punctured.

Here, the left side and the right side refer to one side of the DC subcarrier for the sake of convenience, and the opposite side of the DC subcarrier is the right side, and the present invention is not limited to the illustrated position. The size of the FFT window of the P-SCH and the length of the ZC sequence can be variously determined, and thus the mapping method of the sequence can be variously changed. The ZC sequence may be mapped symmetrically around the DC subcarrier in the time domain.

<Dedicated MBMS indication in P-SCH>

Now, a method for indicating whether dedicated MBMS is performed in the P-SCH, which is a proposed scheme, will be described.

Suppose that in a P-SCH, a ZC sequence of length N _ZC = 63 is mapped to 64 subcarriers including DC subcarriers. A ZC sequence d (n) having a length N _ZC = 63, which is a PSS transmitted through a P-SCH, may be generated according to Equation (5).

Table 1 shows the raw index u indicating the physical layer ID in the physical layer cell ID group.

physical-layer ID Root index u 0 25 One 29 2 34

When three PSSs are used in a wireless communication system, the base station selects one of the three PSSs and transmits the selected PSS on the last OFDM symbol of the 0th slot and the 10th slot.

In the proposed method, one PSS is added and one system information is represented by the added PSS. Simply adding an arbitrary PSS through the P-SCH increases the number of PSS estimations that the terminal must perform, thereby increasing the processing complexity of the terminal and degrading the performance of the system. Therefore, in the proposed scheme, a PSS used in the P-SCH is added, but a new PSS having a conjugate symmetry relationship is added to the defined PSS. This can be applied to both a radio frame using a general CP, a radio frame using an extended CP, and a radio frame for a dedicated MBMS, and it can be applied only to time domain synchronization and / or frequency domain synchronization using a PSS having a symmetric symmetric relationship. MBMS or not.

Applying two primitive indices satisfying u ₁ + u ₂ = N _ZC for the ZC sequence primitive index, the ZC sequence is expressed as Equation (6).

Any results for u ₁ and u ₂ (correlation output) have a computational complexity that is similar to the correlation value of a u _1, it is possible to calculate the correlation results for u ₁ and u ₂ for time synchronization with a single operation. Thus, two PSSs satisfying u ₁ + u ₂ = N _ZC are _referred to as a junction symmetry relationship. Or a PSS that can calculate the correlation result for u ₁ and u ₂ in one operation is called a conjugate symmetry relationship.

On the other hand, the junction symmetry relation of the PSS is maintained not only in the frequency domain but also in the time domain. Therefore, the PSS can be mapped not only in the frequency domain but also in the time domain.

Suppose that the ZC sequence in the case where N _ZC is an odd number is mapped in the time domain in the same manner as in FIG. Assuming that the time domain signal at this time is a ^u (k), the value of the intermediate buffer for calculating the final correlation value is defined as Equation (7).

Here, r (n) represents a received signal, d represents a delay index, and I and Q represent an in-phase and a quadrature-phase of a complex signal.

The final correlation result of u ₁ and u ₂ is expressed as Equation (8).

The junction symmetry relationship of the PSS can be maintained in the time domain as well as the frequency domain.

29 and 34 among the primitive indices 25, 29 and 34 used in the PSS for the ZC sequence having the length N _ZC = 63 as shown in Equation 5 satisfy the condition 29 + 34 = 63, so that the correlation value of u = 29 and u = Can be calculated at once. That is, if a primitive index satisfying u ₁ + u ₂ = N _ZC is defined for the primitive index used in the PSS, the terminal can transmit new control information without increasing the amount of computation.

In the PSS in Table 1, u = 38 satisfying the joint symmetry relation at u = 25 can be defined as an indicator for indicating whether dedicated MBMS is used. The UE can indicate whether it is a dedicated MBMS service without increasing the amount of computation.

Table 2 shows an example of a raw index of a ZC sequence used in the P-SCH according to the proposed scheme.

physical-layer ID Root index u 0 25 One 29 2 34 dedicated MBMS indicator 38

In the above description, the original index u = 38 of the added ZC sequence satisfying the joint symmetry relation at u = 25 is used as an indicator for indicating whether the MBMS is dedicated. However, this is only an example, and the original index of the added ZC sequence is And may be used to indicate various system information provided to the UE through the P-SCH. Also, when increasing the number of primitive indexes of the ZC sequence used in the P-SCH, it is possible to represent various control information by defining the primitive indexes of the ZC sequence satisfying the symmetric symmetry relation according to the proposed method.

6 shows an example in which two SSSs are physically mapped to the S-SCH.

Referring to FIG. 6, assume that two sequences of length N = 31 are mapped to 63 subcarriers including a DC subcarrier in the S-SCH. The logical representation represents the SSS used and the physical representation represents the sub-carrier to which the SSS is mapped when the SSS is transmitted on the S-SCH. S1 (n) is the nth entity of the first SSS (SSS1) and S2 (n) is the nth entity of the second SSS (SSS2). The first SSS (SSS1) and the second SSS (SSS2) are interleaved with each other and mapped to physical subcarriers in a concatenated manner. This method is called distributed mapping.

Meanwhile, the first SSS and the second SSS may not be interleaved but may be locally densified and mapped to physical subcarriers. This approach is called localized mapping.

Equation (9) represents a sequence for the SSS mapped to the S-SCH.

Here, s _x ^(m) (n) is a SSS, c _x ⁽ⁿ⁾ is a PSS based scrambling code, z _x ^(m) (n) is a segment based scrambling code ). The SSS is scrambled with two scrambling codes.

Equation (10) represents a generating polynomial of an m-sequence for generating SSS, PSS-based scrambling code and segment-based scrambling code.

The SSS, PSS-based scrambling code and segment-based scrambling code use a cyclic shift version of the sequence generated from the generator polynomial of the m-sequence.

&Lt; Dedicated MBMS indication in S-SCH >

Hereinafter, a method for indicating whether dedicated MBMS is performed via the S-SCH will be described.

FIG. 7 shows an example of mapping an SSS to an S-SCH in order to indicate whether dedicated MBMS service is available.

Referring to FIG. 7, the phase of the SSS can be phase-modulated in the S-SCH and the dedicated MBMS can be indicated in the phase modulation of the S-SCH. Phase modulation means modulating an M-PSK (Phase Shift Key) symbol in a signal mapped to a subcarrier in a frequency domain or a time domain. For example, 1-bit information can be added using BPSK (Binary Phase Shift Key) symbols, and 2-bit information can be added using QPSK (Quadrature Phase Shift Key) symbols. The M-PSK modulation is a method of loading additional information without affecting the detection performance of the sequence. M-PSK can be 8-PSK, 16-PSK, and the like, and there is no limit. The phase modulation of the SSS may be performed on the SSS of the logical expression or on the SSS of the physical representation.

Suppose that the first SSS (SSS1) and the second SSS (SSS2) are mapped to the S-SCH in a distributed mapping manner. At this time, it is possible to indicate whether dedicated MBMS is performed using BPSK symbols. If it is a dedicated MBMS, -1 can be modulated on the S-SCH, and if it is not a dedicated MBMS, +1 on the S-SCH. Or if it is a dedicated MBMS, +1 on the S-SCH, and if it is not a dedicated MBMS, -1 on the S-SCH. (+ SSS1, + SSS2) signal is transmitted in the S-SCH modulated by +1 and the S-SCH modulated in -1 is transmitted in the S-SCH to which the first SSS and the second SSS are mapped (SSS1, SSS2) SCH signals (-SSS1, -SSS2) are transmitted.

Although only one S-SCH is shown here, it is possible to modulate -1 or +1 for both the first S-SCH and the second S-SCH of the radio frame, or for only one of the first S-SCH and the second S-SCH -1 or +1 can be modulated. The M-PSK symbol may be modulated only in one of the first SSS and the second SSS to indicate control information other than the dedicated MBMS. For example, signals (+ SSS1, -SSS2), (-SSS1, + SSS2) signals, etc. may be transmitted through the S-SCH and this may mean another control signal.

In general, a cell search is performed by performing an initial cell search that is performed initially after the UE is powered on, a non-initial cell search that performs a handover or a neighbor cell measurement, . The initial cell search will be described below by way of example, but the technical idea of the present invention can be applied to a non-initial cell search as it is.

In the cell search, a downlink channel called P-SCH and S-SCH is used. The P-SCH is used to allow the terminal to acquire slot synchronization and / or frequency synchronization, and the S-SCH is used to allow the terminal to acquire frame synchronization and physical layer cell ID groups.

8 is a flowchart illustrating a cell search method according to an embodiment of the present invention.

Referring to FIG. 8, the terminal searches for a P-SCH (S110). The UE acquires slot synchronization or symbol synchronization through the P-SCH. In addition, frequency synchronization can be obtained through the P-SCH. When power is applied to the terminal, the terminal must detect the system synchronization of the initial cell and the unique physical layer cell ID of the cell. The initial cell is determined according to the SINR (Signal-to-Interference plus Noise Ratio) of the UE at the time when the power is applied. Generally, the initial cell is the largest signal among the signal components of each base station included in the downlink received signal Means a cell of a base station corresponding to a signal component.

When the dedicated MBMS indicator is transmitted through the P-SCH, the UE can detect the dedicated MBMS indicator through the P-SCH. The UE can calculate the correlation values of two PSSs having a symmetric symmetric relationship at a time in the P-SCH. For example, in Table 2, the UE calculates a correlation value of u = 25 or u = 38 to know whether a dedicated MBMS indicator is present. The UE can calculate the correlation value of two PSSs having a symmetric symmetric relationship by a single calculation, and can detect the dedicated MBMS indicator together with the PSS indicating the physical layer ID without increasing the amount of calculation. When the dedicated MBMS indicator is detected, the UE can use the MBMS according to the defined dedicated MBMS radio frame.

Then, the terminal searches for the S-SCH (S120). The terminal acquires frame synchronization through the S-SCH. The UE acquires cell ID information using the S-SCH's SSS and the P-SCH's PSS. Also, the terminal can obtain the antenna setting and other information.

When the dedicated MBMS indicator is transmitted through the S-SCH, the UE can detect the dedicated MBMS indicator through the S-SCH. The MS estimates the channel using the PSS transmitted through the P-SCH, compensates the estimated channel to the S-SCH, and detects the SSS. When the SSS is detected, the UE can detect the MBMS indicator with only the modulated phase component, and no additional detection process is required. That is, the UE can detect the SSS in the case where the SSS is phase-modulated or not, or can recognize the dedicated MBMS.

All of the functions described above may be performed by a processor such as a microprocessor, a controller, a microcontroller, an application specific integrated circuit (ASIC), etc. according to software or program code or the like coded to perform the function. The design, development and implementation of the above code will be apparent to those skilled in the art based on the description of the present invention.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those skilled in the art that various changes and modifications may be made therein without departing from the spirit and scope of the invention. You will understand. Therefore, it is intended that the present invention covers all embodiments falling within the scope of the following claims, rather than being limited to the above-described embodiments.

1 is a block diagram illustrating a wireless communication system.

2 shows an example of a radio frame structure. And a radio frame using a normal cyclic prefix (CP).

3 shows another example of the radio frame structure. A wireless frame using an extended CP (CP).

Fig. 4 shows another example of the radio frame structure. It is a radio frame for dedicated MBMS.

FIG. 5 shows an example of mapping a sequence to a P-SCH. FFT window size (size) Nf = 64.

6 shows an example in which two SSSs are physically mapped to the S-SCH.

FIG. 7 shows an example of mapping an SSS to an S-SCH in order to indicate whether dedicated MBMS service is available.

8 is a flowchart illustrating a cell search method according to an embodiment of the present invention.

Claims (8)

A method for performing a cell search procedure in a wireless communication system, Searching for a Primary-Synchronization Channel (P-SCH); And And receiving a Primary Synchronization Signal (PSS) via the P-SCH, When the length of the ZC sequence is NZC, the PSS is a ZC (Zadoff-Zhu) sequence and a method (NZC) which is one of two ZC sequences corresponding to the raw indexes u ₁ and u ₂ satisfying u ₁ + u ₂ = NZC Are positive integers, and u ₁ and u ₂ are natural numbers smaller than NZC, which is relative prime to the NZC. The method according to claim 1, And detecting an MBMS indicator indicating whether a dedicated MBMS (Multicast Broadcast Multimedia Service) is available by obtaining a correlation value of the received PSS. The method of claim 2 wherein the other non-MBMS service indicator of the two ZC sequences corresponding to the root index u ₁ and u ₂ is characterized in that the sequence for instructing the physical layer ID. The method of claim 1, further comprising receiving an SSS (Secondary Synchronization Signal) for frame synchronization through a Secondary-Synchronization Channel (S-SCH). A method for performing a cell search procedure in a wireless communication system, Receiving a PSS over a P-SCH; And And receiving an SSS for frame synchronization through an S-SCH using a channel estimated through the P-SCH, The PSS is one of two ZC sequences corresponding to the original indexes u ₁ and u ₂ satisfying u ₁ + u ₂ = NZC when the ZC sequence is a ZC (Zadoff-Zhu) sequence and the length of the ZC sequence is NZC (NZC is a positive integer, and u ₁ and u ₂ are natural numbers smaller than NZC, which is relative prime to the NZC). 6. The method of claim 5, Detecting an MBMS indicator indicating whether a dedicated MBMS is represented by phase modulation of the received SSS. 7. The method of claim 6, wherein two different sequences are used from the S-SCH to the SSS, and the phase of the two sequences is modulated to indicate the MBMS indicator. A method for transmitting a downlink synchronization signal in a wireless communication system, Transmitting a first PSS over a P-SCH; And And transmitting a second PSS over the P-SCH, The first PSS and the second PSS have a conjugate symmetry relationship in which correlation values are obtained by one operation, Wherein the first PSS is a ZC (Zadoff-Zhu) sequence indicating a physical layer ID, and when the length of the ZC sequence is NZC, the first PSS corresponds to the raw indexes u ₁ and u ₂ satisfying u ₁ + u ₂ = NZC (The NZC is a positive integer and u ₁ and u ₂ are natural numbers smaller than NZC, which are relative prime to each other in the NZC), which is one of the two ZC sequences.

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