KR100859716B1 - Cell search method for OFDM based FDD/TDD dual mode mobile station and base station transmission scheme - Google Patents

Abstract

In order to solve the above technical problem, the present invention relates to a method for transmitting a forward synchronization signal. The method for transmitting a forward synchronization signal in a wireless communication system includes the steps of: generating a frame composed of a plurality of sync blocks; And transmitting on a forward link, the frame including a first sync channel sequence providing sync block timing information and a plurality of second sync channel sequences providing frame timing information; A cell identifier is specified by the plurality of second synchronization channel sequences, and the time division duplex and frequency division duplex system divides the first synchronization channel sequence and the plurality of second synchronization channel sequences. It is characterized by using both, dual in FDD and TDD mode The complexity of the mode mobile station is significantly reduced.

OFDM, sync channel, cell search, FDD / TDD

Description

Cell search method for OFDM based FDD / TDD dual mode mobile station and base station transmission scheme in ODF-based FD and TDD dual mode UEs

The present invention relates to an OFDM cellular system, and more particularly, to a method for searching for an initial cell and an adjacent cell in an OFDM cellular system, and a mobile station, a base station, a system, and a frame structure using the same.

The present invention is derived from the research conducted as part of the IT new growth engine core technology development project of the Ministry of Information and Communication and the Ministry of Information and Communication Research and Development. [Task Management Number: 2005-S-404-12, Title: 3G Evolution Wireless Transmission Technology Development] ].

In the 3GPP WCDMA scheme, a total of 512 long PN scrambling codes are used in the system to distinguish base stations of a forward link, and neighboring base stations use different long PN scrambling codes as scrambling codes of forward link channels. When power is applied to the mobile station, the mobile station must obtain the system timing of the base station to which the mobile station belongs (the base station with the largest received signal) and the long PN scrambling code ID (or simply referred to as cell identifier) used by the current base station. This is called a cell search process of the mobile station.

In WCDMA, 512 long scrambling codes are divided into 64 groups and have a primary sync channel and a secondary sync channel on the forward link to facilitate cell search. The primary synchronization channel causes the mobile station to acquire slot synchronization and the secondary synchronization channel causes the mobile station to acquire 10 msec frame boundary and long PN scrambling code group ID information.

The cell search method of the WCDMA method is largely composed of three steps. The first step is a step in which a mobile station acquires slot synchronization using a primary synchronization channel code (PSC). In WCDMA, the same PSC is transmitted in units of 15 slots every 10 msec, and the PSCs transmitted by all base stations are the same signal. In step 1, slot synchronization is obtained by using a matched filter for the PSC.

In the second step, the long PN scrambling code group information and the 10 msec frame boundary are obtained by using the slot timing information and the secondary scrambling code (SSC) obtained in the first step.

In step 3, a long PN scrambling code ID currently used by a base station is obtained using a common pilot channel code correlator by using the 10 msec frame boundary and the long PN scrambling code group information obtained in the previous step. That is, since eight scrambling codes are mapped to one code group, in step 3, the mobile station compares the eight PN scrambling code correlator outputs and detects the long PN scrambling code ID used by the current cell.

In the WCDMA scheme, a synchronization channel basically consists of a primary synchronization channel and a secondary synchronization channel, and the primary synchronization channel and the secondary synchronization channel, the common pilot channel, and other data channels are CDMA based on time-domain direct sequence spreading. Multiplexing is done in a manner.

Currently, in 3GPP, OFDM-based wireless transmission technology specification is in full swing as part of 3G Long Term Evolution (3G-LTE) to compensate for the shortcomings of WCDMA. The synchronization channel and common pilot channel structure used in the WCDMA and the cell search method of the mobile station are suitable for DS-CDMA and cannot be applied to the OFDM forward link. Accordingly, in a cellular system using OFDM, a synchronization channel and common pilot channel structure of a forward link, an initial cell search method of a mobile station, and a neighbor cell search method for handover are required.

In the OFDM-based TDD and FDD dual mode terminals, we propose a cell search method for minimizing receiver complexity and a forward link sync channel transmission method in each base station system of FDD and TDD.

In order to solve the above technical problem, the forward sync signal transmission method proposed by the present invention includes the steps of: generating a frame composed of a plurality of sync blocks in a forward sync signal transmission method in a wireless communication system; And transmitting through the frame, wherein the frame includes a first sync channel sequence providing sync block timing information and a plurality of second sync channel sequences providing frame timing information, and the first sync channel sequence and the plurality of sync channel sequences. A cell identifier is specified by a second sync channel sequence, and the first sync channel sequence and the plurality of second sync channel sequences are used in both a time division duplex and a frequency division duplex system. It is characterized by.

In the TDD / FDD wireless communication system, the first sync channel sequence is repeatedly arranged in the same position on the sync block in the frame.

In addition, the number of first sync channel subcarriers for allocating the first sync channel sequence for each TDD / FDD wireless communication system is the same within the frame.

Further, in the TDD wireless communication system, the first sync channel sequence and the second sync channel sequence may be arranged in a time division multiplexing (TDM) scheme in an adjacent symbol interval in the frame.

In the FDD wireless communication system, the first sync channel sequence and the second sync channel sequence may be arranged in a frequency division multiplexing (FDM) scheme in the same symbol period in the frame.

Further, in the TDD / FDD wireless communication system, the second sync channel sequence is different for each cell and is different for each second sync channel symbol period in a frame even in the same cell.

In order to solve the above technical problem, the present invention provides a method for detecting a cell identifier using a forward synchronization signal in a TDD / FDD dual mode terminal, and a method for detecting a cell identifier using a forward synchronization signal in a TDD / FDD dual mode terminal in a wireless communication system. The method includes: receiving a frame composed of a plurality of sync blocks and having a sync channel sequence arranged in a TDM scheme or an FDM scheme, wherein the first sync channel is obtained in consideration of a scheme in which a sync channel sequence is arranged in the frame; And extracting sync block timing and frame timing information from the sequence and the plurality of second sync channels, and detecting a cell identifier through a combination of the first sync channel sequence and the plurality of second sync channel sequences.

In addition, when the sync channel sequence is arranged in the FDM scheme in the frame, the same first sync channel sequence is extracted for each sync block from the mapping in the frequency domain, and when the sync channel sequence is arranged in the TDM scheme in the frame, the sync block The same first synchronous channel sequence is extracted for each time from the one mapped in the time domain.

The sync block timing may be extracted using a time domain waveform of the first sync channel sequence.

The frame timing information may be extracted using one second sync channel sequence in a second sync channel symbol period within a frame in the plurality of second sync channel sequences.

In order to solve the above technical problem, the forward link frame proposed by the present invention is a first link for providing sync block timing information in a forward link frame including a plurality of sync blocks used as a forward sync signal in a wireless communication system. A plurality of second sync channel sequences providing channel sequence and frame timing information, wherein the cell identifier is specified by the first sync channel sequence and the plurality of second sync channel sequences; The plurality of second synchronization channel sequences may be used in both a time division duplex and a frequency division duplex system.

In the TDD / FDD system, the first sync channel sequence may be repeatedly arranged at the same position on the sync block in the frame.

In addition, in the TDD system, the first sync channel sequence and the second sync channel sequence may be arranged in a time division multiplexing (TDM) manner in an adjacent symbol interval in the frame.

In the FDD system, the first sync channel sequence and the second sync channel sequence may be arranged in a frequency division multiplexing (FDM) scheme in the same symbol period in the frame.

Further, in the TDD / FDD wireless communication system, the second sync channel sequence is different for each cell and is different for each second sync channel symbol period in a frame even in the same cell.

As described above, the present invention significantly reduces the complexity of the dual mode mobile station in the FDD and TDD modes in the OFDM cellular system.

In addition, it is possible to implement a cell searcher that operates both FDD mode and TDD with low complexity.

In addition, the synchronization acquisition method of the present invention enables synchronization acquisition with low complexity.

Hereinafter, with reference to the accompanying drawings will be described in detail a preferred embodiment of the present invention.

Each base station of an OFDM cellular system generally scrambles an OFDM symbol using a long pseudo noise scrambling code, but may use a different kind of scrambling code in addition to the long pseudo noise scrambling code. In the following description, it is called a scrambling code.

A base station according to an embodiment of the present invention includes a method including a plurality of transmission antennas, a time switching diversity (TSTD), a precoding vector switching transmission diversity, or a frequency switching transmission diversity (FSTD). The transmission diversity may be performed by a method, and in the drawings of the present specification, a base station having two transmission antennas is described for convenience.

In addition, the mobile station according to an embodiment of the present invention may perform reception diversity by a method including a plurality of reception antennas, and in the drawings of the present specification, a mobile station having two reception antennas is described for convenience. .

In the case of a mobile station having such a structure, data of each data path according to reception diversity should be combined. In the present specification, a simple summation is used in the present specification, but the present invention is not limited thereto. It is obvious to those who do it.

The present invention relates to a method for cell searching including synchronization acquisition, frame boundary detection, and cell identifier detection (also called scrambling code detection) in an OFDM cellular system.

“Sink block detection” is used herein to mean the detection of sync block boundaries 141 and 1141, and the meaning of detecting the sync block means OFDM symbol synchronization, the position of the first synchronization channel in the sink block, and the second synchronization. This means that the position of the channel is also detected.

In addition, "frame boundary detection" will be used herein to refer to detecting timings 140 and 1140 of the frame boundary, and "frame boundary information" is a term encompassing information on the timing of the frame boundary. Will be used.

The term "scrambling code detection" will be used herein in terms of scrambling code identifier detection and scrambling code detection, and the term "scrambling code information" will be used herein in terms of scrambling code identifiers and scrambling code.

In the present invention, "first sync channel sequence" means a set of first sync channel "chips" mapped to a subcarrier occupied by a first sync channel symbol in a frequency domain.

In the present invention, "second sync channel sequence" means a set of second sync channel "chips" mapped to a subcarrier occupied by a second sync channel symbol in a frequency domain.

In this specification, for convenience, the term Fourier transform is used as a term encompassing a Discrete Fourier Transform and a Fast Fourier Transform.

1 is a view showing the structure of a forward link frame in an FDD wireless communication system according to an embodiment of the present invention. Referring to FIG. 1, each of the forward link frames has a duration of 10 msec and consists of 20 subframes 110.

In Figure 1, the horizontal axis is the time axis and the vertical axis is the frequency (OFDM subcarrier) axis.

Each subframe is 0.5 msec long and includes seven OFDM symbols 120. In the example of FIG. 1, one sync channel OFDM symbol 100-A exists in every five subframes, and thus, four sync channel symbols 100-A, 100-B, 100-C, and 100 are included in one frame (10 msec). -D) exists.

In this case, the repetition period 130 of the synchronization channel symbol is equal to the sum of five subframes, and the number of repetition periods of the total synchronization channel symbols in one frame is four. For convenience, the repetition period of the synchronization channel symbol is called a sync block.

That is, FIG. 1 illustrates that the number of sync blocks 130 in one frame (10 msec) is four. As shown in the example of FIG. 1, when the first sync channel and the second sync channel are combined by the FDM scheme, it is easier to use the channel estimate of the first sync channel when coherent demodulation of the second sync channel.

For the remaining OFDM symbols except for the sync channel symbol part, a cell-specific scrambling code is multiplied in the frequency domain to distinguish each cell.

2 is a diagram illustrating a subframe including a sync channel symbol in downlink of an FDD wireless communication system according to an embodiment of the present invention. An example is subframe 4 of the first sync block of FIG. 1. As shown in the figure, the first sync channel and the second sync channel are combined in an FDM scheme.

According to the subframe illustrated in FIG. 2, the traffic data subcarrier (resource) 170, the first sync channel subcarrier (chip) 180, and the second in the OFDM symbol period 100 -A in which the sync channel symbol is transmitted. A synchronization channel subcarrier (chip) 181 and a null carrier 190 are included, and optionally a DC subcarrier may be included.

The other OFDM symbol 115 includes a traffic data subcarrier 170 or a pilot subcarrier.

As described above, the last OFDM symbol in the subframe is the synchronization channel OFDM symbol 100-A in which the first synchronization channel and the second synchronization channel are composed of FDM.

The example of FIG. 2 is merely an example, and the symbol position of the sync channel may be located at another symbol in the sync block 130.

Importantly, in all sync blocks in which a sync channel exists, the symbol positions of the sync channel are the same.

As a method of allocating a sync channel occupying band, the sync channel may occupy the remaining bands except the guard band, but only a part of the remaining bands may occupy the sync channel.

An example of a system to which the latter method can be applied is a system that must support scalable bandwidth, such as a 3G-LTE system.

That is, in order for all mobile stations using only 1.25 MHz, mobile stations using 2.5 MHz, and all mobile stations using 5 MHz, 10 MHz, 15 MHz, 20 MHz, etc. to acquire synchronization of the base station system, as shown in FIG. Each channel symbol occupies only a portion of the total system bandwidth 160.

For example, when the system bandwidth is 10 MHz, only 1.25 MHz in the center of the circuit except for the DC subcarrier is used.

Meanwhile, as will be described later, the cell searcher of the mobile station can improve cell search performance by performing filtering to pass only the sync channel occupation band 150.

In FIG. 2, the first sync channel and the second sync channel occupy only a part of the band 150 in the entire band 160 as described above.

As illustrated in FIG. 2, the first synchronization channel uses only one of two adjacent subcarriers, and the other one is used by the second synchronization channel.

3 is a view showing the structure of a downlink frame of a TDD wireless communication system according to an embodiment of the present invention. Referring to FIG. 3, each of the forward link frames has a duration of 10 msec and consists of 20 subframes 1110.

3, the horizontal axis is the time axis and the vertical axis is the frequency (OFDM subcarrier) axis.

Each subframe is 0.5 msec long and includes seven OFDM symbols 1120. In the example of FIG. 3, one first sync channel OFDM symbol 1100 -A and second sync channel OFDM symbol 1101-A exist in every 10 subframes, so that a total of two first syncs are performed in one frame (10 msec). There is a channel symbol and two second sync channel symbols.

In this case, the repetition period 1130 of the synchronization channel symbol is equal to the length of 10 subframes, and the number of repetition periods of the total synchronization channel symbols in one frame is two. For convenience, the repetition period of the synchronization channel symbol is called a sync block.

That is, FIG. 3 illustrates that the number of sync blocks 1130 in one frame 110 msec is two. As shown in the example of FIG. 3, when the first sync channel and the second sync channel are combined in a TDM scheme, the channel estimation value of the first sync channel can be used to coherently demodulate the second sync channel. It should be placed in an adjacent area.

For the remaining OFDM symbols except for the sync channel symbol portion, a cell-specific scrambling code is multiplied in the frequency domain to distinguish each cell. In the TDD mode, some of the 20 subframes of FIG. 3 are used as downlinks and some are used as uplinks. Importantly, the subframe including the sync channel must be used for downlink.

4 is a diagram illustrating a subframe including a sync channel symbol in a TDD wireless communication system according to an embodiment of the present invention.

An example is subframe 9 of the first sync block of FIG. 3. As can be seen from the figure, the first sync channel and the second sync channel are configured in a TDM scheme.

The reason why the first synchronization channel and the second synchronization channel are used as the TDM in the TDD wireless communication system as shown in FIG. 3 is that when using the FDM scheme as shown in FIG. This is because a constraint is placed on the non-downward switch point.

According to the subframe disclosed in FIG. 4, the traffic data subcarrier 1170, the first sync channel subcarrier 1180, and the null carrier 1190 are included in the OFDM symbol period 1100 -A through which the first sync channel symbol is transmitted. The OFDM symbol period 1101 -A through which the second sync channel symbol is transmitted includes a traffic data subcarrier 1170, a second sync channel subcarrier 1181, and a null carrier 1190.

The other OFDM symbol 1115 includes a traffic data subcarrier 1170 or a pilot subcarrier.

As described above, the last two OFDM symbols in the subframe are the first sync channel symbol and the second sync channel symbol, respectively. The example of FIG. 2 is merely an example and the symbol position of the sync channel may be located in another symbol in the sync block 1130. Importantly, the sync channel positions are the same in all sync blocks in which sync channels exist.

5 and 6 are diagrams illustrating a frequency mapping form of a synchronization channel in an FDD mode and a TDD mode, respectively, according to an embodiment of the present invention, wherein the number of first synchronization channel subcarriers in a synchronization channel symbol of an FDD mode and FIG. It can be seen that the number and positions of the first sync channel subcarriers in the first sync channel symbol in the TDD mode are the same.

By doing so, the time domain waveforms of the first synchronization channel in the FDD and TDD systems are the same. Therefore, since the mobile station can perform correlation using the same time domain waveform in the FDD mode and the TDD mode in the cell search step 1, the complexity of the terminal can be reduced.

5 and 6, the total number of subcarriers allocated to the second sync channel symbol per frame is approximately equal to 152 and 150, respectively, of FDD and TDD.

Therefore, the same second sync channel sequence set may be used for FDD and TDD. For example, in case of using an extended GCL sequence having a code length of 157, the same sequence is used for the second sync channel subcarrier 181 in the FDD, and only 150 out of the total length 157 in the case of the FDD.

In this case, since the frequency domain correlation may be performed using the same second synchronization channel sequence in the FDD mode and the TDD mode in the cell search step 2, the complexity of the terminal may be reduced.

According to an embodiment of the present invention, the forward link frame may be configured to allocate the first sync channel sequence and the second sync channel sequence allocated to the base station to the first sync channel in the FDM and TDM structures, respectively, as in the example of FIG. 5 or 6. To a subcarrier assigned to a subcarrier and a second sync channel. A component mapped to each of the synchronization channel subcarriers is defined as a "chip."

The length of the sequence of the first sync channel is equal to the number of subcarriers allocated to the first sync channel in one sync channel symbol (37 in the example of FIGS. 5 and 6) and is repeated in every sync channel symbol period. The length of the second sync channel sequence is equal to the total number of frequency domain subcarriers (152 and 150 in the example of FIGS. 5 and 6) of the second sync channel allocated to the plurality of sync channel symbols in the frame. It is done.

As a result, the period of the first synchronization channel sequence is the sync blocks 130 and 1130, and the period of the second synchronization channel sequence is one frame.

Using this structure, the mobile station acquires sync block synchronization using a time domain signal corresponding to the first sync channel sequence in cell search step 1, and in the cell search step 2, the mobile station obtains sync block synchronization based on the sync block synchronization obtained in step 1. The cell identifier and the frame boundary are obtained using the 2 sync channel sequence.

That is, the first sync channel sequence transmitted by any cell for every sync channel symbol can be expressed by Equation 1 below.

In Equation 1, each element of the first sync channel sequence is defined as a "chip" of the first sync channel sequence.

In Equation 1, N ₁ is the number of subcarriers (37 in the example of FIG. 4) allocated to the first sync channel sequence in one sync channel symbol.

In the case of the first sync channel, the same first sync channel sequence is transmitted in every symbol.

The reason for this is that the first sync channel sequence uses the same sequence for every sync channel symbol so that the receiver uses one correlator when the correlator using the time domain waveform of the first sync channel sequence is used in the first cell search. This is for obtaining a sync block boundary.

In addition, all cells used in the system are based on using one same sync channel sequence as the first sync channel sequence, but in some cases, a small number (eg, 8 or less) may be used.

In the present invention, a case where the number of first sync channel sequences used in the system is one will be described as an example.

Any code sequence having good correlation characteristics may be used as the first sync channel sequence, but a generalized chirp like (GCL) sequence may be used as an example.

Meanwhile, the second sync channel sequence may correspond one-to-one with a cell identifier or a cell identifier group. In the present invention, a case where the second sync channel sequence and a cell identifier correspond one-to-one will be described.

The second sync channel sequence has a one-to-one correspondence with the cell identifier and also provides information on a frame boundary to the mobile station. That is, the mobile station obtaining the sync block boundary 141 using the first sync channel detects the cell identifier using the second sync channel and simultaneously detects the frame boundary 140.

To do this, the length of the second sync channel sequence is equal to the total number of subcarriers allocated to the second sync channel in the frame (152 in FIG. 4).

As a result, the second sync channel sequence is represented by Equation 2 below.

는 시퀀스 번호가 k(또는 셀 식별자 번호가 k)인 제2 동기채널 시퀀스의 n 번째 칩이다.In other words,

Is the nth chip of the second sync channel sequence whose sequence number is k (or cell identifier number k).

In Equation 1, P is the number of second sync channels in the frame (4 in the example of FIGS. 1 and 4), and N ₂ is the number of second sync channel subcarriers allocated to the sync channel symbol. to be. As a result, the length of the second sync channel sequence becomes PxN ₂ .

The second sync channel sequence is characterized in that the same sequence is transmitted every frame for a signal transmitted by a base station apparatus of one cell, and different sync channel sequences are used for each cell.

That is, the cell base station of the present invention is assigned a second sync channel sequence mapped to a cell unique cell identifier or cell identifier group, and each chip of the allocated sync channel sequence is assigned to each subcarrier belonging to the sync channel occupation band. This is loaded.

로 표현되고, 두 번째 동기채널 심볼에 대한 부분 시퀀스는

로 표현되는데, 이들 부분 시퀀스는 모두 다름을 특징으로 한다.Subsequences of the respective sync channel symbols of the second sync channel sequence, that is, the partial sequence for the first sync channel symbol in the frame in FIG.

The subsequence for the second sync channel symbol is

These subsequences are all characterized by differentiation.

Therefore, even if the mobile station uses only one second sync channel among the P sync channel symbols in the frame, the frame boundary and the cell identifier or the scrambling code identifier can be detected in the cell search step 2.

This feature enables cell searching of 3G-LTE during handover from GSM to 3G-LTE. That is, the transmission gap of GSM is 4.6 msec. In the worst case, only one sync channel symbol may enter during this period.

In this case, when using the method of the present invention having the structure as shown in FIG. 1, it is possible to acquire sync block synchronization, frame boundary acquisition, and cell identifier acquisition.

As the second sync channel sequence, an arbitrary sequence having good cross-correlation property may be used. For example, an extended GCL sequence extending an GCL sequence may be used to increase the number of sequences.

1 and 3, the cell searcher of the present invention obtains a sync block boundary by using a correlator using a time domain waveform of a primary sync channel sequence in step 1 and searches for a cell. In step 2, a synchronization channel sequence number, that is, a cell identifier, is acquired using a secondary synchronization channel sequence correlator, and at the same time, a 10 msec frame boundary is also acquired. Coherent correlation using channel estimates using the primary synchronization channel may be performed to improve performance when performing secondary synchronization channel correlation. Details will be described later.

In order to improve performance when performing the second synchronization channel correlation, coherent correlation using the channel estimate using the first synchronization channel may be performed. Details will be described later.

The number of the second sync channel sequence used in the system is less than or equal to the number of scrambling codes used in the system.

If the number of second sync channel sequences used in the system is equal to the number of scrambling codes used in the system, the second sync channel sequence number corresponds one-to-one with the scrambling code number (or cell identifier).

If the number of the second sync channel sequence is smaller than the number of scrambling codes, the second sync channel sequence number corresponds to the scrambling code group number. In this case, three more cell searches are required.

That is, in step 2 of cell searching, only frame boundary and scrambling code group information are acquired, and in step 3, one of possible scrambling code numbers in the group must be found.

Step 3 is performed using a parallel domain correlator in the frequency domain for the common pilot signal of the forward link.

However, in the present invention, a case where the number of sync channel sequences and the number of scrambling codes are the same will be described as an example. In this case, since the frame boundary and the scrambling code identifier are detected in the cell search step 2, the cell search step 3 is unnecessary.

5 is a block diagram showing the configuration of a base station according to an embodiment of the present invention. Referring to FIG. 5, the synchronization channel generator 400, the traffic channel and pilot generator 402, the diversity controller 403, the OFDM symbol mapping units 404-A, 404-B, and the scrambling unit 405- A, 405-B), inverse Fourier transform units 406-A, 406-B, CP insertion units 407-A, 407-B, IF / RF units 408-A, 408-B and transmit antennas (409-A, 409-B).

The traffic channel and pilot channel generator 402 generates traffic data or pilot data to be transmitted, and the sync channel generator 400 is the same as Equation 1 and Equation 240 and 250 of FIG. 2 or 4. A first sync channel sequence and a second sync channel sequence defined by Equation 2 are generated.

The OFDM symbol mapping units 404-A and 404-B map data values of respective channels to respective positions on the frequency / time domain as in the example of FIG. 2 or 4.

The scrambling units 405-A and 405-B output the OFDM symbol mapping units 404-A and 404-B, that is, a unique scrambling code for each base station on the frequency domain for OFDM symbols other than sync channel symbols in the mapping result. Multiply by

The inverse Fourier transform units 406-A and 406-B inversely Fourier transform the output of the scrambling units 405-A and 405-B to generate a time domain signal.

CP inserters 407-A and 407-B insert a cyclic prefix to the output of the inverse Fourier transforms 406-A and 406-B to enable demodulation of the OFDM signal even in the multipath delay of the channel. do.

The IF / RF units 408-A and 408-B up-convert the output signals of the CP insertion units 407-A and 407-B, which are baseband signals, to a band pass signal. Amplify the signal.

Transmission antennas 409-A and 409-B transmit the amplified signals.

In the example of FIG. 7, it can be seen that there are two transmission antennas 409-A and 409-B. That is, if the base station according to an embodiment of the present invention has only one transmission antenna 409-A without the transmission antenna 409-B, the OFDM symbol mapping unit 404-B and the scrambling unit 405-B ), The inverse Fourier transform unit 406-B, the CP insertion unit 407-B, the IF / RF unit 408-B, and the diversity control unit 403 can be omitted.

In FIG. 7, a transmission channel symbol is transmitted in transmission diversity using two transmission antennas to a transmitting end of a base station system.

Transmitting diversity through the diversity control unit 403 illustrated in FIG. 5 will now be described. In order to achieve spatial diversity, sync channel symbols belonging to adjacent sync blocks are transmitted to different antennas.

For example, sync channel symbols in the first and third sync blocks are sent to the first transmit antenna 409-A, and sync channel symbols in the second and fourth sync blocks are sent to the second transmit antenna 409-B. It is.

The diversity control unit 403 performs the switching for performing the above-mentioned diversity. That is, as a method of applying Time Switching Transmit Diversity (TSTD) to a synchronization channel, the diversity controller 403 switches the output of the synchronization channel generator 400 so that the OFDM symbol mapping unit 404-. A) or to the OFDM symbol mapping unit 404-B.

In addition to the above-described spatial diversity or TSTD diversity, the present invention may be applied as a precoding vector switching transmission diversity.

Precoding vector switching is a precoding vector for two transmit antennas, for example, after setting a precoding vector as shown in Equation 3 below, the sync channel symbol in the first sync block is transmitted using the first precoding vector. The sync channel symbol in the second sync block is the second precoding vector, the sync channel symbol in the third sync block is the third precoding vector, and the sync channel symbol in the fourth sync block is the fourth precoding vector. How to send.

In the above equation, the first element of the precoding vector is the weight for the first antenna and the second element is the weight for the second antenna.

When the precoding vector switching diversity is applied, the diversity control unit 403 switches the precoding vector by the diversity control unit 403 to switch the OFDM symbol mapping unit 404-A or the OFDM symbol mapping unit 404-B. To provide.

In addition to the TSTD and precoding vector switching, frequency switching transmit diversity (FSTD) may be applied.

In this case, the sequence element mapped to the even subcarrier among the first-carrier subcarriers assigned to the sync channel symbol is transmitted to the first antenna and the sequence element mapped to the odd subcarrier is transmitted to the second antenna. The sequence element mapped to the even-numbered subcarrier among the formulation 2 sync channel subcarriers is the first antenna, and the sequence element mapped to the odd-numbered subcarrier is transmitted to the second antenna.

In this case, the diversity control unit 403 also plays a role. In the case of TDD, the same diversity technique can be applied.

8 is a block diagram showing the configuration of a receiver of a mobile station according to an embodiment of the present invention. The mobile station has at least one receiving antenna, and FIG. 8 is an exemplary diagram of the case of two receiving antennas.

Referring to FIG. 8, a receiver of a mobile station according to an embodiment of the present invention includes a receiving antenna 500 -A and 500 -B, a down converter 510 -A and 510 -B, and a cell searching unit. 600, a data channel demodulator 520, a controller 530, and a clock generator 540.

Frames in the form of RF signals transmitted from each base station are received through the receiving antennas 500-A and 500-B, and then the baseband signals S1 and S2 through the down-converters 510-A and 510-B. Is converted to).

The cell search unit 600 searches for a target cell by using the synchronization channel symbols included in the down-converted signals S1 and S2.

Examples of cell search results include detecting sync channel symbol timing, frame boundaries, and cell identifiers of a target cell. Examples of searching for a target cell include a case where a mobile station initially searches for an initial cell, or a handover. For example, searching adjacent cells.

The controller 530 controls the cell search unit 600 and the data channel demodulator 520.

That is, the controller 530 controls timing, inverse scrambling, and the like of the data channel demodulator 520 based on the cell search result obtained by controlling the cell searcher 600.

The data channel demodulator 520 demodulates the traffic channel data included in the down-converted signal under the control of the controller 530.

Meanwhile, all hardware of the mobile station is operated in synchronization with the clock generated by the clock generator 540.

The cell searcher 600 is divided into sync channel band filter units 610 -A and 610 -B, sync block sync detector 620, and code & boundary detector 640.

The sync channel band filter units 610-A and 610-B may use the downlink-converted signals S1 and S2 as shown in FIGS. 2 and 4 as shown in FIGS. 2 and 4. Band pass filtering that passes only 150 is performed.

The sync block synchronization detector 620 obtains the sync block timing S5 using the first sync channel symbol included in the filtered signals S3 and S4.

The code & boundary detection unit 640 detects a cell identifier and 10 msec frame timing information from the received signal by using the acquired sync block timing information S5.

Meanwhile, the code & boundary detector 640 may increase the detection performance by performing frequency offset estimation and compensation before detecting the cell identifier and the frame timing.

9 is a block diagram illustrating a configuration of the synchronization acquisition unit 620 of FIG. 8 according to an exemplary embodiment of the present invention. Referring to FIG. 9, the synchronization acquisition unit 620 includes a correlation unit 621 -A and 621 -B, a signal combiner 622, an accumulator 623, and a timing detector 624.

In the example of FIG. 9, the mobile station receiver may store the time domain waveform of the first sync channel sequence represented by Equation 1 in advance and perform a correlation in the time domain.

The outputs of the correlators 621 -A and 621 -B are accumulated in the accumulator 623 via the signal combiner 622.

Referring to the example of the FDD frame structure of FIG. 1, the outputs of the correlators 621 -A and 621 -B are each generated 4800 per sync block length, and the timing detector 624 determines the peak value among these correlation values. The position of the sample generating the peak value) is detected, and the detected sample position is determined as the synchronization channel symbol timing.

However, the synchronization acquisition unit 620 may further include an accumulator 623 as shown in FIG. 9 to increase symbol synchronization detection performance.

The accumulator 623 adds each correlation value for each of 4,800 sample positions, and adds each correlation value for samples separated by each sync block length from each sample position.

When the synchronization acquisition unit 620 includes the accumulator 623, the timing detector 624 detects the maximum value among the 4800 values stored in the accumulator 629 to detect the sample position of the detected maximum value. It outputs as (S5).

FIG. 10 is a block diagram illustrating a configuration of the code & boundary detection unit 640 of FIG. 8 according to an exemplary embodiment of the present invention. Referring to FIG. 10, a frequency offset correction unit 645 and a frame boundary & code detector 650 are included.

The frequency offset correction unit 645 sets the synchronization channel symbol timing 641 based on the output S5 of the synchronization acquisition unit 620, and the length of each sync block based on the synchronization channel symbol timing 641. Over the interval, the received signal samples of the 4xN _S first sync channel estimation positions provided from the sync channel band filters 610 -A and 610 -B are stored, and then the frequency offset is first estimated using the same. After correcting the frequency offset for the 4xN _S received signal samples based on the estimated frequency offset, the corrected 4xN _S received signal samples S9 and S10 are provided to the frame boundary & code detector 650. do.

The frame boundary & code detector 650 detects the scrambling code identifier and the 10 msec frame timing by using the frequency offset corrected samples S9 and S10 and passes them to the control block.

The frame boundary & code detection unit 650 performs Fourier transform of Ns received sample values for each of the synchronization channel symbol positions 642-A to 642-D, and converts them into signals in the frequency domain, thereby enabling all possible second synchronization channel sequences. Correlate all of the cyclic shifts to select the correlation component having the maximum value, and then acquire not only the cell identifier of the target cell but also the frame timing by taking the identifier of the second sync channel sequence and the cyclic shift index value. .

In this case, the first sync channel component in the Fourier transform frequency domain signal is used as a channel estimation for coherent correlation of the second sync channel sequence.

11 is a block diagram showing the configuration of the frame boundary & code detection unit 650 of FIG. 10 according to an embodiment of the present invention. Referring to FIG. 11, the code correlation value calculating units 665 -A and 665 -B, the combiner 656, the shift sequence detector 658, the frame boundary detector 840, and the cell identifier detector 830. It is made, including.

The mobile station does not know what the second sync channel sequence identifier and the cyclic shift index are mapped to the received second sync channel symbols, so it performs a Fourier transform on the N _S samples of each of the sync channel symbols into a signal in the frequency domain. After switching, both subcarriers allocated to the dual second synchronization channel should be correlated with respect to all possible second synchronization channel sequences and possible cyclic shifts of the second synchronization channel sequence.

In this case, the first sync channel component is used as a channel estimation for coherent correlation of the second sync channel sequence.

The code correlation value calculation units 665 -A and 665 -B perform Fourier transform on each of the synchronization channel symbols S9 and S10 that have been frequency offset corrected by the frequency offset correction unit 645, and then convert them into signals in the frequency domain. A correlation is calculated for both the second sync channel sequence and the possible cyclic shifts of the second sync channel sequence.

In this case, the first sync channel component is used as channel estimation for coherent correlation of the second sync channel sequence.

The combiner 656 combines the outputs of the second correlation value calculators 665 -A and 665 -B and provides the combined correlation values to the shift sequence detector 658.

Where L is the number of second sync channel sequences (or the number of cell identifiers), P is the number of shifts (or the number of sync blocks per frame) of the second sync channel sequence possible, and is 4 in the examples of FIGS. 2 in the example of FIG. 2 and FIG. 6.

After all, the shift sequence detector 658 selects the maximum value among the correlation values of all the PxL shifted sequences, and then transfers the index value λ of the maximum value to the scrambling code (cell) identifier detector 830 and the frame boundary detector 840. to provide.

The scrambling code (cell) identifier detector 830 detects the scrambling code identifier (or section identifier) of the target base station by performing an L module operation on the output received from the shift sequence detector 658. That is, it is expressed as Equation 4 below.

Scrambling Code Identifier = λ _{mod L}

In Equation 8, [lambda] is an output of the shift sequence detector 658. L is the total number of sync channel sequences used in the system.

The frame boundary detector 850 acquires frame boundary information by performing an operation defined by Equation 5 below to the output received from the shift sequence detector 658.

Frame boundary identifier = [λ ÷ L]

In Equation 5, [x] means a natural number having a maximum value among natural numbers less than or equal to x.

The frame boundary identifier is a unit of sync block length from the first position 644-A of the P sync channel symbol intervals 643-A to 643-D used by the code & boundary detector 650. Indicate how far apart it is.

The code correlation value calculators 665 -A and 665 -B include Fourier transform units 651-A and 651 -B, demapping units 652-A and 652 -B, and channel estimator 653 -A, 653-B) and correlation value generators 820-A and 820-B.

The Fourier transform units 651-A and 651-B perform Fourier transform on time domain samples 642-A to 642-D corresponding to the respective sync channel symbol regions, thereby performing N _S frequency domains on each symbol. Get the converted value.

Demapping unit (652-A, 652-B ) is PxN ₁ values corresponding to sub-carriers of a first synchronization channel sequence from the obtained total frequency conversion value (see Fig. 4) and a second synchronization channel sequence sub-carriers The value of ₂ PxN (refer FIG. 4) is acquired.

A channel estimator (653-A, 653-B ) are each sub-carrier using a first synchronization channel sequence represented by the formula (1) stored in advance from the de-mapping section PxN ₁ of first sync channel frequency domain received sample value received from the Perform channel estimation for.

The second sync channel code correlation unit correlates the PxN _two second sync channel frequency domain received sample values received from the demapping unit with possible PxL shifted second sync channel sequences.

At this time, in order to increase the detection probability, the channel distortion is corrected for each subcarrier by using the channel estimation values passed from the channel estimators 653 -A and 653-B to perform cross-correlation.

The correlation between PxN _two second sync channel frequency domain received sample values and possible PxL shifted second sync channel sequences will be described with reference to FIG.

12 is a conceptual diagram of performing correlation with all possible cyclic shift sequences of a second synchronization channel to obtain a frame boundary and a cell identifier according to an embodiment of the present invention.

Given the demapping unit outputs 901-A through 901-D for the second synchronization channel at the first to fourth synchronization channel symbol positions, it is not necessary to know which part is the frame boundary. 0 cyclic shift), equation 7 (1 cyclic shift), equation 8 (2 cyclic shift), and equation 9 (3 cyclic shift).

As a result, the second sync channel correlation value calculator outputs a total of PxL (P = 4 in the above example).

The PxL code correlator outputs are combined for each component in the signal combiner 656 and transferred to the shift sequence detector.

The shift sequence detector 658 detects the maximum value of the P * L outputs of the signal combiner 656 and scrambling code (cell) identifier detector 830 and the frame boundary detector for the index value λ corresponding to the maximum value. Pass it to (840).

The scrambling code (cell) identifier detector 830 performs a L module operation on the output λ received from the shift sequence detector 658 as shown in Equation 4 to detect the cell identifier of the target base station, and then controls the controller 530. Pass it to).

The frame boundary detector 840 obtains the frame boundary information by performing the operation defined by Equation 5 on the output λ received from the shift sequence detector 658, and then passes it to the controller 530.

FIG. 13 is a conceptual diagram in which a mobile station performs correlation with all possible cyclic shift sequences of a second sync channel for cell identification and frame contention to access a TDM system according to an embodiment of the present invention.

Given that the demapper output 1900 for the first secondary sync channel symbol position and the demapper output 1901 for the second secondary sync channel symbol position are not known which part is a frame boundary, Cross correlation is performed for all possible sequences of Equations 6 (0 cyclic shift) and 7 (1 cyclic shift).

14 is a flowchart illustrating a cell searching method of an FDD / TDD dual mode mobile station according to an embodiment of the present invention.

In operation S100, the dual mode mobile station searches for a cell that transmits an FDM frame.

It is determined whether the cell search is completed within the predetermined T1 (S120). If the cell search is completed within the T1, the cell search is terminated. If the cell search is not completed within the T1, the cell is searched for the transmission of the TDM frame frame (S140). ).

If the cell search is completed within the predetermined T1 (S160), the cell search is terminated.

15 is a flowchart illustrating an FDD cell search method or a TDM cell search method according to an exemplary embodiment of the present invention.

As mentioned above, step S200 is a sync block synchronization acquisition step, and step S210 is a step of detecting a frame boundary and scrambling code identifier including frequency offset correction.

The maximum value of the correlation value for the sync channel sequence detected in step 2 and its shifted sequence is compared with a preset threshold, and when the value is larger than the threshold (S220), the cell search is completed. do.

The invention can also be embodied as computer readable code on a computer readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable recording media include ROM, RAM, CD_ROM, magnetic tape, floppy disks, and optical data storage, and may also include those implemented in the form of carrier waves (e.g., transmission over the Internet). . The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

As described above, optimal embodiments have been disclosed in the drawings and the specification. Although specific terms have been used herein, they are used only for the purpose of describing the present invention and are not intended to limit the scope of the present invention as defined in the claims or the claims. Therefore, those skilled in the art will understand that various modifications and equivalent other embodiments are possible from this. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

1 is a view showing the structure of a forward link frame in an FDD wireless communication system according to an embodiment of the present invention.

2 is a diagram illustrating a subframe including a sync channel symbol in downlink of an FDD wireless communication system according to an embodiment of the present invention.

3 is a view showing the structure of a downlink frame of a TDD wireless communication system according to an embodiment of the present invention.

4 is a diagram illustrating a subframe including a sync channel symbol in a TDD wireless communication system according to an embodiment of the present invention.

5 is a diagram illustrating a frequency mapping form of a synchronization channel in FDD mode according to an embodiment of the present invention.

6 is a diagram illustrating a frequency mapping form of a synchronization channel in the TDD mode according to an embodiment of the present invention.

7 is a block diagram showing the configuration of a base station transmitter according to an embodiment of the present invention.

8 is a block diagram showing the configuration of a receiver of a mobile station according to an embodiment of the present invention.

9 is a block diagram showing a configuration of a synchronization acquisition unit of FIG. 8 according to an exemplary embodiment of the present invention.

10 is a block diagram illustrating a configuration of the code & boundary detection unit of FIG. 8 according to an exemplary embodiment of the present invention.

FIG. 11 is a block diagram showing the structure of the frame boundary & code detector of FIG. 10 according to an embodiment of the present invention.

12 is a conceptual diagram of performing correlation with all possible cyclic shift sequences of a second synchronization channel to obtain a frame boundary and a cell identifier according to an embodiment of the present invention.

FIG. 13 is a conceptual diagram of a mobile station performing correlation with all possible cyclic shift sequences of a second synchronization channel for cell identifier and frame contention to access a TDM system according to an embodiment of the present invention.

14 is a flowchart illustrating a cell searching method of an FDD / TDD dual mode mobile station according to an embodiment of the present invention.

15 is a flowchart illustrating an FDD cell search method or a TDM cell search method according to an exemplary embodiment of the present invention.

Claims (16)

In the forward synchronization signal transmission method in a wireless communication system, Generating a frame composed of a plurality of sync blocks; Transmitting the frame over a forward link, The frame is A first sync channel sequence providing sync block timing information and a plurality of second sync channel sequences providing frame timing information, and specifying a cell identifier by the first sync channel sequence and the plurality of second sync channel sequences , And using the first sync channel sequence and the plurality of second sync channel sequences in both a time division duplex and a frequency division duplex system. The method of claim 1, In the TDD / FDD wireless communication system, the first sync channel sequence is repeatedly arranged in the same position on the sync block in the frame. The method of claim 1, And the number of first sync channel subcarriers for allocating the first sync channel sequence for each TDD / FDD wireless communication system is the same in the frame. The method of claim 1, The first sync channel sequence and the second sync channel sequence in a TDD wireless communication system are arranged in a time division multiplexing (TDM) manner in the adjacent symbol interval in the frame. The method of claim 1, The first synchronization channel sequence and the second synchronization channel sequence in the FDD wireless communication system, characterized in that arranged in the frequency division multiplexing (FDM) method in the same symbol interval in the frame. The method of claim 1, In the TDD / FDD wireless communication system, the second sync channel sequence is different for each cell and is different for each second sync channel symbol period in a frame even in the same cell. A method for detecting a cell identifier using a forward synchronization signal in a TDD / FDD dual mode terminal on a wireless communication system, Receiving a frame consisting of a plurality of sync blocks, the synchronization channel sequence is arranged in a TDM method or FDM method, Extracting sync block timing and frame timing information from a first sync channel sequence and a plurality of second sync channels obtained in consideration of the manner in which the sync channel sequences are arranged in the frame, the first sync channel sequence and the plurality of first 2. A cell identifier detection method using a forward synchronization signal in a TDD / FDD dual mode terminal, characterized by detecting a cell identifier through a combination of two synchronization channel sequences. The method of claim 7, wherein When the sync channel sequence is arranged in the FDM scheme in the frame, the same first sync channel sequence is extracted for each sync block from the mapping on the frequency domain, When the sync channel sequence is arranged in the TDM scheme in the frame, a cell identifier using a forward sync signal in the TDD / FDD dual mode terminal is extracted from the same first sync channel sequence mapped to each sync block in the time domain. Detection method. The method of claim 7, wherein And extracting the sync block timing using the time domain waveform of the first sync channel sequence. The method of claim 7, wherein In the plurality of second sync channel sequences, the frame synchronization information is extracted using a second sync channel sequence in a second sync channel symbol section within a frame. Cell identifier detection method using. delete delete delete delete delete delete

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