KR20070120408A - Structure of hybrid synchronization channel, method and apparatus for transmitting signal, applying and analyzing the sequence using the same - Google Patents

Abstract

A hybrid synchronization channel structure and a method and an apparatus for transmitting signals, applying and analyzing a sequence using the same are provided to obtain synchronization information of good quality in both of a synchronous network and an asynchronous network, and perform synchronization acquisition by auto-correlation and cross-correlation mostly performed in the synchronous and asynchronous networks, thereby improving accuracy of acquired synchronization information. A primary synchronization channel includes a sequence commonly used in a communication network, and includes a repetitive structure of a sequence in a time domain. A secondary synchronization channel includes a sequence for transmission of information except control information included in the primary synchronization channel. The secondary synchronization channel also includes a repetitive structure of the sequence at the time domain. The repetitive structure is composed by inserting a specific sequence at predetermined periods in a frequency domain.

Description

Structure Of Hybrid Synchronization Channel, Method and Apparatus For Transmitting Signal, Applying And Analyzing The Sequence Using The Same}

1A and 1B are conceptual views conceptually illustrating a hierarchical sync channel structure and a non-hierarchical sync channel structure, respectively.

2 is a conceptual diagram conceptually illustrating a hybrid SCH structure according to an embodiment of the present invention.

3 is a block diagram illustrating an apparatus for transmitting a composite synchronization channel signal in accordance with an embodiment of the present invention.

4 is a flowchart showing a step structure of a synchronization acquisition method according to an embodiment of the present invention.

5A and 5B illustrate that a cyclic shift is applied to a sequence inserted into each sync channel by a sequence applying method according to an embodiment of the present invention, and a primary sync channel (P-SCH) and an auxiliary sync channel (S-SCH) are shown in FIG. Fig. Showing the structure in which the same sequence is inserted in the diagram.

6A and 6B illustrate a structure in which a cyclic shift is applied to a sequence inserted into each sync channel by a sequence applying method according to an embodiment of the present invention, and one sequence is divided and inserted into a primary sync channel and a secondary sync channel. Figure.

7A and 7B illustrate a structure in which a cyclic shift is applied to a sequence inserted into each sync channel by a sequence applying method according to an embodiment of the present invention, and different heterogeneous sequences are inserted into a primary sync channel and a secondary sync channel. Figure.

FIG. 8 is a diagram showing a result indicating an impulse response of a radio channel in a sequence received by a sequence analysis method according to an embodiment of the present invention. FIG.

Fig. 9 is a diagram showing a comparison of detection error rates in the case of using the sequence analysis method according to the embodiment of the present invention and in the case of the conventional sequence analysis method.

The present invention relates to a communication system, and more particularly, to a complex synchronization channel structure and a signal transmission, sequence application, and sequence analysis method and apparatus using the same.

In a communication system, particularly in a wireless communication system, the terminal must synchronize with the base station in order to communicate with the base station providing the service. There are two ways to achieve this synchronization, one of which is to synchronize the terminal with the clock of the base station, and the other is to synchronize through random access between the base station and the terminal. .

The method of synchronizing the terminal with the clock of the base station described above is a case in which the terminal synchronizes with the base station with a signal transmitted by the base station constantly. In a system such as a mobile communication system where the terminal always exists at any time It's a way to keep in touch On the other hand, the method of securing a communication base by acquiring synchronization through a random access between the base station and the terminal does not always have to synchronize with each other, but only with a narrow time unit of a packet unit to communicate with. This type of system is suitable for use in systems that need to be implemented inexpensively, such as WLAN or wireless fan (WPAN).

In general, in a mobile communication system, a system configuration is implemented based on a cell. In order for a terminal of each specific location to access a mobile communication service, it is required to synchronize with a base station that is received with a signal having the strongest strength due to its own signal characteristics. After synchronizing in this manner, various signal format information is obtained from the base station, and the user is notified again by means of synchronizing uplink synchronization such as a random access channel.

In addition, a mobile communication base station typically transmits a signal with a certain time frame. The mobile communication base station transmits a signal capable of synchronizing itself to a specific location. This is called a synchronization channel (SCH). When a specific sequence is inserted into the synchronization channel, the mobile station detects the sequence. Synchronization can be made with respect to the time and frequency of the base station. An example of a synchronization channel currently being discussed in 3GPP LTE is as follows.

1A and 1B are conceptual views conceptually illustrating a hierarchical SCH structure and a non-hierarchical SCH structure, respectively.

In the case of FIG. 1A, there are two synchronization channels: a primary SCH (P-SCH) and a secondary SCH (S-SCH). Among them, P-SCH is used for the terminal to find the time synchronization and frequency synchronization of the base station initially, S-SCH is a channel for finding the ID and additional information of the base station in accordance with the detected time synchronization and frequency synchronization Used. In general, the P-SCH signal is transmitted by all base stations to the same signal, and the terminal already knows the signal, and the S-SCH signal transmits signal information specific to each base station and the terminal should detect the specialized signal information. As described above, since the P-SCH has a hierarchical form of finding time synchronization and then obtaining base station information from the S-SCH, a hierarchical synchronization channel structure is used. A cell search using the hierarchical cell is called a hierarchical cell search. Here, for example, signal information specialized for the base station may include information such as cell ID, cell group ID, bandwidth information of another channel, CP length, number of transmitting antennas, and the like.

In contrast, in FIG. 1B, only one synchronization channel (SCH) exists, and the structure of the channel has a repeating pattern in the time domain. In order to find the time synchronization using this, the UE should detect this repetition pattern generated by the base station through auto-correlation, and the position where this autocorrelation value is maximum becomes time synchronization. From this time synchronization, the location of the SCH is determined, the SCH channel signal is extracted, and base station specific information contained therein is obtained. In FIG. 1B, the signal transmitted to the SCH satisfies the condition that it has a repetitive structure in the time domain and transmits a signal specific to a specific base station. That is, the P-SCH and the S-SCH of the hierarchical structure of FIG. 1A are summed together.

On the other hand, in order for the terminal to detect a signal through the synchronization channel, it is necessary to determine in advance which signal to detect. The signals to be used for this sync channel, i.e. the specific sequences, may be different in both the mobile communication system and the system under development. In the case of 3GPP LTE, the CAZAC sequence is the strongest candidate, and in the case of WCDMA, it is based on the Gold Code.

Two kinds of CAZAC sequences are used, which are GCL CAZAC and Zadoff-Chu CAZAC. The relationship between these two types is tied together by a conjugate complex relationship, so Zadoff-Chu CAZAC is obtained by applying the conjugate complex operation to the GCL CAZAC. Zadoff-Chu CAZAC is given by

Here k denotes a sequence index, N denotes a length of a CAZAC sequence to be generated, and M denotes a sequence ID.

When the Zadoff-Chu CAZAC sequence given by Equation 1 and Equation 2 and the GCL CAZAC sequence in the conjugate complex relationship thereof are represented by c (k; N, M), all three features are as follows.

Equation 3 shows that a CAZAC sequence always has a size of 1, and Equation 4 shows that an auto-correlation function of a CAZAC sequence is represented as a delta function. Here autocorrelation is based on circular correlation. In addition, Equation 5 shows that the cross-correlation is always constant.

As shown in Equation 3, since the signal transmitted to the SCH is constant, the PAPR (Peak-to-Average Power Ratio) is low, so that the boosting stage can sufficiently boost the time-domain signal. To provide. In addition, the feature as shown in Equation 4 provides a basis for finding the correct time synchronization when the terminal detects a sequence from the synchronization channel, the last feature of Equation 5 is a mixture of synchronization channels of several base stations In this case, it is possible to effectively treat each base station.

As described above, the CAZAC sequence is inserted into a synchronization channel having a hierarchical or non-hierarchical structure as shown in FIGS. 1A and 1B, and transmitted. Sensitive performance changes depending on how they are deployed and synchronized. The hierarchical structure has a disadvantage in that the time symbol synchronization performance is more affected by the frequency offset than the non-hierarchical structure. On the other hand, a non-hierarchical structure can acquire time symbol synchronization regardless of frequency offset, but when timing signals are received by interference, i.e., when signals are overlapped from other cells, the repeated characteristics in the time domain are destroyed to obtain timing synchronization. it's difficult.

In addition, the non-hierarchical structure generally shows excellent performance in a synchronous network having the same transmission time between base stations, but poor performance in an asynchronous network having a random transmission time between base stations. On the contrary, hierarchical structure shows relatively good performance in asynchronous network, but poor performance in synchronous network.

In addition, when a CAZAC sequence or a specific sequence is used as a sequence transmitted through the synchronization channel as described above, a method of transmitting additional information as a sequence type provided by them includes N pieces of total code types for a sequence of length N. There is a limit to information delivery because it does not provide the ideal.

SUMMARY OF THE INVENTION In order to solve the above problems, an object of the present invention is to provide a synchronization channel structure having a complex structure accommodating the advantages of a hierarchical synchronization channel and a non-hierarchical synchronization channel, and a method and apparatus for transmitting or forming the same. .

Another object of the present invention is to provide a method of acquiring synchronization using the above-described channel structure having a complex structure and performing a cell search based thereon.

Another object of the present invention is to provide a sequence application method that can increase the amount of control information transmitted by applying a cyclic shift to a sequence that can be applied to a channel having a complex structure described above.

It is still another object of the present invention to provide a method for acquiring control information by analyzing a sequence when a sequence to which a cyclic shift is applied to a channel having a complex structure is received.

A synchronization channel structure according to an embodiment of the present invention for achieving the above object comprises a main synchronization channel including a sequence commonly used in a communication network, and including a repetition structure of the sequence in the time domain; And an auxiliary synchronization channel including a sequence for transferring information other than control information included in the primary synchronization channel. Hereinafter, the sync channel structure having the above-described structure will be referred to as a "complex sync channel structure" for convenience of description. In this case, the control information included in the auxiliary synchronization channel may not only include heterogeneous information different from the control information included in the primary synchronization channel, but may also include information for repeating control information included in the primary synchronization channel. .

In addition, the auxiliary synchronization channel as well as the main synchronization channel may also include a repetition structure of the sequence in the time domain, and the above-described repetition structure included in the primary synchronization channel and / or the auxiliary synchronization channel may specify a specific sequence in the frequency domain. It can be made by inserting every cycle.

According to another aspect of the present invention, there is provided a signal transmission method comprising: inserting a specific signal into a synchronization channel signal to transmit control information; And transmitting the synchronization channel signal to a receiving side, wherein the synchronization channel includes a sequence commonly used in a communication network, the primary synchronization channel including a repetition structure of the sequence in a time domain; And an auxiliary synchronization channel including a sequence for transferring information other than control information included in the primary synchronization channel.

In addition, the signal transmission apparatus according to another embodiment of the present invention includes a synchronization channel signal construction unit for inserting a specific signal into the synchronization channel signal for transmitting control information; And a transmission unit for transmitting the synchronization channel signal established by the synchronization channel signal construction unit to a receiving side, wherein the synchronization channel includes a sequence commonly used in a communication network, and the sequence is repeated in a time domain. A main sync channel comprising a structure; And an auxiliary synchronization channel including a sequence for transferring information other than control information included in the primary synchronization channel.

Meanwhile, a method of forming a synchronization channel structure according to another embodiment of the present invention for achieving the above object includes a sequence commonly used in a communication network and includes a main synchronization channel including a repetition structure of a sequence in a time domain. Forming; And forming an auxiliary synchronization channel including a sequence for transferring information other than control information included in the primary synchronization channel formed as described above. In this case, the control information included in the auxiliary synchronization channel may not only include heterogeneous information different from the control information included in the primary synchronization channel, but may also include information for repeating control information included in the primary synchronization channel. .

In accordance with yet another aspect of the present invention, there is provided a synchronization acquisition method. The method includes: determining whether a network in which communication is performed is synchronous using a complex synchronization channel structure as described above; And acquiring synchronization through a repetition structure of a primary synchronization channel when the network through which communication is performed is a synchronous network.

In this case, the acquiring of the synchronization may include selecting a repetition structure of the shortest sequence among the repetition structures of the primary synchronization channel and the auxiliary synchronization channel; And acquiring synchronization through autocorrelation of the shortest repetitive structure selected as described above. In addition, the method may further include increasing the accuracy of the synchronization obtained as described above by using the aforementioned common sequence of the main synchronization channel.

In accordance with yet another aspect of the present invention, there is provided a synchronization acquisition method. The method includes: determining whether a network in which communication is performed is synchronous using a complex synchronization channel structure as described above; And acquiring synchronization through a common sequence included in the primary synchronization channel when the network in which the communication is made is an asynchronous network.

The method may further include increasing the accuracy of the synchronization obtained as described above by using the repetition structure of the primary synchronization channel or the auxiliary synchronization channel.

On the other hand, the cell search method according to another embodiment of the present invention for achieving the above object comprises the steps of using a complex synchronization channel structure as described above, determining whether the network to which the communication is synchronous; When the network in which the communication is performed is a synchronous network, acquiring synchronization through a repetition structure of the primary synchronization channel; And acquiring control information including an ID of the base station from a sequence included in the primary synchronization channel and the auxiliary synchronization channel using the synchronization obtained as described above.

Alternatively, a cell search method according to another embodiment of the present invention for achieving the above object comprises the steps of: determining whether a network in which a communication is made is synchronous, using a complex synchronous channel structure as described above; When the network in which communication is performed is an asynchronous network, obtaining synchronization through a common sequence included in the primary synchronization channel; And acquiring control information including an ID of the base station from a sequence included in the primary synchronization channel and the auxiliary synchronization channel using the synchronization obtained as described above.

In addition, a sequence applying method according to another embodiment of the present invention for achieving the above object includes a main synchronization channel and an auxiliary synchronization channel, the main synchronization channel has a structure including a repeating structure of the sequence in the time domain CLAIMS 1. A method of applying a sequence to be inserted into a synchronization channel, comprising: generating a sequence to be applied to a primary synchronization channel and an auxiliary synchronization channel; And applying cyclic shift to the sequences in the time or frequency domain.

The applying of the above-described cyclic shift may include applying a predetermined delay value to a first region index, which is a selected region among time or frequency domains of the sequences; And applying a modulation function based on the length of the sequences. Alternatively, the step of applying the above-described cyclic shift may be performed in the second region, which is any one selected from the frequency and time domains. And multiplying the sequences by a complex exponential function.

Meanwhile, in the step of applying the aforementioned cyclic shift, different cyclic shifts may be applied to the primary sync channel and the auxiliary sync channel. In addition, in the step of generating a sequence to be applied to the above-described primary and secondary synchronization channel, the sequence applied to the secondary synchronization channel is generated as a repetitive sequence of the sequence applied to the primary synchronization channel, or the sequence is a sequence The sequence to be applied to the primary sync channel and the sequence to be applied to the auxiliary sync channel may be divided or applied, or the sequence to be applied to the primary sync channel and the sequence to be applied to the auxiliary sync channel may be different types of sequences.

A sequence analysis method according to another embodiment of the present invention for achieving the above object is a method for analyzing a sequence in which a cyclic shift is applied to a sequence inserted into a primary sync channel and an auxiliary sync channel at a receiving end of a communication system. Obtaining ID information of the sequence by generating a differential sequence of the sequence; And compensating for the received sequence using the selected sequence by using the obtained sequence ID information, thereby obtaining a cyclic shift value of the received sequence.

In this case, the step of obtaining the cyclic shift value as described above, when the received sequence is a sequence in which the cyclic shift is applied in the frequency domain, to obtain the cyclic shift value by compensating the received sequence in the time domain, the received sequence When cyclic shift is a sequence applied in the time domain, the cyclic shift value may be obtained by compensating the received sequence in the frequency domain.

In the obtaining of the above-described cyclic shift value, the received sequence may be compensated by multiplying the received sequence by the conjugate complex sequence of the selected sequence using the obtained sequence ID information. The step of obtaining the cyclic shift value when the application of the cyclic shift is applied on a group basis may include adding power in each delay group of the sequence whose reception sequence is compensated for; And selecting a group representing the maximum of the summed powers as described above.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. The detailed description, which will be given below with reference to the accompanying drawings, is intended to explain exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the present invention may be practiced. The following detailed description includes specific details in order to provide a thorough understanding of the present invention. However, one of ordinary skill in the art appreciates that the present invention may be practiced without these specific details. In some instances, well-known structures and devices are omitted or shown in block diagram form, centering on the core functions of each structure and device, in order to avoid obscuring the concepts of the present invention. In addition, the same components will be described with the same reference numerals throughout the present specification.

2 is a conceptual diagram conceptually illustrating a composite synchronization channel structure according to an embodiment of the present invention.

The composite synchronization channel structure as shown in FIG. 2 accommodates the advantages of the hierarchical synchronization channel structure and the non-hierarchical synchronization channel structure, and proposes a form that can be used in both a synchronous network and an asynchronous network. This method can use both a method for generating a hierarchical sync channel signal and a method for generating a non-hierarchical sync channel signal at a downlink transmitting end such as a base station. The terminal corresponding to the downlink receiving end searches for a sync signal of the base station. In the case of using a hierarchical synchronization channel, for example, a method of obtaining synchronization by performing cross-correlation using a sequence commonly used in a communication network and a method of using a non-hierarchical synchronization channel. This method supports both methods, for example, a method of acquiring synchronization by performing autocorrelation using a sequence having a repetitive structure in the time domain.

As shown in FIG. 2, the composite synchronization channel structure uses a channel having two layers of P-SCH and S-SCH, and has a characteristic of hierarchical synchronization channel structure in that the P-SCH includes a sequence common to the entire network. And includes a feature of the non-hierarchical sync channel structure in that the sequence has a time domain repetition structure only in the P-SCH or, if necessary, in both the P-SCH and the S-SCH. On the other hand, the sequence to be inserted into the S-SCH is preferably inserted into each cell a sequence representing a cell (Cell Specific Data), the S-SCH as described above also includes a repeating structure in the time domain In this case, such a cell-specific sequence may be formed by forming a structure that is repeated in the time domain.

Therefore, the method of forming the composite synchronization channel structure includes a sequence commonly used throughout the network, and after forming a P-SCH having a repetitive structure in the time domain, other than a control signal transmitted by the P-SCH. The S-SCH may be formed to include the remaining control signals, for example, the cell-specific sequence described above, but the order of formation of each channel may be changed as necessary. In addition, the number of P-SCH and S-SCH may be implemented by a different number of OFDM symbols or channels depending on the system.

As described above, in order to implement a structure that is repeated in the time domain in the P-SCH or in both the P-SCH and the S-SCH, a signal is applied to each synchronization channel of the OFDM system in the N-frequency region as follows. It can be easily implemented by inserting at intervals (N subcarriers). Equation 6 below shows a method of inserting a P-SCH transmission signal and Equation 7 inserts a S-SCH transmission signal.

Here, C _P (k) and C _S (k) modulate a sequence representing information to be transmitted through P-SCH and S-SCH before channel insertion, and S _P (k) and S _S (k) are modulated to a synchronization channel. And N _P and N _S represent a period of inserting a sequence in the frequency domain into the P-SCH and the S-SCH, respectively. The periods N _P and N _S in which the sequences C _P (k) and C _S (k) are inserted into the P-SCH and the S-SCH indicate the number of repetitions of the sequence for each symbol in the time domain as described below. This can be interpreted as N times compression of the time base when the signal is inserted at intervals of N spaces in the frequency domain, and thus equally within 1 symbol, eg 1 OFDM symbol, having a certain time interval. It will be clear to those skilled in the art that the signal has the effect of repeating N times.

FIG. 2 illustrates an example of inserting a sequence at intervals of two spaces by setting N _P and N _S described above in the frequency domain to 2 in both the P-SCH and the S-SCH in the frequency domain. The same sequence is repeated twice in the OFDM symbol. Through this, the receiving side can obtain synchronization information by obtaining an autocorrelation value through a structure repeated twice for each OFDM symbol of the P-SCH and the S-SCH.

On the other hand, unlike the example described above, when data is inserted and transmitted and received in the time domain instead of being inserted and transmitted in the frequency domain, data is transmitted and received in the P-SCH as described above, or in both the P-SCH and S-SCH. The repetition structure in the included time domain may be generated by directly inserting the time signal. Throughout the following description, the term "repetitive structure in time domain" is defined as a concept including both inserting a sequence in a frequency unit in the frequency domain and inserting a signal in the time domain directly and repeatedly as described above. I will use it.

In the case of using the composite synchronization channel structure as described above, as described in more detail below, the synchronization may be estimated using autocorrelation or cross-correlation as needed, and the estimated synchronization may be changed using one method. It is possible to increase the accuracy of the estimated synchronization by additionally using the method, and has the effect of obtaining the synchronization more accurately than in both the synchronous network and the asynchronous network.

3 is a block diagram illustrating an apparatus for transmitting a composite synchronization channel signal according to an embodiment of the present invention.

It is apparent that the signal transmission apparatus for transmitting the synchronization channel signal may be various devices including the base station and the user equipment depending on whether the transmission of the synchronization channel signal is performed in the communication system. Therefore, in FIG. 3, an apparatus capable of transmitting control signals is illustrated as a general transmitter.

As shown in FIG. 3, a signal transmission apparatus according to an embodiment of the present invention includes a synchronization channel signal generator 301 and a transmitter 302. Here, the synchronization channel signal construction unit 301 functions to insert a specific signal into the synchronization channel signal in order to transmit control information in the method of transmitting the signal, wherein the synchronization channels are P-SCH and S-SCH. It is required to include all of them. In addition, the P-SCH includes a sequence commonly used throughout the communication network so that synchronization can be obtained by cross-correlation when the synchronization is estimated at the receiving side, and at the same time, synchronization can be obtained by autocorrelation at the receiving side. It is necessary to include a repeating structure of the sequence in the time domain. In addition, the S-SCH of the synchronization channel used for transmission may include a sequence for transferring information different from the information included in the P-SCH, for example, cell-specific data, and in some cases, the sequence of the P-SCH. It may include a portion to repeat a part.

After the synchronization channel signal generator 301 generates the synchronization channel signal using the synchronization channel having the structure described above, the transmitter 302 transmits the synchronization channel signal in the signal transmission method according to the embodiment of the present invention. It performs the step of transmitting to the receiving side. In FIG. 3, the transmitter 302 converts a serial signal in parallel and transmits the signal through multiple antennas. However, in the signal transmission apparatus according to the exemplary embodiment of the present invention, the transmitter has a synchronization as described above. It may have any structure as long as it can transmit a channel signal, it is not limited to having multiple antennas as shown, it is also possible to have one antenna.

Hereinafter, a method of acquiring synchronization through the synchronization channel signal transmitted as described above will be described.

4 is a flowchart showing a step structure of a synchronization acquisition method according to an embodiment of the present invention.

The synchronization channel in one embodiment of the present invention has a structure including the P-SCH and the S-SCH as described above, where the P-SCH is a repetitive structure of a sequence in the time domain to facilitate synchronization acquisition by autocorrelation. It includes, and also includes a sequence commonly used throughout the network to facilitate synchronization acquisition by cross-correlation. On the other hand, when the network in which communication is performed as described above is a synchronous network, a method of obtaining synchronization by performing autocorrelation using a repetitive structure in the time domain is advantageous, and synchronization is performed by performing cross-correlation through a common sequence. The acquisition method tends to be poor in performance, and has the opposite characteristics when communication is performed in an asynchronous network. Therefore, the synchronization acquisition method according to an embodiment of the present invention proposes a method for obtaining synchronization by selectively performing autocorrelation or cross-correlation according to whether a network to which communication is performed is a synchronous network or an asynchronous network.

First, as shown in FIG. 4, the method determines whether the network in which communication is performed is synchronous in step S401, and proceeds to step S402 in the case of a synchronous network, and in step S406 in the case of an asynchronous network. If the network in which the communication is made is a synchronous network, the method obtains synchronization by using the repetitive structure in the time domain of the P-SCH to perform autocorrelation through steps S402 and S404. To this end, the receiver calculates the following autocorrelation value (M _A ) at all sample positions of the received signal.

Here, r denotes a received signal, n denotes a time domain sample index, and N _A denotes a length for obtaining autocorrelation, and is generally set equal to the period of the repeating structure. Here, when N _A is set by selecting the shortest repeating structure among the repeating structures included in the P-SCH and the S-SCH, as shown in step S402 of FIG. 4, an autocorrelation value M _A such as Equation 8 is obtained. The calculation time is reduced and preferred, but need not be limited thereto.

After calculating the autocorrelation value M _A as described above, in step S404, the receiving side selects a point representing the maximum among the calculated autocorrelation values M _A as follows.

The point obtained in Equation (9) is a point at which the transmitting side transmits the SCH when the noise and the interference are ignored, and the receiving side acquires the synchronization information by performing signal processing based on this.

In addition, as shown in FIG. 4, when step S405 is performed, the accuracy of synchronization is improved by comparing with the synchronization obtained by obtaining a cross-correlation value through a sequence commonly used in a network included in the P-SCH. Further, the performance can be improved. In step S405 of FIG. 4, only a case of using a common sequence included in the P-SCH is described as an example, but in some cases, the S-SCH may include a sequence commonly used in a network. It will be appreciated by those skilled in the art that the accuracy of the synchronization can be improved by using it in cross correlation.

On the other hand, when it is determined in step S401 that the network to which communication is performed is asynchronous, the process proceeds to step S406 as described above. In step S406, the receiving side cross-correlates a known sequence with the received signal. Thereafter, in step S407, the maximum value of the cross-correlation values performed in step S406 is detected, thereby obtaining synchronization information.

Of course, the synchronization information obtained as described above is used as the initial synchronization information, and as shown in FIG. 4, through the repetition structure in the time domain of the P-SCH and / or the S-SCH as shown in FIG. And it is desirable to increase the accuracy of the synchronization by going through the process of equation (9).

Such a repetition structure of the P-SCH and / or S-SCH is a good reference for acquiring time synchronization at the receiving side and increases accuracy in performing frequency synchronization. In general, the shorter the period of the repeating pattern, the more the frequency synchronization can be compensated for the range corresponding to the inverse of the value. In particular, even if the repetition patterns of the P-SCH and the S-SCH are not the same, the receiving side can estimate the time and frequency synchronization values from the repeated patterns, respectively, thereby reducing the cell search time of the terminal.

In addition, the cell search method according to an embodiment of the present invention is a method for performing a cell search by acquiring control information including the ID of the transmitting side and basic information necessary for subsequent processing using the synchronization information obtained as described above. Can also be proposed.

Hereinafter, a sequence application method according to an embodiment of the present invention will be described.

As described above, a cyclic shift applied to sequences inserted into a synchronization channel having a complex structure may be applied regardless of the type of code to be actually applied, for example, a CAZAC code, a PN code, and the like. The delay information is based on estimating the applied delay value by calculating all possible delay values, but in the case of a system employing modulation techniques usable in the frequency domain such as OFDM, a simple detection will be described later. It can be estimated at the receiving side by the method. First, the method of applying such circular movement will be described in detail.

There are two ways to apply cyclic shift to a sequence. One is to directly cycle the sequence itself, and the other is to multiply it by a complex exponent. In addition, the method of directly cyclically moving the sequence itself can be represented by the following equation.

Here, d denotes a delay value, c (k) denotes a sequence to be applied to a channel before circular shift is applied, s (k) denotes a sequence to which circular shift is applied, and N denotes a length of sequences to be applied to the channel. Indicates. As shown in Equation 10, a sequence s (k) generated by applying mods based on N to delayed by d is generated as a sequence having the same length as c (k) but delayed by d.

As described above, the second method of applying the cyclic shift by multiplying the complex index can be expressed in two ways as follows.

Where F is an operator representing a Fourier transform.

Equations 11 and 12 represent the same method in different ways. In the case of multiplying complex exponents as shown in Equation 11, Fourier transforms a sequence as shown in Equation 12 and then cyclically shifts it in another region. Has the same meaning. When using the sequence to which the cyclic shift is applied as described above, it is possible to transmit additional information depending on the extent of the delay value d used for the cyclic shift, and the delay values applied to the P-SCH and the S-SCH are different. More control information can be transferred. In addition, the amount of information transmitted on the synchronization channel transmitted in various ways as well as the cyclic movement to the P-SCH and S-SCH can be increased, with reference to Figures 5a to 7b.

5A to 7B illustrate a structure in which a circular shift is applied to a sequence inserted into each synchronization channel by a sequence applying method according to an embodiment of the present invention, and FIGS. 5A and 5B illustrate P- 6A and 6B show a structure in which the same sequence is inserted into the SCH and the S-SCH. FIG. 6A and 6B show a structure in which one sequence is inserted into the P-SCH and the S-SCH. FIG. 7A and 7B show the P-SCH and the S-SCH. 2 is a diagram illustrating a structure in which different heterogeneous sequences are inserted.

In the P-SCH and the S-SCH of FIG. 5A, sequences are inserted at intervals of two spaces in the frequency domain, thereby including two repetition structures for each OFDM symbol in the time domain, and both SCHs are subjected to the same length cyclic shift. Shown. Here, the arrow indicates the start position of the sequence inserted in each sync channel. As described above, the degree of cyclic shift applied to the P-SCH and the S-SCH indicates predetermined control information. In FIG. 5A, the same delay amount is applied, and the resulting cyclic shift is applied to the P-SCH and the S-SCH. The movement may indicate the same information, but the same delay amount information applied to different synchronization channels may be set to indicate different information. Meanwhile, since the cyclic shift amounts applied to the P-SCH and the S-SCH are not necessarily the same as shown in FIG. 5A, an arrow may exist at any position according to the cyclic shift amount applied to each sync channel.

The P-SCH shown in FIG. 5B shows a result of applying a cyclic shift of a degree different from that of the P-SCH shown in FIG. 5A, and the S-SCH is inserted at intervals of one space in the frequency domain, thereby repeating the structure in the time domain. The result of applying a different amount of cyclic shift to P-SCH is shown. When the S-SCH is inserted at intervals of one space in the frequency domain as described above, the S-SCH does not include a repetitive structure in the time domain, so that the S-SCH cannot be used in the acquisition of synchronization information, but the length of a sequence that can be inserted By doubling, the more accurate result can be obtained in obtaining information other than the synchronization information such as the ID of the transmitting side. In FIG. 5B, the length of the sequence inserted into the P-SCH is N, and the length of the sequence inserted into the S-SCH is 2N, for example.

As described above, FIGS. 6A and 6B illustrate embodiments in which cyclic shift is applied to sequences inserted into P-SCHs and S-SCHs, and one sequence is divided and inserted into both synchronization channels. Accordingly, the P-SCH and the S-SCH of FIG. 6A show an example of dividing a sequence having a total length of 2N into N sequences and inserting the N-sequence into the P-SCH and the S-SCH. The cyclic movement amount also shows a different example. Therefore, the total length of a sequence that can be inserted into both synchronization channels is doubled, and more control information can be accurately transmitted by controlling the sequence having the length of twice and the cyclic shift amount applied to each synchronization channel. In this case, the P-SCH must include a repetitive structure in the time domain so that synchronization can be obtained by autocorrelation, and must include a sequence common to the network so that synchronization can be obtained by cross-correlation. A sequence inserted into the divided S-SCH may also include a common sequence. However, depending on the correlation between acquiring the correct synchronization information and transmitting the control information other than the synchronization information more accurately, a specific sequence determined for each cell may be used for both the P-SCH and the S-SCH. In this case, the S-SCH information is not directly converted into an OFDM signal, but the actual information of the S-SCH may be regarded as the cyclic shift amount itself.

FIG. 6B illustrates a structure in which one sequence is inserted into P-SCHs and S-SCHs as described above. In particular, unlike in the case of FIG. 6A, a sequence insertable by not forming a repeating structure in the S-SCH is illustrated. An example is shown in which the length of is doubled (the length of a sequence inserted into the entire P-SCH and S-SCH is tripled). In this case, the length of a sequence that can be inserted into both synchronization channels is 3N, and N sequence sequences are inserted into a P-SCH including a repeating structure, and 2N sequence sequences are inserted into an S-SCH. An example of moving is shown. As a result, the amount of control information that can be transmitted using the synchronization channel can be increased, and the accuracy thereof can also be increased even when transmitting information such as an ID of a transmitter.

Lastly, FIGS. 7A and 7B illustrate a case in which cyclic shift is applied to sequences to be inserted into P-SCH and S-SCH as described above, and sequences inserted into respective sync channels are different types of sequences. As shown. Here, the different types of sequences inserted into the P-SCH and the S-SCH may be sequences having different values corresponding to IDs among the same kinds of sequences, and include key features used for generating a sequence including the above-described cases. All sequences having different properties may correspond to this. This increases the amount of control information transmitted by increasing the combination of sequences that can be transmitted through the P-SCH and the S-SCH. In addition, as described above, the same or different amount of cyclic shift is applied to the sequences inserted into the P-SCH and the S-SCH, and this cyclic shift amount itself represents another control information. In FIG. 7A, both the P-SCH and the S-SCH include a repetitive structure in the time domain, and sequences inserted into respective sync channels are different types of sequences, and amounts of cyclic shift applied to sequences inserted into respective sync channels are also different. An example is shown. On the other hand, in FIG. 7B, only the P-SCH includes a repetitive structure in the time domain, and instead of having a repetitive structure in the time domain, a sequence string having a length of twice is inserted and inserted into each sync channel. The sequence shows an example in which different degrees of cyclic shift are applied.

5A to 7B, the cyclic shift is inserted into the sequences inserted into the respective synchronization channels and the combination of the sequences inserted into the respective synchronization channels is selected to increase the accuracy of the control information and to expand the combination of the control information. Although the case of obtaining the effect of the present invention has been described by way of example, those skilled in the art will be able to contemplate various modifications having the same principle as well as these examples.

Next, a sequence analysis method according to an embodiment of the present invention will be described in detail.

The sequence generated by the sequence applying method according to the embodiment of the present invention as described above includes a cyclic shift, and the receiving side can acquire additional control information through the degree of the cyclic shift. In addition, the cyclic shift information applied to the cyclic shift is basically calculated by estimating the delay value applied by calculating all possible delay values as described above, but as described below, the receiver side uses a simple detection method. It may be estimated.

To achieve sequence detection as described above, the receiving side first removes the cyclic prefix of the received signal as common in OFDM communication, and then performs a discrete Fourier transform or, if possible, a Fast Fourier transform. Through this, the received signal R (k) may be represented as follows.

, k = 0, 1, 2, ..., N _fft -1

는 순환이동을 포함한 수신신호의 시퀀스를,

는 순환이동을 제외한 수신신호의 시퀀스를, H(k) 는 채널 응답을, N(k)는 잡음을 나타낸다.here,

Is a sequence of received signals including cyclic shift,

Denotes a sequence of received signals excluding cyclic shift, H (k) denotes a channel response, and N (k) denotes a noise.

Thereafter, a step of obtaining a sequence ID of a received signal by generating a differential sequence of the signal R (k) obtained through Equation 13, wherein the used sequence is a GCL CAZAC sequence The M value corresponding to the ID of the GCL code can be estimated through the following equation.

)은 공액복소수 계산에 의해 k 값에 관계없는 상수가 되므로, M값을 추정하는데 영향을 주지 않는다. 이러한 특성을 이용하기 위해, 수신된 시퀀스가 순환이동이 주파수 영역에서 적용된 시퀀스인 경우 시간영역에서 상술한 바와 같은 방법으로 추정된 시퀀스의 공액복소수 시퀀스를 이용하여 보상하는 것이 바람직하며, 반대로 수신된 시퀀스가 순환이동이 시간 영역에서 적용된 시퀀스인 경우 주파수 영역에서 상술한 바와 같은 방법으로 추정된 시퀀스의 공액복소수 시퀀스를 이용하여 보상하는 것이 바람직하다. 상술한 바와 같이 순환이동이 적용된 영역과 상이한 영역에서 시퀀스의 보상이 이루어지는 경우, 순환이동 정보를 나타내는 항목은 복소지수형태의 항목으로서 나타나는바, 추정된 ID를 가지는 시퀀스의 공액복소수 시퀀스와 간단히 곱하는 과정을 통해 순환 이동치 이외의 정보를 보상할 수 있다.In Equation 14, the M value is estimated through the maximum value of the IDFT values of the differential encoding values. Here, the τ component in Equation 13, which is an artificially added delay component in the process of calculating R (k-1) ^* R (k) (

) Becomes a constant irrespective of the value of k by the conjugate complex calculation, and therefore does not affect the estimation of the M value. In order to use this characteristic, when the received sequence is a sequence in which the cyclic shift is applied in the frequency domain, it is preferable to compensate using a conjugate complex sequence of the sequence estimated by the method described above in the time domain, and conversely, the received sequence. If cyclic shift is a sequence applied in the time domain, it is preferable to compensate using a conjugate complex sequence of the sequence estimated by the method described above in the frequency domain. As described above, when the sequence is compensated in a region different from the region to which the circular shift is applied, the item indicating the circular shift information appears as an item of a complex index type, and is a process of simply multiplying the conjugate complex sequence of the sequence having the estimated ID. Through this, information other than the cyclic shift value can be compensated.

In addition to the methods described above, cross-correlation is performed on all possible cases of the original sequence by the number of all cases that occur due to the cyclic shift, and then the sequence having the largest metric is obtained. Detection forms are also possible.

In addition, Equation 14 describes a case in which only one M value is estimated by detecting a maximum value of IDFTs performed on a differential sequence as an example. However, when the channel state is poor, only the maximum value is detected as described above. Rather, it is apparent to those skilled in the art that an index representing a value above a predetermined threshold can be extracted as a candidate and then the values can be processed in parallel.

As described above, after acquiring the ID information of the sequence, a step of obtaining a cyclic shift value is performed by multiplying the received sequence by a sequence that has performed a conjugate complex operation. This is expressed as the following equation.

)이 제거된 형태로 유도될 수 있으며, 상기 수학식 13에서 잡음성분을 무시할 경우 R'(k)는 채널응답(H(k))와 순환이동치 성분(

)만의 곱으로 나타낼 수 있다. 이와 같은 신호(R'(k))에 포함된 순환이동 정보를 보다 용이하게 검출하기 위해 다음과 같이 IFFT를 수행할 수 있다.Through this, R '(k) is a cyclic shift component of the received sequence R (k) (

) Can be derived in a removed form, and when the noise component is ignored in Equation 13, R '(k) is a channel response (H (k)) and a cyclic shift component (

Can be expressed as In order to more easily detect the cyclic shift information included in the signal R '(k), the IFFT may be performed as follows.

As a result of performing Equation 16, an impulse response in the time domain may be obtained.

FIG. 8 is a diagram illustrating a result indicating an impulse response of a wireless channel in a sequence received by a sequence analysis method according to an embodiment of the present invention.

As described above, the impulse response of the received sequence can be obtained through Equation 16, and FIG. 8 shows an example of the impulse response thus obtained. By analyzing this, it is possible to search the cyclic shift value, and obtain control information transmitted through the cyclic shift value.

On the other hand, unlike the case of searching for a cyclic shift value using the result of Equation 16, in the case of a multipath channel, a large number of errors may occur when the cyclic shift value is simply calculated through a single peak value as shown in FIG. . In this case, in consideration of the size of the section that can be spread due to the above-described multipath (hereinafter referred to as "Ng"), by grouping each sequence and applying a cyclic shift in the Ng interval, a method for reducing the error Can be considered That is, if the above-described multipath channel is not taken into account, the applicable circular shift value is 1 to N _fft. However, if the size of the section that can be spread due to the multipath is Ng, the cyclic shift value is 1, Ng, 2Ng, 3Ng, ... shows the optimal detection capability.

In this case, since retrieving the cyclic shift value at the receiving side is determined only in units of Ng as described above, the cyclic shift value can be determined by detecting a group representing the maximum by summing the power in each group unit of size Ng. This can be expressed as Equation 17 below.

Where N _fft is the length of the sequence in the FFT interval, Ng is the number of groups to which cyclic shift is applicable, and g is the group index (g = 0, 1, 2, .., N _fft / Ng).

Of course, the method for detecting the cyclic shift value through Equation 17 is preferably limited to a case in which a channel state is not good, such as a multipath channel. In the case of a channel that does not require consideration of an item such as multipath spreading, It is a matter of course that it is preferable to obtain a cyclic shift value through the detection of a single peak value as shown in Equation (16).

On the other hand, the performance of the sequence analysis method according to an embodiment of the present invention described above is as follows.

9 is a diagram showing a comparison of detection error rates in the case of using the sequence analysis method according to the embodiment of the present invention and in the case of the conventional sequence analysis method.

In FIG. 9, (1) Delayed S-SCH detects only a cyclic shift value through Equations 15 and 16 through a known sequence rather than using all the step configurations of the method proposed in the present invention. (2) Only GCL (IDFT) is a step of estimating the ID of a sequence without applying a cyclic shift instead of using all of the step configurations of the method proposed in the present invention, that is, the step corresponding to Equation (14). (3) Proposed shows a detection error rate when analyzing a sequence by performing all the steps of the sequence detection method according to an embodiment of the present invention.

Therefore, the above (3) is a method performed by combining the step configuration performed in (1) and (2), the overall performance of which is determined by the relatively poor performance of (1), (2), Fig. 9 In the figure, an example that depends on the performance of (2) is shown. Therefore, according to the present invention, it can be seen that there is no increase in the additional error rate even if each step configuration is combined in the prior art. In addition, according to the present invention, as described above, the cell ID may be increased by multiplying the number of cell IDs that can be generated in the prior art by the cyclic shift value. As an example, the inventors found that the number of cell IDs that can be generated in the conventional communication system is 40 when the length N of the sequence is 75. However, the present invention corresponds to 40 * 8 when 8 cyclic shift values are applicable according to the present invention. The simulation can confirm that 320 cell IDs can be generated and no additional error rate increases.

The detailed description of the preferred embodiments of the invention disclosed as described above is provided to enable any person skilled in the art to make and practice the invention. Although the above has been described with reference to the preferred embodiments of the present invention, those skilled in the art will variously modify and change the present invention without departing from the spirit and scope of the invention as set forth in the claims below. I can understand that you can. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

According to the synchronous channel structure according to an embodiment of the present invention as described above, it is possible to obtain the synchronization information of good quality in both the synchronous network and the asynchronous network, the synchronization acquisition and asynchronous by the autocorrelation mainly used in the synchronous network By performing the synchronization acquisition by the cross-correlation mainly performed in the network, the effect of improving the accuracy of the obtained synchronization information is obtained.

In addition, according to the synchronization acquisition method and the cell search method according to an embodiment of the present invention, it is possible to determine whether a network in which communication is performed is synchronous or asynchronous, and to select an appropriate synchronization acquisition method, and P-SCH and S- By using the repetition structure having the shortest length included in the SCH, it is possible to reduce the amount of computation required for the acquisition of synchronization, and the cell search method based on this is based on the synchronization information having such accuracy. Can be obtained.

In addition, according to the method of applying a sequence according to an embodiment of the present invention, additional information may be transmitted to a sequence inserted into each sync channel, and the accuracy of the information transmitted by controlling the type of the sequence inserted into each sync channel. And it has the effect of extending the kind.

In addition, the sequence analysis method according to an embodiment of the present invention has an effect of extending the amount of control information that can be transmitted and analyzed without increasing an additional error rate as compared with the related art.

Claims (20)

A main synchronization channel including a sequence commonly used in a communication network and including a repetition structure of the sequence in a time domain; And And an auxiliary synchronization channel including a sequence for transferring information other than control information included in the primary synchronization channel. The method of claim 1, And the auxiliary synchronization channel also includes a repeating structure of a sequence in the time domain. The method according to claim 1 or 2, The repeating structure is a synchronization channel structure formed by inserting a specific sequence every predetermined period in the frequency domain. The method according to claim 1 or 2, And the repetition structure is achieved by repeatedly inserting a specific sequence directly in the time domain. The method according to claim 1 or 2, And the sequences of the primary sync channel and the auxiliary sync channel include cyclic shift information. A method for acquiring synchronization using a synchronization channel including a primary synchronization channel and an auxiliary synchronization channel, wherein the primary synchronization channel includes a sequence commonly used in a communication network and has a structure including a repetition structure of a sequence in a time domain. To Determining whether the network over which the communication is made is synchronous; And If the network is a synchronous network, acquiring synchronization through the repeating structure of the primary synchronization channel. The method of claim 6, The auxiliary synchronization channel also includes a repetition structure of a sequence in the time domain, Acquiring the synchronization, Selecting a repetition structure of the shortest sequence among the repetition structures of the primary synchronization channel and the auxiliary synchronization channel; And And obtaining synchronization through autocorrelation of the selected shortest repetition structure. The method according to claim 6 or 7, And increasing the accuracy of the obtained synchronization using the common sequence of the primary synchronization channel. A method for acquiring synchronization using a synchronization channel including a primary synchronization channel and an auxiliary synchronization channel, wherein the primary synchronization channel includes a sequence commonly used in a communication network, and has a structure including a repetition structure of a sequence in a time domain. To Determining whether the communication network over which communication is made is synchronous; And If the communication network is an asynchronous network, acquiring synchronization through the common sequence included in the primary synchronization channel; The method of claim 9, And using the repetition structure of the primary synchronization channel or the auxiliary synchronization channel to increase the accuracy of the obtained synchronization. A method of applying a sequence to be inserted into a synchronization channel including a primary synchronization channel and a secondary synchronization channel, the primary synchronization channel having a structure including a repetition structure of a sequence in a time domain, Generating a sequence to be applied to the primary sync channel and the auxiliary sync channel; And Applying a cyclic shift to the sequences in the time domain or frequency domain. The method of claim 11, Applying the circular movement, Applying a predetermined delay value to an index of a first region, the selected one of the time domain or the frequency domain of the sequences; And Applying a modulation function based on the length of the sequences. The method of claim 11, The applying the cyclic shift comprises multiplying the sequences by a complex exponential function in a second region, which is any one of the time domain or the frequency domain. The method according to any one of claims 11 to 13, And applying different cyclic shifts to the primary sync channel and the auxiliary sync channel in applying the cyclic shift. The method according to any one of claims 11 to 13, Generating a sequence to be applied to the primary synchronization channel and the auxiliary synchronization channel, wherein the sequence applied to the auxiliary synchronization channel is generated as a repetitive sequence of the sequence applied to the primary synchronization channel. The method according to any one of claims 11 to 13, In the generating of the sequence to be applied to the primary synchronization channel and the auxiliary synchronization channel, the sequence is applied by dividing and applying one sequence into a sequence to be applied to the primary synchronization channel and a sequence to be applied to the auxiliary synchronization channel. Way. The method according to any one of claims 11 to 13, Generating a sequence to be applied to the primary synchronization channel and the auxiliary synchronization channel; and a sequence to be applied to the primary synchronization channel and a sequence to be applied to the auxiliary synchronization channel are sequences of different types. A method for analyzing a sequence in which a cyclic shift is applied to a sequence inserted into a primary sync channel and a secondary sync channel at a receiving end of a communication system, Obtaining ID information of the sequence by generating a differential sequence of the received sequence; And Compensating for the received sequence and obtaining a cyclic shift of the received sequence by multiplying the conjugated complex sequence of the selected sequence with the obtained sequence ID information. The method of claim 18, The acquiring of the cyclic shift value may include obtaining the cyclic shift value by compensating the received sequence in the time domain when the received sequence is a sequence in which the cyclic shift is applied in the frequency domain. And obtaining the cyclic shift value by compensating the received sequence in the frequency domain when the received sequence is a sequence in which cyclic shift is applied in the time domain. The method of claim 18 or 19, When the application of the circular shift is applied in group units, the obtaining of the circular shift value may include: Summing power in each delay group of the sequence for which the received sequence is compensated; And Selecting a group representing the maximum of the summed powers.

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