JP2011166772A - Method and device for initial cell search - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a initial cell search method and a device thereof. <P>SOLUTION: The initial cell search method includes; a primary synchronization sequence (PSS) detection step; a first consolidation step; a first metric value calculation step; a first threshold comparison step; a first control step; a first calculation step; a carrier frequency offset compensation step; a secondary synchronization sequence (SSS) detection step; a second consolidation step; a second metric value calculation step; a second threshold comparison step; a second control step; and a second calculation step. According to the technique, it is possible to access to a network rapidly under various channel conditions by adjusting the consolidation frame amount of PSS and SSS voluntarily in response to conditions of a channel. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  Embodiments discussed herein relate to the field of wireless communication technology, and more particularly, to an initial cell search method and apparatus in a wireless communication system for a long term evolution (LTE) system.

  When a mobile terminal is powered on in an LTE wireless communication system or the like, a cell search process must first be executed. In the cell search process, the mobile terminal needs to acquire timing, frequency synchronization, and cell ID (Cell ID). As shown in FIG. 1, LTE cell search is based on two downlink signals, a primary synchronization sequence (hereinafter referred to as PSS) and a secondary synchronization sequence (hereinafter referred to as SSS). Do it. Therefore, LTE cell search includes two stages. The first stage is a PSS detection stage, in which a PSS ID is detected, timing synchronization (5 ms) is performed, and a carrier frequency offset (hereinafter abbreviated as CFO) must be estimated. The second stage is the SSS detection stage.Based on the detection result in the first stage, the group ID (cyclic ID), the type of cyclic prefix (hereinafter abbreviated as CP), and the frame timing are determined. Must get.

  SSS detection is performed in the frequency domain, and CFO causes inter-carrier interference (hereinafter abbreviated as ICI) in the frequency domain, and ICI adversely affects the function of SSS detection. Compensate for the CFO based on the CFO estimated in one step.

  In the PSS and SSS detection stages, a better detection function is realized by combining multiple frames over time to suppress noise and resist channel weakness.

  Hereinafter, an existing cell search method will be described with reference to FIG. FIG. 2 is a flowchart illustrating an existing initial cell search method. First, in step S201, an initial value (k = 0) is set. Next, in step S203, PSS detection is performed by calculating a cross-correlation between the received signal and the locally generated PSS signal. After that, in step S205, the correlation value calculated in the PSS detection process in step S203 is synthesized according to the fixed number of synthesis m. Next, in step S207, an estimated value of PSS ID, timing, and CFO is calculated from the combined correlation value calculated in step S205. Thereafter, in step S209, CFO compensation is performed based on the CFO estimated value calculated in step S207. Thereafter, in step S211, in the frequency domain, SSS detection is performed by calculating a cross-correlation between the received equalized SSS signal and the locally generated SSS signal. Specifically, in step S211, based on the timing calculated in step S207, find the SSS signal from the CFO compensated received signal, and after estimating the channel response from the PSS ID calculated in step S207, the frequency In the region, SSS detection is performed by equalizing the SSS signal based on the estimated channel response and performing a cross-correlation calculation between the equalized SSS signal and the locally generated SSS signal. Thereafter, in step S213, the correlation values calculated in the SSS detection process in step S211 are combined in accordance with the fixed combination number n. Thereafter, in step S215, it is determined whether or not the combined correlation value calculated in step S213 exceeds a predetermined threshold value. If the determination result in step S215 is “NO”, in step S217, CFO compensation is reset and k is incremented. Thereafter, in step S219, it is determined whether k is less than the maximum retry number trymax. If the determination result in step S219 is “YES”, the process returns to step S203 to start the cell search again. If the determination result in step S219 is not “YES”, failure of the initial cell search is determined in step S221, the process exits from the initial cell search process, and then shifts to execution of another process (for example, initial AGC). On the other hand, if the determination result in step S215 is “YES”, in step S223, the group ID, CP type, and frame timing are calculated from the combined correlation value calculated in step S213. A cell ID is calculated from the group ID and the PSS ID calculated in step S207.

  As described above, according to the existing cell search method, a fixed number of synthesis (m and n in FIG. 2) is used. If the noise is large and the channel is relatively weak, a good detection function must be realized by setting m and n to large numerical values and synthesizing more frames. However, when the channel condition is good, it is not necessary to fix m and n to large numerical values, and the cell search time is unnecessarily increased. Similarly, if m and n are fixed to small numerical values, the first stage detection quality cannot be guaranteed if the channel condition is bad. As a result, SSS cannot be detected due to errors in timing detection and CFO estimation, which increases the time for cell search.

  Hereinafter, in order to make the disclosed apparatus and method understandable, the disclosed apparatus and method will be briefly described. However, the simple explanation is not exhaustive. The brief description is not intended to identify key points or critical parts of the disclosed apparatus and method, nor is it intended to limit the scope of the disclosed apparatus and method. However, in order to give some concepts in a simple form, this is used as a front part of a more detailed explanation later.

  In view of the above situation in the existing technology, the disclosed apparatus and method can quickly access the network under various channel conditions by voluntarily adjusting the number of combined frames of PSS and SSS according to the channel conditions. It is an object to provide an initial cell search method and apparatus therefor.

  According to one aspect of the method, a primary synchronization sequence PSS detection step for performing PSS detection by performing a cross-correlation calculation between a received signal and a locally generated PSS signal, and a first synthesis number m (m is an initial value) The first synthesis step for synthesizing the correlation value calculated in the PSS detection step and the first synthesis correlation value calculated in the first synthesis step according to A first metric value calculating step for calculating a first metric value to be evaluated, and a first threshold value comparison for comparing the first metric value calculated in the first metric value calculating step with a first threshold value And when the first metric value is less than or equal to the first threshold, the first synthesis number m is gradually increased until the first metric value is greater than the first threshold, and the PSS detection step, First synthesis step and first metric value meter The first control step for repeatedly executing the step and the first threshold value comparison step, and the first combined correlation value calculated in the first combining step, the PSS ID, the timing, and the carrier frequency A first calculation step for calculating an estimated value of the offset CFO, a CFO compensation step for performing CFO compensation according to the CFO estimation value calculated in the first calculation step, and the received post-equalization received in the frequency domain Depending on the secondary synchronization sequence SSS detection step that performs SSS detection by performing cross-correlation calculation between the SSS signal and the locally generated SSS signal, and the second synthesis number n (n is an integer whose initial value is 0) The second metric for evaluating the ability of SSS detection from the second synthesis step for synthesizing the correlation value calculated in the SSS detection step and the second synthesis correlation value calculated in the second synthesis step The second metric that calculates the value A second threshold value comparing step for comparing the second metric value calculated in the second metric value calculating step with the second threshold value, and the second metric value is equal to or less than the second threshold value. In this case, until the second metric value becomes larger than the second threshold, the second synthesis number n is increased, and the SSS detection step, the second synthesis step, the second metric value calculation step, A second threshold comparison step; a second control step for repeatedly executing; and a second combined correlation value calculated in the second combining step to calculate a group ID and the calculated group ID And an initial cell search method including a second calculation step of calculating a cell ID from the PSS ID calculated in the first calculation step.

  According to one aspect of the apparatus, a primary synchronization sequence PSS detection unit that performs a cross-correlation calculation between a received signal and a locally generated PSS signal to perform PSS detection, and a first synthesis number m (m has an initial value of 0 The first synthesis unit that synthesizes the correlation value calculated by the PSS detection unit according to the first and the first synthesis correlation value calculated by the first synthesis unit, and evaluates the ability of PSS detection. A first metric value calculation unit for calculating a first metric value for, a first threshold comparison unit for comparing the first metric value calculated by the first metric value calculation unit with a first threshold value, and When the first metric value is less than or equal to the first threshold, the first synthesis count m is increased until the first metric value is greater than the first threshold, and the PSS detection unit and the first The synthesis unit and the first The first control unit that repeatedly executes the processing in the trick calculation unit, the first threshold comparison unit, the first synthesis correlation value calculated by the first synthesis unit, the PSS ID, the timing, Received in the frequency domain, a first calculation unit that calculates the carrier frequency offset CFO estimate, a CFO compensation unit that performs CFO compensation according to the CFO estimate calculated by the first calculation unit, and A secondary synchronization sequence SSS detection unit that performs SSS detection by performing a cross-correlation calculation between the SSS signal after equalization and the locally generated SSS signal, and the second synthesis number n (n has an initial value of 0) The second synthesis unit that synthesizes the correlation value calculated by the SSS detection unit and the second synthesis correlation value calculated by the second synthesis unit according to the integer). A second metric value calculation unit for calculating a second metric value for evaluating the second metric value and a second threshold value for comparing the second metric value calculated by the second metric value calculation unit with the second threshold value When the comparison unit and the second metric value are less than or equal to the second threshold, the second synthesis number n is increased until the second metric value is greater than the second threshold, and the SSS detection unit A second synthesis unit, a second metric value calculation unit, a second control unit that repeatedly executes the processing in the second threshold comparison unit, and a second calculation unit calculated by the second synthesis unit An initial cell search device comprising: a group ID calculated from the combined correlation value; and a second calculation unit that calculates a cell ID from the calculated group ID and the PSS ID calculated by the first calculation unit. Is given The

  According to another aspect, a computer program product for implementing the above initial cell search method is provided.

  According to another aspect, a computer readable medium storing computer program code for implementing the above initial cell search method is provided.

  The disclosed apparatus and method may be better understood with reference to the following description taken in conjunction with the accompanying drawings. In all the drawings, the same or similar parts are indicated by the same or similar reference numerals. The drawings are included herein and become a part of this specification, together with the following detailed description, and further illustrate preferred embodiments by way of example and interpret the principles and advantages of the disclosed apparatus and method. Use for.

  Those skilled in the art should understand that the elements in the drawings are shown merely for simplicity and clarity and have not necessarily been drawn to scale. For example, the size of certain elements in the drawings may be larger than other elements to help improve understanding of embodiments of the disclosed apparatus and method.

It is a schematic diagram which shows the PSS and SSS signal in a LTE system. It is a flowchart which shows the existing initial cell search method. 5 is a flowchart illustrating an initial cell search method according to an embodiment. It is a block diagram which shows the structure of the initial stage cell search apparatus by an Example. It is a figure which shows the simulation result of cell search time.

  Hereinafter, representative examples will be described with reference to the drawings. For the sake of clarity and conciseness, not all features of an actual embodiment are described in the specification. In developing such actual implementations, decisions specific to the actual implementations must be made to achieve the developer's specific objectives, such as regulatory requirements for systems and services. It must be met and its restrictive conditions are different in different embodiments. And while the development work can be complex and time consuming, such development is merely a task to be performed for those skilled in the art who would benefit from the disclosed content.

  Here, in order to prevent the disclosed apparatus and method from being obscured by unnecessary details, in the drawings, the structure and / or structure of the apparatus having a close relationship with the technology related to the disclosed apparatus and method. Only the processing steps are shown, and other details that are not closely related are omitted.

  Hereinafter, an initial cell search method according to a specific embodiment will be described in detail.

  FIG. 3 is a flowchart illustrating an initial cell search method according to the embodiment.

  First, in step S301, initial values of the first synthesis number m and the second synthesis number n are set (m = 0, n = 0).

  Thereafter, in step S303, cross-correlation between the received signal and the locally generated PSS signal is calculated to perform PSS detection. Therefore, it is preferable to use a partial correlation algorithm in consideration of the influence of the CFO on PSS detection. For example, an example relating to partial correlation divided into three parts is as shown in the following equation.

  Here, id = 0,1,2; k∈ [0,9599], r (n, i) is the received signal of the i-th half frame (5 ms), and PSS (id, n) is This is a locally generated PSS signal. In a 20MHz bandwidth system, the search window for PSS detection is 5ms, and after 16 times downsampling, the search window has 9600 sample points, so k is in the [0,9599] range It is a value in. Since the PSS sequence has 128 sample points, when divided into three parts, each part has floor (128/3) = 42 sample points. floor (x) is a floor function.

  Furthermore, in a TDD system, it is preferable to use a correlation algorithm based on normalization because uplink interference has a significant effect on PSS detection. Examples of normalization factors include the following.

  The normalized correlation value is shown in the following equation (3).

After that, in step S305, the correlation values calculated in the PSS detection process in step S303 are combined according to the first combination count m. For example, the first combined correlation value C _av (id, k, m) can be obtained by combining according to the following equation.

Alternatively, the first composite correlation value C _av (id, k, m) can be obtained according to the following equation.

  Thereafter, in step S307, a first metric value for evaluating the capability of PSS detection is calculated from the first combined correlation value calculated in step S305. Specifically, a person skilled in the art can calculate the first metric value according to various metric functions that can express the ability of PSS detection when the number of synthesis is different, depending on the specific design. In the following, two preferred embodiments of the metric function will be described. As will be appreciated by those skilled in the art, the disclosed method may employ functions other than the following metric functions.

  The first example is as follows.

  A second example is as follows.

Here, k _max (id) = argmax (C _av (id, k, m)), and W _PSS is the number of sample points in the preset calculation window.

  Thereafter, in step S309, it is determined whether or not the first metric value calculated in step S307 exceeds the first threshold th1. Specifically, if Metric1 (id, m)> th1 for any of the PSS ID indexes id, it can be recognized that the number of synthesis (m) of PSS detection is sufficient, and the determination in step S309 The result is “YES”. Unless Metric1 (id, m)> th1, the determination result in step S309 is “NO”.

  If the determination result in step S309 is “NO”, in step S311, m is incremented by 1, for example, and then in step S313, it is determined whether m is less than a preset first maximum number of synthesis M. To do.

  If the decision result in the step S313 is “YES”, the process returns to the step S303 to continue the PSS detection process. If the determination result in step S313 is not “YES”, it is determined in step S315 that the initial cell search process has failed, the process exits from the initial cell search process, and then proceeds to execution of another process (for example, AGC or the like). ).

  On the other hand, if the determination result in step S309 is “YES”, in step S317, an estimated value of PSS ID, timing, and CFO is calculated from the first composite correlation value calculated in step S305. An example of a method for calculating the PSS ID, timing, and CFO when the correlation value corresponding to only one PSS ID exceeds the threshold is as follows.

Here, id _select is the calculated PSS ID, k _select is the calculated timing, δ ^ _f is the calculated CFO estimated value, and Ts is the sampling period after downsampling 16 times is there.

  Thereafter, in step S319, CFO compensation is performed based on the CFO estimated value calculated in step S317.

  Thereafter, in step S321, cross-correlation between the equalized SSS signal received in the frequency domain and the locally generated SSS signal is calculated to perform SSS detection. Specifically, in step S321, based on the timing calculated in step S317, find the SSS signal from the CFO compensated received signal, estimate the channel response based on the PSS ID calculated in step S317, Thereafter, the SSS signal is equalized based on the channel response estimated in the frequency domain, and the SSS detection is performed by calculating the cross-correlation between the equalized SSS signal and the locally generated SSS signal. One example is as follows.

Here, r _SSS (k, CpType, i) is a sequence in the SSS frequency domain after equalization received in the i-th half frame based on different CP types (normal CP or long CP). , SSS (GroupId, FrameTim, k) is a locally generated SSS sequence, GroupId∈ [0, 167], k∈ [0, 61], and FrameTime is the current half-frame in one frame data Indicates whether it is the first half frame or the second half frame. Therefore, 672 (168 (GroupId) × 2 (CpType) × 2 (FrameTim) = 672) correlation values can be obtained according to Equation (9).

Thereafter, in step S323, the correlation values calculated in the SSS detection process in step S321 are combined according to the second combination number n. For example, the second composite correlation value S _av (GroupId, CpType, FrameTime, n) is obtained by combining according to the following expression.

  Thereafter, in step S325, a second metric value for evaluating the SSS detection capability is calculated from the second combined correlation value calculated in step S323. Specifically, a person skilled in the art can calculate the second metric value using various metric functions that can express the ability of SSS detection when the number of synthesis is different, depending on the specific design. In the following, two preferred examples of metric functions will be described, but as will be appreciated by those skilled in the art, the disclosed method may employ functions other than the following metric functions.

  The first example is as follows.

  A second example is as follows.

  Thereafter, in step S327, it is determined whether or not the second metric value calculated in step S325 exceeds the second threshold th2. Specifically, if Metric2 (n)> th2, it can be recognized that the number of synthesis (n) of SSS detection is sufficient.

  If the determination result in step S327 is “NO”, n is incremented in step S329, and then, in step S331, it is determined whether n is less than a preset second maximum number of synthesis N.

  If the determination result in step S331 is “YES”, the process returns to step S321 to continue the SSS detection process, otherwise the CFO compensation is reset in step S333, and then the process returns to step S301 to perform the initial cell search process. Start again.

  On the other hand, if the determination result in step S327 is “YES”, in step S335, a group ID is calculated from the second composite correlation value calculated in step S323, and the calculated group ID is calculated in step S317. The initial cell search process is completed by calculating a cell ID from the obtained PSS ID.

  In the above, the initial cell search method according to the embodiment has been described in detail with reference to the drawings. However, for those skilled in the art, the flowchart shown in FIG. 3 is only an example, and FIG. It is self-evident that modifications can be made to the process of the method shown in. For example, if necessary, the execution order of some steps in the method shown in FIG. 3 can be adjusted, or some processing steps can be deleted or added.

  Hereinafter, an initial cell search apparatus according to an embodiment will be described in detail with reference to the drawings. FIG. 4 is a block diagram of an initial cell search apparatus 400 according to the embodiment. Here, for the sake of brevity, only the portions closely related to the disclosed apparatus are shown. In the initial cell search device 400, the initial cell search method described with reference to FIG. 3 can be executed.

  As shown in FIG. 4, the initial cell search device 400 includes a receiving unit 401, a PSS detection unit 403, a first synthesis unit 405, a first metric value calculation unit 407, and a first threshold comparison unit 409. The first control unit 411, the first calculation unit 413, the CFO compensation unit 415, the SSS detection unit 417, the second synthesis unit 419, the second metric value calculation unit 421, the second Threshold comparison unit 423, second control unit 425, and second calculation unit 427 can be included.

  Among them, after receiving the signal via the antenna, the receiving unit 401 performs preprocessing such as changing the signal to baseband on the received signal, and then converts the analog signal into a digital signal. , Processing such as filtering and downsampling.

  The PSS detection unit 403 performs PSS detection by performing cross-correlation calculation between the reception signal output from the reception unit 401 and the locally generated PSS signal.

  The first synthesis unit 405 synthesizes the correlation value calculated by the PSS detection unit 403 according to the first synthesis number m. The initial value of M is the integer 0.

  The first metric value calculating unit 407 calculates a first metric value for evaluating the capability of PSS detection from the first combined correlation value calculated by the first combining unit 405.

  The first threshold value comparison unit 409 compares the first metric value calculated by the first metric value calculation unit 407 with the first threshold value.

  When the first metric value is equal to or less than the first threshold, the first control unit 411 increases the first synthesis count m until the first metric value exceeds the first threshold, and the PSS The processes in the detection unit 403, the first synthesis unit 405, the first metric calculation unit 407, and the first threshold comparison unit 409 are repeatedly executed.

  The first calculation unit 413 calculates the PSS ID, the timing, and the estimated value of the CFO from the first combined correlation value calculated by the first combining unit 405.

  The CFO compensation unit 415 performs CFO compensation according to the CFO estimated value calculated by the first calculation unit 413.

  The SSS detection unit 417 performs SSS detection by performing a cross-correlation calculation between the received equalized SSS signal and the locally generated SSS signal in the frequency domain.

  The second synthesis unit 419 performs synthesis on the correlation value calculated by the SSS detection unit 417 according to the second synthesis number n. The initial value of n is the integer 0.

  The second metric value calculating unit 421 calculates a second metric value for evaluating the capability of SSS detection from the second combined correlation value calculated by the second combining unit 419.

  The second threshold value comparison unit 423 compares the second metric value calculated by the second metric value calculation unit 421 with the second threshold value.

  If the second metric value is equal to or less than the second threshold, the second control unit 425 increments the second synthesis number n until the second metric value exceeds the second threshold, and SSS The processes in the detection unit 417, the second synthesis unit 419, the second metric value calculation unit 421, and the second threshold comparison unit 423 are repeatedly executed.

  The second calculation unit 427 calculates a group ID from the second combined correlation value calculated by the second combining unit 419, and calculates the group ID and the PSS calculated by the first calculating unit 413. Cell ID is calculated from ID.

  In a specific embodiment, the first control unit 411 increases m and then compares m with the first maximum number of synthesis M. M is an integer greater than 0. If m exceeds M, it is determined that the initial cell search process has failed, and the initial cell search process is exited.

  In a specific embodiment, the second control unit 425 increases n and then compares n with the second maximum number of synthesis N. N is an integer greater than 0. If n exceeds N, reset CFO compensation and start the initial cell search process again.

  In the above, the specific and / or selectable processing processes of each member of the initial cell search device 400 have been described with reference to the flowchart of the method. Therefore, in order to avoid redundant description, the operations and processing processes will be described. Is omitted.

  Here, the structure of initial cell search device 400 shown in FIG. 4 is merely an example, and those skilled in the art can change the block diagram shown in FIG.

  FIG. 5 shows a complementary cumulative distribution function (abbreviated as CCDF) of the cell search time calculated by simulation based on the above technical idea. In the above simulation, th1 = 13dB, M = 16, th2 = 9dB, N = 6, and the channel is ETU300Hz. When there is one base station, SNR = -5 dB, and when there are three base stations, the SNRs of the three base stations are -5 dB, -7 dB, and -7 dB, respectively, and the cell IDs of the three base stations Are 109, 120, and 113, respectively, and the relative delays of the three base stations are 0, 0, and CP / 2. As shown in FIG. 5, in the case of one base station, the cell search time of 90% is 35 ms, but in the case of three base stations, the cell search time of 90% is 45 ms. Thus, according to the disclosed apparatus and method, a network can be accessed relatively quickly.

  It is obvious that each operation process according to the disclosed method can be realized in the form of a computer-executable program stored in a readable storage medium of various facilities.

  Another object of the disclosed apparatus and method is to directly or indirectly provide a recording medium storing the executable program code to the system or equipment, and to provide a computer or central processing unit in the system or equipment. This can be realized by causing the CPU to read and execute the above program. At this time, as long as the system or the facility has a function capable of executing the program, the disclosed method is not limited to the program, and the program can be executed in any format, for example, a target program or an interpreter. Alternatively, it can be in the form of a program provided to the operation system.

  The storage media that can be read by the above equipment include various memories and storage units, semiconductor equipment, disk units such as optical disks, disks, and magneto-optical disks, and other media that can store information. It is not limited.

  The disclosed method can also be realized by connecting a computer to the relevant side in the Internet, downloading and installing the computer program code, and executing the program.

  In the disclosed apparatus and method, each member or step can be disassembled and / or recombined. Such decomposition and / or recombination is equivalent to the disclosed method and invention. In addition, although the steps for performing the above-described series of processes can be performed in the order of description or the order of time, it cannot be said that they must be performed in the order of time. Some steps can be performed in parallel or independently of each other.

  Although the embodiments have been described with reference to the drawings, the embodiments described above are for explaining the disclosed apparatus and method, and are not intended to limit the disclosed apparatus and method. Those skilled in the art can make various modifications and changes to the above-described embodiments without departing from the spirit and scope of the disclosed apparatus and method. Accordingly, the scope of protection of the disclosed apparatus and method is limited by the claims and their equivalent meanings.

  Similar to the description of the above embodiments, the technical idea covered by the disclosed apparatus and method includes, but is not limited to, the following.

(Appendix 1)
Primary synchronization sequence PSS detection step for performing PSS detection by performing cross-correlation calculation between the received signal and the locally generated PSS signal,
A first synthesis step of synthesizing the correlation values calculated in the PSS detection step according to a first synthesis number m (m is an integer whose initial value is 0);
A first metric value calculating step for calculating a first metric value for evaluating the capability of PSS detection from the first combined correlation value calculated in the first combining step;
A first threshold comparing step for comparing the first metric value calculated in the first metric value calculating step with a first threshold;
If the first metric value is less than or equal to the first threshold value, the first synthesis number m is increased until the first metric value exceeds the first threshold value, and the PSS detection is performed. A first control step that repeatedly executes a step, the first synthesis step, the first metric value calculation step, and the first threshold value comparison step;
From the first combined correlation value calculated in the first combining step, a first calculation step of calculating an estimated value of PSS ID, timing, and carrier frequency offset CFO;
CFO compensation step for performing CFO compensation according to the estimated value of CFO calculated in the first calculation step;
In the frequency domain, the secondary synchronization sequence SSS detection step for performing SSS detection by performing cross-correlation calculation between the received SSS signal after equalization and the locally generated SSS signal,
A second synthesis step of synthesizing the correlation values calculated in the SSS detection step according to a second synthesis number n (n is an integer whose initial value is 0);
A second metric value calculating step for calculating a second metric value for evaluating the capability of SSS detection from the second combined correlation value calculated in the second combining step;
A second threshold comparing step for comparing the second metric value calculated in the second metric value calculating step with a second threshold;
When the second metric value is less than or equal to the second threshold value, the second synthesis number n is increased until the second metric value exceeds the second threshold value, and the SSS detection is performed. A second control step that repeatedly executes a step, the second synthesis step, the second metric value calculation step, and the second threshold value comparison step;
A group ID is calculated from the second combined correlation value calculated in the second combining step, and a cell ID is calculated from the calculated group ID and the PSS ID calculated in the first calculating step. A second calculation step of calculating, an initial cell search method.

(Appendix 2)
In the initial cell search method according to attachment 1,
In the first control step, after increasing the first synthesis number m, the first synthesis number m is compared with a first maximum synthesis number M (M is an integer greater than 0), and the first The initial cell search method is characterized in that if the combination number m exceeds the first maximum combination number M, the initial cell search process is determined to have failed, and the initial cell search process is exited.

(Appendix 3)
In the initial cell search method described in Appendix 1,
In the second control step, after increasing the second combination number n, the second combination number n is compared with a second maximum combination number N (N is an integer greater than 0), and the second combination number n is compared with the second combination number n. An initial cell search method comprising: resetting the CFO compensation and restarting the initial cell search process when the number n of synthesis exceeds the second maximum number of synthesis N.

(Appendix 4)
In the initial cell search method described in Appendix 1,
In the first metric value calculating step, the first metric value is calculated according to the following equation:

Here, id is a PSS ID index number, C _av (id, k, m) is the first composite correlation value, and K _max (id) = argmax (C _av (id, k, m)) W _samples is the number of sample points in the search window for PSS detection, and W _PSS is the number of sample points in the first metric value calculation window.

(Appendix 5)
In the initial cell search method described in Appendix 1,
In the first metric value calculating step, the first metric value is calculated according to the following equation:

Here, id is a PSS ID index number, C _av (id, k, m) is the first composite correlation value, and K _max (id) = argmax (C _av (id, k, m)) And W _samples is the number of sample points in the search window for PSS detection.

(Appendix 6)
In the initial cell search method described in Appendix 1,
In the second metric value calculating step, the second metric value is calculated according to the following equation:

Here, GroudId is a group ID index, CpType indicates the type of cycle prefix, FrameTim indicates whether the current half frame is the first half frame or the second half frame in one frame data, and S _av (GroupId, CpType, FrameTime , n) is the second composite correlation value;

An initial cell search method, characterized by:

(Appendix 7)
In the initial cell search method described in Appendix 1,
In the second metric value calculating step, the second metric value is calculated according to the following equation:

Here, GroupId is a group ID index, CpType indicates the type of cycle prefix, FrameTim indicates whether the current half frame is the first half frame or the second half frame in one frame data, and S _av (GroupId, CpType, FrameTime , n) is the second composite correlation value;

An initial cell search method, characterized by:

(Appendix 8)
A primary synchronization sequence PSS detection unit that performs PSS detection by performing cross-correlation calculation between the received signal and the locally generated PSS signal,
A first synthesis unit that synthesizes a correlation value calculated by the PSS detection unit according to a first synthesis number m (m is an integer whose initial value is 0);
A first metric value calculating unit for calculating a first metric value for evaluating the capability of PSS detection from the first combined correlation value calculated by the first combining unit;
A first threshold comparison unit that compares the first metric value calculated by the first metric value calculation unit with a first threshold;
If the first metric value is less than or equal to the first threshold value, the first synthesis number m is increased until the first metric value exceeds the first threshold value, and the PSS detection is performed. A first control unit that repeats processing in a unit, the first synthesis unit, the first metric calculation unit, and the first threshold comparison unit;
From the first combined correlation value calculated by the first combining unit, a first calculation unit for calculating a PSS ID, a timing, and an estimated value of a carrier frequency offset CFO;
A CFO compensation unit that performs CFO compensation according to the estimated value of the CFO calculated by the first calculation unit, and a cross-correlation between the received equalized SSS signal and the locally generated SSS signal in the frequency domain Secondary synchronization sequence SSS detection unit that performs calculation and performs SSS detection;
A second synthesis unit for synthesizing the correlation values calculated by the SSS detection unit according to a second synthesis number n (n is an integer whose initial value is 0);
A second metric value calculating unit for calculating a second metric value for evaluating the capability of SSS detection from the second combined correlation value calculated by the second combining unit;
A second threshold comparison unit that compares the second metric value calculated by the second metric value calculation unit with a second threshold;
When the second metric value is less than or equal to the second threshold value, the second synthesis number n is increased until the second metric value exceeds the second threshold value, and the SSS detection is performed. A second control unit that repeatedly executes processing in a unit, the second synthesis unit, the second metric value calculation unit, and the second threshold comparison unit;
A group ID is calculated from the second combined correlation value calculated by the second combining unit, and a cell ID is calculated from the calculated group ID and the PSS ID calculated by the first calculating unit. An initial cell search device comprising: a second calculation unit that:

(Appendix 9)
In the initial cell search device according to appendix 8,
The first control unit, after increasing the first synthesis number m, compares the first synthesis number m with a first maximum synthesis number M (M is an integer greater than 0), and An initial cell search device that determines that the initial cell search process is unsuccessful and exits from the initial cell search process when the combination number m exceeds the first maximum combination number M.

(Appendix 10)
In the initial cell search device according to appendix 8,
The second control unit, after increasing the second combination number n, compares the second combination number n with a second maximum combination number N (N is an integer greater than 0), and compares the second combination number n. An initial cell search device that resets CFO compensation and restarts an initial cell search process when the number n of synthesis exceeds the second maximum number of synthesis N.

(Appendix 11)
In the initial cell search device according to appendix 8,
The first metric value calculation unit calculates the first metric value according to the following equation:

Here, id is a PSS ID index number, C _av (id, k, m) is the first composite correlation value, and K _max (id) = argmax (C _av (id, k, m)) W _samples is the number of sample points in the search window for PSS detection, and W _PSS is the number of sample points in the first metric value calculation window.

(Appendix 12)
In the initial cell search device according to appendix 8,
The first metric value calculation unit calculates the first metric value according to the following equation:

Here, id is a PSS ID index number, C _av (id, k, m) is the first composite correlation value, and K _max (id) = argmax (C _av (id, k, m)) And W _samples is the number of sample points in the search window for PSS detection.

(Appendix 13)
In the initial cell search device according to appendix 8,
The second metric value calculation unit calculates the second metric value according to the following equation:

Here, GroupId is a group ID index, CpType indicates the type of cycle prefix, FrameTim indicates whether the current half frame is the first half frame or the second half frame in one frame data, and S _av (GroupId, CpType, FrameTime , n) is the second composite correlation value;

An initial cell search device characterized in that:

(Appendix 14)
In the initial cell search device according to appendix 8,
The second metric value calculation unit calculates the second metric value according to the following equation:

Here, GroupId is a group ID index, CpType indicates the type of cycle prefix, FrameTim indicates whether the current half frame is the first half frame or the second half frame in one frame data, and S _av (GroupId, CpType, FrameTime , n) is the second composite correlation value;

An initial cell search device characterized in that:

(Appendix 15)
A computer program storing instruction codes for causing a computer to execute the method according to any one of appendices 1 to 7.

(Appendix 16)
A readable storage medium on which the computer program according to attachment 15 is recorded.

400 Initial cell search device 401 Reception unit 403 PSS detection unit 405 First synthesis unit 407 First metric value calculation unit 409 First threshold comparison unit 411 First control unit 413 First calculation unit 415 CFO compensation unit 417 SSS detection unit 419 second synthesis unit 421 second metric value calculation unit 423 second threshold comparison unit 425 second control unit 427 second calculation unit

Claims (10)

A PSS detection step for performing PSS detection by performing a cross-correlation calculation between a received signal and a locally generated PSS (Primary Synchronous Sequence) signal,
A first synthesis step of synthesizing the correlation values calculated in the PSS detection step according to a first synthesis number m (m is an integer whose initial value is 0);
A first metric value calculating step for calculating a first metric value for evaluating the capability of PSS detection from the first combined correlation value calculated in the first combining step;
A first threshold comparing step for comparing the first metric value calculated in the first metric value calculating step with a first threshold;
If the first metric value is less than or equal to the first threshold, the first synthesis count m is increased until the first metric value is greater than the first threshold, and the PSS A first control step that repeatedly executes a detection step, the first synthesis step, the first metric value calculation step, and the first threshold value comparison step;
A first value for calculating an estimated value of a PSS ID (identifier: IDentifier), timing, and CFO (Carrier Frequency Offset) from the first combined correlation value calculated in the first combining step. A calculation step;
CFO compensation step for performing CFO compensation according to the estimated value of CFO calculated in the first calculation step;
In the frequency domain, a balanced SSS (Secondary Synchronous Sequence) signal received and a locally generated SSS signal are subjected to cross-correlation calculation to perform SSS detection step,
A second synthesis step of synthesizing the correlation values calculated in the SSS detection step according to a second synthesis number n (n is an integer whose initial value is 0);
A second metric value calculating step for calculating the second metric value for evaluating the capability of SSS detection from the second combined correlation value calculated in the second combining step;
A second threshold comparing step for comparing the second metric value calculated in the second metric value calculating step with a second threshold;
When the second metric value is less than or equal to the second threshold, the second synthesis number n is increased until the second metric value is greater than the second threshold, and the SSS detection A second control step that repeatedly executes a step, the second synthesis step, the second metric value calculation step, and the second threshold value comparison step;
The group ID is calculated from the second combined correlation value calculated in the second combining step, and the cell ID is calculated from the calculated group ID and the PSS ID calculated in the first calculating step. An initial cell search method comprising: a second calculation step.   In the first control step, after increasing the first synthesis number m, the first synthesis number m is compared with a first maximum synthesis number M (M is an integer greater than 0), and the first 2. The initial cell search method according to claim 1, wherein when the combination number m exceeds the first maximum combination number M, it is determined that the initial cell search process has failed, and the initial cell search process is exited.   In the second control step, after increasing the second combination number n, the second combination number n is compared with a second maximum combination number N (N is an integer greater than 0), and the second combination number n is compared. 2. The initial cell search method according to claim 1, wherein when the number of synthesis n exceeds the second maximum number of synthesis N, CFO compensation is reset and the initial cell search process is started again. In the first metric value calculating step, the first metric value is calculated according to the following equation:

Here, id is a PSS ID index number, C _av (id, k, m) is the first composite correlation value, and K _max (id) = argmax (C _av (id, k, m)) 2. The initial cell search method according to claim 1, wherein W _samples is the number of sample points in the search window for PSS detection, and W _PSS is the number of sample points in the first metric value calculation window. In the second metric value calculating step, the second metric value is calculated according to the following equation:

Here, GroupId is a group ID index, CpType indicates the type of cycle prefix, FrameTim indicates whether the current half frame is the first half frame or the second half frame in one frame data, and S _av (GroupId, CpType, FrameTime , n) is the second composite correlation value;

2. The initial cell search method according to claim 1, wherein A primary synchronization sequence PSS detection unit that performs PSS detection by performing cross-correlation calculation between the received signal and the locally generated PSS signal,
A first synthesis unit that synthesizes a correlation value calculated by the PSS detection unit according to a first synthesis number m (m is an integer whose initial value is 0);
A first metric value calculating unit for calculating a first metric value for evaluating the capability of PSS detection from the first combined correlation value calculated by the first combining unit;
A first threshold comparison unit that compares the first metric value calculated by the first metric value calculation unit with a first threshold;
If the first metric value is less than or equal to the first threshold, the first synthesis count m is increased until the first metric value is greater than the first threshold, and the PSS A detection unit; the first synthesis unit; the first metric calculation unit; a first control unit that repeatedly executes the processing in the first threshold comparison unit;
From the first combined correlation value calculated by the first combining unit, a first calculation unit for calculating a PSS ID, a timing, and an estimated value of a carrier frequency offset CFO;
A CFO compensation unit that performs CFO compensation according to the estimated value of the CFO calculated by the first calculation unit, and a cross-correlation calculation between the received balanced SSS signal and the locally generated SSS signal in the frequency domain Secondary synchronization sequence SSS detection unit that performs SSS detection,
A second synthesis unit that synthesizes the correlation value calculated by the SSS detection unit according to a second synthesis number n (n is an integer whose initial value is 0);
A second metric value calculating unit for calculating a second metric value for evaluating the capability of SSS detection from the second combined correlation value calculated by the second combining unit;
A second threshold comparison unit that compares the second metric value calculated by the second metric value calculation unit with a second threshold;
If the second metric value is less than or equal to the second threshold, the second synthesis number n is increased until the second metric value is greater than the second threshold, and the SSS A detection unit; the second synthesis unit; the second metric value calculation unit; a second control unit that repeatedly executes the processing in the second threshold comparison unit;
The group ID is calculated from the second combined correlation value calculated by the second combining unit, and the cell ID is calculated from the calculated group ID and the PSS ID calculated by the first calculating unit. An initial cell search device comprising: a second calculation unit that:   The first control unit, after increasing the first synthesis number m, compares the first synthesis number m with a first maximum synthesis number M (M is an integer greater than 0), and 7. The initial cell search device according to claim 6, wherein if the combination number m exceeds the first maximum combination number M, it is determined that the initial cell search process has failed, and the initial cell search process is exited.   The second control unit, after increasing the second combination number n, compares the second combination number n with a second maximum combination number N (N is an integer greater than 0), and compares the second combination number n. 7. The initial cell search device according to claim 6, wherein when the combination number n exceeds a second maximum combination number N, the CFO compensation is reset and the initial cell search process is started again. The first metric value calculation unit calculates the first metric value according to the following equation:

Here, id is a PSS ID index number, C _av (id, k, m) is the first composite correlation value, and K _max (id) = argmax (C _av (id, k, m)) 7. The initial cell search device according to claim 6, wherein W _samples is the number of sample points in the search window for PSS detection, and W _PSS is the number of sample points in the first metric value calculation window. The second metric value calculation unit calculates the second metric value according to the following equation:

Here, GroudId is a group ID index, CpType indicates the type of cycle prefix, FrameTim indicates whether the current half frame is the first half frame or the second half frame in one frame data, and S _av (GroupId, CpType, FrameTime , n) is the second composite correlation value;

9. The initial cell search device according to claim 8, wherein

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