• 专利附录
  • 专利说明
  • 权利要求
  • 类似技术
  • 同族专利
  • 引用文献
  • 法律状态
  • 优先权
    • 专利摘要:
    An OFDM receiving system and method for changing an FFT window application interval using a guard interval are disclosed. In the OFDM reception method for converting a data transmission interval in symbol units consisting of an effective symbol interval and a guard interval in a fast free manner, a process of extracting and extracting a distributed pilot inserted for each predetermined sample of a symbol from the received OFDM signal Estimating the symbol timing offset using the distributed pilot, and setting a symbol timing synchronization point in the data transmission interval, and extracting a predetermined length interval among the effective symbol interval from the set symbol timing synchronization point. Adding the samples to the FFT transform. According to the present invention, the symbol timing synchronization and channel equalization process can be performed accurately without inter-symbol interference even if the exact symbol start point is not determined in a multi-channel (or Rayleigh channel) or pre-ghost channel environment.
    公开号:KR20030006016A
    申请号:KR1020010041556
    申请日:2001-07-11
    公开日:2003-01-23
    发明作者:김정진；한동석
    申请人:삼성전자 주식회사；
    IPC主号:
    专利说明:

    OPDM receiving system for synchronizing symbol timing using guard interval and method
    [8] The present invention relates to an Orthogonal Frequency Division Multiplexer (OFDM) reception system, and more particularly, to an OFDM reception system and method for changing an FFT window application interval using a guard interval.
    [9] In general, an OFDM transmission system uses fast fourier transform (FFT) to transmit information on subcarriers and inserts a guard interval in front of an effective symbol interval in order to reduce the influence of multipath. The OFDM system performs an FFT window timing synchronization in which only a valid symbol is input to the FFT by finding a boundary between a guard period and a valid symbol interval in the received OFDM signal. To this end, the OFDM reception system should first find the interval of the FFT using the similarity between the guard interval and the effective symbol interval.
    [10] 1 is a conceptual diagram of performing symbol timing synchronization in a conventional OFDM receiving system.
    [11] Referring to (a) of FIG. 1, one symbol includes a guard period T g and a valid symbol period T u . A window timing controller (not shown) for controlling window timing determines a start point of a symbol using a guard interval, and inputs N samples from the determined start point of the symbol to the FFT operator (not shown).
    [12] At this time, the window timing controller (not shown) causes the input samples by the data transmission interval (T u), from the symbol timing synchronization point (symbol timing synchronization point) of the FFT window period to the FFT processor.
    [13] However, when the FFT window section is set as shown in FIG. 1A, the start point of an invalid symbol is determined in a pre-ghost channel environment in which multiple paths exist. A part of the next symbol (Intersymbol Interference: ISI) overlaps. Therefore, such symbol interference has a problem of degrading the performance of the OFDM receiving system.
    [14] The technical problem to be achieved by the present invention is to provide an OFDM reception method for preventing the inter-symbol interference occurring in the T multi-channel or pre-ghost channel by changing the application period of the FFT window using the guard interval transmitted in front of the effective symbol There is.
    [15] Another object of the present invention is to provide an OFDM system to which the OFDM reception method is applied.
    [16] In order to solve the above technical problem, the present invention provides a OFDM reception method for converting the data transmission interval in the symbol unit consisting of the effective symbol interval and the guard interval in high-speed free,
    [17] Extracting a distributed pilot inserted into a predetermined sample of one symbol from the received OFDM signal;
    [18] Estimating a symbol timing offset through the extracted distributed pilot to set a symbol timing synchronization point in the data transmission interval;
    [19] Characterized in that the OFDM reception method comprising the step of adding the samples of the predetermined period of the transmission interval to the samples obtained by subtracting a certain length of the effective symbol interval from the symbol timing synchronization point set in the above process.
    [20] In order to solve the above technical problem, the present invention is a OFDM reception system for converting the data transmission interval of the symbol unit consisting of the effective symbol interval and the guard interval in high-speed free,
    [21] Analog-digital conversion means for converting an OFDM signal into a digital complex sample;
    [22] FFT calculating means for converting the valid symbol interval to a fast free;
    [23] Distributed pilot extracting means for detecting a distributed pilot inserted into a sample output from said FFT calculating means;
    [24] Symbol timing offset estimating means for estimating the symbol timing offset through the distributed pilot extracted by the distributed pilot extracting means;
    [25] A symbol timing synchronization point is set in a data transmission interval input from the analog-digital converting means, and a predetermined interval in front of the data transmission interval is included in samples obtained by subtracting a predetermined length interval of the effective symbol interval from the set symbol timing synchronization point. And an FFT window control means for adding samples of the input to the FFT calculation means.
    [1] 1 is a conceptual diagram of performing symbol timing synchronization in a conventional OFDM receiving system.
    [2] 2 is an overall block diagram of an OFDM receiver system for performing symbol timing synchronization according to the present invention.
    [3] 3A and 3B are conceptual views illustrating a method for setting an FFT window section in an FFT window controller according to the present invention.
    [4] 4 is a conceptual diagram illustrating a method of resetting an FFT window section and inputting the FFT window to the FFT calculator in accordance with the present invention.
    [5] 5 is a flowchart illustrating a symbol timing synchronization method of an OFDM reception system according to the present invention.
    [6] 6 is a graph comparing symbol timing synchronization convergence performance of the present invention and the prior art.
    [7] 7 is a graph comparing the present invention and the prior art SER after symbol timing synchronization and channel equalization.
    [26] Hereinafter, exemplary embodiments of the present invention will be described with reference to the accompanying drawings.
    [27] 2 is an overall block diagram of an OFDM receiver system for performing symbol timing synchronization according to the present invention.
    [28] In the OFDM receiving system of FIG. 2, the ADC unit 210, the approximate symbol synchronization extractor 220, the FFT window controller 230, the FFT operator 240, the distributed pilot mode detector 250, and the distributed pilot extractor 260 are shown. And a symbol timing offset estimator 270 and a DPLL unit 280.
    [29] Referring to FIG. 2, first, an analog-to-digital converter (ADC) 210 converts an input analog OFDM signal into a digital complex sample having a sample rate of 9.14 MHz.
    [30] The coarse symbol sync extractor 220 extracts an approximate symbol start point from the input digital complex samples.
    [31] The FFT window controller 230 finds an approximate symbol start point by the coarse symbol sync signal extracted by the coarse symbol sync extractor 220, and then estimates the symbol timing offset estimator 270. Set the symbol timing synchronization point of the digital complex samples by using the offset value, and add the samples of the predetermined interval to the front of the data transmission interval to the samples obtained by subtracting the predetermined length interval of the effective symbol interval from the set symbol timing synchronization point. Input to the calculator 240.
    [32] The FFT calculator 240 converts the samples corresponding to the valid symbol interval input from the FFT window controller 230 to the fast free.
    [33] In this case, the FFT operator 240 outputs a signal in a frequency domain composed of the same number of subcarriers as the transmission mode. Signals in this frequency domain contain pilot data including general data and information necessary for various synchronization and OFDM transmissions. The distributed pilot signal inserted every 12 samples in one symbol of the frequency domain is required for symbol timing synchronization.
    [34] The distributed pilot mode detector 250 determines a mode of a distributed pilot, and compares the sum of powers of subcarriers corresponding to each distributed pilot mode by using a pilot having a greater power than general data, and thus, has high power among four modes. Detect the mode.
    [35] The distributed pilot extractor 260 extracts a distributed pilot inserted into a symbol using the distributed pilot start mode detected by the distributed pilot mode detector 250.
    [36] The symbol timing offset estimator 270 estimates an offset having an integer part and a fractional part using the distributed pilot extracted by the distributed pilot extractor 260. Therefore, the integer portion is applied to the FFT window control unit 230 to perform fine symbol timing synchronization, and the fractional portion controls the sampling clock of the ADC unit 210 through the DPLL 280.
    [37] The DPLL unit 280 changes the frequency and phase of the sampling clock of the analog-to-digital converter 210 by using a decimal value of the symbol timing offset output from the symbol timing offset estimator 260.
    [38] 3A and 3B are conceptual views illustrating a method for setting an FFT window section in the FFT window controller 230 according to the present invention.
    [39] Referring to FIG. 3A, the FFT window control unit 230 uses the offset value estimated by the symbol timing offset estimator 270 to form data including a guard period T g and an effective symbol period T u . Set the symbol timing synchronization point in the transmission section. Then, FFT window controller 230 adds samples of a valid symbol interval (T u), a predetermined period (T p) eda samples minus the predetermined length of the period to the front of the transmission interval is set from the symbol timing synchronization point. Here, the length of the predetermined period T p is smaller than the guard interval T g and is set according to the channel environment.
    [40] Referring to (b) of FIG. 3, the samples in the predetermined interval T p are the same as the symbol to be FFT transformed since they correspond to a guard interval in which a part of the effective symbol interval is copied from the transmitter. Accordingly, if only the same symbol is FFT transformed, the OFDM receiving system can prevent intersymbol interference.
    [41] 4 is a conceptual diagram illustrating a method of resetting the FFT window section by the FFT window controller 230 and inputting the FFT window 240 to the FFT calculator 240 according to the present invention.
    [42] The FFT window control unit 230 adds samples of a predetermined period T p to the front of the transmission period to the samples obtained by subtracting a predetermined length period of the effective symbol period T u from the symbol timing synchronization point set in the data transmission period. Input to the calculator 240. For example, when the data transmission mode is 2K, the FFT window controller 230 inputs 2048 samples to the FFT calculator 240 in parallel.
    [43] 5 is a flowchart illustrating a symbol timing synchronization method of an OFDM reception system according to the present invention.
    [44] First, an OFDM signal of a symbol unit is received from the transmission system (step 510).
    [45] Subsequently, a dispersion pilot inserted for each predetermined sample of one symbol is extracted from the received OFDM signal (step 520).
    [46] Subsequently, the symbol timing offset is estimated through the extracted distributed pilot (step 530), and a symbol timing synchronization point is set in the data transmission period including the guard period and the effective symbol period (step 540).
    [47] Subsequently, the FFT input position is reset by adding samples of a predetermined section to the front of the transmission section to the samples obtained by subtracting the predetermined length section of the valid symbol section from the set symbol timing synchronization point (step 550).
    [48] 6 is a graph comparing symbol timing synchronization convergence performance of the present invention and the prior art. The graph of FIG. 6 is the average squared residual value of the symbol timing offset (SAMPLE 2 ) after synchronizing the symbol timing obtained by applying the DVB-T system. Experimental environment is applied to data transmission mode 2K, guard interval length mode 1/16, initial sample offset 1000 samples, sampling clock frequency offset 200ppm, initial sampling clock phase offset, loop bandwidth of 500ppm PLL block. The multipath used 20 channels of the DVB-T test specification. In the Rayleigh channel and the Rician channel, the present invention has a lower mean symbol timing offset (SAMPLE 2 ) than the prior art.
    [49] 7 is a graph comparing the present invention and the prior art SER after symbol timing synchronization and channel equalization.
    [50] The experimental environment is the same as that of FIG. 6, and the channel equalization algorithm performs channel estimation and equalization through time and frequency axis linear interpolation using a distributed pilot for 4 symbols. Referring to the graph of FIG. 7, the present invention shows a lower SER in Rayleigh channel than in the prior art.
    [51] The present invention is not limited to the above-described embodiment, and of course, modifications may be made by those skilled in the art within the spirit of the present invention. That is, the present invention can be applied to symbol timing synchronization of European digital TVs, IEEE 802.11a wireless LANs, or other systems using the OFDM scheme.
    [52] The above-described embodiments of the present invention can be written as a program that can be executed on a computer. And it can be implemented in a general-purpose digital computer for operating the program from a medium used in the computer. Such media include storage media such as magnetic storage media (e.g. ROM, floppy disks, hard disks, etc.), optical reading media (e.g. CD-ROMs, DVDs, etc.) and carrier waves (e.g., transmitting over the Internet). . In addition, the computer-readable recording medium may be distributed and stored in other systems through a networked computer system, and may be executed.
    [53] As described above, the present invention can accurately perform symbol timing synchronization and channel equalization without inter-symbol interference even if the exact symbol start point is not determined in a multi-channel (or Rayleigh channel) or pre-ghost channel environment.
    权利要求:
    Claims (5)
    [1" claim-type="Currently amended] In the OFDM reception method for converting the data transmission interval of the symbol unit consisting of the effective symbol interval and the guard interval in a fast free,
    Extracting a distributed pilot inserted into a predetermined sample of one symbol from the received OFDM signal;
    Estimating a symbol timing offset through the extracted distributed pilot to set a symbol timing synchronization point in the data transmission interval;
    And performing FFT conversion by adding samples of a predetermined period of the transmission period to samples obtained by subtracting a predetermined length period of the valid symbol period from the symbol timing synchronization point set in the process.
    [2" claim-type="Currently amended] The OFDM reception method of claim 1, wherein a predetermined period of the transmission period is a part of the symbol timing synchronization point.
    [3" claim-type="Currently amended] The OFDM reception method of claim 1, wherein a predetermined period of the transmission period is a period less than the guard period length.
    [4" claim-type="Currently amended] The method of claim 1, wherein a predetermined period of the transmission period is set differently according to a channel environment.
    [5" claim-type="Currently amended] In the OFDM reception system for converting the data transmission interval of the symbol unit consisting of the effective symbol interval and the guard interval in high-speed free,
    Analog-digital conversion means for converting an OFDM signal into a digital complex sample;
    FFT calculating means for converting the valid symbol interval to a fast free;
    Distributed pilot extracting means for detecting a distributed pilot inserted into a sample output from said FFT calculating means;
    Symbol timing offset estimating means for estimating the symbol timing offset through the distributed pilot extracted by the distributed pilot extracting means;
    A symbol timing synchronization point is set in a data transmission interval input from the analog-digital converting means, and a predetermined interval in front of the data transmission interval is included in samples obtained by subtracting a predetermined length interval of the effective symbol interval from the set symbol timing synchronization point. And an FFT window control means for adding samples of the input to the FFT calculation means.
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    引用文献:
    公开号 | 申请日 | 公开日 | 申请人 | 专利标题
    法律状态:
    2001-07-11|Application filed by 삼성전자 주식회사
    2001-07-11|Priority to KR1020010041556A
    2003-01-23|Publication of KR20030006016A
    2008-05-28|Application granted
    2008-05-28|Publication of KR100833223B1
    优先权:
    申请号 | 申请日 | 专利标题
    KR1020010041556A|KR100833223B1|2001-07-11|2001-07-11|OFDM receving system for synchronizing symbol timing using guard interval and method thereof|
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