KR20090105688A - Apparatus and method for recognizing location based on orthogonal frequency division multiplexing(ofdm) - Google Patents

Abstract

PURPOSE: An OFDM signal-based position recognizing apparatus and a method thereof are provided to calculate the position by detecting a leading-edge point. CONSTITUTION: An OFDM signal-based position recognizing apparatus comprises an OFDM signal receiving unit(100), a TPS detection unit(200), and a TDoA calculation unit. The OFDM signal receiving unit obtains symbol synchronization through a received OFDM signal, and detects a leading-edge point. The TPS detection unit detects TPS and transmission station location information from the OFDM signal received by the OFDM signal receiving unit. The TDoA calculation unit calculates a position through the TDoA method between transmission stations by using the leading-edge point and TPS.

Description

Apparatus and method for recognizing location based on orthogonal frequency division multiplexing (OFDM) based on Orthogonal Frequency Division Multiplexing (OPEDM) signal

The present invention relates to a position recognition system, and more particularly, to a position recognition system using an OFDM signal used as a broadcast wave signal.

In the related art, a satellite positioning system (GPS) or a narrow band channel is used as a method for locating a position.

A position recognition system using a narrowband channel, for example, a position recognition system using a broadcast wave signal, generally has a time of arrival (ToA) or a time difference of arrival (TDoA) of a measurement signal for position recognition. ) To estimate the position.

A method using the arrival time (ToA) is a method of estimating a distance by transmitting a measurement signal from an object to which its location is to be determined to a base station, receiving the received signal from the base station, and measuring a transmission time of the measurement signal between the object and the base station. That is, from the plurality of measurement values measured by the plurality of base stations, circles around each base station are generated, and the object is placed at the intersection of these circles, so that the position thereof can be determined.

On the other hand, the method using the arrival time difference (TDoA) determines the position using the arrival time difference of the measurement signal transmitted from different places. That is, the signal arrival time difference is measured in proportion to the difference in distance from the two base stations to the target, and the position can be determined because the target is positioned on a hyperbolic line where the two base stations have a constant distance difference, that is, the two base stations are in focus.

Since this method estimates the distance and position of the object based on timing information related to the arrival time of the received measurement signal, in order to position the object, first, the arrival time of the measurement signal must be accurately determined. do. In the case where there is no obstacle in the straight path between the transmitter transmitting the measurement signal and the receiver receiving the signal, it is relatively easy to accurately find timing information related to the arrival time of the measurement signal. Signal is available.

However, the detection of the linear path signal is very difficult in the environment where there are obstacles in the linear path between the transmitter and the receiver or in the complex multipath environment such as indoor environment. There is a problem that the accuracy is significantly reduced. This difficulty in detecting line path signals is due to the limited time resolution of the signals used for measurement. Time resolution refers to the degree to which a receiver receiving a measurement signal can distinguish multipath signals having different differential path lengths and is generally in inverse proportion to the bandwidth of the signal.

Therefore, the implementation of a location recognition system using broadcast waves has some limitations because many base stations are required for inaccuracy or accurate location recognition.

SUMMARY OF THE INVENTION An object of the present invention is to provide a location recognition device and a location recognition method capable of accurate location recognition while using an OFDM signal, for example, a broadcast wave signal.

In order to achieve the above object, the present invention provides a TPS detection unit for detecting TPS (Transmission Parameter Signal) and transmitting station location information; An OFDM signal receiving unit for acquiring symbol synchronization through a received orthogonal frequency division multiplex (OFDM) signal and detecting a leading-edge point; And a TDoA calculator configured to calculate a position through a TDoA (Time Difference of Arrival) method between transmission stations.

The OFDM signal receiving unit may include: a reading-edge detector detecting the leading-edge point by detecting a minimum symbol interference interval with respect to the OFDM signal; An FFT calculator configured to perform an FFT on the leading-edge obtained by the leading-edge detector; A phase corrector for generating a sine wave and multiplying the output of the FFT calculator to correct a phase of the output signal of the FFT calculator; And a decoding unit which performs decoding on the signal whose phase is corrected. The TPS detector may detect the TPS detection and the transmitter position information from a result of multiplying the output of the FFT calculator and the phase corrector.

The leading-edge detector comprises: a BER calculator configured to calculate a bit error rate (BER) of the output signal of the decoder; A symbol time shift estimator for receiving a maximum impulse response and the BER calculator output signal and estimating a shift in symbol timing; And a read-edge adjuster configured to receive the output of the symbol time shift estimator to adjust the leading-edge point, and the BER calculator may detect the leading-edge point through the bit error rate calculation.

The phase compensator includes a subcarrier index generator for generating an index for a subcarrier, and a sine wave generator (NCO) for generating the sinusoid, wherein the sinusoidal generator generates the symbol time shift. The sine wave may be generated based on a result value obtained by multiplying the output of the estimator and the output of the subcarrier index generator as an address value.

In order to accurately estimate the leading-edge point for the OFDM signal, a feedback operation between the component parts is performed, and when the leading-edge detector obtains an initial leading-edge point, the maximum impulse response point of the OFDM signal In FIG. 4, the point leading one quarter of the guard symbol is estimated as the leading-edge point, and then the BER calculation gradually detects the leading-edge point gradually.

The TPS detector may include a memory device for taking an average to increase the TPS detection rate. The memory device stores the real part (I) and imaginary part (Q) signals, respectively, and the number of times the pilot of the TPS is accumulated in the memory device is controlled by an average frequency adjuster, and the average frequency adjuster is controlled by RSSI information. And receiving bit error information from a BCH decoder to calculate the cumulative number of times.

On the other hand, the location recognition device may be used in conjunction with a cellular network-based location recognition device, a GPS-based location recognition device or a cellular network and GPS-based location recognition device.

The present invention also provides a receiver comprising at least two receivers having the position recognition device of claim 1 to achieve the above object; And a host connected to the receiver to control input and output of a signal to the receiver.

In the present invention, the OFDM signal receiving terminal may include a clock oscillator (Crystal) for synchronizing the clock synchronization of at least the two receivers.

Furthermore, the present invention provides a method for achieving the above object, comprising: detecting a leading-edge point for an OFDM signal of a first transmission station; Detecting a leading-edge point for the OFDM signal of the second transmitting station; Comparing whether the first four OFDM symbols and the second four OFDM symbols are the same as a fast symbol and a guard symbol; And performing a TDoA calculation for every symbol (effective symbol + guard symbol) if it is the same, and performing a TDoA calculation for every symbol having the same guard symbol start position if it is not the same. And detecting a leading-edge point of the OFDM signal of the second transmission station by using a bit error rate (BER) calculation.

In the present invention, the leading-edge detection of the first and second transmission stations comprises: detecting an effective symbol and a guard symbol for the FFT signal; Obtaining a maximum impulse response point of the OFDM signal by a maximum impulse response estimator; Performing an FFT at a point ahead of the maximum impulse response point; Searching for the minimum bit error section through the BER calculation; And estimating the leading-edge point in the minimum bit error period.

On the other hand, multiplying the signal for phase correction of the FFT output and the FFT output before the minimum bit error interval searching step; And performing decoding on the multiplied signal by a decoder.

When the FFT is performed for the first time, the predetermined point selects a point preceding 1/4 of a guard symbol from the maximum impulse response point. The FFT is continuously performed through a feedback operation. It may be performed by adjusting to the estimated leading-edge point.

On the other hand, performing the TDoA calculation in the case of not the same, the TDoA initialization is performed by finding a point that is the least common multiple of the length of the OFDM signal (effective symbol + guard symbol) and the TPS start point of the first and second transmission stations. In this case, the TDoA calculation may be performed based on the point of the least common multiple and the starting point of the TPS.

The TDoA calculation may be performed by extracting a TPS from the OFDM signal from which the leading-edge point is estimated, and accumulating the extracted TPS a predetermined number of times through a storage device to improve the TPS detection rate. The TPS is stored in the storage device as a real part (I) and an imaginary part (Q) signal, and the number of times the pilots of the TPS are accumulated is controlled by an average recovery controller, and the average recovery controller is a RSSI information and a BCH decoder. The cumulative number of times may be calculated by receiving bit error information.

In the OFDM signal-based position recognition apparatus and the position recognition method according to the present invention, by detecting the fastest response, that is, the leading-edge point of the signal, and performing the position calculation, the position error can be reduced to search for the correct position.

In addition, in detecting a TPS signal used as a time-stamp of GPS, the TPS detector used in the positioning device of the present invention uses a storage device as an average and uses the average number of times of the averaged RSSI and BCH-decoder. By adjusting according to the number of bit errors, the TPS information detection rate can be increased.

Hereinafter, with reference to the accompanying drawings will be described a preferred embodiment of the present invention; In the following description, when a component is described as being connected to another component, it may be directly connected to another component, but a third component may be interposed therebetween. In addition, in the drawings, the structure or size of each component is exaggerated for convenience and clarity of explanation, and parts irrelevant to the description are omitted. Like numbers refer to like elements in the figures. On the other hand, the terms used are used only for the purpose of illustrating the present invention and are not used to limit the scope of the invention described in the meaning or claims.

1A and 1B are conceptual views of a position recognition system using a conventional GPS and a corresponding position recognition system using an OFDM signal according to an embodiment of the present invention.

Referring to FIG. 1A, the conventional position recognition system A using GPS includes a time-stamp detector 40 for detecting time-stamp and satellite position information, and a signal acquirer 50 for acquiring and tracking satellite signals. ), A TDoA calculation unit 60 for calculating a position using four or more satellite-to-satellite TDoA methods based on the acquired signal, and a navigation for calculating a minimum path between the two points when two or more points are calculated. The calculation unit 70 is included.

The position recognition system B of the present invention can adopt the basic structure of the conventional position recognition system using such a GPS as it is. That is, the position recognition system (B) according to an embodiment of the present invention is a TPS detection unit 200 for TPS detection and transmission station position detection, OFDM for symbol synchronization acquisition and leading-edge detection of OFDM signals The signal receiver 100 includes a TDoA calculator 300 that calculates TDoA between four or more transmitters based on the obtained leading-edge information, and a navigation calculator 400. The position recognition system B of the present invention uses an OFDM signal, for example, an OFDM-based Digital Video Broadcasting-Terrestrail (DVB-T) signal instead of a satellite signal.

Here, the TPS means a transmission parameter signal and corresponds to a time-stamp, which is a time information signal included in the satellite signal. The TPS generally contains system information at the time of modulation of transmitted information, and this information is used at the receiving side for demodulation. Therefore, the TPS is inserted and transmitted to a predetermined position in the OFDM signal frame, and if such a TPS is correctly detected, the TDoA can be accurately calculated based on the TPS information. Meanwhile, the position recognition system of the present invention includes an OFDM signal receiver 100 for symbol acquisition and leading-edge detection for an OFDM signal corresponding to satellite signal acquisition and tracking, which will be described in more detail with reference to FIG. 2.

The position recognition apparatus using the OFDM signal according to the present embodiment accurately detects the leading-edge of the OFDM signal while using the narrowband signal, that is, the OFDM signal, so that the conventional position recognition system using the narrowband signal is capable of obtaining accurate measurement signals. Difficulties can solve the problem of not being able to accurately position.

FIG. 2 is a block diagram of an OFDM signal receiver for symbol synchronization acquisition and leading-edge detection in the system of FIG. 1B.

Referring to FIG. 2, the OFDM signal receiver 100 according to the present exemplary embodiment may include a leading-edge detector 120, an FFT calculator 140, a phase compensator 130, and a decoder 150. Include. The leading-edge detector 120 finds a point closest to the maximum impulse response point as the leading-edge, that is, the minimum symbol interference point for the OFDM signal. This leading-edge, after all, refers to the position of the earliest received electromagnetic wave when measuring the distance in the positioning device. Finding the correct leading-edge for the OFDM signal enables accurate TPS detection and hence the calculation of TDoA based on accurate time information.

The FFT calculator 140 performs an FFT on the leading-edge obtained by the leading-edge detector 120. Since the leading-edge portion is the start of the signal and the minimum symbol interference point, the FFT is performed at the leading-edge portion, thereby preventing the constellation from spreading after performing the FFT.

The phase corrector 130 generates a sine wave having phase information and multiplies the output of the FFT calculator 140 to correct the phase of the output signal of the FFT calculator 140. In the case of an OFDM signal, it generally includes a fast fourier transform symbol portion and a guard symbol portion. When the FFT starts at the effective symbol portion, the FFT is generated after the FFT due to inter-symbol-interference (ISI). The problem of constellation spreading occurs. In order to prevent this, the FFT is performed from the minimum symbol interference region in the guard symbol portion. When the FFT position is changed in this way, the phase of the FFT output signal is rotated accordingly. The phase correction unit 130 corrects the rotated phase to its original position.

The decoder 150 decodes the phase corrected signal. On the other hand, the TPS detector 200 detects the TPS with respect to the phase-corrected OFDM signal before decoding is performed.

 Meanwhile, the OFDM signal receiver basically includes a pre-FFT symbol timing calculator 110, a baseband converter 160, and an interpolation filter 170, and the pre-FFT symbol timing calculator 110 includes an FFT. The effective symbol and the guard symbol of the OFDM symbol are detected before execution, the baseband converter 160 converts the OFDM signal into a baseband signal, and the interpolation filter unit 170 outputs the output signal of the baseband converter 160. The sample is input to the FFT calculator 140.

If you describe each component in more detail,

The leading-edge detector 120 includes a symbol timing shift estimator 122, a leading-edge adjuster 124, and a bit error rate (BER) calculator 126. The BER calculator 126 calculates a bit error rate with respect to the signal output from the decoder 150, and the symbol timing shift estimator 122 estimates a maximum impulse response point therein (not shown). The maximum impulse response estimation unit and the BER calculation unit BER calculation values of the BER calculation unit 126 are input to obtain a time difference between the maximum impulse response point and the minimum symbol interference point based on the length of a given guard symbol interval. The leading-edge adjusting unit 124 receives the output of the symbol time shift estimating unit 122, detects the leading-edge point, and adjusts the FFT starting point of the FFT calculating unit 140. In other words, the detected leading-edge point is taken as the FFT starting point.

The phase correction unit 130 includes a subcarrier index generator 132 for generating a subcarrier index and a sine wave generator 134 for generating a sinusoidal wave (NCO). The subcarrier index generator 132 is a counter that sequentially outputs numbers from -3408 to 3408 in the 8192 FFT mode of the DVB-T.

The sinusoidal wave generator 134 generates a sinusoidal wave used to remove a frequency shift of a symbol. In general, the sinusoidal wave generator 134 removes the frequency shift by multiplying the sinusoid by the time axis before performing the FFT. In the present embodiment, the sinusoidal wave generator 134 uses the result of multiplying the symbol timing shift of the symbol timing of the estimator 122 by the index value of the subcarrier index generator 132 as an address value. Generate a sine wave and remove the phase rotation of the FFT output by multiplying the complex conjugate of the sine wave by the FFT output value.

That is, the sinusoidal wave generator 134 generates a sinusoidal wave corresponding to the phase rotation through the symbol timing shift and the index product, and automatically removes the phase rotation of the FFT output by multiplying the complex conjugate of the sinusoid by the FFT output. .

The decoder 150 may include a channel equalizer 152 that compensates for the distortion of a distorted channel, a Viterbi decoder 154 that performs decoding using a convolution code, and a Reed Solomon code. Reed-Solomon code) includes a Reed Solomon decoder 156 that performs decoding. The BER calculation unit 126 performs BER calculation on the decoded signal through the Reed Solomon decoder 156.

 As shown in the figure, the BER calculation value of the BER calculation unit 126 is input to the symbol timing shift estimator 122 to calculate the symbol timing shift, and detects the leading-edge through the symbol timing shift. Perform FFT at. This continuous feedback process enables more precise detection of leading-edge points, thereby solving the problem of spreading constellations of the FFT output, and also by detecting the TPS from the FPS output by the TPS detector 200. More accurate TPS detection is possible. Accordingly, the TDoA calculation for location recognition can be performed accurately.

3 is an OFDM signal graph showing the leading-edge portion of an OFDM signal.

Referring to FIG. 3, in general, a minimum symbol interference point of an OFDM signal symbol is present in a guard symbol period, and a point where a signal is started first among the minimum symbol interference points, that is, a leading-edge point is the maximum of the minimum symbol interference period. It is located closest to the impulse response point. Therefore, first, search for the maximum impulse response point, and then find the minimum symbol interference section through the BER calculation, and then select the closest edge from the maximum impulse response point among the minimum symbol interference intervals as the leading-edge point. These leading-edge points can be precisely found through a feedback process.

In general, the leading-edge point is known to appear about 1/4 of the length of the guard symbol section at the maximum impulse response point. However, the leading-edge point does not always exist at that location. Accordingly, the present invention can improve the TPS detection rate by actively searching through the feedback for the correct leading-edge point, not the fixed position, and also performing FFT at the retrieved leading-edge point.

4 is a SER graph for an output signal showing that the leading-edge point is the same regardless of the Doppler frequency.

FIG. 4 shows a symbol error rate (SER) according to a position of performing FFT among guard symbols of 2048 samples in a TU6 channel environment, where X axis represents an index of a sample and Y axis represents an SER. Meanwhile, TU6 is one of the DVB-T communication channel environments, and Hz @ TU6 is the Doppler frequency according to the moving speed of the receiver in the TU6 channel environment.

As can be seen from Figure 4, it can be seen that the SER is lower as the FFT is performed in the center portion of the guard symbol, and also the SER is significantly lower as the Doppler frequency is lower. However, regardless of the Doppler frequency, the leading-edge point (circle of dashed line) is the same. Therefore, by accurately detecting the leading-edge point through the positioning device of the present embodiment and performing the FFT at the leading-edge, the SER can be lowered regardless of the Doppler frequency and the TPS detection rate can be increased.

FIG. 5 is a timing diagram illustrating a point in time when a symbol of an OFDM signal received from each transmitting station has a different size, and the time point of the symbol varies with time.

As shown in FIG. 5, the symbol size of the OFDM signal transmitted from each transmission station may be different. In this case, when the size of the symbol is different, the calculation of the TDoA through the leading-edge becomes incorrect. Therefore, performing TDoA calculation performs TDoA initialization by finding a point (denoted by a dotted line) and a starting point of TPS that are the least common multiple of the length of the OFDM signal (effective symbol + guard symbol) of the first and second transmission stations. The TDoA calculation may be performed based on the point of least common multiple and the starting point of the TPS.

FIG. 6 is a block diagram illustrating a TPS detection unit for TPS detection and retrieval of location information in the system of FIG. 1B.

6, the TPS detector 200 of this embodiment is similar to the TPS detector used in the terminal for receiving an OFDM signal. That is, the TPS detector 200 includes a comparator 240, a 16-bit Sync-word matching filter 280, a memory 29, a Bose-Chadhuri-Hocquenghem (BCH) decoder 250, and the like. However, the TPS detector of the present embodiment includes a TPS pilot averaging device 220 to increase the TPS detection rate. The averaging device 220 is a TPS pilot accumulator 224, 224a for dividing a complex signal subjected to FFT and accumulating the I and Q signals respectively, two memory devices 222 and 222a for accumulating, and a memory device. It includes an average number of times adjuster 225 to adjust the cumulative number of times. Meanwhile, the average frequency adjuster calculates an appropriate cumulative number of times through the output from the Received Signal Strength Indication (RSSI) calculator 260 and the output information of the BCH decoder 250.

In general, signals such as TPS include noise. When a certain period is added periodically, the noise becomes zero. Thus, the SER of the signal can be lowered. That is, the TPS detection rate can be improved due to noise reduction.

FIG. 7 is a simulation picture showing that the SER can be minimized by accumulating and averaging TPS signals through a memory device in the TPS detector of FIG. 6.

 As shown in FIG. 7, it can be confirmed that a point (marked by a black vertical line) at which the SER becomes O is generated through the accumulation of the TPS. Thus, by setting SER to O through accumulation, the TPS detection rate can be increased. The graph in the middle shows the result of adding only 68 bits in one frame. The graph below shows the signal waveform detected by the Sync-Word detector, and the tip that protrudes up and down is the BER starting point for each symbol. As shown in the drawing, it can be seen that the BER starting point becomes more prominent as it accumulates.

FIG. 8 is a block diagram of an entire OFDM signal receiving terminal having the position recognition system of FIG. 1B.

Referring to FIG. 8, the terminal for receiving an OFDM signal includes two receivers 1000 and 1000a including a position recognition device, a clock oscillator 1200 to synchronize clocks of the two receivers, and each receiver 1000, It is connected to the 1000a) includes a host (host, 2000) for controlling the input and output of each receiver signal. The OFDM signal terminal configured as described above includes a positioning device therein, so that its position can be accurately identified through communication with the base station using an OFDM signal, for example, a DVB-T signal.

The terminal for receiving an OFDM signal may be a DVB-T receiver for receiving a DVB-T broadcast signal.

9 is an exemplary view showing a method of finding a location through the TDoA method using the location recognition system of the present invention.

Referring to FIG. 9, an OFDM signal receiving terminal including each transmitting station A, B, and C and a corresponding object, for example, a positioning device, exchanges an OFDM signal including a TPS through communication to calculate an accurate TDoA between each transmitting station. Can be. Accordingly, the corresponding object is located on a hyperbola focusing on two transmitting stations according to the TDoA. At least two hyperbolic lines are extracted through communication between at least three transmitting stations, and the object is identified as an overlapping point (black point). Can be. Although three transmission stations and three hyperbolas corresponding thereto are shown in the figure, more transmission stations and hyperbolas may be introduced. The larger the number of transmitters, the more accurate location tracking is possible.

FIG. 10 is a block diagram showing that a location recognition device B using an OFDM signal according to another embodiment of the present invention can be used in conjunction with an existing cellular network or GPS-based location recognition devices C and A. .

In general, the location recognition method using the cellular network is a method of identifying the location of the mobile device from the location information of the base station in charge of the area in which the mobile phone is mounted. However, the position recognition method using the cellular network has a limitation in determining the precise position due to the position error of about 500 m.

On the other hand, GPS-based position recognition method as described above, by using the four GPS satellites orbiting the earth to calculate the relative distance between the moving object and the satellite to determine the position to some extent, but indoors It is difficult to identify the location in the shaded area.

The disadvantages of the cellular network and GPS-based location recognition method can be compensated by the location recognition method using the OFDM signal of the present invention. That is, by embedding the position recognition device using the OFDM signal of the present invention in a cellular phone or a GPS receiver and interworking with each other, it is possible to perform accurate position recognition in the cellular phone and position recognition in the sound region in the GPS receiver.

In the drawing, although described as a DVB signal, all broadcast wave signals using the OFDM scheme may be used. In addition, although a cellular network is illustrated, a PCS network using a base station may also be used.

11A is a flowchart illustrating a location recognition method using an OFDM signal according to another embodiment of the present invention.

Referring to FIG. 11A, the position recognition method of the present embodiment first detects leading-edge points for OFDM signals received from first and second transmission stations (S100 and S200). The detection of the leading-edge point of the OFDM signal of the first and second transmitting stations is performed using the BER calculation as mentioned above, and through the continuous feedback process, the correct leading-edge is obtained. Next, it is compared whether an effective signal and a guard symbol of the OFDM signal of the first transmission station and the OFDM signal of the second transmission station are the same (S300). As described in the part of FIG. 5, when the size of the symbol is different, the starting point of the signal is changed, and thus, an accurate TDoA calculation cannot be performed. Therefore, in the same case, TDoA is performed for every symbol (S400), and in other cases, TDoA calculation is performed for every symbol having the same guard symbol start position. That is, performing TDoA calculation performs TDoA initialization by finding a point that is the least common multiple of the length of the OFDM signal (effective symbol + guard symbol) and a TPS start point of the first and second transmission stations (S420), and performing the minimum common multiple. The TDoA calculation is performed on the basis of the point and the starting point of the TPS (S440).

FIG. 11B is a flow chart illustrating in more detail a method of detecting leading-edge points for OFDM signals received from each transmitter of FIG. 11A.

Referring to FIG. 11B, first, a valid symbol and a guard symbol are detected through a pre-FFT symbol timing calculator with respect to the received OFDM signal (S110). Next, the maximum impulse response point of the OFDM signal is determined by the maximum impulse response estimator. Obtain (S120). Thereafter, the FFT is performed at a predetermined point before the maximum impulse response point (S130). Here, the predetermined point is a randomly estimated leading-edge point. When the first FFT is performed, as described above, a portion of about 1/4 of the guard symbol section length at the maximum impulse response point is estimated as the leading-edge. Next, phase correction is performed on the FFT output and decoding is performed on the output signal (S140). The minimum bit error section is searched for through the BER calculation on the decoded signal (S150). When the minimum bit error section is found, the point nearest to the maximum impulse response point among the sections is estimated as the leading-edge (S160). When the leading-edge point is estimated as described above, the FFT is performed again at the leading-edge point (130a). The feedback process is then continued to detect more accurate leading-edge points. Here, as described above, the phase correction may be performed by conjugate multiplying a signal for phase correction of the FFT output and the FFT output, that is, a sine wave having phase information.

 The position recognition apparatus and method according to the present embodiment uses an OFDM signal such as a DVB-T broadcast signal to perform the position calculation by detecting the fastest response, that is, the leading-edge point, thereby reducing the distance error and searching for the correct position. Do it. On the other hand, in detecting a TPS signal corresponding to a GPS Time-Stamp, the TPS detector used in the present invention uses a storage device as an averaging device and uses the average number of times of the averaging device as the number of bit errors of the RSSI and the BCH-decoder. By adjusting accordingly, the detection rate of the TPS information can be increased.

So far, the present invention has been described with reference to the embodiments shown in the drawings, which are merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible therefrom. will be. Therefore, the true technical protection scope of the present invention will be defined by the technical spirit of the appended claims.

1A and 1B are conceptual views of a position recognition system using a conventional GPS and a corresponding position recognition system using an OFDM signal according to an embodiment of the present invention.

FIG. 2 is a block diagram of an OFDM signal receiver for symbol synchronization acquisition and leading-edge detection in the system of FIG. 1B.

3 is an OFDM signal graph showing the leading-edge portion of an OFDM signal.

4 is a SER graph for an output signal showing that the leading-edge point is the same regardless of the Doppler frequency.

FIG. 5 is a timing diagram illustrating a point in time when a symbol of an OFDM signal received from each transmitting station has a different size, and the time point of the symbol varies with time.

FIG. 6 is a block diagram illustrating a TPS detection unit for TPS detection and retrieval of location information in the system of FIG. 1B.

FIG. 7 is a simulation picture showing that the SER can be minimized by accumulating and averaging TPS signals through a memory device in the TPS detector of FIG. 6.

FIG. 8 is a block diagram of an entire OFDM signal receiving terminal having the position recognition system of FIG. 1B.

Figure 9 is an exemplary view showing a location through the TDoA method using the location recognition system of the present invention.

FIG. 10 is a block diagram showing that a location recognition device using an OFDM signal according to another embodiment of the present invention can be used in conjunction with an existing cellular network or GPS-based location recognition device.

11A is a flowchart illustrating a location recognition method using an OFDM signal according to another embodiment of the present invention.

FIG. 11B is a flow chart illustrating in more detail a method of detecting leading-edge points for OFDM signals received from each transmitter of FIG. 11A.

Claims (25)

An OFDM signal receiving unit for acquiring symbol synchronization through a received orthogonal frequency division multiplex (OFDM) signal and detecting a leading-edge point; A TPS detector for detecting a transmission parameter signal (TPS) and transmitting station position information from the OFDM signal received by the OFDM signal receiver; And And a TDoA calculator configured to calculate a position using a time difference of arrival (TDoA) method between transmission stations using the reading-edge point and the TPS. According to claim 1, The OFDM signal receiving unit A leading-edge detector detecting the minimum-signal interference section for the OFDM signal to detect the leading-edge point; An FFT calculator configured to perform a fast fourier transform (FFT) on the leading edges obtained by the leading edge detector; A phase corrector for generating a sine wave and multiplying the output of the FFT calculator to correct a phase of the output signal of the FFT calculator; And a decoding unit for decoding the phase-corrected signal. The method of claim 2, And the TPS detection unit detects the TPS detection and transmission station location information from a result of multiplying the outputs of the FFT calculating unit and the phase correction unit. The method of claim 2, The leading-edge detector A BER calculator for calculating a bit error rate (BER) for the output signal of the decoder; A symbol timing shift estimator for estimating a shift in symbol timing based on a maximum impulse response and the BER calculator output signal; And a reading-edge adjusting unit configured to adjust the reading-edge point based on the output of the estimating unit. The method of claim 4, wherein The BER calculator detects the leading-edge point through the bit error rate calculation. The method of claim 2, The phase correction unit A subcarrier index generator for generating an index for a subcarrier (sub-carrier), and a sinusoidal generator (Numerically Controlled Oscillator: NCO) for generating the sine wave, The sinusoidal wave generator generates the sinusoidal wave based on a result value obtained by multiplying the output of the estimate timing unit and the output of the subcarrier index generator by using the symbol timing shifting unit. The method of claim 2, And a feedback operation between the component parts is performed to accurately estimate the leading-edge point for the OFDM signal. The method of claim 7, wherein When the leading-edge detector obtains the first leading-edge point, OFDM signal-based position recognition device characterized in that for estimating the point leading to the leading edge of the guard symbol at the maximum impulse response point of the OFDM signal. According to claim 1, The TPS detector And a storage device for taking an average to increase the TPS detection rate. The method of claim 9, The memory device stores the real part (I) and imaginary part (Q) signals, respectively, and the number of times the pilot of the TPS is accumulated in the memory device is controlled by an average frequency adjuster. The average frequency adjuster receives bit error information from RSSIReceived Signal Strength Indication (RSSI) information and a Bose-Chaudhuri-Hocquenghem (BCH) decoder to calculate the cumulative number of times. According to claim 1, The OFDM signal is a DVB signal, The location recognition device is an OFDM signal based location recognition device, characterized in that for using the digital broadcast OFDM signal. According to claim 1, The OFDM signal is a DVB signal, The location recognition device is an OFDM signal-based location recognition device, characterized in that can be used in conjunction with a cellular network-based location, GPS-based location recognition device or a cellular network and GPS-based location recognition device. A receiver unit comprising at least two receivers having the position recognition device of claim 1; And And a host connected to the receiver to control input and output of a signal to the receiver. The method of claim 13, And a clock oscillator (Crystal) for synchronizing clocks of at least the two receivers. The method of claim 13, The receiving terminal includes a cellular network-based location recognition device, a GPS-based location recognition device or a cellular network and GPS-based location recognition device, And the location recognizing device is used in conjunction with the cellular network or the GPS-based location recognizing device. Detecting a leading-edge point for the OFDM signal of the first transmitting station; Detecting a leading-edge point for the OFDM signal of the second transmitting station; Comparing a valid symbol and a guard symbol of the OFDM signal of the first transmitting station and the OFDM signal of the second transmitting station; And Performing the TDoA calculation for every symbol (effective symbol + guard symbol) if the same, and if not, performing the TDoA calculation for every symbol having the same guard symbol start position; And detecting a leading-edge point of the OFDM signals of the first and second transmission stations by using a bit error rate (BER) calculation. The method of claim 16, The leading-edge detection of the first and second transmission stations is Detecting a valid symbol and a guard symbol for the OFDM signal; Obtaining a maximum impulse response point of the OFDM signal by a maximum impulse response estimator; Performing an FFT at a point ahead of the maximum impulse response point; Searching for the minimum bit error section through the BER calculation; And And estimating the leading-edge point in the minimum bit error period. The method of claim 17, Before the minimum bit error interval search step, Conjugate multiplying the signal for phase correction of the FFT output and the FFT output; And Performing a decoding on the multiplied signal by a decoder; The signal for phase correction is an OFDM signal based position recognition method, characterized in that the sinusoidal signal generator generates a product of the subcarrier index and the symbol timing shift as an address value. The method of claim 17, And when the FFT is performed for the first time, the predetermined point is one point ahead of a guard symbol at the maximum impulse response point. The method of claim 17, The FFT is performed continuously through a feedback operation, wherein the predetermined point is adjusted to the estimated leading-edge point and performed. The method of claim 16, The TDoA calculation is performed in the case of not being identical, and the TDoA initialization is performed by finding a point that is the least common multiple of the length of the OFDM signal (effective symbol + guard symbol) and the TPS start point of the first and second transmitting stations. OFDM signal based position recognition method characterized in that for performing the TDoA calculation on the basis of the point to be the least common multiple and the TPS start point. The method of claim 16, The TDoA calculation is performed by extracting a TPS from the OFDM signal from which the leading-edge point is estimated. The method of claim 22, OFDM signal based position recognition method, characterized in that for accumulating the extracted TPS a predetermined number of times through a storage device to improve the TPS detection rate. The method of claim 23, wherein The TPS is stored in the memory device as a real part (I) and an imaginary part (Q) signal, and the number of times the pilot of the TPS is accumulated is controlled by an average frequency adjuster. The average frequency adjuster receives the bit error information from RSSI information and the Bose-Chaudhuri-Hocquenghem (BCH) decoder and calculates the cumulative frequency. The method of claim 16, The position recognition method is an OFDM signal-based position recognition method characterized in that the position recognition in conjunction with a cellular network-based position recognition method, GPS-based position recognition method or a cellular network and GPS-based position recognition method.

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