KR100617092B1 - Pilot order estimator and method of digital broadcasting receiver - Google Patents

Abstract

The present invention relates to a distributed pilot order estimation apparatus and method in a DVB broadcast receiver using an OFDM transmission scheme. In particular, the present invention estimates the order of distributed pilots using the correlation between the four patterns of reference distributed pilot information and the received triplex data, so that the fine symbol timing synchronization and the channel equalizer are correctly estimated even in a long ghost environment in an SFN network. It is possible to perform channel estimation and fine window offset estimation with the distributed pilot.

Distributed Pilot, Correlation, Symbol Timing Synchronization, Channel Equalization

Description

Pilot order estimator and method of digital broadcasting receiver

1 is a view showing the structure of a transmission frame of a general DVB method

2 is a schematic diagram of a digital broadcast receiver with a distributed pilot order estimation apparatus in accordance with the present invention.

FIG. 3 is a detailed block diagram illustrating an embodiment of the reception synchronizer of FIG. 2. FIG.

4 is a detailed block diagram illustrating an embodiment of the distributed pilot order estimator of FIG. 3.

5 is a detailed block diagram illustrating an embodiment of the reference distributed pilot generator of FIG. 4.

FIG. 6 is a detailed block diagram illustrating an embodiment of the triple data extractor of FIG. 4.

FIG. 7 is a detailed block diagram of one embodiment of the correlator of FIG.

8 is a detailed block diagram illustrating one embodiment of the distributed pilot aligner of FIG.

9 is a detailed block diagram illustrating an embodiment of the distributed pilot order detector of FIG. 4.

Explanation of symbols for main parts of the drawings

301: Approximate symbol timing synchronization unit 302: Fractional carrier synchronization unit

303: FFT unit 304: integer unit carrier synchronization unit

305: sampling frequency synchronizer 306: distributed pilot order estimator

307: Fine symbol timing synchronizer 308: Equalizer

401: reference distributed pilot generator 402: triplex data extractor

403 Correlator 404 Distributed Pilot Aligner

405: Distributed Pilot Sequence Detector

The present invention relates to a digital broadcast receiver, and more particularly, to an apparatus and method for estimating a scattered pilot order in a digital broadcast receiver of an OFDM transmission method.

Digital Video Broadcasting-Terrestrial (DVB-T) and DVB-Handheld (DVB-H), which have been selected as the European standard for terrestrial and mobile channels of digital TVs, adopt Orthogonal Frequency Division Multiplexing (OFDM) transmission methods. The OFDM transmission scheme is known as a strong transmission scheme for channel distortion due to multiple paths in a wireless broadband broadcasting system.

1 illustrates a frame structure of the above-described DVB-T and DVB-H, and is composed of distributed pilots, continuous pilots, and transmission parameters signaling (TPS) in addition to payloads.

The distributed pilot has four distributed pilots of 17 groups in one frame (for example, 68 OFDM symbols). In this case, it is necessary to accurately estimate the order of distributed pilots in order to function as a fine window offset and a channel equalizer.

The continuous pilot is always located in the same subcarrier regardless of the OFDM symbol. The continuous pilot is required for carrier frequency offset estimation and sampling clock synchronization.

The TPS is signal parameters related to a transmission structure such as channel coding and modulation. The TPS is transmitted in parallel per symbol. For example, 17 TPS is transmitted in the 2K mode and 68 TPS is transmitted in the 8K mode. All TPS carriers convey the same information in the same symbol.

However, the above-described OFDM transmission scheme is sensitive to synchronization (symbol synchronization, frequency synchronization, timing synchronization), and thus, when accurate synchronization between transmission / reception is not possible, distortion of a received signal occurs, and many studies have been conducted to solve this problem. .

In addition, estimating the order of distributed pilots in the DVB-T and DVB-H transmission frame structure is an essential part of the design of the DVB receive synchronizer. The fine symbol timing synchronization and the channel equalizer have a correctly estimated distributed pilot, Fine window offset estimation can be performed. In particular, long ghosts exist in SFN networks, and in this channel environment, it is difficult to accurately estimate the order of distributed pilots at once.

That is, the distortion of the distributed pilot due to the long ghost in the SFN network causes incorrect distributed pilot order estimation, which makes it impossible to perform fine symbol timing synchronization and equalizer.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an apparatus and method for accurately estimating the order of distributed pilots even under ghost conditions.

In order to achieve the above object, the present invention provides a distributed pilot order estimating apparatus, comprising: a data extractor for extracting and outputting triplex data from an OFDM signal in a frequency domain sampled and input; A correlator configured to calculate and output a correlation power value between the triplex data extracted by the data extractor and a reference distributed pilot having first to fourth patterns; A distributed pilot aligner for calculating and outputting the cumulative correlation power values of the first to fourth distributed pilots from the correlation power values output from the correlator; And a distributed pilot having a first pattern among consecutive OFDM symbols in a frequency domain sampled and input after comparing the magnitudes of the first through fourth cumulative distributed pilot correlation power values output from the distributed pilot aligner. It characterized in that it comprises a distributed pilot order detector for selecting and outputting.

The distributed pilot sorter classifies the input correlation power value into any one of a 1st distributed pilot correlation power value, a 2nd distributed pilot correlation power value, a 3rd distributed pilot correlation power value, and a 4th distributed pilot correlation power value at every OFDM symbol interval. It is characterized by accumulating.

The distributed pilot sorter may include a distributed pilot order counter for generating a count value indicating a sequence of correlation power values currently input, and a correlation power value input according to a count value of the distributed pilot order counter. After receiving the demultiplexer classified into any one of the distributed pilot correlation power value, the 3rd distributed pilot correlation power value, and the 4th distributed pilot correlation power value, and the corresponding distributed pilot correlation power values classified by the demultiplexer, accumulating them at every OFDM symbol interval, and then accumulating them. And a first to fourth distributed pilot correlation power accumulator for outputting.

The distributed pilot order detector compares the magnitudes of the first to fourth cumulative distributed pilot correlation power values to be input, and generates a control signal indicating a start time of an OFDM symbol including a distributed pilot of a first pattern according to a comparison result. And a selector for outputting a distributed pilot start detector and a control signal of the distributed pilot start detector to select and output an OFDM symbol input at this time when the control signal of the distributed pilot start detector notifies a start time of an OFDM symbol including a distributed pilot of a first pattern. It features.

Pilot order estimation method in a digital broadcast receiver according to the present invention,

(a) extracting and outputting triplex data from an OFDM signal in a frequency domain sampled and input;

(b) calculating and outputting a correlation power value between the triplet data and a reference distributed pilot having first to fourth patterns;

(c) calculating and outputting the cumulative correlation power values of the first to fourth distributed pilots from the correlation power values of step (b), respectively; And

(d) after comparing the magnitudes of the first to fourth cumulative distributed pilot correlation power values, selecting and outputting an OFDM symbol including a distributed pilot having a first pattern among consecutive OFDM symbols in a frequency domain sampled and inputted; Characterized in that comprises a step.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention that can specifically realize the above object will be described. At this time, the configuration and operation of the present invention shown in the drawings and described by it will be described as at least one embodiment, by which the technical spirit of the present invention and its core configuration and operation is not limited.

2 is a schematic diagram of a digital broadcast receiver having a reception synchronizer 201 equipped with a scattered pilot order estimator (SPOE) according to the present invention.

3 is a detailed block diagram illustrating an exemplary embodiment of the reception synchronizer, including a coarse symbol timing recovery (CSTS) unit 301, a fractional carrier synchronization unit (302), and a high speed Fourier transform (FFT) unit 303, integer carrier carrier (ICFS) unit 304, sampling frequency synchronization (SFS) unit 305, distributed pilot order estimation (SPOE) unit 306, fine symbol A fine symbol timing recovery (FSTS) unit 307 and a channel equalizer 308 are provided.

That is, since the multi-carrier modulation scheme, which is a transmission scheme of the DVB transmission system, transmits information in parallel using FFT / IFFT, the IFFT output of the transmitter must be rearranged and inputted into the FFT of the receiver. In this case, since a guard interval is inserted between the symbols and transmitted in order to prevent interference between symbols, the symbol sequence is output from a sample string output from an A / D converter (not shown) in the preprocessor 200 of the receiver. After detecting the starting point, the effective sample sequence with the guard interval removed must be entered into the FFT. Therefore, the approximate symbol timing synchronizer (or the approximate FFT window position reconstructor) 301 extracts only valid data samples excluding the guard interval from the received sample sequence and then passes through the fractional carrier synchronizer 302. Output to FFT section 303.

In this case, if the FFT window error is very serious, the value after the FFT cannot be used.However, if the error is small, the distortion due to the adjacent symbol is very small and does not greatly affect the time shift. This time transition is shown as a phase rotation at each frequency in the frequency axis which is the output of the FFT unit 303.

On the other hand, in the OFDM scheme, unlike the single broadcast transmission scheme, carrier recovery is configured to operate in two modes, namely, the fractional carrier synchronizer 302 and the integer carrier synchronizer 304. The integer carrier synchronizer 304 estimates and compensates an integer multiple of the nearest subcarrier interval with respect to the initial frequency offset, and the minority carrier synchronizer 302 estimates and compensates a frequency offset less than half the subcarrier interval.

That is, the fractional and integer carrier carriers 302 and 304 remove frequency offset and phase noise of a carrier by a tuner and a mixer (not shown) of the preprocessor 200. At the same time, the bandpass digital signal is converted into a baseband digital signal.

In addition, the received continuous OFDM signal is sampled at a rated periodic interval determined by the sampling frequency. Since the sampled signal is processed as a digital signal such as a demodulation process through the FFT unit 303, the function of finding an optimal sampling timing is very important in an OFDM system. This is performed by the sampling frequency synchronizer 305. At this time, the sampling frequency error is divided into a sampling clock phase offset and a sampling clock frequency offset. The sampling clock phase offset occurs when the sampling clock speeds of the transmission / reception periods coincide with each other, but the sampling timings of the transmission / reception periods do not coincide. Can be defined as an error. The sampling clock frequency offset is defined as a sampling frequency difference generated when the sampling clock speeds do not coincide with each other in the transmission / reception period.

The distributed pilot order estimator 306 estimates the order of the distributed pilots that are regularly generated for every four OFDM symbols, and the result is the fine symbol timing synchronization (ie, the fine window offset estimation) and the channel equalizer 308. Used to get the channel transfer function.

4 is a detailed block diagram illustrating an embodiment of the distributed pilot order estimator 306, including a reference distributed pilot generator 401, a triple data extractor 402, a correlator 403, A distributed pilot arrangement 404, and a distributed pilot order detector 405.

The reference distributed pilot generator 401 generates four patterns of distributed pilots that constitute a known DVB frame by an appointment between transmitters and receivers. That is, the distributed pilot has a feature of repeating every four OFDM symbols.

FIG. 5 is a detailed block diagram showing an embodiment of the reference distributed pilot generator 401, and includes a PRBS sequence generator 501 and a reference distributed pilot extractor 502. As shown in FIG.

The PRBS sequence generator 501 generates a DVB frame PRBS sequence and outputs it to the reference distributed pilot extractor 502. The reference distributed pilot extractor 502 extracts PRBS bit values of known distributed pilot positions and outputs them to the correlator 403 as the reference distributed pilot. That is, the reference distributed pilot extractor 502 repeatedly extracts the reference distributed pilots sp_real and sp_imaginary for every four OFDM symbols and outputs them to the correlator 403.

The triplex data extractor 402 extracts triplex data from the constellations (fft_real, fft_imaginary) of the frequency domain to which the sampling clock generated from the sampling frequency synchronizer 305 is synchronized and outputs the data to the correlator 403.

FIG. 6 is a detailed block diagram showing an embodiment of the triple data extractor 402 and includes a latch 601 and a triple counter 602.

The multiplier counter 602 is a counter for calculating a multiplier, and the latch 601 extracts triplex data (triple_real, triple_imaginary) from the input signal constellation according to the count signal generated by the multiplier counter 602. Output to correlator 403.

The correlator 403 estimates the correlation between the distributed pilot of the four patterns generated by the reference distributed pilot generator 401 and the tripled data extracted by the tripled data extractor 402 to the distributed pilot sorter 404. Output

FIG. 7 is a detailed block diagram showing an embodiment of the correlator 403, and includes a complex multiplier 701 and a square 702. As shown in FIG.

The complex multiplier 701 performs a conjugate product of the reference variance pilot generated by the reference variance pilot generator 401 and the triple fold data extracted by the triple fold data extractor 402 and multiplies the result by a square ( 702). The square 702 takes a square of the output of the complex multiplier 701 and outputs it to the distributed pilot aligner 404 as a correlation value corr_power.

The distributed pilot aligner 404 calculates the cumulative correlation power value of each distributed pilot from the correlation value estimated by the correlator 403 and outputs it to the distributed pilot order detector 405.

FIG. 8 is a detailed block diagram showing an embodiment of the distributed pilot aligner 404, which includes a demultiplexer 801, a distributed pilot order counter 802, and a distributed pilot correlated power accumulator 803. As shown in FIG.

The demultiplexer 801 outputs and accumulates a correlation value corr_power inputted using the output of the distributed pilot order counter 802 as a selection signal to a corresponding accumulator of the distributed pilot correlation power accumulator 803. That is, since the distributed pilot order counter 802 can know which of the four reference distributed pilot patterns the current correlation value is input, the demultiplexer 801 uses the 1st distributed pilot correlation power value, 2nd, as the correlation value. It may be classified into a distributed pilot correlation power value, a 3rd distributed pilot correlation power value, and a 4th distributed pilot correlation power value. In this case, the distributed pilot of the first (1st) pattern is a case where the first distributed pilot is inserted at the beginning of one OFDM symbol, that is, the first subcarrier position.

That is, the 1st distributed pilot correlation power value is output to the 1st distributed pilot accumulator 811 of the distributed pilot correlation power accumulator 803 and accumulated at every OFDM symbol interval, and the 2nd distributed pilot correlation power value is a 2nd distributed pilot. The accumulator 812 is output to the accumulator 812 and accumulated at every OFDM symbol interval. Similarly, the 3rd distributed pilot correlation power value is output to the 3rd distributed pilot accumulator 813 of the distributed pilot correlation power accumulator 803 and accumulated at every OFDM symbol interval, and the 4th distributed pilot correlation power value is accumulated at the 4th distributed pilot accumulation power. The data is output to the group 814 and accumulated at every OFDM symbol interval.

The distributed pilot correlation power values accumulated in the first to fourth distributed pilot accumulators 811 to 814 are output to the distributed pilot order detector 405.

The distributed pilot order detector 405 compares the magnitudes of the first to fourth cumulative distributed pilot correlation power values output from the distributed pilot sorter 404, and then includes 1st distributed pilots among consecutively input OFDM symbols. The OFDM symbol is detected to inform the fine symbol timing synchronizer 307 and equalizer 308 the start of the input data.

9 is a detailed block diagram showing an embodiment of the distributed pilot alignment order detector 405, which is composed of a 1st distributed pilot start detector 901 and a selector 902. As shown in FIG.

The 1st distributed pilot start detector 901 compares the magnitudes of the first to fourth cumulative distributed pilot correlation power values to be input, generates a control signal indicating the start time of the OFDM symbol including the 1st distributed pilot, and selector 902. )

The selector 902 selects 0 and outputs it to the fine symbol timing synchronizer 307 and the equalizer 308 until the control signal informs the start time of the OFDM symbol including the 1st distributed pilot. Then, when the control signal indicates the start time including the 1st distributed pilot, the OFDM symbol (fft_real, fft_imaginary) output from the sampling frequency synchronizer 305 is selected to the fine symbol timing synchronizer 307 and the equalizer 308. Output

The fine symbol timing synchronizer 307 and the equalizer 308 perform their respective functions in synchronization with the lock signal of the distributed pilot order detector 405.

In this case, it can be seen that the present invention takes up to four OFDM symbol times to estimate the 1st distributed pilot.

In addition, the present invention can be applied to both DVB-H receiver and DVB-T receiver.

On the other hand, the terms used in the present invention (terminology) are terms defined in consideration of the functions in the present invention may vary according to the intention or practice of those skilled in the art, the definitions are the overall contents of the present invention It should be based on.

The present invention is not limited to the above-described embodiments, and can be modified by those skilled in the art as can be seen from the appended claims, and such modifications are within the scope of the present invention. .

The apparatus and method for estimating a distributed pilot order of a digital broadcast receiver according to the present invention described above use the correlation to estimate the order of the distributed pilot, so that the fine symbol timing synchronization and the channel equalizer have a correctly estimated distributed pilot and estimate the channel. Fine window offset estimation can be performed.

In particular, even in a long ghost environment in an SFN network, the order of distributed pilots can be estimated accurately.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (9)

A data extractor for extracting and outputting data in units of N multiples from an OFDM signal in a frequency domain sampled and input; A correlator that calculates and outputs a correlation power value between the N-fold data extracted by the data extractor and a reference distributed pilot having first to fourth patterns; A distributed pilot aligner for calculating and outputting the cumulative correlation power values of the first to fourth distributed pilots from the correlation power values output from the correlator; And After comparing the magnitudes of the first to fourth cumulative distributed pilot correlation power values output from the distributed pilot aligner, an OFDM symbol including a distributed pilot having a first pattern among consecutive OFDM symbols in a frequency domain sampled and input is obtained. And a distributed pilot order detector for selecting and outputting the pilot order estimator. The method of claim 1, wherein the data extractor A counter that counts in multiples of three, And a latch for extracting and outputting triplex data according to a count signal generated by the triplex counter from an OFDM signal of a frequency domain sampled and input. The distributed pilot aligner of claim 1, wherein The input correlation power value is classified into one of 1st distributed pilot correlation power value, 2nd distributed pilot correlation power value, 3rd distributed pilot correlation power value, and 4th distributed pilot correlation power value, and accumulated at every OFDM symbol interval. Pilot order estimation apparatus in a digital broadcast receiver. The distributed pilot aligner of claim 1, wherein A distributed pilot order counter for generating a count value indicating the order of the currently input correlation power value, The demultiplexer classifies the correlation power value input according to the count value of the distributed pilot order counter into any one of a 1st distributed pilot correlation power value, a 2nd distributed pilot correlation power value, a 3rd distributed pilot correlation power value, and a 4th distributed pilot correlation power value. Wow, Pilot order estimator in the digital broadcast receiver, characterized in that the first to fourth distributed pilot correlation power accumulator for receiving the corresponding distributed pilot correlation power value classified by the demultiplexer and accumulates at every OFDM symbol interval and outputs the result. . 5. The method of claim 4, wherein the distributed pilot order detector is Distributed pilot start detector for comparing the magnitudes of the first to fourth cumulative distributed pilot correlation power values input, and generating and outputting a control signal indicating a start time of an OFDM symbol including a distributed pilot of a first pattern according to a comparison result Wow, When the control signal of the distributed pilot start detector informs the start time of the OFDM symbol including the distributed pilot of the first pattern comprises a selector for selecting and outputting the input OFDM symbol at this time Pilot order estimator. The method of claim 4, wherein The distributed pilot of the first pattern is a pilot order estimation apparatus in a digital broadcast receiver, characterized in that the pattern is a scattered pilot inserted into the first subcarrier position of one OFDM symbol. (a) extracting and outputting triplex data from an OFDM signal in a frequency domain sampled and input; (b) calculating and outputting a correlation power value between the triplet data and a reference distributed pilot having first to fourth patterns; (c) calculating and outputting the cumulative correlation power values of the first to fourth distributed pilots from the correlation power values of step (b), respectively; And (d) after comparing the magnitudes of the first to fourth cumulative distributed pilot correlation power values, selecting and outputting an OFDM symbol including a distributed pilot having a first pattern among consecutive OFDM symbols in a frequency domain sampled and inputted And a method for estimating pilot order in a digital broadcast receiver. 8. The method of claim 7, wherein step (c) The input correlation power value is classified into one of 1st distributed pilot correlation power value, 2nd distributed pilot correlation power value, 3rd distributed pilot correlation power value, and 4th distributed pilot correlation power value, and accumulated at every OFDM symbol interval. A pilot order estimation method in a digital broadcast receiver. 8. The method of claim 7, wherein step (d) Comparing the magnitudes of the first to fourth cumulative distributed pilot correlation power values accumulated and input at every OFDM symbol interval, and notifying a start point of an OFDM symbol including a distributed pilot of a first pattern according to a comparison result; And informing the start point of the OFDM symbol including the distributed pilot of the first pattern, selecting and outputting the input OFDM symbol at this time.

Images