KR20090128372A - Ofdm receiving apparatus and receiving method thereof - Google Patents

Abstract

PURPOSE: An OFDM receiving apparatus and receiving method thereof are provided to prevent the unnecessary process of signal by rapidly detecting the information about the service mode. CONSTITUTION: The synchronization portion(100) receives a message the carrier signal and recompenses the frequency offset and timing offset. The service mode detection part(110) detects the service mode corresponding to the pseudo noise sequence level outputted from the synchronization portion. The FFT(fast fourier transform) part(120) outputs the signal by changing the signal outputted from the synchronization portion. The FEC(forward error correction) part(130) performs the error correction about output data. The information for pseudo noise code has the power level corresponding to the service mode of the received carrier signal with the information for pseudo noise code.

Description

OPDM receiving apparatus and receiving method

The present invention relates to an Orthogonal Frequency Division Multiplexing (OFDM) receiver and a receiving method thereof, and more particularly, to Time Domain Synchronous-OFDM (hereinafter, referred to as 'TDS-OFDM'). The present invention relates to an OMD receiver and a method for receiving the OMD signal modulated using the scheme, and capable of quickly detecting a service mode before restoration of the received OMD signal.

In general, the UFDM method includes digital audio broadcasting (DAB), terrestrial digital television broadcasting, wireless local area network (WLAN), and wireless asynchronous transfer mode (WATM). Are widely used in digital transmission technology. The OMD system refers to an orthogonal frequency division multiplexing scheme, which divides data to be transmitted into several pieces, modulates the divided data using hundreds of carriers (subcarriers), and transmits them in parallel. The UFDM method is a digital modulation method for improving the transmission rate per bandwidth and preventing multipath interference. The OPM is transmitted while maintaining orthogonality between subcarriers, thereby achieving optimum transmission efficiency in high-speed data transmission. Has characteristics.

On the other hand, TDS-OFDM is an OFM system using synchronization in the time domain, and forms one of the OFM systems together with VOFDM (Vector Orthogonal Frequency Division Multiplexing) and COFDM (Coded Orthogonal Frequency Division Multiplexing). In the transmission apparatus using the TDS-OFDM scheme, the OMD signal is transmitted using time domain synchronization, and the OMD transmission signal allocated for the preset frequency band is rearranged along the time axis. In addition, in the TDS-OFDM transmission apparatus, as shown in FIG. 1, a guard interval (GI) is inserted in front of the OMD transmission signal formed along the time axis to suppress interference between signals, and is protected. The synchronization information using pseudo noise sequence information is inserted in front of the interval and transmitted. The pseudo-noise string information is used as synchronization information for predicting the synchronization and the channel of the OMD signal received by the OMD receiver which receives the transmitted OMD signal.

 2 is a block diagram illustrating an example of an OMD receiver for receiving a modulated signal using a conventional TDS-OFDM scheme. Referring to the drawings, the conventional OMD receiver includes a synchronization unit 10, FFT unit 20, TPS extraction and decoding unit 30, and FEC unit 40.

The synchronizer 10 compensates the frequency offset and the timing offset with respect to the signal received through the antenna. The FFT unit 20 performs fast Fourier transform of the signal output from the synchronizer 10 into a signal in the frequency domain. The TPS extraction and decoding unit 30 extracts a transmission parameter signal (TPS) included in the signal output from the FFT unit 20 and performs a decoding process. The FEC unit 40 performs an error correction decoding process to correct an error occurring during transmission.

In this configuration, the information about the service mode is included in the TPS and transmitted, and is carried on a TPS determined subcarrier. The information on the service mode means information on the type of data, such as a digital TV (DTV) signal, a mobile communication signal, or a mobile text service signal, or information such as an FEC code rate or a type of FEC used. It can be used in FEC process or source decoding process.

Therefore, in order to detect such information about the service mode, it can be known after extracting and decoding the TPS from the fast Fourier-processed signal in the FFT unit 20. That is, in order to detect the information about the service mode, the received signal can be detected only after the synchronization, FFT process, TPS extraction and decoding process. Therefore, as in the case of receiving a mobile communication signal in a receiver for receiving a digital TV (DTV) signal, unnecessary signal processing is performed on a signal that does not need to be processed by the receiver, thereby wasting resources. The problem arises.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to quickly recover a received OFM signal in a receiving apparatus that receives a modulated signal using the TDS-OFDM scheme. The present invention provides an OMD receiver and a method for receiving the same, which detect information about a service mode and prevent unnecessary signal processing.

In accordance with another aspect of the present invention, an OMD receiver according to the present invention includes a synchronizer configured to receive a transmission signal and output a signal compensated for a frequency offset and a timing offset, and a pseudo noise string (PN) in a signal output from the synchronizer. sequence) a service mode detection unit for detecting a service mode corresponding to a level, an FFT unit for converting and outputting a signal output from the synchronization unit into a signal in a frequency domain, and an FEC unit for performing error correction on the output data, The transmission signal received by the OMD receiver has PN sequence information having a power level corresponding to a service mode of the received transmission signal.

Here, the service mode may be one of a digital TV (DTV) broadcasting mode, a mobile communication mode, and a mobile text service mode.

In addition, the power level of the pseudo-noise sequence information may be lowered in the order of the digital TV broadcasting mode, the mobile communication mode, and the mobile text service mode.

On the other hand, in the method of receiving the OFM die according to an embodiment of the present invention, receiving a transmission signal, performing synchronization on the received signal, outputting a signal compensated for the frequency offset and timing offset, the output signal Detecting a service mode corresponding to a PN sequence level, converting the synchronized signal into a signal in a frequency domain and outputting the signal, and performing error correction decoding on the output data; The received transmission signal has PN sequence information having a power level corresponding to a service mode of the received transmission signal.

Here, the service mode may be one of a digital TV broadcasting mode, a mobile communication mode, and a mobile text service mode.

In addition, the power level of the pseudo-noise sequence information may be lowered in the order of the digital TV broadcasting mode, the mobile communication mode, and the mobile text service mode.

Hereinafter, with reference to the drawings will be described the present invention in more detail.

3 is a block diagram of an OMD receiver according to the present invention. The OMD receiver receives and processes a modulated signal using a TDS-OFDM scheme, and includes a synchronizer 100, a service mode detector 110, a fast fourier transform (FFT) unit 120, and an FEC. (Forward Error Correction) section 130 is provided.

The synchronizer 100 compensates for the frequency offset and the timing offset with respect to the signal received through the antenna. The FFT unit 120 performs fast Fourier transform of a signal in the time domain output from the synchronizer 100 into a signal in the frequency domain. The FEC unit 130 corrects an error occurring during transmission included in the signal converted into the signal in the frequency domain by the FFT unit 120. The service mode detector 110 receives a signal output from the synchronizer 100 and determines a service mode of the received signal.

In this configuration, the signal received through the antenna frame is synchronized to the synchronization unit 100 and transmitted to the service mode detection unit 110, the service mode detection unit 110 is a pseudo noise sequence (PN sequence) information and error in the synchronized signal The power ratio between the FDM signals is detected to determine a service mode with respect to the received signal. That is, the signal received by the OSF receiver according to the present invention is modulated using the TDS-OFDM scheme, and the pseudo noise noise information and the power ratio between the OSF signals vary according to a predetermined service mode. It should be a signal whose level value of the noise string information is variable.

For example, such a transmission signal can be generated from the FM transmitter, as shown in FIG. Referring to FIG. 4, the illustrated OFM transmitter includes an FEC coding unit 200, an Inverse Discrete Fourier Transform (IDFT) unit 200, a Guard Interval (GI) insertion unit 220, and a mode information setting unit 230. ), An additional information insertion unit 240, a shaping filter 250, and an RF amplifier 260.

The FEC coding unit 200 performs error correction encoding to correct an error that may occur in transmission on the OMD signal to be transmitted. The IDFT unit 210 performs an Inverse Discrete Fourier Transform that rearranges the OFM signal formed based on the frequency coded by the FEC encoder 200 based on time. The GI insertion unit 220 inserts a guard interval for suppressing interference between neighboring OFM die symbols with respect to the OFM die signal in which the inverse discrete Fourier transform is performed in the IDFT unit 210. The mode information setting unit 230 sets the level value according to the service mode provided for the OMD signal transmitting pseudo noise string information to be inserted into the OMD signal inserted with the protection interval for synchronizing the OMD signal. Set it to variable.

The additional information inserting unit 240 has a level value that is variably set in response to the service mode of the OPM signal in the mode information setting unit 230 in the OS signal of which the protection interval is inserted in the GI insertion unit 220. PN 'is inserted. The shaping filter 250 shaping filters the signal output from the additional information insertion unit 240. The RF amplifier 260 high frequency amplifies the OPM signal filtered by the shaping filter 250. The amplified OMD signal thus amplified is transmitted through the antenna.

In the OMD transmission apparatus having such a configuration, the pseudo-noise sequence information as the synchronization information is inserted with the level value varied according to the service mode provided instead of the constant level value. That is, the level value of the pseudo noise string information is varied and set according to the service mode, and the pseudo noise string information PN 'having the set level value is inserted into the OPM signal with the protection section inserted. Accordingly, the OMD receiver may determine the service mode of the OMD signal received through the pseudo-noise string information of the set level value inserted in the OMD signal before restoring the OMD signal. . At this time, the mode information setting unit 230 variably sets the power level of the pseudo-noise string information according to the service mode and provides the additional information insertion unit 240, and the receiving device of the OMD signal inserted with the protection section is provided. The service mode may be detected by detecting a ratio of power to power of pseudonoisy heat information.

On the other hand, examples of the service mode include data types such as DTV broadcasting mode, mobile communication mode, and mobile text service mode. In this case, the mode information setting unit 230 provides the digital TV broadcasting mode, the mobile communication mode, and the mobile text service mode when the service mode of the OS signal is provided. The highest level value is set in the broadcast mode, and the smallest level value is set in the order of the mobile communication mode and the mobile text service mode. For example, if the service mode is a digital TV broadcasting mode, the ratio of pseudo noise trains to FM signals is set to 6 dB, and if the service mode is mobile communication mode, power ratios of pseudo noise trains to FM signals are set to 4 dB. If the service mode is the moving text service mode, the power ratio of the pseudo noise string information to the FM signal can be set to 2 dB.

FIG. 5 is a diagram illustrating a frame structure of an OMD signal output from the additional information insertion unit 240 of FIG. 4. Referring to the drawings, the frame of the OMD signal is changed in accordance with the service mode in the mode information setting unit 240 pseudo noise string information (PN ') having a set level value, the guard interval (GI), and OF Die symbol (OFDM). Here, the OMD symbol is information for substantially restoring in the OMD receiver, and the guard period GI is an interval allocated to suppress interference between the OMD symbols transmitted. As described above, the pseudo-noise sequence PN 'information set by the mode information setting unit 240 has a level value that varies according to the service mode of the OMD signal.

For more details on the OMD transmitter described in FIGS. 4 and 5, the level value of the pseudo-noise string is varied according to the service mode of the presently filed Korean application No. 2002-30391 to be inserted into the OFM signal. Which is part of the present invention, which is incorporated herein by reference.

6 is a flowchart for explaining an example of an operation method of the OS receiving apparatus according to the present invention. In the operation method described in the flowchart, it is assumed that a signal transmitted from an OMD transmitter as described with reference to FIGS. 4 and 5 is received.

Referring to the flowchart, the synchronizer 100 performs frequency synchronization and time synchronization on a signal received through an antenna (S400). The signal synchronized in the synchronizer 100 is transmitted to the service mode detector 110, and the service mode detector 110 detects a power ratio of a pseudo noise string (S410). Here, the power ratio of the pseudo-noise sequence means the power ratio of the pseudo-noise sequence information (PN '), the protection period and the OMD symbol.

The service mode detector 110 first determines whether the power ratio of the pseudo noise string is 6 dB (S420). At this time, the error range is considered and the same is true in the subsequent judgment process. As a result of the determination of the service mode detection unit 110, when the power ratio of the pseudo noise string is 6 dB, it is determined as the DTV broadcasting mode (S430). If it is determined in step S420 that it is not 6dB, the service mode detection unit 110 again determines whether or not the power ratio of the pseudo-noise sequence is 4dB (S440), and if the determination result is 4dB (S450). In addition, if it is determined in step S440 not 4dB, the service mode detector 110 again determines whether or not the power ratio of the pseudo-noise sequence is 2dB (S460). As a result of the determination, it is determined that the mobile character service mode is 2dB (S470), otherwise, the process ends.

As described above, according to the determination result of the service mode of the service mode detection unit 110, a subsequent signal processing process is performed. That is, in the case where the OS receiver is a receiver for DTV broadcasting, the restoration process for the OS FM signal is performed only when the service mode is the DTV broadcasting mode according to the determination result of the service mode of the received signal. In other service modes, the received signal may be ignored and unnecessary signal processing may be omitted. Similarly, the case where the OS receiver is used in a mobile communication environment or a mobile text service environment is processed in the same manner. Therefore, after the synchronization process, it is possible to quickly detect the service mode of the signal, thereby avoiding unnecessary signal processing process it is possible to use resources more efficiently.

In addition, in the above embodiment, the type of service mode is described as an example of DTV broadcasting mode, mobile communication mode, and moving text service mode, but the type of service mode is not limited thereto, and various applications are possible.

As described above, according to the present invention, before restoring the received OMD signal, the level value of the pseudo-noise string inserted into the OFM signal is detected to quickly detect the service mode of the received OMD signal. Can be. As a result, unnecessary signal processing may be prevented, and resources may be used more efficiently. Since only necessary signals may be processed, unnecessary waste of power may be prevented.

In addition, although the preferred embodiment of the present invention has been shown and described above, the present invention is not limited to the specific embodiments described above, but the technical field to which the invention belongs without departing from the spirit of the invention claimed in the claims. Of course, various modifications can be made by those skilled in the art, and these modifications should not be individually understood from the technical spirit or the prospect of the present invention.

1 is a diagram showing the structure of a TDS-OFDM symbol;

2 is a block diagram of an OFM receiver using a conventional TDS-OFDM scheme;

3 is a block diagram of an OMD receiver according to the present invention;

Figure 4 is a block diagram of the FM transmitter for the FM receiver according to the present invention,

5 is a diagram illustrating a structure of an OMD signal output from the additional information inserting unit in the OMD transmitter of FIG. 4; and

6 is a flowchart illustrating an example of an operating method of the OSDM receiving apparatus according to the present invention.

Explanation of symbols on the main parts of the drawings

100: synchronization unit 110: service mode detection unit

120: FFT unit 130: FEC unit

Claims (6)

In the OMD receiver, A synchronization unit for receiving a transmission signal and outputting a signal compensated for a frequency offset and a timing offset; A service mode detector for detecting a service mode corresponding to a PN sequence level in the signal output from the synchronizer; An FFT unit converting the signal output from the synchronization unit into a signal in a frequency domain and outputting the signal; And And an FEC unit for performing error correction on the output data. And the transmission signal received by the OPM receiver has PN sequence information having a power level corresponding to a service mode of the received transmission signal. The method of claim 1 The service mode is, The digital TV (DTV) broadcasting mode, the mobile communication mode, and the mobile SMS service mode, characterized in that the OMD receiving apparatus. The method of claim 2, And the power level of the pseudo-noise string information is lowered in the order of the digital TV broadcasting mode, the mobile communication mode, and the mobile text service mode. In receiving method of Receiving a transmission signal, performing synchronization on the received signal, and outputting a signal compensated for a frequency offset and a timing offset; Detecting a service mode corresponding to a PN sequence level of the output signal; An FFT conversion step of converting the synchronized signal into a signal in a frequency domain and outputting the converted signal; And Performing error correction decoding on the output data; And the received transmission signal has pseudo noise sequence (PN sequence) information having a power level corresponding to a service mode of the received transmission signal. The method of claim 4 The service mode is, A method of receiving an FM DM characterized by one of a digital TV broadcasting mode, a mobile communication mode, and a mobile text service mode. The method of claim 5, The power level of the pseudo-noise string information is lowered in order of the digital TV broadcasting mode, the mobile communication mode, and the mobile text service mode.

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