KR20030092656A - OFDM transmitter capable of regulating the level-value of PN according to service-mode of OFDM - Google Patents

Abstract

PURPOSE: An OFDM transmitter capable of varying a level value of a pseudo noise sequence according to a service mode to insert the varied level value into an OFDM signal is provided to allow an OFDM receiver to judge a service mode without restoring the OFDM signal. CONSTITUTION: An OFDM transmitter inserts pseudo noise sequence information that is synchronous information of an OFDM signal into the OFDM signal to perform time domain synchronous transmission. The OFDM transmitter includes a guard interval insertion unit(300), a mode information setting unit(400), and a mode information insertion unit(500). The guard interval insertion unit inserts a guard interval into the OFDM signal in order to restrain inter-symbol interference of the OFDM signal. The mode information setting unit variably sets a level value of the pseudo noise sequence information according to a service mode of the OFDM signal. The mode information insertion unit inserts the pseudo noise sequence information having the level value set corresponding to the service mode into the OFDM signal.

Description

FM transmitter capable of regulating the level-value of PN according to service-mode of OFDM}

The present invention relates to an Orthogonal Frequency Division Multiplexing (OFDM) transmitter, and more particularly, to a Pseudo Noise Sequence (PN), which is synchronization information of an ODP DM signal, and a service mode of an ODP DM signal. The present invention relates to an OMD transmitter that performs Time Domain Synchronous (TDS) transmission in a variable manner.

In general, a broadcasting system of a high definition television (HDTV) can be roughly divided into an image encoder and a modulator. The video encoder compresses digital data of about 1 Gbps obtained from a high quality video source into data of 15 to 18 Mbps. The modulator transmits several tens of Mbps of digital data to the receiver through a limited band channel of 6 to 8 MHz. Digital high-definition television broadcasting adopts a terrestrial simultaneous broadcasting method using a channel of a very high frequency (VHF) / ultra high frequency (UHF) band allocated for conventional television broadcasting. Therefore, the modulation scheme used in the high definition television broadcasting system must satisfy the following conditions due to the environment of terrestrial simultaneous broadcasting.

First, the modulation scheme used in the high-definition television broadcasting system requires high spectrum efficiency in order to transmit digital data of several tens of Mbps to a receiver through a limited band channel of 6 to 8 MHz. Second, the modulation scheme used in the high-definition television broadcasting system has multipath fading due to the surrounding buildings or structures, and therefore has a strong characteristic against fading. Third, modulation schemes used in high-definition television broadcasting systems inevitably cause co-channel interference by existing analog television signals, and thus have a strong characteristic against co-channel interference. In addition, digitally modulated signals of high-definition television systems should be able to minimize interference with existing analog television receivers.

Modulation techniques that meet these conditions include Quadrature Amplitude Modulation (QAM) and Residual Side Band (VSB) modulation. In terrestrial broadcasting, the multiplication of QAM and VSB is already limited. have. Here, the transmission rate is determined, and even if the symbol transmission rate is increased in the same multiple dimensions, the transmission rate of the bandwidth is improved. However, when the symbol transmission speeds of 16- / 32-inch quadrature amplitude modulation and 4-valued residual sideband modulation are increased, the interference caused by the interference between the second image and the multipath is severely generated. This is especially true in urban areas where skyscrapers are struggling.

Therefore, in order to solve these problems, Europe adopts Orthogonal Frequency Division Multiplexing (OFDM), a digital modulation method that can achieve the dual effect of improving the transmission speed per bandwidth and preventing interference, as a next-generation high-definition television terrestrial broadcasting method. Doing.

The OMD method converts a symbol string input in a serial form into parallel data of a predetermined block unit and then multiplexes the parallelized symbols with different subcarrier frequencies. The OMD system uses a multi-carrier, and has a considerable difference from the conventional single carrier. Multiple carriers have orthogonality with each other. Orthogonality means a property in which the product of two carriers becomes '0', which is a requirement for using multiple carriers. The implementation of the UFDM method is performed by the Fast Fourier Transform (FFT) and the Inverse Fast Fourier Transform (IFFT), which are simply obtained by the definition of orthogonality and fast Fourier transform between carriers. .

On the other hand, the advantages of the OMD method is as follows. The television terrestrial transmission system has channel characteristics in which reflected waves, co-channel interference, and adjacent channel interference affect transmission quality due to signal transmission, and thus design conditions of the transmission system are very demanding. However, the OS has strong characteristics in the multipath. That is, since multiple carriers are used, symbol transmission time can be increased. This is relatively insensitive to the interference signal due to the multipath, so there is little deterioration in performance even for a long time echo signal. In addition, since the existing signal has a strong property, there is little influence on co-channel interference. Due to this characteristic, a single frequency network (SFN) can be constructed. Here, the single frequency network means that one broadcast broadcasts the whole country on one frequency. As a result, co-channel interference becomes very severe, and since the OMD system is strong in such an environment, it can be used. Thus, using a single frequency network can efficiently use a limited frequency resources.

On the other hand, the FM signal is composed of multiple carriers and each carrier has a very small band. Thus, the overall spectral shape is almost square, resulting in a relatively higher frequency efficiency than a single carrier. In addition, the advantages of the UF DM method is that the waveform of the UF DM signal is the same as White Gaussian Noise, so the PAL (Phase Alternation by Line) and SECAM (Sequential Couleur a Memoire) methods are used. Has less interference than other broadcasting services. Accordingly, in the OMD system, the modulation scheme may be different for each carrier, so that hierarchical transmission is possible.

In general, an OPM transmitter that transmits an OFM signal using time domain synchronization re-assembles an OFM signal formed on a frequency axis that provides one service allocated to a preset frequency band along a time axis. Arrange. The OPM transmitter inserts a guard interval (GI) for suppressing interference between signals in front of the OFM signal formed along the time axis, and inserts synchronization information before the guard period and transmits it.

1 is a block diagram illustrating an OPM transmitter performing general time domain synchronous transmission. The FM transmitter has an inverse discrete fourier transform (IDFT) unit 10, a guard interval (GI) insertion unit 20, a pseudo noise sequence (PN) insertion unit 30, and a pulse shaping filter 40. .

The IDFT unit 10 performs an Inverse Discrete Fourier Transform that rearranges the OFM signal formed based on frequency based on time. The GI inserter 20 performs an IDFT unit 10. A guard interval is inserted to suppress interference between neighboring OFM die symbols with respect to the OFM die signal on which the inverse discrete Fourier transform is performed. The PN insertion unit 30 inserts Pseudo Noise Sequence (PN) information into the OMD symbol in which the protection interval is inserted. The pseudo-noise string information is synchronization information for predicting synchronization and channel of the OMD signal received by the OMD receiver which receives the transmitted OMD signal. At this time, the synchronization inserter 40 generates a pulse wave corresponding to the OMD signal into which the pseudo noise string information is inserted.

The pulse shaping filter 40 shaping and filtering the pulse wave so that a pulse wave corresponding to the OFM signal output from the PN insertion unit 30 is formed corresponding to the occupied band of the OMD signal to which the pulse signal is allocated. The molded filtered OMD signal is a high frequency amplified signal transmitted through the antenna 50.

On the other hand, the OPM transmitter performing such time domain synchronization (TDS) transmission may provide various types of services in the frame structure of the same OFM signal.

However, the conventional OMD transmitter transmits the pseudo-noise sequence information inserted into the OMD signal with the protection interval set to a constant level value regardless of the service type of the OMD signal, that is, the mode, to the ODM signal. Insert and send In general, the conventional noise noise sequence information inserted into the OPM signal has a power ratio of 6 dB of the noise noise sequence information with respect to the OFM signal into which the protection interval is inserted. Accordingly, the conventional OPM transmitter inserts pseudo-noise string information having a level value of 6 dB into the OFM signal including the protection interval, performs shaping filtering and high frequency amplification, and transmits it to the outside.

Therefore, the conventional OMD transmitter maintains a constant level value of the power ratio of the OMD signal in which the protection interval for the pseudo noise string is inserted, so the OMD receiver provides a service provided by the OMD transmitter. In order to know what kind of data is, the cumbersome operation of demodulating the OS symbol is followed.

In addition, when the OMD signal is transmitted using the conventional OMD transmitter, the OMD receiver determines whether the OMD signal is necessary by demodulating the OMD signal every time the OMD signal is received in order to receive the necessary signal. There is a problem that must be done.

The conventional OMD transmitter transmits pseudo noise string information having a constant level value to an OFM receiver inserted with a protection interval, regardless of the service type of the OMD signal, thereby inserting pseudo noise according to the service type. There is a problem in that power is wasted by taking pseudo-noise thermal information of the same level value even for a service for which the level value of thermal information is small.

An object of the present invention for solving the above problems is to easily determine the type of service provided by the receiving FM receiving side by variably allocating the power ratio of the OFM signal containing the inserted pseudo-noise information and protection intervals. It is to provide an OMD transmitter and a method for transmitting OMD using the same.

In addition, another object of the present invention for solving the above problems is generated by inserting and transmitting pseudo-noise string information having the same level value into the OPM signal inserted with the protection interval regardless of the type of service. The present invention provides an OMD transmitter capable of reducing power consumption and an OMD transmission method using the same.

1 is a block diagram showing an OFM transmitter performing general time domain synchronous transmission;

Figure 2 is a block diagram showing a preferred embodiment of the FM transmitter in accordance with the present invention,

3 is a diagram illustrating a frame structure of an OMD signal output from the additional information insertion unit of FIG. 2;

4 is a flowchart illustrating a preferred embodiment of a method of transmitting an OMD signal using an OMD transmitter according to the present invention; and

FIG. 5 is a flowchart illustrating the setting step of FIG. 4 in detail.

Explanation of symbols on the main parts of the drawings

100: FEC coding unit 200: IDFT unit

300: GI insertion unit 400: mode information setting unit

500: additional information insertion unit 600: molding filter

700: RF amplifier 800: antenna

According to the present invention, in the OMD transmitter for performing time-domain synchronous transmission by inserting pseudo-noise string information, which is the synchronization information of the OFM signal, into the OFM signal, a symbol of the OMD signal is used. GI insertion unit for inserting a protection interval into the OMD signal to suppress interference between modes, a mode information setting unit for setting the level value of pseudo noise string information variably according to the service mode of the OFM signal, and a protection section inserted Mode information insertion unit for inserting pseudo noise string information having a level value set in correspondence with the service mode, the pseudo noise string information having a set level value, and an OPM signal having a guard interval inserted therein. And a high frequency amplifier for high frequency amplifying the molded filtered OMD signal.

Preferably, the level value of the pseudo noise string information set in the mode information setting unit is the power ratio of the power of the pseudo-noise string information to the OPM signal with the protection section in the service mode.

Types of service modes include digital TV broadcasting mode, mobile communication mode, and mobile text service mode. Accordingly, the mode information setting unit sets the range of the level value of the pseudo noise string information to 0 dB to 2 dB when the service mode is the digital TV broadcasting mode. Further, the mode information setting unit sets the range of the level value of the pseudo noise string information to 2 dB to 4 dB when the service mode is a mobile communication mode. The mode information setting unit sets the range of the level value of the pseudo noise string information to 4 dB to 6 dB when the service mode is the moving character service mode.

On the other hand, according to the present invention, in accordance with the present invention, the OPM transmission method using an OMD transmitter which performs time-domain synchronous transmission by inserting pseudo-noise sequence information, which is the synchronization information of the OFM signal, into the OFM signal. Inserting a protection interval in the OMD signal to suppress the inter-symbol interference of the OMD signal, and variably setting the level of pseudo noise string information according to the service mode of the OMD signal; Inserting pseudo-noise sequence information having a level value set corresponding to the service mode to the OPM signal having a protection section inserted therein; shaping the pseudo-noise sequence information having a set level value and the OSF signal having a protection section inserted therein; OFM transmission method using an OMD transmitter comprising a step of filtering, and a high frequency amplification of the molded filtered OMD signal It is achieved by.

According to the present invention, the level value of pseudonoise string information is varied and set according to the service mode of the OMD signal provided, and the pseudonoise string information having the set level value is inserted into the OPM signal with the protection interval inserted. As a result, the service mode of the received FM signal may be determined based on the pseudo-noise string information of the set level value inserted in the FM signal before restoring the OS signal received by the FM receiver.

Accordingly, the OPM receiver can determine the service mode and receive the necessary service without restoring the OFM signal. In addition, by setting the level value of the pseudo noise sequence information variably according to the service mode provided, power consumption required for inserting the pseudo noise sequence information can be reduced.

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

Figure 2 is a block diagram showing a preferred embodiment of the FM transmitter in accordance with the present invention.

The FM transmitter includes a FEC coding unit 100, an inverse discrete fourier transform unit 200, a guard interval insert unit 300, a mode information setting unit 400, The additional information inserting unit 500, the shaping filter 600, and the RF amplifier 700 are provided.

The FEC coding unit 100 performs coding for correcting an error occurring in the transmission for each service information of the OMD signal to be transmitted.

The IDFT unit 200 performs an Inverse Discrete Fourier Transform that rearranges the OFM signal formed based on the frequency coded by the FEC coding unit 100 based on time.

The GI inserting unit 300 inserts a guard interval for suppressing interference between neighboring OSDM symbols with respect to the OSDM signal in which the inverse discrete Fourier transform is performed in the IDFT unit 200.

The mode information setting unit 400 is provided for the OS signal transmitting PN (Pseudo Noise Sequence) information to be inserted into the OS signal to which the protection interval is inserted for synchronization of the OS signal. The level value PN 'is variably set according to the service mode SM. The pseudo noise string (PN) information is synchronization information for predicting synchronization and channel of the OMD signal received by the OMD receiver receiving the OMD signal transmitted.

In the present embodiment, the pseudo-noise sequence information, which is the synchronization information, is received based on a level value that is variably set in the pseudo-noise sequence information in the OMD receiver by varying the level value according to the service mode provided, rather than a constant level value. The service mode of the received OMD signal can be grasped.

The additional information inserting unit 500 has a level value that is variably set in response to the service mode of the OPM signal in the mode information setting unit 400 in the OPM signal in which the protection interval is inserted in the GI insertion unit 300. PN 'is inserted.

The shaping filter 600 shaping and filtering the OFM signal in which the pseudo noise string information of the level value set in the mode information setting unit 400 is inserted into the OFM signal in which the protection interval is inserted in the additional information insertion unit 500. do.

The RF amplifying unit 700 amplifies the OPM signal shaping filtered by the shaping filter 600. The amplified OMD signal thus amplified is transmitted through the antenna 800.

Therefore, the level value of the pseudo noise string information is varied and set according to the provided OS mode of the FM signal, and the pseudo noise string information having the set level value is inserted into the OS signal having the protection interval inserted. As a result, the service mode of the received FM signal may be determined based on the pseudo-noise string information of the set level value inserted in the FM signal before restoring the OS signal received by the FM receiver. Accordingly, the OPM receiver can determine the service mode and receive the necessary service without restoring the OFM signal.

According to the present exemplary embodiment, the level value of the pseudo noise string information variably set by the mode information setting unit 400 according to the service mode is represented by a ratio of the power of the OMD signal to which the guard interval is inserted to the power of the pseudo noise string information. . That is, the mode information setting unit 400 adjusts the power level of the pseudo noise string information according to the service mode and provides it to the additional information inserting unit 500.

On the other hand, examples of the service mode of this embodiment include a digital TV broadcasting mode, a mobile communication mode, a mobile text service mode, and the like. Preferably, the mode information setting unit 400, when the type of the service mode of the OPM signal provided by the digital TV broadcast mode, mobile communication mode, and mobile text service mode, the level value of the pseudo noise string information is digital The smallest level value is set in the TV broadcasting mode, and the higher level value is set in order of the mobile communication mode and the mobile text service mode. According to the present embodiment, the mode information setting unit 400 sets the level value of the pseudo noise string information to 0 dB to 2 dB when the service mode is a digital TV broadcasting mode. In addition, the mode information setting unit 400 sets the level value of the pseudo noise string information to 2 dB to 4 dB when the service mode is a mobile communication mode. The mode information setting unit 400 sets the level value of the pseudo noise string information to 4 dB to 6 dB when the service mode is the moving text service mode.

Accordingly, by setting the power ratio of the OMD signal in which the power-to-protection interval of the pseudo-noise sequence information is inserted in accordance with the service mode, the pseudo-noise sequence information is inserted into the OPM signal into which the protection interval is inserted. In the FM receiver, it is possible to easily determine the service mode provided based on the level value of the pseudo noise string information. In addition, by varying the level of the pseudo noise sequence information according to the service mode, it is possible to reduce the power consumption required for inserting the pseudo noise sequence information.

3 is a diagram illustrating a frame structure of an OMD signal output from the additional information insertion unit 500 of FIG. 2. The frame of the OSDM signal includes pseudo noise string (PN ') information having a variable level set by the mode information setting unit 400, a guard period GI, and an OSDM symbol. The OMD symbol is information for substantially restoring the OMD receiver. The guard period (GI) is a period allocated for suppressing interference between the OMD symbols transmitted. The pseudo noise string (PN ') information output from the mode information setting unit 400 has a level value that varies according to the service mode of the OMD signal.

4 is a flowchart illustrating a preferred embodiment of a method of transmitting an OMD signal using an OMD transmitter according to the present invention.

First, the FEC coding unit 100 performs coding for correcting an error occurring in transmission on service information of each OMD signal to be transmitted (S110). The IDFT unit 200 performs an inverse discrete Fourier transform for rearranging the OMD signal of the coded frequency axis to the time axis for error correction (S120).

The GI insertion unit 300 inserts a guard interval (GI) for suppressing interference between neighboring OFM die symbols with respect to the OFM die signal on which the inverse discrete Fourier transform is performed (S130). The mode information setting unit 400 variably sets the level noise PN 'according to the service mode SM of the OSDM signal with pseudo noise sequence PN information to be inserted into the OSDM signal to which the protection interval is inserted. (S140).

The additional information insertion unit 500 inserts the level value PN 'of the pseudo noise string information that is variably set corresponding to the service mode of the OSDM signal to the OSDM signal in which the protection interval is inserted (S150).

The shaping filter 600 shaping-filters the OMD signal into which the pseudo-noise string information of the level value PN 'set in the OMD signal into which the protection interval is inserted is inserted (S160). The RF amplifying unit 700 amplifies the molded filtered OMD signal in high frequency (S170).

Accordingly, the level of the noise noise information is changed according to the service mode provided, rather than the constant level value, so that the FM receiver receives the received noise signal based on the level value variably set in the pseudo noise noise information. Know the service mode. Accordingly, the OPM receiver can determine the service mode and receive the necessary service without restoring the OFM signal.

FIG. 5 is a flowchart illustrating the setting step S140 of FIG. 4 in detail. The mode information setting unit 400 receives the provided service mode SM and analyzes the received service mode (S141). Accordingly, the mode information setting unit 400 determines whether the service mode is a digital TV (DTV) broadcasting mode (S142). If the service mode is determined to be a digital TV (DTV) broadcasting mode, the mode information setting unit 400 sets the level value PN 'of the output pseudo noise string information to 2 dB (S143).

If it is determined in step S142 that the service mode is not a digital TV (DTV) broadcasting mode, the mode information setting unit 400 determines whether the service mode is a mobile communication mode (S144). If the service mode is determined to be the mobile communication mode, the mode information setting unit 400 sets the level value PN 'of the output pseudo noise string information to 4 dB (S145).

If it is determined in step S144 that the service mode is not the mobile communication mode, the mode information setting unit 400 determines whether the service mode is the mobile character service mode (S146). If it is determined that the service mode is the mobile character service mode, the mode information setting unit 400 sets the level value PN 'of the output pseudo noise string information to 6 dB (S147).

Therefore, by setting the level value of the pseudo noise sequence information variably according to the service mode provided, power consumption required for the insertion of the pseudo noise sequence information can be reduced.

According to the present invention, the level value of pseudonoise string information is varied and set according to the service mode of the OMD signal provided, and the pseudonoise string information having the set level value is inserted into the OPM signal with the protection interval inserted. As a result, the service mode of the received FM signal may be determined based on the pseudo-noise string information of the set level value inserted in the FM signal before restoring the OS signal received by the FM receiver.

Accordingly, the OPM receiver can determine the service mode and receive the necessary service without restoring the OFM signal. In addition, by setting the level value of the pseudo noise sequence information variably according to the service mode provided, power consumption required for inserting the pseudo noise sequence information can be reduced.

In the above described and illustrated with respect to the preferred embodiment of the present invention, the present invention is not limited to the specific preferred embodiment described above, without departing from the gist of the invention claimed in the claims in the art Various modifications can be made by those skilled in the art, and such changes are within the scope of the claims.

Claims (14)

In the OMD transmitter which performs time-domain synchronous transmission by inserting pseudo noise string information, which is the synchronization information of the OFM signal, into the OFM signal, A GI insertion unit for inserting a guard interval into the OFM signal to suppress interference between the symbols of the OFM signal; A mode information setting unit configured to variably set a level value of the pseudo noise string information according to the service mode of the OMD signal; And And a mode information inserting unit inserting the pseudo-noise string information having a level value set corresponding to the service mode to the OPM signal into which the protection interval is inserted. The method of claim 1, The service mode, the digital TV broadcasting mode, the mobile communication mode, and the mobile SMS service mode including at least one of the FM transmitter. The method of claim 1, The level value of the pseudo-noise string information set in the mode information setting unit is a power ratio of the power of the OPM signal to which the protection interval is inserted into the service mode and the power of the pseudo-noise string information. FM transmitter. The method of claim 3, The mode information setting unit, And if the service mode is the digital TV broadcasting mode, the range of the level value of the pseudo-noise sequence information is set to 0 dB to 2 dB. The method of claim 4, wherein The mode information setting unit, And if the service mode is the mobile communication mode, setting the range of the level value of the pseudo-noise string information to 2 dB to 4 dB. The method of claim 5, The mode information setting unit, If the service mode is the mobile text service mode, the range of the level value of the pseudo-noise string information is set to 4 dB to 6 dB. The method of claim 6, And a shaping filter for shaping and filtering the OFM signal having the set level and the pseudo-noise string information and the protection interval inserted therein. The method of claim 7, wherein And a high frequency amplifying unit configured to amplify the high frequency to transmit the molded filtered OMD signal through a channel. In the OMD transmission method using an OMD transmitter which performs time-domain synchronous transmission by inserting pseudo-noise string information, which is synchronization information of an OFM signal, into an OFM signal, Inserting a guard interval into the OFM signal to suppress inter-symbol interference of the OFM signal; Variably setting a level value of the pseudo-noise string information according to a service mode of the OS signal; Inserting the pseudo-noise sequence information having a level value set corresponding to the service mode into the OPM signal into which the protection interval is inserted; Shaping and filtering the OFM signal into which the pseudonoise string information having the set level value and the protection interval are inserted; And And amplifying the molded-filtered OFM signal by high frequency amplification. The method of claim 9, The service mode, the digital TV broadcasting mode, the mobile communication mode, and the mobile SMS service mode, characterized in that the OMD transmission method using an OMD transmitter. The method of claim 10, The level value of the pseudo-noise sequence information set in the setting step is a power ratio of the power of the OFM signal to which the protection interval is inserted and the pseudo-noise sequence information. FM transmission method. The method of claim 11, In the setting step, If the service mode is the digital TV broadcasting mode, the range of the level value of the pseudo-noise sequence information is set to 0 dB to 2 dB. The method of claim 12, In the setting step, And if the service mode is the mobile communication mode, setting the range of the level value of the pseudo-noise sequence information to 2 dB to 4 dB. The method of claim 13, The setting step, If the service mode is the mobile text service mode, the range of the level value of the pseudo-noise string information is set to 4 dB to 6 dB.