KR20030095709A - OFDM Transmitting System capable of transmitting the OFDM signal of multi-service mode according to predetermined a channel - Google Patents

Abstract

PURPOSE: An OFDM transmission system capable of transmitting OFDM signals of a multiple service mode through allotted channels is provided to increase the use efficiency of allotted frequency bandwidth by transmitting source data corresponding to a plurality of service modes. CONSTITUTION: A plurality of forward error connection(FEC) units(100) execute coding for correcting errors generated in transmitting a plurality of source data according to service modes. A plurality of mapping units(200) map the error-coded source data by symbol units. A frame forming unit(300) combines the mapped source data for forming one orthogonal frequency division multiplexing(OFDM) frame. An inverse fast fourier transform(IFFT) unit(500) executes IFFT by allotting multiple subcarriers to the OFDM frame by source data. A guard interval(GI) insertion unit(600) inserts a guard interval into the OFDM frame to prevent interferences between OFDM frames.

Description

OFDM Transmitting System capable of transmitting the OFDM signal of multi-service mode according to predetermined a channel}

The present invention relates to an Orthogonal Frequency Division Multiplexing (OFDM) transmission system, and more particularly, modulates a signal for transmission through OFM modulation and inserts a modulated OFM signal into a multiple subcarrier. The present invention relates to an OMD transmission system for transmitting.

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.

In Europe, Orthogonal Frequency Division Multiplexing (OFDM), a digital modulation method that achieves the dual effect of improving transmission speed per bandwidth and preventing interference, is adopted as the next generation high-definition television terrestrial broadcasting method.

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 accomplished by the Fast Fourier Transform (FFT) and the Inverse Fast Fourier Transform (IFFT), which are simply determined 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.

1 is a block diagram schematically illustrating an example of a general OSDM transmission system.

The FM transmission system includes a forward error correction (FEC) unit 10, an inverse fast fourier transform (IFFT) unit 20, a guard interval (GI) insertion unit 30, and a radio frequency (RF) amplification unit (FEC). 40).

The FEC unit 10 performs coding for correction of an error occurring in transmission on the source data of the determined service mode for transmission. The IFFT unit 20 inverse Fourier transforms the source data on which the coding is performed for error correction. The GI insertion unit 30 inserts a guard interval for suppressing interference between the source data in the source data on which the inverse Fourier transform is performed. The RF amplifier 40 amplifies the source data into which the guard interval is inserted. The amplified source data is transmitted to the receiver through the transmission channel through the antenna 50.

2 is a diagram illustrating an example of a frame structure of data transmitted through a conventional OPM transmission system. The figure shows an example of the service mode as MPEG data.

The frame structure of MPEG data transmitted through the conventional OMD transmission system is inversely Fourier transformed by the number N of multiple subcarriers determined for inverse Fourier transform in the IFFT unit 20. At this time, the frame of MPEG data is filled with the same number as the number of the determined number N of multiple subcarriers.

The conventional OMD transmission system transmits only one service regardless of a transmission rate required according to a service mode by transmitting source data, which is one determined service mode, through a determined number of multiple subcarriers. Accordingly, the conventional OMD transmission system transmits by inverse Fourier transforming the source data of one service mode regardless of the determined number of multiple subcarriers. Therefore, the conventional OMD transmission system has a problem in that it is not possible to efficiently use the number of multiple subcarriers determined by transmitting the source data corresponding to one service mode regardless of the service mode of the source data to be transmitted.

In addition, the conventional OMD transmission system transmits the source data of the corresponding service mode to the frequency band determined for one service mode, so that when the source data of the corresponding service mode is not transmitted, the utilization efficiency for the determined frequency band is reduced. There is a low problem.

An object of the present invention for solving the above problems is to provide an OFM transmission system that can more efficiently use the frequency band determined according to the service mode.

Another object of the present invention for solving the above problems is to provide an OMD transmission system capable of transmitting OMD signals corresponding to more various service modes through the determined frequency band.

1 is a block diagram schematically illustrating an example of a general OSDM transmission system;

2 is a diagram illustrating an example of a frame structure of data transmitted through a conventional OPM transmission system;

3 is a block diagram showing a preferred embodiment of the OS transmission system according to the present invention;

4 is a diagram illustrating an example of an OMD frame formed by FIG. 3;

FIG. 5 is a diagram illustrating a plurality of OPM frames output from the frame forming unit of FIG. 3 with reference to a time axis; and

6 is a flowchart illustrating a preferred embodiment of the OS transmission method using the OS transmission system according to the present invention.

Explanation of symbols on the main parts of the drawings

100: FEC part 120: 1st FEC part

140: second FEC part 160: third FEC part

200: mapping unit 220: first mapping unit

240: second mapping unit 260: third mapping unit

300: frame forming portion 400: GB portion

500: IFFT part 600: GI insertion part

700: RF amplifier

The object as described above, according to the present invention, in the OMD transmission system for transmitting a signal through the OMD modulation, a plurality of source data according to the service mode to perform the coding for the correction of errors occurring on each transmission A plurality of FEC units to perform mapping, a plurality of mapping units to perform mapping of each source data subjected to error coding on a symbol basis, and a frame forming unit to combine the source data on which the mapping is performed into one OMD frame, An IFFT unit for performing inverse fast Fourier transform by allocating multiple subcarriers for each ODP frame by source data, and inserting a protection interval for suppressing interference between the OFM die frames in the OPM frame with inverse fast Fourier transform. RF to amplify the RF signal consisting of the GI insertion portion, and the OPM DM frame inserted with a protection interval It is accomplished by the OFDM transmission system including the pokbu.

Preferably, the frame forming unit groups the OMD frames in which the plurality of source data are combined to a predetermined number, inserts a header into the group of ODM frames to be grouped, and inserts the headers into the ODM frames within the group. Insert information about the included source data into the header.

Examples of the source data include MPEG data, audio data, data broadcasting data, and the like.

Examples of the multiple subcarriers include 2K having a number of points of inverse fast Fourier transform, 2K having 2048, 4K having 4096, and 8K having 8192.

According to the present invention, in the OMD transmission method using an OMD transmission system for transmitting a signal through the OMD modulation, an error occurring in the transmission of a plurality of source data according to the service mode, respectively Performing coding for correction of the data, combining each source data subjected to each error coding to form one OSDM frame, and assigning multiple subcarriers to the OSDM frame for each source data. Performing a fast Fourier transform, inserting a guard interval for suppressing interference between the OSDM frames in the OSDM frame on which the inverse fast Fourier transform is performed, and an OSMD frame having the guard interval inserted therein UFD using the UFDM transmission system including the step of amplifying the FDM signal It is achieved by a transmission method.

Preferably, in the frame forming step, a header is inserted into a group of the OMD frame grouped by grouping the ODM frames in which a plurality of source data are combined into a predetermined number, and the plurality of ODM frames in the group. Information about the source data included in the frame is inserted in the header.

Examples of the source data include MPEG data, audio data, data broadcasting data, and the like. The types of multiple subcarriers include 2K having a number of points of the multiple subcarriers for inverse fast Fourier transform, 4K having 4096, and 8K having 8192.

According to the present invention, by transmitting source data corresponding to a plurality of service modes with respect to the allocated frequency bandwidth, the use efficiency of the allocated frequency bandwidth can be increased and various services can be provided through the corresponding band.

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

3 is a block diagram showing a preferred embodiment of the OS transmission system according to the present invention.

The OPM transmission system includes a forward error correction (FEC) unit 100, a mapping unit 200, a frame forming unit 300, a guard band (GB) unit 400, and an inverse fast fourier transform (IFFT). ) 500, a GI (Guard Interval) insertion unit 600, and a RF (Radio Frequency) amplifier 700.

The FEC unit 100 performs coding for correcting errors occurring on the transmission of a plurality of source data corresponding to respective service modes, respectively. In the present embodiment, MPEG data, audio data, and data broadcasting data are taken as examples of service modes. Accordingly, the FEC unit 100 according to the present embodiment includes the first FEC unit 120, the second FEC unit 140, and the third FEC unit which perform error correction coding on MPEG data, audio data, and data broadcasting data, which are service modes, respectively. Has 160.

The mapping unit 200 maps the source data on which the error correction coding is performed in symbol units according to the service mode. The mapping unit 200 according to the present exemplary embodiment may include a first mapping unit 220, a second mapping unit 240, corresponding to the first FEC unit 120, the second FEC unit 140, and the third FEC unit 160. And a third mapping unit 260.

The frame forming unit 300 combines the source data on which symbol units are mapped for each source data to form a single OMD frame. In this case, the formed OMD frame is formed in a size corresponding to the number of preset multiple subcarriers. An example of the number of multiple subcarriers is 2048, 4096, and 8192 subcarriers. Preferably, the number of points of subcarriers in this embodiment is 2K, 4K, and 8K corresponding to 2048, 4096, and 8192.

The GB unit 400 inserts guard bands on both sides of the one OMD frame formed in the frame forming unit 300. The IFFT unit 500 performs inverse fast Fourier transform on the OMD signal formed of the OMD frame with the guard band inserted therein.

The GI inserting unit 600 inserts a guard interval for suppressing interference between respective OMD frames of the OMD signal in which the inverse fast Fourier transform is performed.

The RF amplifier 700 amplifies the OFM signal in which the protection interval is inserted. The high frequency amplified OFM signal is transmitted along the transmission channel through the antenna 800.

Therefore, the OMD signal according to the plurality of service modes can be transmitted through the set bandwidth. In addition, the receiving side may select and restore a desired service as a plurality of services are received in one OMD frame. And, by transmitting a plurality of services for the allocated frequency bandwidth, it is possible to increase the utilization efficiency of the allocated frequency bandwidth.

The frame forming unit 300 according to the present exemplary embodiment forms source data corresponding to a plurality of input service modes as an OMD frame, and then groups a plurality of ODM frames formed to each OMD frame group. It is preferable to insert the head. In this case, the head includes respective information on source data which is a plurality of service modes included in the grouped OMD frames.

FIG. 4 is a diagram illustrating an example of an OMD frame formed by FIG. 3. According to the OMD frame, the type of source data according to the service mode is an example of MPEG data, audio data, and data broadcasting data. The frame forming unit 300 of the present embodiment sets MPEG allocation data, audio data, and data broadcasting data according to a transmission rate required for each service mode, and inserts corresponding source data into the allocation area. According to the figure, the region occupied by MPEG data is the largest among one OMD frame, and occupies the allocation region in order of data broadcasting data and audio data.

In addition, as shown, the OMD frame has a form in which the guard band is inserted into both sides of the frame through the GB unit 400. The OMD frame is formed of N multiple subcarriers having points of 0 to 'N-1' multiple subcarriers. In this case, N is 2K, 4K, and 8K. Therefore, the guard band is included in the number of corresponding multiple subcarriers of the allocated frequency band.

FIG. 5 is a diagram illustrating a plurality of ODP frames output from the frame forming unit 300 of FIG. 3 with reference to a time axis. As shown, the number of OMD frames grouped in the frame forming unit 300 is m. Accordingly, the header H is inserted in units of m OPM frames grouped, and the source data (data broadcast 1, audio () of each OFM frame corresponding to each service mode is inserted in the header H. 1), MPEG (1), data broadcasting (2), audio (2), MPEG (2), ... information on data broadcasting (m), audio (m), MPEG (m)) is included. .

Accordingly, the OMD receiver receiving the OMD signal in which the header H including the information about the source data of the OMD frame is inserted, analyzes the header H before restoring the received OMD signal. Only the desired source data can be extracted and restored.

6 is a flowchart illustrating a preferred embodiment of the OS transmission method using the OS transmission system according to the present invention.

First, the FEC unit 100 having the first FEC unit 120, the second FEC unit 140, and the third FEC unit 160 is MPEG data, audio data, and data, which are source data corresponding to respective service modes. Coding is performed on the broadcast data to correct errors occurring on the transmission, respectively (S100).

The first mapping unit 220, the second mapping unit 240, and the third mapping unit 260 provided corresponding to the first FEC unit 120, the second FEC unit 140, and the third FEC unit 160 are disposed. The mapping unit 200 maps the source data on which the error correction coding is performed in symbol units according to the service mode (S120).

The frame forming unit 300 combines source data in which symbol units are mapped for each source data, and has one of 2K, 4K, and 8K corresponding to 2048, 4096, and 8192 according to the number of points of subcarriers. It is formed of an OMD frame (S140). The GB unit 400 inserts guard bands on both sides of the one OMD frame formed in the frame forming unit 300 (S160). The IFFT unit 500 performs an inverse fast Fourier transform on the OMD signal formed of the OMD frame into which the guard band is inserted (S180).

The GI insertion unit 600 inserts a guard interval for suppressing the interference between the respective OMD frames of the ODM signal in which the inverse fast Fourier transform is performed (S200). The RF amplifier 700 amplifies a high frequency of the FM signal inserted into the protection interval (S220). Accordingly, source data corresponding to a plurality of service modes may be transmitted with respect to the allocated frequency bandwidth.

According to the present invention, by transmitting source data corresponding to a plurality of service modes with respect to the allocated frequency bandwidth, the use efficiency of the allocated frequency bandwidth can be increased and various services can be provided through the corresponding band.

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 (10)

In the OMD transmission system for transmitting a signal through the OMD modulation, A plurality of FEC units for coding a plurality of source data according to a service mode for correcting an error occurring on a transmission; A plurality of mapping units which map each source data on which the error coding is performed in symbol units; A frame forming unit which combines the source data on which the mapping is performed and forms one OMD frame; An IFFT unit for performing inverse fast Fourier transform by allocating multiple subcarriers for each of the source data to the OMD frame; And And a GI insertion unit for inserting a guard interval for suppressing interference between the UF DM frames in the UF DM frame on which the inverse fast Fourier transform has been performed. The method of claim 1, The frame forming unit may group the OMD frames in which the plurality of source data are combined into a predetermined number to insert a header into the grouped OMD frame groups to insert a header into the group of ODM frames in the group. And inserting information on the source data included in the header. The method of claim 2, And the source data comprises at least one of MPEG data, audio data, and data broadcasting data. The method of claim 3, The multiple subcarriers, And the number of points of the multiple subcarriers for the inverse fast Fourier transform corresponds to any one of 2K of 2048, 4K of 4096, and 8K of 8192. The method of claim 4, wherein And an RF amplifier configured to amplify an RF signal, which is an OMD frame with the protection period inserted therein, into an RF amplifier. In the OMD transmission method using an OMD transmission system for transmitting a signal through the OMD modulation, Performing coding for correcting an error occurring on the transmission of the plurality of source data according to the service mode, respectively; Combining each source data on which each error coding is performed to form one OMD frame; Performing an inverse fast Fourier transform by allocating multiple subcarriers for each of the source data with respect to the OFM frame; And And inserting a protection interval for suppressing the interference between the OSF frames in the OSF frame on which the inverse fast Fourier transform has been performed. . The method of claim 6, In the frame forming step, The OMD frames in which the plurality of source data are combined are grouped in a predetermined number so that a header is inserted into the grouped OMD frame groups, and the source data included in the OMD frames in the group. The information transmission method of the OPM using the OMD DM service system, characterized in that is inserted into the header. The method of claim 7, wherein And the source data comprises at least one of MPEG data, audio data, and data broadcasting data. The method of claim 8, The multiple subcarriers, The number of points of the multiple subcarriers for the inverse fast Fourier transform corresponds to any one of 2K of 2048, 4K of 4096 persons, and 8K of 8192 persons. Way. The method of claim 9, And amplifying high-frequency amplification of the FM signal comprising the OMD frame inserted with the protection period. 2.