KR100864709B1 - OFDM Transmitter capable of improving the quality of receiving and a method processing OFDM signal thereof - Google Patents

Abstract

The OMD transmitter transmits an IDFT unit for performing inverse discrete Fourier transform that rearranges the OFM signal formed based on the frequency based on time, and an OFT neighboring to the OFM signal subjected to the inverse discrete Fourier transform. The GI insertion unit inserts a guard interval to suppress interference between the DM signals, and the OS is inserted into the OS signal with the guard interval inserted therein. And a synchronization inserting portion inserted into the DM signal. The synchronization information is channel information data for the PN sequence and the guard interval mode and the symbol mapping mode. Accordingly, in the apparatus for transmitting a signal by inserting a PN sequence in a digital sending system, the receiver may extract information necessary for a channel easily by adding information necessary for reception to the PN sequence, thereby improving reception performance.

Channel Information, Protection Section, Symbol Mapping, PN Sequence, Frame Sync, Receive Performance Enhancement

Description

FM transmitter capable of improving the quality of receiving and a method processing OFDM signal

1 is a diagram illustrating a data format of a general OSDM signal.

2A is a block diagram for generating a general PN sequence;

2b is a block diagram of a 16th Walsh code;

3 is a schematic block diagram of an UFDM transmitter according to the present invention;

4 is a block diagram of an embodiment of the synchronization inserting unit 600 of FIG.

5 is a block diagram of another embodiment of the synchronization inserting unit 600 of FIG.

6A is a block diagram of an eighth Walsh code;

6B and 6C show arbitrary data for the guard interval mode and the symbol mapping mode, and

FIG. 7 is a flowchart of a method of signal processing by the ODP transmitter of FIG. 3.

Explanation of symbols on the main parts of the drawings

100: FEC 200: serial / parallel converter

300: IDFT 400: parallel / serial conversion unit                 

500: GI insertion unit 600: synchronous insertion unit

700: filter portion 800: RF portion

The present invention relates to an Orthogonal Frequency Division Multiplexing (OFDM) transmitter, and more particularly, to an OFM transmitter capable of improving reception performance.

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 for 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 division 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.

The synchronization insertion unit for inserting the synchronization information inserts a timing synchronization signal and a frame sync for channel prediction in front of the guard period GI. As a result, as shown in FIG. A frame consists of a frame sync and a frame segment, that is, a frame segment consisting of a guard interval and a predetermined number of sample data. As illustrated in FIG. 1, 255 signal frames are gathered to form one frame group. Frame sync is binary data plus a PN sequence and a walsh code. Here, the frame sync is a binary data value obtained by adding a PN sequence, which is 255 binary data values output by the block diagram shown in FIG. 2A, and a 16 th order Walsh code shown in FIG. 2B. That is, 16 data of the PN sequence are added to one bit of the Walsh code. Here, the Walsh code is used to distinguish from which of the base stations data is transmitted.

Typically, since a base station affects within one reception area is limited, it is difficult for more than 8 to influence the base station. Therefore, by using the 16th Walsh code conventionally used as the 8th Walsh code, it is effective for more accurate reception to carry the necessary information when receiving the channel corresponding to the remaining 8th Walsh code.

SUMMARY OF THE INVENTION An object of the present invention for solving the above problems is to provide an OMD transmitter which carries useful information to the frame sink to improve reception performance.

In order to achieve the above object, the OMD transmitter according to the present invention includes an IDFT unit for performing an inverse discrete Fourier transform for rearranging an OFM signal formed based on frequency based on time, and an inverse discrete Fourier transform. A GI insertion unit inserting a guard interval to suppress interference between the OMD signals adjacent to the OMD signal, and the synchronization and channel of the OMD signal to the OMD signal inserted with the guard interval. It has a synchronization insertion unit for inserting synchronization information for prediction into the OMD signal inserted with the protection interval, the synchronization information is characterized by having a PN sequence and channel information.

Preferably, the PN sequence is data combined with a Walsh code, which is base station information, and the channel information is at least one of a guard interval mode and a symbol mapping mode.

On the other hand, the signal processing method according to the present invention, the step of inverse Fourier transform to rearrange the FM signal formed on the basis of the frequency based on time; Inserting a guard interval to suppress interference between the OFM signals adjacent to the OFTDM signals inversely Fourier transformed; And inserting synchronization information into the OPM signal with the guard interval inserted into the ODM signal with the guard interval inserted into the ODM signal with the guard interval inserted, wherein the synchronization information includes a PN sequence and channel information. It is characterized by that.

Accordingly, in the apparatus for transmitting a signal by inserting a PN sequence in a digital sending system, the receiver may extract information necessary for a channel easily by adding information necessary for reception to the PN sequence, thereby improving reception performance.

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

Figure 3 is a block diagram showing a preferred embodiment of the FM transmitter in accordance with the present invention. The FM transmitter includes a FEC (forward error corrector) 100, a serial / parallel conversion unit 200, an inverse discrete fourier transform (IDFT) 300, a parallel / serial conversion unit 400, and a guard interavl (GI) insertion. The unit 500, the synchronization inserting unit 600, the filter unit 700, the RF unit 800 and the like.

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

The serial / parallel conversion unit 200 converts the error coded serial data into predetermined parallel data and outputs the converted parallel data.

The IDFT unit 300 performs an Inverse Discrete Fourier Transform that rearranges N data of the frequency domain into N sample data of the time domain. The sample data in the inverse Fourier transform time domain is converted into serial data by the parallel / serial converter 400 and output.

The guard interval inserting unit 500 inserts a guard interval GI in units of N sample data with respect to the output serial data. For example, the guard period GI is provided to suppress interference between neighboring frame segments with respect to a signal frame including 255 frame segments as shown in FIG. 1.

The synchronization inserting unit 600 inserts synchronization information for synchronization and channel prediction in the OSDM receiver into the OS signal in which the protection interval GI is inserted in the GI insertion unit 500. Here, the synchronization information is information of a binary data value to which a PN sequence, Walsh code, and channel information are added.

Thereafter, the filter unit 700 filters the OFM signal, and the filtered OMD signal is processed by the RF unit 800 as an RF signal and transmitted to the channel.

Hereinafter, the preferred embodiment of the present invention will be described in detail with reference to FIGS. 4 to 5 by inserting necessary information through the synchronization inserting unit 600 to improve reception performance.

FIG. 4 is a block diagram of generating an synchronization signal by adding data including a combination of an eighth order Walsh code and information data required for a channel to a PN sequence. As shown in FIG. 1, a frame sink is inserted into a frame segment in which a guard interval GI is inserted into data inversely Fourier transformed by the IDFT 300. This frame sync combines the PN sequence 611, the eighth order Walsh code 613 as shown in FIG. 6A, and the information 615 necessary for the channel through the MUX 617, and then, by the XOR gate 619. FIG. Synchronization information is generated. In this case, the channel information data is generally at least one of a guard interval mode and a symbol mapping mode used for synchronization and channel prediction.

Meanwhile, FIG. 5 is another embodiment of the present invention. In general, since the information transmitted from the base station can be detected by the receiver, only the channel information 625 except for the eighth order Walsh code is included in the PN sequence 621 and the XOR gate 629. ) To generate synchronization information. Of course, the channel information data is data in which the protection period mode, the symbol mapping mode, or the protection period mode and the symbol mapping mode are combined. For example, FIGS. 6B and 6C show the protection interval (GI) mode (1/6, 1/9, 1/12, 1/20, 1/30) and the symbol mapping mode (QPSK, 16QAM, 64QAM) according to constellation. This shows an arbitrary code for. In FIG. 6C, two bits of '8' are added to distinguish the protection interval mode (FIG. 6B) and the symbol mapping mode among the 8 bits of data. In FIG. The code of minimizing the correlation is selected, and in FIG. 6C, the 6-bit data is also selected from the code with the minimum correlation between them.

Therefore, by adding channel information necessary for the PN sequence, the receiver can easily extract information necessary for a channel, thereby improving reception performance.

7 illustrates in detail a method of signal processing by inserting channel information data into a PN sequence in an OEM transmitter according to the present invention.

The serial data error coded by the FEC 100 is output as parallel data to the serial / parallel conversion unit 200 (S10).

The parallel-converted data is inversely Fourier transformed into sample data in the time domain by the IDFT 300 (S20). Thereafter, the sample data in the inverse Fourier transformed time domain is converted into serial data by the parallel / serial converter 400 and outputted (S30).

Guard interval (GI) insertion unit 500 inserts a guard interval (GI) in units of frame segments with respect to the output serial data (S40). The synchronization inserting unit 600 inserts synchronization information for synchronization and channel prediction at the OSDM receiver into the OS signal of which the protection interval GI is inserted in the GI insertion unit 500 (S50).

Here, the synchronization information may be data added with a combination of the PN sequence 611, the eighth order Walsh code 613, and the channel information data 615, as shown in FIG. 4, or as shown in FIG. Likewise, the data may be a combination of only the PN sequence 621 and the channel information data 623. In this case, the channel information data is, for example, a protection interval (GI) mode for synchronization and channel prediction required for receiving an OMD signal and a symbol mapping mode according to the constellation.                     

Thereafter, the OPM signal is filtered by the filter unit 700 and transmitted to the wireless channel through the RF unit 800 (S60).

In this manner, by using the guard interval mode and the symbol mapping mode in combination with the PN sequence as the frame sync, that is, the synchronization information, the reception performance of the receiver can be improved.

In addition, the receiver may easily and reliably detect necessary mode information by using the correlation between the received signal and the M sequence using characteristics of the M sequence.

According to the present invention, in a device for transmitting a signal by inserting a PN sequence in a digital sending system, the receiver may extract information necessary for a channel by adding information necessary for reception to the PN sequence, thereby improving reception performance.

In addition, the receiver may easily and reliably detect necessary mode information by using the correlation of the received signal and the M sequence by using the characteristics of the M sequence.

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)

An IDFT unit for performing an inverse discrete Fourier transform for rearranging the OFM signal formed based on frequency based on time; A GI insertion unit for inserting a guard interval to suppress interference between the OFM signals adjacent to the OFM signals subjected to the inverse discrete Fourier transform; And And a synchronization insertion unit for inserting synchronization information for synchronizing the channel of the OSF signal and channel prediction into the OSF signal to which the protection period is inserted, and inserting the synchronization information to the OSF signal with the protection period inserted. And the synchronization information has a PN sequence and channel information. The method of claim 1, The synchronization information further comprises a Walsh code (walsh code) that is the base station information. The method of claim 1, The channel information, The OMD transmitter is at least one of a guard interval mode and a symbol mapping mode. The method of claim 3, wherein The type of the guard interval mode is one of 1/6, 1/9, 1/12, 1/20, 1/30 of the OMD transmitter. The method of claim 3, wherein The symbol mapping mode is one of the QPSK, 16QAM, 64QAM of the FM transmitter. An inverse Fourier transform so as to rearrange the OFM signal formed based on the frequency based on time; Inserting a guard interval to suppress interference between the OFM signals neighboring the OFM signals converted by the inverse Fourier transform; And And inserting synchronization information for synchronization and channel prediction of the OFM signal into the OFM signal into which the protection interval is inserted. And the synchronization information has a PN sequence and channel information. The method of claim 6, The synchronization information has a Walsh code (walsh code) that is the base station information signal processing method characterized in that the further. The method of claim 6, The channel information, And at least one of a guard interval mode and a symbol mapping mode. The method of claim 8, The guard interval mode is a signal processing method of the OMD transmitter, characterized in that any one of 1/6, 1/9, 1/12, 1/20, 1/30.  The method of claim 8, The symbol mapping mode is any one of QPSK, 16QAM, 64QAM signal processing method of the FM transmitter.

Images