KR100637068B1 - An OFDM Transmitter capable of improving the employment rate of predetermined frequency band for transmitting to OFDM signal - Google Patents

Abstract

An OMD transmitter capable of increasing transmission utilization of an allocated frequency band is disclosed. The OMD transmitter comprises: an IDFT unit for performing an inverse discrete Fourier transform that rearranges an OFM signal formed based on a frequency based on time, and suppresses interference between the OFM signals which have undergone an inverse discrete Fourier transform. GI insertion section for inserting the guard interval, the synchronization insertion section for inserting synchronization information for synchronization and channel prediction at the receiving end into the OFM signal with the guard interval inserted, and each of the OPM signals with the synchronization information inserted According to the type of service information, the service information has a multi-switching unit for sequentially switching the transmission rate over time differently through a predetermined band. By inserting the type information of each service into the synchronization information to the plurality of services that the synchronization insertion unit is to transmit the OMD signal for one frequency band, and outputs multiple switching based on the transmission rate required according to the type of service through the multiple switching unit, Various services can be provided through one allocated band.

Time Division Synchronization, UF DM, PN, Service Information, Type Information

Description

An OFDM Transmitter capable of improving the employment rate of predetermined frequency band for transmitting to OFDM signal

1A and 1B are diagrams illustrating a transmission scheme according to a service type of a general OSDM signal;

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

3 illustrates a frame structure of an OFM signal using time division synchronization, and

4 is a view showing in detail the multi-switching portion of the two.

Explanation of symbols on the main parts of the drawings

100: FEC coding unit 200: IDFT unit

300: GI insertion unit 400: synchronous insertion unit

500: multiple switching unit 600: molding filter

700: RF amplifier

The present invention relates to an Orthogonal Frequency Division Multiplexing (OFDM) transmitter. More particularly, the present invention relates to an OMD transmitter that transmits an OFM signal using time division according to a service type of the OFM signal. It is about.

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 caused 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.

1A and 1B are diagrams illustrating a transmission scheme according to a service type of a general OSDM signal.

In the drawing, the service 1 10 and the service 1 20, which are OS signals, are different information. In the conventional OMD transmitter, only one service is allocated to one transmission frequency band and transmitted. Accordingly, the FM transmitter transmits the service 1 (10) on a frame basis, that is, on the basis of the time axis t, the service 1-1, the service 1-2, ... And service 1-N sequentially. Also, for the service 2 (20), the OMD transmitter transmits the service 2-1, the service 2-2, ..., the service 2- on a frame-by-frame basis as in the service 1 (10). (N-1), and service 2-N are sequentially transmitted.

However, the conventional OMD transmission which transmits only one service for the allocated frequency band cannot transmit various services such as audio, video, and A / V information using the allocated frequency band. In addition, the conventional OMD transmitter provides a service through one transmission band without considering various situations occurring at the receiving side.

Therefore, when the receiving environment of the service user is to receive the OMD signal transmitted by the conventional method in the environment of the fixed reception or the mobile body, and receives the service, the receiving environment of the transmitted OS signal is not considered. Since the received OMD signal is received, it is difficult to receive in a poor reception environment.

Accordingly, service users who are provided with the service through the OMD signal transmitted by the conventional method have difficulty in using various services. In addition, the conventional OMD transmitter transmits data sequentially over a set frequency band irrespective of the importance of the data to be transmitted, thus making it difficult to stably receive the important data.

An object of the present invention for solving the above problems is to provide an OMD transmitter capable of transmitting various types of services using the assigned frequency band.

Another object of the present invention for solving the above problems is to provide an OMD transmitter capable of adaptively transmitting a service to a receiving environment of a receiving side.                         

Another object of the present invention for solving the above problems is to provide an OMD transmitter capable of transmitting a more stable data according to the importance of the data.

The object as described above, according to the present invention, the IDFT unit for performing an inverse discrete Fourier transform for rearranging the OFM signal formed on the basis of the frequency, between the OPM signals, the inverse discrete Fourier transform is performed GI insertion unit for inserting a guard interval to suppress interference, a synchronization inserter for inserting synchronization information for synchronization and channel prediction at the receiving end into an OFM signal with a guard interval inserted, and an OF with synchronization information inserted According to the type of each service information of the DM signal, the service information is achieved by the OMD transmitter including a multi-switching unit for sequentially switching the transmission rate differently over time through a predetermined band.

The synchronization information consists of PN information into which information on the type of service information is inserted. Types of service information include data information, audio information, video information, video information, and digital broadcasting information. In addition, the video information, video information, and digital broadcasting information include resolution information of the video and display size information of the video.

Preferably, the OMD transmitter of the present embodiment further includes an FEC coding unit which performs coding for correcting an error occurring in transmission on the service information of each OFM signal to be transmitted before the IDFT unit.

In addition, the OMD transmitter of the present embodiment, a molding filter for filtering the pulse corresponding to the service information that is sequentially switched over time in the multi-switching unit into a curved waveform, and the service information output from the molding filter It further comprises an RF amplifier for amplifying a high frequency.

According to the present invention, the type of service information is inserted into the synchronization information into a plurality of services that are the OPM signals transmitted by the synchronization inserter for one frequency band, and are based on the transmission rate required according to the type of service through the multiple switching unit. By multiple switching outputs, various services can be provided through one allocated band. In addition, by providing a plurality of services using the allocated frequency band, the use efficiency of the frequency band can be improved. In addition, it is possible to transmit the respective service information by varying the modulation scheme of each service according to the reception environment and the transmission frequency according to the transmission rate of each service. In addition, in a poor channel environment, by using a stable modulation scheme for the service information and transmitting, it is possible to easily demodulate the received service at a low signal-to-noise ratio at the receiver.

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

Figure 2 is a block diagram showing a preferred embodiment of the FM transmitter in accordance with the present invention. The OMD transmitter includes a forward error correction coding (FEC) coding unit 100, an inverse discrete fourier transform (IDFT) unit 200, a guard interval (GI) insertion unit 300, a synchronization insertion unit 400, and multiplexing. And a switching unit 500, a shaping filter 600, and an RF amplifier 700.

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 frequency based on time. The GI inserting unit 300 inserts a guard interval for suppressing interference between neighboring OSF signals with respect to the OSF signal in which the inverse discrete Fourier transform is performed in the IDFT unit 200. The synchronization inserting unit 400 inserts synchronization information informing the start of service according to the stream of the OSDM signal into the OS signal of which the guard interval is inserted in the GI insertion unit 300. This synchronization information is used for synchronization and channel prediction in the OMD receiver.

At this time, the synchronization inserting unit 400 generates a pulse corresponding to the OFM signal into which the synchronization information is inserted. The multi-switching unit 500 sequentially switches the transmission rate according to time differently through the preset band according to the type of each service information of the OS signal in which the synchronization information is inserted.

The shaping filter 600 filters the pulses corresponding to the service information output by being sequentially switched in time by the multi-switching unit 500 into a curved waveform. The RF amplifier 700 asynchronously amplifies the service information output by being sequentially switched in time by the multi-switching unit 500.

Meanwhile, the synchronization information inserted into the synchronization insertion unit 400 is called PN information, that is, pseudo noise sequence information. The synchronization inserting unit 400 according to the present embodiment includes each piece of information on a plurality of services of the OMD signal for transmission to the PN information, and inserts the information into the OMD signal with the guard interval inserted therein. In this case, examples of the type of service information include data information, audio information, video information, video information, and digital broadcasting information. The video information, video information, and digital broadcast information include video resolution information, video display size information, and the like.

Accordingly, the type of service is provided through the multi-switching unit 500 by inserting the type information of each type of service into a plurality of services that are OFM signals to be transmitted by the sync insertion unit 400 for one frequency band. According to the multiple switching output based on the transmission rate required according to, it is possible to provide a variety of services through one allocated band. As a result, the allocated frequency band can be efficiently used, and the utilization rate of the frequency band can be increased.

3 is a diagram illustrating a frame structure of an OMD signal using time division synchronization. Any service N of the OS signal includes synchronization information, a guard period (GI), and OS signal. The OSDM data is substantially information for reproduction at the receiving end. The guard period (GI) is a period allocated for suppressing interference between a plurality of OFM data transmitted sequentially. The synchronization information is information for notifying the start of each OPM data when the OMD data is streamed. In the present embodiment, the type information of the service for each ODP data is inserted into the synchronization information, and the synchronization information with the type information is inserted into the OMD data with the protection interval GI inserted therein. Accordingly, the receiving end can determine the type of the received OMD data based on the type information of the service included in the synchronization information. In addition, the receiving end can reproduce the OMD data suitable for the reception situation through the type information.                     

4 is a diagram illustrating in detail the multi-switching unit 500 of the two. The synchronization inserter 400 inserts corresponding PN information for the service 1 to the service N, respectively, and outputs the PN information to the multi-switching unit 500. The multi-switching unit 500 multiplexes the service 1 to the service N into which the PN information is inserted in response to the data rate required according to the type information. For example, if service 1 is information suitable for the stop environment of the receiver and service 2 is information suitable for the mobile environment of the receiver, the multi-switching unit 500 transmits the frequency of service 2 compared to service 1 based on the time axis. Multiply by raising it. In addition, when the service 1 is audio information and the service 2 is video information, the multi-switching unit 500 performs a multi-switching by increasing the transmission frequency of the service 2 compared to the service 1 based on the time axis.

Therefore, by inserting PN information including the type of service into the service information to be transmitted, and adjusting the transmission frequency of each service information according to the receiving environment and transmitting through one frequency band, the low signal-to-noise ratio of the service information to be transmitted Also, demodulation of the received service information can be easily performed.

According to the present invention, the type of service information is inserted into the synchronization information into a plurality of services that are the OPM signals transmitted by the synchronization inserter for one frequency band, and are based on the transmission rate required according to the type of service through the multiple switching unit. By multiple switching outputs, various services can be provided through one allocated band.

In addition, by providing a plurality of services using the allocated frequency band, the use efficiency of the frequency band can be improved.                     

Each service information can be transmitted by varying the modulation scheme of each service according to the reception environment and the transmission frequency according to the transmission rate of each service. In addition, in a poor channel environment, by using a stable modulation scheme for the service information and transmitting, it is possible to easily demodulate the received service at a low signal-to-noise ratio at the receiver.

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 (25)

delete delete delete delete delete delete delete An IDFT unit for performing an inverse discrete Fourier transform for rearranging the OFM signal formed based on frequency based on time; And a GI insertion unit for inserting a guard interval to suppress interference between the OSF signals in which the inverse discrete Fourier transform has been performed. In the transmitter, Further comprising a multiplexer for multiplexing the plurality of service information, The plurality of service information is OFM transmitter, characterized in that the data rate is sequentially multiplexed differently according to the type of each service information. delete The method of claim 8, The type of the service information is OFM die transmitter, characterized in that it comprises at least one of data information, audio information, video information, video information and digital broadcasting information. The method of claim 10, And the video information, the video information, and the digital broadcast information include at least one of resolution information of the video and display size information of the video. The method according to any one of claims 8, 10 and 11, And an FEC coding unit configured to perform coding for correcting an error occurring in transmission for each service information of the multiplexed plurality of service information of the OMD signal. The method of claim 12, And an RF amplifier for amplifying the multiplexed plurality of pieces of service information of the OMD signal. delete Performing an inverse discrete Fourier transform that rearranges the OFM signal formed based on the frequency based on time; And inserting a guard interval to suppress interference between the OSF signals in which the inverse discrete Fourier transform has been performed, the method of transmitting the OSFDM signal comprising a plurality of service information. And the plurality of service information are sequentially multiplexed at different transmission rates according to types of service information. delete The method of claim 15, And the service information comprises one or more of data information, audio information, video information, video information, and digital broadcasting information. The method of claim 17, The video information, the video information, and the digital broadcasting information includes at least one of the resolution information of the image, and the display size information of the image. The method according to any one of claims 15, 17 and 18, And performing FEC coding for correcting an error occurring in transmission for each service information of the multiplexed plurality of service information of the OSDM signal. The method of claim 19, And further amplifying the multiplexed plurality of pieces of service information of the OMD signal. delete In the OMD receiver for receiving an OMD signal including a plurality of service information sequentially multiplexed differently with time through a predetermined band according to the type information of each service information, Means for receiving an OMD signal including the plurality of service information; And means for performing a restoration of the FM signal including the plurality of service information received based on the type information of the service information. The method of claim 22, The OS receiver of claim 1, wherein one or more pieces of service information can be selected and received. In the signal processing method of the OPM receiver for receiving an OMD signal including a plurality of service information sequentially multiplexed differently with time through a predetermined band according to the type information of each service information, Receiving an OMD signal including the plurality of service information; And restoring an OMD signal including the plurality of service information received based on the type information of the service information. The method of claim 24, The method of claim 1, wherein one or more service information of the plurality of service information can be selected and received.

Images