RU2219676C2 - Method for broadcasting information television programs - Google Patents

Abstract

FIELD: television and sound diffusion engineering. SUBSTANCE: method designed for distributing information programs in mobile networks includes digital compression of image signals and accompanying sound during transmission, their multiplexing to obtain compressed information television signal, noise-suppressing channel coding, carrier modulation using orthogonal frequency division of channels, and radiation; during reception it includes carrier signal demodulation, division of digital image signals and accompanying sound, their digital decoding and reproduction; transmission also includes subsampling and compression of image signals, addition of random value phase increment assigned out of set of random values known in advance to each signal subcarrier upon modulating carriers of orthogonal frequency division of channels, frequency conversion of highfrequency signal shaped in this way, and its radiation over narrowband , such as 250-500 MHz, municipal mobile channel; upon demodulation random-value phase increment introduced during transmission is subtracted in each signal subcarrier and during reproduction subsampling introduced during transmission is eliminated and image signal is returned to original form. Proposed method ensures no-break reception of television programs and/or audio stereophonic broadcasting in multiple-beam environment with rapidly changing phase structure of field during flow of traffic. EFFECT: enhanced reliability of television program reception. 2 cl, 2 dwg

Description

 The invention relates to techniques for television and sound broadcasting and the organization of television information broadcasting and sound stereo broadcasting, can be used for lower dynamics of moving images when the location of the receiver in moving vehicles in urban areas with dense buildings, multipath and the lack of direct visibility of the transmitter antenna, as well in areas with difficult terrain, in mountainous areas and in dense forests, where under the indicated conditions television with Useful systems can not provide a satisfactory reception quality.

 The known method of analog television broadcasting (GOST 7845. Broadcast television system. Main parameters. Measurement methods.), Including on the transmitting side the conversion of the image and sound into an electrical analog signal, modulation of the radio carriers by these signals, and on the receiving side - demodulation of the radio carriers and image reproduction and sound, does not allow for the reception and playback of images on mobile devices in urban environments with dense buildings, many due to the lack of direct visibility of the transmitter antenna, as well as in areas with difficult terrain, in mountainous areas and in dense forests, where the channel bandwidth can be narrowed to 250-300 kHz and the field strength decreases during sudden changes in time compared to the direct conditions visibility reaches 20-30 dB.

 The closest in technical essence to the claimed technical solution is a method of digital television broadcasting according to the DVB-T (Digital Video Broadcasting (DVB) standard. Personnel structure, channel coding and modulation for digital terrestrial television. European standard (Telecommunication series). ETSI. EN 300 744 IV.1.12 (1997-08), which includes digital compression of image and sound signals during transmission, their multiplexing, noise-proof channel coding, OFDM carrier modulation and radiation, and at the reception, a demo carrier spacing, separation of digital image and sound signals, their digital decoding and playback.

 The disadvantage of this method is the wide frequency band occupied by the full television signal, which does not allow its use on mobile devices in urban areas with dense buildings, multipath and the lack of direct visibility of the transmitter antenna, as well as in areas with difficult terrain and in mountainous areas.

 The objective of the present invention is to provide a system that allows for the uninterrupted reception of a television program and / or stereo sound broadcasting in a moving vehicle, under conditions of sharply reduced field strength in the presence of multipath, narrow-band transmission channel and rapid change in the phase structure of the field during traffic.

 The invention consists in a method that includes digital compression of image and sound signals during transmission, multiplexing them to produce a compressed information television signal, noise-proof channel coding, carrier modulation using orthogonal frequency division of channels (OFDM) and radiation, and, on reception, carrier demodulation signal, separation of digital compressed image and sound signals, their digital decoding and playback; t and then compress the image signals, after modulating the OFDM carriers, a phase increment of a random variable assigned from a set of previously known random variables is added to each signal subcarrier, the high-frequency signal thus formed is converted in frequency and emitted by a narrowband, in particular 250-500 kHz, mobile the city channel, after demodulation at each subcarrier of the signal, it subtracts the random increment entered in the transmission phase transmission, and during playback eliminates the thinning and return the image signal to its original form. The introduction of random phase additives makes the signal noise-like with a significantly reduced peak factor, which allows it to be received with a significantly lower signal / noise ratio than with strictly determined phase assignments.

 In addition, a stereo audio signal is additionally encoded on the transmission and its statistical multiplexing is performed with the compressed information television signal, and on the receiving side, after demodulation, the stereo audio signal is extracted and decoded. Statistical multiplexing allows you to use the time points of each of the combined signals, in which the flow of information is reduced, to supplement it with part of the flow of the second signal. As a result, the total frequency band needed to transmit the two combined signals is significantly reduced compared to the sum of the bands occupied by each of the signals.

 The invention relates to techniques for television and sound broadcasting and can find application for the distribution of information programs in stationary and mobile networks in conditions of reduced bandwidth of communication channels.

 Figure 1 shows one of the possible transmitting parts of the device for implementing the method.

 This device has two main inputs - an image signal and sound, the first of which is connected through units of decimation of the number of frames and pixels in each frame 1 and compression of the image signals 2 to one of the inputs of the multiplexer 3, the second input of which is connected to the input of the sound signals through a compression unit 4, and the output through a series-connected channel coding unit 5, an OFDM modulator unit 6, an additional phase coding unit for subcarriers 7, a frequency conversion and radio signal amplification unit 8 to the transmitting antenna, while a third input of the multiplexer 3 is connected to a stereo sound signal through the additional compression unit 9. When simultaneous transmission of image signals with audio signals and stereo audio multiplexer 3 performs a statistical multiplexing of all signals.

 Figure 2 shows one of the possible options for the receiving part of the device for implementing the method.

 It contains serially connected receiver unit 10, demodulator unit 11, channel decoding unit 12, demultiplexer unit 13, one of the outputs of which is connected to the image signal decoding unit 14 connected in series, the frame number recovery unit 15 and the reproducing device, its second output is connected to the unit restoration of audio signals 16, and the third output to an additional unit for the restoration of stereo audio signal 17. Blocks 16 and 17 are connected through a switch 18 and the output will amplify Do 19 with speakers that reproduce sound or mono TV or stereo.

 The proposed method is as follows.

 The image signal is fed to block 1 (Fig. 1), in which the frames are thinned out and pixels are processed in the frame to reduce the number of frames and reduce the resolution of the images, then the signal is sent to compression unit 2 and then to multiplexer 3. At the same time, to the second input of this the same multiplexer receives a sound signal through a vocoder compression unit 4. Next, the signal is channel encoded in block 5, after which it is fed to the OFDM modulator 6, to each signal subcarrier at the output of which is added in block 7 a phase increment of a random variable assigned from a set of previously known random variables. The high-frequency signal thus formed is frequency-converted by the frequency converter of the transmitter 8 and radiated through a narrow-band, in particular 250-500 kHz, mobile city channel using a transmitting antenna.

 In the block diagram of FIG. 1, dashed lines show an option in which an additional stereo audio signal is present, which is compressed in block 9. In this case, statistical multiplexing is used in multiplexer 3.

 The signal, after the receiver unit 10 (Fig. 2), is fed to the demodulator 11, in which the subdivision of the random increment introduced in the transmission is subtracted from each subcarrier, and then to the channel decoding unit 12. From this block, the signal is supplied to the demultiplexer 13, in which it is divided into an image signal, restored in block 14 and then fed to block 15, which eliminates the decimation introduced in the transmission and returns the signal to its original form, to the sound signal restored in bl osk 16, and the stereo signal restored in the additional unit 17. The switch 18 is used to supply either a sound signal of television (from the output of block 16), or stereo signals (from the outputs of the additional block 17) to the output sound amplifiers 19.

Claims (2)

1. A method for broadcasting information television, including digital compression of image and sound signals during transmission, multiplexing them to obtain a compressed information television signal, noise-proof channel coding, carrier modulation using orthogonal frequency division multiplexing (OFDM) and radiation, and at reception, demodulation carrier signals, the separation of digital image signals and sound, their digital decoding and playback, characterized in that the transmission signals are decimated and then the image signals are compressed, after modulating the OFDM carriers, a phase increment of a random variable assigned from a set of previously known random variables is added to each signal subcarrier, the high-frequency signal thus formed is converted in frequency and emitted in a narrow-band, in particular 250-500 kHz, mobile city channel, after demodulation, each subcarrier of the signal subtracts the phase increment of the random variable entered in the transmission, and when playing the device remove the introduced for thinning and return the image signal to its original form. 2. The method according to claim 1, characterized in that the transmission further encodes the stereo audio signal and performs its statistical multiplexing with the compressed information television signal, and on the receiving side after demodulation, the stereo audio signal is extracted and decoded.

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