KR100749678B1 - Method and apparatus for removing interference between input and output signal, a same frequency gap filler in a terrestrial DMB system - Google Patents

Abstract

Disclosed are a method and apparatus for removing an error component due to interference between transmission and reception channels when terminating a same channel in a terrestrial DMB, and a terrestrial DMB cochannel gap filler using the same. According to the present invention, an apparatus for removing interference between input and output signals in a terrestrial DMB using the same channel relay method includes an A / D converter for converting an input signal into a digital signal; A filter for filtering and extracting an error signal due to interference between input and output signals included in the converted digital signal; A coefficient calculator which receives the converted digital signal and calculates coefficients used in the filter; A mixer for removing the filtered error signal from the A / D converted digital signal; And a D / A converter converting the mixed signal into an analog signal. As a result, an error generated due to interference due to coupling between the transmission and reception channels can be reduced without having to physically separate the physical distance between the transmission and reception channels.

Description

Method and apparatus for removing interference between transmitting and receiving channels according to co-channel relaying of terrestrial DMB, and gap filler using the same {Method and apparatus for removing interference between input and output signal, a same frequency gap filler in a terrestrial DMB system}

1a and 1b is a configuration diagram of a terrestrial DMB and satellite DMB system,

2 is a configuration diagram showing an example of a gap filler for covering the radio wave shadow area;

3 is a diagram illustrating a terrestrial DMB gap filler according to an embodiment of the present invention;

4 is a detailed configuration diagram of a terrestrial DMB gap filler according to an embodiment of the present invention;

5 is an operation flowchart of a terrestrial DMB gap filler according to an embodiment of the present invention;

6 is a diagram illustrating a transmission frame structure of a terrestrial DMB;

7 is a flowchart illustrating an interference error cancellation process in a terrestrial DMB gap filler according to an embodiment of the present invention.

The present invention relates to digital multimedia broadcasting, and more particularly, to a method and apparatus for removing an error component due to interference between transmission and reception channels during the co-channel relay in a terrestrial DMB, and a terrestrial DMB co-channel gap filler using the same.

Conventional analog broadcasting has poor power efficiency because its receiving device drastically degrades the received signal when moving, and uses high transmit power to reduce the influence of noise, and other frequencies in neighboring areas to avoid interference between channels. Because of this, there is a technical limitation such as poor spectral efficiency. Accordingly, researches on digital audio broadcasting (DAB), which can replace conventional analog AM and FM radio broadcasting, have been conducted.

Digital audio broadcasting (DAB) not only can transmit high quality audio through audio channels, but also various additional data such as still images, video, graphics, and text through data channels. This is called Digital Multimedia Broadcasting (DMB). Examples of multimedia services that can be provided by the DMB include, for example, travel and traffic information services, program headline text and images combined, or weather forecast and traffic information combined with electronic maps. Examples of such services include independent information services that are independent of programs such as website broadcasting or GPS for DMB, and video transmission services.

As a standard for DMB, EUREKA-147 describes the use of high-quality audio compression technology in accordance with MPEG-1 Audio Layer II with a bandwidth of about 2 MHz to provide CD level audio services and various additional services.

On the other hand, DMB includes terrestrial DMB and satellite DMB, and as in the current terrestrial television relay system, terrestrial DMB transmits DMB broadcast radio waves using terrestrial relay equipment, and transmits DMB radio waves through satellite. This is a satellite DMB. However, in both terrestrial DMB and satellite DMB, there is a radio shading area where the strength of broadcast radio waves transmitted from terrestrial relay facilities or satellites is weak, and a relay device called a gap filler is required to solve this problem. The gap filler is a relay device that receives and amplifies DMB broadcast radio waves from a terrestrial repeater or satellite, and transmits them in a frequency band that can be received by the DMB terminal.

The gap filler includes a heterogeneous channel relay type gap filler and a co-channel relay type gap filler. The gap filler of the heterogeneous channel relay method receives a DMB broadcast signal through a wired or wireless channel separate from the DMB broadcast channel, modulates and amplifies according to the modulation method and frequency that the DMB terminal can receive, and transmits a radio wave through an antenna. Eliminate radio shading areas. The gap filler of the same channel relay method directly receives, filters, and amplifies a DMB broadcast signal of a DMB broadcast channel, and transmits a radio wave through an antenna so that the DMB terminal can receive it.

Therefore, the radio shading cancellation method using the gap filler of the heterogeneous channel relay method is expensive because the separate wired or wireless channel must be provided to transmit the DMB broadcast signal to the gap filler, but the interference between the received signal and the transmitted signal in the gap filler is high. The phenomenon can be avoided. On the other hand, the radio wave shading cancellation method using the gap filler of the same channel relay method does not require a separate channel for transmitting the DMB broadcast signal, but due to interference due to coupling between the receiving antenna and the transmitting antenna, The performance of the system is degraded due to distortion or oscillation. The signal-to-noise ratio is lowered by simply amplifying the radio wave received through the receiving antenna and transmitting it through the transmitting antenna. In order to solve this problem, it is necessary to isolate the transmitting and receiving antennas. To this end, since the physical distance between the transmitting and receiving antennas must be sufficiently far, the cost increases.

Accordingly, an aspect of the present invention is to provide a method and apparatus for removing an error of a DMB broadcast signal caused by interference due to coupling between transmission and reception channels in a gap filler of a terrestrial DMB using a co-channel relay method.

Another object of the present invention is to provide a gap filler using the error elimination method and apparatus.

According to an aspect of the present invention, there is provided an apparatus for canceling interference between input and output signals in a terrestrial DMB using a same channel relay method, the apparatus comprising: an A / D converter converting an input signal into a digital signal; A filter for filtering and extracting an error signal due to interference between input and output signals included in the converted digital signal; A coefficient calculator which receives the converted digital signal and calculates coefficients used in the filter; A mixer for removing the filtered error signal from the A / D converted digital signal; And a D / A converter converting the mixed signal into an analog signal.

The coefficient calculating unit performs an FFT by finding a phase reference symbol by finding a null symbol in a DMB transmission frame that is the A / D converted digital signal, and performing an FFT, using an FFT value and the phase reference symbol. It is desirable to obtain a system transfer function by calculating a, and to obtain an impulse response of an interference component due to interference between transmission and reception channels by performing normalization and IFFT to obtain coefficients used for the FIR filtering by weighting previous coefficient values.

In addition, the technical problem is a gap filler of a terrestrial DMB using the same channel relay method, the receiver for receiving a DMB broadcast signal; An interference component removing unit for removing interference between the received signal and a signal to be transmitted; A transmitter for amplifying and outputting a signal from which the interference component is removed; And an oscillator for generating a clock signal used for converting the frequency bands of the receiver and the transmitter.

On the other hand, according to another field of the present invention, the technical problem in the interference cancellation method between the input and output signals in the terrestrial DMB using the same channel relay method, A / D conversion step of converting the received signal into a digital signal; A filtering step of filtering and extracting an error signal due to interference between input and output signals included in the converted digital signal; A coefficient calculating step of receiving the converted digital signal and calculating coefficients used in the filter; A mixing step of removing the filtered error signal from the A / D converted digital signal; And a D / A conversion step of converting the mixed signal into an analog signal.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1A and 1B are configuration diagrams of a terrestrial DMB and satellite DMB system.

Referring to FIG. 1A, the terrestrial DMB system includes a DMB broadcasting station 110, a transmitting station 120, DMB terminals 130 and 160, and a gap filler 140. The DMB broadcasting station 110 has a DMB broadcasting content produced by a studio or an external content producer and transmits it to the transmission station 120. The transmitting station 120 transmits the DMB broadcast according to the frequency band of the broadcasting company, and the DMB terminal 130 may receive the DMB broadcasting content and play the DMB broadcasting content. However, the DMB terminal 160 in the radio shade area 150 where the intensity of the radio wave transmitted from the transmitting station 120 is weak due to a distance from the transmitting station 120 or a building or an obstacle is poor. Since the phenomenon such as the screen is cut off or the like, the gap filler 140 receives the DMB broadcast signal from the transmitting station 120 and amplifies it, thereby eliminating the radio shade area 150.

Referring to FIG. 1B, the satellite DMB transmits a DMB broadcast signal to the DMB terminals 135 and 165 through the satellite 125. Accordingly, the gap filler 145 receives the radio wave from the satellite 125 to solve the radio shade area 155. The DMB terminals 135 and 165 are terminals capable of receiving DMB broadcasts transmitted through satellite DMB channels.

2 is a configuration diagram illustrating an example of a gap filler for covering a radio wave shadow area.

The gap filler includes a receiving antenna 210, a receiving unit 220, a signal processing unit 230, a transmitting unit 240, and a transmitting antenna 250. The receiving antenna 210 receives a DMB broadcast signal from a transmitting station or a satellite, and the receiving unit 220 extracts a signal corresponding to a frequency band of the DMB operator through filtering or the like. The signal processor 230 amplifies the received DMB broadcast signal. If necessary, the signal is converted to match the frequency band transmitted by the transmitter 240. For example, if a radio wave modulated according to a time division multiplexing (TDM) method is received from a transmission station or a satellite, and the terminal modulates the radio wave according to a code division multiplexing (CDM) method, the modulation method is also changed accordingly. You can also perform an operation. The transmitter 240 transmits the amplified DMB broadcast signal through the transmit antenna 250.

3 is a configuration diagram of a terrestrial DMB gap filler according to an embodiment of the present invention.

Referring to FIG. 3, the gap filler includes a receiver 310, an A / D converter 320, a signal processor 330, a mixer 340, a D / A converter 350, a transmitter 360, and an oscillator ( 370). The receiver 310 includes a filter and extracts a signal suitable for a DMB broadcasting frequency from the received DMB signals. Then, the A / D converter 320 converts the digital signal. The digitally converted signal is input to the signal processor 330 to calculate and output an error component generated by interference due to the coupling between the receiver 310 and the transmitter 360. The mixing unit 340 outputs a signal from which the interference error component is removed by subtracting the error component from the A / D converted original signal. The signal thus made is input to the D / A converter 350, converted into an analog signal, and then made into a signal suitable for the transmission frequency band through the transmitter 360, and then transmitted through the transmit antenna. At this time, the oscillator 370 is used for frequency down-conversion and up-conversion in the receiver 310 and the transmitter 360. Here, the A / D converter 320, the signal processor 330, the mixer 340, and the D / A converter 350 are called an interference component remover.

4 is a detailed configuration diagram of a terrestrial DMB gap filler according to an embodiment of the present invention.

Referring to FIG. 4, the bandpass filter 1 405, the SAW filter 410, the A / D converter 415, the coefficient calculator 420, the filter 425, the mixing unit 430, and the D / A The converter 435 includes a band pass filter 2 440, a high output amplifier 445, a channel filter 450, an oscillator 1 455, and an oscillator 2 460.

When a signal transmitted through the DMB broadcasting channel is input to the antenna, the signal of the DMB broadcasting frequency band is filtered through the band pass filter 1 405. The filtered signal is changed to a low frequency band according to the signal of the oscillator 1 455 and input to the surface acoustic wave (SAW) filter 410, thereby optimizing the signal-to-noise ratio according to the characteristics of the SAW filter 410. The SAW filtered signal is changed into a signal of an intermediate frequency (IF) band according to the signal of the oscillator 2 460 before being input to the A / D converter 415. This signal is input to the A / D converter 415 and converted into a digital signal.

The filter 425 extracts an error component due to interference. The filter 425 receives an A / D converted signal and performs FIR filtering as an example. The coefficient calculator 420 receives an A / D converted signal and uses an sync symbol described in Eureka-147 to impulse filter coefficients of an inverse function of an interference signal due to coupling between transmission and reception channels. Obtain the response and output the filter coefficients.

An error signal generated by interference due to coupling is output by the coefficient calculator 420 and the filter 425, and the error signal is mixed by the mixing unit 430 to generate a DMB broadcast signal from which an error component is removed. The signal is then converted into an analog signal by the D / A converter 435. The analog signal thus converted is made into an amplified signal of a transmission frequency band through the band pass filter 2 440, the high power amplifier 445, and the channel filter 450, and is transmitted through a transmission antenna. In this process, the oscillator 1 455 and the oscillator 2 460 are made into signals of the original frequency band.

5 is an operation flowchart of a terrestrial DMB gap filler according to an embodiment of the present invention.

Referring to FIG. 5, the flow of operations of receiving and relaying a DMB broadcast signal using the gap filler of FIG. 4 will be described. First, the DMB broadcast signal is received, and the signal of the broadcast frequency band is filtered and extracted (S510). In this process, frequency downconversion and SAW filtering are performed to optimize the signal-to-noise ratio. The signal-optimized signal ratio is A / D converted to calculate an error component generated by the interference due to the coupling (S520). With the A / D converted digital signal, filter coefficients for interference component removal are calculated (S530). The filtering is performed by applying the calculated filter coefficients (S540). A detailed description of the calculation and filtering process of the filter coefficient will be described later with reference to FIG. 7.

The error component thus produced is mixed with the original signal to produce a DMB broadcast signal from which the error component has been removed (S550). After the D / A conversion step is made into an analog signal (S560). After the signal amplification step (S570) is transmitted in accordance with the frequency band of the transmitting antenna (S580).

6 is a diagram illustrating a transmission frame structure of terrestrial DMB.

The transmission frame of the terrestrial DMB includes a synchronization channel (SC) 610, a fast information channel (FIC) 620, and a main service channel (MSC) 630. Include. The synchronization channel 610 includes a null symbol 611 for frame synchronization and a phase reference symbol 612 for differential quadrature phase shift keying (DQPSK) demodulation. The null symbol 611 contains a value of '0', and the phase reference symbol 612 provides a reference phase used to modulate an OFDM symbol with a predetermined pattern and is defined in Eureka-147, a standard specification of DMB. Value. The fast information channel 620 is used to transmit information necessary for the DMB receiver to process data, for example, information on a service configuration, a multiplexed form, and the like, or to transmit data that needs to be quickly transmitted. The main service channel 630 is a channel containing data to be actually transmitted.

One OFDM symbol consists of a valid data interval 632 of 1ms long and a Guard Interval 631 of 0.25ms long. Therefore, one transmission frame is composed of a null symbol, a phase reference symbol, three FIC symbols, and 72 MSC symbols, and the total length is 96 ms.

7 is a flowchart illustrating an interference error cancellation process in a terrestrial DMB gap filler according to an embodiment of the present invention.

Referring to FIG. 5, the A / D-converted signal is input by the above-described step S530, and a null symbol 611 is repeated in 96 ms in the frame of the terrestrial DMB (S705), and the phase reference symbol 612 following the null symbol is found. In step S710, the FFT is performed on a signal estimated to be an interval. When the FFT is performed, the signal S (n, k) in the frequency domain is output. In this case, n denotes a repetition number of variable coefficients for updating the filter coefficients in the filter 425, and k denotes a subcarrier order of FFT size.

Therefore, since the FFT is performed on the signal estimated in the phase reference symbol 612 section, the inverse function is used by using the phase reference symbol signals T (n, k) and S (n, k) to find out the actual signal sent from the original transmission station. F (n, k) = S (n, k) / T (n, k) is calculated (S715). The calculated inverse function F (n, k) is a system error function of the gap filler. The calculated inverse function is made to 1-1 / F (n, k) through a normalization process (S720). If this is called er (k), the IFFT is performed to minimize the value and reduce the error generated by the interference caused by the coupling between the transmission and reception channels (S725). Taking the IFFT gives the impulse response of the error component produced by the interference due to the coupling.

Next, the rectangular window is taken to update the coefficients of the filter 425 (S730), and coefficient weighting is performed with the weight mu (S735). The coefficient weighting process is to accumulate and reflect the calculation result of the coefficient value. The coefficients thus produced are delayed to remove the error component (S745), and when the delayed signal and the coefficient weighted signal are mixed (S740), the filter coefficients w (n, k) = w (n-1, k) are finally obtained. ) + μr (k) er (n, k) is output. The filter coefficient is transmitted to the filter 425 and used as a filter coefficient for FIR filtering (S750). When an error component is generated, a DMB broadcast signal is mixed with the initial signal to remove the error component (S755).

On the other hand, the above-described method for removing the interference component between the transmission and reception channels according to the same channel relay of the terrestrial DMB can be prepared by a dedicated chip, FPGA or computer program. Codes and code segments constituting the program can be easily inferred by a computer programmer in the art. In addition, the program is stored in a computer readable media, and read and executed by a computer, thereby implementing a method of removing interference components between transmit and receive channels according to the same channel relay of the terrestrial DMB. The information storage medium includes a magnetic recording medium, an optical recording medium, and a carrier wave medium.

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

As described above, according to the present invention, the error generated by the interference due to the coupling between the transmission and reception channels can be reduced without dropping the physical distance between the transmission and reception channels, and thus, the gap filler using the same can be installed in a narrow space. Reduce costs In addition, there is an effect that can reduce the degradation of the signal and also improve the signal to noise ratio.

Claims (9)

In the interference canceling device between input and output signals in the terrestrial DMB using the co-channel relay method, An A / D converter converting the input signal into a digital signal; A filter for filtering and extracting an error signal due to interference between input and output signals included in the converted digital signal; A coefficient calculator for calculating filter coefficients by finding a null symbol in a DMB transmission frame, which is the A / D converted digital signal, obtaining frame synchronization to find a phase reference symbol, performing an FFT, and performing an IFFT; A mixer for removing the filtered error signal from the A / D converted digital signal; And And a D / A converter for converting the digital signal from which the error signal has been removed to an analog signal. delete The method of claim 1, wherein the coefficient calculation unit Implement FFT on the phase reference symbol, calculate an inverse function using the FFT value and the phase reference symbol to obtain a system transfer function, perform normalization and IFFT, and impulse response of interference components due to interference between transmission and reception channels. And obtain coefficients used in the filter by weighting previous coefficient values. In the gap filler of the terrestrial DMB using the co-channel relay method, A receiver which receives a DMB broadcast signal; An A / D converter which removes interference between the received signal and a signal to be transmitted and converts the received signal into a digital signal; A filter for filtering and extracting an error signal due to interference between input and output signals included in the converted digital signal; Find a null symbol in a DMB transmission frame that is the A / D converted digital signal, obtain frame synchronization, find a phase reference symbol, perform an FFT, calculate an inverse function using the FFT value, and the phase reference symbol, and transfer the system. A coefficient calculator which obtains a function, obtains an impulse response of an interference component due to interference between transmission and reception channels by performing normalization and IFFT, and obtains coefficients used in the filter by weighting previous coefficient values; A mixer for removing the filtered error signal from the A / D converted digital signal; And a D / A converter configured to convert the digital signal from which the error signal is removed into an analog signal. A transmitter for amplifying and outputting a signal from which the interference component is removed; And And an oscillator for generating a clock signal used to convert frequency bands of the receiver and the transmitter. delete delete In the interference cancellation method between the input and output signals in the terrestrial DMB using the co-channel relay method, An A / D conversion step of converting an input signal into a digital signal; A filtering step of filtering and extracting an error signal due to interference between input and output signals included in the converted digital signal; A coefficient calculating step of calculating filter coefficients by finding a null symbol in a DMB transmission frame, which is the A / D converted digital signal, obtaining frame synchronization to find a phase reference symbol, performing an FFT, and performing an IFFT; A mixing step of removing the filtered error signal from the A / D converted digital signal; And And a D / A conversion step of converting the digital signal from which the error signal is removed to an analog signal. delete 8. The method of claim 7, wherein the counting step Performing an FFT on the phase reference symbol; Calculating an inverse function using the FFT value and the phase reference symbol to obtain a system transfer function; And Performing normalization and IFFT on the system transfer function to obtain an impulse response of an interference component due to interference between transmission and reception channels, and obtaining coefficients used in the filter by weighting previous coefficient values. How to eliminate interference between the liver.

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