KR100705330B1 - Apparatus and Method for repeating on common frequency in Digital broadcasting - Google Patents

Abstract

A co-channel relay apparatus for receiving a broadcast signal of the present invention for improving a transmission output by removing a feedback signal and transmitting the same in a same channel includes a receiver which receives a broadcast signal of an RF band, and converts the received broadcast signal into a base band. A demodulator, a feedback signal removing unit for removing a feedback signal caused by low isolation of a transmitting / receiving antenna of the same channel relay apparatus from the baseband broadcast signal, an equalizing unit for flattening the broadcast signal from which the feedback signal has been removed, And a modulator for converting the flattened broadcast signal into a broadcast signal of an RF band, an amplifier for amplifying the modulated broadcast signal, and a transmitter for transmitting the amplified broadcast signal.

Repeater, Feedback Signal

Description

Apparatus and Method for repeating on common frequency in Digital broadcasting}

1 is a schematic diagram showing the function of the same channel repeater;

2 is a functional block diagram showing the configuration of a conventional analog channel repeater;

Fig. 3A is a functional block diagram showing the structure of a conventional digital co-channel relay device;

Figure 3 (b) is a view showing the configuration of a conventional equalizer;

4 is a functional block diagram showing a configuration of an on-channel relay apparatus according to an embodiment of the present invention;

5 is a functional block diagram showing a configuration of an on-channel relay apparatus according to another embodiment of the present invention;

6 is a functional block diagram illustrating a configuration of an on-channel relay apparatus when a signal to be relayed according to an embodiment of the present invention is a CDMA scheme;

7 is a functional block diagram illustrating a configuration of a feedback signal removing unit of an on-channel relay apparatus according to an embodiment of the present invention.

8 is a flowchart illustrating an on-channel relay method according to an embodiment of the present invention.

The present invention provides an on-channel relay apparatus and method for receiving a broadcast signal and transmitting the same channel. More particularly, the present invention provides a broadcast channel for receiving a broadcast signal, which can efficiently remove a feedback signal and improve the function of an equalizer. The present invention relates to a co-channel relay apparatus and a method thereof.

As the broadcasting system is switched from analog broadcasting to digital broadcasting, various digital broadcasting systems such as HD-TV, terrestrial DMB, and satellite DMB are being considered. When the relay repeats the same frequency as the signal transmitted from the main transmitter, the receiver can continuously receive the broadcast without switching channels even when moving in different areas, and in particular, to save the frequency resources. do. In a digital broadcasting system, since a receiver can process signals in different paths, a broadcasting system using the same frequency becomes possible.

1 is a schematic diagram showing the function of the same channel repeater. The broadcast system using the same frequency includes a main transmitter 11, a repeater 12, and a receiver 13. When the receiver 13 exists in the shaded area corresponding to the area where the signal of the main transmitter 11 does not reach, the broadcast device cannot be received, and thus the relay device receives the signal of the main transmitter 11 and retransmits it to the shaded area. (12) is necessary.

2 is a functional block diagram showing the configuration of a conventional analog channel repeater. The analog relay device includes a receiving antenna 21, an RF receiving unit 22, an amplifier 23, and a transmitting antenna 24. The signal transmitted from the main transmitter is received via the receiving antenna 21. The RF receiver 22 filters only the desired signal band, and the filtered signal is amplified to cover the shadow area in the amplifier 23. The amplified signal is transmitted to the shaded area through the transmitting antenna 24.

The feedback signal refers to a signal transmitted from the transmitting antenna 24 of the repeater to the shaded area, and then to the receiving antenna 21 of the repeater. The relay device having a different transmission frequency from the conventional transmission frequency removes the transmission signal mixed with the reception signal through filtering. However, in the analog channel repeater, such filtering is impossible, and thus the repeater repeats the process of amplifying and transmitting the feedback signal in the received signal.

Fig. 3A is a functional block diagram showing the structure of a conventional digital co-channel relay apparatus. The digital co-channel repeater includes a receiving antenna 31, an RF receiver 32, a demodulator 33, an equalizer 34, a modulator 35, an amplifier 36, and a transmit antenna 37. Include. The signal transmitted from the main transmitter is received through the receiving antenna 31 and filtered by the RF receiver 32 into the desired signal band. The filtered signal is converted into a baseband signal by the demodulator 33. The converted baseband signal is removed by the equalizer 34, the multipath signal, the feedback signal, the noise, and the like, and is converted into the RF band signal by the modulator 35. The converted RF band signal is amplified by the amplifier 36 and then transmitted to the shaded area through the transmission antenna 37.

In the digital co-channel repeater, even though the feedback signal is generated, since the equalizer makes a decision, the feedback signal is not continuously amplified and oscillated, but has the following problems. 3B is a diagram showing the configuration of a conventional equalizer. This shows the configuration of a Decision Feedback Equalizer (DFE) commonly used in relays. In order to remove InterSymbol Interference (ISI) from the baseband signal converted by the demodulator 33, a detector (Viterbi Decoder 42) is a nonlinear equalizer using the previous signal obtained by the decision (44). That is, the coefficients of the feed forward filter 41 and the feedback back filter 43 are changed by using the signal determined by the detector Viterbi Decoder 42, and the output of the feed forward filter 41 is changed. ISI can be removed from

In general, the repeater uses a Viterbi decoder having a length of 1 (TB) as a detector 42 in order to minimize the delay time of the equalizer 34 because the delay time is large. Although the equalizer 34 relayed the signal determined when TB was 1, it is later possible to determine whether the signal relayed in the past is the correct signal by increasing the TB. However, in the related art, since not only the signal transmitted from the main transmitter but also all the feedback signals are input, the feedback signal is removed when the coefficient of the feedback filter 43 is changed by finding out that the signal relayed in the past is wrong through additional TB. There is a problem that the performance is reduced.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a co-channel relay apparatus for receiving and transmitting a broadcast signal on the same channel, which can efficiently remove a feedback signal and improve the function of an equalizer. To provide a method.

The same channel relay apparatus for receiving a broadcast signal and transmitting the same on the same channel according to an embodiment of the present invention for achieving the object, the receiver for receiving a broadcast signal of the RF band, converting the received broadcast signal to a baseband A demodulator, a feedback signal removing unit for removing a feedback signal caused by low isolation of a transmitting / receiving antenna of the same channel relay apparatus from the baseband broadcast signal, an equalizing unit for flattening the broadcast signal from which the feedback signal has been removed, And a modulator for converting the flattened broadcast signal into a broadcast signal of an RF band, an amplifier for amplifying the modulated broadcast signal, and a transmitter for transmitting the amplified broadcast signal.

Preferably, the feedback signal remover includes a feedback signal estimation filter for receiving the signals output from the equalizer, and estimating the feedback signal, and a signal remover for removing the feedback signal estimated from the baseband signal. do.

Also, preferably, the feedback signal removing unit receives the signals output from the equalizer, and adjusts the coefficients of the feedback signal estimation filter to minimize the difference between the baseband broadcast signal converted by the equalizer and the estimated feedback signal. It may further include a filter coefficient updating unit for adaptively updating.

The same channel relay apparatus includes an error correction decoding unit for decoding and correcting an error correction code by outputting the signal from the equalizer, and an error correction code for error correction encoding the signal output from the error correction decoding unit and outputting the error correction code to the modulation unit. It may further include wealth.

In the present co-channel relay method, receiving and converting a broadcast signal of an RF band into a base band, and removing the feedback signal caused by low isolation of a transmit / receive antenna of the same channel relay apparatus from the baseband broadcast signal. Equalizing the broadcast signal from which the feedback signal has been removed; and converting the equalized broadcast signal into a broadcast signal of an RF band and amplifying and transmitting the same.

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

4 is a functional block diagram illustrating a configuration of an on-channel relay apparatus according to an embodiment of the present invention. The relay device includes a receiving unit 100 including a receiving antenna 101 and an RF receiving unit 102, a demodulation unit 103, a feedback signal removing unit 104, an equalizer 105, a modulator 106, An amplifier 107 and a transmitter 108 including a transmission antenna are included.

The RF band signal and the feedback signal transmitted from the main transmitter are received through the reception antenna 101 and filtered by the RF receiver 102 to the desired signal band. As described above, the feedback signal refers to a signal received through the reception antenna 101 included in the RF band signal transmitted from the main transmitter after being transmitted through the transmitter 108 in the relay device. The received signal is converted into a baseband signal by the demodulator 103. Since the converted baseband signal y includes not only the signal S (n) transmitted from the main transmitter, but also the feedback signal f (n), the feedback signal canceling unit 104 uses the converted baseband signal y from the converted baseband signal y. The feedback signal component is removed and only the signal transmitted from the main transmitter is output. The signal from which the feedback signal is removed is removed from the equalizer 105 by noise and converted into an RF band signal by the modulator 106. The converted RF band signal is amplified by the amplifier 107 and transmitted to the shaded area through the transmitter 108.

7 is a functional block diagram showing the configuration of the feedback signal removing unit 104 of the co-channel relay apparatus according to an embodiment of the present invention. The feedback signal remover may include a signal remover 401 and a feedback signal estimation filter 402, and may further include a filter coefficient updater 403. Referring to FIG. 7, S (n) refers to the nth signal transmitted from the main transmitter in the order of time in the nth order, and f (n) is received through the reception antenna 101 together with S (n). n Refers to the feedback signal. S '(n) is a signal from which the feedback signal is removed from the baseband signal converted by the demodulator 103 through the feedback signal removing unit 104, and the noise or the like is removed through the equalizing unit 105. to be. That is, S '(n) becomes a signal determined for S (n) through the feedback signal removing unit 104 and the equalizer 105. f '(n) refers to a signal estimated for f (n) in the feedback signal estimation filter 402.

The feedback signal removing unit 104 is a baseband signal (y) converted by the demodulation unit 103 and the first signal to the (n-1) signal previously outputted in order over time from the equalizer 105, That is, {S '(1), ..., S' (n-1)} is received as an input.

The feedback signal estimation filter 402 receives S '(1) to S' (n-1) and finds f '(n) which is an estimated value for the feedback signal f (n). In this case, the coefficient of the feedback signal estimation filter 402 may use a pre-initialized value, or may use the coefficient adaptively updated by the filter coefficient updater 403.

The signal removing unit 401 removes and outputs f '(n), which is an estimated feedback signal, from the baseband signal y. This output signal becomes a signal S '(n) from which noise is removed through the equalizer 105. S '(n), which is a signal determined for S (n), is stored, and when S (n + 1) and f (n + 1) are received, estimating the feedback signal f (n + 1) Used for.

The filter coefficient updater 403 uses an algorithm that adaptively updates the coefficients of the feedback signal estimation filter 402. Examples of such algorithms include Least Mean Square (LMS) and Recursive Least Squares (RLS). Etc. The filter coefficient updating unit 403 receives S '(1) to S' (n-1) and outputs the baseband signal y and the feedback signal f '(n) estimated by the feedback signal estimation filter 402. It operates in the direction in which the difference is minimized, thereby adaptively updating the coefficients of the feedback signal estimation filter 402. That is, y-f '(n) = {S (n) + f (n)}-f' (n), and an error signal that is a difference between the feedback signal f (n) and the estimated feedback signal f '(n). Will operate in the direction of minimum.

Referring to (b) of FIG. 3, the equalizer 105 relays a signal determined when TB (Trace Back) is 1, but after that, by further lengthening TB, it is determined whether the signal relayed in the past is a correct signal. The coefficient of the feedback filter 43 may be changed. The present invention first removes the feedback signal from the feedback signal removing unit 104, and the equalizing unit 105 determines the signal {S (n) + f (n)-f '(n) determined to be a signal transmitted from the main transmitter. }, If the signal relayed in the past through a sufficient TB is known to be wrong, it is possible to change the coefficient of the feedback filter 43 to output a more accurate value for S (n). That is, the performance of the equalizer can be improved by first removing the feedback signal.

5 is a functional block diagram showing the configuration of the same channel relay apparatus according to another embodiment of the present invention. The error correction decoding unit 202 and the error correction unit 203 are added to FIG. 4. The error correction decoder 201 decodes an error correction code for the signal from which the feedback signal remover 104 and the equalizer 201 have removed the feedback signal and noise, and corrects the error. The error correction coder 203 performs error correction encoding on the signal output from the error correction decoder 202. The signal output from the error correcting code unit 202 is converted into an RF band signal by the modulator 106. Since the inclusion of the entire error correction decoding unit may improve reception performance, the error correction decoding unit 202 and the error correction decoding unit 203 may be included when the restriction on the signal delay is small. Will be. At this time, the input of the feedback signal removing unit 104 is a signal y output from the demodulator 103 and a signal previously output from the error correcting code unit 203. In finding the estimated value f '(n) of the feedback signal, the first to (n-1) signals previously outputted in order from the error correcting code unit 203 over time, that is, {S' (1), By using S '(n-1)}, there is no problem of ambiguity between signals compared in the feedback signal estimation filter.

FIG. 6 is a functional block diagram showing the configuration of the same channel relay apparatus when the relaying signal is a CDMA scheme according to an embodiment of the present invention. Conventionally, since the function of removing the feedback signal is included in the equalizer, it was only available for the VSB modulation method. However, the present invention removes the feedback signal first through the feedback signal removing unit 104 and then equalizes the modulation method. The restriction on is reduced. Therefore, it can also be used for CDMA communication. When a signal to be relayed is combined with a plurality of signals within the same frequency using a code division multiple access (CDMA) scheme, the channel separator 301 receives a signal output from the feedback signal removing unit 104. Each signal is divided by correlating orthogonal codes of a signal and a set of the codes. The equalizer 302 removes noise and the like from each divided signal, and each signal is spread by the PN code in the signal synthesizer 303 and then synthesized into one signal. At this time, since the input of the feedback signal removing unit 104 is a signal y output from the demodulation unit 103 and a signal previously output from the equalization unit 302 and synthesized by the signal synthesizing unit 303, an ambiguity problem also occurs. I never do that.

8 is a flowchart illustrating an on-channel relay method according to an embodiment of the present invention.

In operation S501, an RF band broadcast signal is received and converted into a baseband signal.

The converted baseband signal y includes not only the signal S (n) transmitted from the main transmitter, but also the feedback signal f (n) transmitted through the transmission antenna of the relay device and received by the reception antenna of the relay device. The feedback signal is removed (S502).

Referring to FIG. 7, the feedback signal estimation filter 402 is equalized in step S503 and outputs the first to the (n-1) -th signals, that is, {S '(1), .. , S '(n-1)} is used to find f' (n), which is an estimated value for the feedback signal f (n). The coefficient of the feedback signal estimation filter 402 may use an initialized value, or may use the coefficient adaptively updated by the filter coefficient updater 403.

The signal removing unit 401 removes and outputs f '(n) estimated by the feedback signal estimation filter 402 from the baseband signal y converted in step S501. This output signal is equalized by removing noise and the like in step S503, and is converted into an RF band broadcast signal, amplified and transmitted in step S504. As a result, the signal equalized in step S503 becomes S '(n). S '(n) is transmitted through the transmitting antenna of the relay in step S504 and then stored for use in estimating the feedback signal f (n + 1) received through the receiving antenna of the relay over time. .

The filter coefficient updating unit 403 receives S '(1) to S' (n-1), and the baseband signal y and the feedback signal estimated by the feedback signal estimation filter 402 converted in step S501. It operates in a direction in which the difference of f '(n) is minimized, thereby adaptively updating the coefficients of the feedback signal estimation filter 402. Examples of such algorithms include LMS and RLS, as described above. That is, y-f '(n) = {S (n) + f (n)}-f' (n), and an error signal that is a difference between the feedback signal f (n) and the estimated feedback signal f '(n). Will operate in the direction of minimum.

As described above, by using the same channel relay apparatus and method for receiving the broadcast signal and transmitting the same signal through the same channel, the feedback signal can be efficiently removed and the function of the equalizer can be improved.

While the above has been shown and described with respect to preferred embodiments of the present invention, the present invention is not limited to the specific embodiments described above, it is usually in the technical field to which the invention belongs without departing from the spirit of the invention claimed in the claims. Various modifications can be made by those skilled in the art, and these modifications should not be individually understood from the technical spirit or the prospect of the present invention.

Claims (5)

In the same channel repeater for receiving a broadcast signal and transmitting the same channel, Receiving unit for receiving a broadcast signal of the RF band; A demodulator for converting the received broadcast signal into a base band; A feedback signal removing unit for removing a feedback signal received through the receiving unit from the signal transmitted by the same channel relay apparatus in the baseband broadcast signal; An equalizer for flattening the broadcast signal from which a feedback signal has been removed; A modulator for converting the flattened broadcast signal into a broadcast signal in an RF band; An amplifier for amplifying the modulated broadcast signal; And And a transmitter for transmitting the amplified broadcast signal. The same channel relay apparatus for receiving a broadcast signal and transmitting the same on the same channel. The method of claim 1, wherein the feedback signal removing unit, A feedback signal estimation filter which receives the signals output from the equalizer and estimates the feedback signal; And And a signal remover for removing the feedback signal estimated from the baseband signal. The same channel relay apparatus for receiving a broadcast signal and transmitting the same on the same channel. The method of claim 2, wherein the feedback signal removing unit, A filter coefficient updating unit receiving the signals output from the equalizing unit and adaptively updating the coefficients of the feedback signal estimation filter to minimize the difference between the baseband broadcast signal converted by the equalizing unit and the estimated feedback signal; Receiving a broadcast signal that further comprises a same channel relay apparatus for transmitting on the same channel. The method of claim 1, An error correction decoding unit for correcting the signal output from the equalizer by decoding an error correction code; And And an error correction coder for error correcting encoding the signal output from the error correction decoder and outputting the signal to the modulator. The same channel relay apparatus for receiving a broadcast signal and transmitting the same on the same channel. Receiving a broadcast signal in an RF band and converting the signal into a base band; Removing the feedback signal received through the receiver from the signal transmitted by the same channel relay apparatus in the baseband broadcast signal; Equalizing the broadcast signal from which the feedback signal has been removed; And And converting the equalized broadcast signal into a broadcast signal of an RF band, amplifying and transmitting the broadcast signal, and transmitting the received broadcast signal through the same channel.

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