KR101333822B1 - Method and apparatus for canelling interference - Google Patents

Abstract

In the broadcast system to which the hierarchical modulation technique is applied, an apparatus for removing interference demodulates a hierarchical modulated signal including a service providing signal and a signal newly added to the service providing signal. Next, the interference elimination apparatus demodulates the service providing signal to generate service providing data, modulates the service providing data into a specific signal, and removes the interference signal corresponding to the specific signal from the demodulated hierarchical modulated signal.

Description

Interference elimination device and its method {Method and apparatus for canelling interference}

The present invention relates to an interference cancellation apparatus and a method thereof. In particular, the present invention relates to an apparatus and method for removing interference at a receiving end of a digital broadcasting system to which hierarchical modulation is applied.

The present invention is derived from a study conducted as part of the IT growth engine technology development of the Ministry of Knowledge Economy [Task Management Number: 2006-S-017-04, Task name: Development of terrestrial DMB transmission advancement technology].

Terrestrial-digital multimedia broadcasting ("T-DMB") is a broadcasting system that adds multimedia broadcasting services including video services to Eureka 147 based DAB (Digital Audio Broadcasting) system in Europe. A method of transmitting a DMB broadcast signal to a moving receiver using a located transmitter is used.

In order to service T-DMB's quality of service in SD (Standard Definition) level or to increase the number of service channels, a higher channel rate is required. Accordingly, by adopting a hierarchical modulation scheme to the T-DMB system, a mobile multimedia broadcasting system having a higher transmission rate for the same frequency bandwidth can be realized while maintaining backward compatibility with the existing T-DMB system.

Advanced Terrestrial Digital Multimedia Broadcasting (AT-DMB) with hierarchical modulation is called differential quadrature phase shift keying (AT-DMB), which is used for data transmission in conventional T-DMB systems. It is a broadcasting system that expands the data rate by up to 2 times by adding a signal modulated by a new modulation method to a signal called "DQPSK".

Since the AT-DMB system is compatible with the T-DMB system, a single frequency network (hereinafter referred to as "SFN") that transmits signals at the same frequency may be configured and operated.

In the SFN, AT-DMB can be operated as a local broadcast having a limited broadcast area by broadcasting at a small power to a specific region, and T-DMB can be operated as a global broadcast. At this time, the AT-DMB receiver receives a T-DMB signal and an AT-DMB signal at the same time, and the T-DMB signal acts as an interference signal source, thereby degrading reception performance.

An object of the present invention is to provide a method and apparatus for removing a T-DMB signal from a received signal received at a receiver of a terrestrial DMB system to which hierarchical modulation is applied.

In order to achieve the above object, a method for removing interference in a broadcast system to which a hierarchical modulation scheme according to a feature of the present invention is applied is

Demodulating a hierarchical modulated signal including a service provision signal and a signal newly added to the service provision signal, demodulating the service provision signal to generate service provision data, and modulating the service provision data into a specific signal And removing the interference signal corresponding to the specific signal from the demodulated hierarchical modulated signal.

According to another aspect of the present invention, an apparatus for removing interference in a broadcast system to which a hierarchical modulation technique is applied

A modulator for modulating the service providing data corresponding to the hierarchical modulated signal including a service providing signal and a signal newly added to the service providing signal into a specific signal, and removing the interference signal corresponding to the specific signal from the hierarchical modulated signal It includes an interference cancellation unit.

According to an embodiment of the present invention, the reception performance of the AT-DMB receiver may be improved in a single frequency network system including an AT-DMB system operated by local broadcasting and a T-DMB system operated by global broadcasting.

1 is a block diagram showing the configuration of a transmitting end of an AT-DMB system according to an embodiment of the present invention.
2 is a block diagram showing the configuration of a receiving end of an AT-DMB system according to an embodiment of the present invention.
3 is a block diagram showing a configuration of an interference cancellation apparatus at a receiving end of an AT-DMB system according to an embodiment of the present invention.
4 illustrates a channel impulse response according to an embodiment of the present invention.
5 is a flowchart illustrating a method of removing an interference signal at a receiving end of an AT-DMB system according to an embodiment of the present invention.

DETAILED DESCRIPTION Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art may easily implement the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In the drawings, parts irrelevant to the description are omitted in order to clearly describe the present invention, and like reference numerals designate like parts throughout the specification.

Throughout the specification, when a part is said to "include" a certain component, it means that it can further include other components, except to exclude other components unless otherwise stated.

Hereinafter, an interference cancellation apparatus and a method thereof according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram showing the configuration of a transmitting end of an AT-DMB system according to an embodiment of the present invention.

First, a transmitter of an AT-DMB system generates a hierarchically modulated broadcast signal by modulating a data stream in a different modulation scheme in one channel.

Hierarchical modulation generally modulates two separate data streams with HP (High Priority) modulation and LP (Low Priority) modulation. Here, the modulation scheme may be, for example, one of Quadrature Phase Shift Keying (QPSK), Quadrature Amplitude Modulation (16QAM), and 64QAM. For example, the LP modulation method may be 16 QAM, and the HP modulation method may be QPSK.

Streams modulated with HP modulation are called HP signals, and streams modulated with LP modulation are called LP signals.

The HP signal and the LP signal may contain the same content or may include completely different content. That is, the broadcaster may provide two completely different services having different forms on one channel.

When the HP signal and the LP signal contain the same content, the same content can be received by different kinds of devices. In addition, in order to transmit a single content regardless of the transmission environment, the HP signal and the LP signal may include the same content.

According to an embodiment of the present invention, the AT-DMB system generates a hierarchically modulated broadcast signal by adding a newly added LP signal to an HP signal which is a service providing signal corresponding to an existing T-DMB system.

The transmitting end of the AT-DMB system applies DQPSK modulation to the HP signal and transmits the modulated signal to the receiving end by adding a new modulation or the same modulation to the LP signal.

As shown in FIG. 1, the transmitting end of the AT-DMB system includes an HP signal processing apparatus 100, an LP signal processing apparatus 200, and a hierarchical modulator 300.

The HP signal processing apparatus 100 includes a convolutional encoder 110, a transmission frame multiplexer 120, a QPSK mapper 130, and a frequency interleaver ( 140 and a DPQSK modulator 150.

The convolutional code unit 110 corrects a bit error of an input HP signal using a convolution code.

The transmission frame multiplexer 120 multiplexes the HP signal correcting the bit error.

QPSK mapper 130 maps the multiplexed HP signal for quadrature phase shift modulation.

The frequency interleaver 140 interleaves the mapped HP signal in the frequency domain.

The DPQSK modulator 150 modulates the differential interleaved HP signals for hierarchical modulation.

The LP signal processing apparatus 200 includes a turbo coder 210, a transmission frame multiplexer 220, a QPSK mapper 230, and a frequency interleaver 240.

The turbo coder 210 corrects a bit error of the LP signal input using the turbo code.

The transmission frame multiplexer 220 multiplexes the LP signal correcting the bit error.

The QPSK mapper 230 maps the multiplexed LP signal.

The frequency interleaver 240 interleaves the mapped LP signals in the frequency domain.

The hierarchical modulation device 300 includes an OFDM signal generator 310. The OFDM signal generator 310 generates a hierarchically modulated broadcast signal by OFDM modulating the differentially-phase shifted HP signal and the interleaved LP signal.

Next, the receiving end of the AT-DMB system according to an embodiment of the present invention will be described in detail with reference to FIG.

2 is a block diagram showing the configuration of a receiving end of an AT-DMB system according to an embodiment of the present invention.

First, a receiver of an AT-DMB system receives a hierarchically modulated broadcast signal by adding a new LP signal to an HP signal, which is a service providing signal corresponding to an existing T-DMB system.

As shown in FIG. 2, the receiving end of the AT-DMB system includes an OFDM demodulator 400, an HP data processing apparatus 500, an interference cancellation apparatus 600, and an LP data processing apparatus 700.

The OFDM demodulator 400 receives a hierarchically modulated broadcast signal, that is, a received signal, received from a transmitting end of the AT-DMB system, and OFDM demodulates the received signal.

The HP data processing apparatus 500 includes a DPQSK demodulator 510, a frequency deinterleaver 520, a demapper 530, and a transmission frame demux 540. And a time deinterleaver 550 and a Viterbi decoder 560.

The DPQSK demodulator 510 demodulates the HP signal by differential four-phase shift.

The frequency deinterleaver 520 deinterleaves the demodulated HP signal in the frequency domain.

Demapper 530 demaps the deinterleaved HP signal.

The transmission frame demultiplexer 540 multiplexes the demapped HP signal.

The time deinterleaver 550 deinterleaves the multiplexed HP signals in the time domain.

The Viterbi decoder 560 corrects bit errors in the deinterleaved HP signal and outputs HP data.

The interference cancellation apparatus 600 includes an HP modulator 610 and an interference canceller 620.

The HP modulator 610 modulates the output of the HP data processing apparatus 500, that is, the HP data in which the error is corrected, into a T-DMB signal.

The interference canceller 620 receives the outputs of the OFDM demodulator 400 and the HP data processor 500, that is, the OFDM demodulated received signal and the T-DMB signal, and receives the T-DMB signal from the OFDM demodulated received signal. Remove

Next, the interference canceller 620 inputs the output of the interference canceller 620 from which the T-DMB signal is removed, to the LP data processing apparatus 700.

The LP data processing apparatus 700 includes an LP demodulator 710, a frequency deinterleaver 720, a demapper 730, a transmission frame demultiplexer 740, a time deinterleaver 750, and a turbo decoder ( 760).

The LP demodulator 710 demodulates the received signal from which the T-DMB signal has been removed, that is, the LP signal.

Next, the frequency deinterleaver 720, the demapper 730, the transmission frame demultiplexer 740, the time deinterleaver 750, and the turbo decoder 760 other than the LP demodulator 710 are T-DMB in the received signal. Since there is no direct connection with the present invention for canceling the signal, the detailed description is omitted.

Next, the interference cancellation apparatus 600 according to an embodiment of the present invention will be described in detail with reference to FIG. 3.

3 is a block diagram showing a configuration of an interference cancellation apparatus at a receiving end of an AT-DMB system according to an embodiment of the present invention. 4 is a diagram illustrating a channel impulse response according to an embodiment of the present invention.

First, the interference cancellation apparatus 600 according to the embodiment of the present invention is described as including the HP modulator 610 and the interference canceller 620, but is not limited thereto.

As shown in FIG. 3, the interference canceling unit 620 includes a buffer 621, a channel estimator 622, a smoothing filter 623, a transducer 624, and a selector 625. ) And an OFDM signal generator 626.

The buffer 621 performs the demodulation of the output signal of the OFDM demodulator 400, that is, the OFDM demodulated while the output signal of the OFDM demodulator 400 is delayed while passing through the HP data processor 500 and the HP modulator 610. Save the received signal.

The channel estimator 622 estimates the channel distortion by dividing the output signal of the OFDM demodulator 400 by the output signal of the HP modulator 610. Here, the output signal of the OFDM demodulator 400 is a hierarchically modulated signal, and the output signal of the HP modulator 610 is a hierarchically unmodulated signal. Therefore, the output of channel estimator 622 contains the error of the LP signal plus for hierarchical modulation. Here, the error is a random error.

The filter 623 filters the channel distortion estimated by the channel estimator 622 to remove the error of the LP signal, that is, outputs the channel distortion of the frequency domain.

The converter 624 obtains a channel impulse response of the time domain by performing inverse fast fourier tramsform (IFFT) on the channel distortion of the frequency domain. Here, since the hierarchically modulated T-DMB is operated by local limited broadcasting and the T-DMB is global broadcast, the hierarchically modulated T-DMB signal is received in time before the T-DMB signal. Referring to FIG. 4, the hierarchically modulated T-DMB signal and the T-DMB signal may be distinguished in time.

Transducer 624 then measures the time delay and magnitude of the T-DMB signal based on the channel impulse response.

The selector 625 selects and distinguishes the T-DMB signal from the received signal based on the measured time delay and the magnitude of the T-DMB signal.

The signal generator 626 generates a T-DMB signal, that is, an interference signal having a time delay and magnitude of the measured T-DMB signal, and subtracts the interference signal generated from the output signal of the OFDM demodulator 400. Signal generator 626 then obtains a signal from which the interference signal has been removed from the received signal.

Then, the interference elimination apparatus 600 according to the embodiment of the present invention may improve the reception performance of the AT-DMB receiver by removing the interference signal from the received signal.

Next, an interference cancellation method according to an embodiment of the present invention will be described in detail with reference to FIG. 5.

5 is a flowchart illustrating a method of removing an interference signal at a receiving end of an AT-DMB system according to an embodiment of the present invention.

First, a transmitting end of an AT-DMB system transmits a hierarchically modulated broadcast signal, that is, a received signal, to a receiving end of an AT-DMB system. Here, the receiving end of the AT-DMB system includes an OFDM demodulator 400, an HP data processing apparatus 500, an interference cancellation apparatus 600, and an LP data processing apparatus 700.

The OFDM demodulator 400 OFDM demodulates the hierarchically modulated broadcast signal, that is, the received signal (S501). Here, the received signal is a signal generated by OFDM modulating the differentially phased HP signal and the interleaved LP signal at the transmitting end of the AT-DMB system.

The HP data processing apparatus 500 demodulates the HP signal to generate HP data (S502).

The interference elimination apparatus 600 modulates the HP data into a T-DMB signal (S503). In addition, the interference cancellation apparatus 600 stores the demodulated received signal while modulating the HP data into the T-DMB signal (S504).

The interference cancellation apparatus 600 estimates the channel distortion of the output signal of the OFDM demodulator 400, that is, the hierarchically modulated signal, using the T-DMB signal, that is, the hierarchical unmodulated signal (S505). In this case, the estimation result includes random errors as much as the LP signals added for hierarchical modulation.

The interference elimination apparatus 600 filters the estimated channel distortion to remove the error of the LP signal, that is, generates the channel distortion of the frequency domain (S506).

The interference cancellation apparatus 600 obtains the time-domain channel impulse response by performing inverse fast Fourier transform on the channel distortion of the frequency domain (S507).

Next, the interference cancellation apparatus 600 measures the time delay and the magnitude of the T-DMB signal based on the channel impulse response (S508).

The interference elimination apparatus 600 selects and distinguishes the T-DMB signal from the received signal based on the measured time delay and the magnitude of the T-DMB signal (S509). In addition, the interference cancellation apparatus 600 generates a T-DMB signal, that is, an interference signal having a time delay and a magnitude of the measured T-DMB signal (S510).

The interference elimination apparatus 600 removes the interference signal from the output signal of the OFDM demodulator 400, that is, the received signal (S511).

Thus, the interference cancellation method according to an embodiment of the present invention removes the T-DMB signal acting as an interference signal source at the receiving end of the AT-DMB system to reduce the reception performance of the layer-modulated T-DMB. Receive performance can be improved.

The embodiments of the present invention described above are not only implemented by the apparatus and method but may be implemented through a program for realizing the function corresponding to the configuration of the embodiment of the present invention or a recording medium on which the program is recorded, The embodiments can be easily implemented by those skilled in the art from the description of the embodiments described above.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, It belongs to the scope of right.

Claims (10)

In a method for removing interference in a broadcast system to which a hierarchical modulation technique is applied,
Demodulating a hierarchical modulated signal comprising a service provision signal and a signal newly added to the service provision signal;
Demodulating the service provision signal to generate service provision data;
Modulating the service provision data into a specific signal, and
Removing an interference signal corresponding to the specific signal from a demodulated hierarchical modulated signal;
/ RTI > The method of claim 1,
The removing step
Obtaining a channel impulse response using the specific signal;
Generating the interference signal based on the channel impulse response
/ RTI > 3. The method of claim 2,
Obtaining the channel impulse response
Estimating channel distortion of the demodulated hierarchical modulated signal;
Filtering the channel distortion to remove the error as much as the newly added signal to output the channel distortion in the frequency domain, and
Transforming the channel distortion of the frequency domain to obtain a channel impulse response of the time domain
/ RTI > 3. The method of claim 2,
Generating the interference signal
Measuring a time delay and magnitude of the specific signal based on the channel impulse response;
Discriminating the specific signal from the demodulated hierarchical modulated signal based on the time delay and the magnitude of the specific signal, and
Generating the interference signal having a time delay and a magnitude of the specific signal
/ RTI > The method of claim 1,
The demodulating step
And demodulating the demodulated layer modulated signal while demodulating the service providing data. The method of claim 1,
And the specific signal is a terrestrial digital multimedia broadcasting signal. An apparatus for removing interference in a broadcasting system to which a hierarchical modulation technique is applied,
A demodulator for demodulating a hierarchical modulated signal including a service provision signal and a signal newly added to the service provision signal;
A data processor for demodulating the service provision signal to generate service provision data;
A modulator for modulating the service providing data into a specific signal, and
An interference canceller for removing an interference signal corresponding to the specific signal from the demodulated hierarchical modulated signal
. The method of claim 7, wherein
The interference canceling unit
A channel estimator for estimating channel distortion of the hierarchical modulated signal;
A filter for filtering the channel distortion to remove the error of the newly added signal and outputting the channel distortion in the frequency domain;
A transformer for converting the channel distortion of the frequency domain to obtain a channel impulse response of the time domain, and measuring a time delay and magnitude of the specific signal based on the channel impulse response;
A selector for distinguishing the specific signal from the demodulated hierarchical modulated signal based on a time delay and a magnitude of the specific signal, and
A generator for generating the interference signal having a time delay and a magnitude of the specific signal
. 9. The method of claim 8,
The interference canceling unit
And demodulating the demodulated layer modulated signal while demodulating the service providing data. The method of claim 7, wherein
And said specific signal is a terrestrial digital multimedia broadcasting signal.

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