KR100662392B1 - Apparatus for receiving broadcast - Google Patents

Abstract

An apparatus for receiving broadcasting is provided to improve a bit error rate of a received signal caused by channel compensation in correspondence with fast channel variation, thereby improving receiving performance. In a broadcasting receiving apparatus for receiving a transmission signal of OFDM(Orthogonal Frequency Division Multiplexing), the apparatus comprises the followings: an equalizer(190) which compensates and outputs a channel of a received signal; and a phase compensator(300) which compensates phase errors of a signal, outputted from the equalizer(190), by using phase errors of TPS(Tandem Packet Switch) data having channel coding information. The transmission signal of the OFDM type uses a PN(Pseudonoise) sequence as a training signal.

Description

Apparatus for receiving broadcast

1 is a configuration diagram showing a brief configuration of a transmission device of the DMB-T

2 is a structural diagram of a frame having a guard interval of 1/9 as an example of a transmission signal frame of a DMB-T;

3 is a block diagram of an embodiment of a broadcast receiving device according to the present invention;

4 is a structural diagram illustrating an embodiment of a phase compensator of a broadcast reception device according to the present invention;

5 is a constellation concept of phase error compensation by a phase compensator in a broadcast receiving apparatus according to the present invention.

<Explanation of symbols in the main part of the drawing>

10: channel encoder 15: TPS generator

20 modulator 30 reverse DFT

40: PN generation unit 50: multiplexer

60: SRRC unit 70: RF transmission unit

110: tuner 120: automatic gain control unit

130: A / D converter 140: phase separator

145: Multiplier 150: Resampler

160: SRRC unit 170: frame synchronization unit

171: PN correlation unit 172: signal acquisition unit

174: signal tracking unit 177: automatic frequency control unit

179: multiplier 180,182: DFT unit

190: equalizer 300: phase compensation unit

301: TPS decoder 305: phase error detector

310: multiplier

The present invention relates to a broadcast receiving apparatus, and more particularly, to a broadcast receiving apparatus capable of channel compensation of a received signal even with a quick channel change.

Recently, Tsinghua University has proposed a new standard for terrestrial digital television (“Terrestrial DTV”) broadcasting to China. The proposal relates to a broadcast standard called Terrestrial Digital Multimedia / Television Broadcasting (DMB-T). In DMB-T, a new modulation scheme called Time Domain Synchronous OFDM (hereinafter referred to as TDS-OFDM) is used.

A signal transmitted after being modulated at the transmitting end of the TDS-OFDM is applied with an Inverse Discrete Fourier Transform (IDFT) as in the cyclic prefix OFDM (CP-OFDM) scheme.

However, a pseudonoise (PN) is inserted in the guard interval instead of CP and used as a training signal.

The above-described method can reduce overhead when transmitting a broadcast signal, improve channel usage efficiency, and improve performance of a synchronizer and a channel estimator of a broadcast signal receiver.

When the transmission signal modulated by the TDS-OFDM method is received, frequency error compensation and sampling error are compensated for, and the received signal is decoded by performing channel compensation on the signal with the error compensated. The equalizer of the receiver performs channel compensation, but if the received signal includes information by fast channel conversion, there is a problem that the bit error rate may be lowered because the phase error is different every frame. .

Accordingly, the channel compensation of the received signal is not sufficient by the channel compensation of the equalizer of the receiver, and in particular, there is a problem in that the reception performance of the received signal is reduced due to a fast channel change.

An object of the present invention for solving the above problems is to provide a broadcast receiving apparatus capable of channel compensation of a received signal even with a fast channel change.

Another object of the present invention is to provide a broadcast receiving apparatus capable of increasing a bit error rate of a received signal according to channel compensation in response to a fast channel change and having good reception performance.

In order to achieve the above object, the present invention provides a broadcast receiving apparatus for receiving a transmission signal of orthogonal frequency division multiplexing (OFDM), comprising: an equalizer for compensating and outputting a channel of a received signal; And a phase compensator for compensating for a phase error of a signal output from the equalizer by using a phase error of transmission information parameter signal (TPS) data having channel encoding information.

In the orthogonal frequency multiplexing transmission signal, a PN (Pseudonoise) sequence is preferably used as a training signal.

The phase compensator comprises: a TPS decoder for decoding the transmission information parameter signal data from a received signal; A phase error detector for detecting a phase error of the equalizer output signal from the output signal of the equalizer and the output signal of the TPS decoder; And a multiplier that multiplies a phase error output by the phase error detector by an output signal of the equalizer to compensate for the residual phase error.

The transmission information mediation signal preferably includes at least one information of a frame group number, a Forward Error Correction (FEC) code error ratio, or a time-deinterleaver mode.

Hereinafter, with reference to the accompanying drawings, preferred embodiments of the present invention that can specifically realize the above object will be described.

1 is a block diagram showing a brief configuration of a transmission apparatus of a DMB-T. Referring to FIG. 1, the operation of the transmitter of the DMB-T will be described.

The channel encoder 10 outputs a bitstream encoded by the channel in order to detect an error at the receiving end.

The TPS generation unit 15 includes a TPS (transmission variable parameter signal) including channel encoding or modulation information such as a frame group number, a forward error correction (FEC) code error ratio, and a time-deinterleaver mode. TPS) generates and outputs the data.

The modulator 20 receives the encoded bit stream and modulates the bit stream by quadrature amplitude modulation (QAM), such as 4-, 16-, or 64-values.

The inverse DFT unit 30 modulates a signal modulated by the OFDM scheme in the frequency domain into an OFDM signal in the time domain. In the DMB-T method, the inverse DFT unit 30 may simultaneously convert a frequency domain signal for 3780 points of transmission data into a time domain signal.

The PN generator 40 generates a PN sequence to be used as a training signal of a broadcast signal to be transmitted.

The multiplexer 50 distributes the generated PN sequence and the OFDM signal converted by the inverse DFT unit 30 in a time domain, and multiplexes the same.

The SRRC unit 60 outputs the bandwidth of the multiplexed DMB-T signal by limiting the bandwidth. In general, the roll-off factor α used for the bandwidth limit is 0.05.

The RF transmitter 70 up-converts the output signal with the limited bandwidth to an RF (Radio Frequency) transmission band of a predetermined frequency fc to transmit a broadcast signal.

FIG. 2 shows a structure of a frame in which a guard interval is 1/9 of a frame of a signal transmitted by the DMB-T transmitting apparatus of FIG. 1. A transmission frame structure having a guard interval of 1/9 will be described with reference to FIG. 2.

The frame consists of frame sync and frame body.

The frame body is a place where data to be transmitted is a DFT block to which a Discrete Fourier Transform (DFT) is applied, and the DFT block generally includes 3780 stream data.

The frame sync consists of a PN sequence, and the PN sequence used for the frame sync may use a sequence having an order of 8 (m = 8). When m = 8, 255 different sequences can be generated. The sequences can be extended to preambles and postambles for use in guard intervals.

Accordingly, the preamble and the postamble may be a repetition period of the PN sequence for cyclic extension (cyclic extension) of the PN sequence.

Of the 255 PN sequences of the frame sync, the first 115 PN sequences of the PN sequence are added as a postamble to the end of the 255 PN sequences, and the last 50 PNs of the PN sequence are preambles of the 255 PN sequences. It can be added to the front and expanded.

The polynomial of the PN sequence is P (x) = x ⁸ + x ⁶ + x ⁵ + x + 1, and the generated phase varies from 0 to 254 according to the initial state of the PN sequence.

When the guard interval is 1/9, the preamble and the postamble may be added to the 255 PN sequences before and after to configure a frame sink including 420 data. In other words, 420 data, which is 1/9 of 3780 data of the DFT block, may be used for frame sync. One OFDM frame may be composed of a frame sink of 420 data and a frame body of 3780 data.

The structure of the data frame may vary depending on the protection period, and the number of data distributed in each frame may also be distributed differently.

In addition, the protective section may be defined as 1/4 or 1/9, in addition to the 1/6 protective section may be used, and thus, the length of the protective section may be formed differently depending on the standard forming the system.

3 is a block diagram of an embodiment of a broadcast receiving apparatus according to the present invention. An operation of an embodiment of a broadcast reception device according to the present invention will be described with reference to FIG. 3 as follows.

The tuner 110 of the broadcast reception device according to the present invention converts a signal of an RF transmission band into a base band signal and outputs it.

The automatic gain controller (AGC) 120 may output power by normalizing power of the output signal.

The analog to digital converter 130 converts the output signal into an analog signal and outputs the digital signal.

The phase splitter 140 divides an inphase component signal (hereinafter referred to as I signal) and a quadrature component signal (hereinafter referred to as Q signal) from the signal output from the A / D converter 130. Print separately.

The automatic frequency control (FCC) unit 177 compensates for the estimated frequency error of the separated I and Q signals, and the SRRC unit 160 controls the bandwidth of the received signal as in the transmitter. Can act as a filter to limit

The frame synchronization unit may be divided into three parts. First, the AFC unit 177 calculates the frequency error of the received signal as described above, and calculates the product of the received signal and the signal from which the frequency error is calculated through the multiplier 145. The frequency error of the received signal can be compensated for.

The signal acquisition unit 172 synchronizes the PN sequence sent by the transmitter. Finally, the signal tracking unit 174 compensates for the symbol error using the captured PN sequence.

The frame synchronizer of the received signal may use a result of correlation between the received signal and the PN sequence in the PN correlator 171.

Data output as a result of the frame synchronization unit is transformed into the time domain through the FFT (Fast Fourier Transform) process in the DFT unit 180 and 182, and the channel is compensated through the equalizer 190 to the phase compensator 300. Is output.

4 illustrates an embodiment of a phase compensator of a broadcast reception device according to the present invention. Referring to Figure 4 describes the operation of an embodiment of the phase compensation unit according to the present invention.

The equalizer 190 may input the channel-compensated signals X _I and X _Q to the phase error detector 305. The TPS decoder 301 may decode the TPS data among the received signals in the frequency domain. As described above, the TPS data includes information of a frame group number, a Forward Error Correction (FEC) code error ratio, a time-deinterleaver mode, and the like.

Therefore, since the decoded TPS data can be used as a pilot signal in the frequency domain, the phase error can be estimated. Since the pilot signal has a larger power than the general transmission signal, accurate error estimation can be performed by using the decoded TPS data to estimate the phase error.

The phase error detector 305 receives the position of the channel compensated signal output from the equalizer 190 and the position of the TPS data T _I and T _Q output from the TPS decoder 301 and the value at the position. Can be.

The TPS data may be modulated in a predetermined manner, for example, quadrature phase shift keying (QPSK), and have a complex number format divided into an inphase component and a quadrature component. Can be.

The phase error detector 305 may detect phase error of a signal whose channel is compensated by the equalizer 190 using the TPS data. When the outputs of the equalizer 190 and the TPS decoder 301 are complex numbers, the phase errors of the real (I) and imaginary (Q) components of the complex signal are as follows.

Therefore, if the phase error E _I , E _Q calculated by Equation 1 is compensated for the signals X _I , X _Q output from the equalizer 190, the output of the compensated complex signal Y _I , Y _Q ) is as follows.

In Equation 2, Y _I and Y _Q are as follows.

Therefore, in the case of FIG. 4, when the signals X _I and X _Q output from the equalizer 190 are multiplied by the phase error E _I and E _Q in the multiplier 310, the signal compensated for by the channel is equalized. The phase error of may be output as a compensated signal.

5 is a diagram illustrating a concept of phase error compensation by a phase compensator in a broadcast receiving apparatus according to the present invention in a constellation. The concept of compensating for the phase error by the phase compensator of the broadcast reception device according to the present invention will be described with reference to FIG. 5.

In FIG. 5, the transmission signal TPS (T _I , T _Q ) indicates that the TPS data should be located in the constellation diagram. The signals X _I and X _Q from which the TPS data are output through the equalizer may include errors in in-phase signal components and quadrature components, respectively. The error E _I and E _Q for each component of the TPS data T _I and T _Q and the equalizer output signals X _I and X _Q of the TPS data are calculated and the errors E _I and E _Q are calculated. By rotating the equalizer output signal (X _I , X _Q ) corresponding to the TPS data by), original TPS data (T _I , T _Q ) can be obtained.

Therefore, if the phase error is compensated for the signals other than the signals corresponding to the TPS data output from the equalizer as described above, the bit error rate of the signal output from the equalizer can be increased and a more accurate received signal can be obtained. You can get it.

The effects of the broadcast receiving apparatus according to the present invention described above are as follows. According to the broadcast reception device according to the present invention, channel compensation of a received signal is possible even with a fast channel change. In addition, the bit error rate of the received signal according to the channel compensation may be increased in response to the fast channel change, thereby increasing the reception performance.

Claims (4)

In the broadcast receiving apparatus for receiving a transmission signal of an orthogonal frequency division multiplexing (OFDM), An equalizer for compensating and outputting a channel of the received signal; And And a phase compensator for compensating for a phase error of a signal output from the equalizer by using a phase error of transmission information parameter signal (TPS) data having channel encoding information. The method of claim 1, The transmission signal of the orthogonal frequency multiplexing scheme uses a PN (Pseudonoise) sequence as a training signal. The method of claim 1, The phase compensator comprises: a TPS decoder for decoding the transmission information parameter signal data from a received signal; A phase error detector for detecting a phase error of the equalizer output signal from the output signal of the equalizer and the output signal of the TPS decoder; And And a multiplier for compensating for the residual phase error by multiplying the phase error output by the phase error detector to an output signal of the equalizer. The method of claim 1, The transmission information parameter signal includes at least one of information of a frame group number, a Forward Error Correction (FEC) code error ratio, and a time-deinterleaver mode.

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