EP2283651A1

EP2283651A1 - Method and device for transmitting and receiving digital multimedia broadcast signals

Info

Publication number: EP2283651A1
Application number: EP08874406A
Authority: EP
Inventors: Jong Soo Lim; Young Su Kim; Kyu Tae Yang; Jae Hwui Bae; Byung Jun Bae; Kwang-Yong Kim; Joung Il Yun; Seomee Choi; Gwang Soon Lee; Ji Bong Lee; Soo In Lee; Seung Ku Hwang; Chie Teuk Ahn
Original assignee: Electronics and Telecommunications Research Institute ETRI
Current assignee: Electronics and Telecommunications Research Institute ETRI
Priority date: 2008-05-23
Filing date: 2008-11-26
Publication date: 2011-02-16
Also published as: KR100964382B1; EP2283651A4; WO2009142373A1; KR20090122096A

Abstract

The present invention relates to a multimedia broadcast signal transmitting/receiving method, and it generates a pilot signal by mapping transmission information on an orthogonal code, disperses the pilot signal in the frequency domain, modulates the dispersed pilot signal, and transmits the modulated pilot signal.

Description

METHOD AND DEVICE FOR TRANSMITTING AND RECEIVING DIGITAL MULTIMEDIA BROADCAST SIGNALS

Technical Field

[1] The present invention relates to a multimedia broadcast signal transmitter/receiver, and particularly, it relates to a digital multimedia broadcast signal transmitter/receiver for increasing a data rate by loading information on a pilot signal and transmitting the same.

[2] This work was supported by the IT R&D program of MIC/IITA [2006-S-017-03,

Advanced Technology Development for Terrestrial Digital Multimedia Broadcasting] Background Art

[3] A conventional multimedia broadcast signal transmitting device will now be described with reference to FIG. 1 and FIG. 2. FIG. 1 shows a schematic diagram of a conventional multimedia broadcast signal transmitting device.

[4] As shown in FIG. 1, the conventional multimedia broadcast signal transmitting device includes a Motion Picture Experts Group (MPEG) 4 video encoder 110, an MPEG4 audio encoder 120, an MPEG4 system encoder 130, an MPEG2 transport stream (TS) multiplexer 140, a Reed-Solomon (RS) encoder 150, a convolutional in- terleaver 160, and a digital audio broadcasting (DAB) transmitter 170.

[5] The MPEG4 video encoder 110 and the MPEG4 audio encoder 120 encodes a multimedia source, and the MPEG4 system encoder 130 objects and synchronizes a media stream. The MPEG2 TS multiplexer 140 multiplexes the media stream, and the RS encoder 150 performs an additional error correction encoding process. The convolutional interleaver 160 eliminates a temporal correlation between adjacent bytes in a data stream, and the DAB transmitter 170 receives a stream from the convolutional interleaver 160 through a stream mode channel, transforms it into final digital broadcasting signals, and outputs them.

[6] The DAB transmitter 170 will now be described in detail by exemplifying a Eureka-

147 DAB transmitting device that is a European digital audio broadcasting system. FIG. 2 shows a schematic diagram of a DAB transmitter in the Eureka- 147 DAB system.

[7] As shown in FIG. 2, the DAB transmitter 170 includes an energy dispersal scrambler

171, a convolutional encoder 172, a time interleaver 173, a symbol mapper 174, a frequency interleaver 175, a differential modulator 176, an inverse fast Fourier transform (IFFT) unit 177, and a guard interval inserter 178.

[8] The energy dispersal scrambler 171 energy disperses the audio data stream input to the DAB transmitter 170 or a radio frequency (RF) transmission signal of a general data stream, and the convolutional encoder 172 convolution encodes the audio data stream or the general data stream with different coding rates according to an unequal error protection (UEP) profile or an equal error protection (EEP) profile.

[9] The time interleaver 173 time interleaves sixteen logic frame intervals. Since the logic frames respectively have information of a 24ms interval in the time domain, a 384ms total interleaving depth is given. The symbol mapper 174 configures a synchronization channel, a fast information channel (FIC), and a main service channel (MSC) for valid data transmission, and performs a quadrature phase shift keying (QPSK) symbol mapping process in order to configure a 24ms-digital audio broadcasting (DAB) transmission frame.

[10] The frequency interleaver 175 applies frequency interleaving in order to minimize an influence on frequency selective fading.

[11] The differential modulator 176 generates a phase reference signal to locate the same at the second symbol of the transmission frame, and differentially modulates an orthogonal frequency division multiplexing (OFDM) symbol configuring an FIC and an MSC. The IFFT unit 177 performs an IFFT on respective OFDM symbols configuring a transmission frame into signals in the time domain, and the guard interval inserter 178 inserts data that correspond to 1/4 of the latter part of the valid symbol interval before the valid symbol in order to eliminate inter-symbol interference (ISI).

[12] The conventional multimedia broadcast signal transmitting device has an available data rate of 1.152 Mbps when the convolutional coding scheme having the coding rate of 1/2 is applied, and it has an available data rate per service of 576 kbps when two video services are applied to one channel.

[13] Accordingly, the conventional multimedia broadcast signal transmitting device has a limit in providing a high quality service even when applying a high-efficiency source encoding process (776 kbps).

[14] The conventional multimedia broadcast signal transmitting device cannot guarantee receiving performance under a high-speed movement environment since the phase reference symbol (PRS) used for differential modulation is the only one as a pilot signal available for channel estimation.

[15] Further, since it is required to use a predefined signal for the pilot signal used for channel estimation in the conventional digital multimedia broadcast signal transmitting device, the data rate is reduced by the rate of inserting the pilot signal.

[16] The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art. Disclosure of Invention

Technical Problem

[17] The present invention has been made in an effort to provide a digital multimedia broadcast signal transmitting/receiving device for guaranteeing excellent receiving performance under the fast movement environment and improving the data rate. Technical Solution

[18] An exemplary embodiment of the present invention provides a method for transmitting digital multimedia broadcast signals including: generating a pilot signal by mapping transmission information on an orthogonal code; dispersing the pilot signal in the frequency domain; and modulating and transmitting the dispersed pilot signal.

[19] Another embodiment of the present invention provides a device for transmitting digital multimedia broadcast signals including: a pilot signal generator for generating a pilot signal by mapping transmission information on an orthogonal code; a disperser for dispersing the pilot signal in the frequency domain; and a modulator for modulating the dispersed pilot signal.

[20] Yet another embodiment of the present invention provides a method for receiving digital multimedia broadcast signals including: demodulating a received signal; finding a correlation between a signal of a subcarrier into which a pilot signal is inserted from among the demodulated received signal and a plurality of orthogonal codes; and determining the orthogonal code having the greatest correlation from among the plurality of orthogonal codes as a pilot signal, wherein the pilot signal included by the received signal is generated by mapping transmission information on an orthogonal code.

[21] Yet another embodiment of the present invention provides a device for receiving digital multimedia broadcast signals including: a demodulator for demodulating a received signal; and a pilot signal determiner for determining a pilot signal by using the demodulated received signal and extracting transmission information loaded on the pilot signal by using the pilot signal, wherein the pilot signal is generated by mapping transmission information on an orthogonal code.

Advantageous Effects

[22] According to the present invention, it is possible to provide a high quality service by applying an OFDM-CDMA transmission method to the digital multimedia broadcast system, and to increase the data rate by loading information on the pilot signal and transmitting the same. Brief Description of the Drawings

[23] FIG. 1 shows a schematic diagram of a conventional multimedia broadcast signal transmitting device.

[24] FIG. 2 shows a schematic diagram of a DAB transmitter of the Eureka- 147 DAB system. [25] FIG. 3 shows a schematic diagram of a digital multimedia broadcast signal transmitting device according to an exemplary embodiment of the present invention. [26] FIG. 4 shows a schematic diagram of a transmitting data processor.

[27] FIG. 5 shows a schematic diagram of a pilot signal generator.

[28] FIG. 6 shows a flowchart of a digital multimedia broadcast signal transmitting method according to an exemplary embodiment of the present invention. [29] FIG. 7 shows a method for mapping 2-bit information on the Walsh code.

[30] FIG. 8 shows a method for inserting a pilot signal into a subcarrier of an OFDM symbol when the information bit to be transmitted is given as "10". [31] FIG. 9 shows a schematic diagram of a first disperser and a second disperser.

[32] FIG. 10 shows a format of a dispersed pilot signal.

[33] FIG. 11 shows a PAPR distribution when the first disperser 303 and the second disperser 304 are not applied. [34] FIG. 12 shows a PAPR distribution when the first disperser 303 and the second disperser 304 are applied. [35] FIG. 13 shows a PAPR distribution by the product of a dispersed signal and an energy dispersal code. [36] FIG. 14 shows a schematic diagram of a digital multimedia broadcast signal receiving device according to an exemplary embodiment of the present invention. [37] FIG. 15 shows a schematic diagram of a pilot signal determiner.

[38] FIG. 16 shows a flowchart of a digital multimedia broadcast signal receiving method according to an exemplary embodiment of the present invention. [39] FIG. 17 shows a schematic diagram of the first inverse disperser 706 and the second inverse disperser 707.

[40] FIG. 18 shows a process for determining a pilot signal from a received signal.

[41] FIG. 19 shows a method for a demapper to extract transmission information by demapping a pilot signal. [42] FIG. 20 shows a bit error rate (BER) of a pilot signal according to a signal-to-noise rate (SNR) when a multimedia transmitting/receiving method according to an exemplary embodiment of the present invention is applied.

Mode for the Invention [43] In the following detailed description, only certain exemplary embodiments of the present invention have been shown and described, simply by way of illustration. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification.

[44] Throughout the specification, unless explicitly described to the contrary, the word

"comprise" and variations such as "comprises" or "comprising" will be understood to imply the inclusion of stated elements but not the exclusion of any other elements. Also, the terms of a unit, a device, and a module in the present specification represent a unit for processing a predetermined function or operation, which can be realized by hardware, software, or combination of hardware and software.

[45] A digital multimedia broadcast signal transmitting device according to an exemplary embodiment of the present invention will now be described with reference to FIG. 3 to FIG. 5. FIG. 3 shows a schematic diagram of a digital multimedia broadcast signal transmitting device according to an exemplary embodiment of the present invention.

[46] As shown in FIG. 3, the digital multimedia broadcast signal transmitting device includes a transmitting data processor 301, a pilot signal generator 302, a first disperser 303, a second disperser 304, a summation unit 305, an energy dispersal code generator 306, a first product unit 307, an OFDM modulator 308, a cover code generator 309, and a second product unit 310.

[47] The transmitting data processor 301 encodes the input multimedia signal with one or more coding schemes, interleaves it, symbol maps it, and outputs it to the first disperser 303.

[48] The transmitting data processor 301 will be described with reference to FIG. 4. FIG.

4 shows a schematic diagram of a transmitting data processor.

[49] As shown in FIG. 4, the transmitting data processor 301 includes an energy dispersal scrambler 410, a channel encoder 420, an interleaver 430, and a symbol mapper 440.

[50] The energy dispersal scrambler 410 energy disperses the input multimedia signal.

Energy dispersal can be performed by using various dispersal polynomials.

[51] The channel encoder 420 channel encodes the energy dispersed multimedia signal so as to have a robust error correction function for a radio transmission channel. The channel encoding method includes RS coding, convolutional encoding, low density parity check (LDPC) coding, turbo encoding, and concatenated coding concatenating the above-noted coding. In this instance, the rate compatible punctured code (RCPC) available for varying a channel encoding or a structure for changing the encoding rate of the channel code can be used.

[52] The interleaver 430 interleaves a multimedia signal so as to disperse an error of fading of a radio transmission channel. In this instance, it is possible to use various combinations of interleaving methods in the time and frequency directions.

[53] The symbol mapper 440 allocates a data bit of a multimedia signal to the transmission symbol. The symbol mapper 440 maps the data bit on a point in a signal array according to a modulation method such as the quadrature phase shift keying (QPSK), M-PSK, or M-quadrature amplitude modulation (QAM).

[54] The pilot signal generator 302 performs a basic function of the pilot signal such as channel estimation and simultaneously generates a pilot signal for transmitting various kinds of information.

[55] The pilot signal generator 302 generates not a predefined pilot signal but a data signal in the format of the pilot signal and applies various coding methods and modulation methods in order for the receiver to accurately demodulate the pilot signal. The modulation methods include the binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), M-PSK, and M-QAM, and the coding methods include the Read-Solomon code, convolutional code, turbo code, and LDPC.

[56] The pilot signal generator 302 will now be described in detail with reference to FIG.

5. FIG. 5 shows a schematic diagram of a pilot signal generator.

[57] As shown in FIG. 5, the pilot signal generator 302 includes an input unit 510, a

Walsh code mapper 520, and an output unit 530.

[58] The input unit 510 receives information to be transmitted through the pilot signal, and the Walsh code mapper 520 generates a pilot signal by mapping the information on the Walsh code. The output unit 530 outputs the pilot signal generated by the Walsh code mapper 520. The information to be transmitted through the pilot signal includes various types of information including a transmission parameter used for demodulating the received signal by the receiving device, and disaster broadcasting.

[59] The first disperser 303 and the second disperser 304 disperse outputs of the transmitting data processor 301 and the pilot signal generator 302 in the frequency domain.

[60] Here, the first disperser 303 and the second disperser 304 use orthogonal codes such as the Walsh codes used by the IS95 system and the CDMA2000 system or the orthogonal variable spreading factor (OVSF) codes used by the WCDMA system as dispersal codes.

[61] The summation unit 305 summates an output of the first disperser 303 and an output of the second disperser 304 to output a dispersed signal in the frequency domain.

[62] The energy dispersal code generator 306 generates an energy dispersal code for solving the problem in which the peak-to-average power ratio (PAPR) of an output signal of the OFDM modulator 308 is increased as a pilot signal is inserted. Sequences having a random characteristic such as the PN sequence and the scrambling sequence can be used as the energy dispersal code.

[63] The PAPR's of the output signals of the OFDM modulator 308 are varied depending on the sequence used as the energy dispersal code, and the usage of a PN sequence has the best PAPR characteristic. In the case of using the PN sequence, it is possible to use a PN sequence having a period that is different from the number of subcarriers of the OFDM modulator 308.

[64] The first product unit 307 multiplies an output of the summation unit 305 by an energy dispersal code generated by the energy dispersal code generator 306 to output a signal for reducing the PAPR.

[65] The OFDM modulator 308 OFDM modulates the output of the first product unit 307.

[66] The cover code generator 309 generates a cover code for identifying a cell and a sector identified by the base station and the repeater. The PN sequence and the scrambling sequence can be used for the cover code.

[67] The second product unit 310 multiplies an output of the OFDM modulator 308 by the cover code generated by the cover code generator 309 to output a signal for identifying a cell and a sector, and a transmitting antenna transmits the signal output by the second product unit 310.

[68] A method for transmitting a digital multimedia broadcast signal according to an exemplary embodiment of the present invention will now be described with reference to FIG. 6 to FIG. 13. FIG. 6 shows a flowchart of a digital multimedia broadcast signal transmitting method according to an exemplary embodiment of the present invention. It will be described in the exemplary embodiment of the present invention that a pilot signal is included in each group of 8 subcarriers in the frequency domain and 2-bit information is loaded on one OFDM symbol and is transmitted by using a pilot signal, and the embodiment of the present invention is not limited thereto.

[69] The pilot signal generator 302 maps transmission information on the orthogonal code to generate a pilot signal (S610). The case of using the Walsh code as the orthogonal code will be described in the exemplary embodiment of the present invention. FIG. 7 shows a method for mapping 2-bit information on the Walsh code. Referring to FIG. 7, W_n is an orthogonal Walsh code. The pilot signal generator 302 maps 2-bit information on the orthogonal Walsh code. Therefore, when the receiving device determines the pilot signal and extracts information included in the pilot signal, accuracy is increased and realization becomes easier.

[70] The transmitting device inserts the generated pilot signal in the corresponding subcarrier of the OFDM symbol (S620). FIG. 8 shows a method for inserting a pilot signal into a subcarrier of an OFDM symbol when the information bit to be transmitted is given as "10". As shown in FIG. 8, the transmitting device increases accuracy by repeatedly inserting the Walsh code into the subcarrier into which the pilot signal is inserted when the receiving device determines the pilot signal and extracts information included in the pilot signal. For example, when the number of subcarriers is given as 1024, the same Walsh code is repeatedly inserted 32 times.

[71] The second disperser 304 disperses the pilot signal into the frequency domain (S630).

[72] FIG. 9 shows a schematic diagram of the first disperser and the second disperser. In

FIG. 9, M corresponds to the length of the Walsh code, and W_n represents M orthogonal Walsh codes.

[73] As shown in FIG. 9, the first disperser 303 and the second disperser 304 are not divided, but are used to use part of the Walsh code to disperse the pilot signal in one disperser and use the other Walsh code to disperse the multimedia signal. That is, the Walsh code is respectively multiplied to the pilot signal and multimedia signal, which is then summated by the summation unit 305 to acquire a dispersed signal in the frequency domain.

[74] FIG. 10 shows a format of a dispersed pilot signal. As shown in FIG. 10, the pilot signal is dispersed by the second disperser 304 and is then included in the eight adjacent subcarriers.

[75] That is, the pilot signal is included in the corresponding subcarrier and is then transmitted in the existing OFDM transmission system such as the digital video broadcasting terrestrial (DVB-T), digital video broadcasting for handheld (DVB-H), and integrated service digital broadcasting terrestrial (ISDB-T) as shown in FIG. 8, and the pilot signal can be dispersedly included in the entire subcarriers and be transmitted in the OFDM-CDMA transmission system.

[76] The transmitting device multiplies a dispersed signal by an energy dispersal code

(S640).

[77] The PAPR is increased as the multimedia signal and the pilot signal are dispersed in the frequency domain, and the PAPR can be reduced by multiplying the dispersed signal by the energy dispersal code.

[78] FIG. 11 shows a PAPR distribution when the first disperser 303 and the second disperser 304 are not applied, finding a PAPR for each OFDM symbol from among 1000 OFDM symbols and displaying the distribution. In FIG. 11, when the first disperser 303 and the second disperser 304 are not applied, the average of the PAPR is given as 9dB and the peak of the PAPR is given as 11.5 dB.

[79] FIG. 12 shows a PAPR distribution when the first disperser 303 and the second disperser 304 are applied. Referring to FIG. 12, when the first disperser 303 and the second disperser 304 are applied, the PAPR is increased and the peak of the PAPR is increased by 6 dB compared to the case in which the first disperser 303 and the second disperser 304 are not applied.

[80] FIG. 13 shows a PAPR distribution by the product of a dispersed signal and an energy dispersal code. In this instance, the PN sequence with the period of 32,768 is used for the energy dispersal code.

[81] Referring to FIG. 13, when the dispersed signal is multiplied by the energy dispersal code, the PAPR is reduced by a similar degree to the case in which the first disperser 303 and the second disperser 304 are not applied.

[82] Therefore, the PAPR is increased when the first disperser 303 and the second disperser 304 are applied to the OFDM-CDMA broadcasting system, and the PAPR can be reduced by applying the energy dispersal code generator 306 and the first product unit 307.

[83] The transmitting device OFDM modulates the energy dispersal code multiplied dispersed signal (S650), multiplies it by a cover code, and transmits a resultant signal (S660).

[84] A digital multimedia broadcast signal receiving device and method according to an exemplary embodiment of the present invention will now be described. FIG. 14 shows a schematic diagram of a digital multimedia broadcast signal receiving device according to an exemplary embodiment of the present invention.

[85] As shown in FIG. 14, the digital multimedia broadcast signal receiving device includes an uncover code generator 701, a first product unit 702, an OFDM demodulator 703, an energy inverse dispersal code generator 704, a second product unit 705, a first inverse disperser 706, a second inverse disperser 707, a pilot signal determiner 708, a channel estimator 709, an equalizer 710, and a received data processor 711.

[86] The uncover code generator 701 generates an uncover code for uncovering a received signal corresponding to the cover code multiplied to the transmission signal of the transmitting device. The uncover code corresponds to a conjugate of the cover code generated by the cover code generator 309.

[87] The first product unit 702 multiplies the received signal by an uncover code generated by the uncover code generator 701 to output an uncovered signal.

[88] The OFDM demodulator 703 OFDM demodulates the output of the first product unit

702 and outputs a resultant signal.

[89] The energy inverse dispersal code generator 704 generates an energy inverse dispersal code for inversely dispersing the received signal corresponding to the energy dispersal code multiplied to the transmission signal of the transmitting device. The energy inverse dispersal code corresponds to a conjugate of the energy dispersal code generated by the energy dispersal code generator 306.

[90] The second product unit 705 multiplies the signal output by the OFDM demodulator

703 by the code generated by the energy inverse dispersal code generator 704 to output a resultant signal.

[91] The first inverse disperser 706 and the second inverse disperser 707 inversely disperse the output signal of the second product unit 705. [92] The pilot signal determiner 708 determines a pilot signal from the output of the second inverse disperser 707, and extracts transmission information loaded on the pilot signal based on the determined pilot signal. The pilot signal determiner 708 decodes and demodulates the pilot signal that is distorted on the transmission channel by using a decoding method and a demodulation method corresponding to the coding method and the demodulation method used by the pilot signal generator 302 to determine and output an accurate pilot signal.

[93] The pilot signal determiner 708 will now be described in detail with reference to FIG.

15. FIG. 15 shows a schematic diagram of a pilot signal determiner.

[94] As shown FIG. 15, the pilot signal determiner 708 includes an input unit 810, a correlator 820, an integrator and determiner 830, an output unit 840, and a demapper 850.

[95] The input unit 810 receives a pilot signal from the second inverse disperser 707, the correlator 820 finds a correlation between the pilot signal provided by the input unit 810 and the Walsh codes, the integrator and determiner 830 integrates the correlation found by the correlator 820 by the number of repeated insertions of the pilot signal into a single OFDM symbol to determine the Walsh code with the greatest correlation to be a pilot signal, and the output unit 840 repeats the pilot signal determined by the integrator and determiner 830 by the number of repeated insertions of the pilot signal into one OFDM symbol and outputs a resultant signal.

[96] The demapper 850 demaps the Walsh code type pilot signal determined by the integrator and determiner 830 to extract and output transmission information that is loaded on the pilot signal and is transmitted.

[97] The channel estimator 709 estimates a transmission channel by using the pilot signal determined by the pilot signal determiner 708 and the distorted pilot signal output by the second inverse disperser 707.

[98] The equalizer 710 equalizes and outputs the output signal of the first inverse disperser 706 by using the transmission channel estimated by the channel estimator 709.

[99] The received data processor 711 outputs a multimedia signal by symbol demapping, deinterleaving, channel decoding, and descrambling the output signal of the equalizer 710.

[100] A digital multimedia broadcast signal receiving method according to an exemplary embodiment of the present invention will now be described. FIG. 16 shows a flowchart of a digital multimedia broadcast signal receiving method according to an exemplary embodiment of the present invention.

[101] As shown in FIG. 16, the receiving device multiplies the received signal by the uncover code (S910), OFDM demodulates the uncovered received signal (S920), and multiplies the OFDM demodulated received signal by the energy inverse dispersal code (S930).

[102] The receiving device inversely disperses the received signal (S940). FIG. 17 shows a schematic diagram of the first inverse disperser 706 and the second inverse disperser 707. As shown in FIG. 17, the first inverse disperser 706 and the second inverse disperser 707 are not divided, part of the Walsh code is used to inversely disperse the part that corresponds to the pilot signal from among the received signals within one inverse disperser, and the other Walsh code is used to inversely disperse the part that corresponds to the multimedia signal from among the received signals.

[103] The receiving device finds a correlation between the subcarrier signal into which the pilot signal is inserted from among the received signals and the Walsh code (S950), and integrates the correlation (S960) to determine the pilot signal (S970). FIG. 18 shows a process for determining a pilot signal from a received signal.

[104] As shown in FIG. 18, the correlator 820 finds a correlation between respective subcarrier signals into which the pilot signal is repeatedly inserted from among the received signal and the Walsh code, integrates a plurality of correlations, and determines the Walsh code having the greatest correlation to be a pilot signal transmitted by the transmitting device.

[105] The receiving device extracts transmission information by demapping the pilot signal (S980). FIG. 19 shows a method for a demapper to extract transmission information by demapping a pilot signal. As shown in FIG. 19, the demapper 850 extracts a transmission parameter that is loaded on the pilot signal and transmitted by the transmitting device or other information by demapping the Walsh code determined to be a pilot signal.

[106] FIG. 20 shows a bit error rate (BER) of a pilot signal according to a signal-to-noise rate (SNR) when a multimedia transmitting/receiving method according to an exemplary embodiment of the present invention is applied.

[107] Here, the channel environment uses the TU6 channel that is mainly used under the movement environment, and the speed of the receiving device is given as 200 km/h.

[108] Referring to FIG. 20, accuracy of determining the pilot signal is excellent in the environment with the SNR of IdB.

[109] The above-described embodiments can be realized through a program for realizing functions corresponding to the configuration of the embodiments or a recording medium for recording the program in addition to through the above-described device and/or method, which is easily realized by a person skilled in the art.

[110] While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Claims

[I] A method for transmitting digital multimedia broadcast signals, comprising: generating a pilot signal by mapping transmission information on an orthogonal code; dispersing the pilot signal in the frequency domain; and modulating and transmitting the dispersed pilot signal. [2] The method of claim 1, wherein the transmission information includes a transmission parameter for demodulating a received signal by a receiving device. [3] The method of claim 1, further including repeatedly inserting the pilot signal into a plurality of subcarriers. [4] The method of claim 1, further including multiplying the dispersed pilot signal by an energy dispersal code having a characteristic of randomness. [5] The method of claim 4, wherein the energy dispersal code is a pseudo random noise (PN) sequence. [6] The method of claim 4, further including multiplying the pilot signal by a cover code for identifying a cell and a sector. [7] A device for transmitting digital multimedia broadcast signals, comprising: a pilot signal generator for generating a pilot signal by mapping transmission information on an orthogonal code; a disperser for dispersing the pilot signal in the frequency domain; and a modulator for modulating the dispersed pilot signal. [8] The device of claim 7, wherein the orthogonal code is a Walsh code. [9] The device of claim 7, further comprising a first multiplier for multiplying the dispersed pilot signal by an energy dispersal code having a characteristic of randomness. [10] The device of claim 9, further comprising a second multiplier for multiplying the pilot signal by a cover code for identifying a cell and a sector.

[I I] A method for receiving digital multimedia broadcast signals, comprising: demodulating a received signal; finding a correlation between a signal of a subcarrier into which a pilot signal is inserted from among the demodulated received signal and a plurality of orthogonal codes; and determining the orthogonal code having the greatest correlation, from among the plurality of orthogonal codes, as a pilot signal, wherein the pilot signal included by the received signal is generated by mapping transmission information on an orthogonal code. [12] The method of claim 11 , wherein the pilot signal included by the received signal is repeatedly inserted into the received signal, the finding of a correlation includes finding a correlation between the respective repeatedly inserted pilot signals and the plurality of orthogonal codes, and the determining includes integrating correlation of the respective repeatedly inserted pilot signals and the plurality of orthogonal codes. [13] The method of claim 11 , further comprising extracting the transmission information by demapping the determined pilot signal. [14] A device for receiving digital multimedia broadcast signals, comprising: a demodulator for demodulating a received signal; and a pilot signal determiner for determining a pilot signal by using the demodulated received signal, and extracting transmission information loaded on the pilot signal by using the pilot signal, wherein the pilot signal is generated by mapping transmission information on an orthogonal code. [15] The device of claim 14, wherein the pilot signal determiner includes: a correlator for finding a correlation between a signal of a subcarrier into which a pilot signal is inserted from among the demodulated received signal and a plurality of orthogonal codes; an integrator and determiner for integrating the correlation, and determining the orthogonal code with the greatest correlation to be a pilot signal; and a demapper for extracting transmission information that is loaded on the pilot signal and transmitted by demapping the determined pilot signal.