EP2304949A2

EP2304949A2 - Apparatus for transmitting and receiving digital multimedia broadcasting and method thereof

Info

Publication number: EP2304949A2
Application number: EP09770389A
Authority: EP
Inventors: Jong Soo Lim; Young Su Kim; Kyu Tae Yang; Jae Hwui Bae; Byungjun Bae; Kwang-Yong Kim; Joungil Yun; Seomee Choi; Gwang Soon Lee; Ji Bong Lee; Yun Jeong Song; Soo In Lee; Seungku Hwang; Chieteuk Ahn; Namho Hur
Original assignee: Electronics and Telecommunications Research Institute ETRI
Current assignee: Electronics and Telecommunications Research Institute ETRI
Priority date: 2008-06-24
Filing date: 2009-06-24
Publication date: 2011-04-06
Also published as: KR20100002110A; WO2009157717A3; WO2009157717A2

Abstract

A digital multimedia broadcasting transmitting apparatus includes: a variable spreader (120) that spreads a pilot signal to a frequency domain and outputs a signal having a format where the pilot signal is partially inserted to the entire subcarriers; a modulator (130) that modulates the output of the variable spreader (120); and an antenna (140) that transmits the signal modulated by the modulator (130).

Description

APPARATUS FOR TRANSMITTING AND RECEIVING DIGITAL MULTIMEDIA BROADCASTING AND METHOD THEREOF

The present invention relates to a digital multimedia broadcasting transmitting/receiving method and apparatus.

In a digital multimedia broadcasting system, a transmitting apparatus inserts a pilot signal every constant subcarrier unit within one symbol, and spreads a data signal and the inserted pilot signal to a frequency domain for transmission to a receiving apparatus. In this case, a signal transmitted to the receiving apparatus has a format where the spread pilot signal is inserted to the entire subcarriers.

The receiving apparatus performs inverse spread on the received signal to check a signal value that is distorted while a subcarrier in which a pilot signal is inserted before the spread in the transmitting apparatus is passed through a channel and to check channel information by using the checked signal value. In this case, the checked channel information is information that represents a constant subcarrier unit to which the pilot signal is inserted.

The receiving apparatus equalizes channels by equally applying the checked channel information to a subcarrier unit to which the corresponding subcarrier is included.

However, as the length of a spread code used for spreading the pilot signal in the frequency domain in the transmitting apparatus is increased, the length of an inverse spread code for performing inverse spread in the receiving apparatus is increased so that the complexity in the entire digital multimedia broadcasting system is problematically increased.

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.

The present invention has been made in an effort to provide a digital multimedia broadcasting transmitting/receiving apparatus that can reduce complexity.

According to an exemplary embodiment of the present invention, a digital multimedia broadcasting transmitting apparatus is provided.

The digital multimedia broadcasting transmitting apparatus includes a variable spreader that spreads a pilot signal to a frequency domain and outputs a signal having a format where the pilot signal is partially inserted to the entire subcarriers, a modulator that modulates the output of the variable spreader, and an antenna that transmits the signal modulated by the modulator.

The variable spreader may include a spreader that spreads the pilot signal to the frequency domain and outputs a signal having a format where the pilot signal is inserted to the entire subcarriers and a pre-coder that outputs the signal having the format where the pilot signal is partially inserted to the entire subcarriers by multiplying the signal output from the spreader with an orthogonal code.

According to another exemplary embodiment of the present invention, a digital multimedia broadcasting transmitting method is provided.

A method for a digital multimedia broadcasting transmitting apparatus to transmit a digital multimedia broadcasting signal includes spreading a pilot signal in a frequency domain, and outputting a spread signal having a format where the pilot signal is partially inserted into the entire subcarriers and modulating the spread signal and outputting the modulated signal.

According to another exemplary embodiment of the present invention, a digital multimedia broadcasting receiving apparatus is provided.

The digital multimedia broadcasting receiving apparatus includes a demodulator demodulating a signal received from a digital multimedia transmitting apparatus and outputting a signal having a format where a pilot signal is partially inserted to the entire subcarriers and an inverse spreader performing inverse spread to the output of the demodulator and outputting a signal having a format where the pilot signal is inserted every constant subcarrier unit among the entire subcarriers and a data signal is inserted to the other subcarriers to which the pilot signal is not inserted. A code used in the inverse spreader is an orthogonal code, and a length of the code used in the inverse spreader is less than the constant subcarrier unit and is the same as a unit to which the pilot signal is inserted in the signal output from the demodulator.

According to another exemplary embodiment of the present invention, a digital multimedia broadcasting receiving method is provided.

A method for a digital multimedia broadcasting receiving apparatus to receive a digital multimedia broadcasting signal includes demodulating a signal received from a digital multimedia transmitting apparatus and outputting a signal having a format where a pilot signal is partially inserted to the entire subcarriers and performing inverse spread on the output signal and outputting a signal having a format where the pilot signal is inserted every constant subcarrier unit among the entire subcarriers and a data signal is inserted to the other subcarriers to which the pilot signal is not inserted. A code used in the inverse spread is an orthogonal code, and the length of the code used in the inverse spread is less than that of the constant subcarrier unit.

According to the exemplary embodiments of the present invention, a digital multimedia broadcasting transmitting/receiving apparatus and a method thereof having reduced complexity can be provided.

FIG. 1 is a schematic view of a digital multimedia broadcasting transmitting apparatus according to an exemplary embodiment of the present invention.

FIG. 2 is a schematic view for description of the exemplary embodiment of the present invention.

FIG. 3 is a schematic view of a pilot signal format according to variance of the length of a code used in a pre-coder according to the exemplary embodiment of the present invention.

FIG. 4 is a schematic view of a spreader according to the exemplary embodiment of the present invention.

FIG. 5 is a schematic view of the pre-coder according to the exemplary embodiment of the present invention.

FIG. 6 schematically shows a configuration of the digital multimedia broadcasting transmitting apparatus according to the exemplary embodiment of the present invention.

FIG. 7 is a schematic view for describing operation of an inverse spreader according to the exemplary embodiment of the present invention.

FIG. 8 is a schematic view of a variable spreader according to another exemplary embodiment of the present invention.

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.

In addition, 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. In addition, the terms "-er", "-or", and "module" described in the specification mean units for processing at least one function and operation and can be implemented by hardware components or software components and combinations thereof.

Hereinafter, a digital multimedia broadcasting transmitting/receiving method and an apparatus using the same will be described in further detail with reference to the drawings.

FIG. 1 schematically shows a digital multimedia broadcasting transmitting apparatus according to an exemplary embodiment of the present invention.

Referring to FIG. 1, a digital multimedia broadcasting transmitting apparatus 100 according to the exemplary embodiment of the present invention includes a data processor 110, a variable spreader 120, a modulator 130, and an antenna 140.

The data processor 110 encodes an input data signal based on one or more coding methods, performs interleaving, maps the interleaved signal to a symbol, and outputs the mapped signal to the variable spreader 120.

The variable spreader 120 includes a spreader 121 and a pre-coder 122, and the spreader 121 includes a pilot spreader 11, a data spreader 12, and an adder 13 and spreads a pilot signal and a data signal in a frequency domain.

The pilot spreader 110 spreads a pilot signal used for checking channel information in a receiving apparatus to the frequency domain, and the data spreader 12 spreads an output of the data processor 110 to the frequency domain.

The pilot spreader 110 and the data spreader 12 use orthogonal codes for spread, and the orthogonal codes include, for example, a Walsh code or an orthogonal variable spreading factor (OVSF) code. In addition, the length of the code used for spread may be a subcarrier in which a pilot signal is inserted.

The adder 13 adds outputs of the pilot spreader 110 and the data spreader 12 to output a spread signal in the frequency domain.

The pre-coder 122 multiplies a code used in the spreader 121 or a code having a different length by an output of the spreader 121 and outputs the product. For example, the spreader 121 may spread the pilot and data signals by using a Walsh code of length 8, and the pre-coder 122 may multiply a Walsh code of length 4 to the spread signal and output the product.

In addition, the length of a code used in the pre-coder 122 may be changed according to a channel condition. That is, when the channel condition varies significantly so that the spread is more frequently required, the length of the code used in the pre-coder 122 may be decreased, and when the channel condition varies insignificantly so that the spread is less frequently required, the length of the code used in the pre-coder 122 may be increased.

The modulator 130 modulates the output of the pre-coder 122.

The antenna 140 transmits a signal modulated by the modulator 130.

FIG. 2 is a schematic view for description of the exemplary embodiment of the present invention. In FIG. 2, it is assumed that the pilot signal is inserted into every eighth subcarrier, the spreader 121 uses a code of length 8, and the pre-coder 122 uses a code of length 4.

Referring to FIG. 2, a signal before passing through the spreader 121 has a format where the pilot signal is inserted in every eighth subcarrier unit in one symbol. That is, among eight neighboring subcarriers, a pilot signal is inserted into one subcarrier and a data signal is inserted into the other seven subcarriers.

The spreader 121 spreads the pilot and data signals in the frequency domain, and a signal having passed through the spreader 121 has a format where the same sized (i.e., 1/8 the size of one symbol) pilot signals are inserted to the entire subcarriers.

The pre-coder 122 multiplies the code of length 4 by the signal spread by the spreader 121 and outputs the product, and the signal having passed through the pre-coder 122 has a format where a pilot signal having a half size of one symbol is inserted every four subcarrier units.

The 1/8-sized pilot signal that has been inserted into the entire subcarriers before passing through the pre-coder 122 is increased to 1/2 after passing through the pre-coder 122. That is, the number of subcarriers to which the pilot signal is inserted is decreased, but the size of the pilot signal inserted into the corresponding subcarrier is increased.

Therefore, when the receiving apparatus receives a signal that is modulated after being passed through the pre-coder 122, the receiving apparatus can perform inverse spread by using a code of length 2 so that the amount of calculation required for the inverse spread can be reduced.

The decrease of the calculation amount of the receiving apparatus according to application of the pre-coder 122 will be described with reference to the following equations.

Equation 1 to Equation 3 show eight subcarrier values that vary after the subcarriers pass through the spreader 121 and the pre-coder 122 of FIG. 1. Here, the eight subcarriers neighbor each other in one symbol.

Equation 1 represents a signal that has not yet passed through the spreader 121, and the signal before passing through the spreader 121 has a format where a pilot signal is inserted into the first subcarrier among the eight neighboring subcarriers and data signals are inserted into the other seven subcarriers.

[Equation 1]

Here, denote subcarrier numbers, denotes a pilot signal, and denote data signals.

Equation 2 represents a signal that has passed through the spreader 121, and in this case, the spreader 121 uses the Walsh code of length 8.

[Equation 2]

As shown in Equation 2, the pilot and data signals are spread to the eight neighboring subcarriers.

A general digital multimedia broadcasting transmitting apparatus forms a subcarrier as given in Equation 2, modulates the subcarrier, and transmits the modulated subcarrier. Therefore, in order to inversely spread a signal as given in Equation 2, a transmitting apparatus needs to perform 8×8 multiplications.

Equation 3 shows a signal that has passed through the pre-coder 122 according to the exemplary embodiment of the present invention, and in this case, the pre-coder 122 uses a Walsh code of length 4.

[Equation 3]

As shown in Equation 3, when a signal spread to the entire subcarriers by the spreader 121 is passed through the pre-coder 122, a value of the corresponding subcarrier is determined by a combination of a signal initially inserted to the subcarrier before the spread and a signal inserted into the fourth subcarrier in the subcarrier sequence.

Therefore, the pilot signals that have been spread to the entire subcarriers are inserted only to the subcarrier to which the pilot signal is initially inserted and to the fourth subcarrier in the subcarrier sequence.

In addition, referring to a format of a signal inserted into a subcarrier after passing through the pre-coder 122, subcarriers (e.g., and ) of which values are determined by a combination of the same signals (e.g., p and d₄) are the same as a result obtained by adding multiplication of a Walsh code of length 2 to signals (e.g., p, d₄) that have been initially inserted to the corresponding subcarriers.

Therefore, a receiving apparatus that receives a signal from the transmitting apparatus to which the pre-coder 122 according to the exemplary embodiment of the present invention is applied can perform inverse spread with the Walsh code of length 2 without using a Walsh code of length 8.

That is, a general transmitting apparatus needs to performs 8x8 multiplications for inverse spread, but the receiving apparatus receiving a signal from the transmitting apparatus to which the pre-coder 122 according to the exemplary embodiment of the present invention is applied can perform inverse spread with 2x2x4 multiplications so that a calculation amount for the inverse spread can be reduced.

FIG. 3 is a schematic view of a pilot signal format according to length variation of a code used in the pre-coder 122 according to the exemplary embodiment of the present invention.

Referring to FIG. 3, as the length of a code used in the pre-coder 122 is decreased, the pilot signal is widely spread to the entire subcarriers. Therefore, as the length of the code used in the pre-coder 122 is increased, the calculation amount for performing inverse spread in the receiving apparatus can be reduced.

In addition, when the pre-coder 122 uses a code of length 8, a signal spread in the frequency domain through the spreader 121 is inversely spread while passing through the pre-coder 122 so that the receiving apparatus does not need to perform inverse spread.

When the pre-coder 122 uses a code of length 1, a signal that is the same as the signal spread in the frequency domain before passing through the pre-coder 122 is output, and therefore the calculation amount of the receiving apparatus is not reduced.

FIG. 4 schematically shows the spreader 121 according to the exemplary embodiment of the present invention, and FIG. 5 schematically shows the pre-coder 122 according to the exemplary embodiment of the present invention.

In FIG. 4, a Walsh code is exemplarily used as a spread code in the spreader 121.

In FIG. 4, M denotes the length of a Walsh code, and may correspond to a pilot signal insertion period, that is, a subcarrier unit to which a pilot signal is spread. In addition, W₀, W-₁, ... and W_M-1 are Walsh codes that are orthogonal to each other, and M Walsh codes are provided.

The spreader 121 includes a pilot spreader 11, a data spreader 12, and an adder 13. The pilot spreader 110 and the data spreader 12 are not separated so that they are distinguished when using partial Walsh codes to spread a pilot signal in the same spreader 121. That is, a signal spread in the frequency domain can be obtained by multiplying a Walsh code by each of a pilot signal and a data signal and then adding them in the adder 121.

In FIG. 5, it is assumed that the spreader 121 uses a Walsh code of length 8 as a spread code and the pre-coder 122 uses a Walsh code of length 4.

The pre-coder 122 multiplies the signals spread by the spreader 121 with a Walsh code of length 4 for every four subcarrier units, adds the products, and outputs the sum.

In further detail, the pre-coder 122 includes a first operator 21 for processing four subcarrier units among eight subcarriers and a second operator 22 for processing the other four subcarrier units, and the first and second operators 21 and 22 respectively include multipliers 31 and 32 for multiplying a Walsh code to each subcarrier and adders 41 and 42 for adding products of the multipliers 31 and 32.

Hereinafter, a digital multimedia broadcasting receiving apparatus according to an exemplary embodiment of the present invention will be described in further detail.

FIG. 6 shows a configuration of a digital multimedia broadcasting receiving apparatus according to an exemplary embodiment of the present invention.

Referring to FIG. 6, a digital multimedia broadcasting receiving apparatus 200 according to the exemplary embodiment of the present invention includes an antenna 210, a demodulator 220, an inverse spreader 230, a channel estimator 240, an equalizer 250, and a data processor 260.

The antenna 210 outputs a signal received from the digital multimedia transmitting apparatus 100 to the demodulator 220.

The demodulator 220 demodulates an output of the antenna 210.

The inverse spreader 230 inversely spreads the signal demodulated by the demodulator 220. In this case, an inverse spread code of the inverse spreader 230 is determined corresponding to a code used for pre-coding in the pre-coder 122 and the length of the code rather than to an inverse spread code that corresponds to the spreader 121 of the digital multimedia transmitting apparatus 100 so as to correspond to a coding result of the pre-coder 122 of the digital multimedia transmitting apparatus 100.

That is, when a pilot signal is inserted every eighth subcarrier unit, a code of length 8 is used in the spreader 121, and a code of length 4 is used in the pre-coder 122 when a Walsh code of length 2 is used for inverse spread in the inverse spreader 230.

In addition, since the code used in the pre-coder 122 may be changed according to a channel condition, a code used in the inverse spreader 230 and the length of the code may be changed corresponding thereto.

In further detail, when the channel condition varies insignificantly, the number of pilots is reduced and therefore the calculation amount of the receiving apparatus 200 for the inverse spread can be further reduced by increasing the length of the pre-code in the pre-coder 122, and when the channel condition varies significantly and thus the calculation amount for the inverse spread is increased, a signal can be transmitted to the receiving apparatus by increasing the number of pilots.

The channel estimator 240 estimates a transmission channel based on a distorted pilot signal output from the inverse spreader 230. In further detail, the channel estimator 240 checks a signal value that is distorted when a subcarrier to which a pilot signal is inserted before being spread in the transmitting apparatus is passed through a channel, and checks channel information by using the distorted signal value. In this case, the checked channel information is information that represents a constant subcarrier unit to which a pilot signal is inserted.

The equalizer 250 equalizes a data signal output from the inverse spreader 230 based on the transmission channel information estimated by the channel estimator 240, and outputs the equalized data signal.

The data processor 260 performs symbol demapping, deinterleaving, and channel decoding processes on the data signal equalized by the equalizer 250 and outputs a result thereof.

FIG. 7 is a schematic view for describing operation of the inverse spreader 230 according to the exemplary embodiment of the present invention.

In FIG. 7, the inverse spreader 230 uses a Walsh code of length 2 for inverse spread. In addition, an input and an output for inverse spread of the corresponding subcarrier among the eight neighboring subcarriers are determined based on Equation 3.

In further detail, as given in Equation 3, a subcarrier value of a signal having passed through the pre-coder 122 of the transmitting apparatus 100 is determined by a combination of a signal that has been initially inserted into a subcarrier before being spread and a signal inserted into the fourth subcarrier in the subcarrier sequence. In addition, subcarriers (e.g., and ) of which values are determined by a combination of the same signals are the same as a product obtained by multiplying a Walsh code of length 2 to the signal that has been initially inserted to the corresponding subcarrier and adding the product.

Therefore, the inverse spreader 230 can inversely spread pilot and data signals by multiplying the Walsh code of length 2 with respect to the subcarriers (e.g., and ) of which values are determined by a combination of the same signals.

FIG. 8 is a schematic view for description of operation of a variable spreader 120 according to a second exemplary embodiment of the present invention.

In the above description, the variable spreader 120 includes the spreader 121 and the pre-coder 122, and the adders 13 spread the pilot and data signals in the frequency domain and the pre-coder 122 multiplies the orthogonal code to the signal spread to the entire frequency domain and outputs the product.

However, the variable spreader 120 according to the second exemplary embodiment of the present invention simultaneously performs the operations that have been separately performed by the spreader 121 and the pre-coder 122. That is, the variable spreader 120 according to the second exemplary embodiment of the present invention spreads the pilot and data signals in the frequency domain and outputs a result in a format that is the same as the output of the pre-coder 122 of the above-described exemplary embodiment of the present invention.

That is, the variable spreader 120 according to the other exemplary embodiment of the present invention spreads a signal to the entire subcarriers by multiplying a Walsh code of length 2 to a signal initially inserted to "one subcarrier" and "the fourth subcarrier" from the one subcarrier in the subcarrier sequence (e.g., and ).

As described, according to the second exemplary embodiment of the present invention, the transmitting apparatus performs the same as that of the above-described exemplary embodiment without adding the pre-coder 122, and the calculation amount of the transmission apparatus can be further reduced.

In FIG. 8, the variable spreader 120 according to the second exemplary embodiment of the present invention uses the Walsh code of length 2 for a spread code, and spreads a signal to the entire subcarriers by multiplying the Walsh code of length 2 to the signal initially inserted to "one subcarrier" and "the fourth subcarrier" from the one subcarrier in the subcarrier sequence (e.g., and ).

As shown in FIG. 8, the signal spread with the Walsh code of length 2 by the variable spreader 120 according to the second exemplary embodiment of the present invention is the same as the signal that has passed through the pre-coder 122 of FIG. 2.

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.

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

A digital multimedia broadcasting transmitting apparatus comprising:

a variable spreader that spreads a pilot signal to a frequency domain and outputs a signal having a format where the pilot signal is partially inserted to the entire subcarriers;

a modulator that modulates the output of the variable spreader; and

an antenna that transmits the signal modulated by the modulator.
The digital multimedia broadcasting transmitting apparatus of claim 1, wherein the variable spreader comprises:

a spreader that spreads the pilot signal to the frequency domain and outputs a signal having a format where the pilot signal is inserted to the entire subcarriers; and

a pre-coder that outputs the signal having the format where the pilot signal is partially inserted to the entire subcarriers by multiplying the signal output from the spreader with an orthogonal code.
The digital multimedia broadcasting transmitting apparatus of claim 2, wherein the spreader spreads the pilot signal by using a spread code having a length that is the same as a period of the pilot signal input to the variable spreader.
The digital multimedia broadcasting transmitting apparatus of claim 3, wherein the spreader spreads the pilot signal by using a spread code that is the same type as the orthogonal code.
The digital multimedia broadcasting transmitting apparatus of claim 4, wherein the length of the orthogonal code is greater than 1.
The digital multimedia broadcasting transmitting apparatus of claim 2, wherein the spreader comprises:

a pilot spreader that spreads the pilot signal to the frequency domain;

a data spreader that spreads a data signal to the frequency domain; and

an adder that adds outputs of the pilot spreader and the data spreader and outputs a signal spread in the frequency domain.
The digital multimedia broadcasting transmitting apparatus of claim 6, wherein the pre-coder comprises an operator for processing a subcarrier unit that corresponds to the length of the orthogonal code,

wherein the operator comprises:

a multiplier that multiplies the orthogonal code to each subcarrier; and

an adder that adds a result of the multiplier for the subcarrier unit.
The digital multimedia broadcasting transmitting apparatus of claim 2, wherein the length of the orthogonal code used when a channel condition varies significantly is shorter than the length of the orthogonal code used when the channel condition varies insignificantly.
The digital multimedia broadcasting transmitting apparatus of claim 1, wherein the variable spreader spreads the pilot signal by using a spread code having a length that is shorter than a period of the pilot signal inserted to the variable spreader.
A method for a digital multimedia broadcasting transmitting apparatus to transmit digital multimedia broadcasting signal, comprising:

spreading a pilot signal in a frequency domain, and outputting a spread signal having a format where the pilot signal is partially inserted into the entire subcarriers; and

modulating the spread signal and outputting the modulated signal.
The method of claim 10, wherein the outputting of the spread signal comprises:

spreading the pilot signal in the frequency domain and outputting a signal having a format where the pilot signal is inserted to the entire subcarriers; and

multiplying the signal having the format where the pilot signal is inserted to the entire subcarriers with an orthogonal code and outputting a signal having a format where the pilot signal is partially inserted into the entire subcarriers.
The method of claim 11, wherein a code used in the spreading of the pilot signal in the frequency domain and outputting of the signal having the format where the pilot signal is inserted to the entire subcarriers is a spread code having a length that is the same as a period during which the pilot signal is initially input.
The method of claim 12, wherein a code used in the multiplying of the signal having the format where the pilot signal is inserted to the entire subcarriers with an orthogonal code and outputting of the signal having the format where the pilot signal is partially inserted into the entire subcarriers is the same type as the code used in the spreading of the pilot signal in the frequency domain and outputting of the signal having the format where the pilot signal is inserted to the entire subcarriers.
The method of claim 13, wherein the length of the orthogonal code is greater than 1.
A digital multimedia broadcasting receiving apparatus comprising:

a demodulator demodulating a signal received from a digital multimedia transmitting apparatus and outputting a signal having a format where a pilot signal is partially inserted to the entire subcarriers; and

an inverse spreader performing inverse spread to the output of the demodulator and outputting a signal having a format where the pilot signal is inserted every constant subcarrier unit among the entire subcarriers and a data signal is inserted to the other subcarriers to which the pilot signal is not inserted,

wherein a code used in the inverse spreader is an orthogonal code, and a length of the code used in the inverse spreader is less than the constant subcarrier unit and is the same as a unit to which the pilot signal is inserted in the signal output from the demodulator.
The digital multimedia broadcasting receiving apparatus of claim 15, further comprising:

a channel estimator that checks transmission channel information based on a pilot signal output from the inverse spreader;

an equalizer that equalizes a data signal output from the inverse spreader based on the channel information checked by the channel estimator and outputs the equalized data signal; and

a data processor that performs symbol demapping, deinterleaving, and channel decoding on the data signal equalized by the equalizer.
A method for receiving a digital multimedia broadcasting signal in a digital multimedia broadcasting receiving apparatus, comprising:

demodulating a signal received from a digital multimedia transmitting apparatus and outputting a signal having a format where a pilot signal is partially inserted to the entire subcarriers; and

performing inverse spread on the output signal and outputting a signal having a format where the pilot signal is inserted every constant subcarrier unit among the entire subcarriers and a data signal is inserted to the other subcarriers to which the pilot signal is not inserted,

wherein a code used in the inverse spread is an orthogonal code, and the length of the code used in the inverse spread is less than that of the constant subcarrier unit.
The method of claim 17, further comprising:

checking transmission channel information based on the inversely spread pilot signal;

equalizing the inversely spread data signal based on the checked channel information and outputting the equalized data signal; and

performing symbol demapping, deinterleaving, and channel decoding on the equalized data signal.