WO2015037833A1

WO2015037833A1 - Ldpc-rs two-dimensional code for ground wave cloud broadcasting

Info

Publication number: WO2015037833A1
Application number: PCT/KR2014/007443
Authority: WO
Inventors: 박성익; 권선형; 김흥묵; 허남호
Original assignee: 한국전자통신연구원
Priority date: 2013-09-10
Filing date: 2014-08-11
Publication date: 2015-03-19

Abstract

A low density party check (LDPC) -reed Solomon (RS) two-dimensional code for ground wave cloud broadcasting is provided. A method for transmitting a ground cloud broadcasting signal may comprise the steps of: encoding information to be transmitted to a two-dimensional code configured by an LDPC code and an RC code; and outputting, line by line, the information encoded into the two-dimensional code.

Description

LDPC-RS two-dimensional code for terrestrial cloud broadcasting

Embodiments of the present invention provide a low density parity check (LDPC) code and a reed solomon (RS) code to correct errors occurring in a wireless channel in a terrestrial cloud broadcasting system operating in a single frequency network. It relates to a constructed two-dimensional code.

Current terrestrial TV broadcasts generate co-channel interference, which is three times the service radius, so that the same frequency cannot be reused in an area within three times the service radius. The area where such frequencies cannot be reused is called a white space, and the spectral efficiency is very low due to the occurrence of the white space. Therefore, in order to improve spectral efficiency, a need has arisen for the development of a transmission technology that facilitates white space removal and frequency reuse that focuses not only on increasing transmission capacity but also on reception robustness.

Accordingly, September 2012 IEEE Transactions on Broadcasting, vol. 58, no. In the academic literature "Cloud Transmission: A New Spectrum-Reuse Friendly Digital Terrestrial Broadcasting Transmission System" published in 3, terrestrial cloud broadcasting technology, which is easy to reuse frequency and does not generate white space, is easy to build and operate a single frequency network. Proposed.

Using such terrestrial cloud broadcasting technology, a broadcaster may transmit the same or different broadcast content nationwide through a single broadcast channel. However, in order to do this, the receiver should be able to receive one or more terrestrial cloud broadcast signals in an overlapping area, that is, an overlapping area in a single frequency network, and separately demodulate the received terrestrial cloud broadcast signals. It should be possible. That is, in the situation where co-channel interference exists and timing and frequency synchronization of respective transmission signals are not guaranteed, the receiver should be able to demodulate one or more cloud broadcast signals. For this purpose, the terrestrial cloud broadcasting system must operate in an environment in which the power of noise is greater than that of the broadcast signal, that is, in a negative signal to noise ratio (SNR) environment.

In addition, terrestrial cloud broadcasting systems are generally designed with the worst case in mind to provide quality service to all viewers. That is, the viewer is designed to stably receive the terrestrial broadcast signal even at the edge (part of the end or boundary) of the broadcast zone. This means that most broadcast zones have a much higher SNR than the edges. For example, more than 80% of the broadcast area is known to have an SNR of at least 5 decibels (dB) above the edge. Therefore, the terrestrial cloud broadcasting system should be able to decode information with a low latency and complexity in a region with a high SNR than in a region with a low SNR.

The technical problem of the present invention can be operated in a negative signal to noise ratio (SNR) environment for terrestrial cloud broadcasting, and LDPC (which can decode information with minimum complexity and latency in a high SNR environment). Low Density Parity Check) -Reed Solomon (RS) two-dimensional code.

Another object of the present invention is to provide a method and apparatus for adaptively decoding the LDPC-RS two-dimensional code.

According to an aspect of the present invention, a method for transmitting a terrestrial cloud broadcast signal includes encoding information to be transmitted into a two-dimensional code including a low density parity check (LDPC) code and a reed solomon (RS) code, and encoded by the two-dimensional code. And outputting information in rows.

In an embodiment, the two-dimensional code may be a code in which a row corresponds to the RS code and a column corresponds to the LDPC code.

In another embodiment, the LDPC code may be an LDPC code of a QC (Quasi-Cyclic) structure.

In another embodiment, the LDPC code is an A matrix of size g × K, a B matrix of size g × g, a C matrix of size (NKg) × (K + g), and a size of (NKg) × ( NKg) and a matrix D of g × (NKg), where N is a length of a codeword, K is a length of information, and g is a value that varies according to a code rate.

In another embodiment, the encoding may include encoding the information to be transmitted in a row unit by using the RS code and secondly by column by using the LDPC code.

As another embodiment, after the encoding, the method may further include dividing the information encoded with the 2D code into a plurality of blocks based on the size of the cyclic sequence matrix constituting the LDPC code.

As another embodiment, the outputting may include outputting information divided into the plurality of blocks in block units.

As another embodiment, the outputting may include outputting the information divided into the plurality of blocks in units of bits.

As another embodiment, the information encoded with the two-dimensional code may be restored by partial decoding using information of the LDPC codeword and a part of parity when the signal-to-noise ratio of the received signal is greater than or equal to the first threshold.

As another embodiment, the information encoded with the 2D code may be restored to RS decoding only without LDPC decoding when the signal-to-noise ratio of the received signal is greater than or equal to a second threshold.

According to another aspect of the present invention, a transmitter for transmitting a terrestrial cloud broadcast signal includes an encoder and a two-dimensional code that encode information to be transmitted into a two-dimensional code including a low density parity check (LDPC) code and a reed solomon (RS) code. It may include an output unit for outputting the encoded information in a row unit.

According to another aspect of the present invention, a receiving apparatus for receiving an LDPC-RS two-dimensional code includes an estimator for estimating a signal-to-noise ratio for a received signal, and a low density parity check (LDPC) code and an RS based on the estimated signal-to-noise ratio (Reed Solomon) It may include a determination unit for determining a decoding algorithm to be applied to a codeword encoded with a two-dimensional code consisting of a code and a decoding unit for decoding the codeword using the determined decoding algorithm.

In one embodiment, the two-dimensional code is a code in which a row corresponds to the RS code and a column corresponds to the LDPC code, or a row corresponds to the LDPC code and a column corresponds to the RS code. Can be.

In another embodiment, the LDPC code may be configured as an identity matrix with a part of parity.

In another embodiment, the codeword may be a codeword primarily encoded by the RS code in a row unit and secondly encoded by the LDPC code in a column unit.

In another embodiment, the estimator may estimate the signal-to-noise ratio using any one of a preamble signal, a pilot signal, and a training signal.

In another embodiment, the determiner may determine at least one of an LDPC decoding algorithm and an RS decoding algorithm as a decoding algorithm to be applied to the codeword.

In still another embodiment, when the decision unit determines to apply the LDPC decoding algorithm to the codeword, the decision unit selects any one of an LDPC decoding algorithm using the entire codeword and an LDPC decoding algorithm using a portion of the codeword. It can be determined by the LDPC decoding algorithm to be applied to the codeword.

According to another aspect of the present invention, a method of decoding a codeword encoded with a two-dimensional code consisting of an LDPC code and an RS code, estimating a signal-to-noise ratio for a received signal, the codeword based on the estimated signal-to-noise ratio The method may include determining a decoding algorithm to be applied to and decoding the codeword using the determined decoding algorithm.

According to still another aspect of the present invention, a decoding apparatus for decoding an LDPC-RS two-dimensional code is to be applied to a decoding algorithm applied to a codeword encoded with a two-dimensional code consisting of an LDPC code and an RS code based on an estimated signal-to-noise ratio for a received signal. And a decoding unit for decoding the codeword using the determined decoding algorithm.

By using a two-dimensional code consisting of a Low Density Parity Check (LDPC) code and a Reed Solomon (RS) code, information can be decoded even in a negative signal to noise ratio (SNR) environment, and partly parity in a high SNR environment. Only the information can be successfully decrypted.

Since a decoding algorithm that has a different complexity and latency is adaptively used according to the SNR, information can be decoded with a minimum complexity and latency in an environment with high SNR.

1 is a diagram illustrating a parity check matrix of a QC-LDPC code applied to the present invention.

2 is a diagram showing the structure of an LDPC-RS two-dimensional code according to the present invention.

3 is a diagram illustrating a process of encoding information using an LDPC-RS two-dimensional code according to the present invention.

4 is a graph showing the BER performance in the AWGN channel of the LDPC-RS two-dimensional code according to the present invention.

5 is a graph showing BER performance in the fading channel of the LDPC-RS two-dimensional code according to the present invention.

FIG. 6 is a diagram illustrating an LDPC-RS two-dimensional code in which information for RS encoding is arranged horizontally. FIG.

7 is a diagram illustrating an LDPC-RS two-dimensional code in which information for RS encoding is arranged vertically.

8 is a diagram illustrating that the LDPC-RS two-dimensional code of FIGS. 6 and 7 have the same form in terms of two-dimensional code.

9 is a diagram for explaining partial decoding of an LDPC-RS two-dimensional code according to the present invention.

10 is a graph showing the performance of the complexity and latency of the LDPC-RS two-dimensional code applied to the present invention.

11 and 12 are diagrams illustrating an information transmission method using an LDPC-RS two-dimensional code according to an embodiment of the present invention.

13 is a flowchart illustrating a method of transmitting a terrestrial cloud broadcast signal according to an embodiment of the present invention.

14 is a flowchart illustrating an adaptive decoding method of an LDPC-RS two-dimensional code according to an embodiment of the present invention.

15 is a diagram illustrating a case where only RS decoding is performed on an LDPC-RS two-dimensional code applied to the present invention.

FIG. 16 is a block diagram showing a transmitting device for transmitting a codeword encoded with an LDPC-RS two-dimensional code, according to an embodiment of the present invention.

FIG. 17 is a block diagram illustrating a receiving apparatus for receiving a codeword encoded with an LDPC-RS two-dimensional code 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. 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. 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, without excluding other components unless specifically stated otherwise. In addition, the term "~ unit" described in the specification means a unit for processing at least one function or operation, which may be implemented in hardware or software or a combination of hardware and software.

The Low Density Parity Check (LDPC) code is known as the error correction code closest to Shannon's limit in the Additive White Gaussian Noise (AWGN) channel, and is approximately better than Turbo's. And parallel decoding (parallelizable decoding) is possible. In general, the LDPC code is defined by a randomly generated low density parity check matrix (PCM). However, the randomly generated LDPC code not only requires a lot of memory to store the PCM, but also takes a long time to access the memory.

Therefore, in order to solve such a memory problem, a QC-LDPC code, which is an LDPC code having a QC (Quasi-Cyclic) structure, may be used. The QC-LDPC code is composed of a zero matrix or a circulant permutation matrix (CPM), and is defined by PCM H as shown in Equation 1 below.

Equation 1

Here, P is a CPM whose size is L × L and is represented by Equation 2 below.

Equation 2

Where P ⁱ is the CPM shifting the identity matrix I (= P ⁰ ) to the right i (0≤i <L) times, and P ^∞ is the zero of size L × L It is a matrix. Thus, since the QC-LDPC code only needs to store exponent ⁱ to store P ⁱ , the memory required to store PCM is significantly reduced.

Therefore, the QC-LDPC code defined by the PCM as shown in FIG. 1 may be applied to the present invention. In FIG. 1, N denotes the length of a codeword and K denotes the length of information. g is a value that varies with code rate. The matrices A and C are g × K and (NKg) × (K + g), respectively, and are composed of a zero matrix and a cyclic permutation matrix of size L × L. The matrix Z is a zero matrix of size g × (NKg) and the matrix D is an identity matrix of size (NKg) × (NKg). The matrix B is a dual diagonal matrix having a size g × g, and is represented by Equation 3 below.

Equation 3

Where I _{L × L} represents an identity matrix of size L × L. As shown in Equation 3, the double diagonal matrix B is an element matrix constituting the double diagonal is an identity matrix and the remaining element matrix is a zero matrix. The element matrix constituting the double diagonal of the double diagonal matrix B may be continuous with the element matrix constituting the diagonal of the identity matrix D.

The QC-LDPC code shown in FIG. 1 shows very good performance near the Shannon limit. In addition, since a part of parity (part corresponding to matrix D ) is composed of the identity matrix, the code rate from the lower code rate mother code through puncturing or truncating technique is used. It can be easily converted to this high code. In other words, the QC-LDPC code has a rate-compatible characteristic such as a Raptor code due to the special structure of the PCM as shown in FIG. 1. However, the QC-LDPC code has an error floor in a region having a bit error rate (BER) of 10-8. In addition, because burst errors occur in the fading channel, a complex bit and frequency interleaver must be used to ensure performance in the fading channel. Therefore, in the present invention, information can be encoded by using the LDPC-RS two-dimensional code as shown in FIG.

FIG. 2 is a diagram illustrating a structure of an LDPC-RS two-dimensional code according to the present invention, and FIG. 3 is a diagram illustrating a process of encoding information using an LDPC-RS two-dimensional code according to the present invention.

In FIG. 2, N _{RS_Info} , N _{RS_Parity} and N _RS respectively indicate information, parity, and codeword lengths for an RS code, and N _{LDPC_Info} , N _{LDPC_Parity} and N _LDPC are LDPC codes, respectively. Indicates the length of information, parity, and codeword. As shown in FIG. 2, a row of the LDPC-RS two-dimensional code according to the present invention corresponds to an RS code and a column corresponds to an LDPC code. Here, the LDPC code corresponding to the sequence of the LDPC-RS two-dimensional code may have the same structure as that of the QC-LDPC code illustrated in FIG. 1, that is, the same PCM.

Accordingly, the transmitting apparatus for terrestrial cloud broadcasting according to the present invention encodes information to be transmitted in row by row using an RS code, as shown in FIG. 3, and secondarily, LDPC. The code can be encoded in columns by column and then output. The receiving device that receives the information (codeword) encoded by the LDPC-RS two-dimensional code can first decode the LDPC codeword and secondly decode the RS codeword.

4 is a graph showing BER performance in the AWGN channel of the LDPC-RS two-dimensional code according to the present invention, Figure 5 is a graph showing the BER performance in the fading channel of the LDPC-RS two-dimensional code according to the present invention.

In FIG. 4, for example, BER performance in an AWGN channel of LDPC code having a length of 16200 or 64800 bits and a code rate of 1/4, and an error of up to 160 bytes in length and up to 7 bytes are corrected. The BER performance in the AWGN channel of the shortened RS code and the LDPC-RS two-dimensional code consisting of the LDPC code is shown, respectively. As a modulation method, QPSK (Quadratic Phase Shift Keying) is used, and a LLR (Log-likelihood Ratio) based sum-product algorithm that performs 50 iterative decoding is used to decode the LDPC codeword. The hard coded hard-decision Berlekamp-Massey algorithm is commonly used to decode RS codewords.

Referring to FIG. 4, the RS output of the LDPC-RS two-dimensional code (the output after decoding the LDPC codeword after decoding the LDPC code) in the AWGN channel not only shows better performance than the output of the existing LDPC code but also occurs in the LDPC code. It can be seen that it removes the error floor phenomenon. In addition, it can be seen that the BER performance of the LDPC-RS two-dimensional code exhibits a sharp-slope slope than the LDPC code.

Meanwhile, the LDPC-RS two-dimensional codeword according to the present invention may be output in a column by column or in a row by row, as shown in Table 1 below.

Table 1

Output of two-dimensional code	effect
Case I (column by column) output in LDPC codeword order	No interleaving
Case II (row by row) RS codeword output	Time & frequency interleaving

Referring to Table 1, Case I, that is, output in column units (output in LDPC codeword order) does not have any interleaving effect, while Case II, that is, output in units of rows (output in RS codeword order) It has a time & frequency interleaving effect by a block interleaver. Accordingly, there is no performance difference between Case I and Case II in the AWGN channel, but shows a very large performance difference as shown in FIG. 5 in the fading channel.

In FIG. 5, the LDPC output shows the performance when only the LDPC codeword is decoded, and the RS output shows the performance when both the LDPC codeword and the RS codeword are decoded. The LDPC and RS codes used in FIG. 5 are the same as in FIG. 4, and the length of the LDPC code is 64800 bits, and the error correction capability of the RS code is fixed to 7 bytes, respectively. In addition, a TU (Typical Urban) -6 channel at 120 km / h was considered for fading.

As shown in FIG. 5, Case II has a much better performance than Case I in the fading channel. The reason for this is that Case I (column by column output) cannot properly distribute a large number of cluster errors in the fading channel, whereas Case II (row by row output) has a time and frequency interleaving effect. This is because it can be properly distributed through the block interleaver. Therefore, in order to effectively distribute the clustering error occurring in the fading panel, the LDPC-RS two-dimensional codeword according to the present invention may be output in units of rows.

FIG. 6 is a diagram illustrating an LDPC-RS two-dimensional code in which information for RS encoding is arranged horizontally, and FIG. 7 is a diagram illustrating an LDPC-RS two-dimensional code in a form where information for RS encoding is arranged vertically. 8 is a diagram illustrating that the LDPC-RS two-dimensional code of FIGS. 6 and 7 have the same form in terms of two-dimensional code. Hereinafter, a case where the code rate of the LDPC code is 1/4, the length is 64800 bits, and the length of the RS code is 160 bytes (1280 bits) will be described.

The RS code encodes information in units of bytes. Accordingly, the LDPC-RS two-dimensional code has a form in which the input bytes (8 bits) for RS coding are arranged in rows as shown in FIGS. 6 and 7, and the input bytes for RS coding are arranged in columns. Arrangement is possible. Referring to FIG. 8, the LDPC-RS two-dimensional code applied to the present invention is composed of 8100 RS codewords and 160 LDPC codewords in both cases, and it can be seen that the LDPC-RS two-dimensional code is exactly the same in terms of two-dimensional code.

The LDPC code used for the above-described LDPC-RS two-dimensional code has a rate-compatible characteristic similar to that of the Raptor code, and thus the code rate is determined through puncturing or truncating. Can be variable. In other words, the LDPC code can be successfully decoded only by the information constituting the LDPC codeword and a part of parity. Therefore, in a region where the received signal-to-noise ratio (SNR) is relatively good, instead of decoding using a whole LDPC codeword, that is, full decoding, a portion of the LDPC codeword (information portion and parity) may be used. Since only partial decoding can be performed, that is, partial decoding, complexity and latency can be greatly reduced. Here, the complexity refers to the amount of computation required during decoding, and the latency refers to the time that the decoder must wait to begin decoding. Hereinafter, partial decoding of the LDPC-RS two-dimensional code according to the present invention will be described in more detail with reference to FIG. 9.

The LDPC codeword constituting the LDPC-RS two-dimensional codeword may be divided into a plurality of blocks as shown in FIG. 9. Since the LDPC code used for the LDPC-RS two-dimensional code has a QC structure and is composed of a CPM having a size L as described above, the size of the blocks may be determined as a multiple of L. For example, FIG. 9 illustrates a case where an LDPC codeword having a length of 64800 bits is divided into 2160 blocks having a length of 30 bits (the size of a CPM). Blocks of the divided LDPC codeword may be sequentially transmitted in the horizontal direction as shown in FIG. 9. That is, it may be output in a row by row in order to obtain the time and frequency interleaving effect.

In this way, when the vertical LDPC codeword is divided into a plurality of blocks and then transmitted in the horizontal direction, not only the time and frequency interleaving effects due to the block interleaver of the LDPC-RS two-dimensional code but also the rate-compatible code of the LDPC code are available. This feature allows for fast decoding with low complexity and low latency.

For example, 780 blocks (540 information blocks + 240 parity blocks) and 1080 blocks among a total of 2160 blocks (540 information blocks + 1620 parity blocks) constituting the LDPC codeword. (540 information blocks and 540 parity blocks), 1300 blocks (540 information blocks and 760 parity blocks) and 1620 blocks (540 information blocks and 1080 parity blocks), respectively. The code rate and length of the received LDPC codeword are 23400 bits (16200 bits of information + 7200 bits of parity) and 2400 code rates of 32400 bits (16200 bits of information + 16200 bits of parity), respectively. ), 39000 bits (16200 bits of information + 22800 bits of parity) at 2/5 code rates, and 48600 bits (16200 bits of information + 32400 bits of parity) at 1/3 code rates. That is, when only a part of the 2160 blocks constituting the LDPC code is received and partially decoded, complexity and latency are greater than full decoding of the existing 1/4 code rate and 64800 bit long LDPC code. Can be reduced.

Table 2 below shows the LDPC mother code of code rate 1/4, the code rate, length, number of '1's in PCM, and complexity for puncturing or truncating LDPC codes. The amount of reduction (proportional to the number of 1s of PCM) and the amount of latency reduction are respectively shown.

TABLE 2

Code rate	Length (N)	Number of 1 in PCM	Complexity reduction	Latency reduction
1/4	64800	277,170	-	-
1/3	48600	199,260	28%	25.0%
2/5	39000	160,260	42%	37.5%
1/2	32400	121,190	56%	50.0%
2/3	23400	82,590	70%	62.5%

10 is a graph showing the performance of the complexity and latency of the LDPC-RS two-dimensional code applied to the present invention. As an example, BER performance according to the reception length of an LDPC codeword having a length of 64800 bits and a code rate of 1/4 in an AWGN channel is shown in comparison with SNR.

As shown in FIG. 10, the receiving apparatus receives 780 blocks (540 information blocks + 240 parity blocks) from a total of 2160 blocks (540 information blocks + 1620 parity blocks) constituting the LDPC codeword. Suppose it is, this corresponds to the LDPC code of 23400 bits in length and 2/3 code rate, and shows the performance of BER = 10 ^-6 when the SNR is around 4.5 dB.

Next, assuming that the receiving device receives 1080 blocks (540 information blocks and 540 parity blocks) out of the total 2160 blocks constituting the LDPC codeword, it is 32400 bits long and has a code rate of 1 /. Corresponds to the LDPC code of 2, and exhibits a performance of BER = 10 ^-6 when the SNR is near 2 dB.

Similarly, assuming that the receiving device has received 1300 blocks (540 information blocks and 760 parity blocks) out of the total 2160 blocks constituting the LDPC codeword, it is 39000 bits long and has a code rate of 2/5. Corresponds to the LDPC code, and shows the performance of BER = 10 ^-6 when the SNR is near 0 dB.

In addition, assuming that the receiving apparatus receives 1620 blocks (540 information blocks and 10800 parity blocks) from a total of 2160 blocks constituting the LDPC codeword, this is 48600 bits in length and 1/3 in code rate. Corresponds to the LDPC code, and shows the performance of BER = 10 ^-6 when the SNR is around -1.5 dB.

Finally, assuming that the receiving device has received all 2160 blocks that make up the LDPC codeword, this corresponds to a mother LDPC code of 64800 bits in length and 1/4 code rate and an SNR of -3 dB. It shows the performance of BER = 10 ^{-6 in} the vicinity.

As described above, the LDPC code of the LDPC-RS two-dimensional code applied to the present invention has different performances according to the received length, and the longer the length of the received codeword, the better the performance. In other words, the higher the reception complexity and latency, the better the performance.

First, in FIG. 11, 160 first blocks are sequentially transmitted among elementary blocks constituting the LDPC codeword, and then 160 second blocks are repeatedly transmitted to the last 160 blocks. A method of transmitting sequentially is shown. On the contrary, in FIG. 12, the first bits of 160 blocks 1, that is, 160 bits are transmitted, and the second 160 bits of blocks 1 are transmitted next, and the process is repeated. A method of transmitting the thirtieth 160 bits of the blocks is shown. The bitwise transmission method as shown in FIG. 12 has an additional bit interleaving effect as compared to the blockwise transmission method as shown in FIG. However, in this case, since the receiver has to wait 4800 bits to receive one block (30 bits) which is a basic block of the LDPC codeword, a longer delay occurs when the LDPC code is decoded.

Referring to FIG. 13, the terrestrial cloud broadcast signal transmission apparatus according to the present invention may encode information (input data) to be transmitted into a two-dimensional code consisting of an LDPC code and an RS code (1310). For example, the transmitting apparatus may first encode the information to be transmitted in the row unit using the RS code and secondly encode the information in the column unit using the LDPC code. The two-dimensional code may be a code in which a row corresponds to the RS code and a column corresponds to the LDPC code. The LDPC code may be an LDPC code of a QC structure.

Thereafter, in order to effectively distribute the clustering error occurring in the fading panel, the coded information (LDPC-RS codeword) may be output in units of rows (1320). At this time, the transmitting apparatus divides the information encoded by the two-dimensional code into a plurality of blocks based on the size of the cyclic sequence matrix constituting the LDPC code, and outputs the information divided into the plurality of blocks in units of blocks or bits. Can be output in units. Faster decoding is possible when output in units of bits, and additional bit interleaving is achieved when output in units of blocks.

The information encoded by the LDPC-RS two-dimensional code according to the present invention can be successfully recovered by partial decoding using information constituting the LDPC codeword and a part of parity when the signal-to-noise ratio of the received signal is greater than or equal to the first threshold. have. In this case, RS decoding is not performed. In addition, the information encoded by the LDPC-RS two-dimensional code according to the present invention can be recovered without error by only RS decoding without LDPC decoding when the signal-to-noise ratio of the received signal is greater than or equal to the second threshold.

14 is a flowchart illustrating an adaptive decoding method of an LDPC-RS two-dimensional code according to an embodiment of the present invention, and FIG. 15 is a diagram illustrating a case where only RS decoding is performed on an LDPC-RS two-dimensional code applied to the present invention. to be.

The reception apparatus for receiving an LDPC-RS two-dimensional code according to the present invention first estimates a signal-to-noise ratio for the received signal using a signal previously promised between the transmitter and the receiver in order to adaptively decode the LDPC-RS two-dimensional codeword (1410). ). Here, the predetermined signal may be a preamble signal, a pilot signal, a training signal, or the like.

Thereafter, the receiving apparatus determines a decoding algorithm to be applied to the LDPC-RS two-dimensional codeword encoded by the LDPC-RS two-dimensional code composed of the LDPC code and the RS code based on the estimated signal-to-noise ratio (1420). Here, the LDPC-RS two-dimensional codeword may be a codeword primarily encoded in a row unit by an RS code and secondly encoded in a column unit by an LDPC code.

In detail, the receiving apparatus may determine at least one of an LDPC decoding algorithm and an RS decoding algorithm as a decoding algorithm to be applied to the LDPC-RS two-dimensional codeword. In this case, when the receiver determines to apply the LDPC decoding algorithm to the codeword, the LDPC decoding algorithm (complete decoding) using the entire LDPC-RS two-dimensional codeword and a part of the LDPC-RS two-dimensional codeword (information portion and An LDPC decoding algorithm (partial decoding) using a portion of the LDPC parity (partial decoding) is determined as an LDPC decoding algorithm to be applied to the LDPC-RS two-dimensional codeword, and the LDPC-RS two-dimensional codeword is decoded using the determined decoding algorithm. (1430).

For example, the receiving device may apply the LDPC-RS decoding method shown in Table 3 according to the SNR value.

TABLE 3

SNR value	Primary LDPC Decoding	2nd RS Decoding
Receive SNR <Threshold + 0.5 dB	Complete Decode (Decode using 2160 blocks)	RS decoding
Threshold + 0.5 dB ≤ received SNR <threshold + 2.5 dB	Complete Decode (Decode using 2160 blocks)	skip
Threshold + 2.5 dB ≤ received SNR <threshold + 4.0 dB	Partial decoding (decoded using 1620 blocks)	skip
Threshold + 4.0 dB ≤ received SNR <threshold + 5.5 dB	Partial Decoding (Decoded using 1300 blocks)	skip
Threshold + 5.5 dB ≤ received SNR <threshold + 8.5 dB	Partial decoding (decoding using 1080 blocks)	skip
Threshold + 8.5 dB ≤ received SNR <threshold + 23.5 dB	Partial Decoding (Decoded Using 780 Blocks)	skip
Threshold + 23.5 dB ≤ receive SNR	skip	RS decoding

Here, the threshold means the performance limit of the LDPC-RS two-dimensional code, and is -3.4 dB in the AWGN channel as shown in FIG. This means that the received SNR must be at least -3.4 dB to receive information without error.

The threshold shown in Table 3 may vary depending on the length and code rate of the LDPC code, the length and error correction capability of the RS code. In addition, the number of LDPC blocks to be used according to the interval for dividing the received SNR, that is, the received SNR may vary.

The LDPC-RS two-dimensional code according to the present invention can be successfully recovered through RS decoding only without LDPC decoding in a very high SNR environment (reception near the transmitter). For example, when 160 blocks 1 are received as shown in FIG. 15, the receiving device may decode 3 RS codewords from 3.75 RS codewords. Therefore, the receiving apparatus can recover information with minimal complexity and latency by performing RS decoding without LDPC decoding in an environment where SNR is very high (for example, a region near the transmitter).

Referring to FIG. 16, the transmitter 1600 for transmitting the terrestrial cloud broadcast signal according to the present invention may include an encoder 1610 and an output unit 1620.

The encoder 1610 encodes the information to be transmitted into a two-dimensional code including an LDPC code and an RS code. The two-dimensional code may be a code in which a row corresponds to the RS code and a column corresponds to the LDPC code, and the LDPC code may be a QC-LDPC code. As an example, the encoder 1610 may first encode information to be transmitted in a row unit using the RS code and secondly encode the information to be transmitted in a column unit using the LDPC code. The coded information may be divided into a plurality of blocks based on the size of the cyclic sequence matrix constituting the LDPC code.

The output unit 1620 outputs the information encoded by the encoder 1610 in units of rows. The output unit 1620 may output information divided into a plurality of blocks in block units or in bit units.

The information encoded by the LDPC-RS two-dimensional code by the transmitting device 1600 is successfully restored by partial decoding using information constituting the LDPC codeword and a part of parity when the signal-to-noise ratio of the received signal is greater than or equal to the first threshold. If the signal-to-noise ratio for the received signal is greater than or equal to the second threshold, the signal may be successfully recovered by only RS decoding without LDPC decoding. In addition, in an area where the signal-to-noise ratio for the received signal is low (the edge of the broadcast zone), it can be successfully decoded through full decoding.

Referring to FIG. 17, a receiver 1700 for receiving an LDPC-RS two-dimensional code according to the present invention may include a receiver 1710, an estimator 1720, a determiner 1730, and a decoder 1740. have.

The receiver 1710 receives an LDPC-RS two-dimensional codeword, a signal previously promised between the transmitter and the receiver, etc. from the transmitter.

The estimator 1720 estimates a signal-to-noise ratio for the received signal. As an example, the estimator 1720 may estimate a signal-to-noise ratio for the received signal based on any one of a preamble signal, a pilot signal, and a training signal.

The determiner 1730 determines a decoding algorithm to be applied to a codeword encoded by a two-dimensional code consisting of an LDPC code and an RS code (LDPC-RS two-dimensional code) based on the signal-to-noise ratio estimated by the estimator 1720. Here, the LDPC-RS two-dimensional code may be a code in which a row corresponds to an RS code and a column corresponds to an LDPC code. Alternatively, the LDPC-RS two-dimensional code may be a code in which a row corresponds to an LDPC code and a column corresponds to an RS code. In this case, the LDPC code may be an LDPC code of a QC (Quasi-Cyclic) structure, and a part of parity may be configured as an identity matrix. The codeword encoded with the LDPC-RS two-dimensional code may be a codeword primarily encoded by the RS code in a row unit and secondly encoded by the LDPC code in a column unit.

For example, the determiner 1730 determines at least one of an LDPC decoding algorithm and an RS decoding algorithm as a decoding algorithm to be applied to the LDPC-RS two-dimensional codeword based on the signal-to-noise ratio estimated by the estimator 1720 as shown in Table 3 below. Can be. When the decision unit 1730 decides to apply the LDPC decoding algorithm to the LDPC-RS two-dimensional codeword, the LDPC decoding algorithm using the entire codeword (complete decoding) and the LDPC decoding algorithm using the portion of the codeword (partial) Decoding) can be determined by the LDPC decoding algorithm to be applied to the codeword.

The decoder 1740 decodes the LDPC-RS two-dimensional codeword using the decoding algorithm determined by the determiner 1730. To this end, the decoder 1740 may include an LDPC decoder 1742 and an RS decoder 1744.

In FIG. 17, the case where the determination unit 1730 is included in the reception device 1700 has been described. However, the determination unit 1730 may be included in the decoding unit 1740 as necessary. In this case, the decoder 1740 may adaptively decode the LDPC-RS two-dimensional codeword according to the signal-to-noise ratio when the information on the signal-to-noise ratio and the LDPC-RS two-dimensional codeword are input. In this case, the decoder 1740 may be implemented as an independent decoding device, and the decoding device may be applied to a codeword encoded with a two-dimensional code consisting of an LDPC code and an RS code based on an estimated signal-to-noise ratio for the received signal. It may include a determining unit for determining a decoding algorithm and a decoding unit for decoding the code word using the determined decoding algorithm.

The above description is merely illustrative of the technical idea of the present invention, and those skilled in the art to which the present invention pertains may make various modifications and changes without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

Claims

In the method for transmitting a terrestrial cloud broadcast signal,

Encoding information to be transmitted into a two-dimensional code including a Low Density Parity Check (LDPC) code and a Reed Solomon (RS) code; And

Outputting the information encoded by the two-dimensional code in units of rows

Transmission method comprising a.
The method of claim 1,

The two-dimensional code is,

And a row corresponds to the RS code and a column corresponds to the LDPC code.
The method of claim 1,

The LDPC code is,

A transmission method characterized by an LDPC code of a QC (Quasi-Cyclic) structure.
The method of claim 1,

The LDPC code is,

A matrix of size g × K, B matrix of size g × g, C matrix of size (NKg) × (K + g), D matrix of size (NKg) × (NKg), and g × of size Consisting of a Z matrix of (NKg),

And N denotes a length of a codeword, K denotes a length of information, and g denotes a value which varies according to a code rate.
The method of claim 1,

The step of encoding,

And firstly encoding the information to be transmitted on a row-by-row basis using the RS code and secondly on a column-by-column basis using the LDPC code.
The method of claim 1,

After the encoding step,

And dividing the information encoded by the two-dimensional code into a plurality of blocks based on the size of a cyclic sequence matrix constituting the LDPC code.
The method of claim 6,

The outputting step,

And transmitting the information divided into the plurality of blocks in block units.
The method of claim 6,

The outputting step,

And transmitting the information divided into the plurality of blocks in bit units.
The method of claim 1,

The information encoded by the two-dimensional code,

And if the signal-to-noise ratio for the received signal is equal to or greater than the first threshold, the transmission method is recovered by partial decoding using information constituting the LDPC codeword and a part of parity.
The method of claim 1,

The information encoded by the two-dimensional code,

And if the signal-to-noise ratio for the received signal is greater than or equal to the second threshold, the system recovers only RS decoding without LDPC decoding.
In the method of decoding a codeword encoded by a two-dimensional code consisting of a low density parity check (LDPC) code and a Reed Solomon (RS) code,

Estimating a signal-to-noise ratio for the received signal;

Determining a decoding algorithm to be applied to the codeword based on the estimated signal to noise ratio; And

Decoding the codeword using the determined decoding algorithm

Decoding method comprising a.
The method of claim 11,

The two-dimensional code is,

And the row corresponds to the RS code and the column corresponds to the LDPC code, or the row corresponds to the LDPC code and the column corresponds to the RS code.
The method of claim 11,

The LDPC code is,

And a part of parity is an LDPC code of a QC (Quasi-Cyclic) structure composed of an identity matrix.
The method of claim 11,

The codeword,

And a codeword encoded first in row units by the RS code and secondly encoded in column units by the LDPC code.
The method of claim 11,

The estimating step,

Estimating the signal-to-noise ratio using any one of a preamble signal, a pilot signal, and a training signal.
The method of claim 11,

The determining step,

And determining at least one of an LDPC decoding algorithm and an RS decoding algorithm as a decoding algorithm to be applied to the codeword.
The method of claim 16,

The determining step,

When the LDPC decoding algorithm is determined to be applied to the codeword, any one of an LDPC decoding algorithm using the entire codeword and an LDPC decoding algorithm using a portion of the codeword is applied to the codeword. Decoding method further comprising the step of determining.
A decision unit for determining a decoding algorithm to be applied to a codeword encoded by a two-dimensional code consisting of a Low Density Parity Check (LDPC) code and a Reed Solomon (RS) code based on the estimated signal-to-noise ratio for the received signal; And

Decoding unit for decoding the codeword using the determined decoding algorithm

Decoding device comprising a.
The method of claim 18,

The codeword,

And a codeword encoded primarily by row by the RS code and secondly encoded by column by the LDPC code.
The method of claim 18,

The determining unit,

Determine at least one of an LDPC decoding algorithm and an RS decoding algorithm as a decoding algorithm to be applied to the codeword, and if it is determined to apply the LDPC decoding algorithm to the codeword, the LDPC decoding algorithm and the code using the entire codeword. And an LDPC decoding algorithm for applying the codeword to any one of the LDPC decoding algorithms using a part of the word.