KR100493094B1 - Symbol puncturing method for channel coder/decoder of mobile communication system - Google Patents

Abstract

The present invention provides a symbol puncturing method for channel encoding and decoding in an enhanced rate adaptation mode (ERAM) puncturing mode of a mobile communication system. J j mod J <K (where j = 0 to J-1), which is a condition for determining whether or not to perform puncture, k _j -J _{j + 1} = Z _j to which the jK mod J can be added. And a second process of determining whether symbol puncturing is performed on the symbol group J using K _j -J _{j + 1} = Z _j . In the above, I = number of information bits per frame input to the turbo encoder including reserved and tail bits, K = j is the indexing value of symbol group J, L is the number of output symbols of the turbo encoder, N is the channel interleaver block size.

Description

SYMBOL PUNCTURING METHOD FOR CHANNEL CODER / DECODER OF MOBILE COMMUNICATION SYSTEM}

The present invention relates to a channel encoding and decoding apparatus of a mobile communication system, and more particularly, to an efficient symbol puncturing method for channel encoding and decoding.

In general, a next generation mobile communication system using a code division multiple access method transmits data for a voice service, an image service, a data service, and control data for performing the services. Minimizing errors during data transmission is one of the important factors in improving the quality of service, so reserved bits, frame quality indicator bits, and tail bits are added to the data. Included together form the input information bit stream. The transmitter in the mobile communication system encodes the input information bit string, performs channel interleaving, and the like, and the receiver of the mobile communication system performs channel deinterleaving and decodes the received signal to obtain the information bit string at the time of transmission.

From the specification of CDMA2000 Release B, a new Enhanced Rate Adaptation Mode ( ERAM) technique used for symbol puncturing during encoding and decoding has been introduced. ( ERAM may not be punctured, but only the puncturing is considered in the present specification.) In the ERAM (hereinafter referred to as "ERAM puncturing mode"), the encoding rate for encoding is not fixed to a single value such as 1/4, but 1/3, 1/4, 1/5, etc. It is a technique of encoding and decoding while being adaptively changed at the same code rate. Assuming that the code rate is 1/3 and the input information bit string is 300 bits, the information bit string encoded by the turbo encoder is 900 bits. The ERAM puncturing mode is defined to be used only for turbo encoding in Radio Configurations 4 and 5 of the forward link and in Radio Configuration 4 of the reverse link.

When ERAM puncturing mode is enabled, the transmitter of the mobile communication system encodes the input information bit stream by a channel encoder consisting of a turbo encoder and a perforator, and then performs channel interleaving by a channel interleaver to transmit and move the input information bit stream. A receiver of a communication system performs channel deinterleaving on a received signal by a channel deinterleaver, and then performs double channel decoding by a channel decoder composed of a back puncturer and a turbo decoder to obtain an information bit string at the time of transmission.

The symbol puncturing standard specified in CDMA2000 Release B is as follows. The parameters used in the ERAM puncturing mode are as follows.

* I = number of information bits per frame input to the turbo encoder, including reserved and tail bits

* L: Number of output symbols of turbo encoder

* N: channel interleaver block size

* J =

* K =

Code symbol group indexing I = 0 to I-1. Here, the symbol symbol group consists of L / I encoded bits.

* Symbol group puncture: (jK) If symbol J <K (where j = 0 to J-1), symbol puncture is performed for symbol group J having indexes 2j and 2j + 1.

* Puncture Pattern: When P (i mod 2) and L are odd, the I-1th symbol symbol group must be punctured.

Table 1 below shows the puncturing pattern in the ERAM puncture mode. The puncturing pattern includes a data puncturing pattern and a tail puncturing pattern.

2I <N 3I R = 1/3 3I <N 4I R = 1/4 4I <N 5I R = 1/5    P0    P1    P0    P1    P0    P1 Data perforation pattern   110   110   1011  1110  11101  11011 Tail perforated pattern   101   110   1011  1011  11011  11011

This specification should be similarly applied not only when puncturing during encoding on the transmitter side but also when performing reverse puncturing during decoding on the receiver side. Due to the addition of this standard, the puncturer should always check whether the condition for judging whether symbol group J is to be performed in the ERAM puncture mode enabled state, that is, jK mod J <K, is satisfied. If jK mod J <K is satisfied, the symbol group J becomes a target for puncturing.

However, checking whether or not jK mod J <K is satisfied to check whether symbol group J is punctured has the following disadvantages. (1) It is impossible to process one symbol per clock because mod needs to be calculated. (2) A multiplier is used to calculate j * K, and as the j value increases, the j * K value also increases, requiring a large number of bits.

Therefore, there is a need for an algorithm for quickly determining whether to perform puncturing of the symbol group J in the ERAM puncturing mode enabled state, that is, whether jK mod J <K is satisfied.

Accordingly, an object of the present invention is to provide a puncturing method for facilitating determination of puncturing by easily performing mod calculation in ERAM puncturing mode.

Another object of the present invention is to provide a puncturing method to configure the efficient hardware by determining the puncturing without performing a complicated operation.

In accordance with the above object, the present invention provides a symbol puncturing method for channel encoding and decoding in an enhanced rate adaptation mode (ERAM) puncturing mode of a mobile communication system. J j mod J <K (where j = 0 to J-1), which is a condition for determining whether or not to perform puncture, k _j -J _{j + 1} = Z _j to which the jK mod J can be added. And a second process of determining whether symbol puncturing is performed on the symbol group J using K _j -J _{j + 1} = Z _j . In the above, I = number of information bits per frame input to the turbo encoder including reserved and tail bits, K = j is the indexing value of symbol group J, L is the number of output symbols of the turbo encoder, N is the channel interleaver block size.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. It should be noted that the same elements in the figures are represented by the same numerals wherever possible. In addition, detailed descriptions of well-known functions and configurations that may unnecessarily obscure the subject matter of the present invention will be omitted.

FIG. 1 is a diagram to help understand symbol puncturing in an ERAM puncturing mode enabler. FIG. 2 is a diagram illustrating a channel encoder including a turbo encoder and a puncturer, and a channel interleaver according to an embodiment of the present invention. The figure showing. FIG. 3 is a diagram illustrating a configuration of a channel decoder and a channel deinterleaver including a back puncturer and a turbo decoder according to an exemplary embodiment of the present invention.

A symbol puncturing operation in the channel encoder in the ERAM puncturing mode enabled state will be described with reference to FIGS. 1 and 2. In the description of the symbol puncturing operation described below with reference to FIGS. 1 and 2, the symbol puncturing standard defined in CDMA2000 Release B and Release C and the variables mentioned in the prior art used in the ERAM puncturing mode are used as they are. Should be understood.

2 shows a part of the configuration of a mobile communication system transmitter, which is composed of a channel encoder and a channel interleaver 24 including a turbo encoder 20 and a perforator 22. The perforator 22 includes a symbol group perforation determiner 26, a perforation pattern comparator 28, and a perforation performer 30. The symbol group puncturing determining unit 26 included in the puncturing machine 22 is a component for determining whether to perform puncturing of the symbol group J when ERAM puncturing mode is enabled, that is, whether jK mod J <K is satisfied. .

The symbols applied to the turbo encoder 20 of the channel encoder shown in FIG. 2 include reserved bits, frame quality indicator bits, and tail bits together in the data. Input information bit string. The I input information bit strings are turbo encoded at the code rate I / L by the turbo encoder 20 and output as L information bit strings. For example, if the bit number I of the input information bit string per frame is 300 bits and the code rate is 1/4, the bit number L of the information bit string encoded by the turbo encoder 20 is 1200 bits.

The L information bit strings turbo-encoded by the turbo encoder 20 at the code rate I / L are applied to the symbol group puncturing judging unit 26 of the puncturer 22, whereby the symbol group puncturing judging unit 26 is performed. It is determined whether to puncture or pass the symbol group J using the condition for determining whether symbol group J is to be punctured, that is, jK mod J <K. The symbol group J is J = As shown in FIG. 1, two code symbol groups (I ₀ , I ₁ ) (I ₂ , I ₃ )... Code symbol group indexing for the code symbol group I is I = 0 to I-1, that is, I ₀ , I ₁ , I ₂ , .., I _I-1 , Group I ₀ , I ₁ , I ₂ , .., I _I-1 consists of L / I encoded bits. Since the code rate R (= I / L) in FIG. 1 is assumed to be I / L = 1/4, the code symbol groups I ₀ , I ₁ , I ₂ , .., I _I-1 are each 4 (= It can be seen that it consists of L / I) encoded bits. In FIG. 1, among the encoded bits of the code symbol group I ₀ , I ₁ , I ₂ , .. I _I-1 , the symbol (bit) of the m mark is an information symbol, and the symbol (bit) of the m symbol is a redundancy symbol. Means (bit). Symbol group J is J = J = Is defined as K = K It is defined as Here, N is a block size of the channel interleaver 24 of FIG.

The symbol group puncturing judging unit 26 satisfies the symbol group J having indexes 2j and 2j + 1 when the condition for determining puncturing of the symbol group J is satisfied, that is, jK mod J <K (where j = 0 to J-1). Determine that the puncture should be performed. If symbol group J is to be punctured, the symbol group J is applied to the puncturing pattern comparison unit 28, and if symbol group J is to be passed without puncturing, the rear end of the puncturer 22 through the pass path 32. Is directly applied to the channel interleaver 24 at.

The puncturing pattern comparison section 28 compares each symbol of the symbol group J provided from the symbol group puncturing judging section 46 with the puncturing patterns described in the table of Table 1 according to the code rate R (= I / L), and performs puncturing. The unit 30 performs symbol puncturing by applying the compared puncturing pattern to the symbols of the provided symbol group J. For example, if the code rate R = 1/4, the puncturing unit 30 performs the data puncturing pattern shown in the table of Table 1 for each of the eight symbols of the symbol group J provided by the symbol group puncturing decision unit 26. 1011 1110 " is applied to puncture the provided symbol if it matches the pattern of " 0 ", and to pass if the provided symbol matches the pattern of " 1 ". One puncturing pattern (P0, P1) is applied to each symbol group index j.

When symbol puncturing is performed by the puncturer 22 of FIG. 2, the L symbols input to the puncturer 22 become the same number of symbols as the channel interleaver block size N of the channel interleaver 24. Is applied). The channel interleaver 24 performs channel interleaving on N symbols and outputs a data string consisting of N symbols.

As described above, the symbol group puncturing determination unit 26 of the puncturer 22 determines whether to puncture or pass the symbol group J using the judgment condition of whether to perform puncturing of the symbol group J, that is, jK mod J <K. In this case, if the symbol condition J is performed by the adder, not the multiplier, and the decision condition of whether the punctuation of the symbol group J is satisfied, that is, jK mod J <K is satisfied, the puncturing judgment of the symbol group J is very difficult. It will happen quickly. To this end, an embodiment of the present invention derives a method that can be implemented as an adder in variables and expressions in jK mod J <K. The method is as follows.

In the judgment condition of whether the symbol group J is to be punctured, that is, jK mod J <K, j increases in the order of symbols. That is, j is sequentially increased to ₀ , ₁ , 2, ... (J ₀ , J ₁ , J ₂ ,...) As shown in FIG. 1. The remaining values K and J in the determination condition are fixed constants in one frame period. In the equation of the determination condition, jK mod J becomes the quotient of the mod operation where n is equal to "0 <jK-nJ <J". Where jK is the dividend and J is the divisor. Then jK-nJ is the remainder and the remainder is always less than the divisor J. But substituting n from 0 to calculate the quotient n increases the computation time and the complexity of control in hardware that is synchronized to the clock. Therefore, in consideration of the characteristic that j increases sequentially, an algorithm that can be easily calculated can be derived.

The formula for determining the code rate of ERAM by the CDMA2000 standard is as follows.

K = Therefore, substituting 1/5 above gives 2K <L-4I. Since L = 5I, eventually 2K <I => K <J. Therefore, the nature of J and K in ERAM puncture mode is that J> K is always true.

In order to know the characteristics of jK mod J, j can be arranged in order as follows.

If j = 0,

jK mod J = 0 * K mod J = 0 <K The symbol group J is puncturing. The quotient n of "jK-nJ <J" = "0 * K-nJ <J" must be n = 0.

If j = 1,

jK mod J = 1 * K mod J = K (since J> K), and the jK mod J <K criterion does not hold, so the symbol group J is not-puncturing. The quotient n of "jK-nJ <J" = "1 * K-nJ <J" must be n = 0.

if j = 2,

jK mod J = 2 * K mod J has a value of (0 2K-J <K), symbol group J must be symbol punctured (jK-nJ <J "=" 2 * K-nJ quotient quotient n = 1), or (2K-J <0) The symbol group J should not perform symbol puncture (n = 0).

if j = 3,

If jK mod J = 3 * K mod J, if there were perforations when j = 2 (0 If 3K-2J <K) is established, puncture is performed (jK-nJ <J "=" 3 * K-nJ <J "quotient n = 2), or (3K-2J <0). Do not (n = 1).

0 if no perforation when j = 2 If 3K-J <K) is established, the puncture is performed (jK-nJ <J "=" 3 * K-nJ quotient n = 1), or (3K-J <0) is performed. Do not (n = 0).

It can be seen from the above case that if j * K − (n _j + 1) * J> 0, then n _{j + 1} = n _j + 1, or n _{j + 1} = n _j (n ₀ = 0)

JK can be expressed as follows.

K _{j + 1} = K _j + K (where K ₀ = 0, K _j = jK)

If K _j- (J _j + J)> 0 then J _{j + 1} = J _j + J, otherwise J _{j + 1} = J _j (where J _j = n _j * J)

If K _j -J _{j + 1} <K, symbol puncture is performed for symbol group J _j , otherwise symbol puncture is not performed for symbol group J _j .

You can easily calculate jK mod J with the above algorithm.

However, if calculated in the above manner, K _j and J _j continue to increase and there is a risk of overflow, or the required number of bits is greatly increased.

Therefore, K _j -J _{j + 1} = Z _j is defined. then,

Z _{j + 1} = K _{j + 1} -J _{j + 2} = K _j + K- (J _{j + 1} + J) = Z_j + K- J, ( = 0 or 1)

Where K _j -J _{j + 1} -J> 0 as described above = 1, otherwise = 0 So if Z _j > J = 1, otherwise = 0

Therefore, by calculating jK mod J = Z _j , the above operation can be obtained without overflow and excessive waste of bits.

If the above described algorithm is developed in a flowchart, it is as shown in FIG.

The symbol group puncturing determination unit 26 sets Z _j = K _j -J _{j + 1} = 0, j = 0, as in step 100 of FIG. I judge J = 0 or 1). If in step 102 the Z If J = 1) Proceed to step 104. In step 104, it is determined whether Z-J <K. If Z-J <K, the method proceeds to step 108 and performs symbol puncturing for the symbol group J. If Z-J <K, the process proceeds to step 118. No puncturing for J. Meanwhile, the symbol group puncturing judging unit 26 determines Z in step 102. If not J = 0) Go to step 106. In step 104, it is determined whether Z <K. If Z <K, the method proceeds to step 112 and performs symbol puncturing for the symbol group J. If Z <K, the method proceeds to step 114 and performs puncturing for the symbol group J. I never do that. In this manner, as in step 116 of FIG. 4, whether the symbol is punctured is determined according to the above-described flowchart for the next symbol group J (j = j + 1).

The present invention can be used not only to perform the puncturing in encoding shown in FIG. 2 but also to perform the reverse puncturing in decoding in FIG. 3 shows a part of a configuration of a mobile communication system receiver, which is composed of a channel deinterleaver 40, a channel decoder composed of a back puncturer 42 and a turbo decoder 44. The reverse puncher 42 includes a symbol group reverse punch determiner 46, a punch pattern comparison unit 48, and a reverse punch performer 50. The symbol group reverse puncturing determination unit 46 included in the back puncturer 42 determines whether a condition for determining whether to perform the reverse puncturing of the symbol group J when ERAM puncturing mode is enabled, that is, jK mod J <K is satisfied. The judgment is performed based on the flow chart of. If the symbol group J is to be subjected to reverse puncturing, the symbol group J is applied to the puncturing pattern comparison unit 48, and if the symbol group J is to be passed without the reverse puncturing, the symbol punctured through the pass path 52 Is applied directly to the turbo decoder 44 at the end of 42).

In the above description of the present invention, specific embodiments have been described, but various modifications may be made without departing from the scope of the present invention. Therefore, the scope of the present invention should not be defined by the described embodiments, but should be determined by the equivalent of claims and claims.

As described above, the present invention makes it easy to determine whether to puncture by performing a mod calculation in the ERAM puncturing mode, and it is possible to construct an efficient hardware by determining the puncturing without performing a complicated operation such as multiplication.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram for explaining an explanation of an operation of symbol puncturing in a channel encoder when ERAM puncturing mode is enabled.

2 is a diagram illustrating a configuration of a channel encoder and a channel interleaver according to an embodiment of the present invention;

3 is a diagram illustrating a configuration of a channel decoder and a channel deinterleaver according to an embodiment of the present invention;

4 is a control flowchart of a symbol group puncturing determination unit in a puncturer and a reverse puncturer according to an embodiment of the present invention.

Claims (4)

In the symbol puncturing method for channel encoding and decoding in the ERAM (Enhanced Rate Adaptation Mode) puncturing mode of a mobile communication system, The symbol group J for encoding and decoding (J is J j mod J <K (where j = 0 to J-1), which is a condition for determining whether or not to perform puncture, k _j -J _{j + 1} = Z _j to which the jK mod J can be added. 1 course, And a second process of determining whether symbol puncturing is performed on the symbol group J using the K _j -J _{j + 1} = Z _j . In the above, I = number of information bits per frame input to the turbo encoder including reserved and tail bits, K = j is the indexing value of symbol group J, L is the number of output symbols of the turbo encoder, N is the channel interleaver block size. The method of claim 1, wherein the second process comprises: Z The first step of judging J or Z above A second step of selectively performing symbol puncturing on the symbol group J according to whether Z-J <K if J, and Z above And a third step of selectively determining whether to perform symbol puncturing for the symbol group J according to whether or not Z <K. The symbol puncturing method for channel encoding and decoding according to claim 1, wherein the symbol puncturing is performed. 3. The method of claim 2, wherein in the second step, when Z − J <K, symbol puncturing is performed on the symbol group J, and when Z − J <K, the puncturing on the symbol group J is not performed. Symbol puncturing method for channel encoding and decoding characterized in that. 3. The channel encoding method of claim 2, wherein the third step includes performing symbol puncturing on the symbol group J when Z <K, and not performing puncturing on the symbol group J when Z <K. 4. Symbol puncturing method for decoding.