KR100347501B1 - Optimized rate-compatible turbo encoding - Google Patents

Abstract

The turbo encoding method and apparatus utilizes a set of rate-compatible turbo codes that are optimized at a high code rate and derived from a universal configuration code. The turbo code has a rate-compatible puncturing pattern. The method comprises the steps of encoding a signal at a first encoder and a second encoder using an upper code rate and a universal best rate 1/2 configuration code, the first encoder and the second encoder having And generating a plurality of parity bits of the data; Puncturing each of the plurality of parity bits in each encoder with a best puncturing pattern of the highest rate; And puncturing each of the plurality of parity bits in the respective encoder with the best puncturing pattern of the subrate. In the variant, the best rate 1/2 configuration code represents the combination of polynomials 1 + D ² + D ³ (octal 13) and 1 + D + D ³ (octal 15) (where D is the data bit). The hardware embodying the invention is provided in a turbo encoder.

Description

[0001] OPTIMIZED RATE-COMPATIBLE TURBO ENCODING [0002]

To provide high quality communications over RF propagation channels that result in signal waveforms and spectral distortion, including signal attenuation (free space propagation loss) and multipath inflow fading, forward error correction (FEC) is required for terrestrial and satellite radio systems do. With these drawbacks, it is necessary to consider hardware components that together provide an efficient balance between the design of the radio transmission and receiver equipment, the modulation format, the error control scheme, the design objective to select demodulation and decoding techniques, and the system performance and implementation complexity . Due to differences in propagation channel characteristics, such as between terrestrial and satellite communication channels, the results of system design naturally vary greatly. Similarly, existing communication systems continue to evolve to meet increased system requirements for new higher rates or more robust communication services.

In the case of a terrestrial cellular mobile radiotelephone, the analog mobile telephone system (AMPS) is an exemplary first generation system: IS-136 and European GSM Time Division Multiple Access (TDMA) standards and U.S. The IS-95 Code Division Multiple Access (CDMA) standard is a second generation system; The currently developing broadband CDMA standard (i.e., CDMA 2000 in the US and UTRA in Europe) is a third generation system.

In third generation systems, the development of flexible, high-speed data communication services is of major interest. Preferred features include the ability to perform rate adaptation and satisfy various quality-of-service (QOS) conditions.

Conventional forward error correction (FEC) schemes for communication systems include the use of convolutional codes, block codes such as Reed-Solomon or BCH codes, and / or reduced coding schemes.

Turbo codes are a relatively new class of block codes that have been argued to provide a bit error rate (BER) close to the theoretical limit for an important class of idealized channels by a circular soft-decision decoding method to be.

The turbo encoder typically includes two systematic cyclic convolutional codes (" constituent codes ") separated by an interleaver that randomizes the representation order of the information bits for the second constituent encoder associated with the first constituent encoder The performance of the turbo code depends on the configuration code, the interleaver, the information block size (which generally increases with the higher data rate), and the number of decoder iterations. For a particular turbo code with mixed configuration codes, the block size and decoder iteration count can ideally be adjusted to compromise performance, delay, and implementation complexity requirements. However, as the block size changes, a new interleaver matching the corresponding clock size is required.

In a CDMA network with a synchronization base station, the forward link channel (from the base station to the user terminal) may be designed to be orthogonal using, for example, a Walsh-Hamad spreading sequence. However, in the case of a reverse link channel (from a user terminal to a base station) operating asynchronously using a pseudo-orthogonal spreading sequence, this is generally not possible. Thus, a reverse link in a synchronous CDMA network typically has more interference, and therefore may require a stronger FEC (via a code of the lower rate) than the forward link channel.

For asynchronous CDMA networks, the forward and reverse link channels are somewhat similar in terms of interference level, so it is possible to use a common FEC scheme (or at least one similar FEC scheme) on the two links.

The flexibility and high performance of TurboCOD is becoming a potentially promising technology for advanced data communication services. Thus, it is desirable to identify turbo coding FEC schemes and turbo codes that optimally match the various service conditions and the respective data rates and coding rates while minimizing implementation complexity.

The present invention benefits from the above and other needs by providing a method for designing and using universally optimized turbo codes and rate-compatible punctures as an advantage to support an incremental redundancy scheme such as automatic repeat request (ARQ) It is correcting.

SUMMARY OF THE INVENTION [

In a most basic form, the present invention provides, in one embodiment as a method of processing data, a turbo code in which a set of rate-compatible turbo codes are optimized at a high code rate to produce a turbo with a compatible puncturing pattern in a data service derived from universal configuration code Code. The method comprises the steps of encoding a signal at a first encoder and a second encoder using a universal best rate 1/2 configuration code according to an upper code rate and a lower code rate, Generating a plurality of respective parity bits for the bits; Puncturing each of the plurality of parity bits in each encoder with a best puncturing pattern of the highest rate; And puncturing each of the plurality of parity bits in the respective encoder with the best puncturing pattern of the subrate.

In a variation, a set of rate-compatible turbo codes derived from an optimal universal rate 1/3 configuration code, the turbo code having a similar configuration code and compatible puncturing patterns A method of processing data in a data service includes encoding a signal having a best rate of one third in a first and a second encoder, each encoder generating a respective plurality of parity bits for each data bit -; Puncturing the plurality of parity bits with the highest puncturing pattern of the highest rate; And puncturing the plurality of parity bits with the best puncturing pattern of the sub-rate.

In another variation, a set of rate-compatible turbo codes, the set being rate-compatible using a code rate 1/4 and having turbo codes with different code rates and rate-compatible puncturing patterns The turbo encoding method comprises the steps of encoding a signal in a first encoder and a second encoder using a top code rate and a sub code rate and a universal best rate 1/4 configuration code, Each generating a respective plurality of parity bits for a data bit; Puncturing each of the plurality of parity bits in each encoder with a best puncturing pattern of the highest rate; And puncturing each of the plurality of parity bits in each encoder with the best puncturing pattern of the subrate.

In another embodiment, the encoding system uses a set of rate-compatible turbo codes derived from the best universal 1/2 configuration code, the set having a compatible puncturing pattern, A second encoder, each encoder comprising a first and a second adder coupled to selected portions of the first and second adders, respectively, in a configuration corresponding to the best universal 1/2 configuration code; box-; And a puncturer configured to cause the first and second encoders to puncture a plurality of data outputs from each of the first and second encoders, wherein the puncturing is performed based on the set of compatible puncturing patterns, Determined by the turbo code rate.

In another variation, the encoding system uses a set of rate-compatible turbo codes derived from an optimal universal 1/3 configuration code, wherein the rate-compatible turbo codes have a similar configuration code and a compatible puncturing pattern And wherein the encoding system comprises a first and a second encoder, each encoder having a plurality of shift registers, and a second encoder coupled to selected portions of the first and second adders in a configuration corresponding to the rate 1/3 configuration code, 1 and a second adder; And a puncturer configured to puncture the plurality of data outputs from the first and second encoders, wherein the puncturing is performed using a predetermined turbo code according to the set of compatible puncturing patterns, Determined by the rate.

Another variation of the system employs a set of rate-compatible turbo codes having a universal constituent code and a rate-compatible puncturing pattern for different code rates, the system comprising a first and a second Encoder, wherein each encoder comprises a plurality of shift registers and first and second adders respectively coupled to selected portions of the first and second adders in a configuration corresponding to the universal configuration code; And a puncturer configured to puncture a plurality of data outputs from the first and second encoders, the puncturing being determined by a predetermined turbo code rate according to the set of compatible puncturing patterns .

BRIEF DESCRIPTION OF THE DRAWINGS [

These and other aspects, features, and advantages of the present invention will become more apparent from the following more detailed description, taken in conjunction with the following drawings.

1 is a code division multiple access (CDMA) digital cellular mobile radio system hardware diagram.

2 is a hardware diagram of a CDMA digital cellular mobile radio system in which embodiments of the present invention may be implemented.

3 is a functional block diagram of a turbo-code encoder modified for use with the present invention.

4 is a functional block diagram of an overall turbo decoder;

Figures 5,6,7 and 8 illustrate that the turbo code uses interleaver sizes 1000, 512 and 1024 bits of turbo code rate 1/2 and rate 1/3 when using the candidate configuration code represented as d (D) and n (D) 0.0 > (BER) < / RTI > performance versus signal-to-noise ratio (SNR)

Figure 9 shows puncturing schemes for optimizing rate 1/4 turbo codes.

Figures 10, 11 and 12 show the BER / FER performance of configuration code # 1-3, which is a frame size of 512 bits.

13 is a diagram illustrating the BER / FER performance of configuration code # 1 where configuration code # 1 is a frame size of 1024 bits and consistent results are obtained at sizes 2048 and 3072 bits, respectively.

14 shows the BER / FER performance of a selected rate 1/4 turbo code at frame size 512, where a consistent result is obtained for each of the size 1024, 2048 and 3072 bits.

15 is a comparison of a preferred turbo code B for another puncturing scheme with a frame size of 512 bits.

16 is a layout of candidate puncturing patterns for rate 1/3 and 1/2 turbo codes when the configuration code has a rate of 1/3.

17 is a comparative view of a rate 1/3 puncturing scheme at a frame size of 512 bits;

FIG. 18 shows a rate 1/2 puncturing scheme at 512 bits of frame size that yields consistent results at 1024, 2048, and 3072 bits, respectively. FIG.

19 is a block diagram of a preferred universal configuration encoder for a turbo code optimized at code rate 1/2 and 1/3 to vary interleaver depth.

20 is a functional block diagram for a rate 1/4 turbo code optimized at code rate 1/2 and rate 1/3, including interleaving and puncturing (rate 1/3 and rate 1/2 use similar processing).

Figure 21 is a puncturing pattern for a rate 3/8 turbo code.

22 shows a 3/8 turbo code whose result is optimized at code rate 1/2 and rate 1/3 at a constant frame size 512 bits at 1024, 2048 and 3072 bits, respectively.

Figure 23 is a puncturing pattern for a rate 4/9 turbo code.

Figure 24 shows a rate 4/9 turbo code optimized at code rate 1/2 and rate 1/3 using 512 bits of frame size.

25 is a functional block diagram of a preferred configuration encoder for a turbo code optimized at a code rate of 1/4.

26 is a functional block diagram of a rate 1/4 turbo code optimized at rate 1/4 including interleaving and puncturing (rate 1/3 and rate 1/2 use similar processing).

Figure 27 is a puncturing pattern for a rate 2/9 turbo code.

Figure 28 shows a rate 2/9 turbo code optimized with a code rate of 1/4 using 512 bits of frame size.

29 is an initial puncturing pattern for a rate 3/8 turbo code;

Figure 30 shows a rate 3/8 turbo code optimized with a code rate of 1/4 using 512 bits of frame size.

31 is a functional block diagram of a preferred universal encoder for a rate 1/2 and rate 1/3 turbo code that varies interleaver depth.

32 is a preferred comparison of a rate 1/4 FER-optimized turbo code with 1024, 2048, and 3072 bits with convolutional codes at 512 bits of consistent frame size.

Appendix A is a collective set of drawings, which may be referred to as "similar" drawings, curves, or simulations or equivalents.

Corresponding reference characters refer to corresponding elements throughout the several views.

The present invention relates to error correction in data communication, and more particularly to forward error correction (FEC). In particular, the present invention is based on the emerging 3 < Desc / Clms Page number 3 > approach that is highly flexible in supporting a wide range of system conditions related to transmission data rate, channel coding rate, service measurement quality (i.e., delay, bit error rate, frame error rate) And more particularly to the selection and use of optimal turbo codes in high performance data communication systems such as terrestrial cellular mobile radio and satellite telephone systems.

The following description of the invention is not to be taken in a limiting sense, but merely to illustrate the general principles of the invention. The scope of the present invention should be determined with reference to the appended claims.

Two major features of the present invention are: 1) Forward Air Calibration (FEC) for data services based on specific " Universal " turbo codes that have been demonstrated to provide near-optimal performance over a wide range of information block sizes and code rates. ), And 2) a method by which a specific turbo code having the above-described desirable properties can be designed.

Turbo codes are particularly well-suited for data applications because of their excellent error-correcting capabilities with low signal-to-noise (SNR) ratios and flexibility to trade off bit error rate (BER) and frame error rate (FER) performance to handle delays. . The data service being considered in the embodiments described below conforms to the third generation code division multiple access (CDMA) cellular mobile wireless standard under development and is typically more delay tolerant than the low rate voice service.

However, the universal turbo codes (and methods for obtaining such codes) specified below may also be used in other cellular mobile radio systems (e. G., European Time Division Multiple Access TDMA) standard). ≪ / RTI > Several specific turbo codes have been identified that provide different optimizations in relation to these conditions. Other codes will also be possible.

In order to optimize the performance of the turbo codes for data services, it is necessary to have a set of " universal " constituent codes that provide optimal or near optimal performance in combination with various different interleaver depths and turbo code rates, It is desirable to avoid tailoring each optimization of the turbo code.

Referring first to Figure 1, an exemplary conventional digital cellular mobile radio system using a direct sequence code division multiple access (CDMA) mobile station to base station (or reverse link) is shown using a convolutional encoder and a Viterbi decoder have. Such basic coding and interleaving is equally applicable to other multiple access systems such as time division multiple access (TDMA) used in the known GSM standard.

Figure 1 also shows a base station to mobile (or forward) link in a cellular mobile radio system. In transmission system 100, the system assembles a user information bit from a data terminal device (not shown) into a fixed length frame of N bits per frame 106 that is input to a convolutional encoder 108 And a segmentation processor 104. The convolutional encoder 108 is coupled to a synchronization and framing processor 104 that generates an N / r code symbol 110 at the input of a channel interleaver 112 coupled to the convolutional encoder 108. The channel interleaver 112 performs pseudo-random shuffling of the code symbols 110 and outputs the code symbols 110 to the spread spectrum modulator 114 coupled to the channel interleaver 112. Spread spectrum modulator 114 uses spread spectrum modulator 114 to provide a spread spectrum modulator 114 with a user-specific transmit PN-code generated by PN converter 116 coupled to spread spectrum modulator 114, Signal. The mobile station RF transmitter 118 is also coupled to a spread spectrum modulator 114 in which a high power amplifier (not shown) coupled to transmit antenna 120 copies signals to the base station. Spread-spectrum modulation and RF transmission techniques are known to those skilled in the art of spread-spectrum communication systems.

The mobile station ^A received by the base station reception antenna 122 ) ^A Mobile station signal Is demodulated in spread spectrum demodulator 128 that is amplified in base station RF receiver 124 and despreads the signal using the same PN code used by mobile station RF transmitter 118. [ The demodulated symbols are deinterleaved by the channel interleaver 130 and input to the Viterbi decoder 132. The decoded information bits are reconstructed into a received data block 136 and forwarded from the receiving end of the system to the data terminal equipment.

Referring now to Figure 2, a hardware system for a digital cellular mobile radio system embodying an embodiment of the present invention is shown. As described above, although the same block diagram shows the forward link, the reverse link is shown. Also, although a CDMA system is used as an example, one skilled in the art can also consider the present invention to apply to other systems such as TDMA.

The transmission data block 202 from the data terminal equipment is segmented and framed at a fixed frame length in the segmentation processor 204 and applied to the turbo code encoder 208. [ The output from the encoder 208 is supplied to the channel interleaver 212 to pseudo-randomize the code symbols. The channel interleaver 212 provides an output to a spread spectrum modulator 214 that generates a spread spectrum that is carried on the RF carrier to the mobile station RF transmitter 218 using a user specific PN code from the PN generator 216 do. The channel interleaver 212 is distinct from the turbo code interleaver (not shown), which is a component of the encoder 208. The mobile station RF transmitter 218 coupled to the transmit antenna 220 uses the high power amplifier (not shown) of the transmit antenna 220 to copy the signal to the base station.

The signal from the mobile station received at the base station antenna 222 is amplified at the base station RF receiver 224 and transmitted to a spread spectrum demodulator that is despreading the signal using the same PN code as used by the mobile station RF transmitter 218 228). The demodulated symbols are deinterleaved by the channel DE-interleaver 230 and input to the turbo code decoder 232. The decoded information bits from the turbo code decoder 232 are reconstructed into a received data block 236 at the reconstruction processor 234 and forwarded to the data terminal device at the receiving end.

Referring to FIG. 3, the basic structure of the turbo code is characterized by parallel reduction of two simple configuration codes in the encoder # 1 306 and the encoder # 2 308. The two constituent encoders, Encoder # 1 306 and Encoder # 2 308, process the same information bit stream 302, while Encoder # 2 308 decodes the information bits to encoder # 2 308 306 processes the information bits 302 in an order different from the order in which the encoder # 1 306 processes the information bits 302 because the interleaver 304 rearranges them before reaching the encoder 308. This configuration allows the sequence of information bits 302 to cause Encoder # 1 306 to generate a low-Hamming weight output 310 also causes Encoder # 2 308 to provide an excellent Thereby reducing the likelihood of equalizing the output 314 enabling performance.

In addition to the information bits 302 (also referred to as systematic bits 302), both the encodings 306 and 308 generate parity bits 310 and 314 punctured by a puncturer 312 to produce a predetermined overall turbo code Rate. It can also puncture systematic bits.

The configuration code of the turbo code is a systematic, cyclic convolutional code that is usable. The simplest and most widely known circular convolutional code has a transfer function of rate 1/2 and the following:

G (D) = [1, n (D) / d (D)]

Where n (D) and d (D) are binary multiple formats specifying the feedforward and feedback connections of the encoders, respectively.

The rate of the turbo code is changed by changing the selection of the output bits 310, 314 for puncturing or transmission. In all of the following cases, " 1 " indicates transmission, and " 0 " indicates puncturing.

FIG. 3 also shows two possible puncturing pattern results from the puncturer 312. In turn, puncturing the parity bits between the encoders 306 and 308 results in a turbo code rate r = 1/2. The transmission of all parity bits in the two encoders 306 and 308 will result in a code rate r = 1/3.

It is not possible to achieve a low turbo code rate of 1/3 or less without increasing the number of configuration encoders or increasing the number of output parity bits per configuration encoder. The latter is often desirable to reduce implementation complexity. In this case, one skilled in the art will consider a rate 1/3 systematic cyclic convolutional code with the following transfer function.

G (D) = [1, n 1 (D) / d (D), n 2 (D) / d (D)]

By using these two configuration codes, puncturing or deleting provides an arbitrary turbo code rate between 1/5 and 1.

The turbo code is decoded using the iterative decoding method as shown in the block diagram of Fig.

Each configuration code is individually decoded using similar estimates of the other configuration decoders 406 or 416 as ' a priori ' information. The configuration decoders 406 and 416 must be soft-input / soft-output types such as a MAP (Maxium A Posteriori) algorithm, a sub-optimal Soft-Output Viterbi Algorithm (SOVA) or a variant thereof. After all the configuration decoders process the data, the process can be repeated.

Indeed, the turbo decoders 406,416 are often limited to a fixed number of iterations to meet the implementation complexity and performance goals of the system.

4 is an overall block diagram of a turbo decoder. Soft information related to the information bits 404, parity bits for the first encoder 402, and parity bits for the second encoder 402 'are received from the demodulator. First, the first decoder 406 generates a soft decision 408 for the information bits using the received information 404 and the received parity bits 402. [ Soft decisions 408 are interleaved by interleaver 412, whose outputs are soft decisions 414. The soft decision 414 is supplied to the second decoder 416 as a priori information.

The second decoder 416 receives the soft decisions 414 described above and then provides an enhanced soft decision 420 for the information bits 420 interleaved by the interleaver 422 and supplied to the second decoder 406 as a priori information ). The entire process is repeated as many times as necessary. The final output 420 is obtained by making a hard or soft decision of the first or second decoder.

According to the present invention, it is possible to derive a uniform turbo code and various puncturing patterns to obtain a uniform good code for various code rates and information block sizes.

First, a methodology for determining the universal configuration code is developed by limiting the initial pool of possible universal configuration codes according to a trade-off between performance and implementation complexity. According to the present invention, performance studies using different status codes indicate that the 8-state configuration code provides a good performance trade-off.

The universal configuration code is first optimized according to the main code rate of the target application. For example, in the case of CDMA data communications, individual optimizations may be performed on the forward and reverse links, since the reverse link often requires a lower code rate for higher coding gain.

The next step, described in more detail below, is used to generate turbo codes optimized for rates 1/2 and 1/3.

The transfer function of 1) G (D) = [ 1, n (D) / d (D)] type (where, d (D) is a primitive polynomial, n (D) starting with 1 and ends with D ³⁾ Lt; RTI ID = 0.0 > 1/2 < / RTI >

2) determine the turbo code rate 1/2 and rate 1/3 test puncturing pattern to apply to the output data encoded by the two rate 1/2 configuration encoders;

3) Combine the test pattern with each rate 1/2 configuration code to form all possible rate 1/2 and 1/3 turbo codes;

4) evaluate the relative BER performance of all possible rate 1/2 and 1/3 turbo codes with fixed interleaver length;

5) Based on the best overall BER performance, choose from a group of mother pairs, a subgroup of candidate pairs, to build an optimal turbo code;

6) Evaluate other relative BER performance of a turbo code group having subgroups of candidate pairs punctured in rate 1/2 and rate 1/3 puncturing patterns with a plurality of different interleaver depths.

7) choose among turbo code groups, universal codes, with best overall overall relative BER for interleaver depth; And

8) Encode data with rate 1/2 and rate 1/3 turbo code with the selected universal code pair in the first and second encoders - Similar encoder and interleaver supply bits to the second encoder, Are aligned differently before entering each encoder.

Once generated, a superior turbo code of a lower rate such as 1/4, which is compatible with the rate 1/2 and the 1/3 turbo code determined by the above step, can also be determined.

Rate 1/2 configuration code

The following description explains how the rate 1/2 configuration code is determined in one embodiment.

First, a list of candidate 8-states, rate 1/2 configuration code polynomials is determined.

Table 1 lists the denominator polynomial d (D) and the molecular polynomial n (D) determined by the octal method. There are 12 candidate congruity candidates considered for initial testing.

Rate 1/2 candidate 8-state configuration encoder Denominator polynomial d (D) (octal) Molecular polynomial n (D) (octal) 11 12 11 15 11 17 12 11 12 15 12 17 15 11 15 12 15 17 17 11 17 12 17 15

Each of the twelve (12) polynomials is represented in octal form in Table 1 and has a corresponding binary and polynomial. For example, the binary equivalent of octal number 13 is binary 1011. Binary 1011 corresponds to the following polynomial:

D (D) = D ⁰ (1) + D ¹ (0) + D ² (1) + d ³ (1) = 1 + D ² + D ³ .

Next, the candidate turbo code is simulated with a 1000 bit interleaver size and three decoder iterations. The exemplary results shown in Figures 5 and 6 assess the bit error rate (BER) vs. Ebi / No performance of all candidate turbo codes at rate 1/2 and rate 1/3, as described above. The measurement of Ebi / No is equivalent to the relative SNR.

The results in Figures 5 and 6 are used to select six (6) code polynomial pairs. The six (6) candidate universal code pairs d (D) -n (D) are shown in octal representation on the left-hand side of Table 2 below.

Table 2 is then generated using the corresponding performance of 8-state turbo codes using simulated data with candidate universal codes at each rate and interleaver depth. Sample performance studies or simulations are shown in Figures 7 and 8 which illustrate selected turbo codes of 512 bit interleaver depth for rate 1/2 and rate 1/3.

Table 2 below shows the approximate SNR loss for the simulated data due to the use of rate 1/2 and 1/3 and interleaver depths of 512, 1024, 2048 and 3072 bits.

Approximate SNR loss due to use of non-optimized code Candidate " universal " code d (D) -n (D) Turbo code rate size (bits) 1/2512 1/21024 1/22048 1/23072 1/3512 1/21024 1/32048 1/33072 15-13 0.005 dB 0.00 dB 0.00 dB 0.05 dB 0.10 dB 0.05 dB 0.05 dB 0.10 dB 13-15 0.00 dB 0.00 dB 0.00 dB 0.00 dB 0.05 dB 0.05 dB 0.05 dB 0.05 dB 15-17 0.05 dB 0.05 dB 0.00 dB 0.05 dB 0.05 dB 0.05 dB 0.00 dB 0.10 dB 17-15 0.40 dB 0.50 dB 0.00 dB 0.00 dB 0.05 dB 0.00 dB 17-13 0.40 dB 0.50 dB 0.00 dB 0.00 dB 0.00 dB 0.00 dB 13-17 0.05 dB 0.05 dB 0.05 dB 0.00 dB 0.00 dB 0.10 dB 0.00 dB 0.10 dB

In similar simulations using a 16-state code, the pairs referred to as 31-33 and 31-27 are also used to provide a similar complexity comparison with 8-state codes using eight (8) decoder iterations, A sample using four (4) decoder iterations for the status code is shown in Figures 7 and 8. An 8-state code with eight iterations performs a 16 state code with four iterations.

As a separate simulation, the performance difference among the different interleavers using the six (6) candidate pairs is observed to be within 0.05 dB.

Finally, the results in Table 2 show that the following rate 1/2 configuration code pairs provide overall best performance over the range of rates and interleaver sizes studied.

d (D) = 1 + D 2 + D 3; n (D) = 1 + D + D ³ .

This represents an octal number 13 and an octal number 15, respectively.

In each case tabulated, the performance of codes 13-15 is within 0.05 dB for the best performance code for rate and interleaver size.

Thus, this configuration code is chosen as the basis for a turbo code design where superior code rates, such as 1/2 and 1/3, are preferred.

Rate 1/3 configuration code

The following describes how the rate 1/3 configuration code is determined. Similar to the rate 1/12 configuration code, rate 1/3 configuration code candidates are identified in Table 3 below to establish a near optimal 1/4 and 1/5 turbo code rate. In this case, the configuration code candidate for the turbo code must have three (3) polynomials instead of two (2).

Candidate configuration code for optimal subrate turbo code CC # 1 (Oct. 13-15 / 17) CC # 2 (Oct. 15-13 / 17) CC # 3 (Oct. 17-13 / 15) d (D) = 1 + D 2 + D 3 (8 decimal _{13) n 1 (D) =} 1 + D + D 3 (8 decimal _{15) n 2 (D) =} 1 + D + D 3 (8 hexadecimal 17 ) d (D) = 1 + D + D 3 (8 decimal _{15) n 1 (D) =} 1 + D 2 + D 3 (8 decimal _{13) n 2 (D) =} 1 + D + D 2 + D 3 ( Octal number 17) d (D) = 1 + D + D 2 + D 3 (8 decimal _{17) n 1 (D) =} 1 + D 2 + D 3 (8 decimal _{13) n 2 (D) =} 1 + D + D 3 ( Octal 15)

Optimal rate 1/4 turbo code

In order to build the overall rate 1/4 turbo code, various puncturing schemes in combination with the respective configuration codes in Table 3 must be considered.

The various puncturing schemes of FIG. 9 are considered first. For a rate 1/4 code, the common input information bits or systematic bits are transmitted by two encoders, with three (3) of the four (4) parity bits generated for that input bit, by one encoder .

9 are selected based on the previously described design principles to meet the specified code rate.

Next, each of the three (3) code triads of Table 3 is combined with the puncturing patterns 910, 920, 930, and 940 of the four (4) of FIG. 9 to obtain, for example, a fixed interleaver depth of 512 Generates twelve (12) possible turbo codes to be evaluated with the simulated data shown in Figures 10-12.

Next, the performance of the twelve (12) turbo codes is used to select three (3) best turbo code candidates for a more detailed evaluation. Based on the simulation results shown in Figures 10 to 12, the best turbo code candidates for the three (3) of twelve (12) are:

A configuration code having a turbo code A-puncturing pattern second;

A configuration code having a turbo code B-puncturing pattern first; And

A configuration code third with a turbo code C - puncturing pattern first (the puncturing pattern is selected from the patterns 910, 920, 930 and 940 of FIG. 9).

Next, one of the turbo codes of codes A to C is selected for an appraisal to demonstrate that the puncturing pattern is good at different interleaver depths using simulated data of various ancillary interleaver frame sizes.

To confirm the basic methodology, the performance of the turbo code based on the configuration code first (e.g.) is simulated for each frame size of 1024, 2048 and 3072 bits. Sample results for the BER / FER performance of 1023 bits of code # 1 are shown in FIG. 13, which confirms the basic methodology.

Next, FIG. 14 shows the BER / FER performance of the simulated data using three rate 1/4 turbo code candidates A through C with a 512 bit interleaver depth. Coherent results are also achieved at interleaver sizes 1024, 2048 and 3072 bits.

Next, in the resulting simulations and similar plots as in Fig. 14, a rate 1/4 turbo code candidate is selected from among the candidate turbo codes A through C providing the overall best performance of all interleaver depths do. In the case of rate 1/4 turbo codes, optimization based on BER performance provides results different from optimization based on FER performance. For simulated data, Turbo code B has the best overall FER performance, and Turbo code C provides the best overall BER performance. Figure 15 shows the performance of a Turbo code C compared to other puncturing schemes.

As such, the FER-optimized turbo code B is chosen as the basis for the design because FER performance is often a more important criterion for data services. On the other hand, the turbo code A may be punctured to provide the same universal turbo code that was previously identified optimally for rate 1/3 (by puncturing all parity bits from the n ₂ (D) polynomial). That is, turbo code A is the preferred choice for forward link rate 1/4 code to have a single universal mother code that implements all different code rates.

Although current third generation CDMA encoding is primarily for rate 1/4 channel encoding for reverse link, rate 1/3 and rate 1/2 channel coding may be required for some highest rate data channels. A universal turbo code for rate 1/4, rate 1/3 and rate 1/2 can be designed where the underlying configuration code is the same and only the puncturing pattern used is different. The method for generating the upper rate turbo code from the rate 1/3 configuration code is as follows.

Rate 1/3 turbo code optimized to 1/4 rate

Using the rate 1/4 optimized turbo code, i.e., the configuration code derived from the turbo code B, rate 1/3 and rate 1/2 turbo codes can be designed to be compatible therewith. Therefore, the configuration code second (from code B) is used as a basis.

Figure 16 shows seven (7) basic puncturing patterns that can be used to generate rate 1/3 turbo codes and four (4) basic puncturing patterns to generate rate 1/2 turbo codes. The seven (7) rate 1/3 patterns 1602 to 1614 in the block diagram 1600 correspond to two (2) encoder puncturing block patterns 1616 and 1618, successive information puncturing bit patterns 1620, 1626, and four (4) corresponding row parity bit puncturing patterns 1622, 1624, 1628, and 1630. As before, the pattern (" 1111 ") shown in row 1620 always transmits all information bits from encoder 1. The pattern (" 0000 ") in row 1626 punctures the information bits entering by the second encoder encoder. This is because it is not necessary to transmit the information bits twice. Four (4) rate 1/2 puncturing patterns 1 to 4 shown in FIG. 16 as reference numerals 1640, 1642, 1644 and 1646 follow the same convolution.

Next, the BER and FER performance of all possible 1/3 turbo codes simulated with the preferred configuration code second to the interleaver depth 512 in FIG. 17 are compared.

The best two (2) patterns are then selected for consideration. Next, the performance of these two (2) patterns is compared at the interleaved depth (1024, 2048 and 3078) bits.

For example, in FIG. 17, which illustrates a rate 1/3 puncturing pattern of 512 bits, patterns 2 and 5 are selected based on curves 1710 and 1720, respectively, having the best and next best overall relative FER.

Pattern 2 is then selected to have the best performance across the various interleaver depths from a side-by-side simulation similar to that of FIG. 17 at a side-by-side interleaver size for 1024, 2048 and 3072 bits.

Rate 1/2 turbo code optimized for rate 1/4

The rate 1/2 code may also be optimized with a lower rate code for similar compatibility as described above. 18 compares the BER and FER simulated performance of all rate 1/2 turbo codes at a 512 bit interleaver depth. Fig. 18 is generated using the puncturing pattern 4 and the configuration code 2 shown in Fig. 16 (4) for the rate 1/2 turbo code. Patterns 1 and 4 are determined to be best based on simulated curves 1810 and 1820 for FER performance.

A similar simulation curve for FIG. 18 is performed for patterns 1 and 4 for interleaver depths of 1024, 2048, and 3072 bits, as in the case of rate 1/3 optimized at rate 1/4. Based on the resulting performance / curves, pattern 1 is adjusted to be the best pattern for FER performance.

Preferred universal turbo codes optimized for rates 1/2 and 1/3

19 is a block diagram for a configuration encoder optimized in accordance with the method previously described for turbo code rates 1/2 and 1/3. Figure 20 shows a block diagram for a corresponding turbo code punctured at a rate of 1/4.

A number of modular adders 1904,1908,1920,1910 (1902), which are hardwired to receive information bit stream X (t) 1902 at switch 1922 and to represent two (2) molecular polynomials and one denominator polynomial, , 1914, 1918, 1919) and some shift registers (1906, 1912 and 1916).

In Fig. 19, the denominator polynomial d (D), represented by octal number 13, is hardwired by a return feedback connection to modulo adders 1920 and 1904. [ Before computing, the three shift registers 1906, 1912, and 1916 are first set to zero.

The first molecular polynomial on the denominator polynomial expressed as " 1101 " is the result of the modulator adder 1920 and X (t) (1992) to produce the first bit W (t); A modulo sum (first bit) of shift register 1906 and W (t) from modulator adder 1908; Another zero bit (third bit) indicated by the absence of a connection to register 1912; And to return the output Y _o (t) by combining the modulo sum (fourth bit) of the other register 1916 and the result of the modulo adder 1908 from the modulo adder 1998. The result is Y _o (t) = W (t) + S _o (t) + S ₂ (t).

19, the second molecular polynomial on the denominator polynomial expressed as " 1111 " combines X (t) 1902 with the result of adder 1920 to produce a first bit W (t); Adds the contents of the subsidiary register 1906 to W (t) with the contents of modulo adder 1910 (second bit); Adding the contents of register 1912 to the result of adder 1710 along with modulo adder 1914 (third bit); And, a hard-wire is to be returned to the modular adder 1919 (fourth bit) and the output Y ₁ by adding the contents of the adder 1914 is the register 1916 to the other with the result of (t). The result is Y ₁ (t) = W (t) + S _o (t) + S ₁ (t) + S ₂ (t).

In Fig. 19, the denominator polynomial connection sums the results of registers 1902 to 1906 in adder 1920 and then adds X (t) to these adders 1904. Thus, if modular adder 1904 is a value W (t), register 1906 holds S ₀ (t), register 1912 holds S ₁ (t), register 1916 holds S ₂ (t), adder 1904 holds W (t) = X (t) + S ₁ (t) + S ₂ (t); _{Y 0 (t) = W (} t) + S o (t) + S 2 (t); And Y ₁ (t) = W (t) + S ₀ (t) + S ₁ (t) + S ₂ (t). Thus, additions are accumulated.

If the two bits are different, the result of the modulo adder is "1" and if the two bits are equal, "0". Output Y ₀ (t) represents the output from numerator Polynomial No. 1 and the denominator polynomial. Output Y ₁ (t) represents a second numerator polynomial and a denominator polynomial.

Initially, S ₀ = S ₁ = S ₂ = 0, and the values of registers 1906, 1912, and 1916 shift left to right after each clock cycle is incremented. Therefore, S ₀ (t + 1) = W (t); S ₁ (t + 1) = S ₀ (t) and S ₂ (t + 1) = S ₁ (t).

For example, the optimal puncturing matrix shown in FIG. 20 shows " 1 " for transmitted bits and " 0 " for punctured bits. 20 illustrates an encoder 2000 having an incident bit X (t) and an encoder 2006 for generating an output bit X ^' (t), parity bits Y ₀ ¹ (t) and Y ₁ ¹ (t) Lt; RTI ID = 0.0 > X ^' (t) < / RTI > Any of the interleaved bits X ^' (t) is processed at the rate 1/4 encoder 2004, only at the second rate 1/4 encoder 2006. Block 2010 shows a puncturing pattern matrix.

More complex puncturing patterns may be used to achieve different possible coding rates. For example, it is possible to achieve rates 2/8 and 4/9 against turbo codes optimized for rates 1/2 and 1/3, and to optimize rates < RTI ID = 0.0 > An optimal puncturing pattern can be selected to achieve rates 2/9 and 3/8 for the turbo code.

Similar to FIG. 9, the block diagram for the optimal turbo code rate 3/8 uses the rate 1/3 mother configuration code of FIG. An encoder for the configuration code of FIG. 20 is shown in FIG. The puncturing pattern of the rate 3/8 turbo code shown in Figure 21 punctures 1 out of every 6 bits associated with the first molecular polynomial from the two encoders to produce a rate 3/8 turbo code.

The second pattern is an extension of the first pattern such that both constituent encodings all have the same rate, 6/11. The expansion pattern copies the same pattern (matrix) for the bits of the other three (3), but moves the position of one transmission bit from one encoder to the other. That is, "1" in one encoder while flipping "0" in another encoder in the similar position.

Figure 22 shows the performance of these patterns at an interleaver depth of 512 bits. Based on these and similar curves at the 1024, 2048 and 3072 interleaver depths, pattern 2 is selected to implement a rate 3/8 turbo code.

FIG. 23 shows a puncturing puncture selected for a rate 4/9 turbo code used with the mother of the code of FIG. Similarly, the second pattern is the first extension, with both configuration codes having the same rate, i.e. 8/13.

Fig. 24 shows a corresponding performance curve. Pattern 2 is selected to implement a rate 4/9 turbo code.

As such, one exemplary turbo code design optimized for the turbo code rates 1/2 and 1/3, and universal for all interleaved depths, is the preferred generator polynomial d (D) = 1 + D ² + D ³ , n ₁ (D) = 1 + D + D ³ , and n ₂ (D) = 1 + D ² + D ³ .

A preferred puncturing pattern for various code rates is as follows:

1) Rate 1/4 - alternately puncturing parity bit n ₁ from one encoder and n ₂ from the same encoder.

2) rate 1/3 - puncturing parity bit n ₂ from two encoders

3) Rate 1/2 - puncturing parity bits n ₂ and alternately ringham puncture parity bits n ₁ from the two encoders.

4) Rate 3/8 - Punctures parity bit n ₂ and punctures one of every 6 parity bits n ₁ from two encoders.

5) Rate 4/9 - Punctures parity bit n ₂ and punctures 3 equally among every 8 parity bits n ₁ from two encoders.

The simplified version of this code is a universal turbo code design consisting of two constituent encoders with generator polynomials d (D) = 1 + D ² + D ³ and N ₁ (D) = 1 + D + D ³ . (The third polynomial n ₂ (D) is not used, so no corresponding output is generated, and the encoder block diagram is simplified by eliminating the corresponding connection). This universal turbo code design is 1 / 3, and so on. A corresponding preferred set of puncturing patterns is as follows:

1. Rate 1/3 - No Puncturing

2. Rate 1/2 - alternately puncturing parity bit n ₁ from two encoders;

3. Rate 3/8 - puncturing one of every 6 parity bits n ₁ from two encoders; And

4. Rate 4/9 - uniformly punctures 3 out of every 8 parity bits n ₁ from the two encoders.

A preferred universal turbo code optimized for code rate 1 /

A basic block diagram for a preferred configuration encoder is shown in Fig.

26 is an encoder block diagram for a preferred rate 1/4 turbo code. In this case, the second parity bits are alternately punctured by the two constituent encoders. The preferred puncturing pattern described in the previous section is then applied to generate rate 1/3 and rate 1/2 turbo codes. Different rates can also be supported by identifying additional puncturing patterns. This is illustrated by considering rates 2/9 and 3/8.

Figure 27 shows the puncturing pattern for the 2/9 reverse link code. The different patterns of the three (3) are compared with the performance curves of FIG. 28 by, for example, similar curves as described in Appendix A illustrating the performance of various frame interleaver sizes. From pattern 2 FER curve 2810 and pseudo-curve, the pattern second is selected as the optimal FER pattern for rate 2/9.

Next, FIG. 29 shows six (6) initial check puncturing patterns for optimizing the rate 3/8 reverse link code. The performance of these patterns is simulated with a fixed interleaver length of 512 bits. Based on this simulation, Pattern 5 and Pattern 6 are selected as optimal puncturing patterns for incidental review.

The two or more extension patterns 7 and 8 of the patterns 5 and 6 copy the same pattern for the other three information bits, but move one of the transmission bits in the parity sequence from one encoder pattern to another. This extension allows all configuration encoders to have the same rate, 6/11 in each encoder.

FIG. 30 shows exemplary performance curves of four (4) candidate puncturing patterns 5,6,7 and 8 for a rate 3/8 turbo code. Based on these results, the pattern 8 FER curve 3010 and a pseudo curve such as that shown in Appendix A, for example, demonstrate that pattern 8 is the optimal puncturing pattern for the rate 3/8 turbo code. Thus, one preferred universal turbo code design optimized for rate 1/4 is the polynomial d (D) = 1 + D + D ³ , n ₁ = 1 + D ² + D ³ , and n ₂ = 1 + D + D ² + D ³ .

The following puncturing pattern is the FER performance for the most optimal pattern and the most commonly used turbo code rate as discussed previously for the turbo code rate 1/4, where n ₁ is the output associated with the first molecular polynomial represent the bits, n ₂ represents output bits associated with a second numerator polynomial.

1) Rate 1/4 - alternately puncturing parity bit n ₂ from both constituent encoders.

2) Rate 1/3 - Punctures parity bit n ₁ from both configuration encoders.

3) Rate 1/2 - puncturing parity bit n ₂ and every other parity bit n ₁ from both encoders.

4) Rate 2/9 - Puncturing every one of every four parity bits from n ₁ from both encoders.

5) Rate 3/8 - Puncturing one of the parity bits n ₁ and every six parity bits n ₂ .

These preferred puncturing patterns are also cyclically shifted without affecting performance. Cyclically shifted patterns are equivalent.

Turbo coding FEC scheme for CDMA data services

The preferred set of universal turbo codes described in the present invention provides a flexible high performance channel code that is well suited for advanced data communication systems that require a variety of low speed and high speed data services. Such preferred universal turbo codes enable different turbo encoding scheme techniques to meet certain conditions of a particular data communication system.

As a first example, one of the following two FEC schemes is suitable and is recommended for synchronous CDMA data communication networks (such as a third generation CDMA 2000 system under development).

1) a preferred universal turbo code optimized at code rates 1/2 and 1/3 with a subset of associated preferred puncturing patterns on the forward link, and a subset of associated preferred puncturing patterns on the reverse link An optimized preferred universal turbo code; And

2) A preferred universal turbo code optimized at code rates 1/2 and 1/3 with a subset of the preferred preferred puncturing patterns associated on forward and reverse links.

As a second example, one of the following two FEC schemes suits and is recommended for asynchronous CDMA data communication networks (such as third generation UTRA systems currently in development in Europe and Asia).

1) a preferred universal turbo code optimized at code rates 1/2 and 1/3 with a subset of associated puncturing patterns on forward and reverse links;

2) a preferred universal turbo code optimized with a code rate of 1/4, as described above, with a subset of the preferred preferred puncturing patterns on forward and reverse links; And

3) Simplified version of the universal turbo code, as described above, with a subset of the desired preferred puncturing patterns on the forward and reverse links.

The choice of implementation choices depends on the expected good code rate, minimum code rate, and implementation complexity constraints, as well as other system conditions. Of course, additional puncturing patterns may be designed in accordance with the teachings of the present invention to provide different turbo coding rates.

Other variations

Universal turbo codes for high-speed data services are particularly suitable for third-generation CDMA cellular mobile radio systems, but can be readily applied to other systems.

Known variations, such as frame-oriented convolutional coding (FOCTC), may also be used for the preferred universal configuration code and universal turbo codes of the present invention. The design methodology for selecting universal configuration codes and universal turbo codes can also be applied to alternate turbo code structures such as those involved in more than two constituent encoders and those involved in serial abbreviations instead of or in parallel.

The exemplary preferred puncturing patterns described in the present invention can be modified or modified in various ways by those skilled in the art. For example, a cyclic shift of the preferred puncturing pattern provides performance substantially equivalent to the preferred puncturing pattern described in the present invention. In addition, certain data communication systems may require different and ancillary puncturing patterns to support rate matching. These puncturing patterns can be designed in accordance with the teachings of the present invention.

Set of rate-compatible universal turbo codes

According to the present invention, an AWGN channel for various code rates and various interleaver depths can be provided by transmitting the same bit position as a given higher rate turbo code set is transmitted by the same set of other arbitrary lower rate turbo codes To provide a set of uniformly optimized or nearly optimal rate-compatible turbo codes.

In particular, one embodiment includes a set of rate-compatible turbo codes of various code rates of 1/5, 1/4, 1/3 and 1/2 and various interleaver depths of 512 to 3072 bits.

Other preferred embodiments provide multiple sets of turbo codes that are optimized under different conditions that allow the system designer to compromise performance versus diversity information (and thus complexity) or vice versa. The selection of the rate-compatible turbo code set is based on the universal configuration encoder described below.

The universal configuration encoders of the present invention provide optimal or near optimal performance over a large range of code rates and interleaver depths. Different optimization criteria, such as reverse link or forward link dominance and degree of diversity, result in different sets of rate-compatible turbo codes.

The rate-compatible code set is particularly suited for hybrid ARQ schemes applied to satellite broadcast and telephony.

Some preferred embodiments have different sets of rate-compatible codes based on different universal configuration codes and different rates of puncturing patterns optimized according to different design criteria.

In accordance with the overall methodology of the present invention, four (4) different preferred rate-compatible turbo code sets are described in the present invention. The first two (2) sets are optimized for high rate turbo codes where higher rates dominate. The second two (2) sets are optimized for the lower rate code where the lower rate prevails. These sets are hereinafter referred to as sets A-D.

The first preferred set is derived from the best universal configuration code of rate 1/2.

The second set is derived from a rate 1/2 of universal configuration code and also from a rate 1/3 of another best configuration code.

The first set, "set A", has two generator polynomials, while the second set, "set B", has three generator polynomials, two of which are common to "set A". As such, " set B " is optimally compatible with " set A ", reducing the amount of design changes for encoding and decoding. As before, a third polynomial is needed for the side encoder parity bits of the turbo code less than 1/3 rate.

The second set " set B " includes " set A " and also extends the family of turbo codes for rate 1/5 or more.

The third and fourth preferred rate-compatible turbo code sets are optimized for the lower rate, especially rate 1/4. &Quot; set C " and " set D " each use three generator polynomials that are the same as those in " set B "

Rate-compatible set derived from rate 1/2 universal configuration code: set A (rate 1/3, 1/2)

From Table 2, it is determined that the rate 1/2 configuration code providing the best overall performance is an octet pair 13-15. Thus, this configuration code pair is used as the mother configuration code pair for set A. [

The rate-compatible set A has a generator polynomial corresponding to octal pair 13-15, wherein the denominator polynomial is 1 + D ² + D ³ (octal 13) and the molecular polynomial is 1 + D + D ³ (8 The number 15).

The puncturing patterns are designed such that all bits transmitted by the rate of one-half code (or more) of the set are also transmitted by the rate 1/3 code or the low rate code set.

Exemplary preferred patterns illustrated by simulation and design principles are as follows:

1) For rate 1/3, there is no puncturing,

2) For rate 1 /, the parity bits are alternately punctured between encoders (note that in this case there is no second molecular polynomial encoding)

31 shows a block diagram for a set A configuration encoder. 31, modular adders 3104 and 3108 (connected to shift register 3106) and modular adder 3116 (connected to shift register 3114) are used for a molecular polynomial representing octal 15 or binary 1101 And an encoding device.

The modulo adders 3104, 3108, 3112, and 3116 add the contents of shift registers 3106, 3110, and 3114 and X (t) in a manner similar to that of FIG.

The simulated performance of rate 1/2 turbo code and rate 1/3 turbo code is based on the assumption that the 8-state convolutional code designed in the present invention (with 8 decoder iterations) is the best 256- (BER) of about 1 / 6dB at rate 1/2 and about 2.0dB at rate 1/3, for rate converters, state rate codes, and the like.

As such, the turbo code in set A is compared to the performance for the best known 256-state convolutional code when simulated for critical performance parameters.

Rate-compatible set derived from universal configuration code of rate 1/3: set B (rate 1/2, 1/3, 1/4, 1/5)

An output power polynomial is required for the rate-compatible generator polynomial of " set B " derived from the best configuration code of rate 1/3, as in the case of determining a universal configuration code of rate 1/3.

Thus, the second best individual rate 1/2 configuration code is selected from Table 2. As before, this method results in two (2) octal pairs overlapping. The octal pair, octal 13-15 and octal 13-17 all provide uniformly superior performance. By combining the pairs of two (2) together we provide three (3) generator polynomials with triplets octal 13-15 / 17. D ² + D ³ (octal number 13), the first molecular polynomial is 1 + D ² + D ³ (octal number 15), and the second molecular polynomial is 1 + D + D ² + D ³ (17). The preferred design for set B has all of these interleaver depths, and these generator polynomials for the turbo code rates 1/2, 1/3, 1/4 and 1/5.

In Set B, the rate 1/3 and rate 1/2 turbo codes generated from the rate 1/3 configuration encoders are the same 1/3 and 1/2 turbo codes generated from the universal rate 1/2 configuration encoder and set A And the set B is preserved.

Puncturing patterns are designed such that all bits transmitted with any higher rate turbo code of set B are also transmitted at any lower code rate of set B. [

Exemplary preferred patterns and design principles demonstrated by the simulations are as follows:

1) Rate 1/5 - no puncturing;

2) Rate 1/4 - alternately puncturing the second molecular parity bit n ₂

3) rate 1/3 - always puncturing the second molecular parity n ₂

4) Rate 1/2 - always punctures the second molecular parity bit n ₂ and always punctures the first molecular parity bit n ₁

For the rate 1/4 pattern, weak arms of the two (2) output arms of the configuration encoder are alternately punctured.

For the rate 1/3 pattern, the weaker output of the two (2) constituent encoder outputs is alternately punctured.

At rate 1/2, the weaker output of the two (2) constituent encoder outputs is always punctured for all of the encoders, and the sen output is punctured.

Optimized rate-compatible set with low turbo code rates

If the upper code rate is dominant mode turbo code, set B is the preferred design choice when stringent rate-compatibility is required at all code rates.

Turbo code set C and set D all optimized with lower turbo code rates are useful when rate-compatibility between the lower rate and higher rate turbo codes is not needed.

Based on the candidate configuration codes listed in Table 3, which are selected based on the results of Table 2 as previously described, the optimal turbo codes for rates 1/4 and 1/5 are selected.

Is the basis for the configuration code first or octet set A in Table 3. However, by removing the condition that the rate 1/4 puncturing pattern should be that of the rate 1/2 or 1/3 code, when the lower rate is not used with the higher rate, the newly optimized 1/4 turbo code To obtain three (3) mother-turbo code triads of each of Table 3, each having four (4) different puncturing patterns are considered.

As described above, the turbo codes A, B, and C are found to be optimal from the respective performance curves 1010, 1110, and 1210 of FIGS. 10, 11, and 12, respectively.

As before, these puncturing patterns are also verified in other interleavers by simulating the performance of the turbo codes based on mother code triplet 1 for the other interleaver frame sizes of 1024,2048, and 3072. Figure 13 shows the sample results of the simulation and confirms the basic methodology at 1024 bits.

Next, FIG. 14 shows samples corresponding to triplet performance matching the selected puncturing pattern at 512 bits. From Fig. 14 and similar results for different interleaver sizes, the best overall BER performance of all simulated interleaver depths is used as the final design criterion to determine the best candidates.

Rate-compatible set derived from rate 1/4 turbo code: set C (rate 1/5, 1/4, 1/3)

Turbo code set C implements code first and pattern first (turbo code C) from FIG. 9, according to a performance curve 1310 of FIG. 14 and a similar curve for other interleaver sizes.

Turbo-code set C is a table containing the denominator polynomial 1 + D + D ² + D ^3, the first molecule polynomial ^{_{n 1, 1 + D 2 +}} D 3, and the second molecule polynomial n _2, 1 + D + D ² 3 < / RTI > The optimal puncturing pattern from simulations consistent with the methodology as described previously is as follows:

1) Rate 1/5 - No puncturing

2) For rate 1/4 - alternately puncturing the second molecular polynomial,

3) For rate 1/3 - always puncturing the second molecular polynomial.

Rate-compatible set derived from rate 1/4 turbo code: set D (rate 1/5, 1/4)

Turbo code set D has a single configuration code for all interleaver depths and turbo code rates of 1/4 and 1/5.

The turbo code set D implements a code first having the pattern second (turbo code A) from Fig. 9 according to the performance curve 1420 of Fig. 14 and a similar curve of other interleaver size.

The set generator including a denominator polynomial ^{d, 1 + D + D 3} , the first molecule polynomial ^{_{n 1, 1 + D 2 +}} D 3, and the second molecule polynomial n _2, 1 + D + D ² + D ³ And has a polynomial expression.

The optimal puncturing pattern from the simulation, previously described and consistent with the methodology, is as follows:

1) Rate 1/5 - No puncturing

2) For rate 1/4 - alternately puncturing output 1/2.

The performance of a rate 1/4 FER-optimized turbo code with a selected interleaver depth of 512 to 3072 bits is compared to the convolutional code in sample drawing 32 and a similar study.

A more complex puncturing pattern may be used for convolutional coding to achieve any higher code rate of the base turbo code in each rate-compatible set.

For example, a rate of 1/2 or more, such as 5/12, may be achieved. With an appropriate choice of puncturing patterns, this can often be done without sacrificing error correction performance.

Application of rate-compatible turbo codes

An exemplary application of the rate-compatible turbo codes described in the present invention is for rate matching where the code rate is selected to match the available physical channel. In rate matching schemes, data services use the same basic encoding, but they can use the same physical channel, especially if the quality of the service description is different for different data services.

According to the present invention, different puncturing patterns can be selected to generate a code rate compatible with the physical channel. If the puncturing patterns are rate-compatible, the selection of the code rate need not be completed by a single decision unit at a single appropriate time. Instead, this determination can be distributed over time as well as over the decision unit. The turbo encoder first generates a coded output sequence corresponding to the lowest code rate to be supported by the system. For example, all possible parity bits will be initially output. Next, the initial puncturing will be performed by one puncturing unit, for example, in response to a quality-of-service (Qos) consideration for a given data service. In this scenario, a data service may not be able to provide the highest quality within the range, for example, where the highest quality within the range does not require the lowest possible code rate available in the system but requires some intermediate code rate, Lt; RTI ID = 0.0 > Qos < / RTI > The first puncturing unit removes the coded bits according to the puncturing pattern corresponding to the lowest rate to provide the highest quality within the Qos range of the data service. Unencoded data is output to the rest of the system for additional processing. In subsequent processing, it is determined to adjust the code rate higher for the message based on dynamic traffic management considerations. For example, to accommodate a message from a higher-priority data service, a physical channel with a smaller payload may be replaced, depending on the provisional need for the physical channel normally associated with that data service. The upper code rate is achieved by performing a second puncturing in accordance with the puncturing pattern associated with the new code rate. Since the puncturing pattern is rate-compatible, it is not necessary to reproduce the coded bits deleted by the first puncturing unit, and the second puncturing unit simply does not need puncturing of the higher rate not deleted by the first puncturing unit Deletes the bit specified by the pattern.

A second exemplary application of the rate-compatible turbo code described herein is an incremental redundancy scheme, such as error control based on the ARQ protocol. In these schemes, the turbo encoder first generates a coded output corresponding to the highest code rate available in the system. If the coded output is sent over a communication channel, the receiver may or may not be able to successfully decode the message. If the message is successfully decoded, the receiver typically sends a negative acknowledgment (NAK) to the transmitter requesting an auxiliary transmission to assist in decoding the packet. With rate-compatible channel encoding, the remainder of the encoded bits generated by one of the lower rate compatible encodings for that packet may be sent to increase the information available to the decoder of the receiver. The decoder performs decoding using the new information together with the original information received for the packet. The effect is whether the original packet was encoded as a subrate code. This process can be repeated until the packet is successfully decoded. By transmitting the redundant coded bits in each retransmission, the traffic load required for retransmission is greatly reduced.

Although the present invention has been described by specific embodiments and applications thereof, numerous modifications may be made by those skilled in the art without departing from the scope of the invention as set forth in the appended claims.

<Appendix>

Claims (17)

A set of rate-compatible Turbo codes derived from a universal constituent code that is optimized at a high code rate, the turbo code having compatible puncturing patterns, A method for processing data in a memory, Encoding the signals in the first and second encoders using the upper code rate and lower code rate and the universal best rate 1/2 configuration code, each of the first encoder and the second encoder having Generating a plurality of parity bits; Puncturing each of the plurality of parity bits in each encoder with a best puncturing pattern of the highest rate; And Puncturing each of the plurality of parity bits in the respective encoder with a best puncturing pattern of a subrate &Lt; / RTI &gt; 2. The method of claim 1 wherein the best rate 1/2 configuration code comprises a combination of polynomials 1 + D ² + D ³ (octal 13) and polynomial 1 + D + D ³ (octal 15) How to represent. 3. The method of claim 2, wherein one of the rate-compatible turbo codes in the set comprises a rate 1/2 turbo code and one of the puncturing is to alternately puncture the parity bits between the first and second encoders &Lt; / RTI &gt; 3. The method of claim 2, wherein one of the rate-compatible turbo codes in the set comprises a rate 1/3 turbo code, and one of the puncturing is to transmit all parity bits at the first and second encoders Lt; / RTI &gt; A method of processing data in a data service using a set of rate-compatible turbo codes derived from an optimal universal 1/3 configuration code, the turbo code having a similar configuration code and a compatible puncturing pattern , Encoding a signal having an optimal rate of 1/3 in the first and second encoders, each encoder generating a respective plurality of parity bits for each data bit; Puncturing the plurality of parity bits with the highest puncturing pattern of the highest rate; And Puncturing the plurality of parity bits with a best puncturing pattern of a subrate &Lt; / RTI &gt; The method of claim 5, wherein the configuration best rate 1/3 code polynomial ^{1 + D 2 + D 3,} (8 decimal 13), the polynomial 1 + D + D ³ (8 decimal 15), and a 1 + D + D ² + D ³ (octal number 17) (where D is a data bit). 6. The method of claim 5, wherein the set of turbo codes comprises a rate 1/5 turbo code, and at least one of the puncturing steps comprises transmitting all parity bits at the first and second encoders Way. 6. The method of claim 5, wherein the set of turbo codes comprises a rate 1/4 turbo code, and wherein at least one of the puncturing steps is performed between the first and second encoders, &Lt; / RTI &gt; 6. The method of claim 5, wherein the set of turbo codes comprises a rate 1/3 turbo code, and at least one puncturing of the puncturing step comprises selecting a group of the plurality of parity bits from the first and second encoders Comprising alternating puncturing. 6. The method of claim 5, wherein the set of turbo codes comprises a rate 1/2 turbo code, wherein at least one of the puncturing operations punctures a selected group of the plurality of parity bits at the encoders And alternately puncturing, in the encoders, another selected group of the plurality of parity bits. A rate-compatible turbo encoding method using a set of rate-compatible turbo codes, the set being optimized at a code rate of 1/4 and having turbo codes with different code rates and rate-compatible puncturing patterns As a result, Encoding a signal at the first and second encoders using a higher code rate and a lower code rate and a universal best rate 1/4 configuration code, wherein each of the first encoder and the second encoder comprises: Generating a plurality of respective parity bits for the bits; Puncturing each of the plurality of parity bits in each encoder with a best puncturing pattern of the highest rate; And Puncturing each of the plurality of parity bits in each encoder with the best puncturing pattern of the subrate &Lt; / RTI &gt; 12. The method of claim 11, wherein the rate-set of compatible turbo code represents the polynomial ^{1 + D + D 3, 1} + D 2 + D 3 and the first coupling of the + D + D ³ (D is a data bit), An associated rate-compatible puncturing pattern is provided, Transmitting all data, Alternately puncturing parity bits associated with polynomials 1 + D + D ³ ; And And puncturing a parity bit associated with polynomial 1 + D + D ³ for each encoder. 12. The method of claim 11, wherein the set of rate-compatible turbo codes comprises at least two turbo codes of different rates selected from a group of rates including 1/5 and 1/4, wherein the turbo codes are polynomials 1 + D + D ³ , 1 + D ² + D ³ and 1 + D + D ² + D ³ (where D is a data bit) An associated rate-compatible puncturing pattern is provided, Transmitting all data, and And puncturing the parity bit associated with polynomial 1 + D + D ² + D ³ alternately. An encoding system using a set of rate-compatible turbo codes derived from a best universal rate 1/2 configuration code, the set having a compatible puncturing pattern, The first and second encoders - each of the encoders - A plurality of shift registers, and A plurality of adders each coupled to a selected portion of the adders in a configuration corresponding to the best universal rate 1/2 configuration code; And Wherein the first and second encoders are configured to puncture a plurality of data outputs from each of the first and second encoders, the puncturing being based on a set of compatible puncturing patterns, Determined by code rate - &Lt; / RTI &gt; A set of rate-compatible turbo codes derived from an optimal universal rate 1/3 configuration code, the rate-compatible turbo codes having a similar configuration code and a compatible puncturing pattern, The first and second encoders - each of the encoders - A plurality of shift registers, and A plurality of adders each coupled to a selected portion of the adders in a configuration corresponding to the rate 1/3 configuration code; And Wherein the first and second encoders are configured to puncture a plurality of data outputs from the first and second encoders, the puncturing being based on a set of compatible puncturing patterns, Lt; RTI ID = 0.0 & &Lt; / RTI &gt; An encoding system using a set of rate-compatible turbo codes comprising a turbo code having a universal constituent code and a rate-compatible puncturing pattern for different code rates, The first and second encoders - each of the encoders - A plurality of shift registers, and A plurality of adders each coupled to a selected portion of a plurality of adders in a configuration corresponding to the universal configuration code; And Wherein the first and second encoders are configured to puncture a plurality of data outputs from the first and second encoders, the puncturing being based on a set of compatible puncturing patterns, Lt; RTI ID = 0.0 & &Lt; / RTI &gt; A set of rate-compatible turbo codes optimized with a high code rate, the set derived from the best universal configuration code of rate 1/2 compatible with the super code, the turbo code having a compatible puncturing pattern In the method, Selecting a group of candidate mother code pairs having primitive irreducible polynomials based on code pair checking and diversity, said code pair checking comprising the steps of: determining a fixed interleaver length Simulating the relative bit error rate (BER) performance of rate 1/2 and 1/3 turbo codes; Measuring a relative signal-to-noise ratio loss of a signal after a plurality of encodings for each candidate pair at a plurality of different interleaver depths and two different turbo code rates, each of the plurality of encodings including a candidate pair, an interleaver depth and rate Having different combinations of; Selecting a best candidate based on the best relative signal to noise ratio loss from the measurement; And Selecting, for each of the at least one rate-compatible turbo code in the set, a best puncturing pattern of at least one low rate and one high rate for the best candidate pair, Selects transmission of any parity bits selected for transmission by the at least one low rate pattern of the set, &Lt; / RTI &gt;