Interleaver Design Method for Turbo Codes Based on Genetic Algorithm

This paper describes a new interleaver construction technique for turbo code. The technique searches as much as possible pseudo-random interleaving patterns under a certain condition using genetic algorithms(GAs). The new interleavers have the superiority of the S-random interleavers and this interleaver construction technique can reduce the time taken to generate pseudo-random interleaving patterns under a certain condition. The results obtained indicate that the new interleavers yield an equal to or better performance than the S-random interleavers. Compared to the S-random interleaver, this design requires a lower level of computational complexity. Key words interleaver - Turbo codes - genetic algorithm CLC number TN 911. 22 Foundation item: Supported by the National Natural Science Foundation of China (60372057) and the Key Open Laboratory on Information Science and Engineering of Railway Transportation Ministry of Beijing Jiaotong University of China (KLISAE-0103)Biography: Tan Ying (1963-), female, Associate professor, Ph. D, research direction: error control coding, analysis and design of wireless communication system.

Puncturing Period on the Performance of Punctured Turbo Codes

Puncturing is the predominant strategy to construct high code rate turbo codes. Puncturing period is a crucial parameter influencing the performance of punctured turbo codes (PTC). Here we developed a new puncturing scheme of turbo codes, with which the puncturing period on the performance of PTC is studied. Consequently, suggestions on selecting the puncturing period are proposed.

A Self-Terminated Interleaver Design for Turbo Codes

Turbo codes can achieve excellent performance at low signal-to-noise ratio (SNR), but the performance can be severely degraded if no trellis termination is employed. This paper proved that if trellis termination bits were appended to RSC1, trellis of RSC2 could be terminated by designing the interleaver properly, consequently, derived the designing condition of such self-terminated interleaver (STI). Then we presented an algorithm of implementing a kind of STI, which could terminate RSC2 as well on condition that the RSC1 was terminated. We verified the performance of STI for turbo codes by simulation, and the simulation results showed that turbo codes with STI outperformed interleavers that could not terminate RSC2 as well.

Turbo Codes with Hybrid Interleaving Mode

In the investigation of turbo codes, either random interleavers or structured interleavers are used. Combined two kinds of interleavers in one turbo encoder, a hybrid interleaving mode is proposed in this paper. Computer simulations show that the performance of turbo codes with the hybrid interleaving mode is better than that with the typical interleaving mode.

Log Likelihood Ratio-Based Relaying for Distributed Turbo Codes

A distributed turbo codes（ DTC） scheme with log likelihood ratio（ LLR）-based threshold at the relay for a two-hop relay networks is proposed. Different from traditional DTC schemes,the retransmission scheme at the relay,where imperfect decoding occurs,is considered in the proposed scheme. By employing a LLR-based threshold at the relay in the proposed scheme,the reliability of decoder-LLRs can be measured. As a result,only reliable symbols will be forwarded to the destination and a maximum ratio combiner（ MRC） is used to combine signals received from both the source and the relay. In order to obtain the optimal threshold at the relay,an equivalent model of decoderLLRs is investigated,so as to derive the expression of the bit error probability（ BEP） of the proposed scheme under binary phase shift keying（ BPSK） modulation. Simulation results demonstrate that the proposed scheme can effectively mitigate error propagation at the relay and also outperforms other existing methods.

Understanding turbo codes: A signal processing study

In this paper,we study turbo codes from the digital signal processing point of view by defining turbo codes over the complex field.It is known that iterative decoding and interleaving between concatenated parallel codes are two key elements that make turbo codes perform significantly better than the conventional error control codes.This is analytically illustrated in this paper.We show that the decoded noise mean power in the iterative decoding decreases when the number of iterations increases,as long as the interleaving decorrelates the noise after each iterative decoding step.An analytic decreasing rate and the limit of the decoded noise mean power are given.The limit of the decoded noise mean power of the iterative decoding of a turbo code with two parallel codes with their rates less than 1/2 is one third of the noise power before the decoding,which can not be achieved by any non-turbo codes with the same rate.From this study,the role of designing a good interleaver can also be clearly seen.

Improving the Structure of Multiple Dimension Turbo Codes Using Multiple Identical Component Encoders

In this paper,we propose an improved structure for M-dimension ( M ≥ 2)turbo codes using M identical component encoders. The presented structure only applies single recursive convolutional encoder to encode M interleaved versions of infor-mation sequence and single tail sequence to operate termination. For the commonly used two-dimension (M = 2) turbo codes,two cascade soft input soft output (SISO) decoders are detailed to de-code the corresponding codes. With the two cascade SISO decod-ers,this coding structure obviously outperforms traditional turbo codes at high code rates,especially,about 0.3 dB gain can be ob-tained at code rate 0.9 in additive white Gaussian noise channel with quadrature phase shift keying modulation. This makes the proposed coding structure very attractive for future radio commu-nication systems with high throughput requirements.

An Improved S-Random Interleaver Design for Turbo Code Based on Chaos Model

A new method to design interleaver based on Henon chaos model is presented. The designed interleaver is with rather random behavior. Experimental results show that the proposed S-henon interleaver make a magnitude of im provement in bit error rate （BER） performance by 0.4 dB compared with the S-random interleaver for AWGN channel respectively. The S-henon interleaver may be adapted to 3G mobile communication systems.

Turbo decoding using two soft output values

It is well known that turbo decoding always begins from the first component decoder and supposes that the apriori information is '0' at the first iterative decoding. To alternatively start decoding at two component decoders, we can gain two soft output values for the received observation of an input bit. It is obvious that two soft output values comprise more sufficient extrinsic information than only one output value obtained in the conventional scheme since different start points of decoding result in different combinations of the a priori information and the input codewords with different symbol orders due to the permutation of an interleaver. Summarizing two soft output values for erery bit before making hard decisions, we can correct more errors due to their complement. Consequently, turbo codes can achieve better error correcting performance than before in this way. Simulation results show that the performance of turbo codes using the novel proposed decoding scheme can get a growing improvement with the increment of SNR in general compared to the conventional scheme. When the bit error probability is 10-5 , the proposed scheme can achieve 0.5 dB asymptotic coding gain or so under the given simulation conditions.

Design of concatenated turbo-SPC coded space-time systems

Multiple antenna wireless systems can provide larger channel capacity and enable spatial diversity to combat fading. In this paper we conduct an investigation into the design of coded space-time system obtained by serially concatenating channel code module and space-time code module with an interleaver in between. As an example, the system is constructed by employing low decoding complexity turbo-SPC （single parity check） code as outer module and linear complex field space-time code as inner module, which achieves full diversity and lossless equivalent channel capacity. Simulation results prove that our designed system performs well and it only loses 0.8 dB from multiple-input multiple-output （MIMO） capacity at BER = 10^-5 in the case of information bit length 6048. Compared with turbo code-based systems, it also has lower error floor.

A reordered first fit algorithm based novel storage scheme for parallel turbo decoder

In this paper we discuss a novel storage scheme for simultaneous memory access in parallel turbo decoder. The new scheme employs vertex coloring in graph theory. Compared to a similar method that also uses unnatural order in storage, our scheme requires 25 more memory blocks but allows a simpler configuration for variable sizes of code lengths that can be implemented on-chip. Experiment shows that for a moderate to high decoding throughput （40-100 Mbps）, the hardware cost is still affordable for 3GPP＇s （3rd generation partnership project） interleaver.

New Near Shannon Limit Codes: Zigzag Codes and Concatenated Zigzag Codes

This paper introduces a family of error correcting codes called zigzag codes. A zigzag code is described by a highly structured zigzag graph. Due to the structural properties of the graph, very low complexity soft in, soft out decoding rules can be implemented. We present a decoding rule, based on the Max Log APP(MLA) formulation, which requires a total of only 20 addition equivalent operations per information bit per iteration. Simulation of a rate 1/2 concatenated zigzag code with four constituent encoders with interleaver length 65536 yields a bit error rate (BER) and of 10 5 at 0.9 dB and 1.4 dB away from the Shannon limit by optimal (APP) and low cost sub optimal (MLA) decoders, respectively.

Low-Complexity Optimization Algorithm for Irregular Low-Density Parity-Check Codes

A low-complexity algorithm is proposed in this paper in order to optimize irregular low-density parity-check(LDPC)codes.The algorithm proposed can calculate the noise threshold by means of a one-dimensional density evolution and search the optimal degree profiles with fast-convergence differential evolution,so that it has a lower complexity and a faster convergence speed.Simulation results show that the irregular LDPC codes optimized by the presented algorithm can also perform better than Turbo codes at moderate block length even with less computation cost.

Optimization of Mapping Rule of Bit-Interleaved Turbo Coded Modulation with 16QAM

Optimization of mapping rule of bit-interleaved Turbo coded modulation with 16 quadrature amplitude modulation (QAM) is investigated based on different impacts of various encoded bits sequence on Turbo decoding performance. Furthermore, bit-interleaved in-phase and quadrature phase (I-Q) Turbo coded modulation scheme are designed similarly with I-Q trellis coded modulation (TCM). Through performance evaluation and analysis, it can be seen that the novel mapping rule outperforms traditional one and the I-Q Turbo coded modulation can not achieve good performance as expected. Therefore, there is not obvious advantage in using I-Q method in bit-interleaved Turbo coded modulation.

Pragmatic Approach to Adaptive Turbo Coded Modulation

This paper presents a pragmatic adaptive scheme for TuCM over slowly fading channels. The adaptive scheme employs a single turbo coded modulator composed of a variable-rate turbo encoder and a variable-rate variable-power MQAM for all fading regions, so it has an acceptable complexity to implement. The optimal adaptive TuCM scheme is determined subject to various system constraints. Simulations have been performed to measure the performance of the scheme for different parameters. It is shown that adopting both the turbo coded modulator and the transmit power achieves a performance within 2.5 dB of the fading channel capacity.

Performance analysis of adaptive turbo coded modulation with time delay

The method of data fitting is applied to obtain the BER expression for turbo coded modulation, and a fitting mathematical model is proposed, which resolves the problem that there is no exact BER expression for turbo coded modulation in performance analysis. With the time delay consideration, the performance of BER of adaptive turbo coded modulation is analyzed and simulated. The results show that adaptive turbo coded modulation is very sensitive to time delay. In order to meet the target BER requirement, the total time delay should be less than 0 001/f D.

SP-DSTS-MIMO Scheme-Aided H.266 for Reliable High Data Rate Mobile Video Communication

With the ever growth of Internet users,video applications,and massive data traffic across the network,there is a higher need for reliable bandwidth-efficient multimedia communication.Versatile Video Coding(VVC/H.266)is finalized in September 2020 providing significantly greater compression efficiency compared to Highest Efficient Video Coding(HEVC)while providing versatile effective use for Ultra-High Definition(HD)videos.This article analyzes the quality performance of convolutional codes,turbo codes and self-concatenated convolutional(SCC)codes based on performance metrics for reliable future video communication.The advent of turbo codes was a significant achievement ever in the era of wireless communication approaching nearly the Shannon limit.Turbo codes are operated by the deployment of an interleaver between two Recursive Systematic Convolutional(RSC)encoders in a parallel fashion.Constituent RSC encoders may be operating on the same or different architectures and code rates.The proposed work utilizes the latest source compression standards H.266 and H.265 encoded standards and Sphere Packing modulation aided differential Space Time Spreading(SP-DSTS)for video transmission in order to provide bandwidth-efficient wireless video communication.Moreover,simulation results show that turbo codes defeat convolutional codes with an averaged E_(b)/N_(0) gain of 1.5 dB while convolutional codes outperformcompared to SCC codes with an E_(b)/N_(0) gain of 3.5 dBatBit ErrorRate(BER)of 10−4.The Peak Signal to Noise Ratio(PSNR)results of convolutional codes with the latest source coding standard of H.266 is plotted against convolutional codes with H.265 and it was concluded H.266 outperform with about 6 dB PSNR gain at E_(b)/N_(0) value of 4.5 dB.

A Novel Concatenated Chaotic Communication System

A strategy for a novel concatenated chaotic communication system is presented. The transmitter system comprises chaotic turbo encoder and logistic CSK block in a serially concatenated form. Chaotic turbo code is capable of reducing bit error rate (BER) of the chaotic system in the AWGN channel. Through the chaotic turbo encoder, the coded sequence, which has quasi-chaotic properties, will be transmitted into the logistic CSK block. Having a very sensitive dependence on initial conditions of the map, the logistic CSK block can also be taken as the chaotic authentication method. The receiver, which has logistic demodulation block and chaotic decoder, is a linear asymptotic approximation to the inverse of the transmitter system. A chaotic iterative soft-decision decoding algorithm is also developed based on conventional maximum A posteriori decoding algorithm. At last, a two-step authentication method of this chaotic system is also presented.

Performance Evaluation for Medium Voltage MIMO-OFDM Power Line Communication System

Power line communication(PLC)provides intelligent electrical functions such as power quality measurement,fault surveys,and remote control of electrical network.Most of research works have been done in low voltage(LV)scenario due to the fast development of in-home PLC.The aim of this paper is to evaluate the link-level performance of a medium voltage(MV)MIMO-OFDM communication system based on transmission link under underground power line channel.The MIMO channel is modeled as a modified multipath model in the presence of impulsive noise and background noise.We first perform a measurement on the practical MV MIMO channel parameters for a section of buried cable of 1 km long in Ganzhou city,Jiangxi province,China.Based on the measured channel,we design the frame structure based on an IEEE standard for broadband over power line networks[1]to support MV MIMO-OFDM transmission.According to designed frame structure,we design an encoder and a decoder for a dual binary tail-biting turbo code and optimize some key decoder parameters for low bit error rate performance.Finally,the link-level performance for both spatial multiplexing and spatial diversity are evaluated.Numeral results show that MV MIMO-OFDM is a promising approach to provide both high data rate and link reliability for PLC.

Systematic-bit-selection distributed with selective-relaying

An improved distributed turbo coding （DTC） scheme, namely, systematic-bit-selection DTC, is proposed for a two-hop relay network implementing selective-relaying （SR）. In the scheme, source broadcasts a punctured turbo code in order to increase the successful decoding rate of relay. The relay forwards systematic-bit to the destination in case of successful cyclic redundancy check （CRC）. From the two versions of systematic-bit coming from relay and source respectively, the des- tination selects the one with higher signal-to-noise ratio （SNR） for turbo decoding. Simulation re- suits show the improved bit error rate （BER） performance of our scheme.