scholarly journals Turbo Codes Performance Optimization over Block Fading Channels

2017 ◽  
Vol 2 (3) ◽  
pp. 228
Author(s):  
Fulvio Babich ◽  
Guido Montorsi ◽  
Francesca Vatta
Keyword(s):  
Fading Channels ◽  
Mobile Communications ◽  
Turbo Codes ◽  
Performance Optimization ◽  
Fading Channel ◽  
Communication Systems ◽  
Channel Model ◽  
Turbo Code ◽  
Convolutional Codes ◽  
Block Fading Channel

In this paper, the best achievable performance of a turbo coded system on a block fading channel is obtained, assuming binary antipodal modulation. A rate 1/3 turbo code is considered, obtained by concatenating, through a random interleaver, an 8-states rate 1/2 and a rate 1 convolutional codes (CC). The block fading channel model is motivated by the fact that in many wireless systems the coherence time of the channel is much longer than one symbol interval, resulting in adjacent symbols being affected by the same fading value. The fading blocks will experience independent fades, assuming a sufficient separation in time, in frequency, or both in time and in frequency. This channel model is suitable for analyzing, forinstance, wireless communication systems employing techniques such as slow frequency-hopping, as is done in the Global System for Mobile communications (GSM).In such systems, coded information is transmitted over a small number of fading channels in order to achieve diversity. The best coded information allocations over a certain number of fading channels are evaluated, using the Eades-McKay algorithm to generate distinct permutations of a multiset. Bounds on the achievable performance due to coding are derived using information-theoretic techniques. In particular, in the paper an analytical method is proposed, based on the sphere-packing bounding technique, to assess the achievable performance. Moreover, simulation results are obtained and compared with the theoretical ones.

scholarly journals Modeling of Non-WSSUS Double-Rayleigh Fading Channels for Vehicular Communications

2017 ◽  
Vol 2017 ◽  
pp. 1-15 ◽  
Author(s):  
Carlos A. Gutiérrez ◽  
J. J. Jaime-Rodríguez ◽  
J. M. Luna-Rivera ◽  
Daniel U. Campos-Delgado ◽  
Javier Vázquez Castillo
Keyword(s):  
Fading Channels ◽  
Communication Systems ◽  
Rayleigh Fading ◽  
Channel Model ◽  
Closed Form Solution ◽  
Multipath Fading ◽  
Rayleigh Distribution ◽  
Rayleigh Fading Channels ◽  
Small Scale ◽  
Time Frequency

This paper deals with the modeling of nonstationary time-frequency (TF) dispersive multipath fading channels for vehicle-to-vehicle (V2V) communication systems. As a main contribution, the paper presents a novel geometry-based statistical channel model that facilitates the analysis of the nonstationarities of V2V fading channels arising at a small-scale level due to the time-varying nature of the propagation delays. This new geometrical channel model has been formulated following the principles of plane wave propagation (PWP) and assuming that the transmitted signal reaches the receiver antenna through double interactions with multiple interfering objects (IOs) randomly located in the propagation area. As a consequence of such interactions, the first-order statistics of the channel model’s envelope are shown to follow a worse-than-Rayleigh distribution; specifically, they follow a double-Rayleigh distribution. General expressions are derived for the envelope and phase distributions, four-dimensional (4D) TF correlation function (TF-CF), and TF-dependent delay and Doppler profiles of the proposed channel model. Such expressions are valid regardless of the underlying geometry of the propagation area. Furthermore, a closed-form solution of the 4D TF-CF is presented for the particular case of the geometrical two-ring scattering model. The obtained results provide new theoretical insights into the correlation and spectral properties of small-scale nonstationary V2V double-Rayleigh fading channels.

On Capacity of 60GHz TH-PPM Systems in Frequency Selective Fading Channels

2012 ◽  
Vol 433-440 ◽  
pp. 5506-5511 ◽  
Author(s):  
Na Li ◽  
Hao Zhang ◽  
Jing Jing Wang ◽  
T. Aaron Gulliver
Keyword(s):  
Fading Channels ◽  
Fading Channel ◽  
Channel Model ◽  
Selective Fading ◽  
Pulse Modulation ◽  
Frequency Selective Fading ◽  
Single User ◽  
Frequency Selective ◽  
Performance Results ◽  
Channel Properties

Two pulse waveforms are designed and analyzed for 60GHz pulse modulation systems. An indoor frequency selective fading channel model is introduced for single user 60GHz TH-PPM systems. The capacity with this channel model of a 60GHz TH-PPM system based on the designed pulses is derived. Performance results are presented to illustrate the effects of the pulse waveforms and channel properties on the channel capacity.

scholarly journals Introducing perforation when applying turbo codes

2021 ◽  
Vol 2094 (3) ◽  
pp. 032061
Author(s):  
A A Sidorenko
Keyword(s):  
Data Transmission ◽  
Turbo Codes ◽  
Communication Systems ◽  
Digital Communication ◽  
Turbo Code ◽  
Code Sequence ◽  
Transmission Channel ◽  
Comparison Results ◽  
Decoding Efficiency ◽  
Digital Communication Systems

Abstract The problem of adapting the degree of redundancy introduced in the process of error-correcting coding to the changing characteristics of the data transmission channel is urgent. Turbo codes, used in a variety of digital communication systems, are capable of correcting multiple errors occurring in the data transmission channel. The article compares the decoding efficiency for various options for introducing perforation into the code sequence generated by the turbo code encoder. Based on the comparison results, recommendations were made on the most appropriate option for the introduction of perforation.

Digital Communications and a Smart World

2019 ◽  
pp. 136-163
Author(s):  
Hua Zhong
Keyword(s):  
Turbo Codes ◽  
Iterative Decoding ◽  
Communication Systems ◽  
Information Transfer ◽  
Turbo Code ◽  
Digital Communications ◽  
Substantial Reduction ◽  
International Standards ◽  
Extrinsic Information ◽  
Likelihood Ratios

This chapter is devoted to digital communications in a smart world. The author examines turbo codes that are currently introduced in many international standards and implemented in numerous advanced communication systems, applied in a smart world, and evaluate the process of extrinsic information transfer (EXIT). The convergence properties of the iterative decoding process, associated with a given turbo-coding scheme, are estimated using the analysis technique based on so-called EXIT charts. This approach provides a possibility to predict the bit-error rate (BER) of a turbo code system with only the extrinsic information transfer chart. The idea is to consider the associated soft-input soft-output (SISO) stages as information processors, which map input a priori log likelihood ratios (LLRs) onto output extrinsic LLRs. Compared with other methods, the suggested approach provides insight into the iterative behavior of linear turbo systems with substantial reduction in numerical complexity.

Split Channel Two-Tone On-Off Keying for Internet of Things Communication in Fading Channel

2020 ◽  
Vol 17 (7) ◽  
pp. 3207-3211
Author(s):  
Gun-Ho Lee ◽  
Eui-Rim Jeong
Keyword(s):  
Internet Of Things ◽  
Urban Area ◽  
Fading Channels ◽  
Fading Channel ◽  
Communication Systems ◽  
Urban Environments ◽  
Selective Fading ◽  
Communication Performance ◽  
Frequency Selective Fading ◽  
Frequency Selective

In medical treatment, healthcare and home appliances, the demand for Internet of Things (IoT) services is increasing in urban areas. However, in fading environments of urban area, the existing IoT communication system can degrade severely. The purpose of this paper is to develop a new IoT communication technology that improves communication performance in fading channels. IoT communication systems are aiming at low power long distances. In addition, the amount of data transmission is small due to the service requirements. To achieve this goal, existing IoT communication modems are designed with narrowband signals. However, narrowband signals may cause performance degradation in a frequency selective fading channel environments in urban area. In this paper, we propose a split channel two tone OOK (SC-TT-OOK) that implements on-off keying (OOK) using two tones. Unlike the existing OOK by using one tone, SC-TT-OOK uses spaced two tones to improve communication performance in fading channels. The conventional OOK method has a similar characteristic to that of the existing IoT modems with a narrow bandwidth spectrum. The proposed SC-TT-OOK is OOK using two separated tones. Since the proposed modulation uses two tones, it requires twice the frequency resources of the conventional OOK. However, if the frequencies of the two tones are sufficiently spaced apart, frequency diversity gain can be achieved in the frequency selective fading channels, and communication reliability can be improved in urban environments. The proposed SC-TT-OOK is examined through computer simulation. The simulation results show that the proposed scheme outperforms the conventional scheme in the frequency selective fading channel. Therefore, the proposed method can be used as an alternative technique for IoT modem in urban environments.

scholarly journals Iterative Decoding of Turbo Codes

2018 ◽  
Vol 3 ◽  
pp. 15
Author(s):  
Dhaneshwar Sah
Keyword(s):  
Turbo Codes ◽  
Coding Theory ◽  
Iterative Decoding ◽  
Communication Systems ◽  
Error Control ◽  
Viterbi Algorithm ◽  
Convolutional Codes ◽  
Soft Information ◽  
Space Communications ◽  
College Of Engineering

<p><strong> </strong>This paper presents a Thesis which consists of a study of turbo codes as an error-control Code and the software implementation of two different decoders, namely the Maximum a Posteriori (MAP), and soft- Output Viterbi Algorithm (SOVA) decoders. Turbo codes were introduced in 1993 by berrouet at [2] and are perhaps the most exciting and potentially important development in coding theory in recent years. They achieve near- Shannon-Limit error correction performance with relatively simple component codes and large interleavers. They can be constructed by concatenating at least two component codes in a parallel fashion, separated by an interleaver. The convolutional codes can achieve very good results. In order of a concatenated scheme such as a turbo codes to work properly, the decoding algorithm must affect an exchange of soft information between component decoders. The concept behind turbo decoding is to pass soft information from the output of one decoder to the input of the succeeding one, and to iterate this process several times to produce better decisions. Turbo codes are still in the process of standardization but future applications will include mobile communication systems, deep space communications, telemetry and multimedia. Finally, we will compare these two algorithms which have less complexity and which can produce better performance.</p><p><strong>Journal of Advanced College of Engineering and Management</strong>, Vol.3, 2017, Page: 15-30</p>

A Study on Turbo Code Performance Based on AWGN Channel

2013 ◽  
Vol 347-350 ◽  
pp. 1720-1726
Author(s):  
Peng Zhu ◽  
Jun Zhu ◽  
Xiang Liu
Keyword(s):  
Mobile Communications ◽  
Turbo Codes ◽  
Turbo Code ◽  
Signal To Noise Ratio ◽  
Satellite Communications ◽  
Decoding Algorithm ◽  
Awgn Channel ◽  
Code Performance ◽  
Wide Range ◽  
Number Of Iterations

Turbo codes have a wide range of applications in 3G mobile communications, deep-sea communications, satellite communications and other power constrained fields. In the paper, the Turbo Code Decoding Principle and several major decoding methods are introduced. Simulations of Turbo code performance under different parameters of AWGN channel are made and the effects of the different interleaving length, the number of iterations, and the decoding algorithm to Turbo code performance are also discussed in AWGN channel. Simulation results show that under the same signal-to-noise ratio, the more the number of iterations is, the longer the sequence of information is, and the more excellent decoding algorithm is, the better the performance of Turbo codes is.

scholarly journals Variable Forgetting Factor LS Algorithm for Polynomial Channel Model

2011 ◽  
Vol 2011 ◽  
pp. 1-4 ◽  
Author(s):  
Amit Kumar Kohli ◽  
Amrita Rai ◽  
Meher Krishna Patel
Keyword(s):  
Fading Channels ◽  
Fading Channel ◽  
Channel Model ◽  
Time Varying ◽  
Selective Fading ◽  
Forgetting Factor ◽  
Frequency Selective Fading ◽  
First Order ◽  
Variable Forgetting Factor ◽  
Frequency Selective Fading Channels

Variable forgetting factor (VFF) least squares (LS) algorithm for polynomial channel paradigm is presented for improved tracking performance under nonstationary environment. The main focus is on updating VFF when each time-varying fading channel is considered to be a first-order Markov process. In addition to efficient tracking under frequency-selective fading channels, the incorporation of proposed numeric variable forgetting factor (NVFF) in LS algorithm reduces the computational complexity.

scholarly journals Improving the performance of BICM-ID and MLC systems with different FEC codes

2013 ◽  
Vol 11 ◽  
pp. 87-93 ◽  
Author(s):  
T. Arafa ◽  
W. Sauer-Greff ◽  
R. Urbansky
Keyword(s):  
Turbo Codes ◽  
Channel Coding ◽  
Communication Systems ◽  
Forward Error Correction ◽  
Convolutional Codes ◽  
Coded Modulation ◽  
Modulation Formats ◽  
Coding Schemes ◽  
Multilevel Modulation ◽  
Exit Charts

Abstract. In bandwidth limited communication systems, the high data rate transmission with performance close to capacity limits is achieved by applying multilevel modulation schemes in association with powerful forward error correction (FEC) coding, i.e. coded modulation systems. The most important practical approaches to coded modulation systems are multilevel coding with multistage decoding (MLC/MSD) and bit interleaved coded modulation with iterative demapping and decoding (BICM-ID). Multilevel modulation formats such as M-QAM, which can be used as a part of coded modulation systems, have the capability of multilevel protection. Based on this fact, we investigate the methods to improve the performance of BICM-ID using multiple interleavers with different binary channel coding schemes such as convolutional codes, turbo codes and low-density parity-check (LDPC) codes. Moreover, an MLC system with parallel decoding on levels (PDL) at the receiver is considered. In our contribution, we propose to design the individual coding schemes using the extrinsic information transfer (EXIT) charts for individual bit levels in the constellation. Our simulation results show that the BICM-ID systems, taking into account different bit-level protections, can provide an improvement of 0.65 dB, 1.2 dB and 1.5 dB for 256-QAM with turbo, LDPC and convolutional codes, respectively. On the other hand, MLC systems with PDL designed using EXIT charts for individual bit levels can slightly improve the performance and eliminate the error floor compared to the systems with MSD.

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