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Evaluation of block turbo code performance with the reduced search trellis decoding method

IEE PROCEEDINGS-COMMUNICATIONS 2001年第3期148卷 125-131页

作者： Shin, SK Lee, SI Lee, SP Elect & Telecommun Res Inst Satellite Commun Syst Dept Yusong Gu Taejon 305350 South Korea

Iterative decoding of parallel concatenated codes, also known as turbo codes, can provide tremendous coding gain approximating to the Shannon limit. Application of turbo coding techniques to block codes gives many advantages, due to the finite code length of the constituent codes and their ease of modification. The authors investigate the application of the trellis decoding method to block turbo codes, since one of the most easy and efficient ways of providing soft output at the decoder is incorporation of the trellis decoding method. The soft output Viterbi algorithm is mainly considered, with performance improvement techniques. The authors propose efficient reduced search algorithms in which the decoder complexity can be reduced about ten times with less than 0.1dB degradation in coding gain.

关键词： coding gain computational complexity parallel concatenated codes turbo coding concatenated codes soft decoder output turbo codes decoder complexity reduction BER performance Shannon limit search problems AWGN channel block codes efficient reduced search algorithms block turbo code iterative decoding error statistics Other topics in statistics finite code length Viterbi decoding AWGN channels soft output Viterbi algorithm BCH codes Codes reduced search trellis decoding performance evaluation

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ML Iterative Soft-Decision-Directed (ML-ISDD): A carrier synchronization system for short packet turbo coded communication

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IEEE TRANSACTIONS ON COMMUNICATIONS 2008年第7期56卷 1169-1177页

作者： Rahamim, Yossef Freedman, Avraham Reichman, Arie Tel Aviv Univ Sch Elect Engn Adv Commun Ctr IL-69978 Tel Aviv Israel

Modern communication, systems are required to provide services based on high data rates burst-mode packet-data transmission, capable of operating at very low SNR conditions. turbo codes enable the operation at low SNR, close to the Shannon limit. However, carrier frequency and phase synchronization, needed for optimal coherent performance of the receiver, still remains a problem in low SNR and short bursts conditions. This paper proposes a new carrier synchronization method, the Maximum-Likelihood Iterative-Soft-Decision-Directed (ML-ISDD), which uses the turbo-decoder soft decisions to improve the carrier synchronization performance at low SNR values. The ML-ISDD method operates iteratively and jointly with the turbo decoder, enhancing both the turbo-decoder and the synchronization performance. The ML-ISDD method has been shown by simulation to significantly increase the allowed initial frequency and phase uncertainty region, thus allowing the use of very short training sequences for initial carrier synchronization.

关键词： phase and frequency synchronization turbo coding packet radio

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turbo Decoder SNR Estimation with RAKE Reception

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IEEE TRANSACTIONS ON COMMUNICATIONS 2009年第2期57卷 430-439页

作者： Boyer, Pete Giordano, Arthur TruePosition Berwyn PA USA AG Consulting Burlington MA USA

The joint performance of a turbo decoder and RAKE receiver using the MAP algorithm depends on the accuracy of the channel reliability factor. In a high data rate/low processing gain environment, inherent interference that results from non-idealities of the RAKE receiver complicate the estimation of the channel reliability factor. The combined performance of a turbo decoder and RAKE receiver is analyzed in a time-dispersive and time-varying channel with distinct multipath components. Approaches are examined for estimating the channel reliability factor using the limited information that is known by the RAKE receiver. The sensitivity of performance to SNR mismatches is computed. The impact of the processing gain and the number of multipath components on BER performance is analyzed along with the effect of the channel time coherence. By accounting for the non-ideal RAKE interference effects, improvements in the channel reliability factor calculation result in BER performance improvements on the order of 0.5-2B.

关键词： Code-division multiple access (CDMA) turbo coding Rake reception fading channels time dispersion

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Utilization of multi-dimensional source correlation in multi-dimensional single parity check codes

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TELECOMMUNICATION SYSTEMS 2016年第4期62卷 735-745页

作者： Izhar, Mohd Azri Mohd Zhou, Xiaobo Matsumoto, Tad Univ Teknol Malaysia Wireless Commun Ctr Skudai 81310 Johor Malaysia Tianjin Univ Sch Comp Sci & Technol Weijin Rd 92 Tianjin 300072 Peoples R China Japan Adv Inst Sci & Technol 1-1 Asahidai Nomi Ishikawa 9231292 Japan

This paper proposes a joint source-channel coding (JSCC) technique that well utilizes multi-dimensional (MD) source correlation using MD single parity check codes (MD-SPCCs). The source is assumed to be described by the coupling of multiple first-order binary Markov processes. The knowledge about the source correlation is utilized in the channel decoding process where each component decoder utilizes a single dimension correlation of the MD source. To enhance performance and reduce the error floor, a rate-1 recursive systematic convolutional code is serially concatenated to the MD-SPCC via a random interleaver. Two decoding techniques are proposed for each component decoder, and the selection of the decoding technique depends on the strength of the source correlation, which may further enhance the performance of the proposed JSCC technique. Simulation results reveal that a significant performance gain can be achieved by exploiting the MD source correlation with the proposed JSCC technique compared with the case in which the source correlation is not utilized;more significant gains can be achieved with stronger source correlation, and with a larger dimensionality source correlation as well.

关键词： Joint source-channel coding Single parity check codes Multi-dimensional source correlation turbo coding

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Reducing the PAPR by utilisation of the LDPC code

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IET COMMUNICATIONS 2009年第4期3卷 520-529页

作者： Daoud, O. Alani, O. Philadelphia Univ Sch Commun & Elect Engn Amman 19392 Jordan Univ Leeds Sch Elect & Elect Engn Leeds LS2 9JT W Yorkshire England

Peak-to-average power ratio (PAPR) is a major drawback in most multi-carrier communication techniques such as orthogonal frequency division multiplex system (OFDM). OFDM consists of lots of independent modulated subcarriers, as a result the amplitude of such a signal can have very large values. These large peaks increase the amount of intermodulation distortion resulting in an increase in the error rate. The PAPR of an OFDM signal can be reduced in several ways: selective mapping, Golay sequences, cyclic coding, clipping and filtering, and multiple signal representation techniques. The authors have improved the performance of the OFDM system by using low-density parity-check (LDPC) codes as an alternative to turbo coding in mitigating the PAPR problem which has been used in the pervious works of the authors. The authors present the design for the proposed (LDPC) code technique that achieves good error correction performance and is used to lower the PAPR in a multiple-input multiple-output OFDM system. The simulation results show that 6-60% reduction in PAPR over current values in the literature can be achieved depending on the system type.

关键词： error correction intermodulation distortion parity check codes low-density parity-check codes peak-to-average power ratio reduction multicarrier communication technique multiple-input multiple-output OFDM system Codes OFDM selective mapping orthogonal frequency division multiplex system OFDM modulation turbo coding error correction performance Golay sequence multiple signal representation techniques turbo codes Radio links and equipment cyclic coding MIMO communication

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Iterative QRM-MLD with pilot-assisted decision directed channel estimation for OFDM MIMO multiplexing

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IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES 2006年第7期E89A卷 1892-1902页

作者： Adachi, Koichi Esmailzadeh, Riaz Nakagawa, Masao Keio Univ Fac Sci & Technol Yokohama Kanagawa 2238522 Japan

Multiple-input multiple-output (MIMO) multiplexing has recently been attracting considerable attention for increasing the transmission rate in a limited bandwidth. In MIMO multiplexing, the signals transmitted simultaneously from different transmit antennas must be separated and detected at a receiver. Maximum likelihood detection with QR-decomposition and M-algorithm (QRM-MLD) can achieve good performance while keeping computational complexity low. However, when the number of surviving symbol replica candidates in the M-algorithm is set to be small, the performance of QRM-MLD degrades compared to that of MLD because of wrong selection of surviving symbol replica candidates. Furthermore, when channel estimation is inaccurate, accurate signal ranking and QR-decomposition cannot be carried out. In this paper, we propose an iterative QRM-MLD with decision directed channel estimation to improve the packet error rate (PER) performance. In the proposed QRM-MLD, decision feedback data symbols are also used for channel estimation in addition to pilot symbols in order to improve the channel estimation accuracy. Signal detection/channel estimation are then carried out in an iterative fashion. Computer simulation results show that the proposed QRM-MLD reduces the required average received E-b/N-0 for PER of 10(-2) by about 1.2 dB compared to the conventional method using orthogonal pilot symbols only.

关键词： OFDM MIMO QRM-MLD channel estimation turbo coding

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Burst-by-burst adaptive turbo-coded radial basis function-assisted decision feedback equalization

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IEEE TRANSACTIONS ON COMMUNICATIONS 2001年第11期49卷 1935-1945页

作者： Yee, MS Liew, TH Hanzo, L Univ Southampton Dept Elect & Comp Sci Southampton SO17 1BJ Hants England

The performance of the proposed radial basis function (RBF) assisted turbo-coded adaptive modulation scheme is characterized in a wideband channel scenario. We commence by introducing the novel concept of the Jacobian RBF equalizer, which is a reduced-complexity version of the conventional RBF equalizer. Specifically, the Jacobian logarithmic RBF equalizer generates its output in the logarithmic domain and hence it can be used to provide soft outputs for the turbo-channel decoder. We propose using the average magnitude of the log-likelihood ratio (LLR) of the bits in the received transmission burst before channel decoding as the channel quality measure for controlling the mode-switching regime of our adaptive scheme.

关键词： adaptive modulation AQAM decision feedback equalizer DFE Jacobian logarithm neural network radial basis function RBF turbo coding

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Design of Simulation System for LTE-U Using 5 GHz Band in MATLAB

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WIRELESS PERSONAL COMMUNICATIONS 2018年第4期100卷 1661-1676页

作者： Tariq, Muhammad Anjum, M. R. Amjad, Muhammad Islamia Univ Bahawalpur Dept Elect Engn Bahawalpur Pakistan

Unused spectrum is being a limited commodity for the telecom industry. However, up to 500 MHz of unlicensed spectrum in 5 GHz band is in use for several applications and services, particularly in WiFi around the world. Unlicensed spectrum has foreseen to play a vital role in 5G. It is already under discussion at different forums that how the unlicensed band advantage can promote 4G Long Term Evolution (LTE) networks. Long Term Evolution Unlicensed (LTE-U) is an extension of existing LTE mobile networks, and allow LTE technology to use unlicensed bands as an adjunct to the licensed band. It will not only deliver a better user experience to end users but also boost capacity for network operators. In this paper, a Simulink based LTE PDSCH (Physical Downlink Shared Channel) model is introduced which uses the 5 GHz band according to the specifications prescribed by LTE-U Forum and 3GPP (Third Generation Partnership Project). It demonstrates multi-codeword transmission within a small cell from an eNodeB to a User Equipment (UE). LTE enabling technologies like OFDMA, closed-loop spatial multiplexing, turbo channel coding and link adaptations are used to design this model. Minimum mean square error (MMSE) technique as a linear detection method is used for spatially multiplexed Multiple Input Multiple Output (MIMO). Bit error rate is analyzed for QPSK, 16-QAM, and 64-QAM and compared for hard and soft decisions MMSE based MIMO detection. Fairly improved throughputs are obtained for multi-antenna configurations considering the low mobility scenarios and low correlation settings between links.

关键词： LTE-U Unlicensed spectrum 5 GHz band turbo coding Closed-loop spatial multiplexing MIMO

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Error rate performance of turbo coded partial response systems for digital magnetic recording channels

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IEICE TRANSACTIONS ON ELECTRONICS 1999年第12期E82C卷 2218-2226页

作者： Saito, H Takai, M Okamoto, Y Osawa, H Ehime Univ Fac Engn Matsuyama Ehime 7908577 Japan

In various digital wireless communication systems, it is known that turbo coding provides an error rate performance within a few tenths of a dB of the theoretical Shannon limit. The error correcting capability of turbo coding is attractive for a recording code in a digital magnetic recording system. The performance of a partial response maximum-likelihood (PRML) system with any recording code is degraded by many undesirable factors such as linear and nonlinear distortions. For improving the performance of the PRML system, it is useful to adopt a high-order PRML system or high rate code in general. In this paper, the two-track recording system using turbo coding which can increase the coding rate over 1 and improve the performance is proposed. turbo-coding provides a near-ML performance by the suboptimum symbol-by-symbol maximum a posteriori probability (MAP) decoding algorithm. Our proposed turbo-coded class 4 partial response (PR4) systems use the rate 4/6, 8/10 and 16/18 turbo codes for high-density two;track-digital magnetic recording. The error rate performance is obtained by computer simulation, taking account of the partial erasure which is a prominent nonlinear distortion in high-density recording. As a result, the proposed systems are hardly affected by partial erasure and maintains good performance compared with the convectional NRZ coded PR4ML system.

关键词： digital magnetic recording partial response turbo coding MAP decoding partial erasure

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turbo Receiver for Multicarrier Spread Spectrum Systems Employing Parity Bit Selected Spreading Sequences

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WIRELESS PERSONAL COMMUNICATIONS 2013年第2期70卷 889-902页

作者： Mirzaee, Alireza D'Amours, Claude Univ Ottawa Sch Elect Engn & Comp Sci Ottawa ON Canada

In this paper a turbo receiver for multicarrier spread spectrum systems employing parity bit selected spreading code (MC-SS-PB) is proposed where detection and decoding are performed iteratively for each detected bit in the receiver. In MC-SS-PB systems, the parity bits generated by a linear block encoder are used to select a spreading code from a set of orthogonal spreading sequences. The selected spreading code is then used to spread the signals in all subcarriers. In the proposed receiver, soft information passes between the detector and the decoder on multiple iterations. Detection is performed by using the received signal in combination with the extrinsic likelihood provided by a soft input soft output decoder. The turbo receiver is further extended to a multiple user system where the multiple access interference is estimated in each iteration and subtracted out from the received signal. Simulations show a significant reduction in bit error rates when a turbo receiver is used in these systems.

关键词： Multicarrier spread spectrum systems turbo coding CDMA Multiuser detection

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