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

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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turbo-coded packet transmission for an optical CDMA network

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JOURNAL OF LIGHTWAVE TECHNOLOGY 2000年第12期18卷 1905-1916页

作者： Kim, JY Poor, HV Cent Res & Dev Ctr SK Telecom Access Network Grp Sungnam City 463020 Kyunggi Do South Korea Princeton Univ Dept Elect Engn Princeton NJ 08544 USA

The performance of an optical code-division multiple-access (CDMA) network with turbo coding is analyzed and simulated. An intensity-modulated and direct-detected optical system employing binary-pulse-position-modulation is considered, The performance of the network is evaluated in terms of throughput-delay characteristics that depend on the turbo coded bit error rate (BER) performance. To eliminate delay capture effects, time-of-arrival randomization is employed. Simulation results demonstrate that the performance of such an optical CDMA network can be substantially improved by increasing the interleaver length and the number of iterations in the decoding process for a fixed code rate. Also, it is confirmed that turbo coding is very effective in increasing the number of simultaneous users that can be supported by an optical CDMA network for a given BER requirement.

关键词： delay optical code division multiple access (CDMA) throughput turbo coding

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Optimization of satellite access lower layer for the transport of IP datagrams

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IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS 2004年第3期22卷 529-537页

作者： Leconte, K Morlet, C Alcatel Space 26 F-31037 Toulouse 1 France European Space Agcy ESTEC NL-2200 AG Noordwijk Netherlands

This paper presents a novel solution optimizing satellite access lower layers and system performances called variable size packets (VSPs) designed for the transport of Internet protocol (IP) datagrams or any packet type from the network layers characterized by a highly variable size. VSP objective is to maximize the, efficiency of layers 1 and 2 thrbugh a joint optimization of access and transport mechanisms mainly for satellite systems addressing residential or corporate terminals market through a multiple-access scheme. It, is particularly attractive for, the return link of next-generation satellite systems to be IP-based, as a possible evolution of the digital video broadcast-return channel via satellite (DVB-RCS) standard. The VSP solution relies on the definition of multiple encapsulation sizes, and is associated to a waveform and an access adapted to variable size packets' transport. It uses the traffic's variable size nature to increase encapsulation efficiency, coding, and spectral,efficiency performances, and system flexibility. It is well adapted to systems using an adaptive waveform leading to system capacity's increase and better performances. This paper describes the VSP principle, advantages and possible high-level system tradeoffs. It then focuses on one critical issue, the, coding, and presents a suitable coding scheme's choice with regards to performances and implementation complexity.

关键词： adaptive coding and modulation encapsulation encoding Internet protocol (IP) datagrams satellite communication turbo coding variable size packets

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Comparative study of turbo decoding techniques: An overview

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2000年第6期49卷 2208-2233页

作者： Woodard, JP Hanzo, L Univ Southampton Dept Elect & Comp Sci Southampton SO17 1BJ Hants England

In this contribution, we provide an overview of the novel class of channel codes referred to as turbo codes, which have been shown to be capable of performing close to the Shannon Limit. We commence with a brief discussion on turbo encoding, and then move on to describing the form of the iterative decoder most commonly used to decode turbo codes, We then elaborate on various decoding algorithms that can be used in an iterative decoder, and give an example of the operation of such a decoder using the so-called Soft Output Viterbi Algorithm (SOVA). Lastly, the effect of a range of system parameters is investigated in a systematic fashion, in order to gauge their performance ramifications.

关键词： .decoding algorithms Comparative Study frame length turbo coding turbo Decoding iterative decoder Soft Output used to decode decoder using

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Diversity Combining and SNR Estimation for turbo-Coded Frequency-Hopped Spread-Spectrum in Partial-Band Interference and Fading Channels

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WIRELESS PERSONAL COMMUNICATIONS 2009年第3期50卷 351-365页

作者： Elezabi, Ayman Gomaa, Ahmad Amer Univ Cairo Dept Elect Engn Cairo Egypt Amer Univ Cairo Elect & Commun Dept Cairo Egypt

We compare different combinations of the repetition diversity order L and code rate R for turbo-coded Frequency-Hopped Spread-Spectrum (FH/SS) communication systems in the presence of fading and partial-band Gaussian interference. For a fixed overall channel code rate R/L we show that using the lowest code rate and no repetition diversity always performs better than using a higher code rate and some repetition for both coherent and non-coherent schemes. We then propose a simple maximum-likelihood-based method for signal-to-noise-ratio (SNR) estimation in Non-Coherent Binary Frequency Shift Keying (NCBFSK) without training symbols. Except for impractically small hop sizes of 8 bits or less we obtain performance virtually equal to that of perfect SNR knowledge but with much less complexity than iterative schemes previously proposed. For the case of Coherent Binary Phase Shift Keying (CBPSK) we derive the Expectation Maximization (EM) estimate of the SNR without training symbols and iteratively feed the estimator with the extrinsic information from the turbo decoder. The performance for CBPSK is near that of perfect SNR knowledge for hop sizes of 64 bits or more. Unlike previously proposed methods for CBPSK the EM estimate of SNR does not require knowledge of the noise and interference variance, received bit energy, or the fading channel model.

关键词： Partial-band interference Frequency hopping Diversity combining turbo coding SNR estimation Expectation maximization Maximum likelihood

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Iterative frequency domain joint-over-antenna detection in Multiuser MIMO

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IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS 2007年第10期6卷 3620-3631页

作者： Karjalainen, Juha Veselinovic, Nenad Kansanen, Kimmo Matsumoto, Tad Univ Oulu Ctr Wireless Commun FIN-90014 Oulu Finland Norwegian Univ Sci & Technol N-7491 Trondheim Norway

Multiuser multiple-input-multiple-output (MIMO) wireless systems have great potential in improving information rate, diversity and resistance to against interference. The primary objective of this paper is to derive for broadband signaling a new iterative frequency domain (FD) multiuser MIMO signal detection technique for joint-over-antenna (JA) detection. The proposed detector is based on soft-cancellation and minimum mean square error (MMSE) filtering, followed by maximum a posteriori probability (MAP) detector to detect several of each users transmit antennas. The purpose of jointly detecting several transmit antennas is to preserve the degrees of freedom (DoF) for MMSE. Computational complexities with FD and its time domain (TD) counterpart are evaluated in this paper, and it is shown that FD requires significantly lower complexity than TD. Numerical results show that JA significantly outperforms the receiver that detects transmit antenna signals antenna-by-antenna (AA). The proposed iterative FD JA technique achieves larger performance gains compared to AA when the total number of transmit antennas is larger than the number of receiver antennas, as well as in the presence of spatial correlation.

关键词： multiuser MIMO spatial multiplexing turbo coding iterative processing frequency domain equalization

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Low-power hybrid turbo decoding based on reverse calculation

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IEICE TRANSACTIONS ON FUNDAMENTALS OF ELECTRONICS COMMUNICATIONS AND COMPUTER SCIENCES 2006年第3期E89A卷 782-789页

作者： Choi, HM Kim, JH Park, IC Korea Adv Inst Sci & Technol Div Elect Engn Taejon South Korea Korea Adv Inst Sci & Technol Dept Elect Engn Taejon South Korea

As turbo decoding is a highly memory-intensive algorithm consuming large power, a major issue to be solved in practical implementation is to reduce power consumption. This paper presents an efficient reverse calculation method to lower the power consumption by reducing the number of memory accesses required in turbo decoding. The reverse calculation method is proposed for the Max-log-MAP algorithm, and it is combined with a scaling technique to achieve a new decoding algorithm, called hybrid log-MAP, that results in a similar BER performance to the log-MAP algorithm. For the W-CDMA standard, experimental results show that 80% of memory accesses are reduced through the proposed reverse calculation method. A hybrid log-MAP turbo decoder based on the proposed reverse calculation reduces power consumption and memory size by 34.4% and 39.2%, respectively.

关键词： log-MAP algorithm low-power design Max-log-MAP algorithm reverse calculation turbo codes turbo coding turbo decoding

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Radial basis function-assisted turbo equalization

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IEEE TRANSACTIONS ON COMMUNICATIONS 2003年第4期51卷 664-675页

作者： Yee, MS Yeap, BL Hanzo, L Univ Southampton Dept Elect & Comp Engn Southampton SO17 1BJ Hants England

This paper presents a turbo equalization (TEQ) scheme, which employs a radial basis function (RBF)-based equalizer instead of the conventional trellis-based equalizer of Douillard et al. Structural, computational complexity, and performance comparisons of the RBF-based and trellis-based TEQs are provided. The decision feedback-assisted RBF TEQ is capable of attaining a similar performance to the logarithmic maximum a posteriori scheme in the context of both binary phase-shift keying (BPSK) and quaternary phase-shift keying (QPSK) modulation, while achieving a factor 2.5 and 3 lower computational complexity, respectively. However, there is a 2.5-dB performance loss in the context of 16 quadrature amplitude modulation (QAM), which suffers more dramatically from the phenomenon of erroneous decision-feedback effects. A novel element of our design, in order to further reduce the computational complexity of the RBF TEQ,is that symbol equalizations are invoked at current iterations only if the decoded symbol has a high error probability. This techniques provides 37% and 54% computational complexity reduction compared to the full-complexity RBF TEQ for the BPSK RBF TEQ and 16QAM RBF TEQ, respectively, with little performance degradation, when communicating over dispersive Rayleigh fading channels.

关键词： decision-feedback equalizer (DFE) Jacobian logarithm neural network radial basis function (RBF) turbo coding turbo equalization (TEQ)

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Near-optimal decoding for coded and power-controlled DS-CDMA downlink

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IEEE TRANSACTIONS ON COMMUNICATIONS 2004年第5期52卷 701-705页

作者： Kim, BH GCT Semicond Inc Seoul 150877 South Korea

We first present the traditional decoding approach that employs the common pilot-channel-based maximal ratio combining and the Viterbi or iterative decoding cannot achieve the optimal error-rate performance for downlink direct-sequence code-division multiple-access (CDMA) signals when a fast power control technique is applied together with a convolutional or turbo coding. Then, as an efficient method to realize a nearly optimal decoding, we propose a branch metric power readjustment (BMPR) technique, where the downlink power control command generated by the mobile station is used not only to adjust the base station power in the transmitter side, but also to readjust the decoder input branch metric power in the receiver side. Numerical results show that the BMPR technique applied to the IMT-2000 wideband-CDMA system can improve the transmit power utilization by up to 0.4 dB for the block-error rate of 10(-2).

关键词： branch metric power readjustment (BMPR) convolutional coding iterative decoding maximal ratio combining (MRC) turbo coding Viterbi decoding

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Reliability improvement techniques for HomeRF system

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IEEE TRANSACTIONS ON CONSUMER ELECTRONICS 2003年第2期49卷 321-327页

作者： Cho, JH Song, HK Sejong Univ Dept Informat & Commun Engn Seoul South Korea

In this paper, we propose several techniques for the HomeRF system. A DC-offset compensation technique and a decision directed channel estimation technique are proposed. Because they use a TS field as reference information for initial training, the proposed techniques require no additional training sequence and only a little additional complexity. And finally, turbo coding technique and space-time block coding technique are considered as improved coding schemes. According to the results of our simulations, the performances of the proposed techniques are significantly improved in comparison with the conventional HomeRF system.

关键词： channel estimation DC-offset compensation space-time block coding turbo coding

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