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15th IEEE International Symposium on Personal, Indoor, Mobile, Radio Communications (PIMRC 2004)

作者： Tsumura, S Vehkaperä, M Li, ZX Tujkovic, D Juntti, M Hara, S Osaka Univ Grad Sch Engn Suita Osaka 5650971 Japan

ISBN: (纸本)0780385233

In this paper, we evaluate the performance of single- and multi-antenna multi-carrier code division multiple access (MC-CDMA) downlink (base station to mobile terminal) systems in multi-cell environments. We first propose a minimum mean square error (MMSE) filter for a single input single output (SISO) MC-CDMA downlink system. Then, we apply it to a SIMO (single input multiple output) system with a conventional turbo coding. Furthermore, we compare the performance of SISO (1 x 1) and SIMO (1 x 2) MC-CDMA systems with that of a multiple input multiple output (MIMO) (2 x 2) system employing space-time turbo coded modulation (STTuCM) in a multi-cell environment with 7 cells by computer simulation. Based on the computer simulation results, it is found that the considered MIMO system can achieve twofold capacity with the same transmission power in the multi-cell environment.

关键词： MC-CDMA MIMO space-time coding turbo coding

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Performance of turbo-coded MC-CDMA system based on complex wavelet packet in Rayleigh fading channel

Performance of Turbo-coded MC-CDMA system based on complex w...

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International Conference on Communications, Circuits and Systems

作者： Yu, XB Bi, GG Southeast Univ Natl Mobile Commun Res Lab Nanjing 210096 Peoples R China

ISBN: (纸本)0780386477

In this paper, on the basis of analyzing the principle of multi-carrier code division multiple access (MC-CDMA) technique, by employing the optimized complex wavelet packet as multi-carrier modulation and the turbo codes as channel coding, we propose a novel MC-CDMA system based on complex wavelet packet and turbo coding, and investigate the system bit error rate (BER) performance in Rayleigh fading channel. The system can overcome the decrease of spectrum efficiency and energy of conventional MC-CDMA due to inserting cyclic prefix (CP);and make full use of the turbo codes' good capacity against fading channel to improve the BER performance further. Theoretical analysis and simulation results all show that the proposed system outperforms conventional MC-CDMA system, and its performance is superior to that of the conventional MC-CDMA with CP. Meanwhile, the application of turbo coding strengthens the system ability to cope with multi-path fading and multi-access interference (MAI) significantly.

关键词： complex wavelet packet turbo coding multi-carrier technique CDMA OFDM

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ML iterative tentative-decision-directed (ML-ITDD): A carrier synchronization system for short packet turbo coded communication

ML iterative tentative-decision-directed (ML-ITDD): A carrie...

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11th IEEE International Conference on Electronics, Circuits and Systems

作者： Rahamim, Y Freedman, A Reichman, A Tel Aviv Univ Sch Elect Engn IL-69978 Tel Aviv Israel

ISBN: (纸本)0780387155

The invention of turbo Codes has manifested the ability of communications systems to operate at very low signal to noise ratio, very close to the theoretical Shannon capacity limit. However, synchronization of turbo-coded signals operating in low SNR conditions may be difficult, especially for short packet transmission. This paper proposes the Maximum-Likelihood Iterative-Tentative-Decision-Directed (ML-ITTD) circuit for using the tentative decisions produced by the turbo decoder to improve the carrier synchronization in turbo coded short packets communication systems. The ML-ITDD method operates iteratively and jointly with the turbo decoder, enhancing both the turbo-decoder and the synchronization performance. The ML-ITDD 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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A low power programmable turbo decoder macro using the SOVA algorithm

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IEICE TRANSACTIONS ON ELECTRONICS 2004年第4期E87C卷 510-519页

作者： Gambe, H Ohbuchi, K Ishihara, T Zakoji, T Araki, K Fujitsu Labs Ltd Kawasaki Kanagawa 2118588 Japan Tokyo Inst Technol Tokyo 1528552 Japan

turbo codes are of particular use in applications of wireless communication systems, where various types of communication are required and the data rate must be changed, depending on the situation. In such applications, adaptation of turbo coding specifications is required in terms of coding block size, data speed, parity bit arrangement or configuration of a convolutional coder, as well as the need for real time processing. We present new ideas to provide these capabilities for a low power decoder circuit by focusing on the configuration of a convolutional decoding algorithm, which occupies a significant proportion of the hardware circuit. We utilize the Soft Output Viterbi Algorithm (SOVA) for the base algorithm, produced by adding the concept of a soft output to the Viterbi Algorithm (VA). The Maximum A Posteriori (MAP) algorithm and its simplified version of MAX-LOG-MAP are also widely known. MAP is recognized as a means of achieving very good bit error rate (BER) characteristics. On the other hand SOVA has been regarded as a method which can be simply implemented with less computational resources, but at a cost of higher degradation. However, in many of recent systems we combine turbo coding with some other method such as Automatic Repeat Request (ARQ) to maintain a good error correction performance and we only have to pay attention to the performance in the range of low carrier-to-noise ratio (CNR), where SOVA has fairly satisfactory BER characteristics. This makes the SOVA approach attractive for a low power programmable IP macro solution, when the fundamental advantage of SOVA is fully utilized in the implementation of an LSI circuit. We discuss the processing algorithm and circuit configuration and show that about 40% reduction in power consumption can be achieved. It is also shown that the IP macro can handle 1.5 Mbps information decoding at 100 MHz clock rate.

关键词： turbo coding SOVA Viterbi algorithm trace back MAX-LOG-MAP sliding window

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Outage performance of a CDMA-based mobile satellite communication system with turbo coding

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IEICE TRANSACTIONS ON COMMUNICATIONS 2001年第3期E84B卷 688-690页

作者： Kim, JY SK Telecom Access Network Grp Cent Res & Dev Ctr Kyunggi Do 463020 South Korea

In this paper, outage performance of a turbo-coded CDMA system is analyzed and simulated in a multiple-beam satellite channel. From the simulation results, it is confirmed that turbo coding provides considerable coding gain over an uncoded system. And, it is demonstrated that Max-Log-MAP decoding algorithm is most promising in terms of performance and complexity.

关键词： outage CDMA satellite communication turbo coding

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Limits of error correction coding in video watermarking

Limits of error correction coding in video watermarking

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5th Conference on Security and Watermarking of Multimedia Contents

作者： Ambroze, M Tomlinson, M Serdean, C Wade, G Univ Plymouth Dept Commun & Elect Engn Plymouth PL4 8AA Devon England

ISBN: (纸本)0819448206

The paper discusses the limits of error correction coding for spread spectrum-based video watermarking. The error correction code has as input the watermark data bits and as output the values which will be scaled and used to modify the video pixels (transform coefficients). The data rate of the watermark can increase only at the expense of increasing code rate. Theoretically, the scheme is seen as a communication channel with Gaussian additive noise interference. Shannon's (ideal) spherical codes are used as the error correcting code to calculate the minimum signal to noise ratio (SNR) necessary for a coding scheme with a given block length to achieve a given error probability. This limit is different from Shannon's asymptotic limit, which is valid for infinite block lengths and zero error probability. In practice, in order to verify the Gaussian channel assumption, the error correction code is a concatenation of codes, of which the innermost is a repetition code. Several practical codes of different length and rates, such as turbo codes and BCH codes are investigated and their performance compared to that of the ideal code of the same size. The compromise block length/code rate is investigated for several marking schemes and attacks.

关键词： video watermarking turbo coding Shannon limit

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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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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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A study of turbo decoding with embedded AR channel model for perpendicular recording

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IEEE TRANSACTIONS ON MAGNETICS 2003年第5期39卷 2570-2572页

作者： Nakamura, Y Okamoto, Y Osawa, H Saito, H Muraoka, H Nakamura, Y Ehime Univ Fac Engn Matsuyama Ehime 7908577 Japan Tohoku Univ RIEC Sendai Miyagi 9808577 Japan

turbo decoding with an embedded autoregressive (AR) channel model is studied in an actual perpendicular magnetic recording channel. Performance of the a posteriori probability (APP) decoder is improved by applying an, AR channel model in order to estimate the decoder input sequence. The bit-error-rate (BER) performance,is obtained by read/write experiments using a spin stand with a perpendicular medium and an single-pole-type/giant magnetoresistive (SPT/GMR) head. The results show that our turbo coding and iterative decoding system using an AR channel model improves the BER performance.

关键词： autoregressive (AR) channel model iterative decoding perpendicular magnetic recording signal-dependent noise prediction turbo coding

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turbo multiuser detection for turbo-coded CDMA in multipath fading channels

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IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY 2002年第5期51卷 1096-1108页

作者： Li, QH Wang, XD Georghiades, CN Intel Corp Intel Labs Santa Clara CA 95052 USA Texas A&M Univ Dept Elect Engn College Stn TX 77843 USA

Multiuser detection and turbo coding are two of the most powerful techniques for enhancing the performance of next-generation wide-band code-division multiple-access (CDMA) systems. In this paper, we develop an iterative multiuser receiver for turbo-coded CDMA systems wit h aperiodic spreading sequences operating in multipath fading, which exploits the power of both techniques. The key innovation in the proposed receiver is a low-complexity soft multiuser detector which uses the same decision statistic as the conventional RAKE receiver (i.e., the outputs of the maximum ratio combiners for all the users), and performs soft-interference cancellation and instantaneous minimum mean-square error (MMSE) filtering. The soft multiuser detector has a complexity of O(K+) per bit per iteration, where K is the number of users. A single-user receiver which employs a soft RAKE detector followed by a turbo decoder is also considered. Simulation results demonstrate that the proposed multiuser receiver offers more than 0.5-dB gain over the single-user RAKE receiver at a bit-error rate (BER) of 10(-3) and even outperforms the single-user RAKE receiver operating in a single-user environment.

关键词： code-division multiple access (CDMA) minimum mean-square error (MMSE) filtering multipath fading multiuser detection soft interference cancellation turbo coding

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