An antenna array is proposed as a means of achieving a. space-diversity effect that partly overcomes the severity of continuous-time Rayleigh fading channels. The investigated channel is assumed to be frequency-nonsel...
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An antenna array is proposed as a means of achieving a. space-diversity effect that partly overcomes the severity of continuous-time Rayleigh fading channels. The investigated channel is assumed to be frequency-nonselective with correlated diversity links, where the correlation is related to the array geometry and the spatial and Doppler dispersions. Further, the error performance is improved. by bit interleaving and channel coding, where the encoders/channel is viewed as a serially concatenated system: a convolutional code constitutes the outer code, whereas a differential encoder and the fading channel (having truncated memory) form a joint inner code. In order to obtain a practical detector structure it is desirable to perform iterative decoding by applying some a posteriori probability (APP) algorithms. For this purpose, we propose a novel generalization of the well-known Bahl-Cocke-Jelinek-Raviv algorithm that calculates the APPs over channels having memory. Numerical results indicate that iterative decoding becomes more powerful when the exploited channel memory depth is extended. Also, the error performance is significantly improved by introducing multiple antennas. The interleaver gain is, however, seen to be quite moderate, in contrast to additive white Gaussian noise channels.
The computational complexity required by the complete calculation of the distance spectrum of turbo codes, even limited to low weight input sequences, makes it too slow for practical purposes such as interleaver optim...
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The computational complexity required by the complete calculation of the distance spectrum of turbo codes, even limited to low weight input sequences, makes it too slow for practical purposes such as interleaver optimization or effective bit error rate bounding. In this paper, a fast algorithm for distance spectrum estimation purposes is presented. A comparison with complete computed spectra, theoretically derived spectra and results from previous works will be presented for both deterministic and uniform interleavers.
In this letter, the performance of turbo codes is evaluated through analysis and simulation over the Rice multiplicative fading channel. The analysis is conducted extending the results presented by Viterbi and Viterbi...
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In this letter, the performance of turbo codes is evaluated through analysis and simulation over the Rice multiplicative fading channel. The analysis is conducted extending the results presented by Viterbi and Viterbi (1998) to the Rice multiplicative fading channel case. Simulation results are obtained using an extended version of the improved Jakes' channel simulator, first presented by Pop and Beaulieu (2001).
In this work, me investigate the use of forward-error correction (FEC) as well as concatenated coding for reliable data transmission in asynchronous direct-sequence code division multiple-access communications over fr...
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In this work, me investigate the use of forward-error correction (FEC) as well as concatenated coding for reliable data transmission in asynchronous direct-sequence code division multiple-access communications over frequency-selective Rayleigh fading channels. The FEC scheme combines antenna diversity with low complexity concatenated codes which consist of a Reed-Solomon outer code and a convolutional inner code. Under this concatenated coding scheme, we analyze the average bit-error rate performance and capacity tradeoffs between various system parameters under a fixed total bandwidth expansion and concatenated codes constraint requirements.
A novel signaling scheme is presented, where a set of orthogonal signals is transmitted in parallel. The signals are selected according to the so-called residue number system (RNS). Hence the system is essentially a m...
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A novel signaling scheme is presented, where a set of orthogonal signals is transmitted in parallel. The signals are selected according to the so-called residue number system (RNS). Hence the system is essentially a multiple code parallel communication scheme using high-modulation alphabets. It is demonstrated that the system performance van be substantially improved by exploiting a number of advantageous properties of the RNS arithmetic. The model treated in Part I, of this paper is extended here to account for the effects of the multipath Rayleigh fading channel when using noncoherent demodulation. Diversity reception techniques with equal gain combining (EGQ or selection combining (SC) are concerned. The related performance is evaluated for both nonredundant and redundant RNS-based orthogonal signaling. Interleaving and forward error-correction techniques are introduced for enhancing the system's bit error rate (BER) performance. The concept of concatenated coding-with a Reed-Solomon (RS) code as the outer code and a redundant RNS code as the inner code is presented, and the performance of the proposed concatenated code is evaluated. Expressions of the error probability for the above-mentioned scenarios are presented, and the associated BER performance is evaluated numerically with respect to specific system parameters. Without concatenated coding, coding gains up to 8.5 or 11 dB are achieved at a BER of 10(-6) using the lowest reliability dropping technique of Part I and one or two redundant moduli, respectively. The BER is substantially higher than that over the additive white Gaussian noise channel reported in Part 1. With the aid of RS coding, an additional 7.5-dB coding gain is achieved.
Following a brief historical perspective on channel coding, an introduction to space-time block codes is given. The various space-time codes considered are then concatenated with a range of channel codecs, such as con...
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Following a brief historical perspective on channel coding, an introduction to space-time block codes is given. The various space-time codes considered are then concatenated with a range of channel codecs, such as convolutional and block-based turbo codes as well as conventional and turbo trellis codes. The associated estimated complexity issues and memory requirements are also considered. These discussions are followed by a performance study of various space-time and channel-coded transceivers. Our aim is first to identify, a space-time code/channel code combination constituting a good engineering tradeoff in terms of its effective throughput, bit-error-rate performance, and estimated complexity. Specifically, the issue of bit-to-symbol mapping is addressed in the context of convolutional codes (CCs) and convolutional coding as well as Bose-Chaudhuri-Hocquenghem coding-based turbo codes in conjunction with an attractive unity-rate space-time code and multilevel modulation is detailed. It is concluded that over the nondispersive or narrow-band fading channels, the best performance versus complexity tradeoff is constituted by Alamouti's twin-antenna block space-time code concatenated with turbo convolutional codes. Further comparisons with space-time trellis codes result in similar conclusions.
In this paper, we present a performance analysis of a wireless multimedia direct-sequence code-division multiple-access (DS/CDMA) system based on different error control schemes and an optimal power control algorithm ...
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In this paper, we present a performance analysis of a wireless multimedia direct-sequence code-division multiple-access (DS/CDMA) system based on different error control schemes and an optimal power control algorithm over multipath Rayleigh fading channels. The error control schemes consist of Forward Error Correction (FEC), diversity, and Automatic Repeat reQuest (ARQ). The concatenated codes with a Reed-Solomon outer code and convolutional inner code are used as FEC. Since a multimedia system is required to support services with different rates and Quality of Services (QoS), different error control schemes are used to satisfy the requirements of different media. In particular, a power control algorithm which can optimize the capacity performance of the integrated system is presented. Numerical results will show that power optimization can increase the capacity and decrease the total transmission power. By incorporating diversity and hybrid ARQ along with appropriate code rates in the optimal power controlled system, dramatic increase in system capacity can also be achieved.
The Reed-Solomon code and multidimensional TCM (MTCM) can be concatenated to improve the performance of discrete multitone (DMT) modulated digital subscriber line (DSL) systems. The criteria for designing an effective...
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The Reed-Solomon code and multidimensional TCM (MTCM) can be concatenated to improve the performance of discrete multitone (DMT) modulated digital subscriber line (DSL) systems. The criteria for designing an effective multidimensional TCM (MTCM) scheme with efficient interleaver are described The results of simulations for evaluating the performance of the proposed coding scheme are presented.
A soft-decision 8-DPSK modulation format is introduced in a concatenated coding scheme and the performance of the resulting system is evaluated over a slow Rayleigh fading HF ionospheric Link in the presence of Additi...
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A soft-decision 8-DPSK modulation format is introduced in a concatenated coding scheme and the performance of the resulting system is evaluated over a slow Rayleigh fading HF ionospheric Link in the presence of Additive White Gaussian noise (AWGN). Well-known Ungerboeck TCM techniques are used as inner codes and a Reed-Solomon block code as outer code. The coded/modulated signal is differentially encoded before transmission to combat random phase changes caused by the channel. Soft-decision demodulator's output is used as an input to a modified Viterbi decoder that calculates the Euclidean distances of the received signal from an 8-PSK constellation adapted to the signal's amplitude variations. Block interleaving techniques are necessary to randomise long bursts of errors caused by the fading channel. Simulation results show that significant coding gains are achieved with a minor bandwidth expansion over uncoded, diversity or other coded systems. Finally, the interesting effects of interleaving on the performance of the proposed systems are analysed.
In this paper, we consider several issues in the analysis and design of turbo-coded systems for (0, kappa) input-constrained channels. These constraints commonly arise in magnetic recording channels. This system is ch...
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In this paper, we consider several issues in the analysis and design of turbo-coded systems for (0, kappa) input-constrained channels. These constraints commonly arise in magnetic recording channels. This system is characterized by a high-rate turbo code driving a high-rate (n - l)/n, small-length (0, kappa) block code, We discuss the properties of the (0, kappa) code that affect its performance on both an additive white Gaussian noise (AWGN) and a preceded dicode channel. We address soft-in soft-out (SISO) decoding of linear and nonlinear (0, tc) codes and show that good (0, kappa) codes exist even when d(min) = 1. For the (0, tc) constrained AWGN channel, we present several rate (n - l)/n block codes that optimally tradeoff bit-error-rate performance with kappa. For the preceded dicode channel, we show that the systematic (0, n - 1) modulation codes are superior to most other rate (n - l)ln block codes in terms of error-rate performance, and their attractiveness is increased by the fact that they do not contribute any significant complexity to the overall system.
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