Space-time convolutional codes, that provide maximum diversity and coding gain, are produced for cases with PSK modulation and various numbers of states and antennas. The codes are found using a new approach introduce...
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Space-time convolutional codes, that provide maximum diversity and coding gain, are produced for cases with PSK modulation and various numbers of states and antennas. The codes are found using a new approach introduced recently in a companion paper. The new approach provides an efficient method that allows a search for optimum codes for many practical problems. The new approach also provides a simple method for augmenting the criteria of maximum diversity and coding gain with a new measure which is shown to be extremely useful for evaluating code performance without extensive simulations. To validate the approach, an extensive set of simulation results are presented comparing the codes designed here to many other recently proposed space-time convolutional codes. The comparisons, given in terms of frame error rate (FER), indicate that our new method provides codes which yield excellent performance. The approach is especially useful for finding a handful of good codes. Selection among these codes can be made with a limited number of simulations for FER.
An unequal channel protection technique for JPEG2000 encoded images is proposed The proposed technique takes advantage of the hierarchical organization of the JPEG2000 bit-stream and protects only the most important p...
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An unequal channel protection technique for JPEG2000 encoded images is proposed The proposed technique takes advantage of the hierarchical organization of the JPEG2000 bit-stream and protects only the most important part of the compressed bit-stream, by means of a rate compatible punctured convolutional code. Both single-quality-layer and multiple-quality-layer compressions are considered The performance of this technique is evaluated under various noisy channel conditions. Simulation results show that the probability of correct decoding the received information and the quality of the reconstructed image are improved by the proposed technique.
There are two main strategies for decodingconvolutional codes: the well-known Viterbi algorithm and sequential decoding. This paper presents a comparison of Creeper, an algorithm for sequential decoding, and the Vite...
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ISBN:
(纸本)0780375106
There are two main strategies for decodingconvolutional codes: the well-known Viterbi algorithm and sequential decoding. This paper presents a comparison of Creeper, an algorithm for sequential decoding, and the Viterbi algorithm. Creeper is an algorithm which combines the best properties of both the stack and the Fano algorithms [1]. It requires less memory than the stack algorithm and has no backward moves as in the Fano algorithm. Some results of simulation show that Creeper is an interesting alternative to the Viterbi algorithm.
In this letter, we construct new encoder-independent upper bounds on the free distance for the rate (n-1)/n convolutional encoders that are formed by using rate 1/2 encoders and combined with 2(n)-level constant-envel...
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In this letter, we construct new encoder-independent upper bounds on the free distance for the rate (n-1)/n convolutional encoders that are formed by using rate 1/2 encoders and combined with 2(n)-level constant-envelope full-response CPFSK signals of single-h, by generalizing the bounding technique employed for the existing bounds. The new bounds coincide with the existing bounds for hless than or equal to0.25, but are generally better for h>0.25. We also present actual encoder combinations achieving the constructed new bounds with short constraint lengths.
The authors compare methods of reducing the co-channel interference on a DS-CDMA downlink signal by employing convolutional coding at the base station and a Viterbi decoder as the initial estimator for a parallel canc...
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The authors compare methods of reducing the co-channel interference on a DS-CDMA downlink signal by employing convolutional coding at the base station and a Viterbi decoder as the initial estimator for a parallel cancellation scheme. The combination of a matched filter and the Viterbi algorithm is shows to afford increased performance compared to equivalent bandwidth systems which do not use forward error correction. The use of a Wiener filter to collapse the spectrum of the spread signal leads to even greater capacity improvements. The systems discussed may be implemented with an affordable increase in receiver complexity and processing delay.
convolutional codes are used in digital communication systems to correct errors that occur during transmission. Their use is now commonplace, particularly in power-limited satellite and deep space communication system...
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convolutional codes are used in digital communication systems to correct errors that occur during transmission. Their use is now commonplace, particularly in power-limited satellite and deep space communication systems. Before the decoder can correctly decode the received continuous bit sequence, however, it must establish where codewords begin and end in this sequence, The process of determining codeword boundaries is called node synchronization. In this paper we develop a node synchronization algorithm based on metric difference values with the objectives of simple implementation and reliable performance. Focusing on satellite applications, we consider the constraint length 7, rate 1/2 convolutional code standardized by the National Aeronautics and Space Administration (NASA) and the European Space Agency (ESA);the approach we develop can be extended to other convolutional coding systems. Through simulation, we investigate the statistics of the received sequence, and highlight correlation in the sequence of the decoder metric values. In the light of these observations, we propose a synchronization algorithm, and develop a first-order analysis of this simple up/down counter framing technique. We recommend framing parameters based on both the analytical results and the expected response of the framing algorithm to correlated metric values. Development of a simple node synchronization algorithm that accommodates correlated metric values has not been reported previously in the literature. Simulation results confirm that reliable node synchronization is possible with this very simple approach. Copyright (C) 2000 John Wiley & Sons, Ltd.
In this paper, me consider convolutionally coded multicarrier direct-sequence code-division multiple access (DS/CDMA) systems using overlapping subchannels in time-limited and band-limited channels. A tight bound on t...
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In this paper, me consider convolutionally coded multicarrier direct-sequence code-division multiple access (DS/CDMA) systems using overlapping subchannels in time-limited and band-limited channels. A tight bound on the bit error probability of the decoder output is obtained in Rayleigh fading channels when the channel state information is ideally available. It is shown that the proposed system, the convolutionally coded overlapping multicarrier DS/CDMA system with a symbol mapping method utilizing the diversity, outperforms the conventional single carrier and nonoverlapping multicarrier systems using the same convolutional code. It is also shown that the proposed system can provide a larger system capacity and more effectively combat the partial band interference than the conventional ones.
This authors report on an investigation of possible source/channel coders for medical image transmission over a GSM cellular link. Two source coders (JPEG and EZW) and two channel coders (convolutional and turbo codes...
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This authors report on an investigation of possible source/channel coders for medical image transmission over a GSM cellular link. Two source coders (JPEG and EZW) and two channel coders (convolutional and turbo codes) are used. Analysis of the results indicates that EZW with convolutional coding gives the best performance, but some kind of automtic repeat on request (ARQ) is also needed.
The authors consider the use of non-binary convolutional codes in turbo coding. It is shown that quaternary codes can be advantageous, both from performance and complexity standpoints, but that higher-order codes may ...
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The authors consider the use of non-binary convolutional codes in turbo coding. It is shown that quaternary codes can be advantageous, both from performance and complexity standpoints, but that higher-order codes may not bring further improvement.
Future mobile communication systems should be able to support a wide range of services with different bit rates. Spread-spectrum code-division;ion multiple-access (CDMA) techniques have attracted much attention to be ...
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Future mobile communication systems should be able to support a wide range of services with different bit rates. Spread-spectrum code-division;ion multiple-access (CDMA) techniques have attracted much attention to be employed in such a system, Different techniques of CDMA could be used to map low-, medium-, and high-bit rates data into the same allocated bandwidth, including pure or wide-band CDMA, FDM/FH/CDMA, TDM/TH/CDMA, or a hybrid of these techniques. This paper investigates multirate pure CDMA using multiuser interference statistics derived for bath Gaussian and Rayleigh fading channels, Approximation of multiuser/multipath interference, in general, helps in the theoretical approach to error performance evaluation and, in particular, is quite useful for simulation approach in a fading channel, Some results of a multirate pure CDMA system with two services (low- and high-bit rates), for both BPSK and DPSK modulation schemes, are presented and compared.
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