Future space missions will put severe constraints on communication links in terms of data rates, bandwidth occupancy, complexity, and performance. The requirements imposed by the new missions and their consequences on...
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Future space missions will put severe constraints on communication links in terms of data rates, bandwidth occupancy, complexity, and performance. The requirements imposed by the new missions and their consequences on channel code design are presented in the first part of the paper. All relevant issues, including code rates, frame lengths, modulation formats, Performance metrics, complexity, and others, are discussed. in the second part of the paper, long erasure correcting codes are presented and their properties explained. These codes operate at the upper layers of the space link protocol and constitute an attractive new frontier for zero packet loss in future space communications.
In the source coding problem with cost constraint, a cost function is defined over the code alphabet. This can be regarded as a noiseless channel coding problem with cost constraint. In this case, we will not distingu...
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In the source coding problem with cost constraint, a cost function is defined over the code alphabet. This can be regarded as a noiseless channel coding problem with cost constraint. In this case, we will not distinguish between the input alphabet and the output alphabet of the channel. However, we must distinguish them for a noisy channel. In the channel coding problem with cost constraint so far, the cost function is defined over the input alphabet of the noisy channel. In this paper, we define the cost function over the output alphabet of the channel. And, the cost is paid only after the received word is observed. Note that the cost is a random variable even if the codeword is fixed. We show the channel capacity with cost constraint defined over the output alphabet. Moreover, we generalize it to tolerate some decoding error and some cost overrun. Finally, we show that the cost constraint can be described on a subset of arbitrary set which may have no structure.
Starting from Shannon's celebrated 1948 channel coding theorem, we trace the evolution of channel coding from Hamming codes to capacity-approaching codes. We focus on the contributions that have led to the most si...
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Starting from Shannon's celebrated 1948 channel coding theorem, we trace the evolution of channel coding from Hamming codes to capacity-approaching codes. We focus on the contributions that have led to the most significant improvements in performance versus complexity for practical applications, particularly on the additive white Gaussian noise channel. We discuss algebraic block codes, and why they did not prove to be the way to get to the Shannon limit. We trace the antecedents of today's capacity-approaching codes: convolutional codes, concatenated codes, and other probabilistic coding schemes. Finally, we sketch some of the practical applications of these codes.
channel coding due to trellis modulation has been proved to be useful for bandlimited channels. However, these modulations, mostly designed with n-use of 2D signals, are primarily aimed at coding gain only. It is poin...
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channel coding due to trellis modulation has been proved to be useful for bandlimited channels. However, these modulations, mostly designed with n-use of 2D signals, are primarily aimed at coding gain only. It is pointed out that utilization of all available signal dimensions, which is limited by the time-bandwidth product, may improve the bandwidth efficiency and simultaneously bring an additional coding gain. Trellis coding with a spectrally efficient 4D signal set based on Q/sup 2/PSK is addressed. Without any expansion of the Q/sup 2/PSK signal set, a simple hand-designed 16-state trellis code provides a coding gain of 6.02 dB. With the same number of states in G. Ungergoeck\'s (1982) 8-PSK trellis, the gain is 4.1 dB. In low intersymbol interference situations, the bandwidth efficiency of this coded Q/sup 2/PSK is twice that of coded 8-PSK; if both operate at 2 b/s Hz and P/sub b/(E)=10/sup -5/, the coded Q/sup 2/PSK provides a saving of about 4 dB over the coded 8-PSK. Some fully connected trellises with an expanded signal due to 2-use of Q/sup 2/PSK signals are also presented. Two such codes ar rate-7/8 achieve a gain of 5.45 dB with only eight states.
For digital transmission over frequency-nonselective fading channels, data security can be obtained by error correction coding, but the coding scheme has to be adapted to the channel properties. For many vehicular app...
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For digital transmission over frequency-nonselective fading channels, data security can be obtained by error correction coding, but the coding scheme has to be adapted to the channel properties. For many vehicular applications, the range of possible vehicle speeds is large and in the UHF band the resulting Doppler frequency may not be small relative to the symbol rate-suggesting a differential detection scheme, Therefore, the channel coding should be robust against changes in Doppler spread, In this letter, a combination of a convolutional code (soft-decision decoding) and a Reed-Solomon (RS) code is considered, and the performance in a narrow-band Rayleigh-fading channel with differential quaternary phase shift keying (DQPSK) modulation without interleaving is evaluated as a function of signal-to-noise ratio (SNR) and Doppler spread by computer simulations, This transmission scheme is proved to have good performance over a large variety of vehicle speeds.
Optimization of multimedia transmissions over wireless channels should be aimed at maximizing the video quality perceived by the final user. For transmission of video sequences over an orthogonal frequency division mu...
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Optimization of multimedia transmissions over wireless channels should be aimed at maximizing the video quality perceived by the final user. For transmission of video sequences over an orthogonal frequency division multiplexing (OFDM) system in a slowly varying Rayleigh faded environment, we develop a cross-layer technique, based on a slice loss visibility (SLV) model used to evaluate the visual importance of each slice. In particular, taking into account the visibility scores available from the bitstream, depending on the scenario, we optimize the mapping of video slices within a 2-D time-frequency resource block and/or the channel code rates, in order to better protect more visually important slices. The proposed algorithm is investigated for several scenarios, with different levels of information about the channel available in the optimization process. Results demonstrate that, for different physical environments and different video sequences, the proposed algorithm outperforms baseline ones which do not take into account either the SLV or the CSI in the video transmission.
Atmospheric turbulence can cause a significant performance degradation in free space optical communication systems. An efficient solution could be to exploit the temporal diversity to improve the performance of the tr...
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Atmospheric turbulence can cause a significant performance degradation in free space optical communication systems. An efficient solution could be to exploit the temporal diversity to improve the performance of the transmission link. Depending on the tolerable delay latency, we can benefit from some degree of time diversity that we can exploit by employing channel coding and interleaving. In this paper, we investigate the efficiency of several channel coding techniques for different time diversity orders and turbulence conditions. We show that a simple convolutional code is a suitable choice in most cases as it makes a good compromise between decoding complexity and performance. We also study the receiver performance when the channel is estimated based on some training symbols. (C) 2008 Optical Society of America
In order to transmit the HDTV signal in 6 MHz, the four United States digital HDTV proponents, the DigiCipher, DSC-HDTV, ADTV and ATVA-P systems, are reducing the video data rate of HDTV to 15-17 Mb/s, a compression r...
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In order to transmit the HDTV signal in 6 MHz, the four United States digital HDTV proponents, the DigiCipher, DSC-HDTV, ADTV and ATVA-P systems, are reducing the video data rate of HDTV to 15-17 Mb/s, a compression ratio of approximately 60-70 times. The high compression dictates that channel coding be used to avoid block errors and multiframe error propagation. High efficiency in channel utilization required by the 6-MHz limitation means that the channel must be properly equalized and that the multipath and interfering signals must be severely limited. The channel coding techniques used for error reduction include data interleaving, error detection and replacement, and error correction at different levels of protection for bits and blocks of unequal importance.< >
In this work, channel decoding is considered as a promising way for improvement of cryptographic functions. Use of MAC/H-MAC values and digital signatures is analyzed in a context of code concatenation, together with ...
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In this work, channel decoding is considered as a promising way for improvement of cryptographic functions. Use of MAC/H-MAC values and digital signatures is analyzed in a context of code concatenation, together with convolutional codes using MAP decoding algorithm. Soft Input Decryption method, which uses L-values from channel decoder, presents an efficient method for integrating cryptography into decoding. The results of computer simulations that implement this method have been also presented. Additionally, the number of L-values verifications has been tested and compared with the theoretical results.
For the first time, the recently proposed "talkative power" paradigm combining power electronics and communication engineering is extended by channel coding and advanced receiver design aspects. In this conc...
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For the first time, the recently proposed "talkative power" paradigm combining power electronics and communication engineering is extended by channel coding and advanced receiver design aspects. In this concept, the pulses that control the duty cycle of switched-mode power converters are simultaneously used for data transmission by modifying the pulse phase, pulse frequency, pulse position or pulse width. The data sequence is embedded into the switching signal, similar to random modulation. The data can be used for example in point-to-point links, inside multi-port power converters, and for communication in networked power grids. As an application example a buck converter is studied. Its output voltage is numerically calculated for arbitrary two-level switching signals. The corresponding system model serves as a common framework for switching waveform design, receiver design, and performance analysis. The data sequence is represented by a small deterministic output voltage ripple. Various techniques to improve the data rate and the robustness of the communication are introduced, including line coding, a derivation of the optimum receiver in the sense of maximum-likelihood detection, and forward error correction coding as an option. Although emphasis is on a buck converter, the concept is applicable to other power converter topologies as well.
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