The interleaving span of coded frequency-hopped (FH) systems is often constrained to be smaller than the decoder memory length, i.e. nonideal interleaving is performed. An upper bound on the performance of a Viterbi d...
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The interleaving span of coded frequency-hopped (FH) systems is often constrained to be smaller than the decoder memory length, i.e. nonideal interleaving is performed. An upper bound on the performance of a Viterbi decoder of a convolutional code with nonideal interleaving is presented. A soft decision diversity combining technique is introduced, and the performance of combined convolutional and diversity coding subject to worst-case partial band noise jamming is investigated. Optimization of the FH system performance subject to constraints of allowed delay and synthesizer settling time provides the best combination of interleaving span and hopping rate. The FH system considered employs M-ary frequency-shift key (MFSK) modulation and noncoherent demodulation with 2-b soft decision based on Viterbi's ratio-threshold technique.
The performance of convolutionally encoded narrow-band digital FM with Viterbi decoding was considered in some detail by Simon [1] for a noncoherent limiter/discriminator (L/D) with integrate and dump (I&D) bit de...
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The performance of convolutionally encoded narrow-band digital FM with Viterbi decoding was considered in some detail by Simon [1] for a noncoherent limiter/discriminator (L/D) with integrate and dump (I&D) bit detection. Employing a new threshold receiver which averages the output of the I&D detector with the output of a sample and hold (S&H) detector, a 3-dB improvement over Simon's results for the bit error probability with FM clicks will be shown to be achievable. At low error rates, the performance of this new receiver is, moreover, comparable to that obtained when the clicks are exactly removed by Simon's hypothetical 'genie."
A serial concatenated convolutional and differential coding scheme is employed in a multi-user direct-sequence code-division multiple-access (DS-CDMA) system. The system consists of single-user detectors (SUDs), which...
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A serial concatenated convolutional and differential coding scheme is employed in a multi-user direct-sequence code-division multiple-access (DS-CDMA) system. The system consists of single-user detectors (SUDs), which are used to suppress multiple-access interference (MAI) with no requirement of other users' spreading codes, timing, or phase information. The differential code, treated as a convolutional code of code rate I and memory 1, does not sacrifice the coding efficiency and has the least number of states. The iterative process exchanges information between the differential decoder and the convolutional decoder. Both component decoders adopt the a posteriori probability (APP) algorithm. Numerical results in additive white Gaussian noise (AWGN) channels show that this concatenated coding scheme provides better performance and more flexibility than conventional convolutional codes in DS-CDMA systems, even in the sense of similar complexity. Further study shows that the performance of this coding scheme applied to DS-CDMA systems with SUDs improves by increasing the processing gain or the number of taps of the interference suppression filter. and degrades for higher near-far interfering power or additional near-far interfering users.
The bit error rate (BER) performance of a two-dimensional (2-D) RAKE receiver, in combination with transmit diversity on the downlink of a wide-band CDMA (W-CDMA) system, is presented. The analyses assume correlated f...
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The bit error rate (BER) performance of a two-dimensional (2-D) RAKE receiver, in combination with transmit diversity on the downlink of a wide-band CDMA (W-CDMA) system, is presented. The analyses assume correlated fading between receive antenna array elements, and an arbitrary number of independent but nonidentical resolvable multipaths combined by the RAKE receiver in the general Nakagami-m fading channel framework. The impact of the array configuration (e.g., the number of transmit antennas and receive antennas, the antenna element separation) and the operating environment parameters (such as the fading severity, angular spread and path delay profile) on the overall space-path diversity gain can be directly evaluated. In addition, the exact pairwise error probability of a convolutional coded system is obtained, and the coding gain of a space-path diversity receiver is quantified.
Atmospheric noise is caused by lightning and dominates other natural radio noise sources below 30 MHz. A wide-band atmospheric noise process appears as low-power Gaussian background process with bursts of high-power i...
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Atmospheric noise is caused by lightning and dominates other natural radio noise sources below 30 MHz. A wide-band atmospheric noise process appears as low-power Gaussian background process with bursts of high-power impulses. The impulses are due to nearby lightning and cause the first-order density of atmospheric noise to have longer tails than the Gaussian distribution. They also tend to occur in groups which means that the atmospheric noise channel has memory. Digital radio systems which operate on the atmospheric noise channel can use hard decisions to desensitize the receiver to the bursts, and forward error correction to recover those symbols which are received incorrectly. If these systems use a high degree of interleaving, then the channel can be modelled as a binary symmetric channel. However, many radio systems which operate below 30 MHz must minimize data delay and therefore interleaving depth must be chosen carefully. This paper uses two Markov chains to model the memory of the atmospheric noise channel. It derives the transition probabilities for these chains from atmospheric noise error processes which were recorded at 306 kHz. Then, it uses the models to estimate the probability of codeword error, and compares these estimates to codeword error rates which are obtained directly from the recorded error processes. These comparisons are made for the Golay code with a variety of bit interleaving depths, and for a Reed-Solomon code with a variety of symbol interleaving depths. Both Markov channel models predict the actual performance of the codes with much greater accuracy than the binary symmetric channel. This paper also includes some results for binary convolutional codes.
Consideration is given to the bit error probability performance of rate 1/2 convolutional codes in conjunction with quaternary phase shift keying (QPSK) modulation and maximum-likelihood Viterbi decoding on fully inte...
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Consideration is given to the bit error probability performance of rate 1/2 convolutional codes in conjunction with quaternary phase shift keying (QPSK) modulation and maximum-likelihood Viterbi decoding on fully interleaved Rician fading channels. Applying the generating function union bounding approach, an asymptotically tight analytic upper bound on the bit error probability performance is developed under the assumption of using the Viterbi decoder with perfect fading amplitude measurement. Bit error probability performance of constraint length K=3-7 codes with QPSK is numerically evaluated using the developed bound. Tightness of the bound is examined by means of computer simulation. The influence of perfect amplitude measurement on the performance of the Viterbi decoder is observed. A performance comparison with rate 1/2 codes with binary phase shift keying (BPSK) is provided.
The results of investigating the developed efficient procedures of iterative reception of serial turbo codes based on a simple convolutional code with two possible states of a code trellis are presented.
The results of investigating the developed efficient procedures of iterative reception of serial turbo codes based on a simple convolutional code with two possible states of a code trellis are presented.
Molecular communication (MC), which transmits information through molecules, has emerged as a promising technique to enable communication links between nanomachines. To establish information transmission using molecul...
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Molecular communication (MC), which transmits information through molecules, has emerged as a promising technique to enable communication links between nanomachines. To establish information transmission using molecules, synthetic biology through genetic circuits techniques can be utilized to construct biological components. Recent efforts on genetic circuits have produced many exciting MC systems and generated substantial insights. With basic gene regulatory modules and motifs, researchers are now constructing artificial networks with novel functions that will serve as building blocks in the MC system. In this paper, we investigate the design of genetic circuits to implement the convolutional codec in a diffusion-based MC channel with the concentration shift keying (CSK) transmission scheme. At the receiver, a majority-logic decoder is applied to decode the received symbols. These functions are completely realized in the field of biochemistry through the activation and inhibition of genes and biochemical reactions, rather than through classical electrical circuits. Biochemical simulations are used to verify the feasibility of the system and analyze the impairments caused by diffusion noise and chemical reaction noise of genetic circuits.
This work focuses on code design and code selection rules under power and decoding delay constraints for an antipodal (BPSK) modulated and convolutionally encoded communication system. The system operates over a slowl...
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This work focuses on code design and code selection rules under power and decoding delay constraints for an antipodal (BPSK) modulated and convolutionally encoded communication system. The system operates over a slowly fading AWGN channel, described here by the block-fading model. We specialize to perfect coherent detection with maximum likelihood decoding assuming ideal channel information (the instantaneous fading values). The dominant design criterion in this scenario is the code diversity level in terms of blocks while the standard Hamming distance plays a secondary role. A code design procedure, based on maximum distance separable (MDS) cyclic block codes is presented along with a code-search algorithm. The performance results of selected codes are assessed via simulation and compared to those achieved by Reed-Solomon codes with erasure and error decoding.
The main drawback of sequential decoding is the variability of its decoding effort which could cause decoding erasures. We propose and analyze in this correspondence an efficient bidirectional sequential decoding (BSD...
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The main drawback of sequential decoding is the variability of its decoding effort which could cause decoding erasures. We propose and analyze in this correspondence an efficient bidirectional sequential decoding (BSD) technique to alleviate this drawback. In the proposed BSD, two decoders are used;one is called a forward decoder (FD), and is used to search the tree from forward direction;while the other is called a backward decoder (ED), and is used for the backward search of the tree. Forward decoding and backward decoding are performed simultaneously, and stop whenever FD and ED merge at a common encoder state somewhere in the tree. The relationships between backward coding and forward coding are examined in detail. Good rate 1/2 convolutional codes, with memory m ranging from 2 to 25, suitable for bidirectional decoding found through extensive computer search, are provided. These codes possess the same distance properties from both forward and backward directions. It is found by means of extensive computer simulations as well as a heuristic argument that the advantage of BSD appears as a substantial decrease of the computational variability of sequential decoding. Our findings suggest that the Pareto exponent of unidirectional sequential decoding (USD) can be practically doubled by using BSD.
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