Presence Of ISI Research Articles

Specify capacity increasing as a fundamental problem of communication theory. Strategy development in the post-Shannon era. Part 3. Retrospective review of methods for capacity estimating of frequency-selective communication channels in the presence of ISI and using PSK-n and APSK-N-signal

Specify capacity increasing as a fundamental problem of communication theory. Strategy development in the post-Shannon era. Part 3. Retrospective review of methods for capacity estimating of frequency-selective communication channels in the presence of ISI and using PSK-n and APSK-N-signal

Specify capacity increasing as a fundamental problem of communication theory. Strategy development in the post-Shannon era. Part 2. Retrospective review of methods for receiving and processing signals in frequency-selective communication channels in the presence of ISI

Specify capacity increasing as a fundamental problem of communication theory. Strategy development in the post-Shannon era. Part 2. Retrospective review of methods for receiving and processing signals in frequency-selective communication channels in the presence of ISI

On Receiver Design for Diffusion-Based Molecular Communication

Diffusion-based communication refers to the transfer of information using molecules as message carriers whose propagation is governed by the laws of molecular diffusion. It has been identified that diffusion-based communication is one of the most promising solutions for end-to-end communication between nanoscale devices. In this paper, the design of a diffusion-based communication system considering stochastic signaling, arbitrary orders of channel memory, and noisy reception is proposed. The diffusion in the cases of one, two, and three dimensions are all considered. Three signal processing techniques for the molecular concentration with low computational complexity are proposed. For the detector design, both a low-complexity one-shot optimal detector for mutual information maximization and a near Maximum Likelihood (ML) sequence detector are proposed. To the best of our knowledge, our paper is the first that gives an analytical treatment of the signal processing, estimation, and detection problems for diffusion-based communication in the presence of ISI and reception noise. Numerical results indicate that the proposed signal processing technique followed by the one-shot detector achieves near-optimal throughput without the need of a priori information in both short-range and long-range diffusion-based communication scenarios, which suggests an ML sequence detector is not necessary. Furthermore, the proposed receiver design guarantees diffusion-based communication to operate without failure even in the case of infinite channel memory. A channel capacity of 1 bit per channel utilization can be ultimately achieved by extending the duration of the signaling interval.

Adaptive Channel Equalization Using Multiplicative Neural Network for Rayleigh Faded Channel

Problem statement: Digital transmission over band-limited communication channel largely suffers from ISIS and various noise sources. The presence of ISI and noise causes bit errors in the received signal. Equalization is necessary at the receiver to overcome these channel impairment to recover the original transmitted sequence. Traditionally equalization is considered as equivalent to inverse filtering and implemented using linear-perform under severe distortion conditions when Signal to Noise Ratio (SNR) is poor. Equalization can be considered as a non-linear classification problem and optimum solution is given by Bayesian solution. Non-linear techniques like Artificial Neutral Networks (ANN) are very good choice for non-linear classification problems. Several non-lines are equalizers have been implemented using ANN which outperformed LTE and solved the problem of equalization to the varying degree of sources. Approach: Forward neural network architecture with optimum number of nodes was used to achieve adaptive channel equalization. Summation at each node was replaced by multiplications which result in powerful mapping. The equalizer was tested on Rayleigh fading channel with a BPSK signal. Results: Results showed that proposed equalizer provides simplified architecture and improvement in the bit error rate at various levels of signal to noise ratio for Rayleigh faded channel. Conclusion: A high order feed forward network equalizer with multiplicative neuron is proposed in this study. Use of Multiplication allows direct computing of polynomial inputs and approximation with fewer nodes. Performance comparison in terms of network architecture and BER performance suggest the better classification capability of the proposed MNN equalizer over RRBF.

Graph-Based Decoding in the Presence of ISI

We propose an approximation of maximum-likelihood detection in ISI channels based on linear programming or message passing. We convert the detection problem into a binary decoding problem, which can be easily combined with LDPC decoding. We show that, for a certain class of channels and in the absence of coding, the proposed technique provides the exact ML solution without an exponential complexity in the size of channel memory, while for some other channels, this method has a non-diminishing probability of failure as SNR increases. Some analysis is provided for the error events of the proposed technique under linear programming.

Channel Estimation and Interference Cancellation for MIMO-OFDM Systems

This paper proposes a new channel estimation method and a new interference cancellation scheme for multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems in the presence of intersymbol interference (IS1). The proposed channel estimation method uses special training sequences (TSs) to have a desirable crest-factor of the transmitted training signal, and to prevent the influence of ISI on the channel estimation performance. By using the recommended training sequences, the ill-conditioned problem of the least square (LS) filter integrated in the proposed channel estimator can be avoided. The proposed interference cancellation scheme uses the estimated channel coefficients and the channel state information (CSI) to reproduce the interference components, which are then iteratively cancelled from the received signals. To reduced the error-floor of the demodulated symbols using for the calculations of the interference components, the so-called remodulation technique is also included in the proposed interference cancellation scheme. Simulation results show that the proposed channel estimation method outperforms conventional channel estimation methods, especially in the presence of ISI and if the signal-to-noise ratio (SNR) is larger than 15 dB. The combination of the proposed method with a space-time block code (STBC) to combat the interference influences results in an excellent system performance in terms of symbol error ratio (SER). In comparison with a STBC MIMO-OFDM system with sufficient guard interval (GI), this combination gains 1.52 dB of SNR at the same SER of 1.1 10 -6 even after performing only one iteration of interference cancellation.

Recursive blind symbol estimation of convolutionally coded cochannel signals

A recursive blind equalizer is presented that directly estimates the transmitted symbols of multiple cochannel signals in the presence of ISI. The algorithm exploits shift structure present in the data model and the finite alphabet property of the signals. The proposed method possesses a separation property that allows the symbol sequences for each user to be estimated independently of the others. Problematic issues surrounding unknown and mismatched channel lengths for the cochannel users can be handled effectively in the recursive equalizer. Additionally, if the cochannel signals are encoded prior to transmission, we show how the code structure can be incorporated into the recursive equalizer to improve its performance.

A computationally efficient FIR MMSE-DFE for CCI-impaired dispersive channels

Fast algorithms for the computation of the FIR MMSE-DFE in the presence of ISI, CCI, and colored noise are presented. Substantial reductions in computational complexity are achieved by using the powerful analytical tools of Cholesky factorization and displacement structure to fully exploit the structure of the problem. Both symbol-spaced and fractionally spaced feedforward filters are considered. Finally, we give a detailed complexity evaluation of the proposed algorithm for scenarios typical of the US TDMA digital cellular standard IS-54.

Innovations-based MLSE for Rayleigh fading channels

This paper deals with the use of the innovations approach for developing a general and practical MLSE algorithms for signals transmitted over Rayleigh fading channels. The proposed MLSE receiver can be implemented by a bank of FIR time-invariant filters followed by a Viterbi processor and is applicable to any practically modulated signal over either frequency-nonselective or selective, fast or slowly fading channels. Simulation results are presented that demonstrate the superiority of the innovations-based receiver over differential detection in the presence of fast fading. To further improve the error performance, the derived MLSE receiver is combined with diversity reception. The simulation also shows that the diversity technique results in a significant improvement of the error performance. A unified interpretation of MLSE of signals transmitted over both Gaussian noise channels in the presence of ISI and Rayleigh fading channels is obtained by using the innovations approach. >

Alternative trellis decoding for coded QAM in the presence of ISI

It is shown, for a set of trial ISI channels, that two reduced-search breadth-first trellis decoders, namely the M-algorithm and the newer T-algorithm, can provide performance equivalent to reduced state sequence estimation (RSSE) but at a substantially reduced computational load. These algorithms allow the optional use of powerful codes and/or Tomlinson precoding. >

Differential detection of optical heterodyne dpsk communication systems with intersymbol interference

AbstractThe system model for differential detection of optical heterodyne DPSK systems is set up, taking into account the effects of the IF filter and its production of ISI, the additive white Gaussian noise in the receiver and the quantum phase noise of lasers as well as the bandwidth‐time product (BT). We derive the probability distribution function of noise statistics for BT ≥ 1. The bit error rates (BER) are investigated in the presence of ISI. Numerical results for a 140‐Mbit /s system are presented for Gaussian IF filters. It is found that the laser linewidth requirement is the same as the system that does not consider the IF filter effect and the ISI it causes.

Beta-actions of catecholamines on the K-related currents of the bullfrog atrial muscle.

Effects of catecholamines on K-related membrane currents in the bullfrog atrial muscle were studied under voltage clamp using the double sucrose-gap technique. Isoproterenol (10(-8)-10(-6) M) and norepinephrine (5 X 10(-6)-10(-5) M) induced an outward shift of the basal current level and enhanced both the background current (Ib) for hyperpolarization and the instantaneous outward current for depolarization. There was an augmentation of the slow inward current (Isi) and the delayed outward current (Ix). The augmentation of Ix was induced with or without an increase in Isi, but different kinetics were involved. In the presence of Isi, beta-agonists produced a more marked augmentation of Ix for the intermediate voltages of depolarization where Isi was enhanced, and Co eliminated these effects. In the absence of Isi with Co, beta-agonists elicited an enhancement of Ix; however, the enhancement was greater for larger and longer depolarizations. All these effects were absent in the presence of propranolol (5 X 10(-7) M). These observations indicate that beta-agonists directly increase the background K current, and enhance the delayed outward current (Ix) via two different mechanisms; one is related to the augmentation of Isi and the other is not.