Evaluation of Multi-Valued Data Transmission in Two-Dimensional Symbol Mapping using Linear Mixture Model

The authors present line-coding methods that reduce the effects of dispersion-induced intersymbol interference (ISI) in high-speed (4 to 8 Gb/s) data transmission over direct-detection single-mode optical fibers. In addition to their use for synchronization purposes, line codes can be designed to eliminate certain worst-case patterns that would otherwise preclude reliable data transmission at very high rates. The authors study the use of these codes with directly modulated 1.55 mu m wavelength DFB (distributed feedback) lasers using conventional fiber (dispersion minimum at 1.3 mu m). Performance is quantified in terms of eye opening at the same information rate (which does not usually correspond to the same clock rate due to code overhead), normalized by any increased noise bandwidth. Examples of simple line codes (with symbol-by-symbol detection and feedback-free decoders) that significantly improve eye opening and thereby increase noise margins are given. The two examples presented at 4 Gb/s and 8 Gb/s realize respective coding gains of 1.65 dB and 5 dB over uncoded systems operating at the same data (information) rate. >

Current studies on modulation and detection schemes in molecular communication mainly focus on the scenarios with static transmitters and receivers. However, mobile molecular communication is needed in many envisioned applications, such as target tracking and drug delivery. Until now, investigations about mobile molecular communication have been limited. In this paper, a static transmitter and a mobile bacterium-based receiver performing random walk are considered. In this mobile scenario, the channel impulse response changes due to the dynamic change of the distance between the transmitter and the receiver. Detection schemes based on fixed distance fail in signal detection in such a scenario. Furthermore, the intersymbol interference (ISI) effect becomes more complex due to the dynamic character of the signal which makes the estimation and mitigation of the ISI even more difficult. In this paper, an adaptive ISI mitigation method and two adaptive detection schemes are proposed for this mobile scenario. In the proposed scheme, adaptive ISI mitigation, estimation of dynamic distance, and the corresponding impulse response reconstruction are performed in each symbol interval. Based on the dynamic channel impulse response in each interval, two adaptive detection schemes, concentration-based adaptive threshold detection and peak-time-based adaptive detection, are proposed for signal detection. Simulations demonstrate that the ISI effect is significantly reduced and the adaptive detection schemes are reliable and robust for mobile molecular communication.

In telecommunication, Intersymbol interference (ISI) is a form of distortion of a signal in which one symbol interferes with subsequent symbols. The presence of ISI in the system introduces errors in the decision device at the receiver output. Therefore, in the design of the transmitting and receiving filters, the objective is to minimize the effects of ISI, and thereby deliver the digital data to its destination with the smallest error rate possible. In this paper, we design a zero forcing equalizer, which is a type of linear equalizer used to mitigate the effects of ISI (Intersymbol Interference). The zero forcing equalizer does this by finding the inverse of the impulse response of the channel. The ISI can be studied using eye diagram, which overlays many samples of a signal and can give a graphical representation of the signal characteristics. In this paper the results have been shown with proper eye diagrams. In this paper we also investigate the bit error rate, which is used to estimate the performance characteristics of the zero forcing equalizer.

Discrete multitone modulation allows for a simple receiver structure if the impulse response of the communication channel is shorter than the cyclic prefix. In ADSL, a time-domain equalizer (TEQ) is used to fulfil this requirement. Without a TEQ, unwanted intercarrier interference (ICI) and intersymbol interference (ISI) occur. In this paper, quadratic forms are developed to calculate the contributions of ICI and ISI to the desired signal. Based on these expressions, a new method for calculating the TEQ coefficients, which minimizes the effects of ICI, ISI, and additive noise, is derived. Simulations in the context of ADSL compare the performance of this new algorithm with one that is state of the art.

This paper presents a new design technique of high-speed interconnects with controlled intersymbol interference (ISI) to create efficient signaling over a band-limited channel. Performance of high-speed electrical links is limited by conductor loss, dielectric dispersion, and reflections in the board, package, and connector. These nonidealities result in significant ISI. In current systems, the effect of ISI is either mitigated through complex equalization, signal conditioning, and coding techniques, or through costly impedance control and manufacturing processes. In the proposed approach, instead of eliminating ISI, we shape the response of the channel into a set of channel characteristics with controlled ISI using simple passive structures in the board and the package. The resulting controlled ISI is exploited at the transmitter and receiver to simplify the architecture of the system and to achieve high data rates. The techniques to design interconnects with controlled ISI are reasonably simple to implement in conventional interconnect technologies. Simulation examples are given to demonstrate the validity and advantages of the design technique using duobinary and analog multitone (AMT) signaling methods.

Free Space Optical (FSO) communication is an emerging technology to provide high bandwidth, secure and high quality communication. In this work we have determined the capacity of the Free Space Optical communication system with Multiple Input Multiple Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) technique under weak atmospheric turbulence conditions. To model the weak turbulence condition of the atmosphere lognormal channel model is used throughout the work. The capacity of MIMO-OFDM FSO is evaluated in the presence of Inter Symbol Interference (ISI) and is compared with MIMO FSO with ISI. The capacity of MIMO-OFDM FSO system increases in comparison to MIMO in the presence of ISI. It is found that the effect of ISI is mitigated by using OFDM and the capacity is enhanced. Since MIMO uses spatial divervity to mitigate the fading caused by turbulence hence the capacity of both MIMO-OFDM FSO and MIMO FSO also increases as the number of receiving antennas is increased.

This paper presents analytical results of the effects of jitter and inter symbol interference (ISI) on a millimeter-wave impulse radio (IR) transceiver, compared with performance of the developed 10-Gb/s W-band IR transmitter prototype. The compact and cost-effective IR transmitter consists of a pulse generator (PG) that creates a short pulse with a duration of <10 ps, a band-pass filter (BPF) that shapes the short pulse to the desired millimeter-wave pulse (wavelet), and a power amplifier (PA) which is deployed as an option. Jitters of the PG and ISI from the BPF are a great issue to make the IR transceiver robust and to obtain excellent performance. One analysis verified that, thanks to a novel retiming architecture, the random jitter and the data dependent jitter from the PG give only a small penalty of <0.5-dB increase in signal to noise ratio (SNR) for achieving a bit error rate (BER) of <10−12. The alternative analysis on the effect of ISI from the BPF indicated that using a Gaussian BPF enables transmission with a BER of <10−12 up to a data rate of 1.4 times as large as a bandwidth of the BPF, whereas the ISI analysis suggested that mismatching of the skirt characteristics of the developed BPF to those of a Gaussian BPF causes tail lobes following the wavelet, resulting in an on/off ratio of <15 dB and hence an SNR penalty of <6 dB.

Any communications signal suffers some degree of distortion during transmission. In high speed data communications, a significant portion of the distortion is ascribed to the presence of inter-symbol interference (ISI). Generally, an ISI channel can be modeled as a FIR filter. The ISI effect can thus be removed by inverse filtering the distorted signal at the receiver. The method presented in this paper, however, adopts a different equalization principle, which, rather than attempting to recover the original signal directly, adapts the decision rule in accordance with the channel statistics to achieve the same objective of retrieving the loss of BER performance.

High speed data transmission over communication channels distort the transmitted signals in both amplitude and phase due to presence of inter symbol interference (ISI). Other impairments like thermal noise, impulse noise and cross talk also cause further distortions to the received symbols. Adaptive equalization of the digital channels at the receiver removes/reduces the effects of such ISIs and attempts to recover the transmitted symbols. The multilayer perceptron (MLP), fuzzy logic (FL) and radial basis function (RBF) based equalizers are relatively new soft computing based equalizers which aim to minimize the ISI present in the channels particularly for nonlinear channels. However they suffer from long training time and undesirable local minima. In the present paper we propose a new adaptive channel equalizer using a novel bacterial foraging optimization (BFO) technique which is essentially a derivative free optimization tool. This algorithm has been suitably used to update the weights of the equalizer. The performance of the proposed equalizer has been evaluated and has been compared with its LMS based counter part. It is observed that the new equalizer offers improved performance both in terms of rate of convergence as well as bit-error-rate

Molecular Communication via Diffusion (MCvD) is an effective and energy efficient method for transmitting information across nanonetworks. In this paper, we focus on a diffusion-based communication system in which the reception process is absorption via receptors. Whenever a molecule hits a receiver it is removed from the environment. This kind of process is called a first passage process and it is more complicated than only using a diffusion process. In 3-D environments, obtaining an analytical solution for hitting time distribution for realistic cases is complicated; hence this paper presents an end-to-end simulator for the MCvD system that sends consecutive symbols.In MCvD, each symbol is modulated and demodulated in a time slot called the symbol duration; however, the long tail distribution of the hitting time is the main challenge that affects symbol detection. The molecules arriving in subsequent slots become an interference source when detection takes place. An end-to-end simulator enables us to analyze the effect of Inter Symbol Interference (ISI) without making any assumptions regarding the ISI. The proposed ISI cancellation technique utilizes decision feedback to compensate for the effect of the previously demodulated symbol. Three different modulation types are considered with the pulse, square, and cosine carrier waves. The results show that the proposed ISI mitigation technique improves the symbol detection performance of amplitude-based modulations more than frequency-based modulations. We also define the peak-to-average messenger molecule metric for quantifying and comparing the constraints on the transmitter and receiver nodes.

This paper proposes an equalization method based on multi-dimensional lattice filter for OFDM system and investigates the optimum reflection coefficient of such a multi dimensional lattice filter. It is known that OFDM transmission can decrease the effect of Inter Symbol Interference (ISI) by parallel transmission of orthogonal sub-carriers. However, conventional OFDM can’t compensate for Inter Carrier Interference (ICI). Proposals of 2 dimensional equalization using 2 dimensional filters for removing ISI and ICI have been made. However, those schemes are complex because the large number of taps necessary. This paper proposes 2 dimensional equalization using multi dimensional Infinite Impulse Response (IIR) lattice filters. These filters can be convergence faster and decrease iteration. The optimisation problem of inverse the characteristic function of path propagation is also dealt with. It is shown that the proposed system performs better than conventional systems making use of other equalization methods.

This paper describes the performance of the wave different method (WDM) for timing recovery in mobile radio communication. The mobile radio is modelled by the Rayleigh fading process where additive white Gaussian noise (AWGN), intersymbol interference (ISI) and timing jitter are assumed to be present. The study is based on computer simulation, and the effects of ISI and timing jitter at various vehicle speeds are presented. Simulation results show that for timing jitter of 50 Hz and peak-to-peak jitter amplitude of 1 symbol duration (T/sub b/) the performance is -32.4dB. The technique can be used to give good performance in the tracking of timing jitter. Also, the method can be modified to operate in a noisy environment.

In Single Frequency Networks, the effect of intersymbol interference (ISI) and inter-carrier interference (ICI) is great due to the delay spread of wireless channels is much longer than a cyclic prefix (CP). The performance of OFDM systems is degenerating seriously. This paper discusses a receiver design based on the implementation of a Decision Feed-back Equalizer (DFE). The proposed DFE receiver incorporates a Parallel Interference Canceller (PIC) as its feed-forward filter. The result shows that in long time delay or more serious fading multi-path, the proposed receiver has better performance for canceling ICI and ISI compared with the conventional OFDM receiver.

Exact analysis as well as asymptotic analysis, based on large-deviation theory (LDT), are developed to compute the bit-error rate (BER) for ultrafast avalanche-photodiode (APD) based optical receivers assuming on-off keying and direct detection. The effects of intersymbol interference (ISI), resulting from the APD's stochastic avalanche buildup time, as well as the APD's dead space are both included in the analysis. ISI becomes a limiting factor as the transmission rate approaches the detector's bandwidth, in which case the bit duration becomes comparable to APD's avalanche buildup time. Further, the effect of dead space becomes significant in high-speed APDs that employ thin avalanche multiplication regions. While the exact BER analysis at the generality considered here has not been reported heretofore, the asymptotic analysis is a major generalization of that developed by Letaief and Sadowsky [IEEE Trans. Inform. Theory, vol. 38, 1992], in which the LDT was used to estimate the BER assuming APDs with an instantaneous response (negligible avalanche buildup time) and no dead space. These results are compared with those obtained using the common Gaussian approximation approach showing the inadequacy of the Guassian approximation when ISI noise has strong presence.

Visible light communication (VLC) enables high speed wireless communication along with fulfilling the illumination requirement in the indoor environment. In this paper, we investigate the performance of a VLC system under multiple reflection condition. We minimize the effect of intersymbol interference (ISI) by using orthogonal frequency division multiplexing (OFDM). Particularly the use of guard interval (GI) in OFDM is utilized to mitigate intersymbol interference. We performed simulation using MATLAB to demonstrate the performance of our proposed VLC system. Simulation results show that the use of guard interval significantly reduces the ISI and hence improves bit error rate (BER) performance.