Presence Of Additive White Gaussian Noise Research Articles

BER performance analysis of polar-coded FBMC/OQAM in the presence of AWGN and Nakagami-m fading channel

<abstract> <p>Offset quadrature amplitude modulation–based filter bank multicarrier (FBMC-OQAM) method is a promising technology for future wireless communication systems. It offers several advantages over traditional orthogonal frequency-division multiplexing (OFDM) modulation, including higher spectral efficiency, lower out-of-band emission, and improved robustness to time-frequency selective channels. Polar codes, a new class of error-correcting codes, have received much attention recently due to their ability to achieve the Shannon limit with practical decoding complexity. This paper analyzed and investigated the error rate performance of polar-coded FBMC-OQAM systems. Our results show that applying polar codes to FBMC-OQAM systems significantly improves the error rate. In addition, we found that employing random code interleavers can yield additional coding gains of up to 0.75 dB in additive white Gaussian noise (AWGN) and 2 dB in Nakagami-m fading channels. Our findings suggest that polar-coded FBMC-OQAM is a promising combination for future wireless communication systems. We also compared turbo-coded FBMC-OQAM for short code lengths, and our simulations showed that polar codes exhibit comparable error-correcting capabilities. These results will be of interest to researchers and engineers working on the advancement of future wireless communication systems.</p> </abstract>

Study on the performance of injection-locked single-loop optoelectronic oscillators in presence of additive white Gaussian noise

Abstract This paper presents a detailed study on the synchronization characteristics of a single-loop optoelectronic oscillator (OEO) under the influence of radiofrequency (RF) signal, which is contaminated with additive white Gaussian noise (AWGN). The influence of the AWGN on the performance of the injection-locked optoelectronic oscillator (IL-OEO) is investigated in terms of the probability of losing lock, average beat frequency, and frequency of skipping cycles. Fokker–Planck technique is utilized to derive the expression for the probability density function (PDF) of the phase difference between the injection RF signal and the OEO output signal. The probability of losing lock on the two sides of the IL-OEO oscillation frequency and the frequency of skipping cycles are calculated in terms of the signal-to-noise ratio (SNR). An expression for the phase noise spectrum of the IL-OEO is also presented. The analytical model predicts the phase noise of the IL-OEO at very low offset frequencies with the accuracy rate of 75 %, in the presence of AWGN. Experimental verifications are carried out to prove the validity of the proposed analytical model.

Blind recognition of alpha‐stable random carrier signals by an eavesdropper in random communication systems

Invisibility of alpha-stable (α-stable) noise as carrier signals, in the presence of additive white Gaussian noise (AWGN) as channel noise, is a key factor to ensure covert transmission by employing random communication systems (RCSs). This study introduces a novel blind recognition method for an eavesdropper to detect the presence of real-valued symmetric and skewed α-stable random carrier signals in the presence of AWGN. The introduced method is based on the proposed random carrier signal recogniser (RCSR), which consists of fractional lower-order auto-covariance block, threshold control block and the random carrier signal recognition indicator. The proposed RCSR first detects the possible presence of α-stable random carrier signals and then recognises the impulsiveness and skewness parameters, exploited by the transmitter and the intended receiver, to extract covertly conveyed binary information. However, the determined covert range can be adopted to perform secure transmission by RCSs. The simulation results reflect the simplicity of the proposed method as it is capable of performing effectively in real time by utilising extremely less number of observed samples.

Enhancement signal detection in underwater acoustic noise using level dependent estimation time-frequency de-noising technique

ABSTRACTIn sonar and underwater digital communication, optimal signal detection is imperative. In many applications, additive white Gaussian noise (AWGN) is assumed; thus, a linear correlator (LC), which is known to be optimal in the presence of AWGN, is normally used. However, underwater acoustic noise (UWAN) affects the reliability of signal detection in applications in which the noise originates from multiple sources and doesn’t follow the AWGN assumption. As a result, an LC detector performs poorly in tropical shallow waters. Accordingly, this study aims to develop a detection method for improving detection probability () by using a time–frequency denoising method based on the S-transform with multi–level threshold estimation. The UWAN used for the validation is sea truth data collected at Desaru beach on the eastern shore of Johor in Malaysia with the use of broadband hydrophones. The performances of four different detectors, namely, the proposed Gaussian noise injection detector (GNID), a locally optimal (LO) detector, a sign correlation (SC) detector, and a conventional LC detector, are evaluated according to their values. For a time-varying signal, given a false alarm probability of 0.01 and a value of 90 percent, the energy-to-noise ratios of the GNID, LO detector, SC detector, and LC detector are 8.89, 10.66, 12.7, and 12.5 dB, respectively. Among the four detectors, the GNID using the S-transform denoising method achieves the best performance.

Performance of Differential-Phase OFDM Systems over Selective Multipath Fading Channels

This paper investigates the performance of differential-phase Orthogonal Frequency Division Multiplexing (OFDM) over frequency-selective multipath Nakagami-m radio fading channels. A closed form for the average signal to noise/interference ratio in the presence of the selective multipath fading channel and additive white Gaussian noise (AWGN) is derived. The results reveal that the system performance is impacted by the interference between the adjacent OFDM frames in two successive signaling intervals which is called Inter-Symbol-Interference (ISI). In addition, the system will possibly be distorted when the orthogonality between the adjacent subcarriers is ceased, creating Inter-Channel-Interference (ICI). This paper also studies the bit-error-rate (BER) performance of the differential-phase OFDM system over the Nakagami-m channel in the presence of AWGN, ISI, and ICI under different conditions and parameters. Moreover, the effect of adding the guard period and the number of subchannels on the probability of error is analyzed. The IEEE 802.11a standard parameters with 64 subcarriers and a decaying exponential power delay profile with root-mean-square value of 129 ns are used in this study. The system performance is also simulated at different guard intervals, number of OFDM subcarriers, Nakagami severity parameter values, and different numbers of possible differential phases.

Improved underwater signal detection using efficient time–frequency de-noising technique and Pre-whitening filter

Optimal signal detection is important in sonar and underwater digital communication. However, a detailed knowledge of the statistics of the noise present is required to achieve optimal signal detection. Additive white Gaussian noise (AWGN) is assumed in many applications; thus, a linear correlator (LC), which is known to be optimal in the presence of AWGN, is normally used. However, underwater acoustic noise (UWAN) influences the reliability of signal detection in applications, in which the noise is non-white and non-Gaussian. As a result, an LC detector performs poorly in underwater applications. Accordingly, the Gaussian noise injection detector (GNID) is proposed in this study to improve detection probability (PD) based on a noise-enhanced signal detection using a pre-whitening filter, a time–frequency de-noising method based on S-transform, and an inverse whitening filter. Sea-truth data are collected at Desaru Beach on the eastern shore of Johor in Malaysia using broadband hydrophones. These data are used as UWAN to validate the proposed method. The performances of four different detectors, namely, the proposed GNID, a locally optimal (LO) detector, a sign correlation (SC) detector, and a conventional LC detector, are evaluated according to their PD values. Given a false alarm probability of 0.01 and PD value of 90%, the energy-to-noise ratios of the GNID are better than the LO, SC, and LC detectors by 1.77, 3.81, and 3.61dB, respectively, for a time-varying signal.

Quantum phase representation of Heisenberg limits and a minimally resourced quantum phase estimator

Within the quantum phase representation we derive Heisenberg limits, in closed form, for N00N states and two other classes of states that can perform better in terms of local performance metrics relevant for multiply-peaked distributions. One of these can also enhance the super-resolution factor beyond that of a N00N state of the same power, at the expense of diminished fringe visibility. An accurate phase estimation algorithm, which can be applied to the minimally resourced apparatus of a standard interferometer, is shown to be resilient to the presence of additive white-Gaussian noise (AWGN). In the limit of no AWGN the algorithm achieves over nine digits of accuracy for the case of a four-photon N00N state - orders of magnitude below its Heisenberg limit.

FIR digital filter-based ZCDPLL for carrier recovery

The objective of this work is to analyse the performance of the newly proposed two-tap FIR digital filter-based first-order zero-crossing digital phase-locked loop (ZCDPLL) in the absence or presence of additive white Gaussian noise (AWGN). The introduction of the two-tap FIR digital filter widens the lock range of a ZCDPLL and improves the loop’s operation in the presence of AWGN. The FIR digital filter tap coefficients affect the loop convergence behaviour and appropriate selection of those gains should be taken into consideration. The new proposed loop has wider locking range and faster acquisition time and reduces the phase error variations in the presence of noise.

Performance Analysis of DWMT Transceiver for ADSL Channel with Overlap FDE in Presence of AWGN, Crosstalk and Impulse Noise

Discrete wavelet Multi-tone (DWMT) was proposed to overcome the problems of Discrete Multi-tone (DMT) for wireline channels. DWMT based system poses more resistance against inter-symbol interference (ISI) because of tight filters and more spectral efficiency due to absence of cyclic prefix as compared to DMT based system. However, no equalization technique has been standardized yet for DWMT transceiver. In this paper, we are proposing Overlap frequency domain equalization (FDE) for DWMT transceiver for ADSL channel in presence of additive white Gaussian noise (AWGN), crosstalk and impulse noise (IN). From simulations results, we can analyze that Bit error rate (BER) performance of Time domain equalization (TDE) is comparable with Overlap FDE but the main advantage lies in lower computational complexity.

Sequence detection for MPSK/MQAM with adaptive phase tracking

In [P.Y. Kam, P. Sinha, A Viterbi-type algorithm for efficient estimation of MPSK sequences over the Gaussian channel with unknown carrier phase, IEEE Trans. Commun. COM-43 (1995) 2429–2433], we developed a Viterbi algorithm for efficient detection of M -ary phase-shift keyed (MPSK) sequences received over the additive, white, Gaussian noise (AWGN) channel with an unknown carrier phase. By assuming the carrier phase is constant over some L symbol intervals and using the sequence detection metric in [P.Y. Kam, Maximum-likelihood digital data sequence estimation over the Gaussian channel with unknown carrier phase, IEEE Trans. Commun. COM-35 (1987) 764–767] as the decoding metric, it approaches the performance of coherent detection, provided the observation interval L for forming the decoding metric is sufficiently long. However, this observation interval L is fixed, and chosen based on prior knowledge of the carrier phase characteristics. Thus, the metric is nonadaptive, and cannot be optimized when a priori statistical knowledge of the carrier phase is not available. The work here renders it adaptive by developing a recursive metric that is adapted on-line based on the received signals, without prior knowledge of the carrier phase characteristics. We first derive a metric for the maximum likelihood sequence detector for a general M -ary quadrature amplitude modulation (MQAM) sequence received in the presence of AWGN and an unknown, slowly- and randomly-varying carrier phase. To reduce the receiver complexity, a practical, suboptimal metric is obtained. A recursive form of the metric using adaptive reference estimation as in [P.Y. Kam, K.H. Chua, X. Yu, Adaptive symbol-by-symbol reception of MPSK on the Gaussian channel with unknown carrier phase characteristics, IEEE Trans. Commun. COM-46 (1998) 1275–1279], is proposed. Comparison between the proposed adaptive, recursive metric and those in the literature is provided. Simulation results using a random-walk carrier phase model show the superior performance of the adaptive sequence detector over the original nonadaptive sequence detector of [P.Y. Kam, P. Sinha, A Viterbi-type algorithm for efficient estimation of MPSK sequences over the Gaussian channel with unknown carrier phase, IEEE Trans. Commun., COM-43 (1995) 2429–2433].

Chaos Controlled ZCDPLL for Carrier Recovery in Noisy Channels

The objective of this work is to analyze the performance of the chaos controlled first order Zero Crossing Digital Phase Locked Loop (ZCDPLL) in the presence of Additive White Gaussian Noise (AWGN). The nonlinear behaviour of ZCDPLL shows a period doubling to its route to chaos. The amount of ZCDPLL divergency is measured and fed-back in a form of linear stabilization. The introduction of the chaos control widens the lock range of a ZCDPLL and improves the loop's operation in the presence of AWGN.

Chaotic time series prediction and additive white Gaussian noise

Taken's delay embedding theorem states that a pseudo state-space can be reconstructed from a time series consisting of observations of a chaotic process. However, experimental observations are inevitably corrupted by measurement noise, which can be modelled as Additive White Gaussian Noise (AWGN). This Letter analyses time series prediction in the presence of AWGN using the triangle inequality and the mean of the Nakagami distribution. It is shown that using more delay coordinates than those used by a typical delay embedding can improve prediction accuracy, when the mean magnitude of the input vector dominates the mean magnitude of AWGN.

Long correlation Gaussian random fields: Parameter estimation and noise reduction

In this paper, a parametric model for Gaussian random fields (GRFs) with long-correlation feature, namely the long correlation GRF (LC-GRF), is studied. Important properties of the model are derived and used for developing new parameter estimation algorithms and for constructing an optimum noise reduction filter. In particular, a novel iterative maximum likelihood estimation (MLE) algorithm is proposed for estimating the parameters of the model from a sample image, and the expectation-maximization (EM) algorithm is proposed for estimating the signal and noise variances given a noisy image. The optimal Wiener filter is derived making use of the parametric form of the model for the noise reduction under additive white Gaussian noise (WGN). Also the theoretic performance of the filter is obtained and its behavior is analyzed in terms of the long-correlation feature of the model. The effectiveness of the presented algorithms is demonstrated through experimental results on synthetic generated GRFs. An application to the restoration of cosmic microwave background (CMB) images in the presence of additive WGN is also presented.

Carrier synchronization for 3- and 4-bit-per-symbol optical transmission

We investigate carrier synchronization for coherent detection of optical signals encoding 3 and 4 bits/symbol. We consider the effects of laser phase noise and of additive white Gaussian noise (AWGN), which can arise from local oscillator (LO) shot noise or LO-spontaneous beat noise. We identify 8- and 16-ary quadrature amplitude modulation (QAM) schemes that perform well when the receiver phase-locked loop (PLL) tracks the instantaneous signal phase with moderate phase error. We propose implementations of 8- and 16-QAM transmitters using Mach-Zehnder (MZ) modulators. We outline a numerical method for computing the bit error rate (BER) of 8- and 16-QAM in the presence of AWGN and phase error. It is found that these schemes can tolerate phase-error standard deviations of 2.48/spl deg/ and 1.24/spl deg/, respectively, for a power penalty of 0.5 dB at a BER of 10/sup -9/. We propose a suitable PLL design and analyze its performance, taking account of laser phase noise, AWGN, and propagation delay within the PLL. Our analysis shows that the phase error depends on the constellation penalty, which is the mean power of constellation symbols times the mean inverse power. We establish a procedure for finding the optimal PLL natural frequency, and determine tolerable laser linewidths and PLL propagation delays. For zero propagation delay, 8- and 16-QAM can tolerate linewidth-to-bit-rate ratios of 1.8/spl times/10/sup -5/ and 1.4/spl times/10/sup -6/, respectively, assuming a total penalty of 1.0 dB.

Comparison of Bit Error Rate Performance of Multi Tone Channel Utilising De-OQPSK and De-Off Set 16 QAM with Guard Interval

Digital communications systems use Multi tone Channel (MC) transmission techniques with differentially encoded and differentially coherent demodulation. Today there are two principle MC application, one is for the high speed digital subscriber loop and the other is for the broadcasting of digital audio and video signals. In this study the comparison of multi carriers with OQPSK and Offset 16 QAM for high-bit rate wireless applications are considered. The comparison of Bit Error Rate (BER) performance of Multi tone Channel (MC) with offset quadrature amplitude modulation (Offset 16 QAM) and offset quadrature phase shift keying modulation (OQPSK) with guard interval in a fading environment is considered via the use of Monte Carlo simulation methods. BER results are presented for Offset 16 QAM using guard interval to immune the multi path delay for frequency Rayleigh fading channels and for two-path fading channels in the presence of Additive White Gaussian Noise (AWGN). The BER results are presented for Multi tone Channel (MC) with differentially Encoded offset 16 Quadrature Amplitude Modulation (offset 16 QAM) and MC with differentially Encoded offset quadrature phase shift keying modulation (OQPSK) using guard interval for frequency flat Rician channel in the presence of Additive White Gaussian Noise (AWGN). The performance of multitone systems is also compared with equivalent differentially Encoded offset quadrature amplitude modulation (Offset 16 QAM) and differentially Encoded offset quadrature phase shift keying modulation (OQPSK)with and without guard interval in the same fading environment.

On the distribution of the weighted sum of L independent Rician and Nakagami envelopes in the presence of AWGN

An alternative, unified, semi-analytical approach for the evaluation of the cumulative distribution function (cdf) of the weighted sum of L independent Rician (or Rayleigh as a special case) and m-Nakagami envelopes with or without the presence of Additive White Gaussian Noise (AWGN) is presented. The cdf is evaluated directly in a nested mode via the Hermite numerical integration technique. The proposed formulation avoids the calculation of complex functions and can be efficiently applied to practical wireless applications when L ≤ 3, using arbitrary statistical characteristics for the modeling parameters. Moreover, it can be also used to control the accuracy of other techniques when L > 3. Comments, comparison with other existing techniques and useful curves for several practical wireless applications such as the calculation of the error bounds for coding on fading channels in mobile satellite applications and the Equal Gain Combining (EGC), are also presented. Finally, the relation between the distribution of the sum of m-Nakagami and Rice envelopes is investigated and discussed.

On the application of sequence estimation algorithms in the digital compact cassette (DCC)

In the current digital compact cassette (DCC) recorder, a straightforward threshold detection scheme is applied which does not exploit the distance properties of the 8-to-10 modulation (ETM) code. More advanced detection schemes are investigated to see if they improve system performance. Two soft decision sequence estimation algorithms are considered: a fully-fledged Viterbi algorithm realizing maximum likelihood sequence estimation (MISE) and a suboptimal trellis detection algorithm. With either of the algorithms, an asymptotic gain of 3 dB versus threshold detection level in the presence of additive white Gaussian noise (AWGN) is expected. The suboptimal detection algorithm is based on the running digital sum (RDS) trellis underlying the ETM code. Performing the suboptimal algorithm requires a minimum of 48 additions, 19 comparisons, and a single table look-up for both detection and decoding of an ETM codeword, versus a minimum of 4234 additions, 421 comparisons, and 423 table look-ups for the fully-fledged algorithm. Compared to the fully-fledged scheme, the suboptimal algorithm leads to a large reduction in computational complexity. The performance of either of the algorithms in the presence of AWGN is determined by means of a computer simulation. The fully-fledged Viterbi algorithm achieves a gain of about 2.3 dB versus threshold detection level for symbol error rates in the order of 10/sup -4/ to 10/sup -5/. >

Coding of optical on-off keying signals impaired by phase noise

The benefits of coding for an optical communication system that employs binary on-off keying and heterodyne detection are quantified. The system is impaired by laser phase noise as well as by additive white Gaussian noise (AWGN). A receiver structure especially designed to mitigate the effects of phase noise in the presence of AWGN is assumed. This special receiver structure requires a wider-band front-end IF filter than would be required for a phase-noise-free signal. The results, computed for several different coding schemes, indicate that the benefits of coding are large and the costs are small. For a linewidth-to-bit-rate ratio ( beta T) of 0.64 (for example, 45 Mb/s and 29 MHz linewidth), a half-rate binary code that can correct 3 bit errors provides a 50% reduction in the required IF filter bandwidth (and, therefore, the required IF) and about 5 dB of reduction in required laser power. The benefits of coding are greatest under high- beta T conditions, corresponding to low bit rates where coders and decoders are most practical to implement.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Data transmission by frequency-hopped multilevel frequency shift keying

The possibility of utilizing frequency-hopped multilevel frequency shift keying (FH-MFSK) techniques for data transmission corrupted by additive white Gaussian noise (AWGN) is discussed. FH-MFSK is one of the many techniques used in spread spectrum systems and is a combination of frequency-hopping and time-hopping. In this system many users share a common frequency band using code-divisionmultiplexing. Each user is assigned an address and the message is modulated on to the address. The receiver, knowing the address, decodes the received signal and extracts the message. A microprocessor supervised experimental FH-MFSK system has been constructed and used to perform error-rate measurements in the presence of AWGN with deleted and delayed sample effects. Its capability for multi-user applications has been determined theoretically. The results show that FH-MFSK is a suitable technique for data transmission in the presence of AWGN.

Filters for the Detection of Binary Signaling: Optimization Using the Chernoff Bound

The probability of error in the detection of binary signaling by a linear receiver is upper bounded by the Chernoff bound, and a general relationship is obtained whose solution gives a receiver filter and threshold which minimize this bound. As an example, the detection of Poisson signaling in the presence of additive white-Gaussian noise is considered and the resulting filter lies between the optimum filter for Poisson signaling and a matched filter.