Performance Of Coherent Receiver Research Articles

Coherent Multiantenna Receiver for BPSK-Modulated Ambient Backscatter Tags

Ambient backscatter communication (AmBC) is an emerging communication technology enabling green Internet of Things deployments. The widespread acceptance of this paradigm is limited by the low signal-to-interference-plus-noise ratio (SINR) of the signal impinging on the receiver antenna due to the strong direct path interference and unknown ambient signal. The adverse impact of these two factors can be mitigated by using noncoherent multiantenna receivers, which are known to require a higher SINR to reach the bit-error-rate (BER) performance of coherent receivers. However, considering the unknown ambient signal, unknown location of AmBC tags, and varying channel conditions, coherent receivers for AmBC systems are rarely studied in the literature. In this article, a coherent multiantenna receiver, which requires no prior information of the ambient signal for decoding the binary-phase-shift-keying (BPSK) modulated signal, is presented. The performance of the proposed receiver is compared with an ideal coherent receiver that has perfect phase information, and also with the performance of a noncoherent receiver, which assumes distributions for ambient signal and phase offset caused by the excess length of the backscatter path. Comparative simulation results show the designed receiver can achieve the same BER performance of the ideal coherent receiver with 1-dB more SINR, which corresponds to 5-dB or more gain with respect to noncoherent reception of on-off-keying modulated signals. Variation in the detection performance with the tag location shows that the coverage area is in the close vicinity of the transmitter and a larger region around the receiver, which is consistent with the theoretical results.

Characteristics of Attention Bias in Patients With Depression Disorder, and the Influence of High Frequency Transcranial Magnetic Stimulation Therapy on the Attention Bias

We propose a general model to entirely describe XPM effects induced by 16QAM channels in hybrid QPSK/16QAM wavelength division multiplexed (WDM) systems. A power spectral density (PSD) formula is presented to predict the statistical properties of XPM effects at the end of dispersion management (DM) fiber links. We derive the analytical expression of phase error variance for optimizing block length of QPSK channel coherent receiver with decision-aided (DA) maximum-likelihood (ML) phase estimation (PE). With our theoretical analysis, the optimum block length can be employed to improve the performance of coherent receiver. Bit error rate (BER) performance in QPSK channel is evaluated and compared through both theoretical derivation and Monte Carlo simulation. The results show that by using the DA-ML with optimum block length, bit signal-to-noise ratio (SNR) improvement over DA-ML with fixed block length of 10, 20 and 40 at BER of 10−3 is 0.18 dB, 0.46 dB and 0.65 dB, respectively, when in-line residual dispersion is 0 ps/nm.

UWB Coherent Receiver Performance in a Vehicular Channel

UWB Coherent Receiver Performance in a Vehicular Channel

A flexible Mth power carrier phase estimation algorithm for coherent optical receiver

Although Mth power carrier phase estimation (PE) algorithm has been investigated intensively in coherent optical phase-shift-keying (PSK) system, block length effect impacts system performance and increases hardware complexity. In this paper, a flexible Mth power carrier PE algorithm is proposed to remove the effect of block length on system performance. We take into account the time-varying phase noise, instead of the assumption of constant phase noise over the entire observation interval. The weighted factors obtained from maximum likelihood method are introduced to eliminate the block length effect. Furthermore, we derive the analytical expression of phase error variance for the performance prediction of coherent receiver with the flexible Mth power. Bit error ratio (BER) performance of coherent receiver is evaluated and compared through both theoretical derivation and Monte Carlo simulation. The results show that by using the flexible Mth power algorithm, signal noise ratio (SNR) improvement over conventional Mth power algorithm with fixed block length of 20 and 40 at BER of 10−5 is 0.47dB and 2.18dB, when the linewidth per laser is 2MHz. By employing our flexible Mth power algorithm, SNR improvement over conventional Mth power algorithm with optimum block length will be larger as increasing laser linewidth . It means our flexible Mth algorithm is more effective for mitigating phase noise than the conventional Mth power algorithm.

Decision-aided maximum likelihood phase estimation with optimum block length in hybrid QPSK/16QAM coherent optical WDM systems

We propose a general model to entirely describe XPM effects induced by 16QAM channels in hybrid QPSK/16QAM wavelength division multiplexed (WDM) systems. A power spectral density (PSD) formula is presented to predict the statistical properties of XPM effects at the end of dispersion management (DM) fiber links. We derive the analytical expression of phase error variance for optimizing block length of QPSK channel coherent receiver with decision-aided (DA) maximum-likelihood (ML) phase estimation (PE). With our theoretical analysis, the optimum block length can be employed to improve the performance of coherent receiver. Bit error rate (BER) performance in QPSK channel is evaluated and compared through both theoretical derivation and Monte Carlo simulation. The results show that by using the DA-ML with optimum block length, bit signal-to-noise ratio (SNR) improvement over DA-ML with fixed block length of 10, 20 and 40 at BER of 10−3 is 0.18dB, 0.46dB and 0.65dB, respectively, when in-line residual dispersion is 0ps/nm.

Gain Flattening and Noise Figure Analysis of EDFA WDM Configuration for L-band Optical Communication using Wavelength Selective Attenuator

In Erbium Doped Fiber Amplifier, there are basically two main techniques for gain flattening: one is use external wavelength filters to flattenedthe gain while the other one relies on modifying the amplifying fiber properties to flattened the gain spectrum. The paper presents the study of simulation of a gain flattened EDFA WDM network for L-band optical communication using Wavelength Selective Attenuator .The design provides a high gain of 34.63dB at 1593nm and gain flatness (P-P) 0.38dB by using wavelength selective attenuator in the entire L-band at room temperature. Noise figure of less than 11dB was found in the entire 37nm (1571nm-1608nm) region very promisingly. The variation also been studied for various values of fiber lengths and pump powers. Full Text: PDF References M.Yamada, H.ono, T.Kananori, S.Sudo and Y.Ohishi, "Broadband and gain-flattened amplifier composed of a 1.55 ?m-band and a 1.58 ?m-band Er3+-doped fibre amplifier in a parallel configuration", Electron Lett., 33, 8 (1997). CrossRef Y.Sun, J.W.Sulhoff, A.K.Srivastava, J.L.Zyskind, T.A.Strasser, J.R.Pedrazzani, C.Wolf, J.Zhou, J.B.Judkins, R.P.Espindola, A.M.Vengsarkar, "Performance of coherent receiver with weighted despreading sequence for DS-CDMA", Electron Lett.33,23(1997) CrossRef Caugale Sachin et al, 2nd International Conference on Machanical ans electronics Engineering (ICMEE 2010) Goel Aditya et al, "Design of broadband EDFA for next generation optical networks", Journal of neural networks and application, pp.9-13 jan ? june 2011. L.L.Yi, L.Zhan, J.H.Ji,Q.H. Ye and Y.X.Xia, "Improvement of gain and noise figure in double-pass L-band EDFA by incorporating a fiber Bragg grating", IEEE Photonics Technology Letters,16,4,(2004). CrossRef M.Yamada, A.Mori, K.Kobasyashi, H.Ono, T.Kanamori, K.Oikawa, Y.Nishida and Y.Ohishi, "Gain-flattened tellurite-based EDFA with a flat amplification bandwidth of 76 nm", IEEE Photon.Technology Lett. 10, 9 (1998). CrossRef T.K.Bandhopadhya, Manish Saxena, Akash Tiwari, "Jitter?s Alpha Stable Distribution Behavior", International journal of Computer Technology and Electronics Engineering, 3,1,(2013). DirectLink M.Pal, M Paul, S.Bandyopadhyay, P.Biswas, K.Dasgupta and S.Bhadra, Fiber Optics Laboratory. CGCRI, Kolkata, India. 2012 Liu Kaixian, Du Juan, "Research of EDFA gain flattening based on chirped fiber Bragg grating", Proceeding of IC-BNMT 2009. CrossRef E. Desurvire, "Erbium Doped Fiber Amplifiers: Principles and Applications", New York: Wiley, 1994, pp. 268?270. K.Thyagarajan, A.Ghatak, "Fiber Optic Essentials", IEEE Press,John Wiley &Sons,Inc.2007

Performance of Coherent Receivers for PCTH-Based UWB System with Diversiform Modulation Schemes

The performances of a PCTH-based communication UWB system with diversiform modulation schemes are compared on the classic AWGN channel propagation and the realistic IEEE-UWB channel model. By employing different versions of modulation at the transmitters, the performances of an optimal receiver and a Rake receiver with various combining schemes are studied in this paper. The numerical results for several compared cases illustrate the tradeoff between transmitter diversity and receiver complexity. It is shown that the actual performance of the PAM-PCTH scheme can be better in both kinds of channel propagation. We also find that the PCTH-based UWB system with the Rake receiver has better performance than the conventional proposal for overcoming the multipath propagation effects in the UWB indoor environment.

Pilot-based estimation of time-varying multipath channels for coherent CDMA receivers

Reliable coherent wireless communication requires accurate estimation of the time-varying multipath channel. This paper addresses two issues in the context of direct-sequence code-division multiple access (CDMA) systems: (i) linear minimum-mean-squared-error (MMSE) channel estimation based on a pilot transmission and (ii) impact of channel estimation errors on coherent receiver performance. A simple characterization of the MMSE estimator in terms of a bank of filters is derived. A key channel characteristic controlling system performance is the normalized coherence time, which is approximately the number of symbols over which the channel remains strongly correlated. It is shown that the estimator performance is characterized by an effective signal-to-noise ratio (SNR)-the product of the pilot SNR and the normalized coherence time. A simple uniform averaging estimator is also proposed that is easy to implement and delivers near-optimal performance if properly designed. The receivers analyzed in this paper are based on a time-frequency RAKE structure that exploits joint multipath-Doppler diversity. It is shown that the overall receiver performance is controlled by two competing effects: shorter coherence times lead to degraded channel estimation but improved inherent receiver performance due to Doppler diversity, with opposite effects for longer coherence times. Our results demonstrate that exploiting Doppler diversity can significantly mitigate the error probability floors that plague conventional CDMA receivers under fast fading due to errors in channel estimation.

Performance of coherent receivers with hybrid SC/MRC over Nakagami-m fading channels

A performance analysis of two hybrid selective combining/maximal ratio combining (SC/MRC) diversity receivers over Nakagami-m (1960) fading channels with a flat multipath intensity profile is presented and numerically compared with that of the conventional SC and MRC schemes. Numerical results for particular cases of interest show that the bit error rate (BER) degradation arising from the use of hybrid SC/MRC instead of MRC is independent of the average signal-to-noise ratio (SNR) regardless of the severity of the fading and that MRC provides a higher rate of improvement than the hybrid SC/MRC as the severity of fading decreases.

Performance of coherent receiver with weighted despreading sequence for DS-CDMA

The performance of a DS-CDMA system using coherent receivers with the despreading sequences weighted by adjustable chip waveforms is presented. A new expression for the signal to interference plus noise ratio (SINR) of the decision variable is derived for the proposed receiver. When the system parameters are given, the derived SINR expression is determined only by one parameter of the weighted despreading sequence. As a result, the parameter can be simply tuned in practice for multiple access interference (MAI) rejection.

Asynchronous polarization diversity receivers for coherent optical communications: A performance review

AbstractThe performance of coherent receivers in optical communication systems is impaired by polarization mismatchings between the received optical signal and the local laser field. One of the most effective techniques to cope with such a phenomenon is the use of polarization‐diversity receivers which, at the cost of a higher complexity in the optical front‐end and a small performance degradation, guarantee insensitivity to changes in the state of polarization of the received signal. The goal of this paper is twofold: firstly, we present here an exact theoretical analysis of balanced polarization‐diversity receivers for ASK, FSK or DPSK modulation schemes in the shot‐noise‐limited regime, deriving closed‐form expressions for the receiver Bit Error Rate (BER) of each of the cited modulations. Secondly, we assess the sensitivity of the same receivers to a slowly‐varying frequency detuning of the heterodyne laser, in order to allow for a well‐aimed design of the Automatic Frequency Control (AFC) circuit of the local laser. This work was performed in the Framework of the “Telecommunications” project funded by the Italian National Research Council (CNR).

Weakly coherent optical systems using lasers with significant phase noise

Current theories for coherent receiver performance as affected by phase noise are compared, the main prediction of these theories are highlighted, and the reasons why many coherent system experiments have failed to approach the level of performance which is theoretically possible are considered. Different theoretical predictions are compared under idealized receiver conditions concerning the appropriate IF bandwidth, the penalty in receiver sensitivity resulting from laser phase noise, and other system properties. In general, good agreement is found. It is shown how these results differ for realistic receiver parameters, and optimized front-end design using tuning of parasitics is suggested.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Estimation of particle size distributions from forward scattering data

A novel approach to the estimation of particle size distributions is proposed and investigated. The proposed technique uses only forward scattering data as opposed to known methods using angle scattering. Our approach relies on the fact that, as coherent light travels through the random scattering medium, its coherence deteriorates. The degree of coherence degradation may be described in terms of the mutual intensity function (MIF). The shape of the MIF depends on the distribution of the particle size in the scattering medium. If a coherent receiver is used to detect forward scattered radiation, its output signal depends on the receiver diameter and on the MIF. Dependence of the receiver output signal on the receiver diameter carries information about the MIF and therefore about the particle size distribution. This information may be extracted by means of the techniques suggested in this paper. The suggested techniques are the outgrowth of our previously proposed method of estimating the particle size for the case of a monodispersive medium. As an example, we consider here the estimation of the Junge distribution. However, the method is applicable to other distributions as well. Since the proposed technique is based on an assumption of the form of the distribution, it will yield inaccurate estimates if the actual shape of the distribution function is different from the assumed. The distribution sensitivity of the technique is assessed by considering an extreme case of a flagrant assumption mistake when a monodispersive medium has been assumed while actually the device deals with a Junge-distributed polydispersive medium. This example yields ~50% relative errors in the produced estimates. Since practical distribution deviations should be less serious, the cited number can be considered as an upper bound for the device errors stemming from the distribution sensitivity. The byproducts of our analysis are the development of the MIF for Junge-distributed scattering media and the analysis of the coherent receiver performance for the case when the received light is scattered by Junge-distributed particles.