Bit Error Rate Analysis Research Articles

Parallel optical interconnection network for address transactions in large-scale cache coherent symmetric multiprocessors

The authors address the primary limitation of bandwidth demands for address transaction in future cache coherent symmetric multiprocessors (SMPs). As a solution, the authors propose a scalable address subnetwork called symmetric multiprocessor network (SYMNET) in which address requests and snoop responses of shared memory multiprocessors are implemented optically. As the address phase of the transaction is linked to the address bandwidth, which is the major bottleneck in SMPs, they focus only on the address subnetwork in this paper. SYMNET has the capability to pipeline address requests from successive processors, which results in increasing the available address bandwidth and lowering the latency of the network. An optical token is implemented to achieve mutual exclusion to the shared channel. This enables collisionless broadcast of multiple address requests. The simultaneous insertion of multiple address requests into the address subnetwork complicates cache coherence. A modified coherence protocol, called COSYM, was introduced to solve the coherence problem. The authors evaluated SYMNET with a subset of Splash-2 benchmarks running from 4-32 processors. Their simulation studies have shown 10%-67% improvement in execution time for various applications. It is also shown that the average latency for a transaction to complete using COSYM was 85% better than the electrical case. An overview of the proposed optical implementation of SYMNET is presented along with the theoretical power budget and bit-error rate analysis. This analysis shows that SYMNET can scale up to hundreds of processors while still using fast snoopy-based cache coherence protocols and that additional performance gains may be attained with further improvement in optical device technology.

Statistical analysis of fiber-optic CDMA communication systems. II. Incorporating multiple optical amplifiers

For pt. I see ibid., vol.20, no.8, p.1304-16 (2002). In this paper, we study and elaborate on the architectural consideration of using multiple optical amplifiers in an all-optical fiber-optic code-division multiple-access (FO-CDMA) network. Our study and considerations are based on obtaining the statistical characteristic functions for photon-counts of a string of output pulses that constitutes the address code in a FO-CDMA network. Optical orthogonal codes (OOCs) with minimum auto-and cross correlation are employed as the address or signature sequence codes. Our analysis is based on chip-synchronous interference only, which provides an upper bound on the system performance. Shot noise, thermal noise, and extinction ratio are considered in this analysis. Bit error rate (BER) results are obtained using two methods, namely, saddle-point and Gaussian approximations. From our BER analysis, we develop some insight into the optimum distribution of optical amplifiers and their corresponding gain setting parameter. Moreover, the effects of source power, code weight, number of users, bit rate, and amplified spontaneous emission noise are investigated.

BER analysis of synchronous fiber‐optic CDMA networks with suboptimal decision threshold

AbstractThe bit‐error rate (BER) of synchronous optical CDMA networks with a fixed (suboptimal) decision threshold is derived. The strategy used offers the advantage that the network need not dynamically monitor the number of users. The numerical results are satisfactory when compared with previous literature based on an optimal threshold. © 2002 John Wiley & Sons, Inc. Microwave Opt Technol Lett 32: 293–296, 2002.

Dual FDTS/DF: a unified approach to dual-detection and modification for MTR codes

Dual-detector decision-feedback schemes have recently gained considerable interest in magnetic recording. Schemes such as dual decision feedback equalization (DDFE), M2DFE, and dual FDTS/DF are dual-detector versions of DFE, multilevel DFE (MDFE), and fixed delay tree search with decision feedback fixed-delay tree search with decision feedback (FDTS/DF) detectors, respectively. At high recording densities, the dual-detector versions significantly improve bit-error-rate (BER) performance and reduce error propagation. In this paper, we first give a unified approach to the bit-error-rate analysis of dual-detector decision feedback schemes in an attempt to highlight their relationship, and then we show that the performance of dual FDTS/DF reduces to that of DDFE for /spl tau/=0 and reduces to that of M2DFE for /spl tau/=1 with d=1 code constraint. Further, we extend the dual FDTS/DF detection scheme to maximum transition run-length (MTR) coded channels. On the basis of both BER and error event analysis, we propose a modified dual FDTS/DF detection scheme for MTR-coded channels that improves BER performance. The new scheme modifies certain bits in the detection profess for preventing the dominant error event. Simulation results on 6/7 MTR-coded Lorentzian channel show that the modified detector gives around 1 dB SNR improvement over the advanced (trellis-coded extended partial response) TC-E/sup 2/PR detector.

Extended-window decorrelating detector for asynchronous CDMA channels and its performance analysis

We propose a new decorrelating detector for the asynchronous code-division multiple-access channels, called the extended-window decorrelating detector (EW-DD). The EW-DD helps to avoid the noncausality problem of the filter-type decorrelating detector and achieve a simplified detection by converting the asynchronous system into the synchronous one. It also helps to enhance the bit-error rate (BER) performances by utilizing one whole period of information of all users and by eliminating the multiple-access interference from the past data through feedback. Nevertheless, the computational complexity is kept lower than that of other existing decorrelating detectors. We carry out BER analysis of the EW-DD and demonstrate performance improvements of the EW-DD over other decorrelating detectors through computer simulations.

Mathematical modelling and BER analysis of 100 Gbs NOLM demultiplexer using a soliton-shaped pulse for control and data

A mathematical model for the non-linear optical loop mirror (NOLM) demultiplexer, operating with a soliton-shaped pulse for both control and data, is presented. The model can be used: to optimise system parameters (control pulse width, walk-off time etc.) for maximising peak transmittance of the switching profile; to calculate the switching profile width; and to estimate the switching profile through a new convolution approach. The simulation results are verified by numerically solving the non-linear Schrodinger equation. The NOLM model is then integrated into an optical receiver model for a bit error rate (BER) analysis. Simulation results show that BER, timing jitter noise and cross-talk are strongly dependent on the walk-off time between control and signal pulses in NOLM demultiplexing. The dependence of the BER on walk-off time agrees qualitatively with experimental results reported elsewhere.

Adaptive feedforward/feedback architectures for multiuser detection in high data rate wireless CDMA networks

We consider the design and performance of nonlinear minimum mean-square-error multiuser detectors for direct sequence code-division multiple-access (CDMA) networks. With multiple users transmitting asynchronously at high data rates over multipath fading channels, the detectors contend with both multiple-access interference (MAI) and intersymbol interference (ISI). The cyclostationarity of the MAI and ISI is exploited through a feedforward filter (FFF), which processes samples at the output of parallel chip-matched filters, and a feedback filter (FBF), which processes detected symbols. By altering the connectivity of the FFF and FBF, we define four architectures based on fully connected (FC) and nonconnected (NC) filters. Increased connectivity of the FFF gives each user access to more samples of the received signal, while increased connectivity of the FBF provides each user access to previous decisions of other users. We consider three methods for specifying the FFF sampling and propose a nonuniform FFF sampling scheme based on multipath ray tracking that can offer improved performance relative to uniform FFF sampling. For the FC architecture, we capitalize on the sharing of filter contents among users by deriving a multiuser recursive least squares (RLS) algorithm and direct matrix inversion approach, which determine the coefficients more efficiently than single-user algorithms. We estimate the uncoded bit-error rate (BER) of the feedforward/feedback detectors for CDMA systems with varying levels of power control and timing control for multipath channels with quasi-static Rayleigh fading. Simulations of packet-based QPSK transmission validate the theoretical BER analysis and demonstrate that the multiuser RLS adapted detectors train in several hundred symbols and avoid severe error propagation during data transmission mode.

Theoretical analysis of propagation characteristics in millimeter-wave intervehicle communication system

The paper presents an analysis of the multipath propagation characteristics of an intervehicle high-speed radio communication system using the ray-tracing method. A model of the millimeter-wave intervehicle propagation path accounting for vehicle traffic was developed and used to study the delay profile, while varying the distribution of the reception power and other multipath propagation characteristics. In the case of digital signal transmission between the vehicles, the probability density function of the carrier-to-noise power ratio (CNR) was determined and a theoretical analysis of the average bit error rate was performed by modeling the intervehicle propagation path using a Rice fading channel. By performing a numerical simulation, close relationships were established between the transmission power necessary to provide the required average bit error rate, the maximum transmission rate, the vehicle traffic, and the size of the antenna. A study of the improved signal propagation characteristics obtained by using diversity reception was also performed. It was found that by reducing the fading effect, an improvement in signal propagation characteristics can be expected. © 2000 Scripta Technica, Electron Comm Jpn Pt 2, 83(11): 33–43, 2000

Forward-link BER analysis of asynchronous cellular DS-CDMA over Nakagami-faded channels using combined PDF approach

A closed-form conditional probability density function (PDF) of the Nakagami-faded-interference-to-signal power ratio, given the exact location of the tagged mobile, is derived for integer values of Nakagami (1960) fade parameter m. The conditional PDF, whose coefficients can be computed efficiently in a recursive manner, significantly reduces the computational complexity of forward-link bit error rate (BER) evaluation of a direct-sequence code-division multiple-access (DS-CDMA) cellular system over a fading channel, BER curves reveal that the performance improvement of increasing m is not significant for m>4. Performance results for noninteger values of m can be estimated using the linear interpolation technique. With the derived BER expressions, a more realistic cellular model that takes into account the effects of nonidentical m and path-loss exponent is proposed and analyzed. By substituting appropriate values of m, the BER performance for a class of fading distributions such as Rayleigh and Ricean fading can be evaluated or approximated. In particular, the Nakagami approximation may be treated as a tight lower bound to the corresponding mathematically involved Ricean case.

Error probabilities of an FFH/BFSK self-normalizing receiver in a Rician fading channel with multitone jamming

We derive the analytical bit-error rate (BER) expressions for a fast frequency-hopped binary frequency-shift keying self-normalizing receiver over a fading channel with the worst-case band multitone jamming (MTJ) and additive white Gaussian noise (AWGN). The desired signal and MTJ are assumed to undergo independent Rician fading and our analyses, validated with simulation results, show that the system performance is not sensitive to different types of MTJ fading conditions. The self-normalizing receiver is found to be superior to the linear-combining receiver when the signal amplitude does not experience severe fading, while the converse is true under Rayleigh fading signal conditions. Under a Rician fading channel and AWGN conditions, the worst-case MTJ and the worst-case partial-band noise jamming are shown to have similar effects on the BER performance of the self-normalizing receiver with diversity.

Analysis of bit error rate of an optical clock extraction system based on self pulsating laser diodes

A theoretical analysis of the bit error rate (BER) in an optical clock extraction system using compact disk self-pulsating laser diodes (SPLDs) is performed. The dependence of the BER on the power of the incoming received data signal and on the detuning between the applied and free running SPLD pulse repetition frequencies is analysed. For a fixed detuning an optimum value of the input signal power at which the system BER is minimum is obtained. This minimum is due to the appearance of oscillations of the relative phase between the input and output signals at high values of the input power. An optimum value of the detuning at which the system BER is minimized is then identified. The influence of fluctuations of the input signal and data encoding on the system BER is also analysed.

Analysis of bit error rate of an optical clock extraction system based on self pulsating laser diodes

A theoretical analysis of the bit error rate (BER) in an optical clock extraction system using compact disk self-pulsating laser diodes (SPLDs) is performed. The dependence of the BER on the power of the incoming received data signal and on the detuning between the applied and free running SPLD pulse repetition frequencies is analysed. For a fixed detuning an optimum value of the input signal power at which the system BER is minimum is obtained. This minimum is due to the appearance of oscillations of the relative phase between the input and output signals at high values of the input power. An optimum value of the detuning at which the system BER is minimized is then identified. The influence of fluctuations of the input signal and data encoding on the system BER is also analysed.

Evaluation of partial-response maximum-likelihood detection for phase-change optical data storage

We describe the application of partial-response (PR) maximum-likelihood (ML) detection in rewritable phase-change optical data storage. The input to this detector, which is simulated in software, is the actual signal (without any equalization), reproduced from reading of the recorded sequence on an optical disk. The detection algorithm involves the extraction of the impulse response from the readout signal, PR equalization, the adjustment of gain and recovery of clock, ML sequence estimation with the Viterbi algorithm, and analysis of PRML performance. With a laser wavelength of 0.69 microm and an objective lens with a numerical aperture of 0.6, three linear densities are examined: 0.35 and 0.31 microm/bit without modulation code and 0.2 microm/bit with the (1, 7) modulation code. The equalized signal exhibits good eye patterns, especially at the densities of 0.35 and 0.31 microm/bit. Analyses of noise and bit-error rate indicate that jitter, rather than noise, is the main obstacle to realizing ultrahigh density in phase-change media with PRML detection. We also briefly discuss the problem of the inherent nonlinear effect in phase-change readout.

Multitone jamming of FH/BFSK in Rician channels

A new bit error rate (BER) expression for a noncoherent frequency-hopped binary-frequency-shift-keying (FH/BFSK) receiver in Rician channels, subjected to independent multitone and wideband noise interference, is derived. Unlike previously published analyzes, we combine the signal and jammer multipath components, the additive white Gaussian noise (AWGN), and other wideband interference as a single Gaussian process. This method leads to a BER expression which consists of only a single rather than a triple integral requiring numerical computation. We also present a new derivation of the probability density function (PDF) of the ratio of two Rician random variables, used in a previously published approximate BER analysis.

Study of BER of 64-QAM signal and OMI-window of feasible operation in analog/digital hybrid SCM transmission systems

In an analog/digital hybrid subcarrier multiplexed (SCM) transmission, carriers have generally been substituted for transmission signals such as AM vestigal sideband (AM-VSB) AM signals and M-QAM signals to evaluate transmission quality. In practical hybrid SCM, however, carriers are modulated by video signals or digital data, and the amplitude of a multiplexed signal composed of these modulation signals is more compressed than that of the carriers. This causes a decrease in the frequency of clipping of the multiplexed signal at the laser threshold. Consequently, the BER of the M-QAM signal in a practical hybrid SCM is lower than that of the experimental results for the same optical modulation index (OMI). However, it is difficult to prepare many practical modulation signals for experiments in a laboratory. Therefore, there is demand for a bit error rate (BER) analysis method for a multiplexed signal that includes the modulation signals needed to sufficiently evaluate the BER and determine the optimum OMI in a practical hybrid SCM. In this paper, we describe such a BER analysis method that can effectively estimate the BER in a practical hybrid SCM. In practical systems, the BER was greatly improved over the BER of a multiplexed signal of carriers. Furthermore, BER degradations due to clipping can be neglected for the AM signals in setting a practical OMI range. We used this analysis method to study the effective OMI range of AM and M-QAM signals. By assuming modulation signals, the OMI range is enlarged and, significantly, the OMI of an AM signal becomes suitable for setting practical values in AM-SCM transmission. This OMI range is more practical than those of former studies.

Bit error rate degradation due to a dip in the frequency response of an equalizing amplifier

This paper describes an analysis of bit error rate (BER) degradation due to a dip in the frequency response of an equalizing amplifier. An equivalent circuit simulation clarifies the BER degradation factors: (1) the output amplitude decrease of a specific binary sequence that has a repetition frequency equal to the dip frequency and (2) the oscillation in output voltage after rise and fall of signal level. A simple model shows that the center frequency and bandwidth of the dip as well as the depth of the dip strongly affect BER. A circuit simulation and experiment show that a dip at around one tenth the data rate causes the worst BER. The dip tolerance of a dc-suppressed transmission code is also discussed.

Forward-link analysis of cellular DS-CDMA over generalised fading channels using saddlepoint integration

The bit-error rate (BER) analysis of an asynchronous cellular direct-sequence code-division multiple-access (DS-CDMA) system with channel fading and random mobile locations often results in a multiintegral expression, even though the Gaussian approximation is applied. In the paper, saddlepoint integration (SPI) is proposed to simplify the analysis. The computational complexity grows only linearly with the number of interfering cells in the system, regardless of the number of mobiles in each cell. By making use of the derived expression, the BER performance for arbitrary Nakagami parameters and path-loss exponents is evaluated efficiently. Simulation results show that the SPI technique is accurate and reliable.

Decision feedback multiuser detection: a systematic approach

A systematic approach to decision feedback multiuser detection is introduced for the joint detection of symbols of K simultaneously transmitting users of a synchronous correlated waveform multiple-access (CWMA) channel with Gaussian noise. A new performance criterion called symmetric energy is defined which is a low-noise indicator of the joint error rate that at least one user is detected erroneously. Even the best linear detectors can perform poorly in terms of symmetric energy compared to the maximum-likelihood detector. A general class of decision feedback detectors (DFDs) is defined with O(K) implementational complexity per user. The symmetric energy of arbitrary DFD and bounds on their asymptotic effective energy (AEE) performance are obtained along with an exact bit-error rate and AEE analysis for the decorrelating DFD. The optimum DFD that maximizes symmetric energy is obtained. Each one of the K! optimum, decorrelating, and conventional DFDs, that correspond to the K! orders in which the users can be detected, are shown to outperform the linear optimum, decorrelating, and conventional detectors, respectively, in terms of symmetric energy. Moreover, algorithms are obtained for determining the choice of order of detection for the three DFDs which guarantee that they uniformly (user-wise) outperform their linear counterparts. In addition to optimality in symmetric energy, it is also shown that under certain conditions, the optimum DFD achieves the AEE performance of the exponentially complex maximum-likelihood detector for all users simultaneously. None of the results of this paper make the perfect feedback assumption. The implications of our work on power control for multiuser detection are also discussed.

Multichannel MLSE equalizer with parametric FIR channel identification

We propose a parametric finite impulse response (FIR) channel identification algorithm, apply the algorithm to a multichannel maximum likelihood sequential estimation (MLSE) equalizer using multiple antennas, and investigate the improvement in the overall bit error rate (BER) performance. By exploring the structure of the specular multipath channels, we are able to reduce the number of channel parameters to provide a better channel estimate for the MLSE equalizer. The analytic BER lower bounds of the proposed algorithm as well as those of several other conventional MLSE algorithms in the specular multipath Rayleigh-fading channels are derived. In the derivation, we consider the channel mismatch caused by the additive Gaussian noise and the finite-length channel approximation error. A handy-to-use simplified BER lower bound is also derived. Simulation results that illustrate the BER performance of the proposed algorithm in the global system for mobile communications (GSM) system are presented and compared to the analytic lower bounds.

BER analysis of 2PSK, 4PSK, and 16QAM with decision feedback channel estimation in frequency-selective slow Rayleigh fading

The average bit error rate (BER) performances of coherently detected 2PSK, 4PSK, and 16QAM in frequency-selective slow Rayleigh fading are analyzed. Decision feedback channel estimation (DFCE) is considered, in which the past L-received signal samples are remodulated to remove the modulation phase by feeding back the detected symbol sequence and then averaged. Analytical expressions for the conditional BER for the given transmitted symbol sequence are derived, and the average BER performances are evaluated by Monte Carlo simulation. It is shown that as L increases, the BER performance improves and approaches that of ideal coherent detection (with perfect channel estimation), and the loss in E/sub b//N/sub 0/ required for BER=0.1% relative to ideal coherent detection becomes as small as 0.4 dB when L=10. It is found that while the best performance is achieved by 2PSK and 4PSK when additive white Gaussian noise (AWGN) is the predominant cause of error (i.e., low E/sub b//N/sub 0/ regions), 16QAM modulation can achieve almost the same performance as 4PSK when the delay spread is the predominant cause of error (i.e., large E/sub b//N/sub 0/ regions), and the worst performance in this case is by 2PSK. The effects of power delay profile shape (double-spike, exponential, and Gaussian profiles assumed), rolloff factors of the Nyquist transmit/receive filters, and the transmitted symbol sequence pattern on the average BER performance are discussed.