Differentially detected GMSK signals in CCI channels for mobilecellular telecommunication systems

The performance of conventional and decision feedback differential detection receivers for Gaussian minimum-shift keying (GMSK) signals transmitted in the presence of cochannel interference (CCI) and additive white Gaussian noise (AWGN) is evaluated. For the interference, the authors adopt a model which includes N statistically independent static as well as faded CCI. Various bit-error-rate (BER) performance evaluation results have indicated that the receiver under investigation performs better as compared to other more conventional receiver structures. Especially significant BER improvements are obtained for the static CCI channel. For example, it is shown that with a carrier-to-interference ratio of 14 dB, the performance of a 2-b decision feedback differential receiver outperforms a conventional 2-b differential detector by more than 14 dB (at a BER 10^-3). For the faded CCI, the improvement is less: mainly they result in error-floor reductions of about half an order of magnitude. By comparing the performance of static and faded CCI, it was also found that for a given C/I, the performance of the former would depend on the number of interferers, whereas this is not the case for the latter     

Precise error-rate analysis of bandwidth-efficient BPSK in Nakagami fading and cochannel interference

The bit-error rate (BER) of bandlimited binary phase-shift keying in a fading and cochannel interference (CCI) environment is derived for the case of perfect coherent detection. The fading-and-interference model assumed is general and of interest for microcellular system studies. The model allows both desired signal and interfering signals to experience arbitrary amounts of fading severity. A precise BER expression is derived using a characteristic function method. Using this accurate analytical result, the impact of the interfering users' fading severity on the desired user-error rate is examined. The BERs obtained under perfect coherent detection are also valid as lower performance bounds for practical realizable receivers where ideal coherent detection is difficult to implement. The error-rate performance of a novel bandwidth-efficient pulse shape is determined for the general fading and CCI environment. Analysis and numerical results show that the new pulse can provide better BER performance than the widely used raised-cosine pulse.     

Multiple-symbol differential detection with interference suppression

A multiple-symbol differential detector is formulated for M-ary differential phase-shift keying modulation where the channel state information is unknown to the receiver. The maximum-likelihood decision statistic is derived for the detector, and its performance is demonstrated by analysis and simulation. Under the Gaussian assumption for the aggregate interference plus noise, an exact expression for the symbol pairwise error probability is developed for M-ary differential phase-shift keying modulation over a diversity, slow-fading Rayleigh channel in the presence of an interference source. A simpler expression of the pairwise error probability is developed for the asymptotic case of large signal-to-noise ratio and small signal-to-interference ratio. It is shown that with an increasing observation interval, the performance of the differential detector over an unknown channel approaches that of optimum combining with known channel.     

Performance of antenna array systems with optimum combining in aRayleigh fading environment

The effect of cochannel interference on the performance of digital mobile radio systems in a Rayleigh fading environment is studied. The average bit error rate (BER) of an antenna array system with an optimum combining scheme that maximizes the output signal-to interference-plus-noise ratio is analyzed. BER expressions which are easy to evaluate numerically are derived for coherent binary phase-shift keying schemes in an environment with cochannel interference and noise     

Accurate performance evaluation of time-hopping and direct-sequence UWB systems in multi-user interference

An exact analysis is derived for precisely calculating the bit error probability of time-hopping and direct-sequence ultra-wideband systems with multi-user interference in an additive white Gaussian noise environment. The analytical expressions are validated by simulation and used to assess the accuracy of the Gaussian approximation proposed for estimating the performance of ultra-wideband communication systems. The Gaussian approximation is shown to be inaccurate for predicting the bit error rate for medium and large signal-to-noise ratio values. The performances of time-hopping and direct-sequence modulation schemes are accurately compared for different numbers of users and frame widths. It is shown that direct-sequence binary phase-shift keying outperforms time-hopping binary phase-shift keying for medium and large values of signal-to-noise ratio, which contradicts some previous results obtained using a Gaussian approximation.     

An Upper Bound Analysis for Coherent Phase-Shift Keying with Cochannel, Adjacent-Channel, and Intersymbol Interference

An error-probability upper-bound is developed for coherent phase-shift keying (CPSK) considering the combined effects of Gaussian noise, intersymbol interference (ISI), and several peak-limited circular-symmetric (CS) components such as adjacent-channel interference (ACI) and cochannel interference (CCI). In an earlier paper [1], an upper bound was introduced, based on the "maximizing probability density function" concept, for CPSK with Gaussian noise and a single CS interference. The natural extension of this type of bound to multiple mixed interferences-such as are encountered in practice-is given in this sequel. This multiple interferer bound, which is computationally simple to use, requires only the peak and mean-square values of the several interferences involved, and is optimal in the sense that no other bound, based solely on the same information, will be lower than it. Through examples we draw comparisons with previously available results, which show that the multiple-interference limited-peak bound, when applied to composite interference situations, can be an effective tool for system design and analysis.     

Performance of an Ultra-Wideband Communication System in the Presence of Narrowband BPSK- and QPSK-Modulated OFDM Interference

An analysis is derived for calculating the bit-error probability of an ultra-wideband (UWB) communication system operating with binary phase-shift keying and quaternary phase-shift keying narrowband interference in additive white Gaussian noise. The analytical expressions are valid when phase transitions of the interfering symbols can be ignored. The accuracy of the Gaussian approximation is assessed, and several modulation schemes proposed for UWB communication are evaluated in terms of capability of interference suppression.     

Asymptotic BEP and SEP of Quadratic Diversity Combining Receivers in Correlated Ricean Fading, Non?Gaussian Noise, and Interference

In this paper, we study the asymptotic behavior of the bit-error probability (BEP) and the symbol-error probability (SEP) of quadratic diversity combining schemes such as coherent maximum-ratio combining (MRC), differential equal-gain combining (EGC), and noncoherent combining (NC) in correlated Ricean fading and non-Gaussian noise, which in our definition also includes interference. We provide simple and easy-to-evaluate asymptotic BEP and SEP expressions which show that at high signal-to-noise ratios (SNRs) the performance of the considered combining schemes depends on certain moments of the noise and interference impairing the transmission. We derive general rules for calculation of these moments and we provide closed-form expressions for the moments of several practically important types of noise such as spatially dependent and spatially independent Gaussian mixture noise, correlated synchronous and asynchronous co-channel interference, and correlated Gaussian interference. From our asymptotic results we conclude that (a) the asymptotic performance loss of binary frequency-shift keying (BFSK) with NC compared to binary phase-shift keying (BPSK) with MRC is always 6 dB independent of the type of noise and the number of diversity branches, (b) the asymptotic performance loss of differential EGC compared to MRC is always 3 dB for additive white Gaussian noise but depends on the number of diversity branches and may be larger or smaller than 3 dB for other types of noise, and (c) not only fading correlation but also noise correlation negatively affects the performance of quadratic diversity combiners.     

Iterative Single-Antenna Interference Cancellation: Algorithms and Results

The capacity of cellular mobile communication systems can significantly be improved using single-antenna interference cancellation (SAIC) techniques. This paper analyzes several soft-input–soft-output (SISO) detectors in iterative SAIC receivers based on the turbo principle and compares their performances and complexities. Among them, the concurrent maximum a posteriori probability (MAP) receiver, which detects single-user signals and exchanges the soft information between cochannel users, is found to provide a good balance between performance and complexity. It can perform nearly the same as the joint MAP algorithm and achieve the single-user matched-filter bound (MFB), and its complexity only linearly increases with the number of cochannel signals. Other reduced-complexity algorithms, such as the Rake Gaussian (RG) approach and soft interference cancellation with MAP equalization (SIC-MAP), also achieve satisfactory performance for binary phase-shift keying (BPSK) modulation when the cochannel interference (CCI) signal can be decoded.      

Performance of GMSK in a land mobile radio channel

Discriminator detection of Gaussian minimum shift keying (GMSK) in a cellular mobile-communication channel is analyzed. The channel is modeled as a frequency-selective fast Rayleigh fading channel corrupted by additive white Gaussian noise (AWGN) and co-channel interference (CCI). A closed-form expression for the probability of error is derived. Numerical computation is used to obtain the GMSK bit error rate (BER) performance for various combinations of channel parameters. These results show that GMSK gives slightly better performance compared to that for π/4-quadrature phase shift keying (QPSK) previously reported in the literature     

MMSE diversity combining for wide-band digital cellular radio

A study of minimum mean-square error (MMSE) diversity combining for wide-band digital cellular radio, designed to combat intersymbol interference (ISI) caused by frequency selective fading is outlined. The systems analyzed use binary phase-shift keying (BPSK), quarternary phase-shift keying (QPSK) or 16-level quadrature amplitude modulation (16-QAM) with cosine rolloff spectral shaping, and space diversity with selection, maximal ratio or MMSE combining. A set of performance curves is presented for selected combining schemes showing the influence of the following system parameters: the diversity order (1 to 4); the cosine rolloff factor; the power delay spectrum (with its associated delay spread); the signal-to-interference ratio; and the number of modulation levels (2, 4 and 16)     

Two-Layer multistate Markov model for modeling a 1.8 GHz narrow-band wireless propagation channel in urban Taipei city

An accurate propagation channel model is crucial for evaluating the performance of a communication system. A propagation channel can be described by a Markov model with a finite number of states, each of which is considered to be quasi-stationary over a short period. This work proposes a two-layer multistate Markov model. Instead of a large Markov transition matrix used in a conventional single-layer Markov model, two small Markov transition matrices are employed by a two-layer Markov model to reduce the computational complexity of the model without increasing the memory requirements. The proposed approach characterizes the multiplicative processes of a propagation channel as shadowing and fast fading. Each type of fading is considered as several channel states and each of the states corresponds to a specific mixed Rayleigh-lognormal distribution. Numerical results reveal that the statistical properties of the simulated data are quite close to those obtained from the measurements; indeed, the proposed two-layer Markov model is more accurate and less complex, and requires less memory than the single-layer Markov model. Furthermore, the proposed two-layer Markov model enables the fading statistics and error probability performance of a quadrature phase-shift keying modulation scheme in a typical urban Taipei environment to be more accurately predicted. Besides, it can easily be applied to similar environmental scenarios.     

New results on selection diversity

The performances of selection diversity receiver structures in a slow flat Rayleigh-fading environment are assessed. A number of new and interesting results are obtained. Binary digital signaling using noncoherent frequency-shift keying (NCFSK), differential phase-shift keying (DPSK), coherent phase-shift keying (CPSK), and coherent frequency-shift keying (CFSK) is considered. The traditional analysis (the traditional selection diversity model) of a selection diversity system is based on choosing the branch with the largest signal-to-noise (SNR) power ratio while assuming that the noise power is constant across all branches. However, many practical selection systems choose the branch based on a largest signal-plus-noise (S+N selection) sample of a filter output. This paper comprises accurate analyses of such S+N selection systems. Results show that S+N selection systems perform better than predicted by the traditional selection diversity model. This is because the former includes the statistical nature of the noise, whereas the latter does not. The performance difference between the two models increases as the number of diversity branches increases. For each of DPSK and CPSK, the dual diversity equal gain (EG) combining and S+N selection systems perform identically. For each of NCFSK and CFSK, receiver structures which are equivalent when there is no diversity perform differently in a diversity environment. Certain dual diversity S+N selection systems give the same performances as EG combining or square law combining. The results are contingent upon perfect cophasing for the EG combining. In systems where estimates of the combining carrier phases contain noise, S+N selection outperforms EG combining for dual diversity     

Error rates of phase-modulated signals in multilink system with interference

The error probabilities for M-fold coherent and differentially coherent phase-shift keying signals passed through a multi-link system composed of cascaded linear amplifiers is found. At each link Gaussian noise and cochannel interference are additively injected.     

Differential phase shift keying in two-path Rayleigh channel withadjacent channel interference

A formula is derived for the error probability of M-ary differential phase-shift keying with differential phase detection in a two-path Rayleigh fading channel taking into account adjacent channel interference (ACI), cochannel interference (CCI), intersymbol interference (ISI), and Doppler frequency shift. Square-root Nyquist filters are used with roll-off, β, the transmitter and receiver as in the proposed US digital mobile radio system. The presence of the second path has a profound effect on increasing the bit error probability (BEP) because it causes ISI. In the absence of ISI, ACI has a smaller effect on BEP than CCI. In the presence of ISI their effect is essentially the same. For a given bit energy-to-noise ratio, the binary system has the lowest BEP; however, the bit rate is also the lowest for a given bandwidth. When the main interference is ACI or CCI, a quaternary system has a lower BEP than the octal system. When the main interference is ISI, this is reversed     

Weak-Signal DPSK Detection in Narrow-Band Impulsive Noise

The weak-signal receiver for binary differential phase-shift keying (DPSK) in additive noise is derived, and its performance in terms of the error probability in the most general narrow-band impulsive (nonGaussian) noise model, Middleton's class A noise, is analyzed.     

On the effect of cochannel interference on average error rates inNakagami-fading channels

The effect of cochannel interference on the performance of digital mobile radio systems in a Nakagami-fading channel is studied. Closed-form expressions are derived for the average probability of error of both coherent and noncoherent (differentially coherent) binary frequency shift keying and phase-shift keying schemes in an interference-limited system. The analysis assumes an arbitrary number of independent and identically distributed Nakagami interferers. The effect of maximal ratio combining diversity is also examined     

Explicit Analytical Expressions for Outage and Error Rate of Diversity Cellular Systems in the Presence of Multiple Interferers and Correlated Rayleigh Fading

The outage probability of maximal ratio combining diversity with an arbitrary number of antennas in the presence of an arbitrary number of cochannel interferers and thermal noise is derived when the branch gains of the desired user signal and interfering signals experience Rayleigh fading and have the same correlation matrix. Two special cases, when the correlation matrix is equicorrelated and when the correlation matrix has different eigenvalues, are considered for both the equal-power cochannel interference case and the unequal-power cochannel interference case. Further, the average bit-error rate of a coherent binary phase-shift keying (BPSK)-modulated cellular system using maximal ratio combining diversity in cochannel interference and correlated Rayleigh fading is derived. The effects of the average signal-to-noise ratio (SNR) and the average signal-power-to-interference-power ratio on the system performance are examined.     

Average error probability of digital cellular radio systems using MRC diversity in the presence of multiple interferers

The performance of digital cellular radio systems employing maximal ratio combining diversity is analyzed in a flat-fading channel with cochannel interference and additive white Gaussian noise. It is assumed that the desired signal may experience Rice fading (due to the presence of a line-of-sight component), while the interferers are Rayleigh-faded and may have similar or dissimilar average powers. Exact expressions are derived for the average symbol-error probability of M-ary phase-shift keying modulation in the presence of multiple independent Rayleigh-faded interferers.     

Nonlinear signal–noise interactions in dispersion-managed links with various modulation formats

Purpose of this paper is to highlight the principles of the nonlinear signal–noise interaction (NSNI) in dispersion-managed long-haul optical links and provide a quantitative understanding of the system parameters for which NSNI sets the nonlinear performance of the most popular intensity and phase modulation formats, namely on–off keying, differential binary and quadrature phase-shift keying and coherent quadrature phase-shift keying.