Aleksandar V. Mosić

Performance analyses of selection combining diversity receiver over α–μ fading channels in the presence of co-channel interference

An approach to the performance analyses of dual selection combining (SC) diversity receiver over correlated alpha - mu fading channels with the arbitrary parameters is presented. Fading between the diversity branches and interferers is correlated and distributed with alpha - mu distribution. Infinite series expressions are obtained for the output SIRs probability density function (PDF), cumulative distribution function (CDF) and an important measure of the systems performances, the outage probability (OP). An average error probability is efficiently evaluated for coherent and non-coherent modulation schemes such as coherent frequency-shift keying (CFSK), coherent phase-shift keying (CPSK), binary frequency-shift keying (BFSK) and binary differentially phase-shift keying (BDPSK). Numerical results are presented to show the effects of various parameters such as fading severity, input SIR unbalance and the level of correlation between received desired signals and interferences on systems performances.

SSC diversity receiver over correlated α-µ fading channels in the presence of cochannel interference

This paper studies the performances of a dual-branch switched-and-stay combining (SSC) diversity receiver, operating over correlated fading in the presence of cochannel interference (CCI). Very useful, novel, infinite series expressions are obtained for the output signal to interference ratios (SIRs) probability density function (PDF) and cumulative distribution function (CDF). The performance analysis is based on an outage probability (OP) and an average bit error probability (ASEP) criteria. ASEP is efficiently evaluated for modulation schemes such as noncoherent frequency-shift keying (NCFSK) and binary differentially phase-shift keying (BDPSK). The effects of various parameters, such as input SIR unbalance, the level of correlation between received desired signals and interferences, nonlinearity of the environment, and fading severity on systems performances are graphically presented and analyzed.

Robust and switched nonuniform scalar quantization of Gaussian source in a wide dynamic range of power

In this paper, robust and switched nonuniform scalar quantization model is analyzed for the case when the power of an input signal varies in a wide range. This model of scalar quantization is used in order to give higher quality by increasing signal-to-quantization noise ratio (SNRQ) in a wide range of signal volumes (variances) with respect to its necessary robustness over a broad range of input variances. We observed μ-low compandor implementation to achieve compromise between high-rate digitalization and variance adaptation. Accurate estimate of the input signal variance is needed when finding the best compressor function for a compandor implementation. It enables quantizers to be adapted to the maximal amplitudes of input signals. In addition, we found the expression for distortion, which we used to estimate the suggested model. In the nature of optimizing parameters of this model, we derived conclusions about the possibilities of this switched quantization application in speech processing. We analized influence of codebook size and number on quality of transmission, and compared ITU-T G711 standard with our model. The main contribution of this model is increasing of quality and the possibility of his applying for digitalization of continuous signals in wide range.

Performance Analysis of Dual-Branch Selection Combining Over Correlated Rician Fading Channels for Desired Signal and Cochannel Interference

System performances of dual selection combining over fading channels are analyzed. Fading between the diversity branches and between interferences is correlated and Rician distributed. Infinite series expressions for the probability density function, and the cumulative distribution function of the output signal-to-interference ratio are derived, which is the main contribution of this paper. Outage probability and the average bit error probability for noncoherent modulation schemes are also presented. Numerical results, presented in this paper, point out the effects of fading severity and correlation on the system performances.

Generalised approach for performance analysis of SIR-based multiple selection diversity over constant correlated α – µ fading channels

Selection combining (SC) is commonly used space-diversity technique in wireless communication systems to alleviate effects of channel fading and interference influence. In this paper, we analyse the performance of multibranch signal-to-interference-ratio (SIR)-based SC diversity over correlated α – µ fading channels with arbitrary parameters. The novel formulae for the probability density function (pdf) and cumulative distribution function (cdf) of output SIR are derived. Some numerical and simulation results are obtained pointing out the effects of fading severity, level of correlation, input SIR unbalance and diversity order to the outage probability. Also, the average error probability for several modulation schemes is numerically evaluated. Copyright

Optimisation of variable-length code for data compression of memoryless Laplacian source

In this study, the authors present an efficient technique for compression and coding of memoryless Laplacian sources, which uses variable-length code (VLC). That technique is based on the combination of two companding quantisers in the first case and three companding quantisers in the second case. These quantisers have disjoint support regions, different number of representation levels and different compressor functions. The closed-form expressions are obtained for the distortion, average bit rate and signal to quantisation noise ratio (SQNR). The presented numerical results point out the effects of rate-distortion (R-D) optimisation on the system performances. Since our model assumes the general case of Laplacian distribution, it has wide applications like the coding of speech and images. It is shown that the difference of SQNR of our model and classical companding quantiser based model is 2.8 dB for two quantisers and 4.2 dB in three quantisers model. The authors have also made a comparison between our model, combination of the optimal uniform quantiser and Huffmann lossless coder and combination of optimal companding quantiser and simple lossless coder.

Design of forward adaptive hybrid quantiser with Golomb-Rice code for compression of Gaussian source

This study proposes a novel model of hybrid quantiser composed of a uniform scalar quantiser and a non-uniform optimal companding scalar quantiser, both designed for a Gaussian source. We examine whether by appropriately designing a novel forward adaptive hybrid quantiser with Golomb–Rice code, one can achieve more sophisticated compression and a higher signal to quantisation noise ratio compared with the uniform quantiser with Golomb–Rice code. We observe which value of the bit rate should be chosen to provide high-quality quantisation. It is shown that the authors compression model can satisfy G.712 recommendation for high-quality quantisation achieving the compression of 1.68 bit/sample over the G.711 quantiser. In addition, for the average bit rate of 6.32 bit/sample their hybrid quantiser outperforms the uniform quantiser for 1.32 dB. The presented performances of the forward adaptive hybrid quantiser indicate that it should be of theoretical and practical significance in quantisation of the Gaussian source signals.

Semi–logarithmic and hybrid quantization of Laplacian source inwide range of variances

A novel semilogarithmic hybrid quantizer for non-uniform scalar quantization of Laplacian source, which consist of uniform quantizer and companding quantizer is introduced. Uniform quantizer has unit gain in area around zero. Companding quantizer is defined with a novel logarithm characteristic. Also an analysis of classic semilogarithmic A-law for various values of A parameter is provided. Comparation with classic semilogarithmic A-law is performed. The main advantage of hybrid quantizer is that number of representation levels for both uniform and companding quantizer are not unambiguously determined function of the A parameter value, as it is the case with classic semilogarithmic A companding characteristic. It is shown that by using hybrid quantizer, average of signal-to-quantization noise ratio SQNR quality obtained by using classic A companding law can be overachieved for 0.47 dB. Numbers of representation levels of hybrid quantizer are adapted to the input signal variances, in order to achieve high SQNR in a wide range of signal volumes (variances). By using this adaptation higher average SQNR quality of 2.52 dB could be achieved compared to classic A companding law. Forward adaptation of hybrid quantizer is analyzed and obtained performances correspond to adaptive classic A companding law case but possible advantage arises in simpler practical realization of hybrid quantizers. Obtained performances correspond to classic A-law companding case, because during the adaptation process, optimal values of parameter A are chosen. For each other A parameter values proposed hybrid quantizer provides better results. For value of A = 50 hybrid model has higher SQNR value for 0.79 dB

SSC Diversity Receiver over Correlated Open image in new window Fading Channels in the Presence of Cochannel Interference

This paper studies the performances of a dual-branch switched-and-stay combining (SSC) diversity receiver, operating over correlated fading in the presence of cochannel interference (CCI). Very useful, novel, infinite series expressions are obtained for the output signal to interference ratios (SIRs) probability density function (PDF) and cumulative distribution function (CDF). The performance analysis is based on an outage probability (OP) and an average bit error probability (ASEP) criteria. ASEP is efficiently evaluated for modulation schemes such as noncoherent frequency-shift keying (NCFSK) and binary differentially phase-shift keying (BDPSK). The effects of various parameters, such as input SIR unbalance, the level of correlation between received desired signals and interferences, nonlinearity of the environment, and fading severity on systems performances are graphically presented and analyzed.