Dual Diversity Reception Research Articles

NOMA-aided UAV Communications over Correlated Rician Shadowed Fading Channels

In this paper, non-orthogonal multiple access (NOMA) is investigated as a viable solution to address spectrum scarcity in unmanned aerial vehicle (UAV) communications. Specifically, the performance analysis of a NOMA-aided UAV communication system (UCS) with dual-diversity receivers on UAVs is conducted over bivariate Rician shadowed fading channels. Using newly obtained closed-form expressions for the joint probability density function (PDF) and joint cumulative distribution function (CDF), the outage probability and finite signal-to-noise ratio (SNR) diversity gain of NOMA-aided UCS are investigated within a stochastic geometry framework. A comprehensive analysis reveals that NOMA-aided UCSs can support more UAVs on the same spectrum than OMA-based systems, with similar outage probability. It is also shown that the cross correlation affects the diversity gain of NOMA-aided and OMA-based UCSs only at low SNR regimes. Therefore, NOMA-aided UCSs can be an attractive alternative over OMA-based UCSs in future wireless systems.

Performance analysis of coherent FSO system with SSC receiver

This paper analyzes the performance of coherent free-space optical (FSO) system employing the switch-and-stay (SSC) dual diversity receiver. The intensity fluctuations of the optical signal are modeled by Gamma-Gamma distribution, being caused by atmospheric turbulence. In addition, pointing errors are taken into account. Novel analytical expressions for the outage probability are derived. The general scenario of unbalanced average signal-to-noise ratios (SNRs) of independent and identically distributed SSC branches is considered, which is further simplified to the balanced SNR case. The effects of various system and channel parameters are investigated and discussed.

Linear Diversity Combining on Nakagami-0.5 Fading Channels

The Nakagami-0.5 distribution is an important special case of the Nakagami distribution as it represents a worst case fading scenario. This scenario is of particular significance for wireless applications with high quality of service requirements. The bit error probability (BEP) performances of three basic diversity combining schemes in Nakagami-0.5 fading are considered. It is shown that the error rate performances of dual branch equal gain and selection combining (SC) diversity are identical regardless of modulation format. It is also shown that L-branch maximal ratio combining diversity in Nakagami-0.5 fading has the same BEP performance as single branch reception in Nakagami-L/2 fading with L times the transmission power of each branch. A useful upper bound for the BEP of L-branch SC diversity in Nakagami-0.5 fading is also derived. The performance degradation for the worst case Nakagami-0.5 fading relative to Rayleigh fading can be as much as 24.6 dB for a dual-diversity receiver at target BEP of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-6</sup> . The additional resources required to restore a specified performance level, as increased channel signal-to-noise ratio and as number of additional diversity branches, are quantified. It is concluded that worst case Nakagami channels can result in dramatically poorer performance than Rayleigh channels, making proper system design and evaluation essential to achieve a required transmission quality.

New Results on the Statistics and the Capacity of Dual-Branch MRC and EGC Diversity in Correlated Lognormal Channels

This letter addresses the performance analysis of dual diversity reception systems in correlated lognormal fading channels with not-necessarily-identical parameters. More specifically, novel results on the probability density function (PDF) and the ergodic capacity of dual-branch maximal ratio combining (MRC) and equal gain combining (EGC) diversity receivers are presented. The proposed expressions find application in cost-sensitive diversity receiver implementations and handover designs.

On the Effect of Correlation on the Performance of Dual Diversity Receivers in Lognormal Fading

The bivariate lognormal distribution has been extensively utilized for modeling the fading gains of dual branch diversity receivers in both indoor and outdoor communication systems. The contribution of this letter is twofold: firstly, a general expression for the average bit-error probability (BEP) of diversity combining with two correlated lognormal fading branches is presented, based on a Gauss-Hermite sum approximation to the moment generating function. Secondly, using the proposed expression, it is shown that correlation can be viewed as an increase in the standard deviations of an equivalent diversity system with uncorrelated lognormal fading gains.

A New Approach to Bivariate Hoyt Distribution and its Application in Performance Analysis of Dual-Diversity Receivers

Novel infinite series based expressions for the bivariate Hoyt distribution are derived. More specifically, expressions for the joint probability density function (JPDF) and the joint cumulative distribution function (JCDF) of two Hoyt fading envelopes are derived, and proposed for use in performance analyses of dual-branch diversity receivers operating over correlated Hoyt fading channels. Using these reasonably simple and mathematically tractable expressions, we evaluate the performance of a dual-branch selection combining (SC) diversity receiver in terms of the outage probability (P out ) and the average bit error probability (ABEP) criteria. The ABEP performance is evaluated for binary differential phase-shift-keying (BDPSK) and binary non-coherent frequency-shift keying (BNFSK) modulation schemes.

An empirical model for dual-diversity reception over fixed wireless channels in suburban macrocell environments

Fixed wireless multipoint communication systems are increasingly being deployed in suburban macrocell environments, either to provide voice and data services to residences (wideband systems) or to supply automated meter reading and related supervisory control and data acquisition services (narrowband systems). Here, we show that a particularly simple yet complete first-order statistical characterization of two-branch diversity reception over fixed wireless channels can be given in terms of just five channel parameters: the average path gains and Ricean K-factors for each branch and the complex envelope correlation coefficient between the time-varying parts of the two path gains. We further show that all five parameters can be estimated from amplitude-only measurements of path gain vs. time, subject only to the assumption that the time-varying component of the path gain is complex Gaussian. We present representative sets of model parameters based upon data collected in typical suburban macrocell environments over time, location, and/or frequency using polarization diversity antennas. Because each of the model parameters, or its logarithm, is close to Gaussian, the set may be cast as a five-element vector of jointly random Gaussian processes. Despite obvious physical differences between the environments, the results show a remarkable consistency.

Performance analysis of system with selection combining over correlated Rician fading channels in the presence of cochannel interference

Dual-diversity receiver employing selection combining (SC) is often used in wireless communication systems due to its simplicity. Ability of the Rician model to describe fading in wireless communications is the reason to derive infinity-series representations for both the probability density function (PDF) and the cumulative distribution function (CDF) of output signal-to-interference ratio (SIR) at the dual SC receiver over correlated Rician fading channels in the presence of correlated Rayleigh distributed cochannel interference (CCI). These expressions are used to study wireless system performance criteria, such as outage probability and average bit error probability (ABEP).

Performance analysis of dual-diversity receivers over correlated generalised Gamma fading channels

The performance of dual-branch equal-gain combining (EGC) and maximal-ratio combining receivers operating over a composite correlated fading environment, modelled by the generalised Gamma (GG) distribution, is analysed. The moments of the output signal-to-noise ratio are derived in closed form for both types of receivers, and by employing the Pade approximants method, the average bit error probability is studied for a great variety of modulation schemes. Furthermore, based on the statistic of the product of two correlated GG random variables, a tight union upper bound for the outage probability of the EGC is obtained, whereas for the special case of Weibull fading a simpler bound is derived in closed form. The proposed mathematical analysis is complemented by various, numericaly evaluated performance results, whereas simulations verify the correctness of the proposed analysis.

Dual diversity over correlated Ricean fading channels

The performance of dual diversity receivers operating over correlated Ricean fading channels is analyzed. Using a previously derived rapidly converging infinite series representation for the bivariate Ricean probability density function, analytical expressions for the statistics of dual-branch selection combining, maximal-ratio combining, and equal-gain combining output signal-to-noise ratio (SNR) are derived. These expressions are employed to obtain novel analytical formulae for the average output SNR, amount of fading, average bit error probability, and outage probability. The proposed mathematical analysis is used to study various novel performance evaluation results with parameters of interest the fading severity, average input SNRs, and the correlation coefficient. The series convergence rate is also examined verifying the fast convergence of the analytical expressions. The accuracy of most of the theoretical performance evaluation results are validated by means of computer simulations.

Infinite-Series Representations Associated With the Bivariate Rician Distribution and Their Applications

Analytical expressions for the evaluation of the bivariate Rician cumulative distribution function (CDF), the covariance, and the characteristic function (CHF) are not known, despite their usefulness in wireless communications systems analysis. In this letter, motivated by the ability of the Rician model to describe fading in wireless communications, we derive infinite-series representations for the probability density function, the CDF, the covariance, and the CHF of two correlated Rician random variables. It is shown that the presented infinite-series expressions converge rapidly, and can be efficiently used to study several performance criteria for dual-diversity receivers operating over correlated Rician fading channels.

Bivariate generalised gamma distribution with arbitrary fading parameters

The three-parameter generalised gamma distribution is a versatile fading model that generalises or accurately approximates many of the commonly used distributions for multipath, shadow, and composite fading. It is difficult to evaluate the performance(s) of closely spaced dual-diversity receivers operating in such a channel because an analytical expression is not yet available for the bivariate correlated generalised gamma distribution. This report studies the bivariate generalised gamma distribution with arbitrary parameters. Expressions for the joint distribution and joint central moments are derived, and are used to obtain the outage probability for a dual-branch selection combining receiver over a correlated generalised gamma fading channel.

Incremental frequency, amplitude and phase tracker (IFAPT) for coherent demodulation over fast flat fading channels

The incremental frequency amplitude and phase tracker (IFAPT) is a recursive algorithm that estimates the parameters of piecewise-linear approximation to assumed continuous narrow-band signals. The parameters are amplitude, phase, and their respective slopes. The simple, recursive nature of IFAPT enables its direct interaction with recursive algorithms, such as the Viterbi and the BCJR in the APP SISO module, used for iteratively decoding concatenated codes. An augmented APP (A/sup 2/P/sup 2/)-module, containing IFAPT and BCJR algorithms, is here applied to iterative decoding serial concatenated convolutional codes under Rayleigh fading conditions with diversity reception. The bit-error rate under Rayleigh fading with dual diversity reception at E/sub bT//N/sub 0/=6 dB and f/sub d/T/sub s/=10/sup -2/ is 10/sup -4/, where E/sub bT/ is the total mean energy per bit in both diversity branches, f/sub d/ is the Doppler frequency, and T/sub s/ the symbol time.

Switched Dual Diversity Reception of M-ary DPSK Signals on Nakagami Fading Channels

The paper deals with dual diversity reception of M-ary differential phase-shift keying modulated signals in the presence of additive white Gaussian noise and Nakagami-distributed slow and nonselective fading. The performance of a switched diversity system is analysed and compared to that of the predetection selection diversity combining scheme. The general case of correlated diversity branches is considered, without restrictions on the fading severity parameter. Average symbol error rate formulas are analytically derived in terms of integral expressions that can be easily computed via numerical integration routines. Moreover, the numerical evaluation of the optimum switching threshold is carried out and the influence of the fading severity parameter, the branch correlation, and the cardinality of the symbol alphabet is analysed. Finally, three fixed switching threshold strategies that allow to obtain a satisfactory diversity gain are considered.

Optimum diversity combining and equalization in digital data transmission with applications to cellular mobile radio II. Numerical results

For Pt.I, see ibid., vol.40, no.5, p.885-94 (1992). The probability distributions of the data rates that can be supported by optimum receiver structures as well as the distribution of the Shannon capacity are studied. The dependences among the important system parameters are exhibited graphically for several illustrative examples including QPSK. At outage probabilities <10/sup -2/ and at operating SNRs of 15-25 dB, the Shannon capacity with optimal dual diversity reception is about 2 bit/s/Hz higher than without diversity. Alternatively, at typical operations of QPSK with 1.5 bit/s/Hz, two orders of magnitude in outage probability can be gained by diversity reception. Comparing the uncoded average probability of error for the optimized MSE systems, at most an order-of-magnitude difference is found among the different equalizers investigated except for the zero-forcing equalizer, whose performance is drastically inferior. Dual diversity can provide two-orders-of-magnitude improvement in the average error rate or in outage probability for the uncoded optimized systems.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Irreducible Error-Rate Performance of Phase-Shift Keyed Signals over Correlated Dual-Diversity Channels

Dual-diversity reception of 1- and 2-bit per baud differentially coherent phase-shift keyed signals over correlated Rayleigh fading channels is investigated. The mechanism that produces irreducible errors is signal distortion due to multiplicative noise. No additive noise is assumed to be present. As the fading correlation coefficient approaches unity or zero, the system error probability approaches that of single or dual independent diversity, respectively. For correlation as high as 0.7, nearly the entire improvement of dual independent diversity is obtained.

Error Rates for a Class of Binary Receivers

An error rate expression for a canonic binary receiver operating over channels that are characterized by both a nonfading component and a selectively fading random component and additive Gaussian noise is derived. The canonic receiver consists of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</tex> independent diversity branches. Most practical binary receivers for FSK, noisy-reference PSK, such as for example, DPSK, pilottone PSK, etc., are special cases of the canonic receiver. The results are applied to evaluate performance of incoherent detection of orthogonal FSK transmission over the HF channel that includes time and frequency selective fading and a nonfading component. The effect of intersymbol interference is also considered. The irreducible error rate for typical values of multipath and fading rates are illustrated for no diversity and dual diversity reception.

An experimental UHF dual-diversity receiver using a pre-detection combining system

The use of diversity reception has often been suggested as a means of overcoming multipath fading in mobile radio propagation, and various combining schemes have been used. An experimental 836 MHz dual channel, space diversity receiver has been built which brings to a common phase and combines two independent signals using a scheme of phase equalizing by multiple heterodyning. This paper describes the system and propagation tests using unmodulated carriers.

A Thin-Route Beyond-the-Horizon VHF System in the Middle East

The application of thin-route technique in an economical integrated small-scale VHF system in the 156-174-Mc band is described. The system provides point-to-point multi-channel voice, teletype and mobile communications between the main office of the Trans-Arabian Pipe Line Company in Beirut, Lebanon, and pumping stations and mobile units along the route of the pipeline through Lebanon, Syria, Jordan and Saudi Arabia. In addition, supervisory control and telemetering of 5000-HP combustion gas turbine pumping installations over portions of the system; including a 120-mile long link, is described. The terminals of this link and others, 90 to .05 miles long, are well beyond the horizon. Dual frequency diversity is employed. Several 250-watt transmitters and dual diversity receivers are duplexed on large arrays mounted on 200-foot selfsupporting towers. Two remote unattended relay stations are employed. System parameters, over-all propagation reliability, and plans for expansion as well as the economic attractiveness of a thin-route design for use in remote areas, are discussed.

Factors Affecting Modulation Techniques for VHF Scatter Systems

An experimental program at approximately 50 mc has been carried out over a 1295-km east-west ionospheric-scatter path to determine the comminucation capacity of the propagation medium using ordinary modulation techniques. Binary error-rate studies using dual-narrow-band frequency-shift-keyed terminal equipment were made to observe the dependence of error rate in scatter propagation on signal-to-noise ratio, multipath factors, and Doppler shifts. With respect to multipath limitation, using antennas of 6° beamwidth, error rate is found to be independent of transmission speed to 500 binary digits per second. Tests were made using dual-diversity narrow-beam rhombic antennas, and dual- and quadruple-diversity broad-beam Yagi antennas. The use of four Yagi antennas gave very promising results as compared to use of two narrow-beam antennas. Frequency shifts of 2, 4, and 6 kc were used to determine the effect of meteor Doppler components in the received signal, leading to recommendations for minimum frequency shift. Though actual modulation tests have so far been made at a frequency of 49.6 mc only, systematic observations of longdelay signals of the order of 10 to 80 msec were made at 30 and 40 mc, using pulse techniques. These delayed signals arrived at the receiver via the F <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> backscatter mode, and were occasionally of sufficient strength to cause binary errors for circuits operating in these frequency ranges. Studies of intelligibility for voice transmission were made using narrow-band frequency modulation and single-sideband modulation. Using 20-kw power, the frequencymodulation tests with dual-diversity receivers and narrow-beam rhombic antennas gave good results at levels of signal-to-noise ratio exceeded for 90 per cent of the year at 50 mc.