Space Diversity Reception Research Articles

Performance of different modulation scheme in free space optical transmission – A review

The Free-Space Optical (FSO) Communication (FSOC) system employs line-of-sight (LOS) technology. For long-distance transmission, FSO uses an optical bandwidth to attain data rates of gigabits per second (Gbps). In the FSO system, several vital difficulties comprising Atmospheric Turbulence (AT), Pointing Error (PE), along with weather-reliant atmospheric attenuation should be resolved. By adding more spatial degrees of freedom, the impacts of fading could be efficiently mitigated by a Multiple-Input, Multiple-Output (MIMO) FSO. In this research, the different modulation techniques’ performance (with or without Space Diversity Reception Technique (SDRT)) utilized in FSO systems is analyzed. Concerning Outage Probability (OP), Bit Error Rate (BER), along with Signal-To-Noise Ratio (SNR), the outcomes are analyzed. M-ary Quadrature Amplitude Modulation (M-ary QAM) and an Orthogonal Frequency-Division Multiplexing (OFDM)-centered FSO system is capable of long-distance communication (7000 m) at data rates ranging as of 4.1 Gbits/s (min) to 10.94 Gbits/s (max) as per the findings.

Performance Analysis and Enhancement of Free Space Optical Links for Developing State-of-the-Art Smart City Framework

In this paper, we have investigated and reported the performance of free-space optical (FSO) links operating in adverse atmospheric conditions. Since FSO links share operational similarity with fiber communication; hence, we believe that a cost-effective FSO framework can play a significant role in the transparent integration of high-speed network access backbones with the end-users. Different modulation formats, complemented with spatial diversity techniques, are discussed in this paper to strategize performance optimization of FSO links. Using bit error rate (BER) and signal-to-noise ratio (SNR) as performance metrics, it was found that binary phase-shift keying (BPSK) qualifies as the best technique modulation technique delivering SNR gain of 10 dB over on–off keying (OOK) operating link under similar channel conditions. Further performance optimization was achieved using space diversity reception wherein SNR witnessed a gain of 3 dB gain over the single-channel FSO link. In terms of application, the proposed model can help in developing a citizen-centric smart city ecosystem that can support seamless communication between heterogeneous smart devices.

Bit Error Ratio, Caused by Doppler Effect, for Systems of Space Diversity Reception

Bit Error Ratio, Caused by Doppler Effect, for Systems of Space Diversity Reception

INCREASED ACCURACY OF THE NAKAGAMI M PARAMETER MEASUREMENT METHOD BASED ON SPACE DIVERSITY RECEPTION

In this paper we will present increased accuracy measurement method for the Nakagami-m m parameter estimation, based on implementation of space diversity reception. Parameter m will be estimated in real time, based on the obtained values of first, second and third order moments of signal, measured by a proposed system. The obtained results will show an increase of accuracy obtained by using this method over the results obtained by using a standard measurement procedure, so it creates a potential to apply this measurement method for estimation of fading parameters in various propagation environments.

Investigation into diversity order at micro and/or macro level in gamma shadowed Nakagami‐m fading channels

AbstractRadio wave propagation through wireless channels is characterized by 4 main physical phenomena: reflection, diffraction, scattering, and absorption. Considerable efforts have been devoted to develop precise mathematical description of signal fluctuations which is very helpful in designing and evaluating the performance of wireless communication systems. A space diversity reception technique presents effective method for increasing channel capacity and upgrading transmission reliability at relatively low cost. In this paper, wireless communication system with maximal‐ratio combining (MRC) microdiversity and selection combining (SC) macrodiversity reception operating over correlated gamma shadowed Nakagami‐m fading channels is studied. Average bit error probability (ABEP), outage probability and average channel capacity, being significant and generally adopted performance measures, are employed to investigate how system performance is affected by the number of base stations and the number of antennas per base station.

Procedure for calculating the dependence of the energy concealment factor on carrier frequency selection for low-frequency satellite communications system

The paper analyzes high energy concealment factor techniques for satellite communications systems by lowering the carrier frequency (to f0 = 100…30 MHz) is carried out. According to research experiments, fading in communication channels with diversity reception is also determined by the influence of small-scale variations of the ionospheric total electron content. A procedure is developed for calculating the dependence of the energy concealment factor on carrier frequency selection for satellite communications system using space-diversity signal reception by two antennas. The calculation procedure is based on the standard deviation of small-scale variations of the ionospheric total electron content.

Reed Muller coded-cooperative diversity for multiple relays with signal space diversity and MRC reception at the destination

Recently, Reed---Muller (RM) codes have been investigated for half-duplex coded-cooperative relay communication systems. RM coded-cooperative (RMCC) diversity promised considerably low encoding and decoding complexity as compared to its predecessor channel codes. In this paper, we investigate the bit error rate (BER) performance of RMCC diversity for multiple relays operating in half-duplex mode with binary phase shift keying (BPSK) and quadrature amplitude modulation such as 4-QAM. In order to improve the BER performance of 4-QAM modulation, we use well known signal space diversity (SSD) technique in the proposed system. At the destination, maximal ratio combining is used for signal detection and joint majority logic decoding is used to recover information transmitted at the destination. Monte Carlo simulations show that the RMCC diversity gains increase manifolds with inclusion of multiple relays and for higher modulation i.e., 4-QAM, SSD provides additional diversity gains over the conventional 4-QAM system. Theoretical expressions for average BER are also derived and are validated with the help of Monte Carlo simulations.

Average bit error rate performance analysis of subcarrier intensity modulated MRC and EGC FSO systems with dual branches over M distribution turbulence channels

Based on the space diversity reception, the binary phase-shift keying (BPSK) modulated free space optical (FSO) system over Malaga (M) fading channels is investigated in detail. Under independently and identically distributed and independently and non-identically distributed dual branches, the analytical average bit error rate (ABER) expressions in terms of H-Fox function for maximal ratio combining (MRC) and equal gain combining (EGC) diversity techniques are derived, respectively, by transforming the modified Bessel function of the second kind into the integral form of Meijer G-function. Monte Carlo (MC) simulation is also provided to verify the accuracy of the presented models.

Model of the Aeronautical Service Channel in the Meter and Decimeter Wavelength Bands for Adaptive Space Diversity Reception

We propose a model of the formation of signals generated by spaced diverse antennas operated in the meter and decimeter wavelength bands and used for the aeronautical service channel. This model is used to assess potential capabilities of spatial interference cancelers in a multi-beam aeronautical communication channel.

Enhanced performance of single-input multiple-output visible light communication system utilizing space diversity technology

Contradictions among receiver optical power, bandwidth of photodiode, and transmission distance are ubiquitous in visible light communication (VLC) systems. In order to moderate such contradictions and improve the performance of VLC systems, we proposed a space diversity receiver for a light-emitting diode (LED)-based VLC system and experimentally demonstrated the highest data rate for an RGB LED with a 1.4 Gbit/s data rate employing two detectors located in different space positions at the same time. The maximal ratio combining algorithm was used in the VLC system for the first time. As a result, the bit error ratios of the receivers can be reduced by 48.08 dB (red LED), 12.04 dB (green LED), and 27.48 dB (blue LED) compared with any separate detector. The performance of the VLC system was significantly improved. It turned out that it was highly desirable to use multiantennas in the VLC system.

Alamouti space–time block coded hierarchical modulation with signal space diversity and MRC reception in Nakagami‐ m fading channel

This study presents a novel approach to an Alamouti transmission scheme for hierarchical modulation (HM) with signal space diversity (SSD) in a Nakagami-m fading channel. The bit-error-rate (BER) performance of the proposed system is determined using the nearest neighbourhood (NN) approximation approach and is briefly discussed. In addition, a reduced complexity maximum likelihood-based decoder is proposed. Simulation results verify a significant BER improvement of the proposed system when compared with previously implemented schemes as well as the accuracy of the NN approximation and the proposed detector. Specifically, gains of up to 8 dB at a BER of 1 × 10−5 for both base and refinement bits have been observed when comparing the proposed HM SSD Alamouti scheme with an HM SSD scheme without Alamouti transmit diversity at a hierarchy of α = 4, channel conditions at m = 1 and N = 1 receiver antennas. Additional results for varying hierarchy at increasing number of receiver antennas and improving channel conditions is also presented. The performance of the proposed reduced complexity decoder is also presented as well as its complexity reduction analysed.

Two-Branch Selection in Wireless Space-Diversity Reception: An Upper Bound for its Output Power

This paper analytically derives an upper bound for the output power of two-sensor branch-selection (a.k.a. "antenna selection," "selection diversity," or "selection combining") reception, based on an empirically proven "geometric model" of the wireless propagation channel. The derived upper bound is explicit in terms of the geometric model parameters. The tightness of this upper bound is verified by Monte Carlo simulations.

HDTV Mobile Reception Performance for Digital Terrestrial Television Broadcasting System ISDB-T : Simulation Study on 8-Branch Space Diversity Reception with Iterative Decoding(<Special Survey>Improvement of Reliability and Stability of Transmitting Equipment and Network at Digital Age)

HDTV Mobile Reception Performance for Digital Terrestrial Television Broadcasting System ISDB-T : Simulation Study on 8-Branch Space Diversity Reception with Iterative Decoding(<Special Survey>Improvement of Reliability and Stability of Transmitting Equipment and Network at Digital Age)

Diversity reception of hydroacoustic signals from the results of experiments in the Black Sea

The results are presented of an experimental study of spatial and frequency correlation of amplitude fluctuations of hydroacoustic signals on two paths of the Black Sea under conditions of a thermal underwater sound channel and tonal-continuous emission at frequencies of 4 and 1.5 kHz. The emitters were located in the coastal wedge on the bottom slope at depths of 35 and 60 m; a receiver system was submerged to a depth of 50–60 m off the side of a ship drifting at various distances in the open sea. Data are presented on the spatial (horizontal and vertical) and frequency intervals of fluctuation correlation on the first path extending 100 km at an emission frequency of 4 kHz under conditions of dominant fast fluctuations, as well as on the second path extending 300 km at an omission frequency of 1.5 kHz under conditions of dominant slow fluctuations. The results of experiments are used to estimate the efficiency of space-diversity and frequency-diversity reception of acoustic signals in application to information transmission over a hydroacoustic channel.

Performance comparison of different modulation formats over free-space optical (FSO) turbulence links with space diversity reception technique

The transmission performance of a free-space optical (FSO) link could be severely degraded due to atmospheric turbulence, which causes the temporal and spatial fluctuation of light intensity. Both the space diversity reception technique (SDRT) and advanced modulation formats can successfully mitigate the transmission impairments of the atmospheric turbulence. The purpose of this paper is to study and compare the bit-error-rate (BER) performance of several widely used modulation formats under different atmospheric turbulence scenarios with and without SDRT. The modulation formats studied in this paper include on-off keying (OOK), differential phase-shift keying (DPSK), and differential quadrature phase-shift keying (DQPSK). We derive a series-form formula for evaluating the BER performance of the DPSK format in the Gamma-Gamma distributed channel with SDRT. We use both theoretical analysis and simulation to examine the BER performance of OOK, DPSK, and DQPSK formats with and without SDRT. It is found that, in the strongly turbulent scenario, the OOK and DPSK formats can have as large as 19.5 and 20.3 dB of SDRT gains at the BER of 10-3, respectively. Using SDRT, the modulation gains of the DPSK format over the OOK format are 3.2 dB in the strongly turbulent scenario and 4.5 dB in the weakly turbulent scenario, respectively. In addition, in the moderately and strongly turbulent scenarios, it is found that the DPSK and DQPSK formats have almost the same BER performance under the same symbol rate.

Phase Fluctuations of Radio Waves in the Saturated-Scintillation Regime

We consider the problem of phase fluctuations of radio waves behind a strong phase screen and in an optically thick layer. It is shown that the phase-fluctuation distribution of the received radiation at an observation point located in the saturated-scintillation area behind a turbulent phase screen is almost identical to the normal distribution of phase fluctuations of the wave on the screen. Amplitude and phase fluctuations of the received radiation are uncorrelated both for single-point and space-diversity reception if, in the latter case, the distance between the observation points exceeds the spatial scale of the diffraction component of the complex field of the received signal. Expressions for the mean square and the structural function of phase fluctuations of radio waves behind a turbulent phase screen in the saturated-scintillation regime are obtained. It is shown that the structural function of phase fluctuations in the diffraction component of the scattered field, which is exactly the function that forms saturated scintillations of the received radiation, almost coincides with the structural function of phase fluctuations on the screen. It is also shown that the diffraction effects can be neglected and the geometric-optical approximation should be used when calculating statistical characteristics of phase fluctuations of a plane wave in the saturated-scintillation area in an optically thick layer with large-scale refractive-index irregularities.

MMSE techniques for space diversity receivers in OFDM-based wireless LANs

This paper studies the application of the minimum mean square error (MMSE) beamformer to orthogonal frequency division multiplexing (OFDM)-based wireless local area networks. The questions here addressed are mainly the design with finite-length data and the choice of the OFDM signal domain where the beamformer is applied, either frequency or time. As OFDM signals need more samples than other modulations to stabilize the estimation of the signal statistics, how to exploit the finite-length training sequence provided for the design of equalizers becomes an important issue. The paper also shows that the usual frequency processing in OFDM is not always the best choice for the spatial beamforming, mainly for channels with a very high delay spread. Then, time processing turns out to be the best suited approach in terms of the tradeoff between performance and complexity. Additionally, novel modifications of the MMSE spatial filter are proposed to improve the raw bit-error rate performance: 1) a temporal semiblind approach that exploits the cyclic prefix and 2) windowing in the frequency domain.

BER performance of MQAM with L‐branch MRC diversity reception over correlated Nakagami‐m fading channels

AbstractExact and closed form generalized expressions for bit error rate (BER) of M‐ary quadrature amplitude modulation (MQAM) with L‐branch maximal ratio combining (MRC) space diversity reception in fading channels are derived and analyzed. The fading channels are modeled as identical but correlated frequency‐nonselective slow Nakagami‐m fading channels corrupted by additive white Gaussian noise (AWGN). Analytical results obtained are in terms of few finite range integrals with an integrand composed of elementary functions. Because of their simple form, these analytical results readily allow numerical evaluation in cases of practical interest. The results are also general enough to include Nakagami‐m fading channels with and without correlation, no diversity system, Rayleigh fading channels with and without correlation, and AWGN as special cases. The numerical results for the case of 16QAM are shown graphically and also in tabular form in order to examine the effects of fading severity, order of diversity, and branch correlation on the BER performance. The two correlation models considered are constant correlation model and exponential correlation model. One may be interested to know how the BER of MQAM is related to symbol error rate (SER) of MQAM. Therefore, the BER results obtained in this paper are also compared with that obtained directly from the SER. It is expected that the analytical results presented in this paper will provide a convenient tool for design and analysis of a radio communication system with space diversity reception in uncorrelated and correlated fading environment. Copyright © 2002 John Wiley & Sons, Ltd.

Space diversity reception and parallel blind equalization in short-burst TDMA systems

We consider a q-antenna space diversity system combined with two parallel equalizer branches for the reception of short-burst time-division multiple-access signals. By applying a combination of several previously proposed blind equalization algorithms, we make significant improvements over the burst error probability performance reported to date. This is achieved by starting the two blind equalizers from different initial tap settings and applying a specific weighting of the equalizers' outputs in order to derive the symbol decision. A burst error probability of less than 10/sup -3/ is achieved with the new strategy for a root mean square (rms) delay spread of less than 0.4 times the symbol duration.

Carrier-frequency estimation for space-diversity reception over selective channels

Carrier-frequency estimation for space-diversity reception over frequency-selective channels is discussed. Three estimation schemes based on training sequences are proposed. The first scheme employs arbitrary sequences and provides joint maximum likelihood (ML) estimates of the carrier frequency and the channel response. Its implementation is complex, but its accuracy achieves the Cramer-Rao bound. The second scheme is based on the ML criterion but employs periodic sequences to reduce the computational load. Periodic sequences are also used in the third scheme which is based on heuristic reasoning. Theoretical analysis and simulations are employed to assess the performance of the three estimation methods, and to show the improvements due to space diversity.