MIMO solution for performance improvements of OFDM–CDMA system with pilot tone

In this paper, MIMO OFDM–CDMA downlink scheme is proposed as a solution for improving performance of the OFDM–CDMA downlink system with pilot tone and threshold detection combining (optimum TDC). The new presented system with MIMO included uses space–time block coding applied to two, three and four transmit antennas and it has an arbitrary number of receive antennas. Bit error rate performance in the case of Ricean frequency selective fading is evaluated for the original system as well as for the one with MIMO included. For that reason an adequate simulation model is developed. The results show that the proposed system significantly outperforms the OFDM–CDMA downlink system with pilot tone and optimum TDC.     

Time–space MIMO system with faster-than-nyquist signaling in frequency-selective fading channel

Multidimensional Systems and Signal Processing - The time–space receive transformation (TSRT) is proposed to increased the achievable rate of the time–space...     

Performance analysis of mode division multiplexing based free space optics system incorporating on–off keying and polarization shift keying under dynamic environmental conditions

In this paper, we propose a novel mode division multiplexing (MDM) based FSO transmission system incorporating polarization shift keying (PolSK) to enhance the information carrying capacity of the system. Using numerical simulations, we report the transmission of two independent 40 Gbps information signals using distinct Laguerre Gaussian modes up to an FSO transmission reach of 90 km under the influence of clear environmental conditions using the proposed system. Further, the influence of different environmental conditions such as rain, haze, and fog on the performance of the proposed link using bit error rate as performance metrics has also been investigated in this paper. Also, we report a comparative analysis of PolSK and on–off keying modulation formats in the proposed MDM-FSO link under the same environmental conditions. The simulation results show that under different weather conditions, PolSK based MDM-FSO transmission system demonstrates better performance.

     

Performance Evaluation of SFBC MIMO–OFDM Using FrFT Under TWDP Fading Channel

Wireless Personal Communications - Multiple-input–multiple-output orthogonal frequency division multiplexing (MIMO–OFDM) is a promising 4G technology to increase data rate and capacity...     

Performances of chaos-coded modulation concatenated with Alamouti’s space–time block code

Recently, some works have shown that it was possible to obtain quite good bit error rate performances over an additive white Gaussian noise channels with chaotic systems. In this research field, this paper proposes new insights for the chaos-coded modulation (CCM) schemes originally proposed by Kozic et al. (2003; IEEE Trans Circuits Syst Regul Pap 53:2048–2059, 2006). A detailed study of the distance spectrum of such schemes is proposed and an approximation of its distribution by means of Gaussian or Rayleigh mixtures is given. Furthermore, using these approximate distributions, a complete study of the performances of these CCM schemes when they are concatenated with a space–time block code is proposed. Accurate bounds are obtained even in the case of time-selective channels.     

Performance analysis of weather-dependent satellite–terrestrial network with rate adaptation hybrid free-space optical and radio frequency link

Due to the rapid development of satellite laser communication technology, free-space optical (FSO) links present a promising alternative to traditional radio frequency (RF) links. In this paper, taking the influence of weather factors into consideration, we investigate the performance of the hybrid FSO/RF links where the feeder link operates in the FSO band and the user link operates in the hybrid FSO/RF band. Specifically, the FSO feeder link is modeled by the gamma–gamma distribution in the presence of beam wander and pointing error, and the detection method adopts either the intensity modulation with direct intensity (IM/DD) or heterodyne detection. The RF user link is assumed to follow the shadowed Rician model. In addition, in order to improve the transmission rate of the link under the time-varying satellite–terrestrial channel, a rate adaptation scheme is proposed. The performance of the system under study is evaluated in terms of the outage probability, average bit error rate (BER), and average transmission rate. Our results provide some important insights, for example, (1) due to the constraints of the feeder link and weather factors, there is an upper limit on the outage performance and bit error rate of the hybrid link; (2) the adaptive transmission strategy can significantly improve the transmission rate of the link compared with traditional design.     

Development of MIMO–OFDM system and forward error correction techniques since 2000s

The multi-input multi-output–orthogonal frequency division multiplexing (MIMO–OFDM) system serves as one of the most promising techniques that support high data rate and high performance in diverse fading channel conditions. The paper presents an overview of MIMO–OFDM wireless technology, covering advances in physical-layer design, various space–time codes, space–frequency codes and efficient concatenated forward error correction techniques, along with interleaving to yield reduced bit error rate performance (BER). Further, the paper presents the evolution of various performance metrics that are reported since the 2000s in the literature. The evolution outcome is examined using a quadratic nonlinear fitting function to assess the interesting performance metrics. Since BER versus SNR analysis is found as the interesting performance study of the MIMO–OFDM system, the current status of the achieved BER under varying SNR is reviewed and presented.     

Fast blind channel estimation for space–time block coded MIMO–OFDM systems

Fast blind subspace channel estimation using circular property of the channel matrix is investigated for space–time block coded (STBC) multiple-input multiple-output orthogonal frequency division multiplexing (MIMO–OFDM) systems in this paper. The noise subspace computed from the correlation matrix of received signals requires a large number of symbols to converge in the subspace channel estimation. Using the circular property of the channel matrix, we propose both the cyclic repetition method (CRM) and the forward–backward method (FBM) to generate N times of equivalent signals for each STBC–OFDM symbol, respectively, where N is the size of FFT operation. With these equivalent symbols, the proposed CRM, FBM and CRM–FBM (CFBM) channel estimations can perform very well within a few OFDM symbols. The CRM, FBM and CFBM schemes are applicable to the CP-OFDM, ZP-OFDM and VC-OFDM systems, respectively. The identifiability of the subspace channel estimation is investigated that the channel matrix is determined up to two ambiguity matrices. Computer simulations demonstrate that the CRM-based, FBM-based and CFBM-based channel estimations have better performances than the conventional ones.     

Low complexity joint estimation of synchronization impairments in sparse channel for MIMO–OFDM system

Low complexity joint estimation of synchronization impairments and channel in a single-user MIMO–OFDM system is presented in this paper. Based on a system model that takes into account the effects of synchronization impairments such as carrier frequency offset, sampling frequency offset, and symbol timing error, and channel, a Maximum Likelihood (ML) algorithm for the joint estimation is proposed. To reduce the complexity of ML grid search, the number of received signal samples used for estimation need to be reduced. The conventional channel estimation techniques using Least-Squares (LS) or Maximum a posteriori (MAP) methods fail for the reduced sample under-determined system, which results in poor performance of the joint estimator. The proposed ML algorithm uses Compressed Sensing (CS) based channel estimation method in a sparse fading scenario, where the received samples used for estimation are less than that required for an LS or MAP based estimation. The performance of the estimation method is studied through numerical simulations, and it is observed that CS based joint estimator performs better than LS and MAP based joint estimator.     

An efficient combinational approach for PAPR reduction in MIMO–OFDM system

The multiple input multiple output (MIMO) with orthogonal frequency division multiplexing (OFDM) has emerged as a promising solution to enhance the channel capacity and diversity of wireless communication system without any increase in bandwidth. In this paper, a parallel combinational scheme is proposed to reduce peak-to-average power ratio (PAPR) in MIMO–OFDM system under Rayleigh fading environment. The proposed method intelligently incorporates both active gradient project and partial transmit sequence schemes. The results show that the proposed method not only reduces the PAPR and computational complexity of the system but also maintains the bit error rate compared to other schemes.     

Performance Analysis of OFDM with Frequency Offset and Correction Model

1　IntroductionIntheOrthogonalFrequencyDivisionMulti plexing (OFDM ) ,datasymbolsaretransmittedinparallel,andthewholetransmissionbandwidthisdividedintomanynarrowsubchannels.Moreover,OFDMcanalmosteliminateInterSymbolInterfer ence (ISI)forhighratedatatransmissionovertimedispersivechannelsifasuitableguardintervalischo sen[1 ] .Comparedtothetraditionalsinglecarriertransmission,thestructureofOFDMissimple,bandwidthefficiencyofOFDMishigher,andOFDMisrobusttotimedispersionfadingandim pulsen…     

Magnetically shielded electron–optical system of a continuous gyrotron with an operating frequency of 24 GHz

It is shown that it is possible to use warm solenoids with copper winding screened with ferromagnetic shields in order to reduce the solenoid supply power by a factor of 1.8–2 while retaining the strength of the magnetic field in the working space for continuous gyrotrons operating in a frequency range of 24–30 GHz. The configuration of the shields as well as the shape and location of the correcting solenoids providing an extended (up to 10 wavelengths long) section of a uniform field in the region of the gyrotron cavity have been determined. It has been shown that introduction of an additional cathode coil into the magnetic system reduces the degree of nonadiabaticity of the magnetic field approximately by an order of magnitude and thereby makes it possible to use the magnetron injection gun for formation of a helical electron beam. Optimization of the configuration of the gun electrodes based on the trajectory analysis makes it possible to obtain an electron beam whose parameters are as good as parameters of the electron beams formed in classical adiabatic electron–optical systems of gyrotrons.     

Physical layer security for space–time-block-coded MIMO system in Rician fading in the presence of imperfect feedback

Wireless Networks - We investigate physical layer security (PLY) of space–time-block-coded (STBC)–multi-input–multi-output (MIMO) wiretap channel in the presence of imperfect...     

SER and throughput analysis of space–time analog network coded relaying system over shadowed Rician fading channels

Wireless Networks - This research article presents an innovative approach based on analog network coding (ANC) in conjunction with space time block coding (STBC) which is termed as space time...     

MIMO-enabled integrated MGDM–WDM distributed antenna system architecture based on plastic optical fibers for millimeter-wave communication

Design of a low-cost fiber–wireless communication architecture is desirable by network operators. Therefore, we demonstrate the transmission of \(2 \times 2\) MIMO spatial streams, each having 2 Gbps DPSK signal to two different radio access units (RAUs) in a distributed antenna system architecture. The proposed architecture employs mode group division multiplexing in combination with wavelength division multiplexing to transport RF DPSK signals centered at 10 GHz. The RF signals are used to modulate optical carriers that are centered at 1300 nm and transmitted toward the RAUs over perfluorinated graded-index plastic optical fiber. Heterodyne detection is performed at the RAUs to transmit mm-wave signals at 60 GHz to the end users. Furthermore, wireline access is also achieved at each RAU to support simplex services. A cost-efficient multiple wavelength source is generated from a single laser by employing a dual-drive Mach–Zehnder modulator. An increase in multiplexing gain is achieved using the two LP modes, LP01 and LP11, of each generated wavelength. The proposed architecture gives acceptable BER results for practical implementation.     

Performance analysis of compensation techniques for 80 × 12-Gbps DWDM systems using optical amplifiers

Photonic Network Communications - Power compensation is the main challenging issue for dense optical communication system because it affects the signal strength, and subsequently, performances of...     

Secrecy performance analysis of CIOD–OFDM systems over wireless fading channels

Wireless Networks - Space–time block codes from coordinate interleaved orthogonal designs (CIODs) have been attracted attention due to their capability for full-diversity and full-rate...     

Performance analysis of κ-μ/gamma shadowed fading model over indoor off body communication channel

The κ-µ/gamma distribution has an importance role to model the small scale fading and shadowing over human off body indoor communication channel. This composite fading model has various special cases like κ-µ, Rician, Nakagami-m, Rayleigh, Rayleigh/gamma, Nakagami/gamma and Rice/logormal. In this paper, the expression for bit error rate (BER) using various modulation schemes, average channel capacity (ACC) and outage probability (OP) over κ-µ/gamma shadowed fading channel are derived. All the derived expressions are novel and presented in analytical form. The expression for BER and channel capacity are in form of well-known Meijer G function, whereas the outage probability expression is obtained from cumulative distribution function (CDF) proposed in previous literature. The derived expressions of BER (BPSK), average channel capacity and outage probability reduces to special cases for validation purpose. The study shows that binary phase shift keying (BPSK) modulation technique has better BER performance as compare to other modulation techniques. Moreover, on increasing α and β while κ and µ kept constant and vice versa, the ACC get increases but below the Additive white Gaussian Noise (AWGN) channel capacity as expected. Also, better outage probability performance is obtained at lowest threshold signal to noise ratio (5 dB).     

Performance analysis of a rate adaptive multi-band ultra-wideband system based on quadrature fractal modulation scheme

1 Introduction Wornell and Oppenheim[1,2] first proposed a modulation technique as an interesting potential application of dy-homogeneous signals. Due to the fractal properties of the homogeneous signals, this technique is called fractal modulation afterwards. This class of homogeneous signals remains invariant under scaling of the time axis. Dy-homogeneous signals satisfy the dyadic self-similarity property[3] s (t ) = 2 kH s (2 kt) (1) For all integers k and a constant H, termed the degree…