A Modified SLM Scheme for PAPR Reduction of UFMC Systems

One of the most promising 5G waveform candidates is the universal-filtered multicarrier system (UFMC). The UFMC system reduces the out-of-band (OoB) emission, bringing about higher spectral efficiency. This is assumed to reach robustness against frequency offset and low latency. Although, as aforementioned, the UFMC system offers many advantages, it lacks high peak-to-average power ratio (PAPR) as a multicarrier transmission technique. This research paper tackles two approaches; firstly, RCS, by developing a simulated conventional SLM system, with modifications to generate the same number of waveforms, while using fewer UFMC modulators. Secondly, by developing a simulated conventional SLM system, with modifications using the same number of modulators to generate more waveforms that would be generated in the conventional scheme. The two sets of results from the proposed M-SLM scheme are compared to each other, and to other PAPR reduction schemes using OFDM and UFMC. To reduce PAPR in UFMC systems, (M-SLM) scheme with low complexity is proposed. The essence of the proposed M-SLM scheme is represented in making use of the cyclically shifting process and FMC modulator’s linearity property. The proposed M-SLM scheme uses Um UFMC modulators to produce Uw alternative UFMC waveforms, where Uw = Um (2Um − 1). As a result, drawing a comparison with existing SLM based PAPR reduction schemes for UFMC systems; the proposed M-SLM scheme's computational complexity is reduced. Finally, there is a comparison between the proposed M-SLM scheme and the schemes there in the literature according to PAPR reduction ability.

BER PERFORMANCE ANALYSIS OF 4QAM/OFDM OVER DIFFERENT SCENARIOS OF LAPLACE FADING CHANNEL.

Multicarrier transmission, also known as (OFDM) Orthogonal Frequency Division multiplexing, in wireless communications, it has been proven to be an essential technique for countering multipath fading. It has been used successfully for HF radio applications and has been selected as the interface for digital audio transmission, digital terrestrial TV broadcasting, and high-speed wireless local area networks in Europe. In this paper, we suggested a new design for modeling multipath fading channels, such as the Laplace fading channel, in order to discover new simulation results and effects. Furthermore, the variance of the Laplace fading channel has been computed and the new Bit Error Rate (BER) derivation is established, and the performance of (M-QAM), M-ary Quadrature Amplitude Modulation (with M=4 over OFDM system under Laplace fading channels in Additive White Gaussian Noise (AWGN) is discussed and compared to the conventional M-QAM/OFDM system Rayleigh fading channel in AWGN. All the simulation results are examined using the optimum signal detection based on the Euclidean distance and evaluated using Monte-Carlo simulation.

A Non-WSSUS Channel Simulator for V2X Communication Systems

This paper presents a simulator of non-wide sense stationary uncorrelated scattering (non-WSSUS) multipath fading channels for the performance analysis of vehicle-to-everything (V2X) communication systems. The proposed simulator is constructed with the combination of the Monte Carlo and sum-of-cisoids (SOC) principles, and it is suitable for multicarrier transmission schemes such as those defined for dedicated short-range communications (DSRC) and cellular-based V2X (C-V2X) communications. The channel simulator provides an accurate and flexible solution to reproduce the time and frequency (TF) correlation properties of non-WSSUS vehicular channels under arbitrary isotropic and non-isotropic scattering conditions. Furthermore, the proposed simulator allows velocity variations and non-linear trajectories of the mobile stations (MSs). To demonstrate the practical value of the presented simulator, we evaluate the bit error rate (BER) performance of two channel estimation techniques that are considered for IEEE 802.11p transceivers, namely the least squares (LS) estimator and the spectral temporal averaging (STA) technique. The BER performance of both channel estimators was analyzed by considering three propagating scenarios for road safety applications. Our results show that the non-stationary characteristics of the vehicular multipath fading channel have nearly no effects on the LS estimator’s BER performance. In contrast, the performance of the STA estimator is significantly affected by the channel’s non-stationary characteristics. A variation of the original STA technique that applies only a temporal averaging is introduced in this work to improve the system’s BER in non-WSSUS channels.

Compensation of Non-linear Distortion Effects in MIMO-OFDM Systems Using Constant Envelope OFDM for 5G Applications

Orthogonal frequency division multiplexing (OFDM) is a multicarrier transmission system that can achieve high data rate over wireless channels. At the same time, multiple input multiple output OFDM (MIMO-OFDM) in wireless communication systems has been exposed to offer significant improvement over wireless technology by providing transmit diversity. It has become a promising technique for high-performance 5G broadband wireless communications. However, the main problem associated with MIMO-OFDM is that its signal exhibits high peak-to-average power ratio (PAPR), which causes nonlinear distortion and consequently performance degradation. Besides, PAPR carries weaknesses such as an increase in power consumption of high power amplifier (HPA) and analog to digital converter (ADC). Thus, 5G base stations will push up power requirements because energy consumption grows with the number of transceiver elements. So, mobile operators must find the right compromise that, on the one hand, guarantees a certain level of performance to a data flow, and, on the other hand, the energy cost generated for the deployment of the network. For this, as part of the management of power consumption, we propose MIMO constant envelope OFDM (MIMO-CE-OFDM) technique. In this work, we used MIMO-CE-OFDM to mitigate the nonlinear effect of HPA and ADC. To perform practical simulations, we have used COST 2100 MIMO channel model. In this paper, a MIMO-CE-OFDM system has been presented and analyzed under COST 2100 channel model conditions. Simulation results are given to illustrate the performance of [Formula: see text] MIMO-CE-OFDM in the presence of both HPA and ADC nonlinearity. This work shows that the effect of nonlinearity is shown to be negligible on MIMO-CE-OFDM signal.

Performance Prediction of OFDM-Based Cognitive Radio for Next-Generation Networking Capabilities

As a pioneering technology, next generation of mobile networks would overcome many problems of daily life activities. This new technology has many challenges that are tried to be destroyed. In this regard, to optimize the utilization of the allowed spectrum, an essential tool such as cognitive radio (CR) must be employed. It provides opportunity to use spectrum in strategic manner to both licensed and unlicensed users in such a way that the available spectrum is exploited in an efficient strategy. Meanwhile, the orthogonal frequency division multiplexing (OFDM) multicarrier transmission mechanism represents one of the more familiar techniques that are widely applied in free space systems of communication. Since this algorithm has the capability of satisfying the prime aspect of CR, which is associated with locally exploiting the unused spectrum autonomously, OFDM procedure is investigated as a CR system’s candidate. In other words, it is of interest to study its behavior when it is combined with CR technology. Here, our goal is to treat the problem of spectrum sensing techniques in conjunction with OFDM signal. Simulation results show that OFDM spectral correlation can be enhanced via varying the number of samples. Also, OFDM pilot is mandatory and acts as a flag for OFDM frames. So, it is of importance to boost it for better detection. Additionally, the probability of detection (Pd ) is estimated for different values of signal strength when the false alarm probability (Pf ) is fixed. Moreover, receiver operating characteristic, which is the variation of Pd as a function of Pf for a fixed SNR, is drawn for two cases; theoretical and simulated. It is found that the two cases are of high degree of coincidence.