Performance Analysis of OFDM with Peak Cancellation Under EVM and ACLR Restrictions

This paper presents performance analysis of an adaptive peak cancellation method to reduce the high peak-toaverage power ratio (PAPR) for OFDM systems, while keeping the out-of-band (OoB) power leakage as well as an in-band distortion power below the pre-determined level. In this work, the increase of adjacent leakage power ratio (ACLR) and error vector magnitude (EVM) are estimated recursively using the detected peak amplitude. We present analytical framework for OFDM-based systems with theoretical bit error rate (BER) representations and detection of optimum peak threshold based on predefined EVM and ACLR requirements. Moreover, the optimum peak detection threshold is selected based on the oretical design to maintain the predefined distortion level. Thus, their degradations are automatically restricted below the pre-defined levels which correspond to target OoB radiation. We also discuss the practical design of peak-cancellation (PC) signal with target OoB radiation and in-band distortion through optimizing the windowing size of the PC signal. Numerical results show the improvements with respect to both achievable bit error rate (BER) and PAPR with the PC method in eigen-beam space division multiplexing (E-SDM) systems under restriction of OoB power radiation. It can also be seen that the theoretical BER shows good agreements with simulation results

A First-Order Primal-Dual Method for Saddle Point Optimization of PAPR Problem in MU-MIMO-OFDM Systems

This paper investigates the use of a particular splitting-based optimization technique for constrained l∞-norm based peak-to-average power ratio (PAPR) reduction problem in multiuser orthogonal frequency-division multiplexing (OFDM) based multiple-input multi-output (MIMO) systems. PAPR reduction and multi-user interference (MUI) cancelation are considered in a saddle-point formulation on the downlink of a multi-user MIMO-OFDM system and an efficient primal-dual hybrid gradient (PDHG) inspired algorithm with easy-to-evaluate proximal operators is developed. The proposed algorithm converges significantly faster to satisfactory solutions with much improved asymptotical convergence rate than existing methods. Numerical results illustrate the superior performance of the proposed algorithm over existing methods in terms of PAPR reduction for different MIMO configurations

Adjustable dynamic range for paper reduction schemes in large-scale MIMO-OFDM systems

In a multi-input-multi-output (MIMO) communication system there is a necessity to limit the power that the output antenna amplifiers can deliver. Their signal is a combination of many independent channels, so the demanded amplitude can peak to many times the average value. The orthogonal frequency division multiplexing (OFDM) system causes high peak signals to occur because many subcarrier components are added by an inverse discrete Fourier transformation process at the base station. This causes out-of-band spectral regrowth. If simple clipping of the input signal is used, there will be in-band distortions in the transmitted signals and the bit error rate will increase substantially. This work presents a novel technique that reduces the peak-to-average power ratio (PAPR). It is a combination of two main stages, a variable clipping level and an Adaptive Optimizer that takes advantage of the channel state information sent from all users in the cell. Simulation results show that the proposed method achieves a better overall system performance than that of conventional peak reduction systems in terms of the symbol error rate. As a result, the linear output of the power amplifiers can be minimized with a great saving in cost

A Review Paper on PAPR Reduction in OFDM using SLM and Adaptive Clipping

Orthogonal Frequency division Multiplexing (OFDM) is an effectual technique of data transmission for high speed communication schemes. However, the main drawback of OFDM system is the high Peak to Average Power Ratio (PAPR) of the communicated signals. OFDM contain of large number of independent subcarriers, as a result of which the amplitude of such a signal can have high peak values. Coding, phase rotation and clipping are between many PAPR reduction schemes that have been proposed to overcome this problem. Here in this paper we survey on two different PAPR reduction methods adaptive clipping and selective mapping (SLM) are used to reduce PAPR. Important reduction in PAPR has been achieved using these techniques

Constant Envelope Precoding for Large Antenna Arrays

5G, the new generation of mobile communications, is expected to provide huge improvements in spectral efficiency and energy efficiency. Specifically, it has been proven that the adoption of large antenna arrays is an efficient means to improve the system performance in both of these efficiency measures. For these reasons, the deployment of base stations with large amount of antennas has attracted a substantial amount of research interest over the recent years. However, when pure digital beamforming is pursued in large array system context, a large number of transmitter and receiver chains must also be implemented, increasing the complexity and costs of the deployment. In general, power consumption of the cellular network is recognized as a major concern. Radio transmitters tend to be really power hungry, especially because of the potential energy inefficiency of their power amplifiers. Due to the characteristics of the current and future waveforms utilized in wireless communications, power amplifiers need to work in a relatively linear regime in order not to distort the signal, making the energy efficiency of such highly linear amplifiers to be rather low. If power amplifiers were capable of working in the nonlinear regime without degrading system performance, their energy efficiency could be notably increased, resulting in considerable savings in energy, costs and system complexity. In this Thesis, the development and evaluation of a constant envelope spatial precoder is being addressed. The precoder is capable of generating a symbol-rate constant envelope signal, which despite pulse-shape filtering yields substantial robustness against the nonlinearities of power amplifiers. This facilitates pushing power amplifiers into heavily nonlinear regime, with the consequent increase in their energy efficiency. At the same time, the precoder is able to perform spatial beamforming processing in order to mitigate the multi-user interference due to spatial multiplexing. It is assumed that the number of antennas in the base station is much larger than the number of simultaneously scheduled users, implying that large-scale MU-MIMO scenarios are considered, which allows us to exploit the additional degrees of freedom to perform waveform shaping. For the sake of evaluating the proposed precoder performance, different metrics such as PAPR, BER, multi-user interference and beamforming gain are compared to those of currently used precoding techniques. The obtained results indicate that the studied constant-envelope precoder can facilitate running the PA units of the large-array system in heavily nonlinear region, without inducing substantial nonlinear distortion, while also simultaneously providing good spatial multiplexing and beamforming characteristics. These, in turn, then facilitate larger received SINRs for the scheduled users, and therefore larger system throughputs and a more efficient utilization of the power amplifiers

Optimizing multi-antenna M-MIMO DM communication systems with advanced linearization techniques for RF front-end nonlinearity compensation in a comprehensive design and performance evaluation study

The study presented in this research focuses on linearization strategies for compensating for nonlinearity in RF front ends in multi-antenna M-MIMO OFDM communication systems. The study includes the design and evaluation of techniques such as analogue pre-distortion (APD), crest factor reduction (CFR), multi-antenna clipping noise cancellation (M-CNC), and multi-clipping noise cancellation (MCNC). Nonlinearities in RF front ends can cause signal distortion, leading to reduced system performance. To address this issue, various linearization methods have been proposed. This research examines the impact of antenna correlation on power amplifier efficiency and bit error rate (BER) of transmissions using these methods. Simulation studies conducted under high signal-to-noise ratio (SNR) regimes reveal that M-CNC and MCNC approaches offer significant improvement in BER performance and PA efficiency compared to other techniques. Additionally, the study explores the influence of clipping level and antenna correlation on the effectiveness of these methods. The findings suggest that appropriate linearization strategies should be selected based on factors such as the number of antennas, SNR, and clipping level of the system

Pulse shaping approach to PAPR reduction for OFDM communication systems

One of the main drawbacks of the OFDM communication system is the high peak-to-average-power ratio (PAPR) of the transmitted signal. In this thesis: (i ) Optimal pulse shaping filter design is proposed to reduce the PAPR of the OFDM signal; (ii ) The level crossing rate theorem is used to derive an upper bound for the CCDF of PAPR of OFDM signal with pulse shaping; (iii ) The multiple filter design is proposed to reduce the PAPR of multiuser OFDM signal