Predistortion performance considering Peak to Average Power ratio reduction in OFDM context

International audienceSome recent communication systems like DVB-T2 standard set up a PAPR reduction technique followed by a linearization's one. So in such a scenario, the performance of the linearization is influenced undoubtedly by the PAPR reduction method. In this paper, we revisit the EVM metric and evaluate a closed form regarding the performance of both the PAPR reduction technique and the linearization's one. We choose the predistortion as a linearization technique and define a predistortion error. Assuming that the baseband OFDM signal is characterized as a complex Gaussian process, we consider the three top categories of PAPR reduction methods presented in [2] and we first study the distribution of the resulted signal. Then, we derive some theoretical expressions of the first and second order moments of the predistortion error and show that the error depends mainly on the PAPR of the signal after PAPR reduction method and on the predistortion quality. Some simulations compared to our proposed model confirm our results

Theoretical analysis of the trade-off between efficiency and linearity of the High Power Amplifier in OFDM context

International audiencePower efficiency and linearity are key parameters of amplification systems but they cannot be achieved simultaneously. A perfect linearity is observed when the power efficiency is low and vice versa. In this paper, we first analyze through some theoretical expressions, the power efficiency and the linearity measured by the Error Vector Magnitude (EVM) metric. Then we propose an analytical trade-off that ensures a good linearity with reasonable efficiency by combining Peak-to-Average Power Ratio (PAPR) reduction and linearization. This analysis is carried out based on Solid State Power Amplifiers (SSPA) and Predistortion (PD) as linearization technique. We show that a trade-off can be achieved for a high distortionless PAPR reduction gain followed by an effective predistortion. Last but not least the most important is to avoid the amplifier saturation by setting the PAPR of the signal after PAPR reduction technique identical to the input back-off (IBO)

Enhanced Multicarrier Techniques for Professional Ad-Hoc and Cell-Based Communications (EMPhAtiC) Document Number D3.3 Reduction of PAPR and non linearities effects

Livrable d'un projet Européen EMPHATICLike other multicarrier modulation techniques, FBMC suffers from high peak-to-average power ratio (PAPR), impacting its performance in the presence of a nonlinear high power amplifier (HPA) in two ways. The first impact is an in-band distortion affecting the error rate performance of the link. The second impact is an out-of-band effect appearing as power spectral density (PSD) regrowth, making the coexistence between FBMC based broad-band Professional Mobile Radio (PMR) systems with existing narrowband systems difficult to achieve. This report addresses first the theoretical analysis of in-band HPA distortions in terms of Bit Error Rate. Also, the out-of band impact of HPA nonlinearities is studied in terms of PSD regrowth prediction. Furthermore, the problem of PAPR reduction is addressed along with some HPA linearization techniques and nonlinearity compensation approaches

Companding and Predistortion Techniques for Improved Efficiency and Performance in SWIPT

In this work, we analyze how the use of companding techniques, together with digital predistortion (DPD), can be leveraged to improve system efficiency and performance in simultaneous wireless information and power transfer (SWIPT) systems based on power splitting. By taking advantage of the benefits of each of these well-known techniques to mitigate non-linear effects due to power amplifier (PA) and energy harvesting (EH) operation, we illustrate how DPD and companding can be effectively combined to improve the EH efficiency while keeping unalterable the information transfer performance. We establish design criteria that allow the PA to operate in a higher efficiency region so that the reduction in peak-to-average power ratio over the transmitted signal is translated into an increase in the average radiated power and EH efficiency. The performance of DPD and companding techniques is evaluated in a number of scenarios, showing that a combination of both techniques allows to significantly increase the power transfer efficiency in SWIPT systems.Comment: This work has been submitted to the IEEE for possible publication. Copyright may be transferred without notice, after which this version may no longer be accessibl

A Joint Linearization/Companding Approach for Improving a CO-OFDM Transmitter

International audience—The joint use of peak-to-average power ratio (PAPR) reduction and linearization via digital predistortion is investigated in this letter, with the view to improve the performances of coherent optical OFDM (CO-OFDM) systems employing a semiconductor optical amplifier (SOA). PAPR reduction is performed via Wang's nonlinear companding transform (WNCT), which has been recently pointed out as a pertinent choice for optical communications, and a Filter Lookup Table (FLUT) scheme is considered for linearizing the transmitter. Experimental results prove the effectiveness of the proposed scheme, as a lower EVM is achieved with respect to system implementations using only PAPR reduction or linearization

Performance improvement of a SOA-based coherent optical-OFDM transmission system via nonlinear companding transforms

International audienceCoherent-Optical OFDM systems are known to be sensitive to large peak-to-average power ratio (PAPR) at the transmitter output, due to nonlinear properties of some components involved in the transmission link. In this paper, we investigate the impact of an amplification of such signals via a semiconductor optical amplifier (SOA), considering some recent experimental results. An efficient tradeoff between BER performance, computational complexity and power efficiency is performed by a proper design of Wang's nonlinear companding function, considered for the first time in an optical communication context. A BER advantage of around 3 dB can hence be obtained over a standard system implementation not using PAPR reduction. The designed function also proves to be more efficient than µ-law function, considered in the literature as an efficient companding scheme

Performance of OPS-SAP technique for PAPR reduction in IEEE 802.11p scenarios

Vehicular Ad Hoc Networks (VANETs) are wireless networks that emerged thanks to the rapid evolution of wireless technologies and the automotive industry. The IEEE 802.11p standard is part of a group of standards related to all layers of protocols for Wireless Access in Vehicular Environment (WAVE) communications, which defines Medium Access Control (MAC) and Physical (PHY) levels. The PHY layer of IEEE 802.11p is essentially based on Orthogonal Frequency Division Multiplexing (OFDM) due to its advantages. However, OFDM signal suffers from high Peak-to-Average Power Ratio (PAPR) at the transmitter side, which causes a significant power efficiency penalty. An efficient peak power reduction technique is Simple Amplitude Predistortion aided by Orthogonal Pilot Sequences (OPS-SAP), which consists in moving certain outer constellation points of the frequency-domain OFDM symbol. In this paper, we propose the application of this OPS-SAP scheme in the IEEE 802.11p scenario, and, moreover, its evaluation under a complete PHY layer.This work has been supported by the Spanish National Projects GRE3N-SYST (TEC2011-29006-C03-03) and ELISA (TEC2014-59255-C3-3-R) and also by Escuela Politécnica a Nacional (Ecuador) by PII-DETRI-01-2016 Project

The effects of digital predistortion in a CO-OFDM system – a stochastic approach

Digital predistortion is topic of significant interest in telecommunications – both in the wireless radio field and, more recently, in photonics. In the present letter, the authors undertake a sensitivity analysis of various digital predistortion algorithms. Using recent metamodeling techniques designed for efficient stochastic analysis, the authors show that using predistortion not only leads to a reduction of the error vector magnitude in general but can also make the system less sensitive to uncertainties

Advanced signal processing techniques for the modeling and linearization of wireless communication systems.

Los nuevos estándares de comunicaciones digitales inalámbricas están impulsando el diseño de amplificadores de potencia con unas condiciones límites en términos de linealidad y eficiencia. Si bien estos nuevos sistemas exigen que los dispositivos activos trabajen cerca de la zona de saturación en busca de la eficiencia energética, la no linealidad inherente puede producir que el sistema muestre prestaciones inadecuadas en emisiones fuera de banda y distorsión en banda. La necesidad de técnicas digitales de compensación y la evolución en el diseño de nuevas arquitecturas de procesamiento de señales digitales posicionan a la predistorsión digital (DPD) como un enfoque práctico. Los predistorsionadores digitales se suelen basar en modelos de comportamiento como el memory polynomial (MP), el generalized memory polynomial (GMP) y el dynamic deviation reduction-based (DDR), etc. Los modelos de Volterra sufren la llamada "maldición de la dimensionalidad", ya que su complejidad tiende a crecer de forma exponencial a medida que el orden y la profundidad de memoria crecen. Esta tesis se centra principalmente en contribuir a la rama de conocimiento que enmarca el modelado y linealización de sistemas de comunicación inalámbrica. Los principales temas tratados son el modelo Volterra-Parafac y el modelo general de Volterra para sistemas complejos, los cuales tratan la estructura del DPD y las series de Volterra estructuradas con compressed-sensing y un método para la linealización en un rango de potencias de operación, que se centran en cómo los coeficientes de los modelos deben ser obtenidos.Premio Extraordinario de Doctorado U