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

A joint OFDM PAPR reduction and data decoding scheme with no SI estimation

The need for side information (SI) estimation poses a major challenge when selected mapping (SLM) is implemented to reduce peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems. Recent studies on pilot-assisted SI estimation procedures suggest that it is possible to determine the SI without the need for SI transmission. However, SI estimation adds to computational complexity and implementation challenges of practical SLM-OFDM receivers. To address these technical issues, this paper presents the use of a pilot-assisted cluster-based phase modulation and demodulation procedure called embedded coded modulation (ECM). The ECM technique uses a slightly modified SLM approach to reduce PAPR and to enable data recovery with no SI transmission and no SI estimation. In the presence of some non-linear amplifier distortion, it is shown that the ECM method achieves similar data decoding performance as conventional SLM-OFDM receiver that assumed a perfectly known SI and when the SI is estimated using a frequency-domain correlation approach. However, when the number of OFDM subcarriers is small and due to the clustering in ECM, the modified SLM produces a smaller PAPR reduction gain compared with conventional SLM

Energy Efficient Peak Power Reduction in OFDM with Amplitude Predistortion Aided by Orthogonal Pilots

The high Peak-to-Average Power Ratio (PAPR) is a main drawback of Orthogonal Frequency Division Multiplexing (OFDM) systems. We propose a two-step technique to reduce the PAPR consisting of a metric-based constellation extension method, such as Simple Amplitude Predistortion (SAP) algorithm, aided by Orthogonal Pilot Sequences (OPS) in a previous step, where we also provide a low-complex implementation of OPS scheme. We show that our proposal, named OP-SAP, outperforms previous approaches in terms of PAPR reduction, due to joining the benefits of Orthogonal Pilots with SAP algorithm. Moreover, it is energy efficient within two aspects: transmitted energy and implementation energy. OP-SAP saves up to 57% of transmitted energy per predistorted symbol compared to SAP. Regarding implementation energy, PAPR reduction techniques introduce some additional computational complexity, which requires extra cycles in the processor that demand energy consumption. We present an exhaustive analysis on computational power cost that shows the low power consumption of OP-SAP compared to other methods as SeLected Mapping (SLM), what yields a remarkable energy saving in its practical implementation.This work was supported in part by the Spanish National Projects GRE3N-SYST (TEC2011-29006-C03-03) and COMONSENS (CSD2008-00010), Fundación Carolina (Spain), and SENESCYT (Ecuador).Publicad