Performance Evaluation of Hybrid ACE-PTS PAPR Reduction Techniques Mohamed I. Youssef, Ibrahim F. Tarrad Electrical Engineering Department Al-Azhar University Cairo, Egypt tarradif@gmail.com Mohamed Mounir Communication and electronics Department El gazeera High Institute for Engineering and Technology Cairo, Egypt Eng_mohamedvip@yahoo.com Abstract— Orthogonal Frequency Division Multiplexing (OFDM) is an attractive technique for wireless communication over frequency-selective fading channels. OFDM suffers from high Peak-to-Average Power Ratio (PAPR), which limits OFDM usage and reduces the efficiency of High Power Amplifier (HPA) or badly degrades BER. Many PAPR reduction techniques have been proposed in the literature. PAPR reduction techniques can be classified into blind receiver and non- blind receiver techniques. Active Constellation Extension (ACE) is one of the best blind receiver techniques. While, Partial Transmit Sequence (PTS) can work as blind / non-blind technique. PTS has a great PAPR reduction gain on the expense of increasing computational complexity. In this paper we combine PTS with ACE in four possible ways to be suitable for blind receiver applications with better performance than conventional methods (i.e. PTS and ACE). Results show that ACE-PTS scheme is the best among others. Expectedly, any hybrid technique has computational complexity larger than that of its components. However, ACE- PTS can be used to achieve the same performance as that of PTS or worthy better, with less number of subblocks (i.e. with less computational complexity) especially in low order modulation techniques (e.g. 4-QAM and 16-QAM). Results show that ACE- PTS with V=8 can perform similar to or better than PTS with V=10 in 16-QAM or 4-QAM, respectively, with 74% and 40.5% reduction in required numbers of additions and multiplications, respectively. Keywords— OFDM; PAPR; PTS; ACE I. INTRODUCTION The present day phenomenon of increased thirst for more information and the explosive progress of new wireless applications have led to an increased demand for wireless systems that support very high data rates, mobility and proficiently utilize the available spectrum and system resources. Orthogonal Frequency Division Multiplexing (OFDM) is among the finest solutions to achieve that and it is attractive choice for high speed data rate communication systems. OFDM is a Multi-Carrier Modulation (MCM) technique, which offers high spectrum efficiency, multipath delay spread handling, immunity to frequency selective channels and shot noise and eliminates the need for equalizers. In addition to that, efficient hardware implementation of OFDM can be realized using Fast Fourier Transform (FFT) [1]. As a result, OFDM has been chosen for high data rate communications and has been broadly deployed in various communication standards such as Long Term Evolution (LTE), Worldwide Interoperability for Microwave Access (WiMAX), Digital Video Broadcasting (DVB), and Digital Audio Broadcasting (DAB) [2]. However, some drawbacks are still unsolved in OFDM systems. A serious drawback of OFDM is the high Peak-to-Average-Power-Ratio (PAPR) of transmitted signal. This phenomenon results from that in time domain, an OFDM signal is the superposition of several narrowband subcarriers. At certain time instances, peak amplitude of the signal is large and at the other times is small. Thus, the peak power of the signal will be larger than the average of it, i.e. high PAPR. When OFDM signal with high PAPR passes through a nonlinear device e.g. High Power Amplifier (HPA), it might cause in-band distortion and undesired Out-Of-Band (OOB) radiation. Handling infrequent large peaks causes low power efficiency or increases the expense of RF power amplifier. Consequently, how to find a solution to reduce high PAPR effectively is one of the main implementation issues in OFDM communication systems [1]. In literature, there are various PAPR reduction methods and also there are different classifications of them. In [3] methods are classified according to its downward-compatibility. When we implement downward-compatible method in the transmitter, we don't have to modify the receiver. Receivers of methods without downward-compatibility should be modified to take vital information like Side Information (SI) into account. Methods with and without downward compatibility also called blind and non-blind methods respectively [4]. ACE [5-6] is a blind technique with high PAPR reduction gain in comparison with other blind techniques, especially in low modulation orders (e.g. 4-QAM). Also, ACE has a moderate computational complexity in comparison with PTS [7-8] with large numbers of alternatives. On the other hand, PTS can work as blind/non-blind technique with high PAPR reduction gain depending on increasing computational complexity. In literature there are plenty of competitive hybrid techniques, such as hybrid SLM-PTS [1, 9], hybrid ACE-TR [10], hybrid PTS-clipping [11], and hybrid Hadamard preceding- ߤ-Law Commanding [12]. Among them, only hybrid ACE-TR [10] is the downward compatible technique. However, TR [13] is always worse than ACE regardless of modulation type as shown in [10]. So the overall performance of ACE-TR is expected to be worse than that of hybrid ACE- PTS, as PTS technique is better than ACE in high order modulation schemes (e.g. 16-QAM and 64-QAM). 978-1-5090-3267-9/16/$31.00 ©2016 IEEE 407