High peak to average power ratio (PAPR) of OFDM reduces the transmitter power efficiency and increases the complication in hardware implementation. A number of techniques have been developed to minimize PAPR of OFDM. Among these techniques, iterative clipping and filtering (ICF) is an effective recent technique that produces significant results in minimizing PAPR. But, the major limitation of this approach is that it requires several iterations for minimizing PAPR. In order to overcome the above limitation, an optimization based ICF is used in this research work. An efficient custom optimized adaptive clipping and filtering technique is proposed. The proposed method shows a greater reduction in PAPR in lesser iterations with reduced out-of-band distortion and bit error rate when compared over classical clipping techniques. Moreover, the effects of oversampling on the performance of the proposed OFDM system are also evaluated.

PAPR Reduction of OFDM Signal via Custom Conic Optimized Iterative Adaptive Clipping and Filtering

Orthogonal Frequency Division Multiplexing (OFDM) is an efficient method of data transmission f r high speed communication systems. However, the main drawback o f OFDM systems is that, it suffers from the problem of hig h Peak-to-Average Power Ratio (PAPR) which causes inefficient use of the High Power Amplifier and could limit transmission efficiency. OFDM consist of large number of independent subcarriers, as a resul t of which the amplitude of such a signal can have high peak value s. In this paper, we propose an effective reduction scheme that combi nes DCT and SLM techniques. The scheme is composed of the DCT f ollowed by the SLM using the Riemann matrix to obtain phase se quences for the SLM technique. The simulation results show PAPR can be greatly reduced by applying the proposed scheme. In compari son with OFDM, while OFDM had high values of PAPR –about 10. 4dB our proposed method achieved about 4.7dB reduction of t he PAPR with low complexities computation. This approach also av oids randomness in phase sequence selection, which makes it simpler to decode at the receiver. As an added benefit, the m atrices can be generated at the receiver end to obtain the data si gnal and hence it is not required to transmit side information (SI). Keywords—DCT transform, OFDM, PAPR, Riemann matrix, SLM.

SLM Using Riemann Sequence Combined with DCT Transform for PAPR Reduction in OFDM Communication Systems

Orthogonal Frequency Division Multiplexing (OFDM) is a very attractive technique for high-data-rate transmission in wireless and wired applications. One major disadvantage of OFDM is that the time domain OFDM signal which is a sum of several sinusoids leads to high peak to average power ratio (PAPR). Number of techniques has been proposed in the literature for reducing the PAPR in OFDM systems. In this paper two techniques proposed for reducing the PAPR are Selected Mapping (SLM) and Partial Transmit Sequence (PTS). The reduction of peak to average transmit power ratio of multicarrier modulation systems, called selected mapping, which is appropriate for a wide range of applications. Significant gains can be achieved by selected mapping where as complexity remains quite moderate. The partial transmit sequences (PTS) scheme achieves an excellent peak-to-average power ratio (PAPR) reduction performance of orthogonal frequency division multiplexing (OFDM) signals at the cost of exhaustively searching all possible rotation phase combinations, resulting in high computational complexity. The simulation results show that the performance of SML and PTS and compare between them.

Comparative study between Selection Mapping Technique (SLM) and Partial Transmission Sequence (PTS) for PAPR reduction in OFDM signals

Discrete Cosine Transform based Single carrier frequency division multiple access (DCT-SCFDMA) is a prominent technique for providing high data rates in multimedia services. It also provides high Quality of Service to the users by mitigating the fading of signals. But High peak-to-average power ratio (PAPR) is a technical challenge which reduces the efficiency of RF power amplifiers. In this article, a novel joint scheme of PAPR reduction method is proposed and analyzed based on pulse shaping and absolute exponential companding (AEXP) technique. Our method proposes the use of standard raised cosine filter and square root raised cosine filter along with the AEXP companding process separately in DCT-SCFDMA system for different subcarrier mapping techniques e.g. interleaved frequency division multiple access and localized frequency division multiple access. Through extensive simulations, the numerical analysis presents that proposed architecture achieves significant improvements over the existing standard pulse shaping methods when used alone in DCT-SCFDMA system as far as the lowest PAPR is concerned.

Efficient PAPR Reduction in DCT-SCFDMA System Based on Absolute Exponential Companding Technique with Pulse Shaping

Orthogonal Frequency Division Multiplexing (OFDM) is an efficient method of data transmission for high speed communication systems. One of the challenging issues for OFDM system is its high Peak-to-Average Power Ratio (PAPR) which causes inefficient use of the High Power Amplifier (HPA) and could limit transmission efficiency. In this paper we analyze the effects of PAPR on HPA and its reduction technique based on GCD matrix In Selected Mapping (SLM) method. Simulation results shows that the new phase sequence based SLM method has good performance in PAPR reduction. OFDM is a Multi Carrier Modulation (MCM) technique, offers a considerable high spectral efficiency, multipath delay spread tolerance, immunity to the frequency selective fading channels, power efficiency and immune to inter symbol interference (1). These days the OFDM technique is considered as a strong candidate for the Fourth Generation (4G) of mobile communication systems. However, though OFDM has many advantages, still some challenging issues remains unsolved in the design of the system. One of the major problems is high Peak-to-Average Power Ratio (PAPR) of transmitted OFDM signal. These multi carrier systems have a problem that PAPR increases with the increase of the number of sub carriers, which makes the signal peaks moves into the non linear region of the RF power amplifier which causes signal distortion (2). Therefore, the OFDM receiver's detection efficiency is very sensitive to the non linear devices used in its signal processing loop, such as Digital-to- Analog converter (DAC) and high power amplifier, which may severely impair system performance due to induced spectral regrowth and detection efficiency degradation (3). The high peaks of OFDM signal can be reduced in three ways. The fist kind is distribution technique, such as clipping, companding and so on. This kind of technique is simple and intuitionistic, but it's inevitable to cause some performance degradation. The second kind is coding technique. In particular, the use of Golay complementary sequence. In an efficient method to reduce the PAPR for a small number of subcarriers, but it has a drawback that it decreasing the transmission rate significantly for a large number of subcarriers. The third kind is probabilistic technique including selective mapping (SLM) and the partial transmit sequence (PTS)(4).In this paper, firstly, we investigate the effect of PAPR on HPA based on characteristics of the OFDM

http://www.sersc.org/journals/IJSIP/vol7_no5/15.pdf

GCD Matrix based PAPR Reduction Technique for OFDM System

One of main disadvantage of OFDM is high peak-to-average power ratio (PAPR). In this paper, two effective PAPR reduction schemes are proposed. These techniques combine DCT and SLM techniques. The scheme 1 is composed of the DCT followed by SLM technique, and the DCT is used followed by conventional SLM in proposed scheme 2. Simulation results show that the proposed schemes can obtain significant PAPR reduction performance with that of ordinary SLM techniques.

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Zhongpeng Wang

Papers

Reduction PAPR of OFDM Signals by Combining SLM with DCT Transform