A low complexity selected mapping scheme for peak to average power ratio reduction with digital predistortion in OFDM systems

One of the effective methods used for reducing peak-to-average power ratio (PAPR) in orthogonal frequency division multiplexing (OFDM) systems is selected mapping (SLM). In this paper, a new SLM scheme called DSI-SLM, which is a combination of dummy sequence insertion (DSI) and conventional selected mapping (C-SLM) is proposed. Previous techniques have had some drawbacks. In DSI, increasing the number of dummy sequences to have better PAPR degrades transmission efficiency, and in C-SLM, the complexity rises dramatically when the number of sub-blocks increases. The proposed DSI-SLM scheme significantly reduces the complexity because of the reduction in the number of sub-blocks compared with the C-SLM technique while its PAPR performance is even better. To enhance the efficiency of the OFDM system and suppress the out-of-band distortion from the power amplifier nonlinearity, a digital predistortion technique is applied to the DSI-SLM scheme. Simulations are carried out with the actual power amplifier model and the OFDM signal based on the worldwide interoperability for microwave access standard and quadrature phase-shift keying modulation. The simulation results show improvement in PAPR reduction and complexity, whereas the BER performance is slightly worse

Evaluation performance of OFDM system using the selected mapping technique for WIMAX technology

Orthogonal Frequency Division Multiplexing (OFDM) is a promising technique used in the wireless broadband communication systems these days. It is a form of multicarrier modulation technique with high spectral efficiency, robustness to channel fading, immunity to impulse interference, uniform average spectral density, capacity to handle very strong echoes and very less nonlinear distortion are the properties of the OFDM. One major disadvantage of OFDM is that the time domain OFDM signal which is the sum of several sinusoids leading to high peak to average power ratio (PAPR). This work, a technique is proposed in the literature for reducing the PAPR in OFDM systems selected mapping technique (SML) for reducing the PAPR in the simulation result shows the PAPR reduction of OFDM signals. The aim is to come up with an approach for a new modified selected mapping (SLM) technique. The modified technique has the inclusion of the idea of sub block partitioning of signals. The comparative analysis between the conventional SLM scheme and the modified SLM scheme shows that the modification gives better complementary cumulative distributive function (CCDF) of the PAPR of transmitted signal

Peak to average power ratio reduction in NC–OFDM systems

Non contiguous orthogonal frequency division multiplexing (NC-OFDM) is an efficient and adaptable multicarrier modulation scheme to be used in cognitive radio communications. However like OFDM, NC-OFDM also suffers from the main drawback of high peak to average power ratio (PAPR). In this paper PAPR has been reduced by employing three different trigonometric transforms. Discrete cosine transform (DCT), discrete sine transform (DST) and fractional fourier transform (FRFT) has been combined with conventional selected level mapping (SLM) technique to reduce the PAPR of both OFDM and NC-OFDM based systems. The method combines all the transforms with SLM in different ways. Transforms DCT, DST and FRFT have been applied before the SLM block or inside the SLM block before IFFT. Simulation results show the comparative analysis of all the transforms using SLM in case of both OFDM and NC-OFDM based systems

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