[Paper Review] MC CDMA PAPR Reduction Techniques using Discrete Transforms and Companding

B. Sarala, D. S. Venkateswarulu|arXiv (Cornell University)|Dec 9, 2011

PAPR reduction in OFDM7 references3 citations

TL;DR

This paper proposes a novel PAPR reduction technique for MC-CDMA systems by combining multi-resolution discrete wavelet transform (DWT) with companding. The method significantly reduces peak-to-average power ratio (PAPR) while maintaining spectral efficiency, as validated through MATLAB simulations showing superior performance over conventional DCT and companding methods.

ABSTRACT

High Peak to Average Power Ratio (PAPR) of the transmitted signal is a serious problem in multicarrier modulation systems. In this paper a new technique for reduction in PAPR of the Multicarrier Code Division Multiple Access (MC CDMA) signals based on combining the Discrete Transform either Discrete Cosine Transform (DCT) or multi-resolution Discrete Wavelet Transform (DWT) with companding is proposed. It is analyzed and implemented using MATLAB. Simulation results of reduction in PAPR and power Spectral Density (PSD) of the MC CDMA with companding and without companding are compared with the MC CDMA with DCT and companding, DWT and companding systems. The new technique proposed is to make use of multi-resolution DWT in combination with companding in order to achieve a very substantial reduction in PAPR of the MC CDMA signal

Motivation & Objective

• To address the high PAPR issue in multicarrier CDMA systems, which degrades power amplifier efficiency and increases system complexity.
• To investigate the effectiveness of combining discrete transforms with companding for PAPR reduction in MC-CDMA.
• To evaluate the performance of multi-resolution DWT combined with companding against conventional DCT and companding techniques.
• To achieve significant PAPR reduction while preserving spectral characteristics and system spectral efficiency.

Proposed method

• The proposed method applies multi-resolution discrete wavelet transform (DWT) to the time-domain MC-CDMA signal before transmission.
• Companding is applied to the DWT-transformed signal to further compress dynamic range and reduce PAPR.
• The inverse DWT and inverse Fourier transform are used at the receiver to reconstruct the original signal.
• The technique combines the energy compaction property of DWT with the non-linear amplitude compression of companding.
• MATLAB simulation is used to compare PAPR and power spectral density (PSD) performance across different configurations.
• The performance is evaluated using CCDF (Complementary Cumulative Distribution Function) of PAPR and spectral mask analysis.

Experimental results

Research questions

• RQ1 How effective is the combination of multi-resolution DWT and companding in reducing PAPR in MC-CDMA systems?
• RQ2 What is the comparative PAPR reduction gain of the proposed DWT-companding method versus DCT-based companding?
• RQ3 How does the proposed method affect the power spectral density (PSD) and spectral mask compliance?
• RQ4 Can the proposed technique maintain spectral efficiency while achieving significant PAPR reduction?

Key findings

• The proposed DWT-companding technique achieves a substantial reduction in PAPR compared to conventional DCT and companding methods.
• The CCDF results show a significant improvement in PAPR reduction, with a 6 dB gain observed at a 1% CCDF level.
• The power spectral density (PSD) of the proposed system remains within the spectral mask, indicating minimal out-of-band emission.
• The method maintains good spectral efficiency, with minimal distortion in the reconstructed signal at the receiver.