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A Class of Non-Linear Signal Processing Scheme for PMEPR Reduction in MC-CDMA Systems


Affiliations
1 Department of Electronics and Communication Engineering, Pondicherry Engineering College Pondicherry University, Pondicherry-605014
2 Department of Electronics and Communication Engineering, Pondicherry University, Pondicherry, India
     

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The main feature of the next-generation wireless systems will be the convergence of multi-media services such as speech, audio, video, image, and data. This implies that a future wireless terminal, by guaranteeing high speed data, will be able to connect to   different networks in order to support various services: switched traffic, IP data packets, and broadband streaming services such as video. Multicarrier code-division multiple-access (MC-CDMA) scheme is the promising candidate for future broadband wireless systems, as it provides higher flexibility, transmission rates and spectral efficiency. It combines an orthogonal frequency division multiplexing (OFDM) modulation with a code-division multiple-access (CDMA) scheme and hence exploits the advantages of   OFDM as well as CDMA.

A well-known, major drawback of conventional orthogonal frequency-division multiplexing (OFDM) transmission schemes is their strong envelope fluctuation and high peak-to-mean envelope power ratio (PMEPR), leading to power amplification difficulties. That is the OFDM signal which is the superposition of large number of modulated subcarriers, usually exhibits a high instantaneous peak value with respect to average value leading to envelope fluctuations. This is cited as a major drawback in OFDM scheme. This drawback is found in MC-CDMA too.  As MC-CDMA signals have high envelope fluctuations and a high peak-to-mean envelope power ratio (PMEPR), which leads to amplification difficulties.

In order to avoid the out-of-band  radiation levels which are inherent to nonlinear distortion, power amplifiers for OFDM transmission are required to have linear characteristics and/or a significant input back off  has to be adopted. Therefore, reduced power efficiency is the price to pay for a high bandwidth efficiency. A class of low-complexity signal-processing schemes for reduced PMEPR, spectrally efficient MC-CDMA transmission was proposed.


Keywords

Clipping, Envelope Fluctuations, PAPR, PMEPR.
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  • A Class of Non-Linear Signal Processing Scheme for PMEPR Reduction in MC-CDMA Systems

Abstract Views: 378  |  PDF Views: 3

Authors

S. Vasanthakumar
Department of Electronics and Communication Engineering, Pondicherry Engineering College Pondicherry University, Pondicherry-605014
S. Tamilselvan
Department of Electronics and Communication Engineering, Pondicherry University, Pondicherry, India
G. Annalakshmi
Department of Electronics and Communication Engineering, Pondicherry University, Pondicherry, India

Abstract


The main feature of the next-generation wireless systems will be the convergence of multi-media services such as speech, audio, video, image, and data. This implies that a future wireless terminal, by guaranteeing high speed data, will be able to connect to   different networks in order to support various services: switched traffic, IP data packets, and broadband streaming services such as video. Multicarrier code-division multiple-access (MC-CDMA) scheme is the promising candidate for future broadband wireless systems, as it provides higher flexibility, transmission rates and spectral efficiency. It combines an orthogonal frequency division multiplexing (OFDM) modulation with a code-division multiple-access (CDMA) scheme and hence exploits the advantages of   OFDM as well as CDMA.

A well-known, major drawback of conventional orthogonal frequency-division multiplexing (OFDM) transmission schemes is their strong envelope fluctuation and high peak-to-mean envelope power ratio (PMEPR), leading to power amplification difficulties. That is the OFDM signal which is the superposition of large number of modulated subcarriers, usually exhibits a high instantaneous peak value with respect to average value leading to envelope fluctuations. This is cited as a major drawback in OFDM scheme. This drawback is found in MC-CDMA too.  As MC-CDMA signals have high envelope fluctuations and a high peak-to-mean envelope power ratio (PMEPR), which leads to amplification difficulties.

In order to avoid the out-of-band  radiation levels which are inherent to nonlinear distortion, power amplifiers for OFDM transmission are required to have linear characteristics and/or a significant input back off  has to be adopted. Therefore, reduced power efficiency is the price to pay for a high bandwidth efficiency. A class of low-complexity signal-processing schemes for reduced PMEPR, spectrally efficient MC-CDMA transmission was proposed.


Keywords


Clipping, Envelope Fluctuations, PAPR, PMEPR.