A NON-LINEAR SCHEME FOR PMEPR REDUCTION IN MC-CDMA SYSTEM
Journal Title: International Journal of Computer Science & Engineering Technology - Year 2012, Vol 3, Issue 3
Abstract
The main feature of the next-generation wireless systems will be the convergence of multimedia 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 high bandwidth efficiency. A class of low-complexity signal-processing schemes for reduced PMEPR, spectrally efficient MC-CDMA transmission was proposed.
Authors and Affiliations
S. Tamilselvan
Keywords
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