OFDMA Downlink and SC FDMA Uplink Integration with Adaptive Modulation for Broadband Wireless Communication

Abstract

The wireless mobile broadband communications suffer from multipath frequency newlineselective fading and the bandwidth is the most precious commodity in all newlinecommunication systems such as 2G, 3G and 4G. Each service provider now newlinesearching, that how can one accommodate a large numbers of users with in a limited newlineallocated bandwidth, In order to increase the data rate of wireless medium with newlinehigher performance, orthogonal frequency division multiplexing (OFDM) is chosen. newlineOrthogonal frequency division multiplexing (OFDM) is an efficient method of data newlinetransmission for high speed communication systems over multipath fading channels. newlineOFDM is a bandwidth efficient multicarrier modulation where the available newlinespectrum is divided into subcarriers, with each subcarrier containing a low rate data newlinestream. OFDM has gained a tremendous interest in recent years because of its newlinerobustness in the presence of severe multipath channel conditions with simple newlineequalization, robustness against inter-symbol interference (ISI), multipath fading, in newlineaddition to its high spectral efficiency. However, the peak-to-average power ratio newline(PAPR) is a major drawback of multicarrier transmission system such as OFDM and newlineother is high sensitivity of frequency offset.The 3rd generation partnership project (3GPP) long term evolution (LTE) standard newlineuses single carrier frequency division multiple access (SCFDMA), scheme for the newlineuplink transmissions and orthogonal frequency division multiplexing access newline(OFDMA) in downlink. SCFDMA makes use of single carrier modulation and newlinefrequency domain equalization; it is a technique that has similar performance and newlineessentially the same overall complexity as those of OFDM. An outstanding newlineadvantage of SC-FDMA is its lower PAPR due to its single carrier structure. SCFDMA newlineas an attractive alternative to OFDMA, mainly in the uplink communications newlinethe lower PAPR is greatly benefit for mobile terminal in terms of power efficiency newlineand manufacturing cost. newline