Singlecarrier FDMA
Singlecarrier FDMA (SCFDMA) is a frequencydivision multiple access scheme. It is also called linearly precoded OFDMA (LPOFDMA). Like other multiple access schemes (TDMA, FDMA, CDMA, OFDMA), it deals with the assignment of multiple users to a shared communication resource. SCFDMA can be interpreted as a linearly precoded OFDMA scheme, in the sense that it has an additional DFT processing step preceding the conventional OFDMA processing.
Passband modulation 

Analog modulation 
Digital modulation 
Hierarchical modulation 
Spread spectrum 
See also 

SCFDMA has drawn great attention as an attractive alternative to OFDMA, especially in the uplink communications where lower peaktoaverage power ratio (PAPR) greatly benefits the mobile terminal in terms of transmit power efficiency and reduced cost of the power amplifier. It has been adopted as the uplink multiple access scheme in 3GPP Long Term Evolution (LTE), or Evolved UTRA (EUTRA).[1][2][3]
The performance of SCFDMA in relation to OFDMA has been the subject of various studies.[4][5][6] Although the performance gap is small, SCFDMA's advantage of low PAPR makes it desirable for uplink wireless transmission in mobile communication systems, where transmitter power efficiency is of paramount importance.
Transmitter and Receiver Structure of LPOFDMA/SCFDMA
The transmission processing of SCFDMA is very similar to that of OFDMA. For each user, the sequence of bits transmitted is mapped to a complex constellation of symbols (BPSK, QPSK or MQuadrature amplitude modulation). Then different transmitters (users) are assigned different Fourier coefficients. This assignment is carried out in the mapping and demapping blocks. The receiver side includes one demapping block, one IDFT block, and one detection block for each user signal to be received. Just like in OFDM, guard intervals (called cyclic prefixes) with cyclic repetition are introduced between blocks of symbols in view to efficiently eliminate intersymbol interference from time spreading (caused by multipath propagation) among the blocks.
In SCFDMA, multiple access among users is made possible by assigning different users different sets of nonoverlapping Fourier coefficients (subcarriers). This is achieved at the transmitter by inserting (prior to IDFT) silent Fourier coefficients (at positions assigned to other users), and removing them on the receiver side after the DFT.
The distinguishing feature of SCFDMA is that it leads to a singlecarrier transmit signal, in contrast to OFDMA which is a multicarrier transmission scheme. Subcarrier mapping can be classified into two types: localized mapping and distributed mapping. In localized mapping, the DFT outputs are mapped to a subset of consecutive subcarriers, thereby confining them to only a fraction of the system bandwidth. In distributed mapping, the DFT outputs of the input data are assigned to subcarriers over the entire bandwidth noncontinuously, resulting in zero amplitude for the remaining subcarriers. A special case of distributed SCFDMA is called interleaved SCFDMA (IFDMA), where the occupied subcarriers are equally spaced over the entire bandwidth.[7]
Owing to its inherent single carrier structure, a prominent advantage of SCFDMA over OFDM and OFDMA is that its transmit signal has a lower peaktoaverage power ratio (PAPR), resulting in relaxed design parameters in the transmit path of a subscriber unit. Intuitively, the reason lies in the fact that where OFDM transmit symbols directly modulate multiple subcarriers, SCFDMA transmit symbols are first processed by an Npoint DFT block.[8]
In OFDM, as well as SCFDMA, equalization is achieved on the receiver side, after the DFT calculation, by multiplying each Fourier coefficient by a complex number. Thus, frequencyselective fading and phase distortion can be easily counteracted. The advantage is that frequency domain equalization using FFTs requires less computation than conventional timedomain equalization, which require multitap FIR or IIRfilters. Less computations result in less compounded roundoff error, which can be viewed as numerical noise.
A related concept is the combination of a single carrier transmission with the singlecarrier frequencydomainequalization (SCFDE) scheme. [9] The single carrier transmission, unlike SCFDMA and OFDM, employs no IDFT or DFT at the transmitter, but introduces the cyclic prefix to transform the linear channel convolution into a circular one. After removing the cyclic prefix at the receiver, a DFT is applied to arrive in the frequency domain, where a simple singlecarrier frequencydomainequalization (SCFDE) scheme can be employed, followed by the IDFT operation.
 DFT: Discrete Fourier Transform
 IDFT: Inverse Discrete Fourier Transform
 CP: Cyclic Prefix
 PS: Pulse Shaping
 DAC: Digital to analog Conversion
 RF: Radio Frequency signal
 ADC: Analog to Digital Conversion
 LPOFDMA: Linearly precoded OFDMA
Useful properties
 Low PAPR (Crest Factor)
 Low sensitivity to carrier frequency offset
 Less sensitive to nonlinear distortion and hence, it allows the use of lowcost power amplifiers
 Greater robustness against spectral nulls
References
 Hyung G. Myung, Junsung Lim, and David J. Goodman, “Single Carrier FDMA for Uplink Wireless Transmission”, IEEE Vehicular Technology Magazine, vol. 1, no. 3, Sep. 2006, pp. 30–38
 H. Ekström, A. Furuskär, J. Karlsson, M. Meyer, S. Parkvall, J. Torsner, and M. Wahlqvist, “Technical Solutions for the 3G LongTerm Evolution,” IEEE Commun. Mag., vol. 44, no. 3, March 2006, pp. 38–45
 3rd Generation Partnership Project (3GPP); Technical Specification Group Radio Access Network; Physical Layer Aspects for Evolved UTRA, http://www.3gpp.org/ftp/Specs/htmlinfo/25814.htm
 M. Danish Nisar, Hans Nottensteiner, and Thomas Hindelang, “On Performance Limits of DFTSpread OFDM Systems”, in Sixteenth IST Mobile Summit, July 2007 in Budapest, Hungary.
 B.E. Priyanto, H. Codina, S. Rene, T.B. Sorensen, P. Mogensen, “Initial Performance Evaluation of DFTSpread OFDM Based SCFDMA for UTRA LTE Uplink”, IEEE Vehicular Technology Conference (VTC) 2007 Spring, Dublin, Ireland, Apr. 2007
 N. Benvenuto and S. Tomasin, “On the comparison between OFDM and single carrier modulation with a DFE using a frequency domain feedforward filter,” IEEE Trans. on Commun., vol. 50, no. 6, June 2002 pp. 947–955
 Xixia Leader in Converged IP Testing, "Single Carrier FDMA in LTE", 915272501 Rev A November 2009.
 H. G. Myung, J. Lim, and D. J. Goodman, "PeaktoAverage Power Ratio of Single Carrier FDMA Signals with Pulse Shaping", The 17th Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC ’06), Helsinki, Finland, Sep. 2006
 D. Falconer, S. L. Ariyavisitakul, A. BenyaminSeeyar, and B. Eidson, “Frequency Domain Equalization for SingleCarrier Broadband Wireless Systems,” IEEE Commun. Mag., vol. 40, no. 4, April 2002, pp. 58–66