Orthogonal frequency-division multiplexing (OFDM)是一種有效的技術，以應付在寬頻無線通訊的頻率選擇性衰弱通道。Single-carrier frequency-division multiple access(SC-FDMA)它是一種可以實現類似的性能，基本架構相同於OFDM。SC-FDMA是OFDM先經由預編碼運算，此運算是經由離散傅立葉轉換(DFT)完成，使用預編碼可以降低均峰比PAPR並且可以有效的功率使用且降低製造成本。但OFDM技術性能主要取決於通道的頻率響應(CFR)估測的準確性。大多數高性能的通道估測建立在利用其頻率響應上的通道統計特性。也是有一些實現較為簡單，基於模型的方法並且對於頻率響應的相關性依賴性較少，由SC-FDMA中的參考訊號可以得到完整的通道資訊，以利於基於模組(Model-Based)運算加上修改式直接決策方法，使通道估測相較於傳統方法有較好的性能。Orthogonal frequency-division multiplexing (OFDM) is an effective technique to cope with frequency-selective fading channels in broadband wireless communications. Single-carrier frequency-division multiple access(SC-FDMA) is a technique which can achieve similar performance and essentially the same structure as OFDMA. SC-FDMA pre-codes its information-bearing symbols by discrete Fourier transform (DFT). This pre-coding operation can reduce PAPR and can benefit power efficiency and reduce manufacturing cost. The performance of OFDM technique depends mainly on the accuracy in channel frequency response (CFR) estimation. Most high performance channel estimation schemes exploit the correlation of the CFRs of subchannels which rely on the knowledge of channel statistics. There are also some Model-Based methods which are relatively simple in implementation and less dependent of the CFR correlation.In SC-FDMA we use reference signal can get the symbol complete channel information for Model-Based computy and Decision–Direct ,which have better performance compared to traditional methods.
