Construction of spectrally efficient low-crest waveforms for multicarrier CDMA systems
T.F. Ho, Victor K. Wei · 2002
We study the spectral efficiency and the crest factor of the transmitted signals in multicarrier code division multiple access (MC-CDMA) systems. In this paper, we find a set of spectrally efficient complementary (SEC) sequences {c/sub n/} that satisfy /spl Sigma//sub n=1//sup N/(-1)/sup n/c/sub n/=0, where N is the length of the sequence used. It is shown that not only do the SEC sequences maintain the characteristic of envelope shaping for the transmitted signals, the power spectra of the multitone signals constituted from these sequences also have an advantage of sharp roll-off gradient. Methods of constructing SEC sequences are given and their applications to MC-CDMA are discussed.