Takuya Kazama, Kazuki Miyazawa and Masahiro Muraguchi, Tokyo University of Science, Japan

We have found out that the CAZAC- OFDM accords the amplitude of IFFT output signal with the amplitude of input DATA and the time ordering of IFFT output signal is unambiguously determined. That is, the OFDM time-domain signals, which are composed of many sinewaves, can be shaped by CAZAC precoder. As one application example that can use this characteristic of CAZAC precoder, we propose a new technique of symbol timing estimation, which enable to avoid the use of the preambles and guard-intervals. Conventional OFDM systems introduce guard-intervals for symbol timing estimation and reduction of multipath effect. Visible light communications (VLCs), which are one kind of line-of–sight communications, does not require consideration of the multipath channel. Therefore, if we embed null data at a fixed position in time-domain, we will easily estimate the symbol timing in the receiver side.

OFDM; CAZAC sequence; Zadoff-Chu sequence; Symbol Timing Estimation; VLC.