2004 年 58 巻 1 号 p. 91-98
Orthogonal Frequency Division Multiplexing (OFDM) signals consist of many independent subcarriers and have a high peak power. The Partial Transmit Sequence (PTS) scheme has been proposed as an effective scheme for reducing the peak power. The scheme employs phase rotations of subcarriers, and a set of rotated angles corresponds to side information, which is transmitted through the same channel as data or another channel. In this paper a coding technique is considered to improve the performance of both data and side information in an OFDM system with PTS. Since the side information is used at the detection of OFDM, the side information should be recovered before the detection. This is, in general, against the causality, because the side information is not obtained before the detection. We proposed a new coding method based on a rotationally invariant trellis coded modulation for the data and side information. If we insert side information into the position that does not suffer from phase rotation, it becomes possible to correct the error due to rotations after decoding. Thus we can obtain coding gain and peak power reduction in the OFDM system using a PTS. As a result we show that the bit error rate of the encoder is at most twice worse than the normal.