Hitachi-kokusai Electric Inc.

Satoru Ejima

Takehiko Kobayashi

Keisuke Yamamoto

Hiroki Kato

Kei Ito

Tatsuhiro Nakada

Keat Beng Toh

A peak power reduction device includes a unit for dividing digital information to be transmitted into a plurality of streams; a unit for selecting the modulation level of the streams and distribution of transmission power according to a transmission state; a unit for performing singular-value decomposition on the transmission path characteristic of a streams and precoding the resultant data by a right singular value matrix; a unit for performing complex mapping on the subcarrier of a stream according to the modulation level; a unit for converting a complex mapping signal into a time domain signal; a first unit for storing a conversion result as a time domain signal; a second unit for calculating a peak time signal exceeding a predetermined threshold value from a peak value, if any exists, that exceeds a prescribed threshold value for the amplitude of the time domain signal.

Peak power reduction device in communication system

The present invention is directed to reduction of operation amount of likelihood calculation (LLR calculation) in a communication apparatus for performing communications using an extended mapping in which a plurality of bit sequences are assigned to a single symbol point. A receiving unit receives a signal which is transmitted from a transmitting unit by using the extended mapping. A repetition process unit decodes the received signal from the receiving unit by calculating an LLR of the received signal and performing a repetition process. In this case, the LLR is calculated for every bit using a MAX-LOG approximation and a thus-derived approximation formula is multiplied by weighting factors corresponding to proportions of '0' and '1' in each bit assigned to a symbol point closest to the received signal.

Communication apparatus

A wireless communications device and method carries out a process including estimating channel information based on a received signal; generating pseudo-transmission signal point candidates based on the channel information and/or transmission signal point candidates; and generating a replica of the received signal based on the pseudo-transmission signal point candidates and the estimated channel information. The process further includes performing matrix operations on the basis of the received signal and the replica thereof; selecting pseudo-transmission signal point candidates which have a greater effect on likelihood calculations; reverting the selected pseudo-transmission signal point candidates to original transmission signal point candidates and calculating final likelihoods; and restoring the received signal on the basis of the calculated likelihoods.

Growing community of inventors

Tokyo, Japan

Satoru Ejima