Peak power reduction device in communication system
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.
1. A peak power reduction device, comprising:
a unit for dividing digital information to be transmitted into a plurality of streams;
a unit for selecting a modulation multi-value number of the plurality of streams and distribution of transmission power according to a transmission state;
a unit for singular-value-decomposing transmission path characteristics of the streams and precoding the transmission path characteristics of the streams by a right singular value matrix;
a unit for complex-mapping subcarriers of the streams according to the modulation multi-value number;
a unit for converting a complex mapping signal into a time domain signal;
a first unit for storing a conversion result as the time domain signal;
a second unit for, when a peak value exceeding a predetermined threshold exists with respect to an amplitude of the time domain signal, calculating a peak time signal exceeding a predetermined threshold value from the peak value;
a third unit for converting the peak time signal into a frequency domain signal and calculating a converted frequency domain peak signal;
a fourth unit for calculating a peak stream signal by multiplying the frequency domain peak signal by a complex conjugate transpose matrix of a right singular value matrix; and
a fifth unit for limiting an SN ratio of a peak stream signal level corresponding to the modulation multi-value number of the streams with respect to the peak stream signal obtained by the fourth unit to a predetermined deterioration amount or less.
2. The device of claim 1 , further comprising:
a sixth unit for calculating a peak time signal whose level is restricted by converting the level-restricted peak stream signal to a time domain; and
a seventh unit for reducing a peak component by subtracting the time domain peak signal obtained by the sixth unit from the time domain signal obtained by the first unit.
3. The device of claim 2 , wherein a modulation error ratio for each stream is controlled according to the modulation multi-value number allocated to the streams by repeatedly operating the second unit to the seventh unit to calculate a peak-reduced time domain signal multiple times.