正交多载波调制中峰值因子的一种减小方案

A method for reducing peak factor in orthogonal MCM

在多载波调制系统中,通常调制信号的平均功率恒定,且和实际发送的信息符号向量无关,此时,由N个子载波组成的多载波信号的峰值因子(PF)等于10lgN(dB)。提出了减小多载波调制系统中PF的一种方案,对于瞬时包络功率的最大值超过所给门限值的信息符号向量,所有子载波的幅度被降低至门限值,而对于瞬时包络功率的最大值低于门限值的信息符号向量,所有子载波的幅度被增大至门限值。采用这种方法,整个调制系统的PF被减小,而净比特速率保持不变,但系统的误比特率(BER)略为增加。

In multicarrier modulation (MCM) systems,the average power of the modulated signal is usually constant and does not depend on the vector of information symbols which are actually transmitted.In such a case,the peak factor (PF) for a MCM signal composed of N carriers is 10lg N(dB).A method for reducing PF in MCM system is proposed.For each vector of information symbols the maximum value of the instantaneous envelope power exceeds some given threshold value,the amplitudes of all carriers are reduced to obtain equality between the maximum of the instantaneous envelope power and the threshold.Moreover,for each vector of information symbols the maximum of the instantaneous envelope power is lower than threshold,the amplitudes of all carriers are increased to obtain equality.Therefore,the PF of the whole modulation system is reduced without reducing the net bit rate by using the method,and then the bit error rate (BER) is increased in some sort.