How To Improve the Speech Quality by Increasing the Average Bit Error Rate

Abstract:
The speech quality is one of the most important features of a digital communication system. The intelligibility and the naturalness of the speech are decisive for the user’s acceptance. In this paper we present a scheme for unequal error protection (UEP), which is based on modulation with unequal power allocation (MUPA). The MUPA technique allocates different transmission power to the modulation symbols according to the individual bit error sensitivities of the assigned bits. This corresponds to an intentional increase of the average bit error rate, but improves the speech quality, as the bit error rates of the most important bits are reduced. The average transmitted energy per bit remains unaffected, while the average channel capacity is decreased by MUPA.