スペクトラムスクランブル秘話のフェーディング伝送路における送受同形エンファシスによる通話品質改善効果の定量評価

Abstract

Phenomena of speech quality being hardly damaged from surrounding noise in comparison with SNR or segmental SNR are many times encountered in running vehiculars or airbornes even if the communication is carried without any encryptions. This difference between these evaluations and speech quality is comes from so called masking effect, which strongly appears when communications being carried through such noise with high frequency component as in running vehiculars or airbornes. Especially, the masking effect strongly appears when encryption is employed to prevent communication security from jeopardy according to genius of human voice. At first, in this paper, a new estimation method of speech quality is proposed with base on the Zwicker's method to evaluate qualitative speech degradation when various encryptions being employed. The isomorphic emphasis previously reported by one of this paper's authors, is secondly discussed to quantitatively evaluate the effect in improving speech quality over poor radio channels when encryption is employed. The amount of improving speech quality by employing isomorphic emphasis over radio channel with spectrum inversion is count up to 12 dB through both theoretical analysis and experimental results.