Prompt estimation of channel quality for personal communication systems

Personal communications, including the personal handy-phone system, require high-quality voice transmission. In the wireless section, a 32 kbit/s adaptive differential PCM (ADPCM) voice coding method is applied. The ADPCM voice coding method has been assumed to be applicable to channel conditions with very low error. In order to realize high-quality channels under slow fading conditions, there must be a function that estimates channel quality instantaneously and reflects the result in voice quality improvement and interference avoidance. This paper notes that the degradation of voice is affected by an error pattern added to the receiver side ADPCM code (4 bit), which is used as the input to the ADPCM decoder. The ACD (ADPCM code detection) prompt channel quality estimation method is proposed, which can promptly detect errors that contribute greatly to channel degradation. Examples of applications of the burst degradation estimation circuit and the interference position estimation circuit are presented and the usefulness of the proposed method is demonstrated.