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Audio quality enhancement for ETSI TS 102 361 digital mobile radio standard compliant radios using volume optimization and better forward error correction scheme

2018    Eksim, Ali; Yetik, Hasan

As the mobile radio communication needs of security and emergency services soared, two-way land mobile radio communication systems are evolved from analog to digital. Digital radios have better communication range and noise performance compared to analog counterparts. Although, digital radios provide superior voice quality in most cases, they have hard time to maintain good voice quality and intelligibility in particular conditions, like bad voice encoder-decoder implementation flaws and high frame error rate conditions. In this work, ETSI TS 102 361 Digital Mobile Radio standard is assessed and proposed two optimizations to improve its voice quality for particular conditions in which voice quality deteriorated. First improvement is utilizing better forward error correction coding compared to already in use in AMBE 3600 bps vocoder to improve the overall bit and frame error rate performance. Second improvement is voice volume optimization. By volume control optimization, vocoder frames are evaluated and punch/click noises that saturate volume of vocoder frames are reduced or cleaned. Proposed optimizations are held in vocoder domain and does not intervene the digital mobile radio protocol standards. Due to the proposed optimizations does not interfere with digital mobile radio protocol; they are highly applicable and very cost effective. As a result, we achieved 2.95 dB coding gain using proposed forward error correction. Using proposed forward error correction along with audio volume optimization, digital mobile radio audio quality and intelligibility are enhanced.