Karl Hellwig

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A MUSHRA listening test carried out by Ericsson Research showed that users clearly prefer AMR-WB voice over uncoded narrowband voice. (MUSHRA: multi-stimulus test with hidden reference and anchor, ITU-R recommendation BS.1534.) In particular, AMR-WB is superior to the 64kbps pulse-code-modulation (PCM) coding of the public switched telephone network (PSTN).(More)
The European Telecommunications Standards Institute (ETSI) has just defined an Adaptive Multi Rate (AMR) speech codec standard for the GSM system with a multitude of source and channel coding rates. The standard aims to provide robust high quality speech together with the flexibility to deliver radio network capacity enhancements by means of low bit-rate(More)
The Enhanced Voice Services (EVS) codec was standardized by 3GPP in 2014. This codec offers significant gains in voice quality, efficiency, channel error robustness over any other existing speech codec and far better music quality. Operators run voice services on a large installed base of 3GPP Circuit-Switched (CS) 2G (GERAN) or 3G (UTRAN) radio networks.(More)
A series of 1,3-diphenyl-6-alkyl/arylfulvenes was prepared, and the electrochemical properties were investigated. The addition of phenyl groups about the fulvene raised the reduction potential and helped to stabilize the electrochemically generated radical anion. The addition of various functional groups onto the phenyl ring at the 6-position of(More)
This document specifies the payload format for packetization of Global System for Mobile Communications Half Rate (GSM-HR) speech codec data into the Real-time Transport Protocol (RTP). The payload format supports transmission of multiple frames per payload and packet loss robustness methods using redundancy. Information about the current status of this(More)
This document specifies the payload format for packetization of Global System for Mobile Communications Half Rate (GSM-HR) speech codec data into the Real-time Transport Protocol (RTP). The payload format supports transmission of multiple frames per payload and packet loss robustness methods using redundancy. Information about the current status of this(More)
Text telephone devices are text-based terminals that allow the users to communicate by text via fixed-line telephone networks. Since cellular phone systems are sometime subject to severe radio channel impairments and the modem signals of these text telephones are therefore not always transmitted reliably, the Federal Communications Commission (FCC) has(More)
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