Investigation of Voice Frame Erasures in GSM

Abstract

The experimental investigation of individual voice quality is carried out in common GSM communication system. There are scientific publications in which methods of GSM frame-level error measurements are presented. These works involve data transfer channel, RLP packet traces. In this paper we take note, that in GSM cellular communication system voice and RLP packets are coded with different channel codes, voice packets have different calculation of parity bits. We have presented a framework for measurements and collection of voice frame erasure traces in GSM network. For measurements we constructed special test-bed system. The main idea of measurements is based on speech frame substitution function which is implemented in the codec. The scheme of experimental test-bed, integrated in GSM network infrastructure, consists of stationary and mobile parts. The stationary computer generates the special test signal. The measurements of lost frames are performed in mobile part by using end-user equipment. The collected traces of erasure frames will be used for development of models of lost voice frame series and for estimation of individual voice quality. The preliminary voice frame erasure trace analysis is presented. Ill. 5, bibl. 8 (in English; summaries in English, Russian and Lithuanian).