Improving the Speech Quality with OSC: Double Full-Rate Performance Assessment

Speech quality is an important measurement for performance evaluation in a wireless mobile communication system since voice is still the most used service on it. The speech quality evaluation in GSM system employing narrowband and wideband AMR codecs with Orthogonal Sub Channel (OSC) technique is addressed in this paper. OSC is a feature proposed in 3GPP GERAN to double circuit switched capacity in GSM networks. It has introduced two new channel modes, namely Double Full-rate (DFR), and Double Half-rate (DHR), which have doubled capacity when compared to legacy AMR channel modes.Many of the efforts in standardization are concentrated on studying hardware improvements lead by AMR DHR usage over AMR HR channel mode. Although AMR DFR has not brought hardware efficiency improvements over legacy channel modes, in this paper it is shown that speech quality is improved over AMR HR with the same blocking capacity; therefore it is a good solution for some interference limited networks. Furthermore, we also investigate the speech quality of wideband AMR DFR codecs which provides a substantial improvement when compared with narrowband AMR.