The audio quality for each technique is evaluated through the use of subjective testing. Coder, network and re-assembly delays are presented. Information carried over two or more independent channels is likely to arrive at different times. Additional coding and re-alignment techniques add to the overall delay. The increase in round trip delay of an interview dispatch was expected to impact heavily on the audiences perception of the quality.
Speech coding quality rather than the delay is therefore the focal point for on-going work.
The standard GSM handset offers two possible digital signal entry points, marked X and Y in Fig. 1 - Methods of sending medium quality audio news dispatches. At the studio, the two or three channels are re-combined using QMF techniques which cancel the effects of aliasing. The data channel includes excellent forward error correction and allows the use of independent coders. Y the output of an appropriate coder is distributed over two or three GSM transparent data channels.