Simulation-Based Estimate of QoS for Voice Traffic over WCDMA Radio Links

WCDMA radio links are subjected to multipath fading which introduce burst errors in the transmitted vocoder frames. This paper presents a methodology for assessing the impact of bursty frame errors on voice quality as measured by MOS (mean opinion score) using waveform level simulations. The approach presented consists of simulating the frame error sequence and mapping the frame error sequence to a sequence of instantaneous MOS values using the ITU E-Model and a recency model. The proposed methodology is applied to estimate the QoS for voice traffic over a wide variety of WCDMA radio channels. Both average MOS scores and link availability (defined as the fraction of time the MOS is greater than an acceptance threshold) are estimated. It is shown that there exits a simple relationship between the average frame error rate (which is a parameter for the physical layer design) and the average MOS and link availability for voice traffic over a broad range of radio channels with multipath fading.