Abstract
During the recent years, Voice over IP (VoIP) has experienced a wide growth due to, among other factors, the expansion of wireless networks. However, voice transmission over wireless systems has some inherent challenges to beat because of the particular characteristics of the wireless transmission channel. In this work we employ two statistical propagation models, namely, Rice and Rayleigh, in order to evaluate the performance of a VoIP wireless transmission system under different fading environments. We compare the results obtained in these hostile scenarios with those attained in free space situations, in which the physical layer is only characterized by signal propagation losses. With the aim of carrying out this evaluation from a Quality of user Experience (QoE) perspective, we employ the E-model, which has become one of the most relevant planning and quality estimation tools. Concretely, we assess, via computer simulation, the effect of fading over system coverage range and VoIP capacity, using different codecs and different bandwidths on an IEEE 802.11 system. From the obtained results, we observe that VoIP communications suffer a noticeable drop on the achieved QoE in scenarios affected by fading channels. Moreover, the network coverage area and the VoIP system capacity are also negatively impacted by the effect of fading, showing reductions of up to 200 m of distance and 3 VoIP calls, in settings with high levels of fading compared with free space situations.
Keywords: E-model algorithm, Fading, MOS, QoE, Rice propagation model, Rayleigh propagation model, VoIP.E-model algorithm, Fading, MOS, QoE, Rice propagation model, Rayleigh propagation model, VoIP.E-model algorithm, Fading, MOS, QoE, Rice propagation model, Rayleigh propagation model, VoIP.
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