In this study, the authors present results of a call testing campaign using voice over long term evolution (VoLTE) technology on the radio access network of the operator Telecom Italia mobile. The quality of the voice call is expressed by means of the mean opinion score (MOS). The electromagnetic propagation environment has been reproduced within a reverberation chamber, and its effect on MOS has been evaluated by varying the signal strength, i.e. the reference signal received power and the signal-to-interference noise ratio. The aim is to find a correlation between the radio propagation environment and the perceived quality of the speech. Regardless of the networks technology, voice quality could be impacted by several factors: traffic load of LTE evolved Node B, quality of service, radio pathloss, mutual radio interference, multipath and so on. Interference and multipath are added to the useful signal in order to deteriorate the MOS, until the VoLTE calls dropped. Target of such work is to properly set the thresholds that trigger a handover of single radio voice call continuity to other radio access technologies (UMTS or GSM). Tests take also into account the adaptive multi-rate CoDec selected by the network.

中文翻译：

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在混响室内测试VoLTE平均意见得分

在这项研究中，作者介绍了在运营商意大利电信移动台的无线接入网上使用长期演进语音（VoLTE）技术进行的通话测试活动的结果。语音呼叫的质量通过平均意见评分（MOS）表示。电磁传播环境已经在混响室内再现，并且通过改变信号强度（即参考信号接收功率和信噪比）来评估其对MOS的影响。目的是找到无线电传播环境和语音的感知质量之间的相关性。无论采用哪种网络技术，语音质量都可能受到以下几个因素的影响：LTE演进型节点B的流量负载，服务质量，无线电路径损耗，相互无线电干扰，多径等。干扰和多径会添加到有用信号中，以使MOS恶化，直到VoLTE呼叫掉线为止。此类工作的目标是适当设置触发单个无线电语音呼叫连续性切换到其他无线电接入技术（UMTS或GSM）的阈值。测试还考虑了网络选择的自适应多速率CoDec。