e rate during the transmission of voice (40 kbps) and silence frames (3 kbps) and the voice activity of 25% of talking, 25% of listening and 50% of silence. The third-party SIP application with AMR WB codec averaged as low as 8 kbps when using VAD. The lower average throughput in this case was a consequence of not transmitting practically anything during silence periods, which on the other hand contributed to a significant reduction of the MOS. This same application with EFR NB codec generated up to 17.3 kbps, driven by less efficient VAD. The three OTT VoIP applications ranged between 17.6 and 42.8 kbps average throughput, depending on the codec they used and the particular implementation of features such as of codec rate adaptation or VAD. Furthermore, at PDCP layer and radio interface, VoLTE and SIP applications using dedicated bearer with QCI1 QoS will further reduce the throughput when ROHC is used. The lowest power consumption was provided by 3G CS call with 153 mA because of the integration of the voice application on the radio chip. VoLTE power consumption was 232 mA LTE Small Cell Optimization SIP EFR SIP AMR OTT AP1 OTT AP2 OTT AP3 VoLTE Figure 16.27 Measured throughput and OTT VoIP power consumption more than 300 mA. OTT VoIP applications were clearly the least efficient, since they used the default non-GBR LTE radio bearer and could not make use of optimized discontinuous reception (DRX) settings for VoIP traffic pattern. These applications required the UE to remain constantly active during the whole duration of the voice call. In the case of native VoLTE and SIP clients, they used dedicated radio bearer with guaranteed bit rate QoS (QCI1) and optimized DRX settings for VoIP traffic pattern. We will show later in this chapter that the integrated VoLTE client can further minimize the power consumption. This kind of optimization will not be available for third-party SIP clients or OTT VoIP which would still need to run on top of the os and using smartphone's application processor. Figure 16.29 shows a m