ample, 19 UEs with a 10 to 1 scheduling ratio generate the radio load equivalent to 190 UEs with a 1 to 1 ratio. In Figure 16.35 it can be observed that VoLTE is not affected at all by any background load level, since its packets get always prioritized over FTP. Only increased load of other VoLTE users may eventually have an impact on the quality. On the other hand, there is an impact of bad radio conditions on the MOS, which in this case was translated in a drop from 3.9 to 3.5 POLQA score. This reduction is caused by additional jitter and delay due to packet retransmissions at the radio interface. It is important to note that 3.5 is still very good quality, actually better level than AMR NB in good radio conditions. OTT VoIP, while delivering very good MOS in low load, quickly experiences quality reduction in relatively low to medium load and becomes very unstable in medium to high loads, where not only the MOS is reduced, but high drop call rate (DCR) is experienced. The mouth to ear delay in OTT VoIP case also increases proportionally to the load while remaining stable for VoLTE; see Figure 16.36. 16.8 Smartphone Battery, Baseband and RF Design Aspects This section presents solutions and trends in optimizing smartphone power consumption in three domains: Trends in smartphone battery capacity Trends in cellular chipset power consumption performance Impact of small cell deployments on smartphone battery life 16.8.1 Trends in Battery Capacity Smartphone's battery life is perhaps one of the KPIs when it comes to measuring user expe- rience. In many instances, battery life is still published for the traditional voice talk time Smartphone Optimization 2007 2008 2009 2010 2011 2012 2013 2014 2015 2007 2008 2009 2010 2011 2012 2013 2014 2015 Year of commercial launch Year of commercial launch Figure 16.37 (a) Trend in screen size. (b) Battery capacity trend in smartphones. Data extracted from 388 smartphones and smartphone standby time. These metrics, inherited from the era of the voice-centric fea- ture phones, no l