ore detailed analysis of the throughput during the duration of the call for some of the cases. It can be observed how VoLTE provides a clear correlation between the throughput and the voice pattern used for the test, with a peak IP throughput of 40 kbps and a minimum of 3 kbps during silence periods. The SIP AMR WB application shows a similar 3G CS VoLTE Figure 16.28 Current consumption Smartphone Optimization VoLTE OTT App1 Time (seconds) Time (seconds) OTT App3 SIP AMR WB Time (seconds) Time (seconds) Figure 16.29 Instantaneous throughput over 2-minute call pattern, but with variable bit rate during speech (25-45 kbps) and practically zero during silence periods. OTT application 1 produced a very similar throughput pattern as VoLTE; however, the peak throughput rose up to 45 kbps, and the low throughput during silence periods did not go below 10 kbps. On the other hand, OTT App 3 did not quite show the same pattern and transmitted around 42 kbps most of the time with some peaks of up to 60 kbps. Knowing the average throughput figures for different VoIP applications is important users, considering that today's cellular contracts do have some kind of monthly quota. Taking the numbers from the examples above, it is possible to estimate how many voice minutes could one user afford considering a certain application and a fixed data plan. Table 16.2 shows how in case of VoLTE more than 112 hours of talk time could be provided with a 1 GB data plan, while OTT application 3 could only achieve up to 27 hours with the same plan. Table 16.2 VoIP minutes with 1 GB data plan using 50% activity voice pattern Average throughput Cost of 2-minute call (Kbytes) VoIP minutes (hours) (kbps) downlink + uplink with 1 GB data plan SIP EFR 519.0 3946 (66) SIP AMR WB 249.0 8225 (137) SIP AMR WB NoVAD 1218.0 1681 (28) OTT application 1 528.0 3879 (65) OTT application 2 1074.0 1907 (32) OTT application 3 1284.0 1595 (27) VoLTE 306.0 6693 (112) LTE Small Cell Optimization Current Consumption and Discontinuous Transmission/Reception (DRX) 