LTE networks has already increased to 460 in more than 140 countries by end 2015. The fast growth of launches has happened during 2012-2015. It is expected that more than 500 operators in more than 150 countries will soon have commercial LTE network running. The number of launched networks is shown in Figure 1.1. The very first LTE devices supported 100 Mbps in the form factor of Universal Serial Bus (USB) modem. Soon LTE capability was introduced into high end and mid-priced smartphones with the bit rate up to 150 Mbps. By 2015, LTE radio is found in most smartphones excluding the very low end segment at 50-USD. The data rate capability is increased to 300 Mbps, and 450 Mbps, in the latest devices. An example drive test throughput is shown in Figure 1.2 illustrating that it is possible to get very close to 300 Mbps in the good channel conditions in 20 + 20 MHz in the field 300 Mbps 200 Mbps 100 Mbps Figure 1.2 Drive test data rate with Category 6 LTE device Introduction Figure 1.3 Example Category 6 LTE device supporting 300 Mbps the field with Category 6 devices. An example of such a device is shown in Figure 1.3. Also, the support for Voice over LTE (VoLTE) is included, which allows to use LTE network not only for data connections but also for voice connections. 1.3 Mobile Data Traffic Growth The mobile data traffic has grown rapidly during the last few years driven by the new smart- phones, large displays, higher data rates and higher number of mobile broadband subscribers. The mobile data growth for 2-year period is illustrated in Figure 1.4. These data are collected from more than 100 major operators globally. The absolute data volume in this graph is more than million terabytes, that is, exabytes, per year. The data traffic has grown by a factor of 3.6x during the 2-year period, which corresponds to 90% annual growth. The fast growth of mobile data is expected to continue. The data growth is one of the reasons why more LTE networks are required, more spectra are needed, radio optimization is necessary and 