re 1.10 Key areas of LTE network optimization network operator during the extreme loading when tens of thousands of customers are in the same location like sports stadiums. The interference management and control channels are the critical areas in those venues. The initial LTE networks did not support voice but CS voice in the legacy 2G and 3G networks was used instead. The CS fallback requires some optimization while VoLTE needs further optimization steps to deliver the same or higher quality voice than with CS voice. Both 2G and 3G networks typically had two frequency bands in use for each operator while LTE networks can have more than six LTE bands. Such complex spectrum allocation requires careful planning how the multiple frequencies are used together. The interworking to the underlying 3G network is also needed for both voice and data until LTE deployment reaches full coverage and VoLTE is used by all customers. The end-user experience is impacted also by the terminal power consumption, by the application performance and by the device operating system. The end-to-end application optimization needs to consider all these aspects to deliver an attractive user experience to the customer's smartphone or other device. The key areas of LTE network optimization are summarized in Figure 1.10 and will be explained in detail in this book. 1.8 LTE Evolution Beyond Release 13 The 3GPP is busy working with Release 13 during 2015 and 2016, but it will not be the end of LTE technology. The target is to utilize the massive ecosystem of the LTE radio also for other use cases and applications. Figure 1.11 illustrates new services that can be supported by the LTE radio and the corresponding technical solution. There are more than 7 billion Introduction New service or application area LTE technical solution LTE Machine-to-Machine Internet of Things (M2M) Group communications, Public safety mission critical push-to-talk LTE Device-to-Device Proximity services (D2D) communication Broadcast services LTE eMBMS Connected cars LTE D2