It can be estimated that in modern telecommunications, there are major effects from video services which are going to be the global driver for data traffic growth on fixed and mobile networks, resulting in the increase of user-generated video transmission. The increase of audio and video is fast and strong due to the transition of “traditional” circuit switched voice services to high-speed packet data networks – which is increasingly the public Internet. VoIP is one of the solutions to facilitate this transition, and makes voice calls just one of the many data services over the Internet. Compared to previous circuit switched solutions, this transition provides much richer calls and by default, there is a set of options users can select to enhance the voice call experience, for example, by including text, special characters, photos, video, audio and other accompanying information to the same call. This transition not only happens for the public use of the tele services, but increasingly also for the company use. In addition to technological benefits making the content delivery richer, the important benefit of VoIP-based calls is reduced cost.
Video and, in general, multimedia contents that have been possible to consume via fixed networks have driven users to wish for similar on-demand access to content via mobile devices. This has not been very
10 The Telecommunications Handbook 2012 2014 2008 2010 2004 2006 2000 2002 1996 1998 1992 1994 2016…2020 5G 4G + evolution “pre-4G” 3G + evolution 2G + evolution GPRSUMTS GSM Ph1 3GPP 3GPP2 IEEE HSDPA HSUPA HSPA/+ EV-DO Rev. A EV-DO CDMA 1x IS-95A LTE Rel 8 LTE Rel 9 LTE Rel 10 LTE-A 802.16e (WiMAX) 802.16d 802.11 b/g 802.16m First mobile data Mobile data established First mobile video Mobile video established
Figure 1.7 The basic principle of the states in the cellular systems development where video delivery is suitable via mobile communications systems.
logical yet via the network solution up to basic 3G mobile systems, due to the limitations of data rates and delays of data transmission, and due to economical aspects. LTE is also now a suitable enabler for multimedia contents.
Nevertheless, if the consumption of the video services increases substantially, the capacity problem may be present in the hot spot areas of the cells as the connections are established point-to-point. In any case, LTE allows for significantly higher capacity at a lower cost per bit, which results in highly improved commercial delivery of video services.
Figure 1.7 presents the high-level development of mobile communications with those technologies that are suitable for more demanding video contents.
Along with evolved 2G and 3G technologies, including GPRS of GSM and 1xRTT of CDMA, and HSPA of 3G, the first data services started to take off. Nevertheless, these services were merely basic ones like simple web browsing and email. In fact, it was possible to utilize video services already via 1G-systems [9], but this type of solution was not very practical prior to the deployment of evolved 2G stage and 3G networks that provided sufficiently high bit rates for a fluent video experience. Also the high cost of data delivery and limited functionality of mobile devices meant that the time was not yet ready for serious video service utilization.
Increased capacity demand is constant for voice and data services as well as for the resulting signaling traffic. This also requires increased capacity for transport networks.
One of the modern phenomena is that ever more audiovisual content is available for on-demand streaming, as a result of hugely increased activities of user generated content. There are various types of media for this new method of content production, including TV network programming and applications or services like YouTube. The popularity of the latter has exploded Internet traffic. According to Ref. [10], users of YouTube
Introduction 11 stream in average 50 videos per month. Furthermore, from 2006 onwards, YouTube in the US consumed more capacity than the entire World Wide Web in 2000. When streaming this type of content via mobile networks instead of fixed networks, the quality has been notably lower due to the capacity restrictions as the format has been the same for all the use cases.
An important factor in video consumption is screen size and resolution. Other relevant parameters are frames rate and bit rate. Table 1.2 summarizes some of the most relevant use cases for different resolutions.
The available throughput for LTE, and especially LTE-Advanced, is clearly higher than any other previous mobile communications solution can offer. Nevertheless, there are situations where the network is in danger of saturating due to excess of simultaneous users.
The service delivered for single users requires dedicated resources from the network. LTE is suitable for high-speed and high-capacity transmissions, so the bit rates that are required by the logical screen sizes of mobile devices can be handled. The problems might arise when multiple users are sharing the resources of the same site, which also increases signaling load.
One of the solutions for this type of situation is the use of MBMS (Multimedia Broadcast Multicast Service) for LTE as presented in Figure 1.8, that is, enhanced MBMS (eMBMS), which is defined first time in the 3GPP Release 9. The previously defined version of MBMS, according to the Release 6 specifications, has not been successful in practice as the demand for PTP (Point to Point) voice and data has required all the capacity. Now, eMBMS may provide a suitable platform for user experiences like television streaming as well as enhanced and interactive contents streaming along with the possibility to show, for example, common URLs for the customers, and move to single PTP connections per user. Some use cases for the eMBMS service could be football stadiums where repetition of the goals can be observed via eMBMS television service. The absolute benefit of this broadcast type of service is that the operator needs to define only the broadcast channels without variations of the capacity as all the users under the eMBMS cell receive the same contents (or, selecting the contents via multiple channels) without utilizing uplink capacity. The obvious disadvantage of this solution is that content must be prescheduled which is comparable with fixed network television programs.
The MBSFN (Multicast Broadcast Single Frequency Network) can be utilized in order to optimize the broadcast mode. It makes bit-synchronizing transmission via a number of eNBs in such a way that the contents can be transmitted at the same time and frequency. The benefit of SFN is that there may be SFN gain in the reception of the signal, according to the principles of OFDM technology.