We have been there before with DVB-H, Qualcomm’s MediaFlo and others, but now we can say for sure that mobile broadcast, or more strictly multicast, is here to stay. The time is right with LTE technology providing the bandwidth, while screens are now large enough and good enough to display compelling video, fuelling massive growth in mobile data.
Besides it is not just video that benefits from multicast delivery but a host of other services too, such as emergency alerts, software updates and various location based applications, like real time traffic updates.
Facebook is interested in simultaneous delivery of apps and is even touting its new membership of the LTE Broadcast User Forum as evidence that it is now cooperating with operators to reduce the load on their networks.
This forum has really taken to the air at Mobile World Congress 2015, with Ericsson in the driving seat accompanied by the GSA, the GSMA, INDYCAR, Intel, KPN, Qualcomm Technologies, Telstra, SingTel and Verizon, as well as Facebook, all providing live demos of new use cases and functions for LTE Broadcast.
Broadcasters such as the BBC alongside other major carriers like Deutsche Telekom, EE and Telecom Italia have also been adding their weight to growing LTE Broadcast momentum, through various trials and beta deployments. The chance now of LTE Broadcast suffering the same fate as its predecessors looks vanishingly slim.
There is still though some confusion over what LTE Broadcast can and cannot do. It operates as a single frequency network (SFN) in multicast mode, being a part of the 3GPP LTE standards set known as evolved Multimedia Broadcast Multicast Service (eMBMS). It extends existing LTE/ Evolved Packet Core (EPC) systems with efficient point-to-multipoint (PMP) distribution, enabling multiple users to receive the same content simultaneously, both within individual cells and across a wider mobile network. LTE Broadcast functionality is now available for commercial launch, beginning with Release 9 and with additional enhancements promised in future 3GPP releases.
One of LTE Broadcast’s benefits is that the multicast can be applied on a cell by cell basis so that it is ideally suited for partitioned delivery of local services that can be location based down to single cells, as well as for national broadcast. All cells participating in an LTE Broadcast SFN send the same data during exactly the same radio time-slots, so that they effectively operate as a single large cell. There is also support for dynamic switching between unicast and the SFN multicast mode, so that the moment a particular stream passes a threshold for popularity, it can be moved at once on the fly to LTE Broadcast mode.
Although the likes of Facebook are motivated at this stage by the growing network burden of app delivery, proliferating video is the main driving force for LTE Broadcast, above all with the Telcos and Cellcos. Against a background of rapidly growing mobile data, the proportion accounted for by mobile video is set almost to double from 40% (or 50% depending on who you believe) in 2013 to 70% in 2017. This is partly on account of the growing pervasiveness of video in non-TV applications such as online news delivery and social media activity. Some of these applications themselves will benefit from LTE Broadcast, for example in live news updates.
The misunderstanding arises over the role of LTE Broadcast for delivery of content that is very popular, but is not consumed by all users simultaneously. This would be the case for some VoD content and also viral YouTube videos say, even though the latter have been presented as a use case for LTE Broadcast. It can be a use case, but only as part of a “RAN (Radio Access Network) Last Mile CDN”, where LTE Broadcast is used for preemptive distribution of popular content to the user’s device.
This effectively extends existing caching solutions beyond the base station, or eNodeB in LTE parlance, to the end device. This will work fine for some applications, such as distribution of certain viral clips or software updates, but suffers from the fact that within each cell everyone who opts in receives it, which is not ideal given the limited storage capacity available on the device. It will only work with the help not just of smart prediction algorithms to work out which content to download over these last mile CDNs, but also cooperation from the device in determining what to store and what to ignore according to the user’s preferences.
In some cases straightforward edge caching would be more appropriate than LTE Broadcast, for example where a given piece of content is popular at a national level but not down to individual cells. In that case it would make sense to cache within the network to reduce backhaul load but then still unicast across the RAN.