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LTE Broadcast part 3/5: Reasons to be cheerful

With three mobile operators, Verizon Wireless, Telstra of Australia and Smart Communications in the Philippines, now having conducted successful trials of LTE Broadcast, it is a good time to assess why at last multicast video transmission over cellular is coming of age.

There have been various failures in the past, such as DVB-H, mostly in Europe, and Qualcomm’s MediaFLO in the US, but they came too early and did not meet all the technological challenges. The underlying factor is the proliferation of tablets and ever larger smartphones, providing users with compelling mobile devices conducive not just for snacking but also consuming longer form content. This in turn has created a surge in video consumption over cellular that threatens to swamp both radio spectrum and the backhaul capacity of radio operators.  LTE Broadcast can save spectrum and fixed network capacity for popular live or linear video content that is consumed simultaneously by a sufficiently large number of people that would otherwise generate multiple unicast streams down to the cell level.

If there are only one or two people in each cell watching a given stream, then LTE Broadcast will not save much spectrum. But there is usually at any one time some relatively popular content being streamed over a given cellular network. Therefore, as various surveys from Ericsson and others have indicated, on average a mobile operator can cut traffic by at least 10% through use of LTE Broadcast. But that does not give the full picture, since the savings will be greater at peak times when more popular content tends to be consumed.

But the killer use case is for venue broadcasting, where hundreds or even thousands of people at say a large sporting event or concert may simultaneously want to tuck into action replays or content relevant to the occasion. Then LTE Broadcast becomes essential both to feed the cell where the venue is located and to distribute the content to devices over the RAN (Radio Access Network). Of course earlier cellular broadcast technologies could also serve venues in principle, but fell down over cost of infrastructure, lack of complaint devices and mobile screens being too small for compelling viewing. DVB-H required significant additional infrastructure investment to deploy, as well as specific upgrades to handsets.

LTE Broadcast will run over all LTE infrastructure and while it is not supported by current commercially available handsets, it will come out of the box with the next generation ready to hit the market in the second half of 2014. It also delivers video much more efficiently than its ancestors such as DVB-H, partly through being based on the 3GPP eMBMS (Evolved Multimedia Broadcast Multicast Service). eMBMS uses OFDM (Orthogonal Frequency Division Multiplexing), which has been incorporated a while in other wireless systems such as Wi-Fi, Wimax and DVB broadcast, but is new to cellular. The key point is that OFDM is a form of inverse multiplexing, splitting the broadcast signal over multiple low bit rate carriers that are therefore closely spaced in frequency, but do not interfere with each other because the waves are out of phase with each other.

This greatly increases robustness against fading at a given frequency, since the signal is split out across a range of frequencies. This robustness enables LTE Broadcast to deliver premium broadcast quality video over cellular for the first time. Apart from eMBMS, LTE Broadcast will in future be able to take advantage of associated developments in video transmission, in particular MPEG DASH for standardized streaming and HEVC (High Efficiency Video Coding)/H.265 for stronger video compression. Taken together these technologies will ensure that LTE Broadcast both reduces bandwidth consumed by mobile video and increases the quality. This is why despite having been bitten before the cellular industry is convinced that LTE

Broadcast will be a great success. Part one in the series by Philip Hunter is here, part two is here and part four is here.
Philip Hunter

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LTE Broadcast 1/5: live debut heralds battles with Wi-Fi to come

The first live LTE Broadcast session delivered recently by Telstra in Australia raised the natural question of why things should be different this time.

The recent history of cellular communications is littered with the skeletons of mobile broadcast’s dismal past, with Telstra’s demonstration as it happens coinciding with the death of the last DVB-H service in Poland. Other notable mobile broadcast failures include Qualcomm’s MediaFLO in the US, which is significant in that the company is now strongly backing LTE Broadcast. Qualcomm’s chipsets are at the center of Ericsson’s LTE Broadcast platform used by Telstra for its live demonstration that served various devices with concurrent video feeds, including a sports match replay, general news and a large video file over the single LTE Broadcast channel.

The same Ericsson/Qualcomm platform will be used in a much more significant test of LTE Broadcast by Verizon at the 2014 SuperBowl in early February 2014. As the most popular US sporting event this will be the perfect springboard for LTE Broadcast, giving it the chance to demonstrate its ability to serve large numbers of users with concurrent streams within a single 4G/LTE cell. This would not of itself prove the case for LTE Broadcast, given that its predecessors could also deliver concurrent streams to multiple users. That after all is the whole point of mobile broadcast. Yet there are important differences this time that suggest LTE Broadcast will at least be a contender for delivering mobile video.

One big difference is that there are now eligible handsets for viewing video, notably tablets but also larger smartphones and a host of emerging hybrid devices that have got consumers hooked onto mobile video consumption when they weren’t before.

The other big difference now is the backing of key industry players and the fact that LTE Broadcast, or more precisely the eMBMS (Multimedia Broadcast Multicast Services) technology on which it is based, is an integral part of the LTE ecosystem underpinning current and emerging 4G cellular services.

All the big industry hitters, including Alcatel-Lucent as well Ericsson and Qualcomm, are full square behind it, along with a host of key second string infrastructure vendors like MobiTV. DVB-H was also an open standard but it required significant additional infrastructure investment to deploy, as well as specific upgrades to handsets. LTE Broadcast will run in principle over all LTE infrastructure and while it is not supported by current commercially available handsets, it will come out of the box with the next generation.

Qualcomm's Mazen Chmaytelli, senior director of business development at its Labs, is on record saying he expects the first LTE Broadcast capable handsets to come to market in the second half of 2014. For these reasons LTE Broadcast will be quite widely deployed, with AT&T as well as Verizon Wireless planning to do so in the US, while Korea Telecom is collaborating with Samsung towards a launch in South Korea. In Europe France Telecom’s Orange and EE have announced firm intentions to deploy LTE Broadcast.

Yet at one time there was equal momentum behind DVB-H and despite the fact LTE Broadcast is much better placed its success is still not a done deal. One reason for that is the advance of Wi-Fi, which may enable venues to cater for large scale events more cost effectively through temporary deployment of hot spots. At the same time versions of existing digital terrestrial standards, such as the DVB’s T2 Lite, could be better placed to meet the requirement for general mass delivery of video to mobile devices. There is a good reason for this.

Outside major events such as Super Bowl where large numbers of people will be consuming the same video streams such as sporting action replays, there will not often be more than a handful of people watching the same content in a single cell and often it will only be one. In the latter case LTE Broadcast collapses to unicast. Yet at any given time there may well be a number of people watching different streams in a given cell, so there is still a need for an efficient video delivery infrastructure, which DVB T2 Lite would be as it has a much larger coverage area than an LTE cell. Within the much larger digital terrestrial coverage area, even mid-tier content would often by consumed concurrently by several people, so that mobile broadcast would save a lot of spectrum. Mobile operators such as EE have stated that the initial “monetization motive” for deploying LTE Broadcast will come from more efficient delivery of video both over the backhaul networks and at the radio level inside cells.

My contention is that these efficiency savings will not materialize outside major events. Even within such events, Wi-Fi may be a more cost effective way of addressing the “Super Bowl” effect and could be offered as a service by mobile operators, which would benefit by offloading the traffic directly onto the more efficient fixed broadband infrastructure. On this count there are already a variety of products available, for example from Birdstep in Sweden, which enable automatic selection of traffic for offloading to Wi-Fi according to specified business rules.

With some operators already talking about temporary LTE Broadcast channels for venues as a future business model, it will be interesting to see how this approach will stack up against Wi-Fi and the answer may be not very well. At least with the upcoming Verizon demonstration at Super Bowl 2014, the battle lines are being drawn. Part 2 is here.