The latest from Telecom-Funda
| Is mobile video traffic quite the threat that everyone thinks? Is the so-called "optimisation" approach flawed? |
| I smell the "Tyranny of Consensus", about mobile video data traffic. This is a long blog post examining the "optimisation" of video for mobile. It forms part of Disruptive Analysis' ongoing research into policy & traffic management. For more details on custom work, please contact Dean Bubley directly . Recently I've been bombarded with vendor announcements of video optimisation solutions, DPI and charging products, and lots of slides suggesting that operators might try to charge extra for mobile video traffic that is "swamping" 3G and 4G networks. Everyone is gearing up for "personalisation", tiered services and so forth – and even trying to talk up the prospect of video-optimised data plans. Everyone's putting out PR-driven surveys with predictably trite answers to loaded questions, usually ignoring cause-and-effect. Normally when there's this level of consistency in stance, it's wrong. Or it's hiding something. Most of the noise is coming from vendors of traffic management solutions sitting in the GGSN or in a box on the Gi interface – the link between the operator's core and the Internet itself. Typically, these compress, transcode, buffer, block or generally fiddle-about with video traffic, with varying levels of sophistication and subtlety. Vendors in this general area here include Acision, ByteMobile, Cisco, Flash Networks, Mobixell, OpenWave, Vantrix and assorted others. Some of them try to second-guess what's going on in the radio by looking at throughput rates and other indirect indicators and only act when there's a perceived problem. Some can do relatively benign "lossless" compression which doesn't actually change the content. Some try to limit the amount of video that gets downloaded to the player's buffer, in case the user abandons viewing, closes the session and "wastes" the data already transmitted. Some control the numbers of parallel (concurrent) IP connections the device can use. Conspicuously, the more radio-centric vendors have been comparatively quiet about video – although it's possible they're just looking forward to selling upgrades to LTE, rather than reducing traffic. What's the problem? So, is mobile video (a) really the problem that everyone suggests, and (b) if it is a problem, are they going about fixing it in the right way? Obviously, it needs to be acknowledged that there's a ton of published information (and obviously more in private) that talks about the % of traffic volumes attributable to "video". So we know from Bytemobile, for example, that >40% of total global mobile data traffic in 2010 was video - at least from the networks they can measure. But then there's a bit of a "so what" there - as other analysis points out that usually only a few cells in a mobile network are actually congested, and we also know that there are plenty of other weak spots beyond data volume, such as RNC signalling storms, that cause congestion. (The actual definition of video is that's something that's rarely or poorly defined itself. Is near-photorealistic cloud gaming video? Augmented reality overlays? A flash animation of a cartoon? Discuss) It's about User Experience. Really? So should we take at face value the claims of the video-optimisers that it's really about "enhancing user experience" as many people claim? (Everyone hates stalling video streams, don't they?). Or is it more about manufacturing a convenient bogeyman: an excuse to sell boxes to help operators "personalise" their mobile broadband or raise prices? Video "consumes" lots of bits, so it must be evil, right? Never mind that in most of the world, mobile data is now priced by MB / GB tiers and quotas, so surely 3GB of email is just as evil as 3GB of video? Or more, given the greater signalling load. And doesn't the act of compressing traffic *unnecessarily* reduce the chance of upselling the user to a larger quota? Surely, when there's no real cost impact or congestion risk, doesn't it make sense to let users download as much as they want? Let the user, or app/content provider take the responsibility for reducing volumes if needed. And never mind that the majority of mobile video still goes to PCs with USB modems, not tablets or smartphones, especially outside the US. Modems that have generally been sold by operators as alternatives or complements to fixed broadband, so it should be neither surprising nor a cause for action when customers use them for that purpose. (Although it's interesting that T-Mobile UK has recently suggested that you should save your video usage for your proper network at home). It's desktop versions of YouTube or iPlayer, using Flash or HTTP, that are generating the tonnage - typically indoors. And people are tolerant of delays & buffering on PCs, and also know how to use the toggle for 360/480p or SD/HD. In other words, a sizeable proportion of mobile video traffic is solely generated by operators' mis-selling and mis-pricing of PC dongles as real alternatives to ADSL and cable broadband. Now obviously here there is a major issue: *when* a given cell or sector is actually congested, or a backhaul link, then one incremental video causes much more of a problem than an extra email. But all the coffee-table stats about "10% of users consuming 90% of the bandwidth" generally fail to state whether they also cause 90% of the problems. It's an anecdote, not a problem statement - especially as most of that 10% are PC users who've been sold a product designed specifically (and knowingly) for high consumption. There's much less data to suggest that actual congestion is caused by bulky things like video streaming, or just that there are 20,000 people at Kings Cross Station at 9am on a Monday morning checking their email simultaneously. Anecdotally, I've spoken to operators that have agreed that the real busy-hour, busy-cell situation is much more complex than just blaming YouTube. To give an analogy: I drive my car 4000 miles a year, as I live in central London and mostly use public transport. But I contribute more to road congestion than someone living in the middle of Wales, driving 40,000 miles annually from their cottage to town and back. Data "tonnage", like mileage, is a lousy predictor of problem causation – yes, there's probably a positive r-squared, but correlation is weak. But volume is easily measured, and to an uneducated ear it "sounds" fair to penalise volume, especially when prefixed with emotive PR gibberish like "data hogs". Forecasts Everyone's seen the Cisco VNI forecasts for mobile video network traffic... but are they (and others) quite as accurate and meaningful as many seem to think? I certainly agree that larger screen sizes means that video data will expand for the same duration of viewing. But other mobile applications for smartphones are proliferating too. Yet unless I'm missing something, the biggest growth in usage (minutes / events) is around social networking, gaming and the like. Yes, Facebook friends can embed or link to a video clip... but doesn't the growing amount of time spent messaging and communicating reduce the number of "snacking" opportunities to watch video? If you have 3 minutes waiting for a bus, do you watch YouTube on your phone, or message your friends or send a cleverly-crafted tweet or status update? I'm also not convinced that there's going to be a perpetual growth in minutes of video delivered over cellular macro networks to mobile devices *in congested cells*. There's too going to be many ways to offload and cache the content (eg podcasts, or connecting via WiFi or femtocells). Many of the places where people watch video or use 2-way video applications will be those with WiFi available. Those home with both fixed and mobile broadband will also increasingly use femtocells. Both almost completely eliminate congestion - especially if they route traffic promptly to the Internet rather than piping it back through the core. In any case, video will need to be treated differently by charging, optimisation and policy servers if it is delivered by a dedicated indoor solution. All such elements need to be made femto-aware to be useful. So is the overall "problem" of macro-cellular mobile video going to get worse? Or is it manageable just with normal capacity upgrades and tiered pricing rather than complex control infrastructure, and questionable "optimisation" practices that are perhaps not optimal for user, content owner or operator? Why optimise in the network anyway? It's also worth noting that two of the most widely-used and successful mobile applications actually monetised by operators - BlackBerry's email service and Opera's Mini web browsing proxy-based service - are both self-optimised and data-compressed. The special magic is in RIM's or Opera's own servers and clients, not in the operator network in between. So why should video be any different? YouTube, the BBC and others are much more mindful of their users' quality of experience when watching their content than the operators. The only way to measure real QoE is directly from the device or software client. Trying to decode "user experience" from the Gi interface is like a doctor diagnosing an illness by looking at how red your nose is, through a telescope from a mile away. Maybe the throughput has dropped because the user went to the basement for 30secs? Maybe a window was minimised? Maybe another app on a multitasking device squeezed out the video client with a big download? Maybe there's an OS glitch, or some other user intervention? The network does not - and cannot - know this. There has even been some talk of network boxes checking that the video size doesn't exceed the phone's screen resolution, and reducing it to fit. This is astonishingly arrogant and apt to create huge user dissatisfaction (and perhaps lawsuits), as it ignores the possibility of the user zooming-in to part of the video, saving it to memory for later use, outputting via the TV port on some phones, or just using the device as a tether or modem. Yes, some network elements can, in some instances, improve experience, some of the time. But it's inconsistent and unprovable, and may well have hidden side effects elsewhere. But it's like a spark-plug manufacturer claiming it can improve your driving experience with a new type of "optimising" plug. Yes, sometimes it could make the engine smoother and the driver experience better. But it's not much help if the tyres are bald - and it might also mess up the fine calibration and actions of the engine-management chip. The gating factor is the radio network The other elephant in the room is radio *coverage*, not capacity. Many 3G networks are still like Swiss cheese, with "not-spots" still common, especially indoors. The woolly survey questions about video user experience generally don't ask respondents if they live in a basement, or a building with metallised windows. Much of the problem is nothing to do with congestion - it's the pesky nature of radio link budgets. You can't "optimise" video through brickwork. Not only that, but the risible notion of offering "premium video" mobile data plans with so-called silver/gold/platinum service tiers generally overlooks the realities of physics, and the inter-dependence of shared media. Who's going to extra pay for "priority" video when often you can't get 3G at all? I'm writing this on a train – where I might actually want to watch video on my PC via mobile – and I'm lucky if I can get GPRS connection most of the time. I might pay extra for national roaming onto a competing network which can actually supply me with connectivity - but I'd rather just churn outright. And what happens when a platinum user is right at the edge of the cell & wants a video? Do you boot off 70 gold-tier users who've got better radio conditions in the middle of the cell, just to serve them? In fact, even doing this potentially raises issues with consumer protection laws - the only way that HSPA can even theoretically get to 7.2 / 14.4 / 21 Mbit/s is by biasing traffic towards those people who've got the best signal. If you change the algorithm, it potentially makes the advertising claims false. In conclusion Overall, Disruptive Analysis believes that there is a good chance that the fears about mobile video traffic are being overstated, and being used as a smoke-screen to permit arbitrary degradation of video content, by unsophisticated boxes placed in the wrong part of the network, ill-equipped to understand the real causes of congestion and poor end user-experience. Regulators should scrutinise very carefully whether covert transcoding of video on uncongested links contravenes new views on Net Neutrality that permit only necessary and proportionate management. They should also enforce requirements on transparency stringently – a subtle "we reserve the right to manage traffic" in the terms & conditions is insufficient: there should be detailed and possibly realtime information on any active management / compression of traffic. Content providers and aggregators should track whether their output is being modified over cellular networks without their permission or awareness, and should consider using encryption to protect against covert manipulation. The should embed agents in the browser or client app to detect unwanted "optimisation" (perhaps through digital watermarks or steganography) and alert the user when the operator is modifying the content in the background. Operators should aim to work with content providers to enable them to optimise their content in the best fashion – either via rate-adaptive codecs, user alerts about congestion, altering frame rates, editing the video or other mechanisms. Some form of congestion API (ideally real-time but initially less-accurate) will help immensely. They should also pressure all of their core network and so-called "optimisation" vendors to adopt strong measures for radio-awareness and device/user-awareness. Despite the hype about charging upstream content providers for "premium" QoS, operators should recognise that this will remain a pipe dream owing to the complexities of radio. If it works, it'll happen first in fixed networks, not mobile, where there's much more control and predictability. There's certainly no chance that a video provider, or user, will pay extra for so-called QoS if the network still has poor coverage For those operators looking at offload, they should reject any policy management or optimisation solution which cannot distinguish between macro and femtocell traffic, or which cannot "optimise" by helping the user to connect to faster/less-congested WiFi if available. They should also be extremely sceptical of so-called personalisation services, pricing different traffic types (not "services") differently, that look good on paper, but which are completely impractical and don't reflect the reality of applications and the web, such as mashups. Remember, video is not "an application", it's 10,000 applications, each of which needs individual consideration if personalisation is to be applied usefully. Unless |
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