Cambridge Mobile Application Group: What can app developers do with LTE-Advanced?

On Tuesday I went to Cambridge Mobile Application Group’s January meetup where Chandru Mullaparthi, Head of Service Development at EE, was talking to us about upcoming developments in mobile network infrastructure and the rollout of LTE-Advanced, which builds on the existing LTE (Long Term Evolution) standard and services.

The stats for LTE-Advanced are pretty impressive: the aim is to offer 1Gbps download, and 500Mbps upload. In a recent test in London’s Tech City EE were able to achieve 294Mbps download speed on a “category 6″ device. More on what “category 6″ means in a moment although, suffice to say, for now there are no such devices available on the market.

His question for us, as mobile developers, was, “What would YOU do with 300Mbps bandwidth?” Specifically, what kind of apps would we build? How would we use that much bandwidth?

Whilst some joker commented that “we’d waste it” and I have no doubt that badly written apps will do exactly that, it does raise many exciting possibilities.

The obvious candidate for high bandwidth is video, but it’s not just downloading video: that 150Mbps upload speed means you can also upload video in realtime. In fact, those of you already used to 4G service may have noticed a much better Skype experience than you get over home broadband for precisely this reason. Even the crappiest ADSL connection usually has enough download bandwidth to stream video. But upload? Not so much. Still, the current 4G LTE services offer speeds of up to 100Mbps download and 50Mbps upload with LTE-8, more than sufficient for a video calls, at least until you run into your bandwidth cap.

But I wonder if we might see new classes of apps emerging where media is being streamed effectively peer to peer in real time. Social and crowdsourced video could be interesting for travel (exactly how bad is that queue on the M4?), event management, and gaming – urban team nerf assassins with real-time video, anyone? (I suppose it might also increase the risk of being arrested for antisocial and disruptive behaviour, so use it responsibly. :) )

On the downside it also raises the possibility of even more intrusive and disruptive forms of advertising but I suppose we’re all used to that by now, and will find ways to deal with it. I’m much more interested in the positive and creative uses.

All of this led to a lot of questions from the group and I felt a bit bad for Chandru because I’m pretty sure he wasn’t able to get through his whole talk. That being said he was very happy to take questions, and very open about answering them, so it was a good session.

Before I get into that, it might be worth a look at what LTE-Advanced offers.

LTE-Advanced Overview

LTE-Advanced is focuses improvements on 7 different areas:

  • Peak data rate
  • Latency
  • Spectrum efficiency
  • Spectrum flexibility
  • Cell edge user throughput
  • VoIP capability
  • Mobility

I’ve already talked about the peaked data rates, but lets look at some of these other areas.

Latency

The aim is to reduce the idle to connected transition to 50ms (this is the standard and it looks like EE are already beating this in their tests), which is significantly faster than 3G, and even faster than the current 4G LTE.

Since the roundtripping time is reduced you should then feel as if the device is connected via a hard line when using apps.

Spectrum Efficiency & Flexibility

I mentioned “category 6″ devices, which aren’t currently available earlier. Current devices tend to be categories 3 and 4. One of the things this refers to is the number of antennae they contain. Currently two is quite common. Category 10 devices may have eight antennae, although it’s difficult to see how these could be made small enough to fit in your pocket.

The number of antennae is one of the factors that enables devices to offer such high speeds: they can use multiple antennae simultaneously to transmit and receive over multiple bands in the frequency spectrum. This is obviously complex but that complexity is hidden at the application level where you simply see one high-speed connection.

Cell-Edge User Throughput

This is somewhat related to the above. With LTE-Advanced it’s possible to transmit and receive data through multiple cells simultaneously. This means that, unlike 3G, where you see a significant drop-off in performance at the edges of cells, service quality and performance is maintained to a much higher level at cell edges.

VoIP Capability

Enabled by increased bandwidth plus the capability to request guaranteed bandwidth.

Mobility

Improvements to mobility will enable handovers between cells at up to 350kmh and, for some frequencies, up to 500kmh – useful when travelling on high speed trains. LTE-Advanced also supports seamless handover between cellular and WiFi networks. The latter should be possible with devices available today but will require upgrades to software both on handsets and on core network infrastructure.

All of this seems great, and should mean that a lot of the problems commonly associated with mobile apps – high latency, flaky connectivity, poor perceived performance – may disappear, or at least be significantly reduced. Mind you, the group were quick to raise potential issues, which are worth looking at…

Issues for App Developers

What about bandwidth caps?

300Mbps is all very well but with bandwidth caps like we have today what’s the point? 5GB isn’t going to last you very long.

I can personally attest to this. Back in August I was in Seattle and Redmond with my friend Kevin and we were using his phone with a 2GB AT&T SIM that we managed to rip through in about four days with the following use: downloading emails (both his and mine with WiFi tethering), some light web usage, maps (mostly offline with Nokia maps), and one 20-30 minute Skype video call.

Bandwidth caps are either going to have to go, or be very significantly increased. People in general are annoyed by them so the former would seem like the way forward. All of this leads to another question…

Will the core network be able to cope with that amount of data flying back and forth?

Currently? No.

Chandru said there’s an arms race between what basestations and handsets support over the radio network, and what the network backhaul can handle, and that they are having to continually upgrade it to keep up.

And contention?

Your device might be able to support these higher speeds, but how many devices running bandwidth-hungry apps can the base-stations support? Will we end up in the same situation as we have with DSL, particularly in rural areas – i.e., nominally 8Mbps connections that at peak times can perform worse than the 56k dial-up connections of 15 years ago?

This is very frustrating for users, and the problem will be made worse if apps are developed on the assumption that the network connection will be fast.

The issue really comes down to the cell density in a given area.

Most areas are covered by macro-cells. These are large cells that provide coverage over a wide area. They tend to be supported by base stations with transmitters placed as high as possible, with good line of site over the widest possible area. However, they can only support a limited number of users and therefore tend to be used as a backup in more populated areas.

Urban, and more populated areas in general, tend to be primarily supported by much smaller cells, with therefore many more base-stations covering a given area. These allow large numbers of users to be supported in areas of higher population density.

If there are a sufficient number of smaller cells then contention should mostly become a non-issue, although I would expect that for large gatherings (concerts, New Year celebrations, etc.) we’ll continue to see the kind of network flakiness we still sometimes experience. This does also depend on what people are using their devices for.

What about pricing?

The rollout in London’s Tech City is currently non-commercial. If you’ve got a device that supports LTE-A, you can go ahead and use it for free at the moment. This is likely to change, and there will be a price premium on LTE-A services, as there is for 4G currently. As with all things mobile you should expect to see that disappear in a couple of years.

Will this supercede fixed line broadband?

Fibre is fast, at least compared to what many at least in the UK are currently used to, but it’s only a third as fast as LTE-A, so why bother with the cost of installing the infrastructure?

In many developing countries, India being one example, this is exactly what’s happening: they’re leapfrogging fixed line infrastructure in favour of cellular because it’s much cheaper to install. No digging up streets, laying cables, etc.

On the other hand fixed line can have certain advantages:

  • It’s more secure,
  • In theory at least it’s harder (or perhaps just more risky) to take the network down whereas, with the right equipment, I can easily disrupt cellular networks in my local area,
  • It’s possible to get guaranteed bandwidth, at least with a leased line, which is why they’re popular with businesses although still far too pricey to be within range of any but the absolute wealthiest of consumers (there are mechanisms for requesting guaranteed bandwidth over LTE-A but, of course, if too many users need it simultaneously this will degrade – I’m not sure how gracefully).

Fixed line isn’t likely to go away completely, even in developing countries, but in 5-10 years time for a lot of people it will no longer be the default option.

What effect does LTE-A have on battery life?

Chandru commented that when EE ran their LTE-Advanced test the device was plugged into the mains and became quite warm, so it sounds like it’s probably quite power-hungry.

One of the other attendees pointed out that Wireless AC already supports LTE-Advanced speeds but without significant battery drain, so it may not be that bad. But then wireless access tends to be over much smaller distances and requires lower transmission power, so I’d say this doesn’t sound like a great benchmark.

What will 5G offer?

The notable item Chandru mentioned here was consistency of bandwidth: the aim is to offer 1Gbps across devices. In the meantime therefore it does seem like we may not be able to assume too much in the way of bandwidth, and there were a lot of questions around how you detect what type and speed of connection you have. This is largely hidden by iOS at least, although it’s possible to tell whether you’re on a WiFi or cellular network. Android’s APIs are a little more accommodating and offer more detail, if you need it.

That’s it for now. Thanks to Chandru, for speaking, Tony Short, for organising, and Red Gate, for sponsoring the event.

One thought on “Cambridge Mobile Application Group: What can app developers do with LTE-Advanced?

  1. Pingback: Web performance: how fast does your website *need* to be?

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