Interview: Rob Joyce, head of LTE, O2

Mobile operator O2 announced a trial of fourth-generation (4G) Long Term Evolution (LTE) wireless technology, the successor to 3G, in London late last year.

The six-month pilot will upgrade more than 25 existing masts covering 15 square miles in Canary Wharf, Soho, Westminster, South Bank and King's Cross connecting up to 1,000 hand-picked users at peak rates of up to 100Mbit/s.

Computing: How will the London 4G tests differ from the O2 trials already conducted in Slough? What have you learned so far?

Joyce: We did both static and mobile tests in the labs and office, as well as driving around Slough itself. LTE handover is much quicker than on HSDPA+ as it is designed as mobile packet technology, so it is much better at handling mobility and is not challenged by speed, at least at a standard 50km/h.

Any technology struggles to keep the bit rate high when the user is travelling at greater speed, although the next version [of LTE] goes up to 500km/h, with some vendors demonstrating the technology on the Beijing Express in China.

What we did learn in Slough is what the network looks like loaded. We did not see a limit there [on how many users can be simultaneously connected to one cell]. The network equipment vendors say it is 3,000 and we will hopefully get close to testing that limit in the London trial. We think the minimum throughput for the guy standing at the cell edge will be 5Mbit/s, with closer to 100Mbit/s peak rates for those at the centre, but typical throughput will be 30-50Mbit/s. We do not think everybody is going to be streaming 10Mbit/s – people will be hitting their email and browsing the web then dropping off, those closest to the cell will get peak rates.

What sort of applications need the sort of bandwidth 4G can potentially provide?

It’s up to end users really. You would probably have said that 10Mbit/s [of mobile bandwidth] was too much 10 years ago, but if you don’t have 10Mbit/s for an iPhone iOS update today, you would be sitting there for hours. You also need more bandwidth for virtual private networks (VPNs), logging on remotely when somebody is sending a 4-5MB presentation – corporates and over-the-air updates will eat bandwidth. Not everyone might be streaming 10Mbit/s from the BBC iPlayer, but if everyone is streaming 1Mbit/s you need a system to cope with that.

Two examples came out of a trial using a dongle. The most power-hungry apps were cloud-based games – the commands sent from the handset use low bandwidth in the uplink, but you need fast bandwidth to get instructions and download the streaming high-definition images of where the player is positioned in the game.