Vodafone UK Turns Mobile Network Guns on BT/EE

Iain Morris

Learning from SoftBank
The recent network transformation owes much to the leadership of Prigg, who joined Vodafone about two years ago from Japan's SoftBank Corp.

Prigg spent time working with 256-QAM and more advanced MIMO technologies during his stint in Japan, and says he was eager to bring his experiences back to the UK on joining Vodafone.

Much of the investment is being driven through Project Beacon, a network-sharing venture with long-time infrastructure partner Telefónica UK, which trades in the UK under the O2 brand.

The basic goal of the network "modernization" is to equip all sites with single radio access network (or S-RAN) technology, which allows Vodafone and O2 to support more than one access technology on the same platform.

About 400 sites are being modernized every month, says Prigg, and around 79% of all sites are now equipped with S-RAN technology. The aim is to complete the overhaul in the next six to nine months.

Vodafone is using its 800MHz spectrum holdings to support 4G services, its 900MHz airwaves with 2G and its 2100MHz frequencies for both 3G and 4G services.

Main Spectrum Holdings of UK Network Operators
Source: Ofcom, operators, Light Reading.
Source: Ofcom, operators, Light Reading.

It is using a 10MHz channel in the 800MHz band to provide wide-area 4G coverage and reckons this gives it a big advantage over BT/EE and Hutchison-owned 3, the smallest of the country's four mobile network operators. "BT/EE and 3 can't really do that because they have only a thin layer of 800MHz spectrum," says Prigg. "That has implications for how much traffic you can carry and we can therefore use it as a primary capacity layer."

The laws of physics mean that signals travel much further in lower frequency bands than in higher ones. The drawback is that lower ranges contain less spectrum and therefore cannot easily support the very highest-speed services.

In more densely populated areas, where traffic demands are greater, Vodafone has been getting around that problem by combining its 800MHz with its 2100MHz spectrum in a two-way carrier aggregation.

And it can go one step further where it needs even more capacity and bring its 2.6GHz spectrum into play in a three-way carrier aggregation. That is exactly what it has been doing at the 280 London sites where it has also deployed 4x4 MIMO and 256-QAM.

As a form of active network sharing, the Beacon initiative means that some network improvements become available to both Vodafone and O2, raising concerns about competition. But Prigg says the platform gives the network partners scope for differentiation, especially on the spectrum front.

Vodafone, for instance, is keen on bringing into use a 20MHz slice of 1400MHz spectrum it bought from US chipmaker Qualcomm Inc. (Nasdaq: QCOM) about two years ago. This downlink-only spectrum could be used in conjunction with 800MHz on the uplink and aggregated with other channels for superfast connectivity. "When you start to think about that, you are basically nudging on gigabit speeds with the right terminals," says Prigg. (See Qualcomm Looks to Sell UK Spectrum Holdings – Report .)

Massive MIMO also holds plenty of promise from a bandwidth perspective and could even help to address the coverage limitations of very high spectrum bands in a 5G setting.

It would do that through an advanced technique called beamforming that allows the antennas to "steer" spectrum to individual users. "It is important because you are reusing the limited amount of spectrum you have over and over again," says Prigg.

Due to the costliness of equipment, massive MIMO is unlikely ever to blanket a national territory, but its beamforming characteristics might in future help Vodafone to improve 5G signal propagation in cities where it is relying on much higher frequency ranges to serve customers.

"As you go higher you won't get the overlapping coverage you need for contiguous data usage and so you will have to start thinking about advanced technologies to bridge the gap," says Prigg.

— Iain Morris, Circle me on Google+ Follow me on TwitterVisit my LinkedIn profile, News Editor, Light Reading

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