Traditional RF unsustainable for multi-band LTE, says Nujira CEO

Tim Haynes

Tim Haynes

2013 saw 4G networks continue to rollout worldwide, with 126 million LTE subscribers on more than 200 commercially launched networks, using 22 different frequency bands, writes Tim Haynes, CEO of Nujira.

We even finally saw LTE launch in some parts of the UK, though rather than lament the late arrival of 4G, perhaps we should congratulate ourselves on the state of our 3G network.

2013 also saw widespread recognition for the need to innovate in the RF front end, with hundreds of engineers in dozens of companies worldwide working to develop and integrate the latest technologies.

The smartphone industry has realised that traditional RF approaches are unsustainable for multi-band LTE smartphones, and are rapidly adopting Envelope Tracking (ET), antenna tuning, and multi-mode, multi-band PAs to improve the performance of the RF Front End.

This subsystem was front of mind throughout the year for handset chipset vendors, OEMs and operators, as key metrics such as battery life, antenna performance, network coverage and thermal management are all dependent on the performance of the RF front end.

All major chipset providers have now made provisions for ET in their latest generation of mobile transceivers, and we’re working with most of them to enable ET on their reference designs. 2013 also saw the publication of the eTrak interface specification from the MIPI Alliance, with Nujira as a key contributor.

Qualcomm’s announcement of the “RF360” at MWC in February – a module level solution including an ETIC and CMOS PAs – sent waves through the GaAs PA vendor ecosystem, although it has still not shipped in any products. We have been saying for a while that the combination of ET with CMOS PAs is a disruptive one, and RF360 could well be the first step in that journey.

2013 saw the launch of the first smartphone to employ Envelope Tracking, Samsung’s Galaxy Note 3, which made use of the Qualcomm modem chipset and ET IC, coupled with traditional GaAs Power Amplifiers.

While not achieving the highest ET performance, it was nevertheless a key milestone for ET, and important validation of the market. Samsung’s Note 3 was closely followed by LG’s Nexus 5, which uses the same Qualcomm chipset.

This highlights perhaps the only negative point: despite massive efforts from almost 20 chipset vendors worldwide, Qualcomm remained the only supplier to ship significant numbers of LTE chipsets in 2013. This monoculture is damaging for the industry, and we expect to see significant erosion of this share in 2014 as other chipset vendors catch up.

As with many new innovations, the development bottleneck has now shifted from hardware to software, with firmware engineers worldwide busily adapting their power control and calibration routines to take full advantage of ET.

Much like the move from carburettors to fuel injection 30 years ago, ET transforms the RF PA into a software-defined component, where performance and fuel economy are controlled by engine management software, rather than hardware tuning and tweaking.

In 2014, the mobile sector will be firmly focused on adopting these new RF front-end technologies, such as antenna tuning and ET, and we predict that ET will reach a 100% attach rate on smartphone reference designs by the end of the year.

One of the key issues for 2014 will be bandwidth, which affects both networks and handset manufacturers. The rapid deployment of TD-LTE, driven particularly by rollout in China, will drive up instantaneous transmission bandwidth and output power by a factor of 5 compared to FD-LTE.

This will push the handset industry towards higher performing RF front ends, but will also improve network capacity. Handset OEMs will realize that the best way to extend battery life is to turn the transmit power up, not down, so perhaps 2014 will see the “half power handsets” of today replaced by terminals which deliver a true 4G experience.

So while the battle to bring ET into the commercial market was won in 2013, 2014 will see the technology debate move onto the specifics, looking for ways to fine-tune the technology and maximise its benefits.

At Nujira, we’re working on some exciting next-generation products and architectures which we’re confident will maintain our position as the world leader in Envelope Tracking technology.

Tim Haynes, CEO Nujira


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