4G is here, bringing superfast data to the palm of our hands, but while we consume more content on our handsets it appears a rather important part of what constitutes a mobile phone has been left behind - voice calls.

When making the decision whether or not to make the switch between 3G and 4G, performance of voice calls probably doesn't come to mind - they'll just keep on working just the same, right? Wrong.

"4G networks at the moment don't actually have a voice service, so the handset has to drop back to either 3G or even 2G to make a call," Phil Sheppard, responsible for Three's 4G technical program, told TechRadar.

"It's an underlying assumption that your voice service will work just as well on 4G as it will on 3G."

Top 4G complaint

Three is the first to admit that it's slow to the 4G game with EE, O2 and Vodafone all launching their superfast services before it, but that extra time has allowed Three to study issues its competitors faced.

"We've seen a lot of the complaints of the other 4G operators have been around voice performance. It's been very slow to move across from 4G to 3G, or it's failed to move across at all," Sheppard revealed.

"We spent the last two months really optimising that and just testing, tweaking and re-modifying things. Technically the handset has to do a bit more work, so it's really important to make it fast and we've now got it down to a point where people really can't tell the difference."

It's not just voice calls which Three has been focussing on however, as data is still clearly the big draw for 4G.

"We want to make sure data performance is really good as well, so what we're doing is we're taking clusters of sites, maybe 20-30, and doing a drive test all the way round each one to ensure the handover between the sites works.

"What you don't want to do is move from one site to the next and the network drops and has to reconnect. We've got it sorted now and it's pretty much 100% in terms of moving in and out of different sites in the areas where the 4G network is live."

There's still a long way to go though, as Three needs to cover all 14,000 sites it has across the UK in its van - something it hopes to have completed by the end of 2015 where it predicts 98% population 4G coverage.

• Have you experienced voice call issues since making the switch to 4G? Let us know in the comment box below, via Facebook, or over on Twitter.

Questions have been raised over Three's 4G roll out, as being the UK's smallest of the big four networks people wonder if it'll be able to cope with the superfast service, with unlimited data tariffs and a free upgrade from 3G to 4G.

TechRadar spoke to Phil Sheppard, responsible for the 4G technical program at Three, who explained that this is not the case.

"We actually have more sites (masts and base stations) than Vodafone and O2. We have 14,000 3G sites in the UK which we'll covert to 4G, and when we last checked Vodafone and O2 were a few thousand behind," explained Sheppard.

"We might only have 10% of mobile customers in the UK, but we account for 43% of all mobile data traffic, so we're used to dealing with large amounts of traffic."

Spectrum speed boost

Three hopes to move 1.5 million customers over to its 4G service in early 2014 as it gradually rolls out to the top 50 biggest towns and cities in the UK, but admits that some users may experience a drop in speed after the initial surge.

"4G speeds will definitely slow [as we add more customers] and that's why we're not really pushing the headlining speed numbers at all.

"We're saying users can expect typical speeds of around 12Mbps, but in practice many people will get a lot more than that. We just don't want to [oversell] speeds," said Sheppard.

Data speeds will pick up as Three adds more spectrum to its existing 1800MHz network. "We have more spectrum coming along in 2015 as a secondary part of our deal with EE, so that will add speed [to the 4G network].

"In the long run, if we get everyone on 4G it's going to be faster on average, as LTE is around 30% more efficient than 3G."

Indoor issues?

Currently Three only has one part of the 1800Mhz spectrum it purchased from EE to launch its 4G service, which could cause issues for rural usage.

"The 1800MHz spectrum used for 4G offers roughly the same coverage as our 3G network which is on 2100MHz," Sheppard told us.

"It's slightly lower so it might be slightly better [at indoor coverage], but at auction we bought some 800MHz, which is better at in-building coverage.

"We not launching with that spectrum, but we will start to deploy it in 2014 and that will add [greater] in-building and rural coverage.

"Currently we struggle with rural areas such as Wales and the South West of England and again the 800MHz will give us that reach and distance."

There's no exact time scale for the rollout, but Three will make quarterly statements throughout 2014 which will detail areas in line for 4G in the following months.

News that Huawei is producing the Ascend P7 should be no surprise, with a leaked document showing the successor to the P6 will have a market-leading selling point.

Alongside a a raft of budget devices like the Ascend G300 and Ascend G510, the Huawei Ascend P6 has helped gain the Chinese firm the title of 'third largest smartphone manufacturer in the world'.

A leaked internal document found by GSM Arena shows a device under the code name 'Sophia', set for release in April 2014. This has led to speculation that this will be the new Huawei Ascend P7.

The most noticeable specification of 'Sophia' is the front facing camera; a whopping 4 times larger than most, an impressive 8MP. This makes it 3MP larger than the front sensor found on the Ascend P6.

8 megapixels, but not 8 cores

Rumours surrounding an octa-core processor handset are limited to the Honor 4 as the Ascend P7 comes toting a HiSilicon Balong 910 1.6GHz quad-core CPU, backed up with 2GB RAM.

Storage wise, the Ascend P7 comes with 16GB of internal space, although there will also be a microSD card slot.

Elsewhere, the P7 comes 4G-enabled, with a 5-inch 1080p screen and 2460mAh battery, as well as being made out of "exquisite materials".. we assume that means diamonds, rubies and Angel Delight.

And let's not forget about the middlingly-interesting Emotion UI, which has been boosted to 2.0 and will run over an 'unspecified' version of Android.

Nokia looks like it wants to cash in on the launch of the powerful Lumia 1520, with a mystery device codenamed RM-964 being spotted on an site monitoring Indian imports.

Nokia Power User spotted the device on Zauba, noting a device with a 5.2-inch screen and a price tag of 34,524 Rupees (around £340/$560/AU$617).

This puts it in line with rumours of a compact Lumia 1520; a quad-core Snapdragon 800 CPU, 20MP camera and Full HD screen akin to the upcoming US-only Lumia 929.

Is Nokia the friend that's never on time?

The Nokia Lumia 1520 was the first Windows Phone 8 handset launched with a quad-core processor and full HD display, putting it right against the Samsung Galaxy Note 3 in terms of size and power.

A smaller-screened quad-core brother would give Lumias something big to shout about, by setting it apart from the dual-core Windows Phone 8 devices that currently occupy the market and pushing it into HTC One, Samsung Galaxy S4 and LG G2 territory.

As the RM-964 is still very much a rumoured device, we're unlikely to see it this year. Launches of the HTC One Two and the 64-bit Samsung Galaxy S5 will give the Nokia a real push. Is Nokia too late to the party?

It'll be interesting to see what happens, but more importantly, what would it be called?

Owners of the Samsung Galaxy S4 mini and Galaxy Ace 3 may be getting a new year treat with news that their handsets could be upgraded to Android 4.4 KitKat in 2014.

A leaked internal document passed to Sam Mobile shows both handsets on a lengthy list of devices apparently due to be tested for the KRT16 update.

Both handsets are considered "mid-range" so there was always a chance of them getting the Android 4.4 update, but the inclusion of the older Galaxy Ace 2, among others, is more of a surprise.

In the past Android handset manufacturers have tended to reserve such updates for higher-end models like the Galaxy S3 and Galaxy S4.

One of the biggest features that Google has been pushing with Android KitKat is its ability to run on devices with as low as 512MB RAM, a move seen to try and reduce the amount of Android segmentation.

KitKat update set to get Fame-ous?

Alongside the S4 mini and Ace 3, the older yet decent Samsung Galaxy S3 mini as well as the Ace 2 and super cheap Galaxy Fame. The update for these Samsung handsets is far from confirmed though, as it's still "under investigation".

Whilst we await the slew of budget KitKat handsets which will hit the market during 2014, support for lower end handsets thus far has been noticeably short. The only budget handset with Android KitKat announced is the Google owned Moto G.

We'll continue to keep our eyes peeled for further information on the Android 4.4 KitKat update, so keep checking back.