Feeds

Clearwire and China Mobile link up for 4G time-div trials

I don't want to pair up, I want to have one after another

Next gen security for virtualised datacentres

As part of the Global TD-LTE Initiative US-based Clearwire and China Mobile are joining forces to test time-divisioned networks in both countries, though we'll likely see the technology in the UK too.

That's because Ofcom, the UK regulator, has earmarked 50MHz of spectrum for the TD variant of 4G telephony, despite the fact that the regulator is supposed to be technology neutral. TD-LTE has a solid technical specification but it still needs lots of interoperability testing if it's going to achieve the economies of scale accorded to its frequency-divisioned contemporary.

When cellular telephony was designed it made sense for the sending and receiving channels to be on separate frequencies, that way the users don't have to shout "over" at the end of every exchange and can even interrupt each other's diatribes with their own interjections.

But giving every user a separate frequency is overly generous, so GSM divides up the band into time slots and expects each user to share a pair of frequencies with seven others nearby. Each user gets an equal share, one time slot per voice call, though a GPRS handset may make use of empty slots for data communications.

Even with CDMA (Code Divisioned Multiple Access) allowing users to share the same frequency at the same time (the base station differentiating between signals with an identifying code) users still transmit on one frequency, and receive on another, ensuring the two don't interfere with each other and keeping things simple.

But using frequency division does require the network operator to own two separate bands, so the regulators regularly licence spectrum in paired blocks suited to frequency divisioning and even refer to companies as owning, for example, 2x25MHz rather than just 50MHz of bandwidth.

WiMAX was the notable exception to the use of frequency-divisioned standards, instead requiring both ends to switch from receive to transmit in perfect harmony. That allows a single frequency so be used for a duplex connection, as well as providing greater flexibility for asynchronous connections (as the time slots for send and receive don't have to be the same size).

WiMAX is all but dead now, but the bands it was using have no convenient pair, which is why Clearwire (who previously deployed WiMAX around the USA) is so keen to explore TD-LTE.

In the UK our 4G auctions are almost entirely paired, but there's a 50MHz chunk at 2.67GHz which lacks a pair and is widely expected to be used for TD-LTE, though the regulator remains officially neutral about technology choices and the licences won't specify what the airwaves are to be filled with.

Who will deploy TD-LTE in the UK we don’t know: the existing operators are more likely to prefer the frequency divisioning they're familiar with, but if China Mobile and Clearwire can demonstrate the technical capabilities of the TD-LTE standard it might increase interest in technology, and the bands needed to support it. ®

Next gen security for virtualised datacentres

More from The Register

next story
6 Obvious Reasons Why Facebook Will Ban This Article (Thank God)
Clampdown on clickbait ... and El Reg is OK with this
So, Apple won't sell cheap kit? Prepare the iOS garden wall WRECKING BALL
It can throw the low cost race if it looks to the cloud
EE fails to apologise for HUGE T-Mobile outage that hit Brits on Friday
Customer: 'Please change your name to occasionally somewhere'
Time Warner Cable customers SQUEAL as US network goes offline
A rude awakening: North Americans greeted with outage drama
We need less U.S. in our WWW – Euro digital chief Steelie Neelie
EC moves to shift status quo at Internet Governance Forum
BT customers face broadband and landline price hikes
Poor punters won't be affected, telecoms giant claims
prev story

Whitepapers

5 things you didn’t know about cloud backup
IT departments are embracing cloud backup, but there’s a lot you need to know before choosing a service provider. Learn all the critical things you need to know.
Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Backing up Big Data
Solving backup challenges and “protect everything from everywhere,” as we move into the era of big data management and the adoption of BYOD.
Consolidation: The Foundation for IT Business Transformation
In this whitepaper learn how effective consolidation of IT and business resources can enable multiple, meaningful business benefits.
High Performance for All
While HPC is not new, it has traditionally been seen as a specialist area – is it now geared up to meet more mainstream requirements?