• Technique offers full stream broadband performance
• In theory will let users dynamically adjust the asymmetry of their G.fast connections  

When Digital Subscriber Line (DSL) was first devised, way back in the early 1990s, there was quite a bit of industry contention about upstream/downstream ratios (or the symetric/asymetric question).  

Essentially, a twisted copper pair only had so much usable spectrum for the technology of the day. Clever processing kept doubling speeds and doubling them again, so the raw speed crept up, but in simple terms there’s always a finite amount of bandwidth in the pipe which must therefore be shared. If you want a fast downstream channel you get a correspondingly slow upstream channel.

There were reasons, of course, to keep things this way. If incumbents pulled a symmetric service out of the hat (same data up as down) using DSL, then customers could trade in their old ‘legacy’ symmetric services and use the new DSL for a fraction the price - that would never do.

Then again, if users are primarily downloading films and other sorts of data-heavy content then asymmetry makes sense - until we start uploading as much or more than ‘we’  (us internet users) download, which many traffic reports point out is already starting to happen as photos and user content from smartphones builds.

ADTRAN has just announced (at Broadband World Forum in London) what it claims is a new capability for G.fast deployments - Dynamic Time Allocation. This, it claims, will allow users to dynamically adjust the asymmetry of their G.fast connections depending on their application needs.

ADTRAN has been demonstrating this innovation to operators globally for low crosstalk G.fast environments, on the basis that it offers an alternative to installing Cat 6, Cat5e or fibre optic cable to provide symmetric Gigabit data rates.

According to ADTRAN, “DTA disrupts the concept of Time Division Duplex (TDD) used by G.fast and other broadband access technologies which, until now, have been based on the “set-and-forget” configuration of uplink and downlink ratios (either symmetric or some degree of asymmetric) at the G.fast distribution point unit (DPU).

“DTA responds to user activity in the order of milliseconds and offers ‘full stream broadband performance’ while giving the perception of a full capacity symmetric broadband experience. This approach achieves up to double the speed of an equivalent symmetric G.fast broadband service delivered without DTA. In instances where simultaneous upstream and downstream transmission is required, DTA responds as appropriate.“