{"id":30866,"date":"2022-04-28T08:28:18","date_gmt":"2022-04-28T07:28:18","guid":{"rendered":"https:\/\/www.ispreview.co.uk\/?p=30866"},"modified":"2022-04-28T08:37:48","modified_gmt":"2022-04-28T07:37:48","slug":"study-tests-the-theoretical-limits-of-copper-line-broadband","status":"publish","type":"post","link":"https:\/\/www.ispreview.co.uk\/index.php\/2022\/04\/study-tests-the-theoretical-limits-of-copper-line-broadband.html","title":{"rendered":"Study Tests the Theoretical Limits of Copper Line Broadband"},"content":{"rendered":"

New research from the University of Cambridge – supported by BT<\/a> and Huawei – has attempted to identify the theoretical limits of Openreach<\/a>’s standard UK copper broadband lines (unshielded twisted copper pairs), while harnessing up to 12GHz of spectrum. The result is faster speeds are possible, but full fibre is still the future.<\/p>\n

At present many UK consumers still get their broadband using Digital Subscriber Line<\/strong> technologies like ADSL2+ (up to 20-24Mbps) and VDSL2 \/ FTTC (up to 80Mbps), which send electrical signals down a tiny bit of twisted pair (TP) copper wire in order to deliver an internet connection into the home. A few people have also adopted the similar G.fast<\/a> technology (up to 330Mbps).<\/p>\n

One important bit of context here is that all of these use different amounts of spectrum in order to carry their data signals. For example, in the UK ADSL2+ utilises up to 2.2MHz, while VDSL2 uses up to 17MHz and G.fast<\/a> goes up to 106MHz. More modern experimental technologies, such as MGFast<\/strong><\/a>, can even harness up to 848MHz<\/strong> for targets data rates up to 10Gbps.<\/p>\n

At this point we could also touch on the theoretical Terabit DSL<\/strong><\/a> (TDSL) technology, but that adopts the radically different approach of using an existing copper wire as a mere “guide<\/em>” (waveguide<\/strong>) to help direct a wireless broadband signal in the 100GHz+ millimeter Wave (mmW) band. We’ll leave that out of this one as it would confuse matters.<\/p>\n

The big problem with these copper line technologies – particularly the fastest ones – is that the more spectrum frequency you harness, the greater the challenge of mitigating interference over distance (signal degradation \/ errors etc.). In the real-world, we experience this as a loss of speed or line stability.<\/p>\n

For example, an old ADSL2+ line can theoretically deliver speeds of c.20Mbps up to distances of around 1.5km from the exchange, but at 5km+ you’ll be down to 1-2Mbps territory. Similarly, G.fast delivers its best speeds for those within c.200-300 metres of a PCP Street Cabinet, but performance rapidly tails off.<\/p>\n

You could, in theory, get 1Gbps+ speeds from G.fast at 212MHz (not deployed in the UK), but you’d need masses of small nodes – all within a few tens of metres of each house – and that’s a very costly and complex build, with issues for long-term maintenance.<\/p>\n

The New Copper Limits Study<\/strong><\/span><\/h3>\n

The new study<\/strong><\/a>, which if you’re comfortable with the physics makes for a fascinating read, is designed with a view to improving “achievable data rates over the copper infrastructure so that the bottlenecks over the last mile can be successfully avoided while satisfying the future data demands<\/em>.”<\/p>\n

Study Abstract<\/strong><\/p>\n

This paper explores the behaviour of the ubiquitous twisted pairs at high frequencies and wideband excitation of twisted pairs up to 12 GHz. Higher carrier frequencies on twisted pairs can enable the data rates required by the future communication networks; hence, the existing copper infrastructure can be utilised on the last mile complementing the fibre networks.<\/p>\n

In this paper, we show a fundamental limit on the operating frequency of twisted pairs beyond which twisted pairs start to radiate and behave like an antenna. To validate our theoretical derivations through measurements, we designed a microstrip balun to excite the differential mode on the twisted pairs.<\/p>\n

At the end, we demonstrate that the standard twisted pairs used in the UK can be used up to 5 GHz carrier frequency without any radiation effect and this upper-bound can be moved to higher frequencies by decreasing the twist lengths.<\/p><\/blockquote>\n

In conclusion, the paper suggests that its results and design guidelines will help scientists and engineers to better understand the wave propagation on TPs and “enable them to design wideband communication systems operating at higher carrier frequencies<\/em>.” It’s a useful bit of knowledge to have, albeit not one that will change the current direction of travel, just as G.fast and MGfast failed to do before. Signal degradation at 5GHz would be.. fun.<\/p>\n

NOTE:<\/strong> The research suggests that performance could also be improved by “decreasing the twist lengths<\/em>” on copper lines, which may be true, but that has no benefit to existing cables in the ground.<\/div>\n

By now most incumbents in the world, including Openreach<\/a>, have realised – through a mix of political, technological and competitive pressures – that it makes more sense to spend big on deploying full fibre (FTTP<\/a>) broadband than it does to continue trying to squeeze extra speed out of ancient copper lines, with all the caveats that invariably entails. Any new copper technology would also take years to develop.<\/p>\n

Meanwhile, optical fibres can already handle multi-Terabit speeds and without the hassles of copper, but it’ll be years before such speeds become viable to homes – yet one day, they will. Lest we forget that Openreach also have no desire to run the old copper network side-by-side with Fibre-to-the-Premises<\/strong> (FTTP<\/a>), thus they’re already working toward its eventual withdrawal.<\/p>\n","protected":false},"excerpt":{"rendered":"

New research from the University of Cambridge – supported by BT and Huawei – has attempted to identify the theoretical limits of Openreach’s standard UK copper broadband lines (unshielded twisted copper pairs), while harnessing up to 12GHz of spectrum. The result is faster speeds are possible, but full fibre is still the future.<\/p>\n","protected":false},"author":1,"featured_media":5193,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"ngg_post_thumbnail":0,"footnotes":""},"categories":[1],"tags":[474,55,56,417,69,477,482],"class_list":["post-30866","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-uk_isp_news","tag-bt","tag-fttc","tag-fttp","tag-g-fast","tag-bt-openreach","tag-science","tag-xg-fast"],"share_on_mastodon":{"url":"","error":""},"yoast_head":"\nStudy Tests the Theoretical Limits of Copper Line Broadband - ISPreview UK<\/title>\n<meta name=\"description\" content=\"New research from the University of Cambridge - supported by BT and Huawei - has attempted to identify the theoretical limits of Openreach's standard UK\" \/>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.ispreview.co.uk\/index.php\/2022\/04\/study-tests-the-theoretical-limits-of-copper-line-broadband.html\" \/>\n<meta property=\"og:locale\" content=\"en_GB\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Study Tests the Theoretical Limits of Copper Line Broadband - 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