In the past two years, some new technologies have been introduced in Korea, apparently increasing broadband Internet speeds 3~5 times faster, from 100 Mbps to 300~500 Mbps, instantly. It certainly is fascinating in that such speed improvement was achieved without the hassle of re-cabling construction in apartment buildings. Because 100 Mbps had seemed unbeatable for almost a decade, this sure was a long-awaited good news. So, we will take a moment to see what these technologies are and in what cabling systems they can be employed.   

First, we may want to think about what has brought these technologies into the market.

Korean big 3 operators are currently offering Giga Wi-Fi Service (802.11ac) at hotspots like Starbucks, actually supporting 250~400 Mbps. To achieve this high speed, the operators expanded their wired access networks for hotspots, where Wi-Fi APs are connected, up to 1 Gbps. But for home users, because the maximum broadband speeds are 100 Mbps no matter what service they use (i.e. VDSL2, LAN or FTTH. See Broadband Access Network Architecture in Korea), Giga Wi-Fi service is not yet available for them. In order for these home users to use the service, their home broadband access should be as fast as hundreds of Mbps.

 
There has been concern about the quality of 4K UHD IPTV service, which was just launched by KT and SK Broadband (SKB) in September. According to Benchbee (www.benchbee.co.kr), the most popular Internet speed test site in Korea, the operators' claimed maximum speeds were different from the actual speeds measured. For example, in case of VDSL2 with a claimed maximum speed of 100 Mbps, the actual average speed was 40~70 Mbps (KT). In case of LAN (UTP to the home) and FTTH also with a claimed 100 Mbps, the actual averages were 40~80 Mbps (KT, SKB and LG U+). Because 4K UHD IPTV service requires a broadband of 15~30 Mbps, home users with more than one TV are likely to suffer from unstable quality of service.   

To address this concern, the big 3 have been working to improve speeds of the existing phone line-based (VDSL2) and UTP-based (Cat5) Internet services, from 100 Mbps to 300~500 Mbps for home users living in apartment complexes.

What is common in all the strategies by the big 3 is pretty obvious. They want to do this without re-cabling, that is without replacing the existing cables installed in apartment buildings. (A person at KT familiar with this matter noted, "Technically, cables installed in buildings are owned by the building owners. So, installing new cables certainly means a lot of steps to go through. Discussions should be arranged, consents should be obtained from all the residents, and costs should be shared by them, etc. Given that, GiGA Wire technology gives the operators a lot of benefits in that it allows for fast speed upgrade without having to go through all the steps".)

Let's talk about KT's GiGA Wire first.

Figure 1. KT's GiGA Wire Architecture (Source: KT) 
 

KT's plan is to support a download speed of 300 Mbps or higher through existing phone lines (1 pair). That is, KT aims to provide ultra-high speed Internet service to users living in 20~30 year-old apartment buildings where only phone lines are installed, as well.

GiGA Wire, based on ITU-T G.hn standards (Line modulation: OFDM/DMT, Duplexing: TDD) and enhanced with KT's patented technology, features chips manufactured by Marvell and systems developed by a Korean developer, ubiQuoss (GNT and GAM that function as a modem and DSLAM in VDSL, respectively).

As seen in the performance graph below, Marvell's G.hn demonstrated good performance, 500 Mbps at a distance of 100 m.

It looks like KT deliberately set its target speed a bit low, around 300 Mbps, considering probable speed degradation in actual deteriorated conditions caused by Crosstalk, outdated on-premise cables, etc.

Figure 2. ubiQuoss's G.hn products: Performance at distances (Source: Marvell and ubiQuoss) 

Again, what's noteworthy about KT's GiGA Wire is that the architecture can be applied not only to apartment units with only 1 pair of traditional telephone lines, but also to those with UTP cabling. In case of units with UTP cabling, 1 out of 4 pairs of lines is used for GiGA Wire.

Then, what about SKB and LG U+?