Faster 5G speeds helped by 4G spectrum bandwidth in South Korea

In our previous insight, we observed that our users in Germany, Italy and the UK experienced significantly faster 5G average download speeds when they were also connected to additional amounts of 4G spectrum, through older 4G technology. To explore this topic further, Opensignal looked at South Korea’s mobile market, known for its advanced 5G deployments. Even with South Korea’s operators using relatively large amounts of new mid-band 5G spectrum, our users saw significantly higher average 5G download speeds when additional 4G spectrum was used. 

We examined users’ 5G download speeds when they were connected to either 80MHz or 100Mhz of 5G spectrum and compared the resulting experience when different quantities of 4G spectrum were also connected. This simultaneous use of the 4G and 5G spectrum is a characteristic of 5G non-standalone access (NSA) where both technologies must work together. NSA 5G is the most common way that operators have launched 5G worldwide.

Interestingly, additional 4G spectrum bandwidth capacity helped to offset the initial difference in average 5G download speeds that we saw between a smaller block of 80 MHz spectrum in the 3.5 GHz band used by LG U+ and larger blocks of 100 MHz in the same band used by KT and SK telecom. In the biggest South Korean cities, our users on LG U+’s network also saw fast 5G download speeds, comparable with SK telecom and faster than in the case of KT. By global standards, all three Korean operators have deployed a large amount of new 5G spectrum — in many markets operators have launched with just 40MHz or 50MHz of new mid-band spectrum.

With 5-20 MHz of supporting 4G spectrum, LG U+ subscribers achieved average 5G download speeds of 201.6 Mbps, as seen by our users. Compared to this, our users on KT and SK telecom’s networks saw average 5G download speeds 78.1% and 102.4% faster, respectively — clocking at 359.0 and 408.0 Mbps. 

However, using an additional carrier of 20 MHz (25-40 MHz of supporting 4G spectrum) — pushed up the average 5G download speeds experienced by our LG U+ users by 90.2%, to 383.4 Mbps. This was faster than what our users on KT’s networks saw with the same amount of 4G supporting spectrum and a larger block of 5G spectrum (350.6 Mbps) — but still lower than what our SK telecom users experienced (452.5 Mbps). Another 20 MHz of supporting 4G spectrum (45-60 MHz) boosted the throughput seen by our LG U+ users by 26.2%, up to 483.9 Mbps. That was 2.8% faster than what our users on SK telecom experienced (470.7 Mbps), using the same amount of supporting 4G spectrum.

In addition to a national impact from 4G, our research showed impressive results for LG U+ in terms of the average 5G download speeds observed by our users in South Korea’s six largest cities, despite it having access to a smaller block of 5G spectrum than its rivals. When looking at combined results from Seoul, Busan, Incheon, Daegu, Daejeon and Gwangju with 25-40 MHz of supporting 4G spectrum, LG U+ and SK telecom statistically tied — both operators achieved 403.6 and 411.6 Mbps respectively. This was approximately 23.0-25.4% faster than their competitor KT. 

With an additional carrier used and bringing the supporting 4G spectrum to 45-60 MHz, LG U+ pulled ahead of its competitors, as its average 5G download speeds saw an increase of 34%. By contrast, our users on SK telecom and KT’s networks saw slight and statistically insignificant increases of observed average 5G download speeds, with the same amount of supporting 4G spectrum used.

Looking at 5G download speeds in Seoul, we saw our users on LG U+’s network enjoyed the highest average 5G download speed, clocking at 515.2 Mbps. This was 8.8% faster than those on SK telecom’s network and 63% than on KT’s network despite LG U+ using 80MHz of 5G spectrum compared with 100 MHz by SK telecom and KT in the 3.5 GHz band. This difference is likely due to the impact of the 4G spectrum that is simultaneously connected alongside this 5G spectrum (see the 2nd chart above). In Incheon, LG U+ and SK telecom were in a statistical tie and our users on those operators reached speeds nearly 3.5 times faster than our users on KT’s network.

Even in a global 5G country leader, 4G continues to be important for the 5G experience

Our analysis shows that strong 4G network foundations still remain essential for 5G deployment in its early stages. 5G-capable spectrum in the 3.5 GHz band is unevenly distributed among South Korean operators. South Korea’s Ministry of Science and ICT (MSIT) completed a spectrum tender in June 2018, during which KT and SK telecom won 100 MHz each, while LG U+ secured a smaller block of 80 MHz in the 3.5 GHz band. Even though a continuous block of 80 MHz in the 3.GHz band is a lot more than that currently held by operators in some European markets, our users on LG U+’s network initially observed significantly lower 5G download speeds than those on KT and SK telecom’s networks at a national level. 

4G continues to boost the 5G experience even for a market like South Korea, hailed as one of the 5G frontrunners. All three Korean mobile operators — KT, LG U+ and SK telecom, shared the 5G Games Experience award along with four operators from other countries in our latest 5G Global Mobile Network Experience Awards 2021 report, while they were also recognized as 5G Global Leaders in all the other Global categories.

Part of the reason for the 5G success story of Korea’s operators is their use of 4G spectrum and having an excellent 4G network that helps to boost 5G download speeds. This proved especially true in the case of LG U+, both at a national level and in the big cities, like Seoul. Despite holding a smaller block of 5G spectrum than its competitors, the operator managed to make up for the difference with more supporting 4G spectrum applied. As a result, our users on this operator’s network managed to see speeds similar to — or even higher than — KT and SK telecom.