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Comparison of Commercial 5G Network Architecture: KT vs. SK Telecom
October 11, 2019 | By Harrison J. Son (son@netmanias.com)
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In this blog, we analyze the current state of commercial 5G network construction of KT and SK Telecom, and the difference of 5G value pursued.


First Release: 2019.03.29  

Last Updated: 2019.10.11



1. End-to-End 5G Network Architecture


The 5G network can be functionally divided into 5G Core network and 5G RAN, and can be divided into Central Cloud and Edge Cloud which are geographically deployed in the mobile operator's network.



SK Telecom



KT 5G Network Architecture:

5G Core, 5G RAN and 5G Edge Cloud

(Last updated: 2019.06.12)

pdf file download



SK Telecom 5G Network Architecture:

5G Core, 5G RAN and 5G Edge Cloud (MEC)

(Last updated: 2019.10.11)

pdf file download



2. Location of Edge Clouds (Edge Cloud has GW-U/UPF, CU and MEC)


KT (8 sites)

SK Telecom (2 sites)

8 Cities: Guro, Hyehwa, Daejeon, Daegu, Gwangju, Busan, Jeju and Wonju

2 Cities: Sungsoo, Dusan







The 5G Edge is one of the biggest features of the 5G network that was not in the 4G era. The services that 5G pursues can be summarized as "providing ultra-low latency, large capacity like wired optical cable" to the terminal. The 5G edge is a network infrastructure that realizes this, brings new revenue generation to telecom operators, and provides users with a new experience different from existing 4G.


KT said on March 6 that it has built an edge cloud in eight central offices nationwide (Guro, Hyehwa, Daejeon, Daegu, Gwangju, Busan, Jeju and Wonju). In the edge cloud, 5G Core UP (GW-U / UPF) and 5G RAN CU are located, and there are also Mobile Edge Computing (MEC) servers that perform data processing for 5G devices in the vicinity of the devices. The Central Cloud is located in Guro, etc., and the 5G Core CP (GW-C / UDR, UDM, PCF, SMF, AMF, etc.) is located.


SK Telecom also announced that it has built Edge Cloud / MEC on March 14th. However, it did not disclose how many were built. However, from the above picture (Source: KT, Mar. 23, 2019), SK Telecom's edge cloud is Sungsoo in Seoul and Dusan in Daejeon.


In the 5G era, the edge cloud that is built in the operator network to provide ultra-low latency and high-capacity services efficiently (terminating the GTP mobile session at a close distance from the user and providing IP services such as AR / VR, V2X and Smart X / Y /Z ) and KT is now the most advanced in Korea.



3. Value of 5G (Which is Better?: 5G alone or 5G+LTE)



SK Telecom


5G alone

KT emphasizes: Latency (10ms)



5G+LTE Aggregation

SK Telecom insists: Speed (2.7Gbps)






At a value of 5G, KT emphasizes ultra low latency (ms) and SK Telecom emphasizes speed (bps).


KT's '5G alone' (not aggregated with LTE) is slower than the '5G + LTE aggregation' in bps. However, KT emphasizes that 5G alone greatly reduces the response time of applications. This is because 5G has low latency in the air section between the UE and the base station (ultra-low delay characteristics of 5G = 1ms frame size 1ms and LTE frame size 10ms) and KT has built an edge cloud in 8 cities.


KT, on the other hand, argues that latency of 5G + LTE aggregation is downgraded to latency of LTE because data is transmitted through two paths.


5G alone would be advantageous for applications such as web surfing and VR, and 5G + LTE aggregation would be advantageous for applications such as downloading large files.



4. 5G Core


The core network architecture of 4G and 5G (NSA: None-Standalone, SA: Standalone) is shown below. Currently, both companies have commercialized the 5G NSA, and 5G SA is expected to be commercialized next year. The 5G NSA core network can be 2 or 3 in the figure below. In case of KT, it corresponds to 3. SK Telecom and LG U+ correspond to 2.




SK Telecom

5G NSA Commercialization (2018.12)

5G SA will be commercialized in 2020

5G NSA Commercialization (2018.12)

5G SA will be commercialized in 2020

Samsung, Cisco Samsung, etc.



Commercialized version in 2019

is shown on the left (GW-C, GW-U)


2018.11.14: KT, CUPS 기술의 5G 초저지연 코어 장비 구축완료





Source: SK Telecom, 2019.03



5G NSA option of three mobile operators in Korea is 5G NSA Option 3 (eNB is Mobility Anchor) that uses EPC core and provides dual connectivity between eNB and gNB. Option 3 is divided into 3 / 3a / 3x, and all Korean operators adopted Option 3x.




5. 5G RAN (Cell Site)



SK Telecom

3.5GHZ, 100MHz, 32TRX

3.5GHz, 100MHz, 32TRX

Samsung, Ericsson, Nokia Samsung, Ericsson, Nokia





4G: Seperated Antenna/RU

5G: Inegrated Antenna /RU






• In Pyeongchang Olympic 5G network, DU has RLC, MAC, PHY and RU has only RF. However, in the 5G commercial network, PHY layer is separated into H-PHY and L-PHY, and L-PHY is deployed in RU.

• 3.5GHz (100MHz): Same as SK Telecom

• 28GHz (800MHz): expected to be the same as SK Telecom






• 3.5 GHz (100 MHz): CU and DU are located in the central office. RU is located at the cell site, and the interface between DU and RU is eCPRI


• 28 GHz (800 MHz): CU is located in the Central office. DU and RU are located at the cell site as one body, the interface between CU and DU is F1




  Source: SK Telecom, 2018.09


  Source: SK Telecom, 2019.03



Both companies have commercialized 3.5GHz 5G base stations in December 2018 and 28GHz base stations are not yet commercialized.


The 5G RAN (gNB) consists of CU (RRC, PDCP), DU (RLC, MAC, PHY-High) and RU (PHY-Low, RF). KT and SKT placed CU and DU in its own central office, not cell site. The RU is located at the cell site, DU and RU are connected through the fronthaul network, and the interface is eCPRI.




6. 5G Fronthaul


KT's his fronthaul network was built by Passive WDM equipment with a point-to-point topology and is called '5G MUX' in KT terminology.

SK Telecom's fronthaul network is a ring topology, and COT in Korea is an active WDM device and Cell site's RN is a passive WDM device. This is called '5G-PON' in SK Telecom terminology.



SK Telecom


5G MUX (Passive WDM, P2P, eCPRI 25Gbps)


Source: KT


5G-PON (Semi-Active, Ring, eCPRI 10Gbps)


Source: SK Telecom


Solid, etc.

HFR, Solid, Coweaver




7. 5G B2B Service (Vertical Market, On-Site Private 5G)


Up to 4G, services and mobile networks have been designed for mobile phones used by indinidual users (B2C).

The technical characteristics of 5G, which distinguishes it from 4G technology, are ultra high capacity, ultra-low delay, and massive connectivity.

The opportunity for 5G is to penetrate existing manufacturers that have existed for a long time using these 5G's features.

In this direction, Korea is drawing a new business model. The chart below shows how the Korean operators are making these efforts.





Source: KT Seminar, 2019.09.26


   SK Telecom



Source: SK Telecom Press Conference, 2019.08




SK Telecom


5G Smart Factory (2019.03.07)



5G Smart Factory (2019.03.06)



5G AR Glass (2019.02.25)





5G Smart Office (2019.02.18)



5G Smart Factory (2018.12.11)







Dave Burstein 2019-04-24 11:36:13

Harrison - Exceptional work. I haven't seen anything close to this quality in English. Always happy to exchange ideas. I've reported broadband from New York since 1999, including wirelessone.news. I'm writing a book on 5G and am on the ITU 2030 Focus Group for 6G. Dave

Sina Ebrahimi 2019-10-02 08:04:37

Thanks for sharing this great vision

Sina Ebrahimi 2019-10-02 08:34:20

I have a question about section 4:
Will SK Telecom use CUPS in the Core Network or not in the transition!?
Is the CUPS transition necessary for the migration from supporting 5G NSA devices to 5G SA?
The two orange arrows in the middle of the picture (which shows the separation of CP/UP of the SGW & PGW) provide some ambiguity here. 
​I would be very pleased if you could provide an answer

Sina Ebrahimi 2019-10-02 08:34:48

Again, thank you so much for this generous post!

Adil 2020-01-09 16:41:27

Good Summary; thanks. I have a question abour the NR Frame configuration used by the Korean operators; specifically the DL/UL configuration; which configuration is finalized when using ENDC


CeliTech Inc 2020-08-10 15:20:56

With the emergence of 5G and new technology like embedded sim(esim), purchasing and utilizing data plans have become revolutionized. Please feel free to check out eSIM data plans at: http://www.celitech.com

Zied Jemai 2024-07-09 23:35:58

Compare the features, prices, and coverage of different 5G providers to find the perfect match for your requirements.

<a href="https://news-blog6.blogspot.com/">US News Blog Informed Insights</a>
<a href="https://news-blog6.blogspot.com/search/label/Information%20%26%20Services/">"Top 5G Providers Compared, Speed, Coverage, and Price"</a>
<a href="https://news-blog6.blogspot.com/2024/05/discover-latest-network-coverage.html">Discover the Latest 5G Network Coverage Across the US!</a>

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