Korea Communication Review October 2014

IN THIS ISSUE
Korean ICT News • page 1-2
KT aims to build a nationwide GiGA Internet access network (1 Gbps to the home) by the end of the year • page 5
Korean big 3 telcos offer hassle-free and instant upgrade to Giga-class Internet without re-cabling • page 6-8
FEATURED ARTICLE: SK Telecom's Network Evolution Strategies: Carrier aggregation, inter-cell coordination and C-RAN architecture • page 9-18
LTE Statistics in Korea UPDATE • page 20-22
Broadband subscribers in Korea UPDATE • page 23-24
IPTV subscribers in Korea UPDATE • page 25
Research and Consulting Scope of Netmanias • page 26
© Netmanias Consulting • www.netmanias.com

Korea Communication Review Publisher: Dr. Harrison J. Son | son@netmanias.com
Associate Editor: Dr. Michelle M. Do | misun.do@netmanias.com
Advertising Sales: Ho-Young Lee | hylee@netmanias.com | +82-2-3444-5747
Business Development: Steve Shin | cm.s.shin@netmanias.com | +82-10-2884-8870

In the past two years, some new technologies have been introduced in Korea, apparently increasing broadband Internet speed 3~5 times faster, from 100 Mbps to 300~500 Mbps, instantly. It certainly is fascinating in that such speed improvement can be achieved even without re-cabling in apartment buildings. Because 100 Mbps has 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. Read the full article (page 6-8)

According to the Ministry of Science, ICT and Future Planning (MSIP), the total mobile traffic of the country as of late August reached 108.8 PB, and LTE traffic (100.8 PB) accounts for 92.7% of the total. Since May, a drastic growth has been witnessed especially in 4G smartphone traffic, increasing fast by over 20 PB, from 69.4 PB in April to 93.7 PB in July. This growth seems mostly caused by LTE unlimited plans that were competitively introduced by the big 3 - first by LG U+ on April 2, and then later in the month by SK Telecom and KT - offering unlimited voice, text AND LTE data services.

Korea’s smartphone subscriptions are already reaching 40 million, in less than five years after the first smartphone‘s debut in the country in 2009. According to the mobile subscription statistics data (as of late July) revealed by MSIP on August 25, Korea has 39.6 million smartphone subscribers, representing 70.4% of the nation’s total mobile subscribers (56.3 million). The subscriptions increased by about 300,000 compared to the late July’s. With this growth rate, the number will very likely exceed 40 million by late September, or by October at the latest.

Korean big 3 telcos offer hassle-free and instant upgrade to Giga-class Internet without re-cabling
In August, LTE traffic represented 92.7% of Korea’s total mobile traffic, 12.6 times more than 3G’s 7.3% – mostly driven by the introduction of LTE unlimited plans Smartphone subscriptions to exceed 40 million in late September hairman Chang-gyu Hwang of KT (with sales of KRW 23.8 trillion in 2013), at a press
conference held at KT Olleh Square
Source: KT
Fronthaul (Active WDM)
3-band CA
Data
Small RRH
No HO
No HO
CoMP
CoMP
Inter-site CA
N cells 1 PCI, TM9
Elastic Cell
Hierarchy Cell
Virtual One Cell
Dual Connectivity
Macro RRH
BBU Pool
Control & Data
Control
Macro RRH
Inter-site CA
Wi-Fi AP
LTE-WiFi CA
LTE Femto CA
Femto
Unified C-RAN
BBU virtualization
Smarthpone
Feature Phone (2G/3G)
Smart Pad
52.5M
56.3M
39.6M
(70.4%)
16.0M
(28.5%)
0.61M
(1.1%)
21.3M
(40.8%)
30.5M
(58.3%)
0.48M
(0.9%)
August 2014
4G Smartphone ~ 33 M
3G Smartphone ~ 7 M
3G Feature phone ~ 9M
2G Feature phone ~ 7M

Korea ICT News
KT aims to build a nationwide GiGA Internet access network (1 Gbps to the home) by the end of the year
To go nationwide with its Giga Internet (GiGA FTTH) service, KT has been introducing high-capacity OLT that offers 1 Gbps to each subscriber, which is 10 times faster than the current 100 Mbps.
The high-capacity OLT system was first introduced in pilot projects that had been conducted in selected Seoul metropolitan areas until May 2014. Then it was further deployed across the entire Seoul metropolitan areas in June, and then across 35% of the country by July. On August 17, KT announced that it would complete the nationwide deployment of the system by the end of the year. Read the full article (page 5). KT and SKB launched the world’s first 4K UHD IPTV service on September 1 On September 1, KT and SK Broadband presented UHD STB, offering the world’s first commercialized UHD IPTV (2160p) service. The UHD service requires about 15 Mbps for 30 fps service, and 30Mbps for 60 fps service. The two operators are offering an UHD STB by Humax to their subscribers. Currently, live broadcasting service (1 UHD channel) and VoD service (29 UHD VoD contents) are being offered by KT, while only VoD service (24 UHD VoD contents) is offered by SKB. LG U+ plans to join them in September.

HFR’s Fronthaul solution to hit the East Asian market
On August 26, HFR, a Fronthaul equipment (flexiHaulTM) supplier for SK Telecom, signed an agreement for
supplying the relevant solution to an East Asian telecommunication operator after being selected through a fierce competition with other vendors from Taiwan and Europe. The company said its experiences of supplying Fronthaul equipment to SK Telecom and SK Telecom’s cooperation were the key contributing factors to the selection.

LG U+ and Nokia developed “Intelligent Network Platform”
On September 17, LG U+ presented “Intelligent Network Platform (INP)” that it developed jointly with Nokia, and this platform is expected to provide faster and uninterrupted video streaming. The company has been putting effort into achieving high video quality to differentiate its LTE services from others’. The key features of the INP are: •Mobile content caching (transparent caching) •DNS caching •Video optimization (Video pacing) •CDN Interworking •Local breakout These features are implemented by RACS (Radio Application Cloud Server) that is installed in eNB as a card. RACS performs caching of video content files like those on YouTube,
thereby reducing the time required for downloading the files. RACS also accelerates loading of web pages by
having DNS addresses converted by it, instead of by a remote server. The video pacing functionality helps a
user save data usage by allowing the user to download only the amount of contents being viewed. This functionality was designed to overcome the drawbacks of the early HTTP progressive downloading. LG U+ and Nokia are planning to complete a field test by the end of October, and begin commercializing RACSs for example by installing them in LTE base stations nationwide.

DASAN Networks Successfully lands a FTTH contract with Viettel in Vietnam: July 24 , DASAN successfully entered Vietnam’s high-speed Internet market. Viettel, the largest telecom operator in Vietnam, has selected DASAN Networks as their network equipment supplier to establish the infrastructure in providing high-speed Internet throughout Vietnam. DASAN Networks made a contract agreement to supply about US$18 Million worth of FTTH GPON systems to Viettel for the next 4 months until November as its first order, and plans to negotiate to supply more FTTH equipment soon. Starting this year, Viettel plans to offer FTTH based high-speed Internet services all over Vietnam. Biddings in supplying GPON equipment for the project started last year, DASAN Networks was selected as the first supplier among other global telecommunication companies.

Samsung and ubiQuoss chosen as official network equipment supplier for ITU PP-14: On September 24, Samsung and ubiQuoss were chosen as official equipment suppliers for a wired and wireless network to be built in the venue of the ITU Plenipotentiary Conference that Korea is hosting in October. ubiQuoss is supplying high-capacity EPON OLT (Model: U9500H). U9500H accommodates 5,000 subscribers (OLT) and support 1Gbps per subscriber. Samsung is supplying 365 wireless Internet access points (APs) and all other control, operation and security systems needed for the event. This will be the company’s debut in the world’s wireless Internet market, in only two years after its entry to the wireless Internet industry in 2012. The conference host, ITU, chose the two suppliers after acknowledging the proven excellence of their products through four technical tests.

eNB (DU)
RACS
RACS: Radio Acceleration Cloud Server
FEATURED ARTICLE
SK Telecom's Network Evolution Strategies
Carrier aggregation, inter-cell coordination and C-RAN architecture
Dr. Michelle M. Do
ARTICLES
KT aims to build a nationwide GiGA Internet access network (1 Gbps to the home) by the end of the year
Chris Yoo
Korean big 3 telcos offer hassle-free and instant upgrade to Giga-class Internet without re-cabling
Dr. Harrison J. Son
KOREA ICT NEWS
Table of contents
1. CA Evolution Strategies
1.1 Combining More Bands: 3-band CA
1.2 Femto Cell with CA
1.3 Combining Heterogeneous Networks: LTE-Wi-Fi CA
1.4 Combining Heterogeneous LTE Technologies: FDD-TDD CA
2. Inter-Cell Coordination Evolution Strategies
2.1 Inter-Site CA in Macro Cell Networks
2.2 SUPER Cell 1.0: Virtual One Cell
2.3 SUPER Cell 2.0: Elastic Cell and Inter-site CA
2.4 SUPER Cell 3.0: Hierarchy Cell
3. RAN Architecture Evolution Strategies
3.1 Unified RAN
3.2 vRAN

• In August, LTE traffic represented 92.7% of Korea’s total mobile traffic, 12.6 times more than 3G’s 7.3% – mostly driven by the introduction of LTE unlimited plans
• Smartphone subscriptions to exceed 40 million in late September
• KT and SKB launched the world’s first 4K UHD IPTV service on September 1
• HFR’s Fronthaul solution to hit the East Asian market
• LG U+ and Nokia developed “Intelligent Network Platform”
• DASAN Networks Successfully lands a FTTH contract with Viettel in Vietnam
• Samsung and ubiQuoss chosen as official network equipment supplier for ITU PP-14
KOREA ICT STATISTICS
LTE Statistics in Korea UPDATE
Broadband subscribers in Korea UPDATE
IPTV subscribers in Korea UPDATE
Research and Consulting Scope of Netmanias
October 2014

CPRI Fronthaul (Active WDM)
3-band CA
Data
Small RRH
No HO
No HO
CoMP
CoMP
Inter-Site CA
N cells 1 PCI, TM9
Elastic Cell
Hierarchy Cell
Virtual One Cell
Dual Connectivity
Macro RRH
BBU Pool
Control & Data
Control
Macro RRH
Inter-Site CA
Wi-Fi AP
LTE-WiFi CA
LTE Femto CA
Femto
Band 5 (850 MHz, 10MHz)
Band 3 (1.8GHz, 20MHz)
Band 1 (2.1 GHz, 10MHz)
vRAN
(Virtualized BBU)
Service-Aware RAN
App. Server(e.g. cache)
(300/450Mbps)
(150Mbps)
(upto Gbps)
EPC Core
New Band
Unified RAN
(Macro RRH & Small RRH)
Macro cell site
셀 사이트 1
Coordination server GE
KT
SK (SK Broadband)
LG U+
Cable
Operators
8.1
(42.4%)
19.0M
Broadband
subscribers
in Korea
(August 2014)
4.7M
(24.8%)
3.0M
(15.8%)
3.2M
(16.6%)
3.90
1.30
0.31
0.04
2.85
1.86
1.78
0.65
1.33
0.35
0.03
1.22
0.92
2.44
KT SK LG U+ MSO
Million
XDSL
LAN (UTP)
HFC (Cable)
FTTH
8.1M
4.7M
3.0M 3.2M
XDSL
LAN
FTTH
HFC
KT aims to build a nationwide GiGA Internet access network (1 Gbps to the home) by the end of the year | By Chris Yoo
On May 20, Chairman Chang-gyu Hwang of KT (with sales of KRW 23.8 trillion in 2013) announced that "KT will open up a new age of GiGAtopia by investing KRW 4.5 trillion (USD 4.4 billion) in GiGA FTTH, GiGA Path (heterogeneous networks convergence technology that combines LTE and Wi-Fi networks), and GiGA Wire (copper wire-based transmission technology) for the next three years." Later on June 19, Mr. Seong-mok Oh, head of the Network Business Division at KT, announced the company would accelerate the process and Commercialize GiGA FTTH and GiGA Wire in the second half of this year. To go nationwide with its Giga Internet (GiGA FTTH) service, KT has been introducing high-capacity OLT that offers 1 Gbps to each subscriber, which is 10 times faster than the current 100 Mbps. The high-capacity OLT system was first introduced in pilot projects that had been conducted in selected Seoul metropolitan areas until May 2014. Then it was further deployed across the entire Seoul metropolitan areas in June, and then across 35% of the country by July. On August 17, KT announced that it would complete the nationwide deployment of the system by the end of the year. KT's high-capacity OLT system is an enhanced version of its previous FTTH OLT (100 Mbps per subscriber). It can cover upto 5,120 users (80x10GE-PON ports, Split ratio 64), and has an excellent switching capacity of 2 Tbps, 40 times higher compared to the previous OLT. With the introduction of the high-capacity OLT system, KT is fully fledged to respond to soaring traffic to be caused by UHD TV, Internet ubiQuoss U9500H High-capacity OLT deployed for GiGA Internet service by KT Switching capacity ubiQuoss U9500H 1.92 Tbps Throughput 1.4 Bpps 10GE ports 80 Split ratio 64 ONTs per system 5,120 Uplink ports 16 x 10GE Height 10 U by UHD TV, Internet of Things (IoT), etc. Chang-Seok Seo, vice president of the Network Technology Unit at KT, noted that "With deployment of high-capacity OLT systems, KT will be able to provide differentiated Giga services that no other can do, and drastically improve service quality as well. KT will devote itself in developing new technologies and conducting researches to ensure high quality service for customers." Upgrade of broadband access speed from 100 Mbps to 1Gbps will result in increased traffic in backbone networks. To effectively respond to this traffic, KT i) replaced the routers in premium core networks that deliver ITPV/VoD traffic with high-capacity 4 Tbps routers last August, and ii) has continued to expand KORNET, which is in charge of delivering Internet traffic, through router replacement, additional line card installation, etc.

2. Upgrade Premium Core Capacity (Premium Core: QoS, IP/MPLS)
3. Upgrade KORNET Capacity (KORNET: Best-effort, IP routing)
PE
OLTs
BRAS
CO
MDU
MDU
MDU
IPTV Headend
Data Center
Domestic
ISPs(SKB, LG U+)
Global
Internet
ONT
ONT
ONU
ONU
Edge
• Live encoder VoD(Cold), …
• eMBMS,..
PE
P
P
BRAS
Edge
BRAS
Edge
Media SW
EPC Core
Center
Edge Node (2)
Node (31)
Akamai CDN edge,
OTT CDN (Pooq),
Cloud, ...
KIX
Center
Node (2)
PE
Edge
PE
Edge
TIC
IPTV VoD
servers (Hot)
splitter
splitter
UTP
VDSL
1. FTTH Access: E-PON→10GE-PON
splitter
splitter
Data Center
Core
Node (19)
Edge
Node (56)
nx10G mx10G
...
IPTV Traffic
(Multicast)
10G
Internet Traffic
L3 SW
Core Node (14)
IPTV/VoD Traffic
P
P
ONT
Global Hub
10GE-PON
OLT

Korean big 3 telcos offer hassle-free and instant upgrade to Giga-class Internet without re-cabling | By Dr. Harrison J. Son
Migration Strategies to Giga-Class Broadband Access in Korea. 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, 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.
Table 1. Giga-Class Broadband Access Strategy in Korea: Summary
KT SK (SK Broadband) LG U+
Brand ▶ GiGA Wire (G.hn) ▶ 2-Pair Ethernet ▶ Super-Fast Network
Copper line
1-pair (Telephone line)
1-pair (UTP)
2-pair (UTP Cat 5/5e) 2-pair (UTP Cat 5/5e)
DL/UL Speed
300Mbps/100Mbps
200Mbps/200Mbps
500Mbps/500Mbps 500Mbps/500Mbps
Commercialization H2 2014 (planned) Q2 2013 Not announced
Vendors
ubiQuoss
(U4124B, C301G)
HFR
(H5224G/5216G, H514G/524G)
Dasan Networks
ubiQuoss
G.hn (300 Mbps)
2-Pair Ethernet (500 Mbps)
802.3z 1000Base-T (1Gbps)
Upgrade to Giga-Class
No additional re-cabling construction in apartment buildings
Re-cabling construction in apartment buildings (Huge Capex)
Existing MDU wiring systems
UTP Cat5e to the home Fast Ethernet (100 Mbps)
Current Services
√
√
KT
SKB, LG U+
KT, SKB, LG U+
KT, SKB, LG U+
KT, SKB
Fiber to the home Fast Ethernet (100 Mbps) 802.3as 1000Base-X (1 Gbps)
KT, SKB, LG U+
Telephone lines to the home VDSL2 (100 Mbps)
UTP Cat5 to the home Fast Ethernet (100 Mbps)
7
© Netmanias Consulting • www.netmanias.com
Korea Communication Review • October 2014
Korean big 3 telcos offer hassle-free and instant upgrade to Giga-class Internet without re-cabling
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.
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, around 300 Mbps, considering probable speed degradation in actual deteriorated conditions caused by Crosstalk, outdated on-premise cables, etc. 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+?
SKB and LG U+ have different strategies. Unlike KT, these two are not targeting old apartment buildings with
only phone lines, but ones built more recently or ones with additional UTP cabling installed at cost, that is those with Cat5 cabling. More than 5 million households in Korea are known to live in these types of apartment units. To offer Internet and telephone services to households living in apartment units where UTP Cat5 cables (4-pair) are installed, Korean operators use 2 pairs of the lines inside a cable for Internet service (Fast Ethernet with 100 Mbps), and 1 pair for POTS phone service. And the last 1 pair is left unused. According to the standards (for Gigabit Ethernet and Fast Ethernet), 1 Gbps requires all 4 pairs of lines (Cat5e) while 100 Mbps requires only 2 out of 4 pairs (Cat5). To achieve 1 Gbps speeds, all 4 pairs should be used, and cables have to be Cat5e. So, additional cabling is inevitable. To avoid this issue, that is, to support Internet speeds higher than 100 Mbps without additional installation of cables, SKB 300+ Mbps Bundled telephone lines G.hn Access Multiplexer (GAM)
MDF
GNT
1-pair
(Phone line)
RJ11
RJ45
GNT
1-pair
(Phone line)
GNT
1-pair
(Phone line)
300+ Mbps
300+ Mbps
MDU (Condominiums,
Apartment Complexes)
Home
Home
Home
...
IPTV
STB
No additional re-cabling construction
POTS
E-PON
Central Office
OLT L3 SW
Splitter
PSTN
FTTP (Fiber To The Phone line)
• deploys GNTs (G.hn Network Terminal) at home and GAM (G.hn Access Multiplexer) at MDF/IDF
• provides point to point connection via existing telephone line (1-pair)
• 200~300 Mbps throughput per subscriber
• VDSL2 replacement for higher speed broadband service
Internet
G.hn Performance (source: ubiQuoss)
Source: KT ubiQuoss's G.hn products
Distance (m)
KT GiGA Wire - Instant upgrading to Giga-Class Internet
8
© Netmanias Consulting • www.netmanias.com
Korea Communication Review • October 2014
Korean big 3 telcos offer hassle-free and instant upgrade to Giga-class Internet without re-cabling
cables, SKB and LG U+ developed a new technology that can support up to 500 Mbps by using only 2 pairs of lines in existent Cat5 cables (bidirectional 500 Mbps at a distance of 100 m). Of course, it is not a standard technology. SKB adopted HFR's new device specially designed for this purpose and launched a new service in June 2013. LG U+ had necessary devices developed by Dasan and ubiQuoss in last June, but no service commercialization plan has been announced so far. As seen above, KT's Giga service is different from those of SKB and LG U+ in that KT is targeting apartment units with only traditional phone lines as well as those with UTP cabling, whereas the other two are targeting only those with UTP cabling. UTP cabling. No doubt that KT is No. 1 in broadband Internet service. After almost a decade of stagnation in speed improvement, Korea is finally taking a long-overdue step forward toward Giga-class Internet service. For apartment buildings that were built recently and thus have optical fiber cables already installed, upgrading to 1 Gbps is easy. On the other hand, for older buildings, it requires installation of new cables, which would apparently result in huge CAPEX. Given that, it is quite impressive that the big 3 managed to find ways to offer Giga-class service of 300 ~ 500 Mbps to users without re-cabling construction. The 2-Pair Ethernet is a vendor-proprietary technology developed by modifying the current 1000Base-T standard(IEEE 802.3ab). This technology enables an Ethernet switch (i.e., FTTB ONU for apartment buildings) to utilize 2-pair lines out of 4-pairs inside a single Category 5/5e UTP cable, providing provide 500Mbps data transmission(=250Mbps per pair X 2 pairs) via 2-pair line. And, the 2-pair Ethernet system is actually implemented by adding a specific functional block of 2-pair Ethernet operation to the MAC/PHY Layer of existing 1000Base-T Ethernet system. The following functionalities are to be appended for the 2-pair Ethernet system. ❶ Rate adaption function between 1000Base-T (1Gbps) and 2pair Ethernet (500Mbps) interface ❷ Flow control function to manage a data traffic prevent a loss of Ethernet frame traffic caused by exceeding 500Mbps ❸ Signal conversion function of 4-pair based 1000Base-T to match with 2-pair Ethernet (2D-PAM5)
SK Broadband's MDU broadband innovation - 500 Mbps with just 2 pairs
l H5224G (24 ports), H5216G (16 ports)
• Auto-Negotiation (100/500/1000Mbps)
• 100 Mbps per port (UTP Cat5, 2-pair)
• 500 Mbps per port (UTP Cat5, 2-pair)
• 1000 Mbps per port (UTP Cat5e, 4-pair)
• Uplink: GPON, GE
l H514G
• Uplink: Auto-negotiation (100/500/1000Mbps)
• LAN ports: 4 10/100/1000Mbps
l H524G
• Uplink: Auto-negotiation (100/500/1000Mbps)
• LAN ports
- 4 10/100/1000Mbps ports
- Wi-Fi (IEEE 802.11n, 2.4G & 5G Dualband 2Tx 2R)
L2 Ethernet Switch CPE (RG)
Deployed products: HFR’s 2-pair Ethernet Products
MDF
CPE 500Mbps
RJ45
MDU (Condominiums, Apartment Complexes)
Home
Home
...
IPTV STB 1-pair
2-Pair Ethernet Switch
4-pair
No additional re-cabling
construction
2-pair
POTS
G-PON
Central Office
OLT L3 SW
Splitter
PSTN
SK Broadband IP
Network
CPE
1-pair 4-pair
2-pair
UTP 4P (CAT5)
UTP 4P
(Cat5)
500Mbps
2-Pair Ethernet
• deploys CPE at home and 2-Pair Ethernet Switch at MDF/IDF
• provides point to point connection via existing CAT5/5e cable (2-pair used)
• bidirectional 500 Mbps throughput per subscriber
• 100 Mbps LAN service replacement for higher speed broadband service
n Gigabit Ethernet / CAT5e 100m / Full Duplex
n 2-pair Ethernet / CAT5 100m / Full Duplex
n Fast Ethernet / CAT5 100m / Full Duplex
250 Mbps x 4 Pairs = 1Gbps
250 Mbps x 2 Pairs = 500 Mbps
100 Mbps 100 Mbps
K Telecom is the #1 mobile operator in Korea, with sales of KRW 16.6 trillion (USD 15.3 billion) in 2013, and with 50.1% of a mobile subscription market share in 2Q launched LTE service back in July 2011, and now more than half of its subscribers are LTE service subscribers, with 56% of LTE penetration as of 2Q 2014.
increased number of cell sites. To save costs of building and operating the increased number of cell sites, it has built C-RAN (Advanced-Smart Cloud Access Network, A-SCAN, as called by SK Telecom) through BBU
concentration since January 2012. In 2014, SK Telecom began to introduce small cells (low-power small RRHs) in selected areas. As with macro cells, small RRHs have the same C-RAN architecture where they are connected to concentrated BBU pools through CPRI interfaces. SK Telecom calls it "Unified RAN (Cloud and Heterogeneous)". To prevent performance degradation at cell edges caused by introduction of small cells, SK Telecom developed HetNet architecture (known as SUPER Cell) where macro cells cooperate with small cells. The company, aiming to commercialize 5G networks in 2020, plans to commercialize SUPER Cell first in 2016,
as a transitional phase to 5G networks.
mobile subscription market share in 2Q 2014. It launched LTE service back in July 2011, and now more than half of its subscribers are LTE service subscribers, with 55.8% of LTE penetration as of 2Q 2014.
Due to LTE subscription growth, more advanced device features, and high-capacity contents, LTE networks are experiencing an unprecedented surge in traffic. To accommodate the flooded traffic, SK Telecom adopted LTE-A (Carrier Aggregation, CA) in 2013, and Wideband LTE-A (Wideband CA) in 2014 for improved network capacity. As another effort to increase network capacity, the company made LTE/LTE-A macro cells a lot smaller, as small as hundreds of meters long, resulting in an increased number of cell sites. To save costs of building and operating the increased number of cell sites, it has built C-RAN (Advanced-Smart Cloud Access Network, A-SCAN, as called by SKT) through BBU concentration since January 2012.

© Netmanias Consulting • www.netmanias.com
Korea Communication Review • October 2014
SK Telecom's Network Evolution Strategies: Carrier aggregation, inter-cell coordination and C-RAN architecture
Dr. Michelle M. Do (misun.do@netmanias.com)

ICIC
DL CoMP (proprietary) | early 2012
Virtual One Cell (TM-9) | H2 2014 (planned)
Elastic Cell (CoMP, Inter-Site CA) | 2016 (planned)
Hierarchy Cell (Dual Connectivity) | 2016 (planned)
eICIC | 2014 (planned)
Inter-Cell Coordination
ð higher speeds at cell edges
Carrier Aggregation
ð speed increased n times
3-Band CA | 300 Mbps
3-Band CA | 450 Mbps
Macro Cell
2-Band CA | 225 Mbps
Femto CA | 150 Mbps
UL CoMP | 2014.04
LTE-Wi-Fi CA | upto Gbps
FDD-TDD CA | upto Gbps
Small Cell (Hetnet)
LTE | 75 Mbps
2-Band CA | 150 Mbps
2011.7
2013.6
2014.6
2014 H2 (planned)
2015 (planned)
2014 (demonstrated at MWC)
2014.7 (demonstrated)
2014.6 (demonstrated)
RAN Architecture
ð RAN TCO reduced/
LTE-A performance enhanced
C-RAN |
Macro Cell |
2012.1
Unified RAN |
Macro & Small Cell |
2014 (First introduced)
vRAN |
Virtualization |
2014
(demonstrated)
Commercialized to be Commercialized
Figure 1. SK Telecom’s Network Evolution Strategies
Inter-Site CA | 2014 (demonstrated at MWC)
Service-Aware RAN|
RAN Cache |
(demonstrated at
MWC 2013)
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© Netmanias Consulting • www.netmanias.com
Korea Communication Review • October 2014
1. CA Evolution Strategies
CA is a technology that combines up to five frequencies in different bands to be used as one wideband
frequency. It allows for expanded radio transmission bandwidth, which would naturally boost transmission
speeds as much as the bandwidth is expanded. So, for example, if bandwidth is increased n times, then so is
the transmission speed. Table 1 shows the LTE frequencies that SK Telecom has as of September 2014,
totaling 40 MHz (DL only) across three frequency bands, which operate as Frequency Division Duplexing
(FDD). SK Telecom commercialized CA in June 2013 for the first time in the world, and then Wideband CA a year later in June 2014. as a transitional phase to 5G networks. We analyzed SK Telecom's network evolution strategies using the following three axes: 1) Carrier Aggregation (CA), 2) Inter-Cell Coordination, and 3) RAN Architecture in the Figure 1. Here, the CA axis shows how speeds have been and can be increased (n times) by expanding total frequency bandwidth aggregated. The Inter-Cell Coordination axis displays the company's strategy to achieve higher speeds at cell edges by improving frequency efficiency. Finally, the RAN Architecture axis shows SK Telecom's plan to switch to an architecture that would yield better LTE-A performance at reduced costs of building and operating RAN. Figure 2 is SK Telecom's evolved LTE-A network, as illustrated according to the evolution strategies shown in Figure1.
Figure 2. SK Telecom’s LTE-A Evolution Network
CPRI Fronthaul (Active WDM)
3-band CA
Data
Small RRH
No HO
No HO
CoMP
CoMP
Inter-Site CA
N cells 1 PCI, TM9
Elastic Cell
Hierarchy Cell
Virtual One Cell
Dual Connectivity
Macro RRH
BBU Pool
Control & Data
Control
Macro RRH
Inter-Site CA
Wi-Fi AP
LTE-WiFi CA
LTE Femto CA
Femto
Carrier Aggregation Evolution
• 3-Band CA
• LTE-Wi-Fi CA
• LTE Femto CA
• FDD-TDD CA
Band 5 (850 MHz, 10MHz)
Band 3 (1.8GHz, 20MHz)
Band 1 (2.1 GHz, 10MHz)
vRAN (Virtualized BBU)
Inter-Site Coordination Evolution
• Inter-Site CA in Macro Cell Networks
• SUPER Cell 1.0: Virtual One Cell
• SUPER Cell 2.0: Elastic Cell, Inter-Site CA
• SUPER Cell 3.0: Hierarchy Cell
RAN Architecture Evolution
• Unified RAN
• Service-Aware RAN
• vRAN
Service-Aware RAN
App. Server(e.g. cache)
(300/450Mbps)
(150Mbps)
(upto Gbps)
EPC Core
New Band
Unified RAN
(Macro RRH & Small RRH)
Macro cell site
Macro cell site
Coordination server GE
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© Netmanias Consulting • www.netmanias.com
Korea Communication Review • October 2014
attempting to apply CA technology to Femto cell as well.
The company completed a technical demonstration of LTE-A Femto cell in MWC 2014, proving it is capable to
support 2-band CA. It will be conducting trial tests in a commercial network in late 2014 for final commercialization of the technology in 2015.
1.3 Combining Heterogeneous Networks: LTE-Wi-Fi CA
In July 2014, SK Telecom performed a technical demonstration of heterogeneous CA that combines LTE
and Wi-Fi bands by using multipath TCP (MPTCP), an IETF standard. MPTCP is designed to combine more
than one TCP flow (or MPTCP subflow) to make a single MPTCP connection, and send data through it. This
technology is applied to a device and application server. In the demonstration, an MPTCP proxy server was used instead of an application server (Figure 3). This technology will allow SK Telecom to combine i) its LTE bands that are currently featuring 2-band CA and ii) 802.11ac-based Giga Wi-Fi bands, together offering up to 1 Gbps or so. The detailed commercialization timeline is to be determined in accordance with the company's plan for future development of MPTCP device and server.
1.4 Combining Heterogeneous LTE Technologies: FDDTDD CA
This method enables operators to expand transmission bandwidth by combining two different types of LTE
technologies: FDD-LTE and TDD-LTE. In a demonstration performed in Mobile Asia Expo in June 2014, SK Telecom successfully demonstrated FDD-TDD CA using ten 20 MHz bandwidths and 8x8 MIMO antenna showing 3.8 Gbps throughout.
2. Inter-Cell Coordination Evolution Strategies
CA improves network capacity by broadening frequency bandwidth, whereas inter-cell coordination technologies do the same task by enhancing frequency efficiency. Inter-cell coordination is designed to manage radio resources more efficiently by having cells in different sites share user and/or cell information with each other. It is now offering a maximum speed of 225 Mbps through the total 30 MHz bandwidth. As of May 2014, out of the total 15 million LTE subscribers, 3.5 million (23%) subscribers are using CA-enabled devices. Let's see where SK Telecom's CA is heading.
1.1 Combining More Bands: 3-band CA
3-band CA combines three frequency bands, instead of the current two, for wider-band transmission. Currently, SK Telecom has three LTE frequency bands, and is offering 2-band CA of 20 MHz or 30 MHz by
combining two of the bands at once. This is because, although LTE-A standards technically support combining of up to five frequency bands, RF chips in CA-enabled mobile devices available now can support
combining of two bands only. 3-band LTE devices are on the way and will be arriving in the market soon - sometime in early 2015 or by late 2014 at the latest. So, SK Telecom is planning to commercialize 3-band CA that combines all of its three frequency bands, just in time. The commercialization of 3-band CA is expected to increase transmission bandwidth to 40 MHz and data transmission rate to 300 Mbps. SK Telecom is also planning to combine three 20 MHz bands to further expand transmission bandwidth up to 60 MHz, and boost data transmission rate to 450 Mbps.
1.2 Femto Cell with CA
SK Telecom commercialized LTE Femto cell for the first time in the world in June 2012, to provide indoor users with more stable communication quality, and now is attempting to apply CA technology to
Table 2. SK Telecom’s Multi-band CA (FDD-FDD)
# of Bands
2-band
3-band
2-band
3-band
Max. Data Rate
150 Mbps
300 Mbps
225 Mbps
450 Mbps
Total BW
20 MHz
40 MHz
30 MHz
60 MHz
BW Aggregation (MHz)
10+10 (B3+B5)
10+20+10 (B1+B3+B5)
20+10 (B3+B5)
20+20+20
Status
Commercialized (June 2013)
to be Commercialized (H2 2014 or 2015)
Commercialized (June 2014)
Planned
Table 1. SK Telecom’s Commercial LTE Frequency (as of September 2014)
DL UL
850 MHz Band 5 10 MHz 10 MHz 75 Mbps
2.1 GHz Band 1 10 MHz 10 MHz 75 Mbps
1.8 GHz Band 3 20 MHz 15 MHz 150 Mbps
LTE Band
Bandwidth Max. Data Rate
SK Telecom's Network Evolution Strategies | Dr. Michelle M. Do (misun.do@netmanias.com)

macro cell network include ICIC and DL CoMP (proprietary) commercialized in 2012. In MWC 2014, inter-site CA was demonstrated showing how cell sites can cooperate with each other for optimized CA. CoMP operates in a centralized way based on C-RAN (A-SCAN) introduced in 2012 along with some of SK Telecom's proprietary technologies like improved scheduling, energy efficiency, etc. Since CoMP commercialization, ICIC has been replaced by CoMP. SK Telecom began to use small cells in its networks in 2014. The more small cells are used, the higher frequency reuse ratio is achieved. However, there have been some drawbacks, like higher handover rates, stronger interference, increased control overhead, etc. as more cells mean more cell edges. So, to overcome these issues, and to maximize the effect of network capacity increased by small cells, an appropriate method of inter-cell coordination should be chosen depending on how densely small cells are deployed.
each other. Inter-cell coordination can also be used both in small cell-introduced HetNet and a legacy homogeneous network. But, more complicated and refined coordination is required because in HetNet, where both high power and lower power cells are deployed together, UEs at cell edges are likely to experience different interference situations. Inter-cell coordination technologies applicable to a macro cell network include ICIC and DL

Figure 3. LTE - Wi-Fi CA using Multipath TCP (MPTCP)
SKT IP Backbone
LTE-A Network IP Backhaul
P-GW
CSP, OTT
(e.g., File Box)
eNB Giga Wi-Fi AP
Proxy
Public Internet
SubflowLTE
MPTCP Client
MPTCP Proxy
Server
225 Mbps 866 Mbps
1 Gbps
Movie file Application
TCP
SubflowWi-Fi
TCP
MPTCP
SubflowLTE
(TCP)
IPLTE IPWi-Fi
SubflowWi-Fi
(TCP)
TCP
Application
MPTCP
SubflowLTE
(TCP)
IPLTE IPWi-Fi
SubflowWi-Fi
(TCP)
Application Server
capacity increased by small cells, an appropriate method of inter-cell coordination should be chosen depending on how densely small cells are deployed. To enhance network capacity efficiently depending on
the degree of small cell deployment in a macro cell, SK Telecom presented SUPER Cell concept, and a 3-phase evolution plan in MWC 2013. In line with the plan, the company is gradually moving forward to its strategic destination, successful commercialization of SUPER Cell in 2016. In October 2013, it conducted a
demonstration of Virtual One Cell (SUPER Cell 1.0).
Table 3. SUPER Cell Evolution Strategies
Evolution Phase
Concept
To be commercialized in
Small cell density
Purpose
1.0
Virtual One Cell
H2 2014
Low
Call drop prevention, better performance at cell edges
2.0
Elastic Cell, Inter-Site CA
2016
Moderate
better performance at cell edges
3.0
Hierarchy Cell
2016
High
Better performance of small cell
Key technologies
Small cell ID (PCI)
Small cell frequency
No. of cell(s)
communicating with UE
TM9
Same as macro cell's
Same as macro cell's
(Macro: F1, Small: F1)
Virtually one (but, can be
multiple)
• CoMP (in the same frequency)
• Inter-Site CA (in different
frequencies)
Different from macro cell's Same or different from macro cell's
(Macro: F1, Small: F1, F2)
Multiple Dual Connectivity
Different from macro cell's
Designated frequency
(Macro: F1, Small: F2)
Dual (one for control and the
other for data)
SK Telecom's Network Evolution Strategies | Dr. Michelle M. Do (misun.do@netmanias.com)
BBU
Pool
Coordination
server
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© Netmanias Consulting • www.netmanias.com
Korea Communication Review • October 2014
of the other band, the UE's aggregated speed naturally drops. In such case, inter-site CA allows the UE to replace the "out-of-coverage" band with the same band, although operated by the neighbor cell site, that has
better channel condition, so that the UE can continue to benefit from the band aggregation.
Figure 4 provides an example of the effect of inter-site
CA that can be gained in a macro cell network that supports 2-band CA. In the example, there are two cell
sites (Cell site 0 and 1), and they each have two cells that are operated by two bands (F10 and F20 from Cell
site 0, and F11 and F21 from Cell site 1 ). A CA-enabled device, by connecting to a serving cell in each band
(PCell in one band and SCell in the other), receives data from both serving cells. Figure 4 (a) shows a case where inter-site CA is not supported. Before or after handover, if the quality of one frequency band becomes degraded at cell site 0 or 1, CA performance becomes downgraded too. On the other hand, Figure 4 (b) illustrates a case where inter-site CA is supported. Both cell sites, through mutual cooperation, ensure optimal CA at cell edges any time, even in case coverages between the bands are mismatched, by dynamically combining frequency bands to increase the aggregated transmission rate.
destination, successful commercialization of SUPER
Cell in 2016. In October 2013, it conducted a demonstration of Virtual One Cell (SUPER Cell 1.0).
Table 3 provides a brief overview of SK Telecom's 3-phase plan for evolving SUPER Cell.
Below, we will discuss some inter-cell coordination technologies: inter-site CA for a macro cell-based homogeneous network, and SUPER Cell for HetNet. Inter-site CA can also be used in HetNet, and will be
discussed under SUPER Cell 2.0 section.
2.1 Inter-Site CA in Macro Cell Networks
CA, designed to increase speeds (by n times) by combining different frequency bandwidths, may slow
down UE's speeds or interrupt CA communication if coverages of the aggregated frequency bands do not
match. Coverage mismatches are usually caused near cell site edges. Inter-site CA lets BBUs cooperate with each other to ensure frequency bandwidth aggregation is performed not only between the bands in the same cell site, but also between ones in different sites. If UE moves out of the coverage of one band while still within the coverage of the other band, Figure 4. Inter-Site CA in Macro Cell Networks t3
-
-
PCell
SCell
(a) Intra-Site CA
Cell site 0
t1 t2
Cell site 1
PCell PCell
SCell SCell
F1
F2
- -
- -
F1
F2
t3
-
-
PCell
SCell
(b) Inter-Site CA
Cell site 0
t1 t2
Cell site 1
PCell PCell
Scell -
F1
F2
- -
- SCell
F1
F2
Inter-Site CA: 50 Mbps
Cell Site 1
5 Mbps
20 Mbps
Cell site 0
30 Mbps
5 Mbps
F1
F2
Cell Site 1
5 Mbps
20 Mbps
Cell site 0
30 Mbps
5 Mbps
F1
F2
Intra-Site CA: 35 Mbps
PCI: Physical Cell ID PCell: Primary Cell SCell: Secondary Cell
BBU
Pool
Coordination
server
30Mbps
30Mbps
5Mbps
RRH
F1 1.8 GHz (Band 3) F2 850 MHz (Band 5)
Cell Site 0
- Cell F10 (PCI = 1)
- Cell F20 (PCI = 2)
Handover Seamless CA
20Mbps
t1 t2 t3
t2 t2
CPRI CPRI
t1 t2 t3
PCell
SCell
PCell
Multi-site cell Multi-carrier Scheduling
F1 cell
boundary
F2 cell
boundary
F1 F2
SK Telecom's Network Evolution Strategies | Dr. Michelle M. Do (misun.do@netmanias.com)
Cell Site 1
- Cell F11 (PCI = 11)
- Cell F21 (PCI = 12)
SCell
35 Mbps
50 Mbps
Cell Site 0
- Cell F10 (PCI = 1)
- Cell F20 (PCI = 2)
Cell Site 1
- Cell F11 (PCI = 11)
- Cell F21 (PCI = 12)
F10
F20
F11
F21
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Korea Communication Review • October 2014
To accommodate this issue, transmission mode 9 (TM9) newly defined in 3GPP Release 10 is employed in
this architecture. TM9 allows a device to receive the same signal from more than one cell while staying near
cell edges, and to communicate at maximum speeds while staying at cell centers, thereby effectively enhancing network capacity. In October 2013, in a demonstration showing how Virtual One Cell works, SK
Telecom proved the transmission speeds of devices at cell edges increased by 1.5 ~ 2 times, and network
capacity by 5~10%. The company is now preparing for its commercialization in late 2014.
2.3 SUPER Cell 2.0: Elastic Cell and Inter-site CA
SUPER Cell 2.0 can be best used when there are a moderate number of small cells in a macro cell after initial stages of introducing small cells. In this phase, unlike phase 1 Virtual One Cell, small cells have cell IDs (PCIs) different from the macro cell's, and work as independent cells. Compared to phase 1, more signal interference is caused. So, this architecture controls interference through inter-cell coordination, rather than having the cells work as one cell, and additionally assigns different frequencies to some small cells. Macro and small cells improve cell edge performance by supporting CoMP and inter-site CA through mutual cooperation. Cells that use the same frequency cooperate with each other using CoMP while those that use different frequencies cooperate using inter-site CA.
frequency bands to increase the aggregated transmission rate.
2.2 SUPER Cell 1.0: Virtual One Cell
SUPER Cell 1.0 architecture is used during initial stages where small cells are introduced, and works effectively
when there are not many small cells in a macro cell yet. Small cells use the same frequency and Physical Cell ID (PCI) as the macro cell's, and both small and macro cells work as Virtual One Cell. Because this architecture causes no handover when devices switch from one cell to another, it prevents call drops, and improves transmission quality during communication near cell edges. Unfortunately, however, the effect of network capacity enhancement is minimal because the effect of frequency reuse, a benefit of introducing small cells, is not expected.
Figure 5. Virtual One Cell based on TM9
Transmission Mode (TM) refers to a way of transmission between a base station and UE in a multi-antenna
environment. TM9 is defined in 3GPP Release 10, and supports up to 8-layer transmission using UE-specific
beamforming. There are two UE-specific reference signals: Demodulation Reference Signal (DM-RS) and Channel State Information Reference Signal (CSI-RS). DM-RS is used for channel estimation and data demodulation and CSI-RS is used for CSI measurement with much lower overhead compared to the Cell-specific Reference Signal (CRS).

BBU Pool
Small RRH
Macro RRH
Handover-free
F1
Virtual One Cell
• Same Cell ID (e.g., PCI =1): No handover
• TM9: increase capacity
TM9
PCI = 11 (macro cell)
F1
PCI = 11 (small cell)
PCI = 21 (macro cell)
F1
• Handover
• Performance
F1 degradation
PCI = 22 (small cell)
Transmission Mode (TM) 9
SK Telecom's Network Evolution Strategies | Dr. Michelle M. Do (misun.do@netmanias.com)
Legacy Cell
SUPER Cell 1.0 (Virtual One Cell)
F1
with UE are dynamically selected as a transmission cell group.
Figure 6 is an illustration of UE communication in
SUPER Cell 2.0, and shows how the number of transmission cells change as UE moves from one place to another: 1 → 2 → 3 → 2 (CoMP used in t2 and t3, and inter-site CA in t4). As such, SUPER Cell 2.0 guarantees UE is always served by the best cells, using CoMP and inter-site CA.
2.4 SUPER Cell 3.0: Hierarchy Cell
SUPER Cell 3.0 can be effective once small cells become densely deployed in a macro cell. At this stage, UE is
usually within the coverage of some small cells no matter where it is, and thus would inevitably experience
frequent handovers every time it moves. Moreover, transmission efficiency of the small cells would drop because of drastic increase in control overhead (e.g. handover control info., neighbor cell measurement
reports, broadcasted system info., etc.), and mobile batteries would not last long because of frequent
handovers. In the legacy architecture, cells are designed to deliver both control signalings and user data together, and the size of available transmission bandwidth is limited because conventional frequency bands are at lower frequencies below 3.5 GHz. So, the legacy architecture has use different frequencies cooperate using inter-site CA. Both CoMP and inter-site CA are performed by the central scheduler located at a BBU pooling site, but they use different ways to improve cell edge performance: In CoMP, the central scheduler dynamically selects a group of cells that experience good channel condition with UE, lets the cells send the same data to the UE, and turns off the cells that cause interference. On the other hand, in inter-site CA, it dynamically combines frequency bandwidths in different sites. HetNet that works based on CoMP is called Elastic Cell by SK Telecom. In July 2014, SK Telecom, in a demonstration showing how Elastic Cell technology works, confirmed the data rates at cell edges actually were improved by 50%. The company aims to commercially launch the technology by 2016. Elastic Cell is the core technology of SUPER Cell, and helps the paradigm of data transfer between base stations and users to shift from cell-centric to user centric. Previously, UE could communicate with only one cell at a time, and had to search for a cell that has the strongest signal strength, itself. But, now Elastic Cell allows UE to communicate with more than one cell at once, and enables the network to select a transmission cell group to communicate with the UE. Cells that are experiencing excellent channel conditions with UE are dynamically selected as
15
© Netmanias Consulting • www.netmanias.com
Korea Communication Review • October 2014
Figure 6. CoMP-based Elastic Cell and Inter-site CA
BBU Pool
Macro RRH
PCI = 22
PCI = 23
F1
F1
F1
PCI = 12
PCI = 13
CoMP
t4
2. Inter-Site CA (Different Channels)
CoMP
F1
F1
F2
F1
PCI = 11
(macro)
PCI = 21 (macro)
t1
t2
t3
F1
PCI = 31 (macro)
PCI = 32
F1
F1
F1
# of transmission cells
Transmission cells (PCI)
t1 t2 t3 t4
SK Telecom's Network Evolution Strategies | Dr. Michelle M. Do (misun.do@netmanias.com)
Legacy Cell (fixed Cell)
F2
F1
1. Elastic Cell
(Co-Channel)
SUPER Cell 2.0 (Elastic Cell)
SUPER Cell 2.0 (Hetnet Inter-Site CA)

improving network capacity effectively. This architecture is scheduled to be commercialized in 2016.
3. RAN Architecture Evolution Strategies
SK Telecom introduced C-RAN right from the very early stages of the LTE service commercialization (January
2012) as an effort to achieve higher mobile network operation efficiency and more cost savings. As a result,
most of the company's RAN is now in C-RAN architecture, where macro BBUs are separated from RRHs, and moved to centralized locations, such as CO or master base station while RRHs are left at cell sites. RRHs are connected, through a fronthaul network (ring-type active WDM network that delivers CPRI traffic, AKA Cloud Belt in SK Telecom term), to BBUs centralized at CO where coordination servers are running, thereby providing inter-cell coordination functions, such as CoMP and inter-site CA. SK Telecom's C-RAN has moved forward to Unified RAN with introduction of small cells in 2014, and will move further forward towards Service-Aware RAN, base stations for intelligent RAN, and Virtualized Radio Access Network (vRAN), the virtualization-based next generation base stations. These two are expected to provide operators with new revenue opportunities and users with enhanced QoE, by introducing/offering services in RAN, primarily based on Unified RAN. In the near future, Service-Aware RAN where cache frequencies below GHz. So, the legacy architecture has not been very effective in improving network capacity when small cells are densely deployed in a macro cell. On the other hand, in Hierarchy Cell, control signalings (control plane) and user data (user plane) are separated and delivered through different radio paths according to their QoE parameters. Small cells become high-capacity cells as they get to use much broader bandwidths in higher frequency bands (e.g. 3.5 GHz or 30 GHz) than macro cells. Control signalings and VoLTE data that require broader coverage are delivered by a macro cell, while user data which requires fast transmission is delivered by a higher-capacity small cell. The key idea of this architecture is dual connectivity. This means that UE can be connected to both macro and small cells at the same time. The macro cell, with broader coverage, always serves as a primary cell, delivering control signalings and working as mobility anchor. So, even when UE keeps moving from one small cell to another, no handover is caused, and mobile batteries last long. High-capacity small cells always serve as secondary cells, taking care of data delivery. Thanks to the dual connectivity, little control overhead is caused to small cells. Moreover, small cells, now that broader bandwidths are secured, can focus on fast transmission, achieving higher transmission efficiency even in a highly-dense cell environment, and thereby improving network capacity effectively. This architecture is scheduled to be commercialized in 2016.

Figure 7. Hierarchy Cell based on dual connectivity

BBU Pool
Macro
Control
Control
Control & Data
Handover
Handover
Handover
F1
Control & Data
Control
Control
Control & Data
Control & Data
F2
F1
Hierarchy Cell
• Split of Data and Control path
• Macro cell: handover signaling
Legacy Cell
Data
Macro RRH
Small RRH
Data
Control & Data
Legacy Cell
SUPER Cell 3.0
enhanced network capacity.

3.2 Service-Aware RAN
Previously, SK Telecom has provided services through its core networks, and hence RAN, incapable of identifying what service is being used by users, has merely served as a dumb pipe for data delivery. However, Service-Aware RAN can i) run service applications in RAN as well, and ii) identify services used by each user and provide them with region-specific or user-specific services by analyzing network/service usage information of each user. This enables operators to create new revenue streams other than network access fees and users to enjoy faster responses and personalized services, thereby improving user QoE and satisfaction. SK Telecom's Service-Aware RAN is based on Unified C-RAN, and so it allows RAN cache servers (or cards) at a BBU pool to cache video files and DNS, and offer features like video optimization, CDN interworking, local breakout, etc. in RAN as well. In MWC 2013, the company, jointly with NSN, demonstrated these Service-Aware RAN features, and vendors like Samsung and Nokia are finishing up development of technologies for installing application servers in RAN the near future, Service-Aware RAN where cache at a centralized BBU pool offers services like video caching in RAN will be commercialized. In the long time, SK Telecom's RAN will evolve into vRAN where BBUs are operated by SW installed on industry standard servers, realizing BBU virtualization.
3.1 Unified RAN: Since 2012, SK Telecom has built its C-RAN with LTE macro cells only, and then also with small cells (smallsized and low-power RRHs mounted on pole) since 2014. As with macro cells, small cells have C-RAN architecture and thus small RRHs are connected through CPRI interface to concentrated BBUs. In other words, both macro and small RRHs are connected to a BBU pool through the fronthaul network. SK Telecom calls this Unified RAN. The evolved Unified C-RAN can increase network capacity flexibly, and help HetNet (SUPER Cell) to connect cells in different sites/BBUs through a high capacity bandwidth and with a lower latency. This assures close coordination between HetNet cells, and thus can efficiently support SUPER Cell technologies (TM9, CoMP, inter-site CA, dual connectivity, etc.) for enhanced network capacity.

Figure 8. Evolution of RAN Architecture

Past Current
CO
DU
Ethernet
Backhaul
l Legacy Distributed RAN l Centralized & Cloud RAN (C-RAN) – 2012 l Unified RAN- 2014 (introduced Small RRH at small cell)
Macro Cell
RU
Centralized BBU
+ Macro RRH + Small RRH
+ Coordination server
(CoMP Scheduler, etc.)
Fronthaul
(Cloud Belt)
BBU
BBU
Ethernet
Backhaul
Macro RRH
Centralized BBU
+ Macro RRH
+ Coordination server
(CoMP Scheduler, etc.)
Fronthaul
(Cloud Belt)
Ethernet
Backhaul
CPRI
Macro RRH
Small RRH
CPRI
Standalone Base Station
(DU (BBU) and RU in one box)
Small RRH
... ...
CO (RAN) CO (RAN)
CPRI
l Service-aware RAN (e.g. Video caching at RAN) l Virtualized RAN (vRAN)
Near Future Long Term
BBU
Coordination server
Fronthaul (Cloud Belt)
Macro RRH
Small RRH
CPRI
Small RRH
...
CO (vRAN)
RAN Cache
CO (RAN) vRAN (BBU Virtualization)
GPP
Hypervisor
3G LTE LTE-A ㆍConnectivity SW
ㆍIntelligent service
Video
streaming
RRM
Scheduler
SON
Agent
Apps
BBU
SAEGW
Move to RAN
Service at RAN Service at Core
RAN (eNB)
RRHs (Macro) BBU s RRHs (Macr o & Small) BB Us
DU
GPP server

for installing application servers in RAN (for example, taking care of charging and handovers in relation to
traffic served directly by RAN cache, without going through P-GW). Given that, Service-Aware RAN is very
likely to be commercialized soon.
3.3 vRAN: RAN building/operating costs are one of the biggest investments that operators should make. To cut down the cost of RAN, and make employment of new network/service functions easier, SK Telecom developed so called vRAN that virtualizes BBUs. In January 2014, SK Telecom demonstrated LTE FDD radio communication (at 300 Mbps using 20 MHz bandwidth and 4x4 MIMO) by installing Hypervisor and Virtual Machine (VM) on an Intel Xeon processor based server and virtualizing the modem functionalities (PHY & MAC). The main feature of vRAN is to apply IT virtualization technology to BBUs so that vendor-specific BBUs that have been provided by the existing base station vendors can be replaced by industry-standard servers. An
industry-standard server, equipped with general purpose processors (GPPs) and HW acceleration technologies, can process RAN functions and services real fast by using SW. Moreover, new features for LTEA/B or 5G, or newly released RAN functions/services can be easily installed/removed through simple SW upgrade using open API. Because this architecture allows for sharing of HW/computing resources between BBUs through open interfaces, flooded traffic in one BBU can be easily diverted on to other BBUs. vRAN, by taking advantage of smarter technologies (more SW-oriented) and a more Cloud-friendly environment (open RAN architecture), can certainly be a great money saver for SK Telecom in that it can significantly save RAN costs for installing and operating base stations. However, apparently switching to vRAN is not an easy task. The company's investments in current RAN equipment should be protected, and vRAN-ready industry standard servers are not available in the market yet. That means, some BBU functions will continue to be used in forms of vendor-specific HWs provided by existing base station vendors, and the BBUs will become more intelligent, for example, with cloud capabilities for inter-BBU resource sharing, while other RAN functions (CoMP coordination, etc.) and application services provided at mobile edges are handled by SW on virtualized industry standard servers. SK Telecom will probably have to stick to this architecture for a long while.

© Netmanias Consulting • www.netmanias.com
Korea Communication Review • October 2014

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Mobile Statistics in Korea (August 2014)
As of August, 2014, the total number of mobile subscribers in Korea hit 56.3 million. This indicates that Korea has a penetration rate of 112%, considering its population, 50.3 million. Korea has 33.9 million LTE subscribers, which account for 60.1% of the total mobile subscribers.
Mobile subscribers - per access technology
2011
August 2014
33.8M
(60.1%)
22.5M
(39.9%)
56.3M
2G & 3G
n Mobile subscribers - per device type
As of the end of August 2014, 39.6M subscribers, which is 70.4% of the total 56.3M mobile subscribers,
are smartphone users.
Smarthpone
Feature Phone (2G/3G)
Smart Pad
52.5M
56.3M
39.6M
(70.4%)
16.0M
(28.5%)
0.61M
(1.1%)
21.3M
(40.8%)
30.5M
(58.3%)
0.48M
(0.9%)
August 2014
As of the end of August 2014, the LTE traffic reached 100.8 PB, which is 12.6 times higher than 3G traffic.
LTE traffic represented 92.7% of Korea’s total mobile traffic – mostly driven by the introduction of LTE
unlimited plans
n Mobile data usage - per access technology
100.8 PB
(92.7%)
8.0 PB
(7.3%)
4G LTE
August 2014
108.8 PB
4G LTE
Feb. 2011
51.2M
n Monthly Traffic - per device type
3G
(Feature phone +
Smartphone)
4G Smartphone ~ 33 M
3G Smartphone ~ 7 M
3G Feature phone ~ 9M
2G Feature phone ~ 7M
4G Smartphone
3G Smartphone
3.123 GB
1.140 GB
2G & 3G Feature phone 0.005 GB
As of the end of August 2014, 4G smartphone, 3G
smartphone and 2G/3G feature phone users generate
3.123 GB, 1.140 GB and 5 MB of traffic on average per
month.
1 6 1 6 1
2011 2012 2013 2014
7 8
* Source: Ministry of Science, ICT and Future Planning
21
© Netmanias Consulting • www.netmanias.com
Korea Communication Review • October 2014
LTE Statistics in Korea
n Mobile Traffic Composition in Korea (4G Traffic only)
n Subscriber Traffic Distribution (Heavy User Behavior)
45.1% 44.3% 45.2%
19.3% 18.9% 18.1%
13.1% 13.5% 14.6%
9.8% 11.2% 10.4%
7.9% 6.9% 7.6%
4.8% 5.2% 4.1%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
Q4 2013 Q1 2014 Q2 2014
Etc.
Market Download
Multimedia (Music, etc)
SNS
Web
Video
In Korea, the top 10% of subscribers who make the heaviest use of the 4G network’s resources account for
46.3% of total traffic. In Korea, the top 10% of subscribers who make the heaviest use of the 3G network’s resources account for 84.6% of total traffic.

32.4%
46.3%
100%
Subscriber Percentile
Traffic Percentile
4G (June 2014)
1% 5%10% 100%
35.1%
69.7%
84.6%
100%
Subscriber Percentile
3G (June 2014)
Traffic Percentile
The chart above presents the results of analysis of data traffic using DPI equipment introduced by the Korea's
big 3 operators. In the analysis, only 4G LTE traffic was included and 3G traffic was excluded. However, given
the fact that as of August 2014 the volume of LTE traffic is 12.6 times larger than that of 3G, the results can
sufficiently serve as references for the entire mobile traffic. The chart shows the distribution of data traffic by
application. We can see, the volume share of video and music streaming traffic reached 59.8%, proving the
surge in mobile traffic has been driven by video traffic.

SK Telecom
KT
LG U+
28.2M
(50.1%)
16.9M
(30.2%)
11.1M
(19.7%)
56.3M
Mobile
subscribers
in Korea
August 2014
22
© Netmanias Consulting • www.netmanias.com
Korea Communication Review • October 2014
South Korea’s top 3 operators have LTE subscription rates that are higher than any of its global
competitors who launched the same service before them, especially LG U+ with the seemingly
unbeatable 71.7% as of the end of June 2014.
As of the end of August 2014, SK Telecom has 15.9M LTE subscribers, which account for 47.0% of the total
LTE subscribers in Korea.
Mobile subscribers trace – Split per network (November 2011 – August 2014)
3. LG U+
11.1M
9.3M
4G (LTE)
2G (CDMA)
3.1M
(27.7%)
9.0M
(96.6%)
0.3M
(3.4%)
9.0M
(72.3%)
LTE Deployment Status by Operator in Korea (November 2007 – August 2014)
15.9M
(47.0%)
9.9M
(29.3%)
8.0M
(23.7%)
n LTE subscribers growth by operator n LTE subscription rate
26.5M
28.2M
4G (LTE)
3G (WCDMA)
2G (CDMA)
8.6M
(30.6%)
3.7M
(13.1%)
0.4M
(1.4%)
19.0M
(71.8%)
7.1M
(26.7%)
1. SK Telecom
15.9M
(56.4%)
4G (LTE)
3G (WCDMA)
7.1M
16.4M (42.0%)
(99.1%)
16.5M 16.9M
2. KT
9.9M
(58.6%)
71.7%
57.3%
55.8%
54.5%
37.8%
Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4 Q1 Q2 Q3 Q4
2011 2012 2013 2014
LG U+ (Korea)
KT (Korea)
SK Telecom (Korea)
Verizon (US)
Docomo (Japan)
SK Telecom
KT
LG U+

* Source 1: Ministry of Science, ICT and Future Planning
* Source 2: KT, SK Broadband and LG U+
n Broadband subscription rate (Q1 2005 – Q1 2014)
The broadband subscription rate in Korea has been steadily increasing, reaching 76.6% in Q1 2005, 100% in Q4
2010, and 103% in April 2014.
KT
Cable operators
LG U+
Million
n Broadband subscribers by operator (Q1 2005 – Q2 2014)
KT
SK (SK Broadband)
LG U+
Cable Operators
8.1
(42.4%)
19.0M
Broadband subscribers in Korea (August 2014)
4.7M
(24.8%)
3.0M
(15.8%)
3.2M
(16.6%)
As of the end of August 2014, Korea has 19.0M broadband subscribers, and 42.4% of them (i.e. 8.1M) are KT users, which makes the company the unrivaled No. 1 in the country’s broadband market.
Q4 2010: 100%
Broadband subscribers
# of Households
18,852,555
18,269,153
Million
Click the link below to see statistics information on wired/wireless services and subscribers in Korea.
https://www.netmanias.com/en/?m=view&id=statistics_ict&no=6041
SK (SK Broadband)
23
© Netmanias Consulting • www.netmanias.com
Korea Communication Review • October 2014
Broadband Subscribers in Korea
XDSL
LAN (UTP)
HFC (Cable)
FTTH OLT
ONT
PON
OLT
L3 SW
ONU
Edge &
Backbone
Home CO
UTP PON
UTP
L2 SW
L3 SW
UTP
UTP
FTTH
LAN
Last mile line
• FTTH: Optical fiber (ONT at home)
• LAN: UTP cable (from L2 switch or ONU)
24
© Netmanias Consulting • www.netmanias.com
Korea Communication Review • October 2014
Since its launch in 2006, FTTH service subscribers have continued to increase. As of the end of August 2014, 5.5M (29.3% of the total broadband subscribers) are subscribing to this service. Different FTTH technologies have been adopted by the big 3 operators – E-PON by KT, G-PON by SK, and E-PON by LG U+ – but they all support 100 Mbps in UL and DL.
LAN (UTP)
FTTH
HFC
XDSL
Million
2005 2006 2007 2008 2009 2010 2011 2012 2013 2014
7.2M LAN (UTP)
(38.1%)
4.6M
(24.4%)
HFC
FTTH
5.5M
(29.3%)
XDSL
1.7M
(9.0%)
19.0M
Broadband subscribers in Korea
(August 2014)
Korea has 5.5M FTTH subscribers, and 70.5% of them (i.e. 3.87M) are KT users, making the company the No. 1 FTTH service provider in the country.
Broadband Subscribers in Korea – Access Technologies
8.1M
4.7M
3.0M 3.2M
n Broadband subscribers trace by access technology (Q1 2005 – Q2 2014)
n Broadband subscribers by operator – per access technology August 2014)
Q2
XDSL
LAN
FTTH
HFC
Pay TV Subscribers in Korea
Pay TV subscribers trace
Cable
IPTV
Satellite
The number of IPTV subscribers is increasing fast. It exceeded 9M in March 2014, and reached 9.2M a month later. This was an increase of 150,000 a month on average. With this growth rate, it is expected to exceed 10M this year. As the competition among IPTV, cable and satellite operators was getting tougher, they began UHD service in an effort to prevent subscriber churn and attract new subscribers. The service was launched by the cable operators and SK Broadband, in April. And KT and LG U+ are scheduled to begin the service by the end of this year.
IPTV subscribers trace by telco
KT
SK Broadband
LG U+
Million
Growth in Korea’s IPTV market has been mostly driven by KT. As of June 2014, the company has 5.4M IPTV
subscribers, which is 66.7% of the country’s total. IPTV operators in the market are in fierce competition with each other as well as with cable operators.
UHD TV services
Cable
14.8M
(52.4%)
9.2M
(32.7%)
4.2M
(14.9%)
IPTV
Satellite
28.3M
Pay TV subscribers in Korea (April 2014)
SK Broadband
KT
LG U+
5.4M
(66.7%)
2.4M
(30.2%)
1.8M
(22.2%)
9.6M
IPTV subscribers in Korea (June 2014)
Cable TV (CJ Hellovision, C&M, t-broad)
IPTV (SK Broadband)
Satellite TV (KT Skylife)
IPTV (KT)
Frame rate 60 fps 30 fps 30 fps (60 fps planned)
Resolution 4K (3840x2160) 4K (3840x2160) 4K (3840x2160)
Encoding rate 32Mbps 15Mbps 30Mbps
Codec HEVC (H.265) HEVC (H.265) HEVC (H.265)
Launch 2014.04 2014.09 2014.06
30/60 fps
4K (3840x2160)
20Mbps
HEVC (H.265)
2014.09
Locations
Headquarter
2F, Namyeong Building
730-13, Yeoksam-dong,
Gangnam-gu, Seoul 135-921,
Korea
Branch Office
3832 NE 88th Street
Seattle, WA 98115
USA
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NMC Consulting Group (Netmanias) is an advanced and professional network consulting company, specializing in IP network areas (e.g., FTTH, Metro Ethernet and IP/MPLS), service areas (e.g., IPTV, IMS and CDN), and wireless network areas (e.g., Mobile WiMAX, LTE and Wi-Fi) since 2002.
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