1

Content Introduction

LET Market Status

C-RAN overview

C-RAN Benefits and Features

Benefits: Installation/Evolution/Performance Aspects

Features: Centralized Coordination, Inter-site Operation

C-RAN Architecture

DU-RU Function Split

Fronthaul Technology

Future Evolution

2

Soaring LTE Compare to 3G

(Source : WCIS, Informa Jan 2014)

Dec 2009 Dec 2012 Dec 2014 (E) Dec 2013 Dec 2010 Dec 2011 LTE

Oct 2001 Oct 2002 Oct 2003 Oct 2004 Oct 2005 Oct 2006

2007

263 Commercial operators in 97

countries

41 million subs added in Q4 2013

3

LTE Expansion in Korea

13

Smart Cache™

3G

22

VoLTE CA

Multi Carrier

LTE Launch

Wideband LTE

eMBMS C-RAN

8

6 Carrier 6 Sector

4

World Firsts in Korea

4.9M Subscribers

300Mbps

Jan. 2014 Commercial

5

LTE Traffic Usage in Korea

2.5 GB

30.9 PB

43.3 PB

50 PB

58.4 PB

68.4 PB 72.7 PB

79.8 PB

86.9 PB

1.8 GB

2.8 GB

Traffic usage per subscriber

Total traffic usage

~50% Growth in LTE traffic per user in just over 1 year

6

Mobile TV in Korea

7

Mobile TV in Korea

(Paid Subs.)

8

Mobile Traffic Explosion

9

Macro cells Small cells

Mobile Traffic Explosion

10

Centralized Baseband Processing

Cloud Computing

Coordinated Radio

Clean Radio Access Network

4C in C-RAN

11

Network Evolution

Traditional BS (DU/RU in one box)

Distributed RAN (D-RAN)

(DU/RU in different box )

Centralized RAN (C-RAN)

(DU Cloud + Remote RU)

DU

DU Cloud

RU

DU

Server

RU

* DU: Digital Unit * RU: Radio Unit

DU

RU

12

C-RAN Network Diagram

Distance < 20 km

Active Optic MUX

Passive Optic MUX

Active WDM

Passive WDM

Fronthaul Network (Optical Transport

Network)

* WDM : Wavelength Division Multiplexing * RRU: Remote Radio Unit

DU Centralized Site Remote Site

(Baseband Processing, Coordinator, Edge App.)

13

C-RAN in Seoul (1/2)

※ Seoul covers 600Km2, 10M pops

Central Site

14

C-RAN in Seoul (2/2)

Optic MUX

DU Centralized Site

Remote Site

16

Installation Aspect

C-RAN

Total N Site - N BBU - Nx3 RRU

Distributed-RAN

Total N Site - Nx3 RRU 1 C-RAN BBU

C-RAN BBU

RRU RRU RRU

BBU

RRU RRU RRU

BBU

RRU RRU RRU

BBU

RRU RRU RRU

RRU RRU RRU

RRU RRU RRU

Centralized-RAN

* DU: Digital Unit * BBU: Base Band Unit * RRU: Remote Radio Unit

Reduced CAPEX/OPEX, CO2

Simpler site installation

Reduced site rental and electricity cost

17

Evolution Aspect

Site visiting - Change Tech-A BBU to Tech-B BBU

Central office visiting - Change Tech-A Card to Tech-B Card

Tech-B card

Tech-B C-RAN Tech-A

C-RAN

Easier evolution with new h/w, new technology

• e.g. BBU + IT server

18

Performance Aspect

Wireless Channel Information

Scheduling info. (QoS/CQI/Load)

IP Network

Radio Resource Coordination Enhanced Performance

Information exchange over IP network - Long Latency, Low Speed

Information exchange side the Rack - Short Latency, High Speed

Distributed-RAN Centralized-RAN

C-RAN

* QoS: Quality of Service * CQI: Channel Quality Information

Easier evolution for better performance with new h/w, new technology (e.g. BBU + IT server)

19

C-RAN Coordination (1/3)

Optimal resource allocation over multi-cell network

in a centralized manner

Cell#3

Cell#1

Cell#2

Cell#N

Cell#4

UE A

UE B

UE D

Cell#1 Cell#2 Cell#3

Cell#4 Cell#5 Cell#6

Cell#7 Cell#8 Cell#9

Cell#N-1 Cell#N

UE B UE A

UE C

UE D

Channel/Scheduling Info.

(QoS/CQI/Load)

Resource Coordination

C-RAN Coordinator

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C-RAN Coordination (2/3)

Cells cooperate with each other in a distributive way. (Each cell decides its own air resource usage.)

To increase the system efficiency in long-term average sense

Limited information (specified in the standard interface) is shared among cells.

Cells are coordinated in a centralized way. (Central coordinator decides the whole network air resource coordination.)

To increase the system efficiency at every millisecond

More information (than standard interface) is exchanged with central coordinator.

ICIC C-RAN Coordination

Interference

X2 Load Information

Interference

Channel Info.

Scheduling Info.

C-RAN Coordinator

Coordination Output

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C-RAN Coordination (3/3)

Serving

Nbr 2

VoLTE VoLTE VoLTE

Serving Cell

Nbr 1

VoLTE UE

VoLTE is affected by neighbor cell interference

Nbr 1

Nbr 2

Serving

Nbr 2

VoLTE

blank

VoLTE

blank

VoLTE

blank

Serving Cell

Nbr 1

VoLTE UE

Interference avoidance by blanking

Nbr 1 blank blank blank

Nbr 2

Intf., Intf.

Intf. Intf.

VoLTE Example Voice quality improvement at cell edge

22

UL CoMP Joint Reception (JR)

Uplink signal is jointly received at multiple points to improve the received signal quality

Conventional UL CoMP JR

UL signal path used by serving cell

*UL CoMP: UpLink Coordinated Multi-Point

SINR

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Inter-site Carrier Aggregation (1/2)

Carrier aggregation using cells from different sites

Chooses Pcell and Scell with the best signal quality

Seamless CA in coverage mismatch area

* Pcell: Primary cell * Scell: Secondary cell

without CA

Thro

ugh

pu

t

이동구간 Coverage mismatch area

with CA

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Inter-site Carrier Aggregation (2/2)

Select and aggregate the best cell of each carrier

22.3 Mbps 45.9 Mbps

1.8 GHz

800 MHz

Cell 0 Cell 1 1.8 GHz 800 MHz

Cell 0 Cell 1

Conventional CA Inter-site CA

(Best Cell Aggregation)

1.8 GHz cell coverage

800 MHz cell coverage

1.8 GHz cell coverage

800 MHz cell coverage

PCell 8.3dB(15.6M) 1.6dB(7.5M)

SCell -1.4dB(6.7M) 12.8dB(30.3M)

8.3dB(15.6M) 1.6dB(7.5M)

-1.4dB(6.7M) 12.8dB(30.3M)

*Based on actual measurement in Korea (FDD, 10 MHz + 10 MHz)

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HetNet Carrier Aggregation

CA between Macro and Small cells

Control and voice are supported by Macro cell

No handover

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One cell operation

Same PCID for multiple N cells

No handover among N cells with same PCID

C-RAN supports larger and flexible N

C

A B

A B C

SIN

R

One Cell operation

Conventional

Small cell

Small cell

One Cell Operation

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C-RAN Benefits and Pitfalls

CAPEX/OPEX Savings

Multiple sites share a high-density DU

Small form factor for each site

Fewer visits to sites for maintenance

EPC

Traditional RAN C-RAN

EPC Backhaul Network

Fronthaul Network Backhaul

Network

Transport Cost between DU/RU

Current technology requires dark fibers

because of high bandwidth

Additional central offices required

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Consideration for C-RAN (1/2)

To minimize transport cost between DU and RU

Minimization of the bandwidth

Alternative transport solutions (e.g. Microwave, Ethernet)

To maximize resource pooling

High density DU, and DU pooling

Reuse for evolved radio technology

To maximize radio performance

Edge performance enhancement by inter-site operation

High-bandwidth and low-latency connectivity between DUs

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Consideration for C-RAN (2/2)

To maximize Maintenance Efficiency

Plug and Play RU

Automatic re-parenting between DU and RU

To utilize the benefits of DU centralization

Interworking with Coordination server, Cache server, Local breakout

server, Analytics server, etc.

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Since March 2013,

Study of C-RAN Technologies

• Function Split between DU and RU

• DU pooling

• Virtualization

• RAN Sharing

• Prototype Development * DU: Digital Unit * RU: Radio Unit * RAN: Radio Access Network

NGMN Project C-RAN

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DU-RU Function Split

(Source: NGMN RAN Evolution C-RAN white paper )

* IV : CPRI interface * IV’ : Compressed CPRI interface

Function Split Options Delay

Sensitivity Bandwidth

Level Comment

Partial L1 at site, L1/L2/L3 centralized

High High • CRAN features applicable

L1 at site, L2/L3 centralized

High Medium • CRAN features not applicable

L1/L2 at site, L3 centralized

Medium Low • CRAN features not applicable • Less centralization effect

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DU-RU Architecture

Option C Option A

DU

RF

RU PHY

Layer 3 Layer 3 PDCP

Layer 3 Layer 3 RLC

Layer 3 Layer 3 MAC

Layer 3 Layer 3 PDCP DU

RF RU

Layer 3 Layer 3 RLC

Layer 3 Layer 3 MAC

Layer 3 Layer 3 PHY

DU

PHY (Cell Processing)

Front- end

RF RU

Layer 3 Layer 3 PDCP

Layer 3 Layer 3 RLC

Layer 3 Layer 3 MAC

Layer 3 Layer 3 PHY

(User Processing)

Option B

DU processing by IT server (Workload is proportional to user traffic amount)

Much smaller bandwidth b/w DU and RU. Limited C-RAN features support.

Conventional

(Source: NGMN RAN Evolution C-RAN white paper )

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Fronthaul Network Topology

CO

T

RT

RT

RT

RT

RT

RT

RT

RT

CO

T

Point-to-Point Topology (A operator who owns abundant dark fibers)

Ring Topology (B operator who wants to reduce dark fiber rental)

* COT : Central Office Terminal * RT : Remote Terminal

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DU-RU Interface: CPRI

CPRI protocol layers

* CPRI : Common Public Radio Interface

LTE 20MHz 4x4 MIMO requires 5Gbps

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Concept of CPRI Compression (1/2)

…0010101111010101 Compression Decompression

Reduced-rate IQ data (DL)

Compression Decompression 0010101111010101…

Reduced-rate IQ data (UL)

Compression/Decompression algorithm is applied to both ends

Baseband Processing Remote Radio Unit

Optic Cable I/Q Sample I/Q Sample

Compression for DL Decompression for UL

Compression for UL Decompression for DL

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Concept of CPRI Compression (2/2)

* D. Samardzija et al., “Compressed Transport of Baseband Signals in Radio Access Networks”, IEEE Trans. Wireless Comm., Sep. 2012

39

Effect of CPRI Compression

Before After

Reduced Bandwidth between DU and RU

Number of optic link and optic module is reduced

10G x 2 10G x 1

* COT : Central Office Terminal * RT : Remote Terminal

2.5G x 8

RT

2.5G x 4 2.5G x 4 2.5G x 8

RT RT

COT RT

RT RT

COT

Example: compression ratio of 2:1

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CPRI over Ethernet

Ethernet Fronthaul

Ethernet based DU-RU Networking

Automatic re-parenting between DU and RU

Dynamic DU pooling

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Analog Signal over Microwave

CPRI to Analog over Microwave

Limited distance

Graceful performance degradation

core

network EPC M/W

UDC CPRI

RU

central unit (cluster)

PDCP

RLC MAC PHY CPRI RF

M/W

UDC

BWOptimized

150MHz

BCPRI 4915.2Mbps

(20MHz, 4x4 MIMO)

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5G and C-RAN

5G not standardized yet

mmWave(eg. 28GHz) and very broad bandwidth(800MHz~1GHze)

Lots of antennas (e.g. 64)

UE peak throughput of 1Gbps ~ 1.5Gbps

Providing services in hot spots due to short coverage

C-RAN for 5G

CPRI fronthaul may not be feasible due to very high sampling rate.

Function split needs to be further investigated.

Higher bandwidth between DUs is required.

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Cloud based Services

Fronthaul Network

More intelligent processing by Cloud Server

Radio performance enhancement by scheduler and SON processing

Cache / Local Breakout / Analytics / M2M / Etc.

Intelligent Processing

* SON : Self Organizing Network * M2M : Machine to Machine