The document discusses the evolution and requirements for the 5G network, highlighting the transition from current technologies to new design principles like centralized radio access networks (C-RAN) and next-generation fronthaul interfaces (NGFI). It emphasizes the need for seamless connectivity, user-centric design, and efficient bandwidth management as critical components for implementing 5G. Challenges regarding latency, synchronization, and protocol compatibility in transitioning to NGFI for 5G are also addressed.

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World’s Largest 4G Network
~1.1M 4G BSs
BS
~720K@2014
Terminal
Sales volume 210M+
Types 1000+, Price <50$
~100M@2014
~360M 4G Subscribers
Subscriber
~90M@2014
Coverage
~330 Cities@2014
Feb, 2106
~1.2B pop (~86%), Reach Villages

2. Green Communication Research
Center established in Oct. 2011,
initiated 5G Key Tech R&D.
Rethink Shannon
Rethink Ring & Young
Rethink Signaling & Control
Rethink Antenna
Rethink Spectrum & Air Interface
Rethink Fronthaul
Rethink Protocol Stack
To start a green journey of wireless systems
For no more “cells”
To make network application/load aware
To make BS invisible
To enable wireless signal to “dress for the occasion ”
To enable Soft RAN via NGFI
To enable flexible configuration of diversified access points
and optimal baseband function split between BBU pool & RRS
Green
Soft
Super Fast
“Towards Green & Soft: A 5G Perspective” IEEE Comm. Mag, Vol.52, Feb.2014
5G Era: Rethink Fundamentals

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5G New Requirements
Immersive
Seamless
Tactile
Ultra Reliable
Massive
Ultra Dense
New design principles, new key technologies, …
Seamless Coverage, Hot Spot High Capacity, Low-power Massive-connection, Low-latency Ultra-reliable

4. UCN (enabled by C-RAN/NGFI)
High Freq.
RIT
Low Freq.
New RIT
Massive-MTC
RIT
Mission-Critical
RIT
Low-latency &
high-reliability
Seamless wide-area
coverage
Hotspot &
high data rate
Low-power &
massive-connections
Green and Soft
SDAI (enabled by MCD)
LTE evolution Low freq. eMBB NB-IOT
Latency redu.
V2X
PTN PON
Transportation
network
Core Network SDN/NFV
RAN
E2E 5G System Key Technologies

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User Centric RAN (UCN): C-RAN a key enabler
Framework of radio access network
Localized data,
service & forwarding
Multi-Connectivity & Flexible
Topology
Autonomous
Network
Unified Access & Seamless
Mobility
Service Awareness
5G WiFi
4G
Signaling
Centralized
Radio Network Controller
广覆盖通用信令层
Macro signalling (data)
layer
本地数据接入点
Local Data Access
Data
D2D
Internet/App
Radio Data Center
RAN Entity
HSS/AAA/PCC
CN Entity
Smart Operation
Including C-RAN (Centralized and Cloud)
Next Generation Fronthaul Interface
(NGFI)
uMTC
mMTC
Mobile
Internet
CN-RAN Repartition
Turbo Charged Edge
RAN restructure
Network Slice
as a Service

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Fronthaul challenges surfaced with C-RAN (2011)
Traditional BTS
Distributed BTS
C-RAN
• Centralized Control and/or Processing
• Collaborative Radio
• Real-Time Cloud
• Clean System Target
Fronthaul used to be an issue for LTE C-RAN:
CPRI Compression and WDM
CMCC has conducted extensive trials to seek cost-
effecitive FH solutions in LTE era
Traditional BTS
Distributed BTS

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Traditional FH solutions must be revisited in 5G era

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NGFI (xHaul)
Traffic dependent
Support of statistical multiplexing
Support of cell coordination
Antenna independent
Radio interface technological neutrality
• The key to achieve FH interface redesign lies in the function re-split
b/w BBU and RRU
• The new NGFI will further lead to re-design of underlined transport
networks with packet switching capability

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Decoupling Ant./Non-ant. Related Processing
The evaluation of the existing FH Interface
(CPRI, OBSAI):
The FH bandwidth is proportional to the
number of antennas.
The FH bandwidth is at least 2 orders
of magnitude higher than BH bandwidth.
0.2 1.6 20
30
400
10000
0.013 0.384 150
0
2000
4000
6000
8000
10000
12000
GSM TD-SCDMA 8-antenna TD-LTE
Radio BW
FH BW
BH BW
Decoupling antenna/non-antenna related processing:
It is proposed that antenna related functions should be
moved from the BBU to the RRH.
FH bandwidth will decrease significantly if the BBU/RRH
function split can decouple the non-antenna related
processing and the antenna related processing.
Considering the C-RAN centralized deployment and the
technologies of 5G, FH is facing a bandwidth explosion.
The number of Carriers
in C-RAN
The number of
antennas
FH BW based on the existing
FH Interface
100 8 1Tbps
100 128 16Tbps

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Decoupling cell/UE Processing
The existing FH interface is a constant bit rate interface, which is load
independent and does not match with the features of mobile traffic.
Decoupling cell/UE processing:
Cell processing is irrelevant to traffic load and is fixed no matter how many UEs are active.
FH bandwidth will be lower and load dependent.
In C-RAN Mode, cell/UE processing decoupling can further help reduce power consumption.
 When the traffic load is low, part of C-RAN cloud resource can be shut down.
 When there is no active UE, BBU software can be switched to a dormant state

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S1 Termination
PDCP
RLC
Low MAC
Bit-level
Processing
Bit-level
Processing
Modulation
Layer Mapping
& Precoding
IDFT &
De-Modulation
Channel Estimation
& Equalization
Resource
Mapping & IFFT
FFT &
Resource De-Mapping
2
3
4
To RRU From RRU
5
High MAC
1"
1"
Some symmetrical BBU-RRU function
re-split solutions
（Taking LTE as an example）
There are many different aspects between UL
and DL:
Generally, the DL rate is not equal to the UL rate.
The bandwidth of UL and DL are not always in the
same order of magnitude.
 The bit width of UL is usually larger than that of the
DL.
Decoupling UL/DL processing
 NGFI design should take into account the
asymmetrical function split solutions.
 For example, the function split solution 3 could
be used for UL while the solution 4 used for DL.
Decoupling UL/DL Processing

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NGFI Progress
下一代前传网络接口
白 皮 书
White Paper of
Next Generation Fronthaul Interface
Version 1.0
June 4th, 2015
China Mobile Research Institute
Alcatel-Lucent
Nokia Networks
ZTE Corporation
Broadcom Corporation
Intel China Research Center
White Paper on NGFI released in June 2015
• Lead of IEEE 1914 (NGFI) WG in IEEE
• 1st NGFI WS held & NGFI WP released in June, 2015
- MoU signing with Broadcom, Intel, Alcatel-Lucent, HuaWei, ZTE,
Nokia, Xilinx & Altera
• Co-founder of IEEE 1904.3
• Leading the project of NGFI in CCSA
• NGFI as the key component in NGMN 5G WP, FuTURE 5G WP
• NGFI/FH promotion and study in ITU-T, IEEE and 3GPP
• NGFI Paper in IEEE Communication Magazine & GLOBECOM 2015
NGFI feasibility study with Xilinx
“Rethink Fronthaul for Soft RAN”, IEEE Comm. Mag. 2015
“NGFI, The xHaul”, GLOBECOM 2015

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Challenges Ahead
 Mapping of FH to Ethernet packet, undergoing in IEEE 1904 WG
 Stage 1: CPRI encapsulation (applicable to 2G, 3G and 4G)
 Stage 2: NGFI encapsulation for 5G
 Latency
 To meet RT requirement of wireless communication
 Limited latency budget for FH (e.g. 250us defined in NGMN for LTE C-RAN)
 Synchronization
 LTE Frequency sync. of 0.05ppm & phase accuracy of +/-1.5us
 Higher in 5G
 Transport of FH packets
 Over IP, MPLS, etc.
 E2E QoS
O&M, protection etc.

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IEEE NGFI (1914) WG
7 Founding members
• Target: efficient & scalable FH for
5G
• Officially approved: Feb. 2016
• Sponsor: IEEE COM/SDB
• 7 founding companies with more
than 50 subscribers so far from
~30 companies
• Scope of 1914.1 project:
- NGFI transport network
architecture
- Requirements
- Function split analysis for LTE
• http://grouper.ieee.org/groups/1914/
• The first NGFI WG meeting, April 25-28,
San Jose, CA
Contact: huangjinri@chinamobile.com