Front-haul networking for 5G:
An analysis of technologies andstandardization

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Hassan Halabian
hassan.halabian@Huawei.com
Canada Research Center
November 2017

Cloud-RAN
Advantages:
Simplify the RRH site – Full outdoor, low cost

Better RAN network performance - Facilitates cooperative radio schemes, e.g., ICIC, CoMP, Massive MIMO

Future oriented – RAN virtualization

Fronthaul

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CPRI widely Deployed For 4GCPRI is - TDM based synchronousinterface/ Symmetrical serial data
link/Steady data stream, ”Always on”
Embedded Ethernet or HDLC streams(C&M plane data)I/Q data is the time samples of the wirelessanalog signal (Data plane)
Front-haul capacity linearly scales with

Number of antenna ports/Number of sectors



Sampling rate (Radio spectrum BW)/I/Q bitwidthTransmission overhead (coding and headers,etc.)/compression factor etc

BER=10-12

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If Use 4G RAN Architecture for 5G
Facing high bandwidth challenge

Big challenge for Massive MIMO (64T/64R) – Beyond
100Gbps requirement

16064But the real fronthaul bandwidth depends on configuration– air spectrum bandwidth, Massive MIMO types etc

x85G

420bandwidth（MHz）

CPRI Split Point
50~130 us

4Gx16

Antenna num

Bandwidth Boosting Sharply
100(Gbps)

16050x32

with 4:1 compression

504G

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45G

eCPRI Protocol Stack
eCPRI Laye1:



eCPRI over electrical cable
eCPRI over electrical backplane
eCPRI over optical fiber

Real Time
C&M

other eCPRI
services

Connection OAM

C&M

Synchronization

eCPRI specific protocol layere.g.
SNMPPTP

UDP

UDP, TCP,SCTP, etc.

UDP

UDP, TCP

IP, IPsec

IP,IPsec

IP

IP,IPsec

User DataeCPRI over Ethernet:
eCPRI Services

eCPRI messages shall be transmitted instandard Ethernet frames

SyncE

eCPRI over IP:
eCPRI messages shall be transmitted in
UDP/IP packets

eRadio Equipment Control (eREC)
User

Sync

eRadio Equipment (eRE)Control& Mgmnt

User

eCPRI Layer

eCPRI Layer

Transport Network Layer
Physical Layer

Control& Mgmnt

Sync

ICMPTransport Network Layer
Transport NetworkFronthaul Network

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Physical Layer

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Ethernet, VLAN (priority tag), MACsec

5Ethernet
OAM

If Use New RAN Architecture for 5G
When compare CPRI with eCPRI, we found morechallenges

1: 5G AAU weight increasing

10~25 Gbps

eCPRI Split Point

50~130 us

Compared with CPRI part Phy function
embedded in 5G AAU

2: 5G AAU upgrade when add newfeatures•Ignore RAN challenges•eCPRI used for fronthaulWith Low Phy

High Phy

3: Do not forget 4G: CPRI + eCPRI
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6Possible 5G Fronthaul Solutions
Increasing 5G site number faces fiber limitation
Possible transport solutions:

Site number increasing due to 4.5GHz/28GHz

Limited fiber resource

Scenario1: Eth based

CPRI&eCPRI

Scenario2: WDM
CPRI&eCPRI

4G BBU

CPRI&eCPRI

Scenario3: PON
CPRI&eCPRI

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Scenario4: Microwave

75G CU/DU

Eth based Fronthaul Research Introduction
Fronthaul Requirements SideEthernet Based Fronthaul Network

RAN Requirements
Last PAR 2018/07, SA Revcom approval: 2019/05
802.3br and 802.1Qbu : Frame preemption
802.1Qbv – Traffic Scheduling (time-gated queues)

Define RRH/BBU Interface Implementation

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• Current focus: Profile(s) for current (CPRI 7.0)
• Next step is eCPRI• Another Team for Fronthaul based on Eth• Joint effort with CPRI Cooperation• Already demo for CPRI over Eth• Joint effort with IETF DetNet WG• Define new Eth Type for Fronthaul

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IEEE 1914.3 – CPRI over Ethernet

Standard for Radio Over Ethernet (RoE) Encapsulations and Mappings, definesThe encapsulation of digitized radiomapper/demapper functions to transfer CPRI streams over Ethernet.

The header format for encapsulation of existing digitized radio transport formats.

Three types of encapsulation techniques

structure–agnostic mapper: is only a container for the encapsulated digitized radio transport frames.

structure-aware mapper: has detailed knowledge of the encapsulated digitized radio transport format content

native RoE packet.
1914.3

eCPRI

Technology

Only EthernetUDP/IP/Eth and Eth. - any packet transport

Bandwidth

CBR (CPRI encapsulation) and VBR (Native RoE only)

User traffic related, VBR( ~10 fold reduction)

Topology

P2P connection, P2P/Chain/Ring

P2MP connection, flexible topology

RAN

IQ time domain and freq. domain data (Native RoE only)

Any functional split

Proprietary Performance
Enhancement Support

LimitedYes

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9IEEE 802.1 TSN Technology Overview
Converged network for Information Technology (IT) and Operational
Technology (OT) in LAN
Multi profiles for different applications – Video, Factory, Telecom…

Time synchronization:
Timing and Synchronization(802.1AS) includes a profile of IEEE
1588
Bounded low latency:
Credit Based Shaper (802.1Qav)
Frame preemption (802.3br &802.1Qbu)
Scheduled Traffic (802.1Qbv)
Cyclic Queuing and Forwarding(802.1Qch) Asynchronous Traffic
Shaping (P802.1Qcr)

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Synchronization
Reliability

Ultra reliability:
Frame Replication and Elimination(P802.1CB)
Path Control and Reservation (802.1Qca)
Per-Stream Filtering and Policing(802.1Qci)
Reliability for time sync (P802.1AS-Rev)

Latency
Resource Mgmt

TSN Standards
Zero congestion loss

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Dedicated resources & API
Stream Reservation Protocol (802.1Qat)
TSN configuration (P802.1Qcc)
YANG (P802.1Qcp)
Link-local Registration Protocol(P802.1CS)

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Eth based Solution – Prototype Test
 Encapsulation of CPRI frame Multiplexing with FlexE

PW for CPRI

FlexEthSubrateBonding

EthCPRI

MAC
Shim

Eth

3 × CPRI 7（9.8304Gbps）

encapsulation

IFMAC

Channelized

40GE（NNI）

FPGA based, only lab POC
2016 – Lab POC, CPRI over Eth via PW(same as E1 PW), FlexEth;
No bandwidth saving, device needed when CPRI and eCPRI at the same site
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PHY11WDM Based Solution – FO/Colorless Module
Centralized WDM Solution(Under R&D)

Current FO Solution

AAU

passive

Shared laser (10 directions)

2x50G

15*Any Port
GE~10G

O/E

Map/
Demap

OTN
OH

oDSP

multiple wavelengths

E/O

BiDi…
AAU

Colorful IF

Colorless SFP+

Cloud BB

Optical distribution
box

Colorless SFP+(10G/25G)

OSN 1800•Full Outdoor, w/osite configuration
•w/o optical layer
commissioning•BBU

Bi-Di, with 1+1
protection

Compatible with CPRI/eCPRI – transparent for any traffic
Simple, low power consumption and save site fibers – without device
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GC SiteShared laser

PON Based Solution–– Optimized DBA Algorithm

Current NG-PON DBA ：350~550us
PON Board - OLT

Periodic
windowing

DBA report

ONU

SR-DBANSRDBA
DBA logic

DBA Optimization for 5G：50us~100us

Controlplane

Allocation

Periodic
windowing

New Periodic
windowing
Mechanism

SR-DBANSRDBA

DBA logicDate plane

Scheduler

NSR T-CONT• Assured-DBA/Max DBA, status report before bandwidth allocation : 1-2ms.
• Fixed-DBA, no need status report, delay will be 100-200us• Periodic windowing, add delay 200-300us

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NSRDBA

LL-DBASR T-CONTTime slot

SR-DBA

DBA logic• LL-DBA, low latency DBA in future, delay will be about 50us~100us.
• Periodic windowing should have new mechanism to eliminate latency to0.

Notes: chipset and hardware must be changed tosupport 50us~100us low latency DBA
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Fronthaul Solution Summary

1
WDM - Colorless• Transparent for
CPRI/eCPRI: 4G&5GCompatible• No site device: Simple,
low power
consumption• Innovation: new
optical module

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2
Eth – RoE
•
••
•

CPRI
mapper/demapper
neededLimited functional
splitting available
Utilize the L2 switch
supply chain
Only Eth transport

••

•
•

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IP/Eth – eCPRI

4PON

Open forperformanceenhancement
Support any packet
transport
Flexible function
splittingNo support for CPRI

• Reuse the existingODN• Upgrade PON capacityand optimize the DBA
algorithm

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Thank you
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