How to pick thebest Fronthaul
technology foryour C-RANnetwork

Contents

02

Introduction

03

Centralized-RAN

04

Passive Optical Fronthaul

05

Packet Fronthaul

06

Microwave-based Fronthaul

07

Ericsson – comprehensive transport portfolio

08

Conclusion – use the best solution

Introduction
Radio Access Networks (RAN) are evolving rapidly with different architecture
options varying from Distributed-RAN (D-RAN) to Centralized-RAN (C-RAN)
in both purpose built and cloud networks. Each has different benefits andspecific requirements. In this paper we will be focusing on how to build thefronthaul network for C-RAN architectures.

3

Ericsson | How to pick the best Fronthaul technology for your C-RAN network

Centralized-RAN
The C-RAN architecture is characterized byconnecting remote antenna sites via afronthaul network to centralized basebands
or vDUs in a hub location. In dense urban
areas, with access to dark fiber, centralizing
and pooling the baseband units to an
aggregation site can be a good option. It
allows for tighter and easier coordination
between the basebands resulting in asuperior radio performance, key to app
coverage and user experience. It also
reduces network costs by simplified

centralized operations and reduces space,
power and cooling requirements at the cellsite.
The network “in front” of the baseband
towards the remote radio unit is called thefronthaul network. The prevalent fronthaul
protocols used are the common public radio
interface protocol (CPRI) and the newer
enhanced CPRI protocol (eCPRI). CPRI is
TDM-based and constant bitrate,
independent of actual user traffic. CPRI

defines line bit rate options 1 (614.4 Mbps)
through option 10 (24.3 Gbps) with CPRI-3(2.5 Gbps), CPRI-7 (9.8 Gbps) and CPRI-8(10.1 Gbps) being the most deployed in theNorth American market. The new eCPRI
protocol introduced in 2017 is a packet
interface and is up to 10x more efficientcompared to CPRI from a transport
perspective since it scales in proportion touser traffic. The eCPRI radio interfaces used
are either 10 GE or 25G E.

Figure 1: Fronthaul network

Fronthaul options
When building your fronthaul network, youneed to use the right tool for the job. Theoptions in the fronthaul toolkit include:• Passive Optical Fronthaul• Packet Fronthaul• Microwave-based Fronthaul• Any combination of above solution(where applicable)

The optimal solution depends on a numberof factors such as fiber availability, CPRI vseCPRI radios, site types, distance between
radio and the hub etc.
Traditional CPRI is typically transported
over fiber using Dense Wave Division
Multiplexing (DWDM) in which multiple
CPRI services are optically multiplexed intoa single fiber strand to reduce fiber costs.

An emerging complementing solution istransporting CPRI over packet using either
Radio Over Ethernet (ROE) encapsulation orconverting CPRI to eCPRI. In the following
sections we will explore the Passive
Optical Fronthaul options as well as Packet
Fronthaul and Microwave-based Fronthaul
options. In real deployments, you will see a
combination of several technologies to fulfill
the needs of a specific site.

4Ericsson | How to pick the best Fronthaul technology for your C-RAN network

Passive OpticalFronthaul
Passive optical fronthaul is ideally suitedfor deployments optimized for space andpower (e.g. small cells), as it is small andvery cost effective. Flexible compact designallows it to be mounted out of sight in a pole,
handhole or small cell enclosure. Passive
fronthaul does not require any additionalpower, colored optics are simply plugged
directly into the radio and baseband andconnected to an optical add/drop filter.

The filters are protocol and bit-rate agnostic
and can transport any mix of CPRI, eCPRI,
and/or Ethernet service with up to 600 Gbps
capacity on single fiber strand. Pluggable
colored optics based on SFP+ and SFP28
technology provide connectivity at 10Gbps and 25 Gbps through fixed and fulltunable variants. For optical fault andperformance monitoring you must rely onon the radio and baseband to monitor thepassive optical infrastructure andcoordinate between RAN and transportorganizations. Passive fronthaul also
requires good planning, administration andinstallation to ensure that the ports andcolors align correctly. Passive Fronthaul
portfolio includes 9 pizza box/enclosure
variants: figure 2 shows the compact
Fronthaul 6585 with integrated DWDM
filter.

Figure 2: Passive Fronthaul 6585 outdoor IP68 box
with OAD-9-S Optical Add/Drop filter

Table 1: Passive optical Fronthaul Benefits and Challenges

Passive Optical Fronthaul Benefits

Passive Optical Fronthaul Challenges•••••••• No demarcation points between transport andradio• Limited management capabilities• Requires disciplined installation and operations
practices

Compact in size, full outdoor remote applications
No additional power requiredLower cost
Faster permitting
Rail, pole, wall, strand or handhole mountFlexible support of many fiber architectures
Protocol and bit rate agnostic

5Ericsson | How to pick the best Fronthaul technology for your C-RAN network

Packet Fronthaul
Packet fronthaul is based on an Ethernet
circuit between the radio and the baseband.
It is managed just like any other ethernet
service, providing the stringent latency andsynchronization requirements are met.
For larger macro sites and street sites, it
typically uses a single redundancy grey
100 Gbps connection between the radio
and hub location. Packet fronthaul circuits
can connect any radio to any baseband
using flow-through provisioning with theadditional benefit that the provisioning
system becomes the “database of record”
tracking tens of thousands of connections,
between all radios and all baseband ports.
In existing networks there will be a mix of
CPRI and eCPRI radio solutions and to beable to capture all benefits with apacketized Fronthaul network there is aneed to handle the installed base of CPRI
radios using packet fronthaul gateways.

Ethernet (RoE) or converted into eCPRI
by using a conversion function on theradio signal carried in CPRI. RoE is more
RAN vendor agnostic and uses a bookended encapsulation/decapsulation
function to map the constant bitrate
CPRI into ethernet packets at the radioand baseband locations. The function
is similar to circuit emulation of TDM
services. RoE can provide up to 20%
bandwidth saving with line code removal
for low speed CPRI interfaces.
CPRI to eCPRI conversion at the antennasite can provide a substantial 60%80% bandwidth reduction comparedto RoE. At the C-RAN hub, the eCPRI
traffic is connected directly to thebaseband without requiring an additional
conversion step. The conversion mode isspecific to the radio type and RAN vendor.
Most sites will have a combination ofCPRI and newer eCPRI radios. Packetfronthaul supports native eCPRI, RoE
and/or eCPRI conversion to adapt todifferent antenna sites situations. Inaddition, some operators may choose toleave older basebands (e.g. 3G) at the
remote site, in which case transport of thebackhaul interface can also be supported.
Critical to packet fronthaul is the qualityand distribution of both frequency andtime/phase synchronization acrossthe transport network. The time errors
incurred across each hop will determine
which radio capabilities can be supported.

Traditional CPRI radio protocols can beeither encapsulated and mapped over
Ethernet frames using Radio overFigure 3: Router 6673 Fronthaul Gateway supporting RoE and CPRI conversion

Table 2: Packet Fronthaul Benefits and Challenges

Packet Fronthaul Benefits

Packet Fronthaul Challenges• Radio and enterprise services over same Ethernet facilities• End to end flow-through provisioning• Better circuit inventory management• Flexible radio to baseband cross-connections for
future baseband pooling scenarios• Reduces costly tower climbs• Clear demarcation between transport and radio• Active solution requiring space and power atantenna site• Stringent synchronization, QoS and timing
requirements• Adds some latency compared to WDM
Fronthaul solutions

6Ericsson | How to pick the best Fronthaul technology for your C-RAN network

Microwave-based
FronthaulHigh capacity 10 Gbps microwave using
E-band (70/80 GHz) can be used for sites
without fiber access, or as a temporary
solution until fiber is available.

With Dual polarization and XPIC – Cross
Polarization Interference Cancellation –you can create 20 Gbps links using a single
antenna.

Packet fronthaul using eCPRI is very
bandwidth efficient and well suited formicrowave.

Typical uses cases are small cells in cities
where trenching a fiber under the sidewalk
is cost prohibitive and time consuming.

Figure 4: MINI-LINK 6355 E-band
microwave

Table 3: Microwave Fronthaul Benefits and Challenges

Microwave Fronthaul Benefits

Microwave Fronthaul Challenges• Quick time to market• Short ROI compared to fiber• All-outdoor node

• Antenna line-of-sight• Maximum capacity 20 Gbps/antenna• Maximum up to 3 km distance7

Ericsson | How to pick the best Fronthaul technology for your C-RAN network

Ericsson – comprehensivetransport portfolio
The Ericsson transport portfolio offers acomprehensive selection of products andsoftware for any of the described
fronthaul deployment options while
managed by the same Ericsson Network
Manager (ENM) as the radio network.

Additionally, the Ericsson Transport
Automation Controller can be used toprovide advanced analytics andautomation for microwave, IP and optical
fronthaul networks using AI and machinelearning.

Passive Optical Fronthaul
The Fronthaul 6000 portfolio supports awide variety of DWDM passive filter
options which can be installed in different
indoor/outdoor enclosures. The remoteunits can be combined with several RRU

models along the common rail system or
directly backpacked to them.
Fronthaul 6000 allows a diverse
assortment of fiber architectures such as
point-to-point, chains and hub and spoke.

Packet Fronthaul
The Router 6000 portfolio offers both
CPRI to eCPRI conversion and CPRI to
RoE encapsulation combined with bestin-class synchronization quality andfeatures.

It has advanced QoS capabilities to support
different radio and enterprise traffic types
at the same time.

Microwave Fronthaul
The MINI-LINK 6355 uses the E-band
frequency and is a complete all-outdoor
node, providing fast time to market.

It supports up to 2x10 Gbps eCPRI packet
fronthaul using a single antenna. Three
25GE interfaces and 2x output power
improve the performance.

8Ericsson | How to pick the best Fronthaul technology for your C-RAN network

Figure 5: Ericsson - comprehensive transport portfolio

Conclusion – use the best solution
Centralized RAN architectures provide superior radio performance while reducing network cost in dense urban areas. Different transport
solutions can be used to build the fronthaul network by combining optical, packet and microwave options depending on the specificneeds. Each technology option has its benefits and challenges. Ericsson’s comprehensive transport portfolio allows you to pick the best
tools for your network needs.

Table 4: Fronthaul deployment scenarios

Fronthaul option

Typical deployment scenario

Passive Optical FronthaulRadio deployments which need to have a small remote footprint
and a fast installation and commissioning.

Packet Fronthaul

Flexible solution for macro sites and street sites and allowing
future compute resource pooling.

Microwave Fronthaul

For small cell sites where there is no fiber available in a timely
matter or fiber costs are too high.

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