fronthaul networks – a key enabler for...

The rules of competition in regards to Mobile Services are rapidly changing. Customers no longer select a carrier based on pricing but rather on service quality. This pushes mobile network operators to further increase radio access capacity and provide continuous network coverage. Providing a superior user

experience is the most effective way to keep churn at a low rate and attract new users.

However, growing capacity and completing coverage in mobile networks is limited by availability of spectrum. This is addressed by LTE-Advanced, which introduces innovative radio features for highest spectral effi ciency in radio access even within overlapping cell sectors by interference coordination and radio spectrum control with multipoint connections. Technologies for reusing spectrum allow the installation of additional low power cells (“Small Cells”)

within a Macro Cell. This improves coverage and increases the overall cell capacity.

Such advanced technologies, however, add additional requirements to the network interconnecting base stations and the Evolved Packet Core (EPC). The inter-cell communication needs to meet more stringent demand for delay and delay variation. In addition, the mobile backhaul network (MBH) must be capable of distributing phase and time information in a highly accurate manner. Those requirements can hardly be met by existing mobile backhaul networks, creating a challenging task for either migrating existing networks or complementing the installed base with alternative concepts.

This paper describes the latest LTE features for spectral reuse and maximizing cell capacity. It outlines the impact on the mobile backhaul network and introduces a fronthaul network as an innovative approach to connecting a rapidly increasing number of Small Cells in a future proof and highly

effi cient way. Guidance for best practice fronthaul network implementation is provided.

Increasing Capacity in the Radio Access Network

As mobile operators extend network capacity they install additional cells within the coverage of a Macro Cell as shown in Figure 1. In a heterogeneous network scenario those additional cells could be a different mobile technology operated in a different spectrum (e.g WiFi) or it might be low power “Small Cells” using the same mobile technology operating in the same spectrum as the Macro Cell.

In case of the latter, effi cient radio resource management must avoid inter-ference that compromises the capacity benefi t of installing additional base stations. LTE is designed to handle interference from neighboring cells and

TECHNOLOGY WHITE PAPER

Fronthaul Networks – a Key Enabler for LTE-Advanced

Author: Ulrich KohnADVA Optical Networking

ADVA Optical Networking © All rights reserved.

The latest LTE features for spectral reuse and maximizing cell capacity.

WHITE PAPERFronthaul Networks – a Key Enabler for LTE-Advanced

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introduces different technologies to avoid, mitigate or constructively benefi t from interference.

Interference Cancellation with eICIC (enhanced Inter-Cell Interference Coordination)

Inter-cell Interference coordination was introduced with LTE Release 8 and is based on optimizing transmit power levels across neighboring cells for minimum interference e.g. by lowering power for users close to the antenna sites allowing re-use of this spectrum. With LTE-Advanced Release 10 another scheme was added. With eICIC (enhanced inter-cell interference coordination) the Macro Cell frame structure’s “Almost Blank Subframes” (ABS), which are used for low power signaling purposes, are re-used by low power radio base stations which operate within the coverage area of the Macro Cell. All sites require common time and phase information in order to synchronize their frame sequence for coordinated access to commonly used time slots. Hence, availability of highly accurate phase and time information is a critical prerequisite for applying this LTE-Advanced feature.

Figure 1: Macro Cells and Small Cells operating in same spectrum with overlapping coverage

Macro Cell

Small Cell

Figure 2: Multiple use of “Almost Blank Subframes” (ABS)

ABS ABS ABS

Macro Cell Timeframes


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Interference Avoidance with CoMP - Coordinated Multipoint Transmission

There are further means to avoid interference by implementing time and space diversity technologies or by synchronizing the signal provided from several base stations.

Beam forming technologies are based on MIMO (Multiple Input Multiple Output) schemes, which spatially segment a cell and allow user terminals to operate in the same spectrum. Figure 3 depicts spectral reuse in overlapping cells by steering beams to several terminals. Such beam forming can also be achieved by combining the radio signal from antennas at different sites.

The involved sites need to coordinate their radio frequency signal in a highly accurate way, which requires phase synchronization and high-capacity connectivity with low latency.

Hence, those LTE-Advanced technologies put some additional requirements on the backhaul network. Stringent time and phase synchronization with accuracy in the order of 1µs is required for most LTE-Advanced features. In addition some schemes need high capacity inter-site communication.

Most requirements can be met by implementing high-quality time synchronization and in addition inter-cell communication using respective interfaces of the LTE architecture. Such implementation however involves signifi cant complexity.

Impact on Mobile Backhaul Architecture

The above outlined technologies allow a higher spectral effi ciency within overlapping sectors. The required interference management calls for strict coordination of access to the radio spectrum in neighboring cells. Hence, a close cooperation is required among the base stations.

The X2 interface defi ned with LTE network architecture can be used for such inter-cell coordination. With present mobile backhaul networks, this interface is frequently connected through the service edge router, which links the different Radio Base Stations with its controller or Service Gateway respectively as shown in Figure 4 with the red solid line.

Figure 3: Beam forming as a means to avoid interference

Beam forming can be achieved by combining the radio signal from antennas at different sites.

The above outlined technologies allow a higher spectral effi ciency within overlapping sectors.


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Control traffi c must be exchanged with stringent delay requirements of less than 1 ms. Each radio needs to be supplied with highly precise time/phase information with an accuracy in the order of 1µs. Location-based services demand even lower tolerance of some 100ns as phase differences among several radio signals are used to calculate the location of user equipment.

Present design practice cannot meet the delay target. Backhaul architectures which switch/route X2 closer to the base station become necessary as indicated with the dotted path in Figure 4. This, however, requires a signifi cant change in network architecture, which may result in signifi cant investment.

Time and Phase Synchronization in Mobile Backhaul Networks

Most present mobile backhaul networks are able to distribute information for frequency synchronization by either using SyncE or packed-based frequency synchronization based on IEEE1588 (Precise Timing Protocol). However, those implementations are not able to provide accurate time and phase synchronization.

There are various strategies how networks can be made capable for distribution of precise phase information. GPS receivers can be co-located with Radio Base Stations but come at high cost and are not suitable for in-door locations. Alternatively, the MBH network can be upgraded with improved synchronization distribution capability, which requires PTP mapped into Ethernet in combination with processing of time stamps within any network node by an embedded “Boundary Clock”. In many cases, such upgrades result in a rebuild of the complete network.

As Mobile Network Operators prepare their infrastructure for emerging LTE-Advanced, they analyze different strategies on how the backhaul network can provide the required functions. Favorable solutions will allow migrating rather than overbuilding the existing network. ADVA Optical Networking offers unique synchronization assurance technology for implementing

synchronization distribution in installed networks. This, however, is not covered in this White Paper, but more detailed information can be found on www.advaoptical.com.

A commercial as well as a highly attractive, technical approach for relaxing the backhaul requirements is based on re-partitioning the Radio Access Network by pooling some functions at a central site and minimizing equipment that needs to be mounted at the antenna site.

Figure 4: Inter-cell communication in LTE

Edge Router

IP/MPLSCarrier Ethernet

Typical X2 connection creates too much delay

Preferred X2 connection for lower delay

Control traffi c must be exchanged with stringent delay requirements of less than 1 ms.

ADVA Optical Networking offers unique synchronization assurance technology.


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Performing interference coordination and spectrum allocation at a central site by a common clock and time unit eliminates the need to accurately distribute synchronization information to each antenna site and relaxes the real-time communication requirements between the controlled sites. Centralized processing also increases effi ciency as overall power consumption is reduced. Installation and maintenance costs will decrease as a larger share of the equipment is installed in a controlled environment.

Centralized Baseband Processing and Fronthaul Network

A radio base station can be functionally separated into

• a Baseband Unit (BBU, sometimes also referred to as Digital Unit DU), which generates and processes a digitized baseband Radio Frequency (RF) signal

• a Remote Radio Head (RRH) aka Remote Radio Unit (RRU), which creates the analog transmit RF signal from the baseband signal and sources it to the antenna respectively digitizes the RF receive signal

With today’s Radio Base Stations, both units are integrated into a single network element. Figure 5 shows a scenario with overlapping cells in which the radio inter-cell communication is handled through the X2 interface.

Separating both units creates opportunities for network optimization. Figure 6 shows how the architecture is impacted by introducing a split radio base station. The active radio frequency unit, which is called Remote Radio Head (RRH) is connected to the pooled digital units by means of a CPRI (Common Public Radio Interface) interface. This interface was specifi ed by an industry cooperation with participation from Ericsson AB, Huawei Technologies Co. Ltd, NEC Corporation, Alcatel Lucent and Nokia Siemens Networks GmbH & Co. KG. It transports the digitized radio frequency signal as well as management and control data. The transmission network connecting RRH with BBU is called fronthaul network underling the difference with the backhaul network, which connect the DUs with the edge of the evolved Packet Core (ePC).

Small form factor Remote Radio Heads (RRH) simplify installation and reduce power consumption of active equipment at the antenna site. As the characteristic

Figure 5: Radio Base Stations use X2 interface to communicate with each other

RU

BBU

RBS

RU

BBU

RBS

RU

BBU

RBS

MBH

X2

S1


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of the RF signal is generated at the collocated, pooled Baseband Units, a tight coordination of the radio signals is achieved. Besides the cost advantages, the improved interference management translates into a higher cell utilization as well as improved quality of service.

Optical fronthaul networks form basis for the next step of innovation towards software defi ned radio access networks, which can be upgraded from one radio technology to another simply by management command. As the CPRI interface does not depend on the radio technology, a upgrade from 3G to LTE or LTE-A only increases data rate in the fronthaul transmission network. Bitrate transparent transmission allows a network upgrade without any impact on the transmission network.

Transmission between BBUs and the Remote Radio Heads will in most cases be done with fi ber systems as data rates of several Gbit/s need to be transported and distances of up to 40km need to be bridged with low latency and low jitter in the range of 10ns.

Copper and Microwave transmission systems might be an alternative, however, both technologies come with some limitations which make a wider application quite unlikely.

Although the latest microwave transmission systems are capable of transporting data at multiple Gibt/s speed, restrictions on availability of spectrum and distance limitation at high frequencies e.g. E-Band at 60/80 Ghz need to be considered. In addition, cost of scaling capacity is signifi cantly less favorable with microwave transmission making fi ber-based solutions ideal. Copper is a theoretical option as well, however, it requires highly sophisticated vectoring and bonding technologies for achieving the required data rates. Distance limitations will further reduce the relevance of this technology.

Although CPRI interfaces can be connected by grey interface and dedicated fi ber, CWDM/DWDM will improve fi ber utilization. As fewer fi bers are used, cost for fi ber provisioning is lower. Active DWDM technology can monitor the transmission network for fast and effi cient fault isolation. Resilient optical transmission improves availability while optical switching allows to implement 1:N protection of BBU units.

Figure 6: Connecting Remote Radio Heads with a pool of Baseband UnitsFigure 6: Connecting Remote Radio Heads with a pool of Baseband Units

Fronthaul Network

RRHRRHRRHRRHRRH

RRHRRHRRHRRHRRH

RRHRRHRRHRRHRRH

Centralized Baseband Processing

3

3

3

BBUBBUBBUBBUBBUBBU

BBUBBU

BBU

BBUBBUBBUBBU

BBUBBU

BBU

BBUBBUBBUBBU

BBUBBU

BBU

BBUBBUBBUBBU

MBH


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Single Fiber Working (SFW) solutions are an attractive approach for high-capacity transport in the fronthaul networks featuring low fi ber handling expenses. In addition, network sharing is supported by DWDM technology as traffi c from different wavelengths is securely isolated from each other.

Optical transmission can easily scale to higher bandwidth by increasing data rate of an optical channel or by adding additional wavelengths. This allows expanding the capacity of a network without signifi cant investment. Low fi ber attenuation allows larger distances which makes its possible to further centralize BBU pools and reduce the number of active sites in a network.

CPRI Characteristics

The CPRI interface is used to transport a digitized radio baseband signal in 2G/3G and LTE networks as well as with WiMAX. As no compression technology is applied, the line rate per carrier and per antenna becomes quite signifi cant depending on oversampling rate, resolution per sample, number of antennas per sector and sectors per antenna site. The list below shows some confi gurations with respective CPRI line rates:

Table 1: Comparing conventional base station with centralized baseband processing

Conventional Radio Base Stations

Centralized Baseband Processing

Spectral Effi ciency Moderate High due to interference coordination

Bandwidth Requirements

Moderate: 0.1…1 Gbit/s High: 1…10 Gbit/s

Interconnection Media to Antenna Site

Microwave, fi ber, copper Fiber

Synchronization Stringent phase alignment Centrally at pooling site

Inter-Cell Communication

Critical latency requirements Relaxed requirements due to co-location of BBUs; but stringent latency requirements between BBU and RRH

Installation Cost High Moderate as less equipment at antenna site

Table 2: CPRI line rates

Application Channels Antenna Confi guration CPRI Line Rates

WCDMA 4 x 5 Mbit/s 1 sector, MIMO 2x2 1228.0 Mbit/s

LTE 20 Mbit/s 1 sector, MIMO 2x2 2457.6 Mbit/s

WCDMA LTE

1 x 5 Mbit/s20 Mbit/s

3 sector, MIMO 2x2 9830.4 Mbit/s


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The CPRI signal is specifi ed with a simple multiplexing structure based on a lowest line rate of 614.4 Mbit/s. Higher capacity signals utilize multiple base streams in parallel. Hence, the CPRI signal allows aggregating of signals. Different mobile radio technologies can be transported in parallel with the same interface. Different topologies as rings, chains or trees are supported with up to 6 consecutive multiplexing stages. [2]

Resilience can be implemented by protection switching of CPRI signals or by using inherent spatial redundancy of multiple antennas (MIMO), see Figure 8showing two antennas per sector. If one RRH should fail, the sector is still covered, however without featuring MIMO.

Stringent delay and jitter requirements have to be met. The distance is limited to approximately 10km (5µs delay) with present standards [2], present technology can tolerate distances of up to 40km.

Figure 7: Antenna site featuring three sectors with 2x2 MIMO and centralized Digital Unit

Figure 8: Implementing resilience by utilizing spatial redundancy

Sector 1

Digital Units at Pooling Site / Macro Base Station SiteAntenna Site

RRH

RRH

RRH

RRH

Sector 2

Sector 3

BBUBBUBBUBBUBBUBBU

BBUBBU

BBU

BBUBBUBBUBBU

BBUBBU

BBU

BBUBBUBBUBBU

BBUBBU

BBU

BBUBBUBBUBBU

Sector 1

Antenna Site

RRH

RRH

RRH

RRH

Sector 2

Sector 3

The CPRI signal is specifi ed with a simple multiplexing structure based on a lowest line rate of 614.4 Mbit/s.


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Providing Connectivity in Fronthaul Networks

Mobile Operators have various options for connecting cell sites with the central baseband units. They may decide to install fi ber to the cell site, rent dark fi ber, share fi ber and the transmission system with another operator or lease bandwidth from a wholesale bandwidth provider. Any of those models comes with specifi c requirements for the fronthaul transmission network in regard to scalability, operational requirements, resilience and traffi c

segregation.

The following operational models shall be outlined and favorable technical solutions will be discussed:

• Self-Provided Fronthaul Network: Mobile Operator owns/leases fi ber and connects pooled DUs with RFU through owned fronthaul network

• Wholesale CPRI Connectivity Provider offers CPRI connectivity service

• Fronthaul Network Sharing: Various MNOs share antenna sites and pooling sites. A shared fronthaul network needs to isolate traffi c and provide means to manage performance per connection

The fronthaul capacity demand depends on site confi guration such as number of antennas, available spectrum, MiMO confi guration and mix of mobile technologies such as 2G, 3G, 4G and WiFi/WiMAX. Hence, the number of CPRI interfaces as well as CPRI capacity will vary signifi cantly across a mobile network but also among mobile networks.

Self-Provided Fronthaul Network

A typical fronthaul network scenario is shown in Figure 9. A passive DWDM/CWDM solution connects the centralized pool of baseband units with the antenna sites providing one CPRI channel per sector. Various topologies are supported as chains and trees. Rings allow implementing protection schemes either by using

Figure 9: Passive Fronthaul Network

Mobile Operators have various options for connecting cell sites with the central baseband units.

BBUBBUBBUBBUBBU

BBUBBUBBUBBUBBUBBU

BBUBBUBBUBBUBBUBBU

RRH

RRH

RRH

RRH

RRH

RRH

RRH

RRH

RRH

RRH

RRH

RRH

RRH RRH

RRH

RRH

RRH

RRH

Fronthaul Network

SFPSFPSFPSFPSFPSFPSFPSFPSFP

SFP

SFP

SFP

SFP

SFP

SFP

SFP

SFP

SFP


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spatial redundancy or optical switching. Today, most operators do not consider resilience with the transmission network. This might, however, change in the future as operators move towards more centralized architectures increasing the number of centrally located BBU units which aggravates the impact of fi ber breaks.

As this approach is based on colored interfaces plugged into radio equipment, the fronthaul network is managed by the radio access network.

The main advantages of such passive WDM solution are:

• Cost effective: no fully-blown transponders are required which reduces spares and simplifi es installation.

• Simple to setup: There are only few components in the system and connection is very straightforward.

• Low latency: A limited amount of additional HW is added in this confi guration thereby guaranteeing the lowest possible latency.

• Low power and space consumption: The network in essence only consists of pluggable modules (SFP, SFP+, XFP, CFP, etc) and passive fi lters. There- fore the required power consumption and space for making the connection is minimal.

• Purely passive – good MTBF: Because of the minimum amount of components in the system the FIT rate is very good.

However, there are several disadvantages to passive WDM systems that have prevented these systems from catching ground in the access domain

• No optical surveillance: Perhaps the most critical point for deployments in the access domain might be that with passive WDM networks no optical surveillance is possible. This makes root cause analysis and network management cumbersome.

• No performance monitoring available: performance monitoring is important for guarantying certain service level agreements.

• Finally, the usage of tunable SFP+ and tunable XFP are not possible in case 3rd party OEM equipment is used for the OLT or ONU that cannot set the wavelength of the tunable pluggable.

Frequently, operational responsibility for transmission networks and radio networks are split in an organization due to very different competence requirements necessary to maintain those technology domains. Hence, operational support tools should be aligned with such organizational separation and demarcation devices should be applied for fast and effi cient fault isolation.

Optical performance assurance provides signifi cant value as it allows the independent monitoring of the optical connectivity network but also provides support with confi guration and provisioning of CPRI connections. A solution based on ADVA Optical Networking’s patented Optojack™ technology is

shown in Figure 10.

Optical performance assurance provides signifi cant value.


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Optojack™ provides a communication interface integrated into pluggables and allows setting up a transparent communication channel. The communication channel is realized by over-modulating the data with a low bit-rate electrical subcarrier. It should be noted that the over-modulation does not affect the optical performance of the pluggable.

The optical signal is monitored by Optojack™-enabled SFPs, which communicate with a central “tracer”. This solution allows a radio vendor independent CPRI connectivity service assurance without the need to use a more complex radio OSS system for low layer connectivity purposes. In addition, Optojack™ provides auto-wavelength confi guration if tunable SFPs are applied.

Wholesale Bandwidth Provider

Laying fi ber is quite an expensive effort in metropolitan environments. Thus, Mobile Operators are interested in leasing CPRI connectivity from a Wholesale Bandwidth Provider. Those Wholesale Providers might be incumbent or competitive operators but could also be a regional corporation

such as utilities or property owners sharing one characteristic: they own fi ber and can provide connectivity among cell sites in an urban/metropolitan environment.

As the number of sites can be quite signifi cant, automated means for provisioning but also assuring service quality are essential. A favorable implementation of a fronthaul solution operated by a Wholesale Bandwidth Provider is shown in Figure 11.

The Mobile Operator hands off a grey CPRI signal while the Wholesale Bandwidth Provider translates this into distinct wavelengths. The transponders can align with different CPRI bitrates and tunability allows changing connectivity in a hard-wired optical multiplexing scheme. Service quality is assessed at each demarcation point for service assurance but also for troubleshooting purposes.

Figure 10: Active Fronthaul Network Solution Featuring Optical Monitoring

Laying fi ber is quite an expensive effort in metropolitan environments.

BBUBBUBBUBBUBBU

BBUBBUBBUBBUBBUBBU

BBUBBUBBUBBUBBUBBU


RRH

RRH

RRH

RRH

RRH SFP

SFP

SFP

TracerTracer

RRH

RRH

RRH

RRH

RRH SFP

SFP

SFP

RRH

RRH

RRH

RRH

RRH SFP

SFP

SFP

SFP

SFP

SFPSFP

SFP

SFP

SFP

SFP

SFP


Fronthaul Network


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As environmentally hardened equipment is applied at the antenna site and size restrictions apply, fronthaul transmission solutions are designed for this specifi c application.

Fronthaul Network Sharing

By sharing the same feeder fi ber a common fronthaul network can be used by different operators running own radio equipment at the cell sites. The main difference to the above discussed scenarios is with the number of channels required to connect each site. Higher channel count systems are more favorable for those applications. The connectivity network might be operated by either one of the Mobile Network Operators or might be provided by a Wholesale Bandwidth Provider. In any of those cases, there is a need for clear service demarcation, which favors a transponder-based backhaul solution as outlined in the above paragraph.

Emerging Technologies

Mass deployment of Small Cells demand cost effi cient and easy to handle transmission networks. Fronthaul DWDM transport solutions therefor should consist of a reduced set of components to minimize logistics and simplify network

Figure 11: Active Fronthaul Network

Table 3: Optical transmitters in DWDM systems

Seeded Refl ective Transmitter Tunable Laser

Channel Countper Fiber

Medium (~40) High (> 80)

Wavelength Generation

ASE + optical fi lter Tunable laser

Bit Rate Medium (some Gbit/s) High (10 Gbit/s and above)

Favorable Application

Limited capacity requirements High channel count, high capacity per channel

BBUBBUBBUBBUBBU

BBUBBUBBUBBUBBUBBU

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RRH

RRH

RRH

RRH

RRH

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RRH

RRH

RRH

RRH

RRH

RRH

RRH RRH

RRH

RRH

RRH

RRH

TRPTRPTRPTRPTRPTRPTRPTRPTRP

SFPSFPSFPSFPSFPSFPSFPSFPSFPSFPSFPSFPSFPSFPSFPSFPSFPSFPSFPSFPSFPSFPSFP

RRH SFP

RRHRRH SFP

RRHRRH SFP

TRP

TRP

TRP

RRH SFP

RRHRRH SFP

RRH SFP

TRP

TRP

TRP

RRH SFP

RRHRRH SFP

RRHRRH SFP

TRP

TRP

TRPTRP

TRP

TRP

TRP

TRP

Fronthaul Network

TRP – Transponder


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design. Different technologies can be applied to replace optical transmitters with distinct wavelengths by components which can be used for any wavelength. Table 3 provides a comparison of two presently discussed approaches.

Seeded Refl ective Transmitters

Distinct wavelengths in the transmission network can be generated by seeding a refl ective semiconductor optical amplifi er (RSOA) with an external wavelength source. Figure 12 shows a fronthaul transmission network with an OLT (Optical Line Termination) at the central BBU pool and an ONU (Optical Network Unit) at the cell site. A spectrally broad EDFA ASE (Amplifi ed Spontaneous Emission) signal is fi ltered in a Mux/Demux device (2,3) and amplifi ed as well as modulated with the upstream data signal in the RSOA (4). Eliminating the need for a tunable transmitter at the antenna site simplifi es installation and logistics.

Remotely seeded architectures are suited for line rates up to some Gbit/s as channel capacity is limited by dispersion and signal to noise ratio. Various technologies are discussed which shall overcome limitations of remotely seeded architecture as replacing ASE broadband sources by Multi-Wavelength Lasers (MWLs) or re-using the downstream signal and re-modulating it at the ONU by means of specifi c modulation schemes.

However this adds more complexity to the system and thereby increases the component cost. Apart from the limited channel capacity, a network with optical amplifi cation and re-modulation is sensitive to refl ections on the fi ber link. This puts stringent requirements on the quality of the splices and cleanliness of the connectors.

Figure 12: Auto-tunability by remotely seeding

MUX/DEMUX

ONU OLT

Reflective SOASFP package

1: Initial ASE(without locking)

SFP

RX

RSOA(TX)

TX data

RX data ASE sourceLaser source

Reflective elementLaser source

2: EDFA ASE(send towards RSOA)

3: sliced ASE spectrum(after AWG)

4: RSOA locks on sliced ASE frequency

e.g.AWG


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Tunable Laser

Tunability of laser sources allows using a single transmitter component for any WDM channel. Those components can replace fi xed wavelength sources without impacting design rules or adding further requirements such as lower levels of refl ection on the fi ber; hence they do not restrict the fl exibility of a DWDM system and allow to be applied with installed fi ber infrastructure. However, means to tune and monitor the wavelengths need to be applied.

Figure 13 shows a favorable application of tunable lasers in a SFW (Single Fiber Working) confi guration. Single Fiber Working systems reduce fi ber handling effort during installation but also maintenance and repair. They are preferably applied in situation with high cost of fi ber or very limited availability of spare fi ber.

Optojack™ technology is applied to confi gure and manage the bidirectional transmission system. This technology provides a non-intrusive communication from the OLT site with the ONU site and means to monitor the up- and downstream spectrum. Self-confi guration of the wavelengths even without need for addition active equipment other than Optojack™ enabled pluggables makes this technology very attractive for mass deployment.

ADVA Optical Networking is working with EU funded research projects on optimizing fronthaul architectures. Various technologies are evaluated commercially as well as technically.

While today passive solutions or transponder-based solutions are effi ciently applied, more advanced technologies as outlined above will further improve economics of fronthaul networks. A higher channel count, increased capacity per channel as well as improved power budgets will support further centralization of Baseband Units reducing the number of active sites in a network. However, this will require technologies such as tunable lasers to

become available as low cost pluggable modules. ADVA Optical Networking product strategy is closely aligned with this technical innovation.

Figure 13: Fronthaul network featuring SFW (Single Fiber Working) wavelength tunability and optical performance monitoring

OLT at central BBU poolONU at antennasite

Remote Node

Cyc

lic A

WG

TSFP+TSFP+RX

TSFP+TSFP+RXTX

AWG

AWG

AWG

AWG

AWG

TXSFP+

RX

TXSFP+

RX

Tapcoupler

Tunable SFP

More advanced technologies will further improve economics of fronthaul networks.


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Summary

Advanced mobile technologies put additional requirements on backhaul architectures. The introduction of a fronthaul network provides various advantages as it relaxes backhaul delay requirements and improves re-use and utilization of the scarce radio spectrum.

Line rates of digitized RF baseband signals make optical transmission systems a perfect fi t in fronthaul networks. DWDM technology minimizes fi ber handling cost and improves fi ber utilization. Active systems provide a demarcation between Radio and Transmission system, which simplifi es operation and eases fault isolation.

Different transmission network architectures allow aligning with operational models such as wholesale, self-provided networks as well as network sharing. Various photonic technologies can be applied to optimizing applications with stars, rings and chains and support more centralized baseband processing architectures. This simplifi es the radio access transport network and reduces the number of active sites.

ADVA Optical Networking specializes in transmission network solutions for operators, enterprises and the public sector. Based on the competence of well recognized experts in photonic transmission and the widely applied FSP 3000 DWDM/CWDM portfolio, ADVA Optical Networking has developed fronthaul transmission solutions, which allow operators and wholesale bandwidth providers

to capitalize on the signifi cant benefi t of central baseband processing with BBU pooling in a Small Cell deployment. Optojack™ – a unique technology for simplifying confi guration and non-intrusive monitoring – meets operational requirements in a most favorable way. Independent from topology, line rate and channel count, an optimized solution is provided.

Optojack™ meets operational requirements in a most favorable way.


For more information visit us at www.advaoptical.com

ADVA Optical Networking North America, Inc.5755 Peachtree Industrial Blvd.Norcross, Georgia 30092USA

ADVA Optical Networking SECampus Martinsried Fraunhoferstrasse 9 a 82152 Martinsried / Munich Germany

ADVA Optical Networking Singapore Pte. Ltd. 25 International Business Park#05-106 German CentreSingapore 609916

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About ADVA Optical Networking

ADVA Optical Networking is a global provider of intelligent telecommunications infrastructure solutions. With software-automated Optical+Ethernet transmission technology, the Company builds the foundation for high-speed, next-generation networks. The Company’s FSP product family adds scalability and intelligence to customers’ networks while removing complexity and cost. Thanks to reliable performance for more than 15 years, the Company has become a trusted partner for more than 250 carriers and 10,000 enterprises across the globe.

The ADVA FSP 3000

ADVA Optical Networking’s scalable optical transport solution is a modular WDM system specifi cally designed to maximize the bandwidth and service fl exibility of access, metro and core networks. The unique optical layer design supports WDM-PON, CWDM and DWDM technology, including 100Gbit/s line speeds with colorless, directionless and contentionless ROADMs. RAYcontrol™, our integrated, industry-leading multi-layer GMPLS control plane, guarantees operational simplicity, even in complex meshed-network topologies. Thanks to OTN, Ethernet and low-latency aggregation, the FSP 3000 represents a highly versatile and cost-effective solution for packet optical transport.

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