Next Generation Mobile Backhaul Solutions by STRATEX

9/10/2008 Next_Generation_Mobile_Backhaul_Solutions.doc Page 1 of 18

Headquarters Harris Stratex Networks, Inc.

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Next Generation Mobile Backhaul Solutions ETSI Base stations that can connect devices at up to 50 Mbit/s or more will be operational within the next few years. For the backhaul network the extra capacity needed and the mix of services will require changes in the technology used – IP/Ethernet will become the transport technology of choice.

This paper introduces the technologies for next generation backhaul networks, and the connection and management solutions provided by Eclipse Carrier Ethernet over Wireless platforms from Harris Stratex Networks.

Introduction Typically a small number of E1s has been sufficient to service 2G and 2.5G base stations, but with the data capacity needed for advanced 3G and 4G HSPA/LTE applications, new technologies and strategies are required.

This need for more capacity must be provided more intelligently, and more efficiently, especially so where the backhaul networks are, or will be required to support multiple services and customers – not just cellular mobile, and not just one operator. There is also a need to ensure service continuity for old and new technologies, given that operators will want to maximize investments in existing 2G/3G infrastructure.

Going forward, the most cost effective backhaul technology to deliver more capacity, more intelligently, is Carrier Ethernet. It provides the scalability, flexibility and QoS features needed to provide a complete solution – from the core MSC to the base stations. It is also the ideal tecnology for use in MPLS or PBB-TE converged networks, where their per-hop behaviour capabilities can provide new efficiencies in the transport of different types of traffic - for different customers.

In networks where wireless provides the backhaul, these developments raise a number of issues. For example, how do you upgrade wireless connections to deliver more capacity? Do you simply increase the capacity of current TDM links, do you overlay with Ethernet to deliver the extra capacity, or do you move to an all-Ethernet solution?

Whichever way is forward, there is a cost efficient solution using Eclipse. Of special note is that one Eclipse node now supports up to six links, and a programmable total nodal throughput of over 1 Gbit/s Ethernet and up to 100xE1 or 2xSTM1.

More Capacity The expected global growth of mobile broadband data services through EDGE/HSPA/LTE evolution will see data traffic exceeding voice within a relatively short period of time. This projection assumes that the cost to access mobile data closely aligns with subscriber expectations for accessing data via wired or WiFi connections. Certainly, the cost of mobile data to subscribers must be lower than for voice for the same data bandwidth, which means operator revenues will be uncoupled from the traditionally linear returns on provisioning for voice growth. Hence operators must implement more cost-efficient solutions for delivering more network capacity.

The mobile data

evolution is

precipitating

massive changes

in mobile network

capabilities and

infrastructure.


Copyright © 2008 Harris Stratex Networks, all rights reserved. Some features are subject to availability.

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Figure 1. The Uncoupling of Voice and Data Revenues

This need for more capacity brings pressure on the backhaul network, where instead of current 2xE1 / 4 Mbit/s connections per 2G BTS, the 3G data revolution is expected to require from 10xE1 or 20 Mbit/s within 3 years, with some city sites as high as 50 Mbit/s. For 4G/LTE, figures as high as 100 Mbit/s have been forecast.

Base Station Readiness

Base stations are now becoming available with TDM and Ethernet access interfaces, giving operators the choice of one or both technologies. However, in most networks it is expected that the rollout of Ethernet-capable base stations will complement an installed base of TDM-only base stations, meaning that for the medium term at least, there will be a mix of TDM and Ethernet in the backhaul. Ultimately, with the roll-out of LTE, an all Ethernet backhaul is considered a must.

Ethernet versus TDM

It is as well to mention some general advantages of packet-based IP/Ethernet over that of circuit-switched TDM transport at this point; advantages of cost, flexibility, scalability, and quality of service (QoS).

• Cost: As the protocol of choice for Internet and business-based intranets, it’s extremely wide usage means it is better supported by network operators and the manufacturing and support industries. Ethernet delivers more cost-effective bandwidth than other technologies.

• Flexibility: Ethernet supports speeds from 1 to 10 Gbit/s in 1 Mbit/s steps. In a backhaul network it means Ethernet can provide an end-to-end solution from the BTS to the network core - gone are the needs to consider PDH connections to an expensive SDH core. Ethernet also supports easy convergence of mobile backhaul with other network applications on in-house or third-party networks.

• Scalability: Ethernet readily lends itself to servicing many 100,000s of individual services over local, metro, national and international connections.

• QoS: Ethernet supports operator-friendly prioritization of traffic. If bottlenecks occur, high priority voice data can be given right of way over lower priority and non-real-time data services.

The bottom line is that Ethernet is considered the way forward for a data-driven expansion of the mobile backhaul network. And with carrier-grade performance now on offer from some suppliers, reliability and availability of Ethernet at least matches that on offer from traditional TDM transport technologies.

Carrier Ethernet

is the technology

for next

generation

backhaul

networks.



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More Intelligence We have mentioned the Ethernet benefits of cost, easy scalability, flexibility and QoS. In this section we introduce technologies that add intelligence to the way capacity is provided and managed in the network, such as mixed mode, pseudowires, MPLS / PBB-TE, bandwidth optimization, traffic aggregation, and IP based OAM for end-to-end traffic and performance management.

Some, like mixed-mode, pseudowires and network synchronization are key considerations in migrating from TDM to Ethernet. Others like MPLS and PBB-TE are particularly relevant to efficient and robust transportation in a converged network.

Mixed Mode Mixed mode is about side-by-side transport of TDM and native Ethernet data; the overlaying of a TDM network with Ethernet, where Ethernet is used to meet the rapidly growing data demand.

Such a strategy has merit from the viewpoint of maximizing the use of existing TDM infrastructure, while minimizing the risk associated with introducing a new technology. The one proviso is that such a solution must be cost-efficient; it must represent a lower cost than a switch to all-Ethernet at the outset, but at the same time support efficient migration to an all-Ethernet network when needed.

Figure 2. Mixed Mode

All-Ethernet and Pseudowires Replacing existing backhaul infrastructure with an all Ethernet solution will invariably require accommodation of existing TDM network connections. This is where pseudowires provide an answer - existing TDM services are transported end-to-end in the network on pseudowires, which operate as virtual tunnels across provider network(s) to support legacy traffic. But pseudowires do impose an overhead – typically an additional 10 to 20% is needed over and above the native TDM bandwidth.

Synchronization is also an issue. Pseudowires do not support a robust solution for transporting the timing signals needed for base station synchronization.

More capacity

must be provided

more intelligently

to maximize ROI

and minimize

disruption to

existing services.



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Figure 3. Pseudowires

Synchronization An IP/MPLS or all-Ethernet network should support transmission of the frequency and phase synchronization requirements for base stations to the standards expected for 4G implementations. Options include synchronous Ethernet (G.8262), IEEE 1588v2, NTP, and proprietary pseudowire adaptive timing solutions. GPS timing has also been promoted as a solution.

Industry feedback indicates that non-proprietary solutions are needed, particularly so in converged networks where standardized operating practices and technologies are key requirements.

Currently IEEE 1588v2 and synchronous Ethernet have the front running. IEEE 1588v2 meets requirements for precision frequency and phase synchronization, but does have some traffic loading issues. Synchronous Ethernet does not provide phase synchronization, but does provide frequency synchronization independent of traffic loading. Ultimately the two may co-exist as merged solutions with, for example, synchronous Ethernet in the core and IEEE 1588v2 in the Metro and access networks.

MPLS and PBB-TE MPLS and PBB-TE are “traffic engineering” technologies for converged networks. They are designed to speed up network traffic flow, make better use of network capacity with accommodation for a wide range of service types and bandwidth plans. They also provide improved resiliency with pre-defined failover scenarios, and support superior management and control features.

Current consensus supports MPLS in core networks, with PBB-TE in Metro and access networks, though all-MPLS or all PBB-TE solutions will have their place depending on operator preferences.

MPLS

MPLS is a mature ITU / IETF standard. It works with IP to support both layer 3 virtual private networks (VPNs) and layer 2 pseudowires. Its flexibility includes support for pt-to-pt, pt to mpt, and mpt-to-mpt (any-to-any) Ethernet Virtual Private LAN Service (VPLS).

Its operation involves setting up a specific path for a given sequence of packets, identified by a label placed in each packet. It operates with IP, ATM, and Frame Relay network-layer protocols and over transport layers that include Ethernet, SDH and PDH. As such, it is particularly suited to networks that carry different mixtures of traffic over different network connections for multiple users.

The merging of

multiple

networks,

customer

groupings,

technologies, and

services onto one

‘converged’

network offers

significant

economies of

scale.



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Essentially, traffic enters and exits an MPLS network via Provider Edge (PE) switch/routers. Ingressing traffic is uniquely labeled (tagged) based on the desired destination and quality of service, and is directed (tunneled) through the MPLS network based on this label. The label switches manage outages, congestion and differentiated (prioritized) services. At the PE egress point the MPLS label is stripped.

Figure 4 illustrates Ethernet multipoint layer 2 VPN operation over an MPLS network using the VPLS function. Ethernet services are delivered transparently between customer LANs at sites A to E. Figure 4. IP/MPLS Virtual Private LAN Service

T- MPLS

Transport MPLS (T-MPLS) is an emerging subset of MPLS. It is optimized for Metro Ethernet network applications to provide purely connection-oriented services for managed point-to-point connections. It operates on similar lines to PBB-TE.

PBB-TE

PBB-TE is an emerging standard for point-to-point connection-oriented services in Ethernet networks. It has a flatter (layer 2 only) structure compared to MPLS, to provide cost optimized solutions where a large amount of connection-oriented traffic needs to be hubbed, aggregated, and switched, such as in a Metro network.

Data Optimization Data optimization is about reducing or compressing data so that more data can be sent over a given bandwidth. Techniques include data compression based on the type of content, data reduction that reduces the number of bits needed to be transmitted, and protocol acceleration, which acts to streamline data communications at the transport layer.

An example is the use of packet and bandwidth optimization for GSM A.bis BTS links. Non-value data is removed for each voice channel, and A.bis data is extracted and converted to a packet format to deliver overall bandwidth savings of up to 50%.

Benefits include improved latency, and more efficient use of existing infrastructure to eliminate or put back the need to update a network to deliver more capacity.

Traffic Aggregation Traffic aggregation combines two or more data streams onto a common stream, and through packet statistical multiplexing achieves improvements in bandwidth utilization of about 50% over typical circuit usage. For example separate 2G and/or 3G circuit-switched connections are converted to packet-based data and aggregated (multiplexed) using the traffic aggregation capabilities of a layer 2 Ethernet switch.

Data optimization

and traffic

aggregation

techniques can

provide

significant

improvements in

bandwidth

utilization.



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When combined with data optimization techniques, overall improvements in bandwidth utilization can be as high as 4:1.

Operation, Administration and Maintenance (OAM) OAM is about end-to-end network management capabilities for fault detection/recovery, performance monitoring, diagnostics, maintenance and configuration. Relevant OAM standards for Carrier Ethernet networks are ITU recommendation Y-1731 for the services layer (UNI to UNI), and IEEE 802.1ag for the connectivity layer. The Metro Ethernet Forum (MEF) has also developed relevant standards and recommendations.

Eclipse Wireless Backhaul Solutions This section introduces Eclipse and its solutions for more backhaul capacity, more intelligently, more efficiently. In particular, it introduces the unique switch-plane and packet-plane capabilities of the Eclipse nodes that together optimize transport options for Ethernet and TDM.

• The Eclipse platforms are described, and the migration of capacity from TDM to carrier-grade Ethernet is explained.

• The spectrum efficiencies offered with adaptive modulation and co-channel operation are described, and the intelligence and capacity efficiencies offered for Core, Metro and access NGN technologies are introduced.

Eclipse Platform Eclipse platforms are optimized for building networks; not just point-to-point links. They comprise the node-based INU/INUe, and terminal based IDUs. Solutions are provided for Ethernet, PDH and SDH.

INUs for Nodes

The INUs replace the traditional terminal or single-link based approach to networking with a nodal solution. One Eclipse INU directly supports up to three links, the INUe supports up to six links. Radio paths and customer interfaces are customized by plug-in cards, now supported by two switch planes; packet and circuit. This nodal concept dramatically reduces equipment, cabling and rack space, delivers superior network flexibility and resilience, and minimizes costs.

IDU Terminals

The IDUs support single-link 1+0 or 1+1 operation. They are optimized for edge linking from an INU/INUe, or where simple IDU-to-IDU linking is required. Different models are available to support Ethernet, Ethernet + PDH, PDH and SDH.

For GigE applications the IDU GE 20x provides up to 360 Mbit/s Ethernet throughput with up to 20xE1 tribs.

With packet

switched GigE

and circuit

switched TDM on

a common

network node,

Eclipse INUs

enable unique

cost and

performance

efficiencies on

wireless networks.



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Eclipse Super PDH

Super PDHTM operates on the Eclipse circuit switch-plane of the INUs, and as the name suggests, it refers to the ability to transport up to 100xE1 over a wireless link. Depending on the capacity and bandwidth selected, modulation rates range from QPSK to 256 QAM, to provide an unmatched range of options for capacity and channel efficiency. This represents a major performance improvement over the 63xE1 maximum on an STM1 (SDH) link, or the typical 16xE1 or 20xE1 maximums of standard PDH links.

Super PDH versus SDH

In most wireless networks Eclipse Super PDH eliminates the need to have an SDH core. SDH was generally adopted because of the limiting capacity and protection options offered by traditional PDH hardware - SDH offered more capacity more robustly than PDH.

However, Eclipse Super PDH means that these reasons for installing an SDH core in a backhaul network are no longer valid for wireless. Super PDH provides a complete network solution for star and ring topologies all the way to the core, and does so at a much lower cost when compared to an SDH+PDH solution.

• In a wireless backhaul network, a single technology is the logical choice where it provides a complete solution – especially so when it also provides significant cost and performance benefits over other options.

• If, however, SDH is needed in the wireless backhaul, Eclipse also delivers with link options of STM1 and 2xSTM1.

Eclipse Ethernet Eclipse links support native GigE or FastE Ethernet connections, with or without companion TDM traffic for mixed mode requirements.

• For many legacy PDH networks, operators are expected to overlay with Ethernet to provide the extra capacity needed to support data-based services; existing voice connections will be transported using legacy TDM links, with the burgeoning data traffic on an Ethernet overlay.

• Links will be expected to transport both TDM and Ethernet traffic natively. Moreover, there will be an expectation that the migration from TDM-only to TDM + Ethernet, and ultimately to all-Ethernet, will be straight-forward, flexible and cost-efficient.

This is what Eclipse is about. With both circuit and extended packet switch-planes, Eclipse INUs enable optimized native mixed mode solutions. For example, adding Ethernet to a Super-PDH link simply requires installation of a GigE or FastE plug-in, at which point an operator can locally or remotely configure the capacity split between PDH and Ethernet in E1 or 2 Mbit/s steps using the Liquid Bandwidth feature on the circuit switch-plane. It means Ethernet can be activated when and where needed in the network with minimum disruption, lowest cost and no risk.

Then when more data capacity is needed, the extended packet plane capability is introduced using plug-in cards. When coupled with Eclipse adaptive modulation, aggregation and CCDP capabilities, one Eclipse node supports multiple link connections with a combining capacity of more than 1.4 Gbit/s, with or without legacy PDH circuits.

• One Eclipse Node supports up to six links.

• Links can be configured to 360 Mbit/s true Ethernet throughput. Note that Harris Stratex uses layer 2, RFC 2544 rated throughput figures, not the layer 1 bit-rate figures used by some vendors to inflate their specs to 400 Mbit/s and beyond.

Super-PDH

supports capacity

migration from 5x

to 100xE1 using

the circuit switch

plane. The same

plane also

supports Ethernet

migration from 10

to 200 Mbit/s.

Ethernet is

supported on both

the circuit and

packet switch

planes. The

circuit switch

plane supports

TDM and

Ethernet; the

packet switch

plane is specific to

Ethernet.



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• Links can be configured for PDH and Ethernet using Liquid Bandwidth.

Figure 5 illustrates the packet and circuit switch plane architecture. Figure 5. Eclipse INU Packet and Circuit Switch Planes

Eclipse Liquid Bandwidth for Seamless Scalability Liquid BandwidthTM is the Eclipse ability to seamlessly assign link capacity to Ethernet, and to companion PDH traffic for native mixed mode operation.

It uses the Nx2 Mbit/s circuit switch plane to assign capacity in 2 Mbit/s / E1 steps to optimize throughput granularity for network planning purposes. This is illustrated in Figure 6, which indicates possible assignments to native Ethernet and to companion NxE1 capacity for a selected link capacity.

Liquid Bandwidth means that the traffic over an Eclipse link can be user-assigned between PDH and Ethernet – from PDH-only to PDH+Ethernet, and ultimately to all-Ethernet. Link capacity, channel bandwidth, and modulation can also be selected from option menus, which for many requirements will require nothing more than a configuration change using the Portal craft tool. Figure 6. Eclipse Liquid Bandwidth

Liquid bandwidth

supports easy

migration from

PDH to native

Ethernet.



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Eclipse Wireless Packet Node The new Eclipse extended packet plane capability is unique - it delivers industry-leading flexibility and performance. One Eclipse node now supports up to six separate links, with each supporting native GigE to 360 Mbit/s. Or up to five GigE links and one Liquid Bandwidth link for Ethernet and PDH.

• The extended packet plane supports multiple GigE user interfaces with inter-card Ethernet bridging and aggregation.

• The circuit plane supports the Liquid Bandwidth Ethernet and PDH connections.

• One Eclipse Node is simply populated with the mix of cards needed at any time to provide the required throughput, protection, and aggregation of traffic.

This capability is backward compatible with installed INUs to provide exceptional value-add on Eclipse networks. It means the native capacity capabilities on existing INUs is increased five-fold. Furthermore, the effectiveness of this gain can be magnified by the statistical multiplexing provided by traffic aggregation and data optimization options.

Figures 7, 8, 9 illustrate some of the configurations made possible. The combined packet and circuit planes represent a breakthrough in wireless backhaul connectivity. Figure 7. Ethernet and PDH Aggregation Node

Figure 8. Ring/Mesh Node

Figure 9. Ring and Spur Node

The packet switch

plane supports up

to six 1+0 links,

each with a

maximum air-

capacity of 360

Mbit/s.

One Eclipse INU

or INUe supports

multiple links,

and the advanced

L2 switch and

TDM cross-

connects support

complex ring and

aggregation

network

topologies.



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Link Capacity and Spectral Efficiency Eclipse link capacity options are achieved within standard ETSI channel bandwidths ranging from 3.5 to 56 MHz. High-order modulation is used to achieve maximum efficiency per channel. Examples include:

• An industry-leading 190 Mbit/s or 93xE1 in a 28 MHz channel using the Liquid Bandwidth capability. Similarly, 204 Mbit/s or 100xE1 is supported on 40 MHz or 56 MHz channels using 128 QAM and 32 QAM respectively.

• 360 Mbit/s in a 56 MHz channel.

• 1xSTM1 in a 28 MHz channel, or 2xSTM1 in a 56 MHz channel.

Note that 1xSTM1 only supports a maximum 63xE1 - STM1 is less spectrally efficient when transporting E1 streams.

Where more capacity is needed than can be provided over one link, Eclipse options include co-channel dual polarization (CCDP) to support 720 Mbit/s, 200xE1 or 4xSTM1. For even higher capacities there are Eclipse 4+4 quattro solutions.

Intelligent, Carrier Grade Ethernet For an Ethernet device to be considered carrier grade, it must have intelligence beyond the simple rule-based packet forwarding capabilities supported by basic L2 switches. As determined by the Metro Ethernet Forum (MEF), there must be the ability to meet carrier-grade requirements for standardized services, reliability, scalability, QoS and service management.

Eclipse Carrier Ethernet over Wireless has this capability.

• Eclipse GigE radios are certified compliant with the MEF 9 and MEF 14 Carrier Ethernet standards. MEF 9 specifies the UNI (Universal Network Interface); MEF 14 specifies the QoS (Quality of Service) parameters.

• This certification provides an assurance that Eclipse GigE links will interoperate with other carrier Ethernet devices, now and into the future.

• Harris Stratex Networks is a founding member of the MEF Mobile Backhaul Group, whose aim is to promote and define the use of Carrier Ethernet services for mobile/cellular networks

Carrier-grade Performance The technology required to deliver MEF 9 and MEF 14 compliance requires an intelligent Ethernet switch. Eclipse is compliant, using features that include advanced QoS options, outstanding reliability and scalability, and best-quality Operation, Administration and Maintenance (OAM) in conjunction with the Harris Stratex ProvisionTM EMS.

Advanced QoS and Performance Options

MEF specifies that support must be provided for Service Level Agreements (SLAs) to deliver end-to-end performance matching over converged networks. Such networks may require support for traffic routing, prioritization, aggregation and protection. Additionally, networks must be able to detect and recover from incidents without impacting users.

Eclipse satisfies these requirements with features normally only found in advanced stand-alone switches. These include port and VLAN prioritization, VLAN Q and Q-in-Q tagging, fast-switched RSTP (RWPR) operation, and link aggregation:

Carrier Ethernet,

as defined by the

MEF, is the

technology for

next generation

backhaul

networks.



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• Port Prioritization. Prioritizes traffic on one port over another.

• VLAN (Tag) Prioritization. Ethernet traffic is prioritized on a frame-by-frame basis using the CoS (Class of Service) bits in the VLAN field of an Ethernet header, or the DSCP bits in the Differentiated Services (DiffServ) field of an IP header.

• Q and Q-in-Q Tagging using the CoS/802.1p prioritization bits. In the Q-in-Q (backbone provider bridge) mode Eclipse can aggregate up to 4 separate customer VLANs onto a common radio channel. Tagging can be retained into an external network for downstream traffic management.

• RWPRTM (Resilient Wireless Packet Ring). RWPR enhances industry-standard RSTP (802.1D-2004) with a unique rapid failure detection (RFD) capability to provide carrier-class network reconvergence times on Eclipse GigE ring and mesh networks. Depending on the network topology, reconvergence (service restoration) times are as low as 50 ms.

• Flow Control. Provides a mechanism to throttle back data from sending devices to reduce demands on available Ethernet bandwidth.

• Link Aggregation. Two or more links are combined into a single logical link, with a traffic capacity that is the sum of the individual links. It is especially relevant to wireless links when traffic capacities higher than the 300 to 360 Mbit/s maximums for a single link are required. Two physical links are used for 720 Mbit/s, four for 1.4 Gbit/s.

Link aggregation also provides sub 50 ms redundancy. If one link fails, its traffic is redirected onto the remaining link, or links. If the remaining link(s) do not have the capacity needed to avoid a traffic bottleneck, QoS priority settings are used to ensure all higher priority traffic continues to get through. Uniquely, Eclipse offers Layer 2 and Layer 1 link aggregation options.

- Layer 2 link aggregation (802.3ad) uses source and/or destination MAC address data in the Ethernet frame MAC/LLC header.

- Layer 1 aggregation acts on the byte data stream. Unlike L2 link aggregation it provides optimum payload sharing regardless of the throughput demands of individual user connections, making it ideal for router-router applications.

Advanced OAM for End-to-End Management

OAM standards (ITU Y-1731, IEEE 802.1ag, MEF) call for network-wide fault detection/recovery, performance monitoring, diagnostics, and maintenance. This means every device in the network must be visible to a network operator to provide the tools needed to determine device and network status and performance, and to effect changes when needed.

Eclipse and its ProVision EMS provide these capabilities end-to-end for the radio and L2 switch functions:

• Where external switches are used in a wireless Ethernet network there is usually no management synergy between the switch and the radios; each is supported on its own management system.

• With Eclipse, management of the radio and Ethernet functions is fully integrated to deliver maximum visibility to operators. For example, where Ethernet performance is being affected by radio performance, the problem is easily diagnosed using common user-friendly interfaces.

Ethernet diagnostics include RMON performance data, Ethernet history, and Ethernet data-dashboards for throughput, errors and discards. ProVision additionally supports end-to-end network mapping, circuit provisioning, and performance monitoring at service (VLAN) and link

Harris Stratex

ProVision EMS

provides network-

wide E-Line and

E-LAN OAM

services.



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levels. Relevant Ethernet and radio error events are supported by probable-cause and remedial advice. Figure 10. Example ProVision EMS Screens for Network Health and Bandwidth Utilization

Adaptive Modulation In many instances spectrum availability is limited, so changing to a wider channel bandwidth to achieve a higher link capacity is not an option. Changing to a more efficient modulation scheme will provide more link capacity, but it will be at the expense of a lowered system gain, and hence link availability. This is where adaptive modulation provides a solution.

Instead of using a fixed modulation rate to provide a guaranteed capacity and service availability under all path conditions, the modulation rate, and hence capacity, is increased when path conditions permit. On a typical link this means higher capacity will be available for better than 99.5 percent of the time.

• Adaptive modulation refers to the dynamic adjustment of modulation rate to ensure maximum data bandwidth is provided most of the time, with a guaranteed bandwidth provided all of the time.

• Wireless links are traditionally engineered to carry traffic with a 99.999% availability under all path conditions. A link using robust QPSK modulation can have as much as 30 dB of fade margin, but is only needed to protect the link against worst-case fades that may occur for just a few minutes in a year. For the rest of the year the margin is not used.

• By using less robust but more efficient modulation schemes, the available fade margin can be transformed into delivering more data throughput. This is the purpose of adaptive modulation; it dynamically changes the modulation so that the highest availability of capacity is provided at any given time.

• When used in conjunction with QoS traffic prioritization, it can be configured to ensure all high priority traffic continues to get through when path conditions deteriorate; only low priority ‘best effort’ data is discarded.

Figure 11 illustrates the modulation/capacity steps and the percent availability over time. QPSK, as the most robust modulation, is used to support critical traffic with a 99.999% availability. Less critical traffic is assigned to the higher modulations. Most importantly, the highest modulation is typically available for better than 99.5% of the time.

Highest capacity,

256 QAM

throughput is

typically available

for 99.5% of the

time.



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Figure 11. Adaptive Modulation Illustration

With Eclipse, adaptive modulation simply requires installation of a plug-in card. It interacts with other plug-ins to provide an end-to-end solution for Ethernet only, TDM only, or a combination of Ethernet and TDM payloads.

It uses one of five automatically and dynamically switched modulations - QPSK, 16 QAM, 64 QAM, 128 QAM, or 256 QAM - selected by an adaptive modulation engine that can handle up to 100 dB/s fading fluctuations. For a given RF channel bandwidth of 7, 14 or 28 MHz, a two-fold improvement in data throughput is provided for a change from QPSK to 16 QAM, a three-fold improvement to 64 QAM, and a four-fold improvement to 256 QAM. An adaptive coding capability will provide options to trade off throughput against system gain.

Note that in many instances the link parameters that supported the original system gain can be retained. For example, the antenna sizes and Tx power used for an original QPSK link on a 7 MHz channel (10 Mbit/s / 5xE1) are unchanged when operated on 256 QAM using adaptive modulation. The adaptive modulation engine ensures that the highest throughput is always provided based on link quality. This typically means that on the original 10 Mbit/s link, 45 Mbit/s throughput is provided for 99.5% of the time.

Modulation switching is hitless. During a change to a lower modulation, remaining higher priority traffic is not affected. Similarly, existing traffic is unaffected during a change to a higher modulation.

Note that while adaptive modulation can also be used on PDH links and combined PDH and Ethernet links, unlike Ethernet there is no QoS synergy on PDH connections.

• Ethernet connections enjoy real synergy through the QoS awareness on the GigE plug-in, and the service provisioning provided by any MPLS or PBB-TE network overlay. All high priority traffic, such as voice and video, continues to get through when path conditions are poor. Outside these conditions ‘best effort’ lower priority traffic, such as email and file transfers, enjoy data bandwidths that can be up to four times the guaranteed bandwidth.

• E1 connections are dropped in user-specified order when link capacity is reduced, and restored when capacity is restored.

Co-Channel Dual Polarized Links (CCDP) In situations where increasing the channel bandwidth and/or increasing the modulation rate, will not provide the capacity needed, CCDP provides an answer. It doubles wireless capacity over the same channel. When coupled with adaptive modulation, this can be increased by a factor of 4:1 to provide an overall improvement of 8:1.

This has special significance on capacity extensions needed to support HSPA 3G and 4G base stations where figures in excess of 50 Mbit/s are forecasted for mid-city sites. For

Investments in

existing channel

plans can be

maximized using

Eclipse CCDP

and adaptive

modulation.

Modulation

switching is

hitless for traffic

that is not

discarded.



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example, a 7 MHz RF channel supports just 10 Mbit/s using QPSK, expands to 45 Mbit/s using 256 QAM adaptive modulation, then doubles to 90 Mbit/s using CCDP.

The CCDP option provides two parallel communication links on the same RF channel. One link uses the vertical polarization, the other the horizontal. A single twin-feed dual polarized antenna is installed at each end of the link, and Cross Polarized Interference Cancellation (XPIC) is used in the radios to ensure any interference between the channels is eliminated. Figure 12. 720 Mbit/s Link Aggregated Mixed Mode CCDP Terminal

Figure 13. 720 Mbit/s Link Aggregated RSTP CCDP Ring Node

Adding CCDP operation to an existing Eclipse link simply requires installation of the parallel link, replacement of the existing antenna with a dual-pol antenna, and the fitting of plug-in XPIC radio access cards.

• Eclipse CCDP configurations cover channel bandwidths from 7 to 56 MHz.

• Modulation options extend from QPSK to 256 QAM, fixed or adaptive.

• Capacity maximums (both links) extend to 720 Mbit/s, 200xE1, or 4xSTM1.

• If both links are configured for Ethernet, the two traffic streams can be L1or L2 link-aggregated onto a single user interface.

• The capacity on each link can be used for Ethernet, TDM, or a mix of TDM and Ethernet (Liquid Bandwidth).

• CCDP links can be 1+1 protected (hot-standby or diversity), or operated in a Super-PDH ring.



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Where even higher capacity links are needed, three or four links can be installed. For example, two CCDP link pairs (four links in total) can support up to 1.4 Gbit/s.

Pseudowires Psuedowires are used to transport a native service over a packet switched network. For mobile backhaul networks, pseudowires will be needed where a PDH network is replaced by an Ethernet or IP/MPLS based network, but must retain support for legacy PDH interfaces at 2G and 3G base stations.

The HSX pseudowire solutions comply with industry-standard IETF and MEF 8 PWE3 options for:

• TDM over IP/MPLS (CESoPSN – structured E1)

• TDM over IP/MPLS (SAToP – unstructured E1)

• TDM over Ethernet (CESoETH – MEF 8)

• ATM pseudo wires (legacy R99 traffic)

• HDLC and PPP pseudo wires (CDMA market)

An industry-standard solution is essential to ensure network-wide connectivity and interoperability.

Network Synchronization Within a PDH backhaul network, E1s are used as the BTS clocking source to provide base station synchronization. If replaced by an all-Ethernet backhaul network, an alternative clocking source is required. While it is apparent that operators will choose implementations based on their particular legacy infrastructure and future plans, for converged services the options most preferred are IEEE 1588v2 Precision Time Protocol (PTP), and synchronous Ethernet.

Some operators have indicated intent to use IEEE 1588v2 or synchronous Ethernet. Others have indicated that they will likely incorporate both, with synchronous in the core, and IEEE 1588 in the Metro and access portions of the network. Harris Stratex solutions will support both options.

• Eclipse currently supports transparent transmission of IEEE 1588v2 frames - Eclipse can be direct-connected to Ethernet-ready Rev.5 Node Bs that incorporate an IEEE 1588v2 slave.

• For pseudowire-connected legacy base stations an external IEEE 1588v2 slave/translator is used to generate the clocking source.

• A synchronous GigE option will be provided when the standard (G.8262) is fully promulgated.

IP/MPLS and PBB-TE The traffic engineering capabilities of IP/MPLS are well established. It is the prominent core network protocol for converged networks, and as these networks evolve it is being pushed further towards the network edges. It provides predicable and robust routing and QoS differentiators for multiple service levels and customer groups, so is well positioned to support the evolution of mobile networks from mixed mode to all IP transport, including the adoption of pseudo wires.

To ensure end-to-

end compatibility

on converged

networks,

synchronization

options must be

standards-

compliant.



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PBB-TE, unlike MPLS, is optimized for Metro Ethernet networks, and consequently offers less complex and lower cost traffic engineering solutions compared to MPLS.

Standards-compliant MPLS and PBB-TE solutions are available from Harris Stratex to ensure interoperability with those from leading core network vendors.

Bandwidth Optimization and Traffic Aggregation Optimization and aggregation and can provide dramatic capacity efficiencies on backhaul connections where, for example, 2G and 3G circuit-switched connections are converted to packet-based data and aggregated (multiplexed) using the aggregation capabilities of a layer 2 Ethernet switch.

• While optimization and aggregation can apply on existing TDM network connections, they enable particularly cost effective gains on Ethernet or IP/MPLS networks where a common transmission pipe is shared for aggregated services.

• Optimization and IP/Ethernet conversion is available for Abis and lub (3G R99), which when aggregated with HSPA data can provide 4:1 bandwidth efficiency gains.

Traffic aggregation is supported on the Eclipse Ethernet interfaces. The resultant dynamic bandwidth allocation between the different aggregated services means maximum use is made of available capacity on the trunk; when there are no voice calls, the full trunk bandwidth is available for data traffic. As the number of voice calls increases, the bandwidth for data is dynamically backed off, with service priority issues handled by the QoS engine.

Conclusion Data services will grow quickly to use more network capacity than voice. More network capacity translates to more backhaul capacity. Coupled with this is the recognition that Ethernet is the transport media of choice for expanded backhaul services.

For many operators the introduction of Ethernet will be on the back of existing TDM network connections given their huge investment in its infrastructure. This will typically involve gradual migration using data overlay, with a decision at some future point to change to an all packet-based network. Other operators may elect to forgo migration and completely replace existing TDM networks using Ethernet. Pseudowires will be used to support legacy TDM connections.

Whatever the direction, Eclipse provides optimized wireless backhaul solutions through its unique packet and circuit switched architecture.

• The extended packet plane supports multiple GigE connections to 1.4 Gbit/s. Link capacities can be configured to 360 Mbit/s, 720 Mbit/s CCDP, or 1.4 Gbit/s CCDP/Quattro.

• The Liquid Bandwidth circuit plane supports native mixed mode operation with Super PDH capacities to 100xE1 and Ethernet to 200 Mbit/s. Services are split between TDM and Ethernet in 1xE1 / 2 Mbit/s steps to the maximums, to accommodate a low-risk PDH now, and Ethernet tomorrow transport philosophy.

Assisting the upgrade route are Eclipse options for better spectrum efficiency. More capacity can be transported on existing channels using high-order modulation, adaptive modulation or co-channel operation.

Similarly, carrier grade Ethernet performance is made possible via an intelligent layer 2 switch to ensure that the transport of Ethernet data is no less secure than for TDM. When coupled with advanced traffic prioritization, RWPR, link aggregation, pseudowires, network synchronization, MPLS, bandwidth optimization and traffic aggregation, there is a Harris Stratex solution for all network topologies.

Eclipse solutions

are optimized for

now and next

generation mobile

backhaul

networks.

The value-add

node concept

provides

maximum

performance with

lowest cost and

risk.



White Paper

The backbone for this capability is the Eclipse INU where plug-in modules provide uniquely flexible and scalable platforms for lowest incremental cost and maximum value-add. Where the plug-in flexibility of the INUs is not required, such as at edge sites, Eclipse IDUs provide cost and performance optimized solutions for Ethernet with or without PDH. In most situations Eclipse eliminates the need for expensive external network devices.

Finally, Eclipse comes with an assurance from Harris Stratex that value-adds will continue to become available to existing and new Eclipse customers to deliver more features and more performance. It is a promise of a low-risk and future-proof investment in Eclipse.



White Paper

Glossary CCDP Co-channel dual polarized. CE Customer edge. Interface to the customer network in an MPLS network. EDGE Enhanced data rates for GSM evolution. An enhanced modulation technique designed to provide data

rates up to 384 Kbps. eLSR Edge label switch router. Provides the edge function of MPLS label switching and functions as an MPLS

Provider Edge (PE) node in an MPLS network. E-Line Denotes an Ethernet point-to-point service. Applicable to private lines, virtual private lines, and Ethernet

Internet Access. E-LAN Denotes an Ethernet multipoint service. Applicable to multipoint L2 VPNs, and transparent LAN

services. EMS Element management system. EVC Ethernet virtual connection. Denotes a multipoint or point-to-point Ethernet connection over a host

network, such as SDH. HSPA High speed packet access. HSDPA High speed downlink packet access. HSUPA High speed uplink packet access. LSR Label switch router. Provides the core function of MPLS label switching and functions as an MPLS

Provider (P) node in an MPLS network. LTE Long term evolution. Evolving standard for 4G mobile networks. MEF Metro Ethernet Forum. NGN Next generation network. PDH Plesiosynchronous digital hierarchy. Asynchronous multiplexing scheme in which multiple digital

synchronous circuits run at slightly different clock rates. Phy Physical, layer 1 level/interface. QoS Quality of service. P node Provider node in an MPLS network. Function is enabled on an LSR. PE node Provider edge node in an MPLS network. Function is enabled on an eLSR. RSTP Rapid spanning tree protocol. RWPRTM Resilient Wireless Packet Ring. SDH Synchronous digital hierarchy. Transmission rates range from 51.84 Mbit/s (STM0) and 155.52 Mbit/s

(STM1) through to 10+ Gbit/s. SFP Small-form-factor pluggable. SLA Service level agreement. TDM Time division multiplexing. Multiple low-speed signals are multiplexed to/from a high-speed channel, with

each signal assigned a fixed time slot in a fixed rotation. UNI Universal network interface. The physical port between the customer and service provider. It is always

provided by the service provider, and in a carrier Ethernet Network is a physical 10, 100, or 1000 Mbit/s, or 10 Gbit/s Ethernet interface.

VLAN Virtual LAN. IEEE 802.1Q tagging mechanism. VPLS Virtual private LAN service. VPN Virtual private network. WiFi Wireless Fidelity. WiFi is a trademark of The Wi-Fi Alliance (www.wi-fi.org). WiMAX Worldwide Interoperability for Microwave Access. Interoperability brand behind the IEEE 802.16

Metropolitan Area Network standards. XPIC Cross-polarized interference cancellation.

Documents

Next Generation Mobile Backhaul Solutions by STRATEX