microwave backhaul enables mobile network...

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Microwave Backhaul Enables Mobile Network Evolution ANSI

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® Packet Node wireless platforms from Harris Stratex Networks.

Executive Summary 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 Packet Node provides optimized wireless backhaul solutions through its unique packet and circuit switched architecture.

• The data packet plane (DPP) supports multiple GigE connections to 2+ Gbit/s. Link capacities can be configured to 380 Mbit/s, 760 Mbit/s CCDP, or 1.5 Gbit/s CCDP/Quattro.

• The circuit plane (backplane) inter-operates with the DPP to support native mixed mode Ethernet + TDM, with PDH capacities to 127xDS1. Mixed-mode operation accommodates a low-risk PDH now, and Ethernet tomorrow transport philosophy. Eclipse Packet

Node makes it

easy to upgrade to

packet radio.

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

Similarly, carrier grade Ethernet performance is provided on an intelligent layer 2 switch to ensure Ethernet data transport 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 Packet Node solution for all network topologies.

The backbone for this capability is the Eclipse INU where plug-in cards upgrade existing Eclipse Node capabilities to Eclipse Packet Node. There is maximum retention of existing Eclipse hardware and software, which equates to maximum value-add and minimum disruption to existing services.

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 low-risk, low incremental cost, and a future-proof investment in Eclipse.

June 2009 Eclipse Packet Node In Mobile Networks: ANSI of 21

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Introduction Typically a small number of DS1s 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.

Data is

precipitating

massive changes

in mobile

backhaul. 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 to the base stations. It is also the ideal technology for use in MPLS 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 Packet Node now supports up to six links, and a programmable total nodal throughput of over 2 Gbit/s Ethernet and up to 127xDS1 or 2xOC3.

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 RAN has a

major role in

decoupling

network costs

from traffic

growth.

Figure 1. The Uncoupling of Voice and Data Revenues


Copyright © 2009 Harris Stratex Networks, all rights reserved.

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This need for more capacity brings pressure on the backhaul network, where instead of current 2xDS1 / 3 Mbit/s connections per 2G BTS, the 3G data revolution is expected to require from 10xDS1 or 15 Mbit/s within 2 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 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 IP network applications on in-house or third-party networks.

Carrier Ethernet

provides the

enabling

technology. • 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.

• Aggregation: Through statistical multiplexing of two or more traffic streams, variations in the aggregate traffic are smoothed to consume a lower peak bandwidth. It means more data can be delivered over the same link capacity compared to circuit-dedicated TDM.

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.

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 IP/MPLS and PBB-TE are particularly relevant to efficient and robust transportation in a converged services network.



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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.

More capacity

must be provided

more intelligently. 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 networks 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. Figure 3. Pseudowires



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Synchronization An IP/MPLS or all-Ethernet network must ultimately be able to transport the stringent frequency and phase synchronization requirements of 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. Packet-based IEEE 1588v2 meets requirements for precision frequency and phase synchronization, but does have some traffic loading issues. Synchronous Ethernet does not support phase synchronization, but does provide frequency synchronization independent of traffic loading. Ultimately the two may co-exist as merged solutions.

MPLS and PBB-TE The merging of

customers,

technologies, and

services onto one

converged

network offers

real economies of

scale.

MPLS and PBB-TE are “traffic engineering” technologies for converged networks. They are designed to speed up network traffic flow, and 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 appears to support MPLS, though PBB-TE has its advocates for non-core Metro and access networks. In the end operator preferences will decide the direction.

MPLS

MPLS is a mature ITU / IETF standard. It is the prominent core network protocol for converged networks, and as these networks evolve it is being pushed further out from the core. It provides predicable and robust routing and QoS differentiators for multiple service levels and customer groups.

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.

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.



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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 suppression 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 from each voice channel, and A.bis data is extracted and converted to a packet format to deliver overall bandwidth savings of up to 50%.

Data optimization

and traffic

aggregation bring

major

improvements in

bandwidth

utilization.

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 and Statistical Multiplexing Statistical multiplexing on aggregated traffic streams can bring improvements in bandwidth utilization of more than 30%.

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) is also developing relevant standards and recommendations.



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Packet Node Solutions Eclipse Packet Node provides more network capacity, more intelligently, at lowest possible incremental cost. It logically and seamlessly addresses transitioning from TDM, to Ethernet + TDM, and ultimately to a fully converged Ethernet network.

Packet Node incorporates a new data packet plane with a 2+ Gbit/s payload capacity, adaptive coding and modulation, extended link aggregation, wider OAM capabilities, optimized pseudowire options, and solutions for timing over Ethernet. It retains its host Eclipse Node features, such as carrier-class RSTP, and extensive options for PDH and SDH inter-working.

Packet Node is

optimized for IP

and TDM

networks. With its current and road-mapped features, Packet Node provides all the components needed to support existing and planned network growth towards HSPA, WiMAX, or LTE.

These next sections introduce Packet Node, and its evolution from Eclipse Node.

Eclipse Packet Node Packet Node introduces a data packet plane (DPP) that supports more than 2 Gbit/s of aggregated IP traffic. It uses the same platform as Eclipse Node and operates seamlessly with the existing backplane (circuit plane).

Operation is enabled on plug-in cards, meaning existing investments in Eclipse Node are retained. Packet Node cards along with other Eclipse cards, can be relocated / reused within networks as and when needed.

• The DPP routes Ethernet traffic directly between its GigE switch and packet radio modem(s) to deliver maximum payload efficiency with lowest latency.

• But the DPP also connects to the backplane to support hybrid mixed-mode operation and to access wider aggregation, pseudowire and synchronization options.

• In combination they optimize transport options for Ethernet, and for Ethernet + TDM.

Packet Node features include:

• Major increases in nodal throughput.

• Advanced GigE switch with 1+1 redundancy options.

• High-capacity links with QPSK to 256 QAM ACM and XPIC/CCDP options.

• Advanced L1 and L2 link aggregation.

• Industry-standard pseudowire options.

• Timing over Ethernet solutions.

• Easy upgrades with low incremental cost.

• Maximized flexibility and scalability.

• Comprehensive OAM capabilities in conjunction with its ProVision EMS.

Some Eclipse Packet Node features and capabilities may be subject to availability. Please contact your Harris Stratex Networks representative for details.



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Figure 5. Packet Node High-level Architecture

Ethernet is

transported via

the DPP.

Ethernet and

TDM via the

Backplane.

Platform

INU

Packet Node comprises the INU or INUe, with split-mount ODUs or an all-indoor RFU, the IRU 600.

The INU directly supports up to three links, the INUe up to six.

INUe

The need for

expensive external

network devices is

minimized.

• Operation on licensed bands 5 to 38 GHz.

• Each link can be configured for an air-capacity to 380 Mbit/s.

• With data optimization techniques, each supports L1 throughputs to 540 Mbit/s.

• An INU or INUe is simply populated with the mix of cards needed at any time to provide the required performance and operation

ODU 300hp & Antenna

• Equipment, cabling and rack space is dramatically reduced.

• Cards are hot-pluggable for easy up-grading and maintenance.

IRU 600



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Extended ODU and RFU Options There is a choice of three split-mount ODUs or an all-indoor RFU.

• ODU 300hp for frequency bands 6 to 38 GHz.

• ODU 300ep for 5 GHz.

• TR 5100 or TR 5200 ODUs for bands 6 to 38 GHz.

o These are the TRuepoint 5000 ODUs.

o Packet Node inter-operation with these ODUs provides an easy, low-cost upgrade path for existing TRuepoint 5000 installations.

o By swapping only the TR 5000 IDU for the Packet Node INU or INUe, existing investments in the TR 5000 are maximized, upgrade costs are minimized, and with no tower work required, service disruption is kept to a minimum.

o Packet Node features such as extended ACM operation for Ethernet, or Ethernet and PDH are retained over both the TR5100 and TR 5200.

• IRU 600 all-indoor RFU for frequency bands 6 to 11GHz.

o Industry-leading system gain coupled with lowest power consumption.

o 1+1 optimized.

o Diplexer and filter based antenna coupler options.

o Expansion port option.

o Expandable to M+N configurations.

o Air compatible with ODU 300hp.

These ODU and RFU options have been fine-tuned for the wider US market. There is an optimized solution for all platform preferences, and in the case of the TR 5000 ODUs, a real incentive is provided to upgrade TR 5000 networks to full Packet Node performance.

Payload Packet Node is optimized for easy and cost-efficient migration solutions from TDM to Ethernet.

• Ethernet is overlaid on existing TDM links. Voice connections are transported on TDM, with the burgeoning data traffic on the overlay.

• The most cost-efficient solution is for TDM and Ethernet side-by-side on hybrid mixed-mode links, with the ability at any time to change the ratio of Ethernet to TDM.

• Moreover, the migration from TDM-only to TDM + Ethernet, and ultimately to all-Ethernet, is straight-forward, flexible and very cost-effective. There is no loss of transport efficiency when a mixed-mode link is migrated to an all-Ethernet payload.

Mixed-Mode The backplane, or the backplane plus DPP are used.

• Packet Node backplane connections support Ethernet + Super PDH, with capacities to 200 Mbit/s or 127xDS1 in 1.5 Mbit/s / DS1 steps.

• DPP connections support 2+ Gbit/s.



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• DPP and/or Backplane traffic is connected to one or more radio access cards (RACs), which in turn connect to an ODU or IRU 600. Hybrid mixed-

mode Ethernet +

TDM solutions

are easily

configured, and

re-configured

when needed.

Adding Ethernet to a Super-PDH link simply requires installation of a GigE or FastE card, at which point an operator can locally or remotely configure the capacity split between PDH and Ethernet in DS1 or 1.5 Mbit/s steps using the Liquid Bandwidth feature on the backplane. It means Ethernet can be activated when and where needed in the network with minimum disruption.

When more data capacity is needed, the DPP capability is introduced using plug-in cards. Adaptive coding and modulation, link aggregation and XPIC/CCDP options enable an Ethernet capacity of more than 2 Gbit/s, with or without legacy Super PDH circuits.

• Super PDH® refers to the ability to transport up to 127xDS1 over a wireless link.

• This is a major performance improvement over the 84xDS1 maximum on an OC3 link, or the typical 16xDS1 maximums of legacy PDH links. But if OC3 is needed in the backhaul, Eclipse also has link options for 1xOC3 and 2xOC3.

Figure 6 illustrates some of the mixed-mode configurations made possible. The combination of DPP and backplane represents a breakthrough for wireless-based connectivity. Capacities indicated are airlink capacities. Ring protection is provided for NxDS1 and Ethernet. The advanced

packet and circuit

elements support

complex ring and

aggregation

networks.

Figure 6. Example Mixed-mode Nodes

All-Ethernet Packet Node extends solutions for all-Ethernet payloads.

• The Backplane supports aggregate capacities to 200 Mbit/s with an Nx1.5 Mbit/s granularity, or to 300 Mbit/s with Nx150 Mbit/s.

• The DPP goes much further, with support for aggregate capacities to 2+ Gbit/s. Airlink capacities (up to six) extend to 380 Mbit/s per link.

• Ethernet frame optimization extends L2 throughputs to 410 Mbit/s and L1 to 540 Mbit/s per link.

Optimized all-Ethernet Packet Node links can be installed from new, or enabled on existing TDM, or TDM + Ethernet installations simply by adding / replacing hot-swappable plug-in cards.





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Carrier Grade Ethernet For an Ethernet device to be considered carrier grade, it must meet the Metro Ethernet Forum (MEF) requirements for standardized services, reliability, scalability, QoS and service management. Harris Stratex is a

founding member

of the MEF

Mobile Backhaul

Group.

Packet Node supports these requirements through MEF 9 and MEF 14 compliance.

• MEF 9 specifies the UNI (Universal Network Interface)

• MEF 14 specifies the QoS (Quality of Service) parameters.

Certification provides an assurance that Packet Node will interoperate with other carrier Ethernet devices, now and into the future.

Harris Stratex Networks is also 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 Traffic Shaping Support is provided to ensure end-to-end service-level matching on converged networks through traffic shaping and prioritization. This particularly applies where available Ethernet bandwidth is, or can be over-subscribed. Packet Node features include:

• Priority Mapping options on ports, and on 802.1p and DiffServ tags, to shape packet access to the available link bandwidth. 8 QoS queues per port provide maximum flexibility when transporting a wide range of traffic types with related priorities.

• Priority Scheduling with extended options for WFQ, strict, and hybrid WFQ + strict.

• Traffic Classification. VLAN Q and Q-in-Q tagging using the CoS/802.1p prioritization bits. In Q-in-Q mode, Packet Node aggregates multiple customer VLANs onto a common radio channel. Tagging can be retained into an external network for downstream traffic management.

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

Carrier Grade Network Resilience Eclipse Node and Packet Node networks detect and recover from incidents without impacting priority users. Protection options support the interfaces, links, network, and the platform.

Ethernet Interface Protection. GigEv3 switch cards are fully hardware protected using a stackable architecture – cards are paired, with the customer interfaces supported on separate cables from each card. Optical Y-cables are used where a single connection is needed. The stacked cards also provide a port expansion capability for situations where more physical user ports are needed.

Ethernet Network Protection. Redundancy is provided on ring and mesh networks, and on link-aggregated connections.

• RWPRTM (Resilient Wireless Packet Ring) for ring and mesh networks. RWPR accelerates industry-standard RSTP (802.1D-2004) with a unique rapid failure detection (RFD) capability to provide reconvergence (service restoration) times as low as 50 ms.

• Link aggregation. Sometimes referred to as N+0 protection. If one link fails, its traffic is directed onto the remaining link(s), typically within 10 ms. If the remaining link(s) do not have the capacity needed to avoid a traffic bottleneck, QoS settings are used to ensure

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higher priority traffic continues to get through. Uniquely, Eclipse offers Layer 2 and Layer 1 link aggregation options.

Radio Link Protection. Links are protectable through hot-standby, space diversity, frequency diversity, or dual protection options. Protection is hitless for an Rx path failure.

Platform Protection. Essential Node management functions are protected using optional protection cards.

Carrier Grade OAM The ProVision EMS for Eclipse supports relevant requirements within ITU Y-1731 for the service layer, and within IEEE 802.3ah for the link layer. Every Eclipse device in a network is visible to network operators together with the tools needed to determine device and network status and performance, and to effect changes when needed. Features include:

• Fully integrated management of the radio and its Ethernet traffic. For example, where Ethernet performance is being affected by radio performance, the problem is easily diagnosed using common user-friendly interfaces.

Harris Stratex

ProVision EMS

provides network-

wide E-Line and

E-LAN OAM

services.

• Ethernet diagnostics with RMON performance data, Ethernet history, and Ethernet data-dashboards for throughput, errors and discards. Troubleshooting is supported by port mirroring, IGMP snooping, and loopback testing.

• End-to-end network mapping, circuit provisioning, and performance monitoring at service (VLAN) and link levels. Strong security is to be supported on SNMPv3 and RADIUS.

• A Multi-Technology Operations System Interface (MTOSI : TMF 854) is being implemented to support ProVision interfacing between MTOSI-standardized management systems.

• Error events supported by probable-cause and remedial advice.

• Site energy and security management with system status, fault management, fuel usage reporting, and energy control history.

Figure 7. Example ProVision EMS Screens for Network Health and Bandwidth Utilization



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Capacity and Spectral Efficiency Superior capacity and spectrum efficiency gains are a feature of Packet Node:

• Adaptive coding and modulation (ACM) for most efficient use of channel bandwidth.

• Co-channel Dual Polarized (CCDP) link operation.

• Ethernet data optimization.

• L1 or L2 link aggregation.

Adaptive Coding and Modulation 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 to provide a higher capacity. Typically this higher capacity will be available for better than 99.5% of the time.

• Adaptive modulation is 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.

• A link using robust QPSK modulation can have as much as 30 dB of fade margin to support a 99.999% availability. But this 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 is transformed into delivering more data throughput - adaptive modulation 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 8 illustrates Packet Node modulation/capacity steps and typical percent availability over time. QPSK, as the most robust modulation, is used to support critical traffic. 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. Figure 8. Adaptive Modulation At Work

The highest

capacity is

typically available

for 99.5% over

time.

Packet Node adaptive modulation is enabled on a plug-in card. It interacts with other cards to provide an end-to-end solution for Ethernet only, TDM only, or a combination of Ethernet and TDM.

It uses one of four automatically and dynamically switched modulations - QPSK, 16 QAM, 64 QAM, or 256 QAM. For a given RF channel bandwidth a two-fold improvement in data



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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.

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 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.

Modulation

switching is

hitless for traffic

that is not

discarded.

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 card, 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.

• DS1 connections are dropped in user-specified order when link capacity is reduced, and restored when capacity is increased.

Figure 9. Packet Node Adaptive Modulation Steps : Maximum Throughput

Black Mbit/s: Native link (air) capacity

Red Mbit/s: Maximum L1 throughput (port utilization) for a 64 byte frame with frame optimization (IFG and Preamble suppression and MAC header compression)



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Coding for Maximum Throughput or Maximum Gain

Modulation code settings provide two sets of modulation rates; one for maximum-throughput, one for maximum-gain.

• Maximum throughput delivers maximum data throughput – at the expense of some system gain. Figure 9 shows throughputs with ACM coding set for maximum throughput.

• Maximum gain delivers best system gain – at the expense of some throughput.

• Maximum throughput or maximum gain rates can be selected across all ACM states, or they can be inter-mixed so that one or more of the four possible QPSK to 256 QAM rates are maximum gain, and the remainder maximum throughput.

When set for maximum gain, system gain is increased by between 3dB to 4dB compared to maximum throughput. This applies on all modulation steps. At the same time capacities are typically reduced by between 8% and 18%. Generally, the higher the modulation rate, the lower the % capacity reduction.

This feature provides a practical trade-off between capacity and system gain to fine-tune link performance.

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

For example, a 10 MHz RF channel that supports an air-capacity of 15 Mbit/s using QPSK, expands to 126 Mbit/s using 256 QAM adaptive modulation, then doubles to 90 Mbit/s using CCDP.

Investments in

existing channel

plans can be

maximized using

Eclipse CCDP

and adaptive

modulation.

Similarly, a 50 MHz RF channel that supports an air-capacity of 78 Mbit/s using QPSK, expands to 325 Mbit/s using 256 QAM adaptive modulation, then doubles to 650 Mbit/s using CCDP.

Under CCDP two parallel communication links are operated on the same RF channel; one using the vertical polarization, the other the horizontal. Cross Polarized Interference Cancellation (XPIC) is used to ensure any interference between the channels is eliminated.

• The capacity on each link can be used for IP traffic (Ethernet), TDM, or IP + TDM.

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

CCDP Links can be 1+1 or ring protected.



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Figure 10. 650 Mbit/s Link Aggregated Mixed Mode CCDP Terminal

Figure 11. 650 Mbit/s Link Aggregated RSTP CCDP Ring Node

Where even higher capacity links are needed, three or four links can be installed. For example, two CCDP link pairs (four links in total) support up to a 1.5 Gbit/s air capacity, and in excess of 2 Gbit/s at L1.

Ethernet Data Optimization Data optimization techniques supported on Packet Node include:

• IFG and Preamble suppression

• MAC header compression

• Statistical Mux Gain

• Abis and IuB data optimization on pseudowires

IFG and Preamble Suppression and MAC Header Compression

This involves a reduction of the byte-count used to transport Ethernet data end-to-end over a Packet Node link. Essentially, Ethernet frame bytes that do not carry payload data are suppressed or compressed for transmission over the link, and re-instated at the far end.

With IFG and Preamble suppression, the 20 bytes are replaced by 4 bytes. This 16 byte reduction in frame space represents a 23 % throughput improvement on 64 byte frames, or 6% on average-size 260 byte frames.



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With MAC header compression, the 12 bytes are replaced by 2 bytes. When this is added to the 16 byte reduction from IFG and Preamble suppression, it represents a 45% throughput improvement on 64 byte frames, or 10% on 260 byte frames.

• Throughput figures quoted at Layer 1 normally highlight the throughput for the smallest 64 byte frames, which provide a maximum indication of bits-per-second. For Eclipse Packet Node this equates to an industry-leading single-link throughput capability of 540 Mbit/s on an 80 MHz channel, or 460 Mbit/s on a 50 MHz channel.

• Layer 2 throughput figures have traditionally and more realistically presented Ethernet throughput, as they look only at the Ethernet frame; IFG and preamble bytes are ignored. Measurement is specified in the IETF (Internet Engineering Task Force) document RFC 2544, to provide a standardized test methodology for the industry.

Whichever way you look at it, whether L1 or L2, Eclipse Packet Node is unmatched in its ability to efficiently transport Ethernet traffic. Statistical

multiplexing

helps extract

maximum

capacity from a

network.

Statistical Mux Gain

This results from multiplexing a number of Ethernet links onto a common link that has a lower capacity than the combined capacity of the individual links. It takes advantage of the bursty nature if IP data where some user bursts correspond to other users' off periods, thereby smoothing the variations in the aggregate traffic, and consuming a lower peak bandwidth.

Gains of more than 30% can be realized. It particularly applies in Ethernet backhaul networks where traffic from multiple sites is aggregated onto a common ‘pipe’. It means that arterial backhaul links can be sized lower than the sum of the individual links at the point of aggregation. Figure 12 illustrates the concept. Compared to the locked-up bandwidth on dedicated TDM circuits, Ethernet aggregation and statistical muxing means less bandwidth is needed to transport the same amount of data. Conversely, statistical muxing extracts maximum efficiency from the available bandwidth. Figure 12: Comparison of Aggregated TDM and Ethernet Traffic Bandwidth

If bandwidth is contested, Ethernet QoS settings can be applied to support priority traffic within individual streams, or to a total stream.

Packet

optimization gives

maximum

performance with

lowest cost.

Abis and Iub Data Optimization

This applies where GSM Abis or Iub UMTS TDM base station connections are captured on pseudowires (PWE3) for transport over an Ethernet network.

Typically the PWE3 encapsulation process adds overheads of up to 15%. This is offset through intelligent optimization, which removes idle cells, idle frames, idle timeslots, silence, and other redundant information on the TDM (Abis) and ATM-IMA (Iub) links.

These techniques can provide reductions in bandwidth usage of more than 50% on Abis links and 40% on lub ATM links.



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Link Aggregation

L1 and L2 link

aggregation

options support

all network

topologies.

Link aggregation is used to combine two or more links into a single logical link to provide a traffic capacity that is the sum of the individual links.

It is especially relevant to wireless links where traffic capacities higher than the maximum possible on the radio channel for one link are required - two links are operated in the same RF channel using CCDP, then link aggregated to provide one logical link of double the capacity.

Link aggregation also provides redundancy. If one link fails, its traffic is redirected onto the remaining link(s). Effectively this is N+0 protection – all links in the aggregation group carry traffic, and provide protection for each other.

If the remaining link(s) do not have the capacity needed to avoid a traffic bottleneck, QoS settings can be set to ensure all higher priority traffic continues to get through.

These capabilities also support route diversity where, for example, a radio link is aggregated with a wireline link to provide additional capacity and route protection.

Uniquely, Eclipse Packet Node 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 connections.

Capacity Migration Collectively, adaptive modulation, CCDP, data optimization, and link aggregation add to provide unmatched 2G to 4G capacity migration potential. This is illustrated in Figure 13, which shows possible migration steps for ETSI channel bandwidths. Eclipse presents

exceptional

migration options.

Figure 13: Capacity Migration

The incremental

cost of overlaying

Ethernet on

existing Eclipse

TDM links is

minimal.

Converged Network Operation While converging services onto a common all-Ethernet network may be an ultimate goal, before this is realized most operators will take the interim step of supporting both Ethernet and TDM. This may be followed by parts of the network being Ethernet, and other parts TDM, or Ethernet + TDM. The associated issues addressed by Packet Node include:



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• Transport of legacy TDM traffic over Ethernet

• Synchronization of base stations over Ethernet

• IP/MPLS Built-in site

aggregation

means costly

stand-alone

aggregation

devices can be

eliminated from

the access

network.

Pseudowires for Legacy PDH Traffic Pseudowires provide a means to encapsulate legacy DS1 circuits for transport over Ethernet. Packet Node supports:

• Unframed DS1 according to SAToP

• Framed DS1 according to CESoPSN

• HDLC over DS1 according to RFC 4618

• Optimization of 2G Abis (GSM) and 3G Iub (UMTS) framing protocols on CESoPSN DS1/DS1 terminations

Industry-standard IETF pseudowire operation is used to ensure interoperation with equipment from other vendors.

16 pseudowire connections are supported per Packet Node convergence card, which also includes synchronization options for pseudowire DS1 clocking.

Synchronization For mixed-mode links the DS1 (G.823) clock will continue to be used. But with migration to an all-Ethernet backhaul the timing requirements must address:

• Synchronization of 2G cells supported on pseudowires.

Sync solutions

from 2G to 4G.

• Synchronization of 3G UMTS eNodeB cells.

• Synchronization of 4G TDD cells for both frequency and phase (relative time).

The Packet Node solutions include Distributed Sync, Synchronous Ethernet, and support for IEEE 1588v2.

Packet Node Distributed Sync solves 2G and 3G timing requirements. A DS1 / G.823 compliant clock is transported in the link overhead to support base station synchronization directly, or indirectly via pseudowires. Payload is not affected.

The clock will typically be sourced at the core end of the network from the PRC, DS1 frame, or Synchronous Ethernet. It is delivered from Packet Node on DS1 framing or as a 1.544 MHz sinewave.

It is particularly applicable in networks where Synchronous Ethernet or 1588v2 are not an option, or at base stations only equipped to clock from DS1.

Synchronous Ethernet will be supported natively on Packet Node to distribute line-based frequency synchronization.

1588v2 frames are transported transparently by Packet Node to support packet-based solutions for frequency and phase synchronization.



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IP/MPLS Given the expectation that an MPLS capability will increasingly be needed to direct cellular IP traffic over shared (service aggregated) networks, the Packet Node solution is to provide an MPLS edge label switch router (eLSR). This option will label traffic towards the MPLS core, and conversely will be the last point in the network to direct traffic towards a base station. It may be located right at a base station, or at a site aggregation node.

Eclipse Packet

Node makes it

easy to migrate to

an IP RAN. Conclusion Packet Node transforms networks to all-IP. You can single-step from TDM to all-IP, or go step-by-step starting with an overlay of Ethernet on existing TDM links, and adjusting the overlay to ultimately reach an all-IP goal.

At each step there is a low-cost card-based solution to support required network infrastructure for more capacity, better spectral and data efficiency, wider redundancy options, tighter QoS, sync options, and legacy traffic support.

This incremental approach has much to recommend it. Change can be made without the risk, downtime and expense often associated with a complete platform change-out. No other node offers the flexibility, scalability, low-cost migration, reliability, and ultimate sophistication and capacity grunt for next generation wireless backhaul.





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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. FDD Frequency division duplex. 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 / OC1) and 155.52

Mbit/s (STM1 / OC3) through to 10+ Gbit/s. SFP Small-form-factor pluggable. SLA Service level agreement. TDD Time division duplex. 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.

microwave backhaul enables mobile network...

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