8/4/2019 Resilient Synchronous Gigabit Ethernet for True 4G Mobile Backhaul Network

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Resilient Synchronous Gigabit Ethernet for True 4G

Mobile Backhaul Network 

Over the next several years, LTE

worldwide deployments bymobile operators will continue togrow in support of the increasedbandwidth demands being drivenby new data services.

According to Cisco's recentprojections, there will be a 92%compound growth rate in mobiledata traffic from 2010 to 2015and 5.6 billion personal devices

will be connected to mobilenetworks by 2015. 2G and 3Gservice subscriptions will bearound for quite some timealthough this number will dropsteadily with the growing adoption of 4G/LTE services, according to InfoneticsResearch (www.infonetics.com). (See Figures 1 and 2.)

Connection speeds of mobile devices increase with each new generation; 2G,3G and 4G mobile devices are designed to handle speeds of 230 kbps, 14Mbps and 1 Gbps, respectively resulting in a 15-fold increase in bandwidth

capacity requirements as more subscribers convert to 4G services.

Building the next generation mobile network in support of these trendsrequires careful consideration of all the building blocks that make up thenetwork. Mobile backhaul is a critical component, playing a pivotal role in theoverall performance of the network. It connects to multiple cell sitessupporting thousands of roaming subscribers and must efficiently handlechanging traffic patterns.

The widely deployed TDM and circuit-switched backhaul networks, such asSONET/SDH are recognized as highly resilient and reliable but are expensiveto operate and the shift toan all-packet mobilebackhaul is driven by theneed to lower the totalcost of ownership. For this reason, Ethernet istoday's choice for mobilebackhaul. The projected mobile

landscape calls for a true4G Ethernet mobile

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backhaul network – one that is capable of providing simultaneous support for multiple generations of high quality services – while efficiently handling theexponential increase in data traffic that will traverse the network.

A true 4G Ethernet mobile backhaul network must meet three fundamental

design requirements – resiliency that provides five 9's availability,synchronization of real-time services and low-latency, line-rate performance.The objective is to provide subscriber's access to the highest level of servicequality at anytime from anywhere while providing the scale to meet futurebandwidth capacity requirements. Two types of Ethernet mobile backhaul deployments include the Multi RadioAccess Network (RAN) and Resilient Microwave Access Ring. (See Figure 3.) In the multi-RAN, cell-site routers with multiple T1/E1 and Ethernet ports aredeployed at the cell site and collect traffic from 2G, 3G and 4G radio towers

for handoff to the mobile backhaul over fiber or copper. Built-in pseudowirecapability converts T1/E1 connections from 2G and 3G services to Ethernetmobile backhaul to enable the simultaneous support of all three generationsof services over the same backhaul network. This is an important requirementgiven the wide deployment of 2G and 3G base stations and mobile operatorshave a need to preserve existing investments as new radio towers aredeployed for LTE services.

At the cell-site aggregation, cell-site aggregation routers are connected to viamultiple, resilient synchronous Gigabit Ethernet rings and are responsible for aggregating multiple Ethernet links from various cell sites and routing thetraffic to the mobile core.

Resilient microwave access rings will be commonly deployed in many parts of the world where microwave deployments are a predominant choice for backhaul access due to its relative low-cost. Ring configurations, as opposedto the commonly deployed point-to-point configuration provide both highcapacity and the required level of resiliency.

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 Resiliency  An important component to achieving five nines availability is through theimplementation of packet ring resiliency protocols, namely, ITU-T G.8032 andRFC 3619 Ethernet Automatic Protection Switching (EAPS) both at the cellsite for microwave access rings and at cell site aggregation for theimplementation of multiple resilient Ethernet rings. G.8032 and EAPS provideprotection switching; EAPS is a proven technology currently deployed inthousands of service provider networks around the world today andG.8032 isa standard that builds on the proven success of EAPS. Depending on the

requirements, mobile operators with EAPS already deployed in their network,can choose to migrate to G.8032.

8/4/2019 Resilient Synchronous Gigabit Ethernet for True 4G Mobile Backhaul Network

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 Synchronization Synchronization is enabled through IEEE 1588v2 (also referred to asPrecision Time Protocol, or PTP) and ITU-T G.8261 Synchronous Ethernet

(SyncE). Real-time traffic synchronization is crucial to ensure a smooth radiotower to radio tower handoff during roaming in order to avoid dropped voicecalls and to maintain the required quality of service. These protocols ensurethe same level of service performance supported by legacy backhaulnetworks based on T1/E1 and SONET/SDH technologies that achievesynchronization of real time services using Time Division Multiplexing.

As a physical layer protocol, SyncE derives its reference timing signal from aclock source such as Building Integrated Timing System (BITS). The physicallayer of the Ethernet port is used to distribute the clock frequency among allthe nodes in the network. It provides the benefit of predictable service

performance independent of the amount of traffic traversing the network.1588v2 distributes both time and frequency, operates at a higher level(Ethernet/UDP) and utilizes time stamps to synchronize the network nodeswith a master clock. In certain deployments, the two protocols are usedtogether in hybrid mode where the frequency is obtained through SyncE andtime of day is obtained through 1588v2. Line-Rate Gigabit Ethernet Access and 10 Gigabit Uplink Ports Single or multiple ports of gigabit line-rate access at the cell site to the mobilebackhaul provides ample current capacity and more links can be added toaddress the future data traffic growth. Additionally, the cell-site aggregationrouters that provide high-density line-rate gigabit Ethernet rings are crucial for scalable service performance. High capacity connections to the mobile coreand intra-ring connections are achieved via single and multiple full line-rate 10Gigabit links. Summary  In order to enable true 4G services, the Ethernet mobile backhaul networkmust provide a combination of resiliency, synchronization, and full capacity

line-rate GbE and 10 GbE performances. It is essential to meet subscriber expectations in service quality for all generations of services while preparingfor the explosive mobile data traffic growth over the next decade and beyond.