Building Tower-Aware LTE Backhaul Networks

By Kevin Wade

Wireless operators’ accelerating 4G/LTE deployments are giving rise to what many would characterize as a “sea change" in wireless backhaul infrastructure. Beyond the well-known 10x bandwidth increase from prior generation (3G) technology, and the somewhat-related FTTT (fiber-to-the-tower) migration, perhaps the most fundamental change associated with LTE is the mandated switch from a TDM-based backhaul architecture to one based entirely on Ethernet.

The shift to Ethernet-based transport for LTE wireless services creates both technological and business challenges for carriers who provide backhaul services. From the technology perspective, wireless operators are requiring that their backhaul providers commit to high levels of network availability and performance, backed by stringent SLAs (Service Level Agreements). Because Ethernet has traditionally been a connectionless, best-effort technology, this presents a challenge. New technologies enable backhaul providers to satisfy these demands by delivering deterministic, “SONET-like" performance for Ethernet networks.

Ethernet Makes the Connection

Ethernet technology has progressed from its roots as a connectionless LAN (Local Area Network) technology to meet these requirements. COE (connection-oriented Ethernet) signifies a major evolution of Ethernet that makes the technology suitable for use in service provider networks. Based on a combination of inter-related standards, which today includes IEEE 802.1Qay and ITU-T G.8031/G.8032 along with the developing IETF MPLS-TP standard, COE effectively transforms Ethernet into a transport technology. A key objective of the COE standards has been to provide Ethernet with traffic engineering functionality to allow more scalable and resilient transport of Ethernet services.

Modeled in many ways after SONET, COE enables the engineering of explicit connections that provide deterministic bandwidth and guaranteed QoS at each node along the defined path. Once end-to-end Ethernet connections have been provisioned through the Ethernet network, COE also provides carrier-grade Ethernet protection switching functionality equivalent to that provided by SONET (50 ms or less) over linear, ring, or multi-ring network topologies.

The predictable performance and topology flexibility provided by COE make the technology ideally suited for low-latency backhauling of Ethernet services from cell sites to the MSC (mobile switching center). By delivering deterministic bandwidth, guaranteed QoS and sub-50 ms protection switching, COE allows backhaul providers to deploy an Ethernet-based LTE transport network optimized for meeting wireless operators’ stringent SLAs for latency, jitter/delay, throughput and availability.

Solving the 10.1G Problem

Providing sufficient transport capacity to fiber-constrained tower sites is another technology challenge faced by LTE backhaul providers. As the number of towers per collector ring expands, and the quantity of wireless operators served per tower is increased, traffic growth can quickly exhaust 10 GbE uplinks on traditional Ethernet edge platforms. This capacity barrier has been referred to as the “10.1G problem."

Packet-optical technology was developed specifically to address this challenge. P-OTPs (packet-optical transport platforms) as their name implies, combine support for Ethernet packet switching and connection-oriented Ethernet with optical DWDM (dense wave division multiplexing) transport in a single system. Through DWDM integration, P-OTPs allow backhaul providers to maximize capacity of available fiber(s) at tower sites for high-density Ethernet service delivery and transport. Further, temperature-hardened P-OTPs are suitable for deployments at the cell site, in outside plant remote cabinets, to satisfy critical availability SLAs.

"Tower Aware" Backhaul Network Planning, Management and Verification

For backhaul providers to deploy a cost-efficient Ethernet backhaul network that utilizes COE and P-OTPs, they require software tools that allow them to plan and manage their networks for optimal end-to-end SLA performance. Additionally, many wireless operators are now requiring real-time service performance visibility from their LTE backhaul providers in order to verify that SLAs are being met. Because backhaul networks involve multiple network layers, multiple equipment vendors and multiple wireless operators, supporting this level of “tower awareness" can amount to a significant business challenge for backhaul providers. New tower aware software innovations allow backhaul providers to overcome these challenges.

Providing Real-time SLA Visibility

Improving service providers’ ability to support Ethernet SLAs has been a key objective of organizations such as the IEEE and ITU, as demonstrated by a number of Ethernet OAM (operations, administration & management) standards. The ITU-T Y.1731 Ethernet OAM standard is the most relevant to Ethernet SLAs. Y.1731 allows real-time and historical monitoring of individual customer connections at the service-level. A customer-service instance, also defined by the MEF as an Ethernet Virtual Connection (EVC), is the service that is sold to a customer. By enabling the measurement of per-EVC performance data collected from network devices such as frame delay, frame delay variation, frame loss and throughput, Y.1731 allows service providers to monitor Ethernet SLAs on an end-to-end basis.

Software innovations recently introduced to the market allow backhaul service providers to simplify the challenges associated with Ethernet SLA assurance. By making Y.1731 performance monitoring data accessible via an easy-to-use Web portal, wireless operator customers can quickly and easily verify that their SLAs are being met. The software provides a secure, services-layer (i.e. customer-specific) SLA portal that rolls up real-time and historical service performance information associated with the Ethernet connections between cell towers and mobile switching centers. Because the portal collects data from network using Y.1731, and other standards-based protocols in the future, the software is a multi-vendor system that works in conjunction with P-OTPs, Ethernet switches, NIDs and other standards-based equipment. The tower aware SLA visibility provided allows a backhaul provider to proactively deliver Ethernet SLA insight to their customers where needed, or can be a differentiating capability for new backhaul contracts. 

Multi-layer Management

Y.1731 enables performance monitoring at the Ethernet services layer, but network performance is not determined by this layer alone. Backhaul providers’ networks consist of multiple, independent network layers, each of which plays a role in determining end-to-end service performance. Depending on the provider, the network can include a physical fiber layer and rise up through the DWDM, Optical Transport Network (OTN), TDM/SONET, connection-oriented Ethernet (COE) and Ethernet service layers.

Historically, each of these layers has been managed and operated independently, without awareness of adjacent layers or services. However, new innovations in multi-layer management simplify operations and maximize performance of the backhaul network with complete OAM operating across all layers. Multi-layer network management also provides tower aware views using advanced 3-D visualization of individual backhaul connections and network resources to accelerate service provisioning and simplify fault correlation.

Optimizing Network Planning

Designing multi-layer backhaul networks is inherently a complex process. New innovations in network-planning software now allow backhaul providers to design multi-layer networks that are optimized for SLA performance. Multi-layer network planning software provides tower aware features through integration with Google Maps as well as Tower Grid data and other planning tools, which aid in traffic loading based on towers per ring for current and projected capacity planning. Advanced algorithms are utilized to characterize end-to-end performance of key parameters such as latency across all layers of the network and ensure the most efficient and economical network design for any given backhaul traffic requirement.

Conclusion

The shift toward Ethernet-based transport for LTE services creates new technology and business challenges backhaul service providers. “Tower aware" tools and technologies have recently been introduced that allow backhaul providers to overcome these challenges. These include innovative software systems for network planning, management and verification, connection-oriented Ethernet for providing deterministic bandwidth and guaranteed QoS, and packet-optical transport platforms for delivering capacity scalability. Used together, these tools and technologies enable backhaul providers to deploy cost-efficient and powerful Ethernet-based transport networks that are purpose-built for the delivery of LTE services with guaranteed SLAs.

In his role as product marketing director for Cyan, Kevin Wade is r esponsible for the company’s outbound, go-to-market activities. Kevin has more than 15 years experience launching new products into the service provider and enterprise markets , as well as successfully building their respective market shares.