Meet the Needs of LTE Backhaul with the Tellabs 8600 Smart Routers

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2 MEET THE NEEDS OF LTE BACKHAUL WITH THE TELLABS 8600 SMART ROUTERS small cell. This kind of architecture also demands an additional, and extremely cost-optimized, aggregation capability at the connected macro sites. In some cases, operators may even need an external transport device next to the small cell site device. This will create a clear demarcation and aggregation between the radio and backhaul domains. Tellabs 8600 Routers Enables Flexibility in LTE Backhaul To address the architectural changes in LTE networks described above, operators need backhaul networks that provide more flexibility for IP connectivity than just pure point-to-point or hub and spoke topologies. IP routing inherently provides a scalable and manageable forwarding mechanism for the multipoint-to-multipoint IP connectivity that LTE backhaul requires. IP routing also ensures flexibility for possible changes in future LTE backhaul architectures. MPLS functionality, on the other hand, enables needed traffic separation and tight control of traffic flows including end-to-end resiliency. BGP-based MPLS IP VPN is an optimal option to separate traffic flows in the different LTE interfaces, as proposed in Figure 2. Figure 2 highlights the high-level architecture of an LTE backhaul network with the Tellabs ® 8600 Smart Routers. By separating IP routing domains with different VRFs, this architecture provides clear visibility of the different connections for planning, provisioning, monitoring and troubleshooting activities. IP VPN for the S1-U and S1-MME provides point-to-point connectivity between eNodeBs and S-GW and MMEs, which may be collocated. As the LTE network grows, operators can utilize additional S-GWs and MMEs for resiliency and to extended capacity. As a result, operators will need to home the connections from an eNodeB to these additional S-GWs and MMEs. The initial point-topoint connection becomes a point-to-multipoint connection, where the S-GWs and MMEs are reachable from all eNodeBs. Operators must add additional end-points to the S1 IP VPN flexibly, without interruption to existing traffic. The topology requirement for the X2 interface is different from the S1 interface. So, operators may be able to utilize a separate IP VPN for the X2 interface between a group of neighboring eNodeBs. This applies if the X2 traffic does not need to pass through a centralized IPsec gateway. This IP VPN is already initially multipoint-to-multipoint in nature. This is because the eNodeBs require connectivity to the neighboring eNodeBs, and they require a reliable X2-based handover capability. In the initial phase of LTE deployments, the X2 interface may not be necessary. This is because the first phase end devices require reduced mobility (i.e. dongles for laptops), deployments are limited and the number of users is fewer. These factors result in a modest number of handovers. However, LTE-based mobile user devices (i.e. smart phones) become more widespread and the networks will expand. Then, the X2 interface will likely be used to limit the signaling load on the MME and to provide more reliable and lossless handovers. As seen in Figure 3, the traffic separation using the IP VPN architecture may start already at the cell site. The VLANs associated with the different LTE interfaces and handed over by the eNodeB are terminated at the first physical interface in the backhaul network. Access Aggregation Core VRF VRF VRF 8609 eNodeB VRF eNodeB VRF VRF VRF VRF VRF IP VPN for 3G IP VPN for LTE IP VPN for OAM VRF 8000 INM 8630 8600 8600 VRF VRF VRF 8607 eNodeB (IP) VRF VRF 8611 VRF 8660 VRF 8600 8600 VRF VRF 8609 eNodeB eNodeB VRF RNC(IP) Figure 2: IP VPN design optimizes LTE Backhaul S-GWs MMEs See tellabs.com for more information about Tellabs Solutions
3 MEET THE NEEDS OF LTE BACKHAUL WITH THE TELLABS 8600 SMART ROUTERS Therefore, the VLAN scalability and management, in addition to the Ethernet broadcast domain planning have already been tackled inherently. The aggregation device at a macro cell site functions additionally as an aggregation and demarcation device for possible small cell sites located in the area. Operators also need connectivity between the network elements (both RAN and backhaul) and the operations center. This includes the management connectivity between the Tellabs ® 8000 Intelligent Network Manager (INM) and the Tellabs 8600 network elements. Another IP VPN can help accommodate this OAM traffic. Small Cells VRFs VLANs OAM 86113G IP X2 S1- U/MME Figure 3: IP VPN based traffic separation at cell site Macro Cell a) ASy Growing and Dynamic LTE backhaul networks need a Hierarchical IP VPN Architecture Operators with growing and dynamic LTE backhaul network can address scalability with a hierarchical IP VPN architecture using the Tellabs 8600 LTE backhaul solution. Figure 4 depicts the different alternatives to address iBGP neighbor scalability and IP address scalability. To limit the number of direct iBGP neighbors, operators can use the route reflector model depicted in Figure 4 part c). Operators can additionally limit the number of IP routes to be advertised in the network, as depicted in Figure 4 part b). To do this, operators can use route aggregation at the Autonomous System Border Router (ASBR). To learn more about these architectures including the Tellabs developed inter-AS option for IP VPNs, read Tellabs’ IP VPN Application Note at www.tellabs.com. LTE Backhaul Networks Need Better Security LTE networks have different backhaul security requirements than 2G and 3G networks. LTE’s basic goals include high data-throughput rates, improved spectrum efficiency, reduced latency, improved coverage and packet-based support for multiple radio access technologies. These goals are driving the evolution of the mobile network to a more efficient, all-IP infrastructure. IP-based transport is more open and therefore more vulnerable than transport based on TDM technology. 8600 PE 8600 PE iBGP 8600 PE 8600 iBGP PE 8600 PE 8600 PE Flat IP VPN Full iBGP mesh b) c) ASx ASy ASy 8600 U-PE 8600 PE 8600 U-PE eBGP 8600 ASBR 8600 iBGP N-PE 8600 PE iBGP 8600 RR 8600 iBGP PE 8600 U-PE 8600 N-PE Hierarchical IP VPN Tellabs InterAS-option 8600 8600 PE PE Hierarchical IP VPN Route Reflector based Figure 4: Enhanced Scalability Options for IP VPN Architectures See tellabs.com for more information about Tellabs Solutions
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Meet the Needs of LTE Backhaul with the Tellabs 8600 Smart Routers

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