SDN-based mobile backhaul Network: LTEHaul

The commercial scale of LTE/LTE-A has brought about the birth of a series of new technologies. 3GPP defines and develops new wireless technologies. Starting from R11, the key is CoMP and eMBMS. CoMP (Coordinated Multiple Points) refers to Multiple site antennas, including service cells and adjacent cells, that receive/transmit messages in a cooperative manner to improve the quality of user reception signals, new technologies that reduce inter-cell interference, improve cell edge user throughput, and average cell throughput. EMBMS (Evolved Multimedia Broadcast/Multicast Service) has a one-to-many transmission advantage, so as to more efficiently use the existing spectrum and mobile network, to provide users with higher quality, greater bandwidth content technology, at the same time, it increases the network transmission efficiency of the same frequency and changes interference to gain.

We know that in traditional GSM/UMTS mobile backhaul networks, all base station services must first converge to BSC/RNC, which sorts and determines the processing of different types of services. This physically splits Backhaul and Core to form a network topology. From the perspective of user bandwidth, the maximum bandwidth throughput of GSM/UMTS base stations is only 42 Mbps, which forms a significant gap between the bandwidth capability of the network and the bandwidth demand of users.

The core of LTEHaul is the new technology brought by LTE/LTE-A, which provides ultra-broadband, Zero Wait and ubiquitous connection, so as to bring users a high-speed, high-quality and simple free sharing business experience. LTEHaul connects FrontHaul, Backhaul, and Core from the network architecture, spanning the traditional GSM/UMTS architecture and bandwidth bottlenecks. At the same time, it achieves load-carrying and control separation through SDN technology, massive remote CSG (Cell Site Gateway) and SCSG (Small-cell Cell Site Gateway) can implement centralized management and automatic business configuration on ASG (Aggregation Site Gateway, this not only greatly simplifies management and O & M, but also helps operators save more than 60% of OPEX and enables fast deployment of new services.

LTEHaul architecture changes

The continuous growth of MBB traffic and the features of large LTE bandwidth (150 Mbps/eNB, planned data of a mobile operator in China) determine that in dense urban areas, high-frequency spectrum Wireless Network (2.6/3.5 GHz) is an inevitable choice. The coverage capability of high-frequency LTE base stations is far smaller than that of the current GSM/UMTS base stations. This means that more base stations are needed to supplement the coverage, and the number of sites will increase linearly by 10 times. At the same time, high-frequency spectrum wireless networks bring about large bandwidth services (peak bandwidth is 10 times higher than 3g), but also generate hot spots and blind spots, FrontHaul scenarios.

1. Compared with the traditional GSM/UMTS architecture, the LTEHaul network architecture has two changes: FrontHaul is located before Backhaul, BSC/RNC nodes disappear, and Backhaul and Core are pulled through the architecture.

FrontHaul = indoor hotspot + outdoor hotspot

FrontHaul occurs before the Backhaul of traditional GSM/UMTS. It can be divided into two scenarios: indoor hotspot and outdoor hotspot. In addition, indoor hotspot coverage is classified into wi-fi and Small cell scenarios.

Wi-Fi Mobile return scenarios are mainly concentrated in mobile office areas, coffee shops, airports, and other places. Due to the poor user mobility and coverage of GSM/UMTS networks, the common requirement for these scenarios is to ensure the quality of a large amount of data services, regardless of voice coverage and roaming. In this scenario, the diversity of backhaul media (P2P optical fiber, PON, copper wire, etc.) and the difficulty of using RRU for power supply exist. Therefore, the ability of any media access and remote POE power supply are particularly important. In addition, a large number of remote nodes need to be maintained, and OPEX costs are high. This requires that the backhaul network must be easy to install (plug-and-play), maintenance-free (access virtualization), and hard with smaller size and lower power consumption.

The scenarios of Small cell return are mainly concentrated in shopping centers and other areas. It features strong user mobility and wide coverage areas, and a large number of voice and data business access. In these scenarios, we must not only ensure the user's voice and data service experience, but also ensure the rapid deployment of services. This requires that the backhaul network not only has the access capability of any media and the remote power supply capability of RRU, but also has strong H-QoS scheduling capability. At the same time, easy to install, maintenance-free, and out-of-the-box use are the basic requirements for TCO cost reduction.

Outdoor hotspot coverage mainly refers to the outdoor scenarios of Small cells, mostly distributed in the bustling pedestrian streets, city squares, open-air coffee shops and other areas. These regions are characterized by high traffic, high traffic volume, and band-based traffic distribution. Their main features are the complex site deployment environment (which must be installed on walls, lamps, and poles) and return the diversity of resources.

The complex site deployment environment requires that the return device be able to access all outdoor devices with "0 site" and be friendly. It is also easy to conceal, waterproof, and lightning-proof, and highly adaptable to the environment. The diversity of backhaul resources refers to the existence of P2P optical fiber, copper wire, GPON and other access resources in the street cabinet resources, which requires the backhaul equipment to support the access capability of any media and the clock synchronization capability of any media. For scenarios where no wired resources are available, full-outdoor microwave is the only choice, and features such as rapid deployment (spherical microwave quick focus), quick activation (USB configuration), and maintenance-free are the basic requirements.

Backhaul CSG: evolution from end nodes to aggregation

The CSG node of the traditional GSM/UMTS Backhaul is the last kilometer. However, in the LTEHaul architecture, Backhaul becomes a collection point, and the traffic covered by the hotspot station is eventually aggregated to the Backhaul CSG node. The change in network architecture requires telecom-Grade 1 + 1 10GE ring network protection, dual-master backup, and multi-point fault resistance.

With the maturity and commercial deployment of VoLTE voice solutions, the frequency of GSM/UMTS will evolve to LTE Refarming. The wireless Blade RRU solution supports LTE Refarming with a 4-mode 7-frequency model, which requires that the CSG nodes that are returned have multi-board business access (6 Business Board locations) large Capacity (400g switching capacity), smooth support of LTE-A (currently commercial LTE-A per base station throughput has reached Mbps, will reach 1 Gbps) Evolution and upgrade capabilities. At the same time, the VoLTE voice service requires the CSG to have multi-service scheduling and quality assurance capabilities with H-QoS.

On the other hand, CSG and wireless BBU are physically located, which requires that CSG devices can work with BBU in cabinets, power supply, and network management, and can be plug-and-play, rapid deployment with the progress of wireless base stations.

Backhaul ASG: FMC fusion start point, with a total of OLT/SDH access data centers

With the evolution of base station IP and the rapid growth of data traffic, FMC's IP bearer network nodes move down to the traditional OLT/SDH access data center location. The typical features of cabinets in the access data center are 300mm deep. Mobile Traffic and fixed traffic are aggregated here. This requires that the ASG node devices have a large capacity (not less than 480 GB) and a depth of 300mm (available on existing website resources ), it can work with OLT/SDH cabinets, power supply, and network management to achieve cost saving and rapid deployment, at the same time, it is required that the FMC service processing capability that integrates BRAS, SR, and vpn pe should be able to achieve future-oriented New Business evolution capabilities (eMBMS requires multicast, L3, IPv6, and other features ).

As the LTEHaul network is large and complicated, it puts a lot of pressure on O & M management. When the macro station and small station traffic converge to the ASG node, the ASG node is also responsible for managing the massive number of Remote csg sdn: Remote module Centralized smart Management (Remote-module Centralized Intelligent Management). The introduction of centralized and intelligent management of remote modules not only simplifies business configuration and management, but also undertakes O & M capabilities for fault alarms and Protection Switching, significantly reducing OPEX costs.

Core: exclusive lte pe to ensure rapid delivery and O & M of E2E services

In the traditional GSM/UMTS mobile return network architecture, BSC/RNC separates Backhaul and Core. In the LTEHaul network architecture, the network function of BSC/RNC is moved down to eNB, and the function is moved to EPC. Therefore, the features of eNB and EPC, such as service delivery, protection switching, and fault locating, require end-to-end communication. The traditional back-to-back Option A's network creation mode cannot meet the needs of 50 ms cross-Origin Protection Switching. The solution of LTE exclusive PE Labeled BGP + HVPN solves this problem.

At the same time, the characteristics of LTE/LTE-A bandwidth, but also solved the problem of lack of resources in the last mile of the mobile operator's enterprise leased line business, making the enterprise leased line become the current Taurus business of LTE/LTE-A. In the network architecture of traditional Option A, segment-based service configuration leads to A long issuance time for enterprise leased line services. In addition, due to the lack of E2E fault locating capabilities, it is difficult to ensure rapid service recovery. The Labeled BGP + HVPN solution solves the N2 scalability problem of connecting eNB and EPC, and also meets the needs of fast delivery and Fault Locating of enterprise VPN services.

SDN evolution: Unified Control Plane for wireless and bearer Solutions

The evolution of LTEHaul SDN architecture is divided into three steps: first, building an All IP architecture based on NP (Network Processor) is the cornerstone of SDN; second, centralized and intelligent management of remote modules, it simplifies O & M and business configuration, and solves the challenges brought by new LTE/LTE-A services. Step 3, unified control platform, pull the wireless side SON (Self Optimization Network), SRC (Single Radio Controller) control Plane to build E2E solutions.

With the commercialization of LTE/LTE-A, the future mobile bearer network needs to carry more new services, support more application scenarios, but also brings more new challenges to the existing bearer network. Huawei's LTEHaul solution will help carriers to smoothly evolve towards LTE-A across mobile return troughs.