By Li Sheng
China Unicom Shanghai has leveraged the advantages of the network management system (NMS) to implement its IP RAN network, which is now as easy to operate and maintain as an SDH network.
A s its largest city, Shanghai is taking the lead in China in terms of WCDMA/LTE development. China Unicom Shanghai (Shanghai Unicom) plans to invest RMB12 billion (USD1.9 billion) into its network infrastructure over the next three years. Its 3G base stations will total 13,000, while its transmission rate will jump from 7.2 to 42Mbps. These developments will certainly put further strain on Shanghai Unicom's backhaul network. After considering the future demands of bearing LTE and high-value fixed services, Shanghai Unicom selected IP RAN for the building of its multiservice bearing network, the evolution of which will pose new challenges for its operation & maintenance (O&M) practices.
Key challenges for IP RAN O&M
IP O&M skills
Shanghai Unicom's multiservice bearing network will comprise more than 5,000 pieces of equipment, the daily maintenance of which will be performed by its regional maintenance centers (nearly 100 members per team). However, its current regional O&M personnel know more about transmission & access than about IP O&M techniques. IP RAN involves dynamic IP protocols such as IP/MPLS, but IP technology is very complex; it would take more than a year for O&M personnel to master the relevant skills. Clearly, this period needs to be shortened.
The China Unicom Group has more than ten specifications regarding transmission, FTTx access, IP network equipment, NM, and OSS, which provide effective guidance for daily maintenance. However, IP RAN is a new technology that bears high-value services and technologies (WCDMA/LTE, private lines for official and corporate entities, and video). Operating such a large IP backhaul network with quality and efficiency would be nearly impossible without O&M standardization.
Shanghai Unicom uses an integrated OSS NMS for centralized monitoring/control of its Internet backbone and IP metropolitan area network (MAN). It also utilizes an NMS from its equipment supplier for auxiliary monitoring/control of warnings and performance. Configuration and troubleshooting are performed through the command line. The operator will add over 5,000 pieces of IP RAN equipment over the next three years; timely network deployment and base station activation/adjustment will be critical. Wireless users are demanding and fickle. O&M personnel must identify latent issues in the network before they emerge, but this is more than what Shanghai Unicom's previous IP OSS could enable.
In 2010, Shanghai Unicom selected Huawei for its IP RAN service-bearing network project. Both parties analyzed and explored IP RAN O&M in depth, and the results have so far been satisfactory.
Simplified architecture, easier O&M
Daily network maintenance includes preventive maintenance, daily monitoring, service activation, troubleshooting, and network analysis. The SDH network comprises thousands of devices and services, leading to frequent base station activation and adjustment (over 100 instances per day). However, O&M can still be conducted easily through visualized configuration of the NMS.
Shanghai Unicom found IP RAN to be very similar to traditional SDH networking in terms of maintenance. It is almost unfeasible to maintain massive amounts of IP equipment by using the command line interface (CLI). The NMS must neutralize the complexities of IP networking through fixing, simplifying, and visualizing the command line; this allows O&M personnel to perform daily tasks in simple steps, which saves time and minimizes training costs.
Traditional CLI-based maintenance is a single-point operation where equipment is isolated and manually correlated to ensure smooth and accurate maintenance. IP RAN architecture typically involves thousands of pieces of equipment, totaling roughly 10,000 links and hundreds of thousands of logical interfaces; with this many points involved, the aforementioned maintenance methods are clearly impossible.
Shanghai Unicom uses its NMS to manage critical IP network resources in a "network+services" manner, thereby visually correlating its network resources. The operator presents physical and clock links through a topology that enables a clear view of network status. Like the E1 circuit and VC4 path for the SDH network, which correlate network resources, Shanghai Unicom abstracts Layer 2/3 VPN and TE tunnels that bear base stations into service resources for E2E management, making the bearing relationships for base stations as clear and simple as those for SDH.
Shanghai Unicom now estimates that its O&M personnel can master service activation after a mere three to four weeks of training.
Enhanced efficiency through O&M standardization
Shanghai Unicom had more than a decade of experience with traditional SDH and IP networks, so it had numerous entrenched O&M specifications/practices that would have to be overcome if IP RAN deployment was to be successful.
The operator worked with Huawei to draft the Daily IP RAN Maintenance Operation Plan, Configuration Specification on IP RAN Base Station Service Activation and Adjustment and the IP RAN O&M KPI & Assessment Recommendations, based on the current China Unicom Communication Network O&M Procedures – Network Equipment and the MEF standards for IP backhaul networks. All of these documents refined Shanghai Unicom's daily O&M procedures for the IP RAN era.
Shanghai Unicom has made it clear that all service configurations and adjustments must be performed through the NMS; the consistency of newly configured and existing data should therefore be verified. In the event of conflict in configuration, O&M personnel will be notified, which ensures configuration accuracy and compliance while reducing the risk of human error in the equation.
GSM/WCDMA/LTE base stations are more demanding on mobile backhaul. Shanghai Unicom analyzed the MEF quality requirements for WCDMA/LTE service bearing and has clarified its quality requirements for IP RAN bearing. Based on these standards, the operator defined two critical indicators for IP RAN operations, namely the base station and regional quality compliance rates. The latter serves as a critical indicator for assessing maintenance performance for each regional repair center as it drives proactive network maintenance.
Shanghai Unicom's OSS NMS is centralized and vendor agnostic, while Huawei's NMS solution has advantages in terms of network and service understanding; the latter also enables a deeper understanding of the Huawei O&M interface. Shanghai Unicom leverages its OSS for centralized alarm monitoring and management across the IP RAN, backbone network, and NGN bearer networks; which is done primarily by first-line monitoring personnel. On the other hand, Huawei's NMS enables a focus on network deployment, base station service activation and adjustment, network quality monitoring and early warning, as well as troubleshooting, by second-line support personnel.
Based on the unified specifications, Shanghai Unicom simplified certain base station activation and adjustment scenarios. It has successfully deployed nine access rings and activated more than forty base stations for service provisioning. According to its O&M personnel, "U2000 NMS is very similar to the SDH NMS in terms of the activation efficiency and operation experiences."
Since dynamic routing protocols were deployed in the IP RAN, accurate fault location was the key challenge. Shanghai Unicom responded by using the NMS to encapsulate those dynamic and connectionless configurations into a visualized path for base station bearing and then encapsulate various smart troubleshooting methods based on that path, thereby enabling automatic location of specific faulty equipment and ports.
On a certain day, the wireless department reported that "3G voice quality is poor with frequent call drops (in a certain apartment complex)." This occurred during peak hours, so the O&M personnel were under heavy pressure. They promptly used the U2000 NMS to check the forwarding path from the base station to the RNC and then initiated fault diagnostics. The fault was identified within ten minutes and cleared within twenty. Thanks to the simplicity of these processes, O&M personnel no longer need accumulate experience through use of the command line over a long period. Instead, two to three weeks of training are sufficient for them to acquire the acumen needed for basic troubleshooting.
During implementation of its pilot integrated IP RAN bearer network, Huawei's NMS proved its utility in terms of deployment efficiency, service activation speed, ease of troubleshooting, and performance monitoring/control. This solution has enabled the rapid completion of Shanghai Unicom's IP RAN, in a manner no more complex than it would be for SDH.
IP represents the future of networking. Shanghai Unicom will continue exploring and enhancing its O&M skills, increasing OSS capabilities, and improving O&M specifications to create an advanced and efficient IP network O&M system.