Senior Engineer - 5G Core (RMI Core Network Operations Dep)

Job Description: About Organization Core Network Operations Department is responsible for the operation of Rakuten Mobile’s fully virtualized network. We manage critical infrastructure components for the Rakuten Core network, including IMS, RCS, EPC, International Roaming, IoT, and Emergency Services, alongside operational automation using AI.

Our mission is to ensure the continuity, reliability, and availability of these services. Our organization consists of 50+ highly skilled Technical SMEs, Operations Engineers, Project Managers, and Problem Managers. We operate a fully virtualized core network leveraging VNF & CNF architectures, supported by an advanced automation & AI framework.

5G SA Launch: With the launch of 5G SA services, we are initiating 5GC operations. Team Strengthening: We are strengthening our capabilities for operating virtualized core network elements. This is essential for ensuring the uninterrupted and reliable delivery of core services through specialized skills, automation, and AI.

Scaling Operations: Due to the growing complexity of core technology, the adoption of the latest innovations, an expanding customer base, and the migration to cloud architecture, we require additional resources to manage the increasing workload associated with maintaining virtualized core network elements. Job Duties Responsible for L2/L3 level troubleshooting support for 5GC E2E operations.

Provide support for vendor products, troubleshooting and resolving technical issues for Core & Cloud. Manage and resolve complex customer issues escalated from the monitoring support team. Perform in-depth audits and implement improvement plans. Perform regular technical analysis to ensure service optimization and quality.

Collaborate with internal teams, partners, and vendors to resolve escalated technical issues and implement corrective actions. Conduct testing and verification of any implemented configuration changes to ensure they meet regulatory and service requirements. Generate reports, analyze service/operational KPIs, and contribute to the improvement of processes and procedures.

Document and maintain detailed records of all support activities, including resolutions, troubleshooting steps, and partner interactions. Execute change implementations. Handle communications with other domains. Build knowledge and manage daily operational activities for high efficiency. Collaborate with partners and internal stakeholders to identify issues and fix incidents within the agreed service SLA.

Participate in an on-call shift rotation pool. Availability to work occasionally during nights and weekends to provide support for urgent issues or scheduled maintenance. Working from Tokyo office.

Minimum Qualifications

10+ years of experience in mobile core network operations/planning. Hands-on job experience with 5GC products. Hands-on job experience with multi-vendor Packet Core products. Hands-on job experience with container-based infrastructure (Kubernetes). Strong knowledge of automation and AI.

Preferred Qualifications

Deep understanding of mobile network protocols and technologies (e.g., Diameter, GTP, SIP, RTP, and IP-based protocols). Specialization in a specific domain, along with strong technical knowledge of E2E Virtual Core network architecture (IMS, EPC, RCS & CNF). Hands-on experience in CNF-based mobile networks. Experience with monitoring tools, performance analysis, 5G Core & Cloud deployment, and industry-standard KPI/metric analysis tools.

Working experience with OpenStack or Kubernetes. Expertise in Method of Procedure (MOP) preparation and validation, as well as configuration implementation. Experience leading Incident Bridges and preparing reports for senior management. Relevant technical certifications. Excellent analytical, problem-solving, communication, and documentation skills.

Languages: English (Overall - 3

• Advanced)