IMS / Core Test Engineer - 5G

IMS / Core Test Engineer - 5G

Location: Bristol 3x a week. 

About the Role

Qualitest is seeking an experienced IMS / Core Test Engineer to support the validation and testing of mobile network core and IMS services for a leading telecommunications client. The successful candidate will be responsible for ensuring the quality, performance, and reliability of voice, messaging, data, and next-generation communication services across complex telecom environments.

Working closely with network engineering, development, operations, and vendor teams, you will execute end-to-end testing activities across IMS, EPC/5GC, VoLTE, VoWiFi, and related network domains, supporting both new feature delivery and production assurance initiatives.

Key Responsibilities

• Design, develop, execute, and maintain test cases for IMS and Core Network platforms.
• Perform end-to-end testing of VoLTE, VoWiFi, SMS, MMS, data services, and supplementary services.
• Validate IMS call flows, SIP signalling, Diameter interfaces, and network interoperability.
• Execute functional, integration, regression, system, and user acceptance testing activities.
• Analyse network traces and logs to identify root causes of defects and performance issues.
• Support testing across EPC and 5G Core network elements including MME, HSS, PCRF, AMF, SMF, UDM, and PCF.
• Validate roaming, emergency calling, handover, and mobility management scenarios.
• Collaborate with vendors and internal stakeholders to investigate and resolve defects.
• Create detailed test reports, defect documentation, and release readiness assessments.
• Support automation initiatives where applicable to improve testing efficiency and coverage.
• Participate in release planning, risk assessment, and production deployment activities.

Required Skills & Experience

• Experience working within telecommunications testing environments.
• Strong understanding of IMS architecture and protocols.
• Hands-on experience testing VoLTE, VoWiFi, SIP, Diameter, RTP, and related technologies.
• Knowledge of EPC and/or 5G Core network components and interfaces.
• Experience using network analysis tools such as Wireshark, QXDM, or similar.
• Ability to analyse signalling traces and troubleshoot end-to-end service issues.
• Experience working with defect management and test management tools.
• Understanding of mobile network architecture including LTE and 5G technologies.
• Strong analytical, troubleshooting, and communication skills.