Mobile Voice Core Engineer

Our Client are a leading communications brand with an outstanding reputation for customer service and value commitment. An opportunity has now arisen within their team for an experienced Mobile Voice Core Engineer.

• Ensure the reliable operation, maintenance, and evolution of the Mobile Core network, including CS, EPC, IMS, and associated platforms
• Deliver high availability and performance for Packet Switched (PS) and Circuit Switched (CS) services, supporting technologies such as VoLTE, and 5G Core
• Act as a subject matter expert for IMS-based services (SIP, Cloud Voice, FTTH voice, Microsoft Teams Operator Connect), providing technical support for integration, troubleshooting, and optimization
• Operate and maintain IMS, CS and EPC components, ensuring compliance with KPIs and SLAs
• Monitor, perform configuration, upgrades, and patches for Mobile core network elements (MME, SGW, PGW, PCRF, HSS, HLR, SBC, CS Core and IMS nodes) working with Ericsson and other in‑house engineers
• Monitor and analyse performance metrics to optimise capacity and quality of service
• Troubleshoot complex issues across signalling protocols (Diameter, SIP, SS7, HTTPs) and resolve faults promptly
• Manage IMS platforms and SIP-based services for mobile and fixed voice
• Support Cloud Voice and FTTH voice solutions, ensuring seamless integration with IMS
• Implement and maintain Microsoft Teams Operator Connect and related interworking functions
• Ensure QoS and security compliance for all IMS-based services
• Support roaming services and ensure IREG compliance
• Maintain mobile support services such as SMS antifraud, voicemail, and SIM steering
• Support the deployment of new SIP carrier interconnects and ongoing support, routing and troubleshooting of existing interconnects
• Work with the Security Architect to (a) review assets, identify weaknesses and ensure appropriate security is maintained; (b) to ensure the Security strategy is implemented including the integration from within your domain with the company's security technology and tools
• Investigate security alerts and provide incident response within your domain
• If/When potential weaknesses, attacks, intrusions, unusual, unauthorised or illegal activity are identified, assist in the implementation of mitigations, including vulnerability management

• Strong understanding of 2G, 4G and 5G mobile networking and associated core
• Strong understanding of protocols utilised in a mobile network including but not limited to SIP, Diameter and SS7
• Experience with mobile core nodes (MME, SGW, PGW, PCRF, HSS) and IMS components (SBC S‑CSCF, I‑CSCF, BGCF etc)
• Knowledge of IP networks, routers, switches, dynamic routing protocols and an appreciation of system security
• An understanding and skills to configure and administer a telecoms virtualised and containerised environment
• Good communication skills both written and verbal
• Willingness to work and communicate with both internal cross departmental teams as well as external customers
• Flexible approach to work and participation in a call‑out rota
• Desire to learn new technologies through both formal and self‑learning and ability to adapt to an ever‑changing technical environment