Core Network Engineer (IMS)

Company: Limitless Mobile
Location: Richardson
Posted on: April 2, 2026

Job Description:

Position: Core Network Engineer (IMS) Location: Richardson, Texas Reporting to: Director of Engineering Role: Core Network Engineer - IMS (VoLTE / VoNR) works within the Engineering department, responsible for Limitless Mobile's IMS infrastructure as well as deploying, managing, and supporting solutions for wholesale customers. Tasks/Responsibilities: Core Network Management The Core Network Engineer (IMS) is responsible for the operational integrity, performance, and evolution of Limitless Mobile's IMS voice services, including VoLTE and VoNR. The role focuses on the day-to-day operation, troubleshooting and optimization of the IMS platforms and interconnections . Operational ownership of IMS infrastructure components, including lifecycle management, configuration, software upgrades, vendor coordination, capacity planning, and fault resolution. Operational ownership of IMS interconnections, including SIP and SIP-I connectivity to PSTN, IPX providers, roaming partners, and emergency services (E911 etc). Responsibilities include SBC configuration, routing policies, codec negotiation, security controls, and interconnect testing. Act as the technical escalation point and subject matter expert for IMS voice services, including VoLTE and VoNR call flows, SIP signalling, RTP media handling, using the open source 5G (NSA / SA) core platforms. Support Roaming and Wholesale teams in the implementation of new roaming agreements, with particular focus on VoLTE and VoNR roaming, including configuration support, IREG testing, and fault resolution during commercial launch of service. Projects Work with Solution Architects to turn solutions designed for wholesale customers into High Level Design (HLD) documentation. When assigned, take ownership of solution deployment for contracted wholesale customers. Participate in post-mortem meetings after each project completion to identify learnings that can be applied in future projects. Operations Support the Network Operations Centre (NOC) with live wholesale and retail customer support, including both proactive and reactive identification / troubleshooting and resolution of issues. Participate in incident response, root cause analysis (RCA), and post-incident reviews for IMS voice services. Support planned maintenance, change management, and software upgrades with appropriate risk mitigation and rollback procedures. Participate in emergency call rotation for critical issues. Skills Development Continuously develop expertise across IMS, VoLTE, VoNR, and emerging voice technologies, including 5G SA voice evolution and roaming capabilities. Measurement: Performance will be measured using a combination of service availability, mean time to resolution (MTTR), successful deployment and launch of IMS voice services, reduction in repeat incidents, and quality of technical documentation and handover. Desired Expertise & Experience: Bachelors or Master's degree in Engineering, Computer Science, or related field. Minimum of 5-8 years working in the telecommunications industry designing, integrating, and managing mobile IMS networks and interconnections for wireless carrier / MNO, MVNO, etc. In-depth knowledge of the IMS network elements, interfaces, protocols, and call flows. Expert knowledge of Voice SIP / RTP and voice convergence technologies, IMS applications (including VoLTE and VoNR), voice traffic (home network, roaming, PSTN, etc.) Ability to design and configure mobile data networks. General understanding of Circuit Switched communications protocols such as SS7 (including SCCP, TCAP, MAP, CAMEL, etc.), SIGTRAN, etc. Diameter Signalling, DRA & RADIUS. Demonstrable experience of managing & configuring IMS network elements including SBG, BGF, MTAS, CSCF, etc. Experience with Ericsson products is a plus. Previous experience in management of the Ericsson MPBN is a plus. Good understanding of DNS, including configuration and troubleshooting. General understanding of Packet Switched communications protocols. APN Management. In-depth understanding of 3GPP, ITU-T and ANSI standards. Understanding of roaming agreements and IR.21, including IREG testing, a plus. IP networking, including IPv4 and IPv6, VPN IPSec and Point-to-Point, transport layer protocols, etc., preferably with CCNA certification. Trouble shooting and fault detection. Proactive and preventative maintenance. Experience of capacity management and dimensioning. Understanding Lawful Intercept & CALEA requirements in the PS domain is a plus. Successful track record of designing compelling technical solutions based on commercial needs of customers. Desired Personality: Entrepreneurial and proactive self-starter with a hunger to make a difference as well as strong performance and results orientation. Ability to thrive in a fast-paced start-up environment, managing multiple projects and deadlines in parallel with ability to recognize and adjust priorities as required. Detail-oriented, methodical, and well organised yet able to demonstrate a high degree of flexibility and adaptability. Ability to work effectively both independently as well as in a team. Ability to remain calm and methodical during major incidents and service outages. Strong analytical, problem solving and negotiation skills. Excellent skills in building and managing relationships as well as influencing. Excellent communications and presentation skills. Positive and constructive personality, including willingness to go beyond the call-of-duty to ensure successful and on-time delivery of the project. Residence Requirement: Candidate must be authorized to work in the USA.

Keywords: Limitless Mobile, Frisco , Core Network Engineer (IMS), Engineering , Richardson, Texas