5G Core System Engineering Lead

We are looking for a 5G Core System Engineering Lead to own end-to-end system design and interface definition for E-Space's satellite 5G Core network. This role sits at the architecture level: you will decompose requirements across the full core service chain, define interfaces and information flows at every boundary, and drive the trade-offs that are unique to a satellite operator - session continuity across dynamic links, SIM management, OSS/BSS, charging and policy, and subscription management for a globally mobile user base. You will translate those trade-offs into concrete architectural decisions and drive them to closure across software, platform, and back-end engineering teams.

What you will do:

• Own end-to-end 5G Core system architecture across the full service chain - AMF, SMF, UPF, UDM, PCF, AUSF, CHF, NEF - and produce architecture decision records (ADRs), system decomposition documents, and interface specifications that serve as the engineering source of truth.
• Define and own interface specifications at every core domain boundary: interfaces between network functions, Nx reference points, UPF-to-data-network anchoring, and integrations with back-end platforms including charging, billing, and SIM provisioning.
• Drive system-level trade-off analyses across competing constraints, latency-aware timer and retransmission parameter tuning, and complexity vs. flexibility trade-offs in policy and charging architecture.
• Analyse how satellite-imposed constraints propagate into core design decisions.
• Lead call-flow design for key 5G Core procedures in the satellite context.
• Define requirements and interface contracts for back-end platform integration: CDR generation and CHF interface, SIM provisioning and UDM data model, BSS/OSS integration points.
• Evaluate build-vs-buy options for core network functions and platform components; produce structured trade studies with quantified criteria covering performance, standards conformance, operational complexity, and cost.
• Define system-level acceptance criteria and performance benchmarks - session setup latency, registration success rate, charging accuracy, failover recovery time - and coordinate with the integration lab team to ensure test coverage matches architecture scope.
• Maintain alignment with 3GPP Rel-17/18 core specifications (SA2, SA5, CT4); identify where standard assumptions diverge from satellite operational constraints and drive resolution.

What you bring to this role:

• Bachelor's or Master's degree in Electrical Engineering, Computer Science, or a related field.
• 12+ years in system or network engineering, with deep focus on 5G SA Core or LTE EPC architecture.
• Strong command of 3GPP 5G Core architecture: NAS protocols, SBI service interfaces, N-reference points, and session, policy, and charging management across AMF, SMF, UPF, UDM, PCF, AUSF, and CHF.
• Demonstrated experience authoring interface specifications, system requirement documents, and trade study reports in a multi-team engineering environment.
• Understanding of how network-layer constraints propagate into core protocol behaviour and how to address them through parameter tuning or architectural adaptation.
• Experience with charging and policy architecture.
• Proven ability to drive architecture decisions to closure across software, platform, and back-end engineering teams.
• Strong written communication; able to produce precise interface specifications and trade-off analyses that stand on their own.

Bonus points for the following:

• Experience with 3GPP NTN core adaptations (Rel-17/18): satellite access node (SAN) architecture, timer and window parameter adaptation for high-latency links, or UPF placement in non-terrestrial topologies.
• Background in MVNO core architecture: roaming interfaces (N32/SEPP, Diameter S6a/S9), multi-PLMN federation, MVNO interconnect, or eSIM/SM-DP+ integration.
• Familiarity with 3GPP SA2/CT4 specifications or direct standards contribution experience.
• Experience with NEF or network exposure APIs and B2B API gateway architecture.
• Background in SIM provisioning platforms, subscription management, or UDM/HSS data modelling.
• Experience in a startup or fast-paced R&D environment where architectural decisions move at product speed.

Additional Requirements

This is a fast-paced, high-impact environment - flexibility to occasionally work extended hours or weekends during critical periods is expected.