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.