Senior Software Engineer - NR-NTN Protocols (L2 & L3)

Responsibilities

• Design, develop, and maintain C++ implementations of 5G NR-NTN L2 and L3 protocol stacks, including MAC, RLC, PDCP, and RRC.
• Implement NTN-specific L2 adaptations: extended HARQ timers, TA pre-compensation, coverage enhancement scheduling, and constellation-aware MAC resource management.
• Develop NTN-specific RRC enhancements: satellite ephemeris broadcast (SIB19/SIB31), UE assistance information for NTN, TA command extensions, and coverage enhancement configurations.
• Implement the RRC measurement framework: measurement configuration, gap scheduling, TN/NTN measurement event handling (A1-A6, NTN-specific events), and inter-RAT/inter-frequency reporting tailored to NTN link dynamics.
• Implement and maintain RRC connection control procedures : RRC Setup/Reconfiguration/Re-establishment, CHO (Conditional Handover), DAPS handover, and RRC Release with redirect.
• Collaborate with Core Network and MNO integration teams to validate NGAP procedures against AMF implementations in lab and live MNO environments.
• Perform debugging, root-cause analysis, and performance tuning of L2/L3 issues in Linux-based development and test environments.
• Collaborate with systems engineers to translate 3GPP Rel-17/18 NR-NTN specifications into software requirements and detailed L2/L3 designs.
• Participate in code reviews, architecture discussions, and contribute to technical documentation and design specifications.
• Actively use AI coding assistants (Claude, Cursor, Codex) throughout the development lifecycle - from spec interpretation and boilerplate generation to test automation and code review - and help establish team best practices for AI-augmented engineering.
• Sound Like You? What You Bring:
• 2+ years of hands-on software engineering experience in wireless/telecom protocol development, with specific depth in L2 and L3 protocol stacks.
• Master's or PhD degree in Wireless Communications, Electrical Engineering, Telecommunications, or a closely related field.
• Strong proficiency in C++ (C++14/17) with demonstrated experience writing production-grade embedded or near-real-time protocol software.
• Solid understanding of 5G NR Layer 2 protocols : MAC (scheduling, HARQ, random access), RLC (AM/UM/TM), and DL/UL scheduler design.
• Deep, implementation-level knowledge of RRC state machines, connection control, reconfiguration, measurement framework, and mobility procedures (handover, re-establishment, CHO, DAPS).
• Solid understanding of UE context lifecycle , handover signalling, paging, error handling, and AMF/gNB interactions over the N2 reference point.
• Experience with Linux kernel/user-space debugging tools: GDB, Valgrind, perf, tcpdump, Wireshark, and system log analysis.
• Proficiency in production-grade protocol software: state machine design, message parsing/encoding (ASN.1/PER), and multi-threaded protocol engines.
• Ability to read 3GPP specifications and independently derive software requirements and detailed designs

Benefits

Additional Information

The world still has coverage blind spots. You could help eliminate them at Skylo. Skylo has pioneered a standards-based approach to satellite connectivity. We connect smartphones and IoT devices directly to satellites. No special hardware, no entirely new networks. Just billions of existing devices, suddenly reachable anywhere on Earth. We're not building toward this future. We're already in it. Our direct-to-device service is live on millions of activated devices across five continents, covering more than 72 million square kilometers, in partnership with leading satellite operators, mobile network operators, Tier-1 chipset makers, and OEMs worldwide. And we're just getting started. At the heart of it all is Skylo's commercial NTN vRAN: a 3GPP standards-based, cloud-native platform that seamlessly bridges terrestrial and satellite networks. It's the infrastructure that makes true anywhere, anytime connectivity possible. When you join Skylo, you'll work at the intersection of three markets reshaping how the world stays connected: mass-market consumer devices, automotive, and industrial IoT. Enabling people outdoors and critical workflows in the world's most remote places. This is a rare chance to work on technology that matters, at a company that's already proving it works This role is based in Espoo, Finland, one of Skylo's core engineering hubs and fastest-growing sites. You'll work onsite three days a week as part of a team that's scaling quickly. How You Will Impact Skylo We are seeking a highly skilled Senior Software Engineer to join our Protocol Stack team, focused on the development and optimization of 5G New Radio Non-Terrestrial Network (NR-NTN) Layer 2 and Layer 3 protocol implementations. In this role, you will design, implement, and validate MAC/RLC/PDCP and RRC protocol software that runs on Skylo's NTN vRAN platform, working closely with our standards, systems, and integration teams to bring NR-NTN connectivity to market at scale.

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