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

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

Skylo Technologies

Espoo, Finland

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.

What You’ll Do

• 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