Senior Software Engineer – NR-NTN Protocols (L1 & L2)

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 Skylo is 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 1 and Layer 2 protocol implementations. In this role, you will design, implement, and validate PHY, MAC, FAPI, and scheduler software that runs on Skylo's NTN vRAN platform, working closely with our RF, 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 L1/L2 protocol stacks — including PHY adaptation layer, FAPI interface, MAC, and DL/UL schedulers Implement NTN-specific L1 adaptations : extended HARQ round-trip timers, timing advance pre-compensation, NTN-aware link adaptation, and satellite Doppler pre-compensation at the PHY layer Extend and optimize the MAC scheduler for NTN: HARQ retransmission management, coverage enhancement (CE) mode scheduling, and constellation-aware resource allocation Design and implement the FAPI interface between MAC and PHY — P5/P7 message handling, slot indication processing, DL/UL configuration, and timing/error event management for NTN-adapted slot structures Develop DL/UL scheduler algorithms for NTN: HARQ retransmission scheduling, CE mode resource allocation, constellation-aware policies, and QoS-aware prioritization across satellite link conditions Work with RF and baseband teams to validate L1/L2 protocol behaviour across lab and field NTN environments (LEO/GEO) Debug, root-cause, and performance-tune L1/L2 issues in Linux-based environments using GDB, Valgrind, perf, and Wireshark Partner with systems engineers to translate 3GPP Rel-17/18 NR-NTN specifications into software requirements and detailed L1/L2 designs Participate in code reviews, architecture discussions, and contribute to technical documentation Actively use AI coding assistants (Claude, Cursor, Codex) across the development lifecycle — from spec interpretation and test automation to 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 L1 and L2 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. Deep understanding of 5G NR PHY layer : numerologies, slot/frame structure, PDSCH/PUSCH processing, HARQ operation, beamforming, and link adaptation. Solid understanding of 5G NR MAC layer : scheduling procedures, HARQ management, BSR/SR/PHR handling, random access procedures, and beam management. Strong understanding of FAPI (nFAPI or SCF FAPI) : P5 configuration interface, P7 real-time slot-level messaging, and MAC-PHY synchronisation in split L1/L2 architectures. Hands-on experience designing or optimising DL/UL schedulers : proportional fair, round-robin, QoS-aware, and near-real-time scheduling in production RAN software. Experience with Linux kernel/user-space debugging tools : GDB, Valgrind, perf, tcpdump, Wireshark, and system log analysis. Proficiency in production-grade protocol software development : state machine design, message parsing/encoding, and multi-threaded protocol engines. What We Offer This is a once-in-a-lifetime opportunity to help build and run the world's first commercial, live direct-to-device satellite network. You'll work alongside a world-class team spanning software, hardware, chipsets, telecom, satellite, and network virtualization, some of the most sought-after expertise in the industry. And you'll do it inside a culture that's open, transparent, and inclusive, shaped by the best of Silicon Valley, Nordic, and South Asian ways of working. With employees working across three continents, Skylo is proud to be an equal opportunity employer dedicated to building an inclusive and diverse workforce. Our worldwide and inclusive culture encourages a flexible approach to work, and we also offer an attractive range benefits such as: Competitive compensation packages Occupational Healthcare and Health and Life Insurance E-passi including, wellness, culture, lunch and commuting benefit Phone & Internet allowance Individual learning & development budget for further personal and professional development Ready To Join Us? Apply now and a member of our recruiting team will be in touch. We review applications on an ongoing basis, so we encourage you to apply early. Our process includes an initial call with a recruiter, a take-home assignment, and two interviews with different team members. Still have questions? Teea Kuusimurto, our Senior Recruiter, has answers. Say hello at [email protected]. EEO Statement Skylo is an equal-opportunity employer and we celebrate diversity. We do not discriminate on the basis of race, religion, color, ancestry, national origin, caste, sex, sexual orientation, parent or caregiver status, political affiliation, gender, gender identity or expression, age, disability, medical condition, pregnancy, genetic makeup, marital status, or military service consistent with applicable federal, state, and local laws. We are also committed to providing reasonable accommodations for qualified individuals with disabilities and disabled veterans in our job application procedures. Please let us know if you need assistance or accommodation due to a disability.