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

Skylo; Espoo; On-site; EUR 60,000 - 80,000; Full time

Benefits offered by this job

Occupational Healthcare

Health and Life Insurance

Phone & Internet allowance

E-pass for wellness and commuting

Individual development budget

Job summary

Skylo is seeking a highly skilled Senior Software Engineer in Espoo, Finland to join our Protocol Stack team. This role focuses on developing and optimizing 5G New Radio Non‑Terrestrial Network protocol implementations.

You will design, implement, and validate software for Skylo’s NTN vRAN platform, collaborating closely with RF and integration teams. The ideal candidate has strong C++ skills, experience in L1/L2 protocol development, and a master's or PhD in Wireless Communications or related fields.

We offer competitive compensation and benefits, including healthcare and individual development budgets.

Qualifications

• 2+ years in wireless/telecom protocol development with L1 and L2 stacks.
• Strong proficiency in C++ (C++14/17) for near-real-time protocol software.
• Experience designing or optimizing DL/UL schedulers.

Responsibilities

• Develop and maintain C++ implementations of 5G NR‑NTN L1/L2 stacks.
• Implement NTN‑specific L1 adaptations and optimize MAC scheduler.
• Validate L1/L2 protocol behaviour across lab and field environments.

Skills

C++

5G NR PHY layer knowledge

5G NR MAC layer knowledge

L1/L2 protocol development

Linux debugging tools

Education

Master’s or PhD in Wireless Communications or related field

Tools

GDB

Wireshark

Valgrind

Job description

Skylo

The world still has coverage blind spots. You could help eliminate them at Skylo. Skylo has pioneered a standards-based approach to satellite connectivity, connecting smartphones and IoT devices directly to satellites without special hardware or new networks. Our direct‑to‑device service is live on millions of activated devices across five continents, covering more than 72 million square kilometers. Skylo’s commercial NTN vRAN, a 3GPP standards‑based cloud‑native platform, seamlessly bridges terrestrial and satellite networks, enabling true anywhere, anytime connectivity.

Position Overview

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.

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, establishing team best practices for AI‑augmented engineering.

Qualifications

• 2+ years of hands‑on software engineering experience in wireless/telecom protocol development, with 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 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.

Benefits

• 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.

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.