5G Software Engineer (Remote Spain)

Cactus is a software development company, providing full-cycle services for the European market. More than 170 companies increased business productivity using solutions developed by CactusSoft programmers. The company has been regularly included in the listings of the best software development companies in Belgium and Europe.

We are looking for a 5G Software Engineer to support the definition and implementation of 5G Non-Terrestrial-Network capabilities based on space platforms.

As a 5G Software engineer, your role will be to take charge of the software design up to the validation of hardware on 5G solutions and participate in reaching Satcom products in the end, ensuring its compliance to 3GPP standards (Release 17 onwards) and 5G NTN communication system and all activities revolving around it.

This position is based in Spain, and you will collaborate with teams across Europe and an international partnership landscape.

What You Will Do

• Define and document requirements: translate high-level network and service requirements into detailed, actionable technical specifications for 5G features, considering NTN unique aspects.
• Ensure all implemented features align with relevant 3GPP standards (Release 17 onwards for NTN) and industry best practices.
• Design, develop, and optimize embedded software components for next-generation satellite modems.
• Implement efficient algorithms in C++/Python, working close to the hardware and ensuring real-time performance.
• Integrate software with FPGA, SDR, and networking layers in resource-constrained environments.
• Build and maintain test setups and validation frameworks to evaluate the performance, security, and robustness of software products.
• Perform automated testing, benchmarking, and monitoring under realistic operational conditions.
• Collaborate with system architects, hardware engineers, and researchers to bring advanced 5G NTN concepts into production-ready solutions.
• Work on the systems integration into the complete 5G NTN User Terminals, including parabolic satellite antennas or flat panel antennas.
• Participate in the 5G NTN system end-to-end design & definition.
• Link with partners for the equipment specifications.
• Contribute to system validation.
• Support demo operations and compare measured performances w.r.t. expected performances.

What We Expect

• Ability to interpret and apply technical specifications to requirements.
• Deep Understanding of 3GPP Standards (NR & NTN) : 5G system architecture, protocol layers PHY, MAC, RLC, PDCP, RRC, NAS; Integration with the 5G Core Network Initial Access and mobility: Random Access Procedure (RACH), Handover Measurement and reporting, Channel State Information (CSI), feedback reporting, UE conformance & Testing.
• Knowledge in NTN-specific features introduced in Release 17 and beyond (e.g., SIB19, timing advance for NTN, Doppler compensation, mobility in NTN).
• Experience in satellite telecommunication systems would be a plus.
• Experience with OpenAirInterface is a strong plus.
• Strong proficiency in programming languages such as C++ and/or Python, with proven experience in developing efficient, scalable software.
• Solid understanding of modern software architectures, including microservices and containerized environments (e.g., Docker, Kubernetes).
• Familiarity with CI/CD pipelines, version control (Git), and DevOps practices.
• Experience with monitoring, logging, and observability tools (e.g., Prometheus, Grafana, ELK, Datadog) to ensure high system reliability.
• Knowledge of cloud-native environments (Azure, AWS, or GCP) is a strong plus.
• Knowledge of IP stack and network protocols.
• Passion about technology.
• Power to take initiatives to propose simpler and efficient ways of working.
• Hands-on and solution-oriented attitude.
• Excellent English communication skills – written and spoken.
• Self-driven and proactive, not afraid to challenge the status quo.
• Autonomy, Adaptability, Availability, Accountability.

What We Offer

• Working with international clients.
• An environment to develop your professional capabilities and take ownership.
• Collaboration with a team of open, dynamic, and international experts.
• Full-time position with a competitive salary and benefits, including learning opportunities.
• Flexible working hours.
• Get-together team events.