Senior Principal Software Engineer – 5G Core Networks

Prattwhitney; San Jose (CA); On-site; USD 146,000 - 277,000; Full time

Benefits offered by this job

Medical, dental, and vision insurance

Three weeks of vacation

401(k) plan with employer matching

Tuition reimbursement

Job summary

Applied Signal Technology in San Jose seeks a Senior Principal Software Engineer for 5G Core network protocol development. You will develop core network software, collaborate on product roadmaps, and elicit customer requirements to shape solutions.

Role requires Linux/C++/Python expertise, 10+ years experience, and a TS/SCI security clearance with polygraph. Travel up to 15% to AST sites and customer locations is expected.

Qualifications

• Degree in STEM and 10+ years of experience in relevant work.
• Experience with 3GPP network functions or service-based interfaces.
• Proficient in Linux-based software development with C++/Python.
• Ability to obtain TS/SCI with polygraph and U.S. citizenship.

Responsibilities

• Develop 5G Core network software for next-gen processing solutions.
• Collaborate with leaders to refine product visions and roadmaps.
• Gather requirements from customers and document CONOPS.
• Create technical docs and demonstrations; travel up to 15%.

Skills

5G Core Network

C++

Python

Linux

REST-like APIs

Education

Bachelor's degree in STEM

Tools

OpenTelemetry

Prometheus

Grafana

Docker

VMware

KVM

Job description

Date Posted: 2026-09-17

Location: US-CA-SAN JOSE-826 ~ 200 Holger Way ~ BLDG 826

Contract Type: Onsite

Security Clearance: TS/SCI with Polygraph (Active, existing required after day 1)

U.S. Citizenship: required (U.S. citizen)

Position: Senior Principal Software Engineer – 5G Core Network protocol development

Employer: Applied Signal Technology (AST), a subsidiary of Collins Aerospace, RTX.

Introduction

Applied Signal Technology is a leader in strategic and tactical SIGINT solutions, providing high‑capacity broadband communications, signal processing, tactical SIGINT, and wireless communications solutions.

What You Will Do

• Apply your 5G Core Network software development experience to advance our next generation mobile telecommunication processing solutions.
• Collaborate with technical leaders to further product visions and roadmaps and develop innovative software solutions.
• Collaborate with customers to elicit requirements and CONOPS, and perform technical research.
• Develop technical documentation, presentations, and/or lead concept demonstrations.
• Travel up to 15% to other AST sites and customer sites to support meetings and/or demonstrations and system deployments.

Qualifications – You Must Have

• Typically requires a degree in Science, Technology, Engineering or Mathematics (STEM) and a minimum of 10 years of prior relevant experience.
• Aggregate of 7 years software development experience in one or more of the following areas: Developing 3GPP network functions, network interfaces, and/or service-based interfaces, such as User Plane Function (UPF), Access and Mobility Management Function (AMF), Session Management Function (SMF), N4 and/or N11 network interfaces, Namf, Nsmf, and/or Nupf services.
• Developing protocols such as NAS, PFCP, GTP‑U, and/or HTTP/2.
• Reverse engineering telecommunications protocols.
• Troubleshooting distributed systems and control‑plane signaling paths.
• Using 5G core network control‑plane probes.
• Developing service‑based microservices with REST‑like APIs.
• Demonstrated expertise developing Linux‑based software systems utilizing modern C++, Python, or equivalent environments to architect, implement, and validate complex telecommunications processing solutions.
• Ability to obtain and maintain a U.S. government issued Top Secret SCI (TS/SCI) security clearance with polygraph after start.
• U.S. citizenship is required, as only U.S. citizens are eligible for a security clearance.

Qualifications – We Prefer

• Existing U.S. government issued TS/SCI security clearance with polygraph or current SSBI.
• Knowledge of AMF, SMF, UPF, UDM, PCF, AUSF, NRF behavior, interactions, and call flows.
• Experience developing 5G core network control‑plane probes for monitoring network traffic, extracting signaling and user‑plane information, decoding 3GPP protocols, and/or traffic replay.
• Experience with observability frameworks (OpenTelemetry, Prometheus, Grafana).
• Familiarity with 4G EPC (MME, SGW, PGW, HSS).
• Familiarity with network virtualization and/or containerization technologies (KVM, VMware, OpenStack, AWS, Kubernetes, Helm, Docker).
• Experience developing with Go or Rust.

What We Offer

• Medical, dental, and vision insurance
• Three weeks of vacation for newly hired employees
• Generous 401(k) plan that includes employer matching funds and separate employer retirement contribution, including a Lifetime Income Strategy option
• Tuition reimbursement program
• Student Loan Repayment ProgramLife insurance and disability coverage
• Optional coverages you can buy pet insurance, home and auto insurance, additional life and accident insurance, critical illness insurance, group legal, ID theft protection
• Birth, adoption, parental leave benefits
• Ovia Health, fertility, and family planning
• Adoption Assistance
• Autism Benefit
• Employee Assistance Plan, including up to 10 free counseling sessions
• Healthy You Incentives, wellness rewards program
• Doctor on Demand, virtual doctor visits
• Bright Horizons, child and elder care services
• Teladoc Medical Experts, second opinion program
• Eligible for relocation
• And More!

Salary

Salary range for this role is 145,600 USD - 276,800 USD. The salary range provided is a good faith estimate representative of all experience levels.

Additional Information

RTX anticipates the application window closing approximately 40 days from the date the notice was posted. However, factors such as candidate flow and business necessity may require RTX to shorten or extend the application window.

RTX is an Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, sex, sexual orientation, gender identity, national origin, age, disability or veteran status, or any other applicable state or federal protected class. RTX provides affirmative action in employment for qualified Individuals with a Disability and Protected Veterans in compliance with Section 503 of the Rehabilitation Act and the Vietnam Era Veterans’ Readjustment Assistance Act.

About RTX

RTX is an aerospace and defense company that provides advanced systems and services for commercial, military and government customers worldwide. It comprises three industry‑leading businesses – Collins Aerospace, Pratt&Whitney, and Raytheon. Its 195,000 employees enable the company to operate at the edge of known science as they imagine and deliver solutions that push the boundaries in quantum physics, electric propulsion, directed energy, hypersonics, avionics and cybersecurity. The company, formed in 2020 through the combination of Raytheon Company and the United Technologies Corporation aerospace businesses, is headquartered in Arlington, Virginia.