Principal Software Engineer – 5G Core Networks

Prattwhitney; San Jose (CA); On-site; USD 118,000 - 225,000; Full time

Benefits offered by this job

Medical, dental, vision insurance

Three weeks of vacation

Generous 401(k) plan

Tuition reimbursement

Life insurance

Job summary

Applied Signal Technology (AST) seeks a Principal Software Engineer specializing in 5G core protocol development to join our onsite team in San Jose. You will work with leaders to drive product visions, elicit requirements, and develop advanced software for SIGINT applications.

You will design and implement Linux-based software using C++ and Python, build microservices, and validate protocols like NAS, PFCP, and HTTP/2. Security clearance and U.S. citizenship are required.

Qualifications

• Typically requires a STEM degree and a minimum of 8 years of relevant experience.
• Aggregate of 5 years software development experience in 3GPP network functions, interfaces and service-based interfaces.
• Developing protocols such as NAS, PFCP, GTP-U, and HTTP/2.
• Reverse engineering telecommunications protocols and troubleshooting distributed systems.
• Experience with Linux-based software systems using C++ and Python.
• Ability to obtain and maintain a TS/SCI security clearance and U.S. citizenship.

Responsibilities

• Collaborate with technical leaders to advance product visions and roadmaps and develop innovative software solutions.
• Gather requirements from customers and CONOPS to shape architecture and implementations.
• Perform technical research, document findings, and contribute to demonstrations; travel up to 15% for site support.

Skills

Linux C++

Python

Microservices

REST APIs

Network protocols

Education

STEM degree

Tools

Docker

Kubernetes

Go

Rust

OpenTelemetry

Job description

Date Posted: 2026-09-17 Country: United States of America Location: US-CA-SAN JOSE-826 ~ 200 Holger Way ~ BLDG 826 Position Role Type: Onsite U.S. Citizen, U.S. Person, or Immigration Status Requirements: The ability to obtain and maintain a U.S. government issued security clearance is required. U.S. citizenship is required, as only U.S. citizens are eligible for a security clearance Security Clearance Type: TS/SCI with Polygraph Security Clearance Status: Active and existing security clearance required after day 1 Raytheon Company Managed by Collins Aerospace At RTX, the world's largest aerospace and defense company, 185,000 great minds are united by purpose and inspired to make a difference solving the world’s most complex problems. With our three market leading businesses, world-class operations and investments in research and development, we offer capabilities and opportunity no one else can. Together, we push the boundaries of known science and find new ways to connect and protect our world. Collins Aerospace is a leader in technologically advanced, intelligent solutions that help redefine the aerospace and defense industry. With a comprehensive portfolio and deep technical expertise, we help customers meet the demands of the global market. Join us and help shape the future of aerospace and defense. Applied Signal Technology (AST) is seeking a Principal Software Engineer with specialization in protocol development within 5G Core Networks who strives for excellence and has a passion to be part of a team that strengthens our nation and improves the security of our world. AST provides trusted strategic and tactical SIGINT solutions that secure the interests of the U.S. and its partners. AST’s work in areas such as high-capacity broadband communications, signal processing and analysis, tactical SIGINT, and wireless communications continually challenge our extraordinary engineers to resolve problems and make the world a safer place. AST’s work environment is passionate, highly collaborative and provides engineers with the freedom to strengthen and expand their skills, explore new and creative ideas, and work closely with our nation’s finest service members all while embracing integrity, innovation, and work-life balance. This is an ONSITE position at the San Jose, CA location.

WHO WE ARE

What You Will Do

• Collaborating with technical leaders to further product visions and roadmaps and developing innovative software solutions
• Collaborating with customers to elicit requirements and CONOPS
• Performing technical research, developing technical documentation, presentations, and/or leading concept demonstrations. Travel up to 15% travel time to other AST sites and customer sites to support customers meetings and/or demonstrations, system deployments.

Qualifications You Must Have

• Typically requires a degree in Science, Technology, Engineering or Mathematics (STEM) and a minimum of 8 years of prior relevant experience
• Aggregate of 5 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), and/or Session Management Function (SMF), N4 and/or N11 network interfaces, and/or 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.

The salary range for this role is 118,300 USD - 224,900 USD.

The salary range provided is a good faith estimate representative of all experience levels. RTX considers several factors when extending an offer, including but not limited to, the role, function and associated responsibilities, a candidate’s work experience, location, education/training, and key skills.

Hired applicants may be eligible for benefits, including but not limited to, medical, dental, vision, life insurance, short-term disability, long-term disability, 401(k) match, flexible spending accounts, flexible work schedules, employee assistance program, Employee Scholar Program, parental leave, paid time off, and holidays. Specific benefits are dependent upon the specific business unit as well as whether or not the position is covered by a collective-bargaining agreement. Hired applicants may be eligible for annual short-term and/or long-term incentive compensation programs depending on the level of the position and whether or not it is covered by a collective-bargaining agreement. Payments under these annual programs are not guaranteed and are dependent upon a variety of factors including, but not limited to, individual performance, business unit performance, and/or the company’s performance.

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 Program
• Life 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!

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.

This role is a U.S.-based role. If the successful candidate resides in a U.S. territory, the appropriate pay structure and benefits will apply.

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 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.

Do you want to be a part of something bigger? A team whose impact stretches across the world, and even beyond? At Collins Aerospace, our Mission Systems team helps civilian, military and government customers complete their most complex missions — whatever and wherever they may be. Our customers depend on us for intelligent and secure communications, missionized systems for specialized aircraft and spacecraft and collaborative space solutions. By joining our team, you’ll have your own critical part to play in ensuring our customer succeeds today while anticipating their needs for tomorrow.

Are you up for the challenge? Join our mission today.

This position is classified as: Onsite: Employees who are working in Onsite roles will work primarily onsite. This includes all production and maintenance employees, as they are essential to the development of our products.