Voice Software Engineer (Lisbon based)

1GLOBAL · Lisbon, Portugal (Hybrid) · Full-time · Posted 2026-11-13

Workplace: hybrid

Department: Technology

Description

About Us

1GLOBAL is a technology-driven global mobile communications provider helping enterprises and consumer brands deliver seamless connectivity worldwide. Powered by a best-in-class telecom platform, proprietary eSIM technology, and its own mobile core network across 15 countries, 1GLOBAL operates as a fully regulated telecommunications provider in 43 countries.

Founded in 2022, 1GLOBAL has rapidly become one of Europe's fastest-growing telecom technology companies, connecting more than 80 million people and devices globally. Our customers include leading banks, multinational enterprises, global retailers, travel companies, payment service providers, and digital-first businesses.

Headquartered in the Netherlands, with R&D hubs in Lisbon, Berlin, and São Paulo, 1GLOBAL employs over 550 professionals across 16 countries. With annual revenues exceeding US$200 million and a strong track record of profitability, we continue to invest in innovation, infrastructure, and international expansion as we redefine the future of global mobile connectivity.

About the Team

As a member of the Network Engineering team within the Voice and Services functional area, you will be responsible for the design, development, testing and lifecycle management of voice and messaging services delivered through IMS and Telecom Application Server platforms. This includes proposing, analyzing and defining requirements for new and existing voice systems, and developing service logic using service creation frameworks such as Rhino (JAIN SLEE), Oracle Communications Application Server, or equivalent platforms.

You will define and support the technology evolution roadmap for the application server and voice service layer, and collaborate with other functional areas on cross-functional projects.

About the Role

Design, develop, test and deploy voice/IMS service logic on Telecom Application Server platforms (e.g., Rhino/JAIN SLEE, Oracle Communications Application Server, or equivalent service creation frameworks), using SIP, CAMEL and Diameter interfaces
Collaborate with other Networks teams to define and manage projects for the delivery of new voice and application server solutions
Own end-to-end project delivery: network design, integration and migration strategy, and collaboration with other relevant departments
Design new consumer and corporate voice/telecom solutions
Create and maintain technical documentation (HLDs, LLDs, Work Orders, etc.) throughout the solution lifecycle
Implement solutions in live environments and define end-to-end system testing requirements
Define and track Quality and Performance indicators
Perform capacity and performance analysis, reporting, and define improvement solutions
Define and implement service and resource configuration on relevant systems
Contribute to complex solutions that influence current product design and address design issues for future products/technologies
Maintain close working relationships with external partners (carriers, service providers)
Elaborate and manage the change request process with partners to meet network requirements
Own the network elements roadmap, including software/hardware upgrade planning across the component lifecycle
Drive process improvements, especially cross-team processes
Document the existing technology portfolio and propose recommendations for improvements or alternatives

Requirements

About You

Must Have

Proven experience implementing live solutions in mobile telecom networks (GSM, UMTS, LTE, IMS) – network design, capacity management, engineering and architecture
Knowledge of 3GPP, GSMA and ITU standards and specifications
Hands-on experience developing and deploying voice/IMS service logic on Telecom Application Server / Service Creation Environment (SCE) platforms – e.g., Rhino (JAIN SLEE), Oracle Communications Application Server (OCAS), or equivalent frameworks – using SIP and CAMEL interface protocols
Working knowledge of Java and JAIN SLEE (or an equivalent service-logic programming/execution model) for building, customizing and troubleshooting telecom service applications
Experience in IMS-based unified communications service development
Solid understanding of IMS architecture, including VoIP, VoLTE, VoWiFi and QoS
Experience with SMS service configuration and routing
Understanding of IMS nodes (P/S/I-CSCF, Application Servers) and IMS protocol interfaces – Gm, ISC, Sh, Cx, SOAP/XML, etc.
Experience with mobile services charging (offline/online), including OCS and Ro, Ro+, Ga and Bp interfaces
Knowledge and experience with Diameter/SCTP networks and protocols
Knowledge and experience with signaling gateways and protocols, including SS7, SIGTRAN, MAP and CAMEL
Experience with protocol analyzer tools (e.g., Wireshark, Astellia) to troubleshoot network issues across the above protocols
Experience with ETSI NFV architecture and solutions
Familiarity with MVNO/MVNE/MVNA architectures and landscape
English proficiency mandatory; additional languages a plus
Degree in Telecommunications Engineering, Computer Science, or equivalent experience

Nice to Have

3+ years designing and implementing mobile core networks in the telecoms industry
Hands-on experience with Rhino (JAIN SLEE) specifically, in addition to other IMS Application Server platforms (Oracle, Nokia TAS, Ribbon, or similar)
Experience with open-source SIP platforms such as Kamailio (SIP proxy/registrar/routing) and FreeSWITCH (softswitch/media server)

Benefits

Why 1GLOBAL?

Growth Opportunities: Advance your career in one of the fastest growing telecommunications companies, expanding over 50% year-on-year under the leadership of successful tech entrepreneurs.
Major Transaction Exposure: Be in the driver’s seat for transactions that will have an impact on the future telco industry.
Work with a Talented Team: From the Board and the Founders to the Senior Management Team, you will collaborate daily with the most capable and renowned external advisors and constantly being exposed to talented and driven individuals.
Dynamic Work Environment: Thrive in a collaborative, fast-paced workplace where innovation is encouraged, and every contribution counts.
Professional Development: Work alongside industry experts to enhance your skills and knowledge in a cutting-edge field.
International Experience: Gain opportunities to work in different 1GLOBAL offices around the world as you grow within the company.
Open Communication Culture: Join a team where your ideas are heard, and open dialogue is encouraged, fostering a supportive and transparent work environment.
Get Things Done Attitude: Be part of a results-driven team that values efficiency, creativity, and the drive to make a tangible impact in the industry.

1GLOBAL is an equal opportunity employer, we value your character as much as your talent. Diversity drives our innovation, and we offer a collaborative, dynamic, and international work environment. We are excited for you to join our mission to revolutionise connectivity globally.

Legal Notice

This job advert and its content are the property of 1GLOBAL and are protected by copyright and other intellectual property rights. Copying, reproducing, republishing or distributing this advert, in whole or in part, without 1GLOBAL’s prior written consent is prohibited. 1GLOBAL reserves all rights and may take appropriate action against any unauthorised use.

Legitimate 1GLOBAL vacancies only redirect candidates to its official application channels, including LinkedIn and Workable, and 1GLOBAL never charges fees or request payments as part of our recruitment process. If you are unsure whether a vacancy is genuine, please refer to 1GLOBAL careers page at https://www.1global.com/vacancies‌ or contact [email protected].

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1GLOBAL

Voice Software Engineer

About the Job

Requirements

Responsibilities

Desired Qualifications