Principal Engineer – Core

Overview

Principal Engineer – Core is the technical authority for Skylo's core network and service layer, owning architecture, design, capacity planning and performance of the cloud-native 5G core, IMS voice and SMS services, and their integration with Skylo's NTN RAN.

What you'll do

• Own the end-to-end architecture and design of Skylo's 5G core (5GC) and its interworking with EPC, including AMF, SMF, UPF, AUSF/UDM/UDR, PCF, NRF, NSSF and NEF functions.
• Act as the lead technical counterpart to core network vendors, driving roadmap and feature requirements, design reviews, and release acceptance.
• Design and evolve IMS-based voice and messaging services (VoLTE/VoNR, SMS over NAS, SMS over IP, SMSC and IP-SM-GW interworking) for satellite-connected devices.
• Define how the core integrates with Skylo's NTN vRAN, including NTN-specific requirements such as extended timers, long round-trip delay, mobility, tracking area design, and satellite/terrestrial roaming.
• Lead core network capacity planning and dimensioning, including traffic forecasting, subscriber growth modelling, and resource planning across cloud and on-prem deployments.
• Define core network KPI frameworks, baselines, and thresholds, and drive performance analysis and optimisation of registration, session, voice, and SMS success rates.
• Design roaming and interconnect architectures with MNO partners (S6a/S8, N32/SEPP, Diameter and HTTP/2 signalling, DEA/DRA, SMS interworking).
• Partner with Regulatory, Security, and Operations teams to ensure the core supports Lawful Intercept, emergency services, and network security requirements.
• Create technical specifications, high- and low-level designs, and engineering documentation for core network elements.
• Conduct proof-of-solutions and lab validation to assess new features, vendors, and architecture options.
• Drive continuous improvement loops with Operations and Implementation teams, including root cause analysis of core network incidents.
• Mentor engineers and provide technical leadership across the Network Design and Planning team.

What you'll need

• 15+ years of experience in mobile core network engineering, design, or architecture, preferably within a mobile network operator or core network vendor.
• Deep hands-on experience with 5G Core (SA) and EPC, including the service-based architecture (SBA/SBI) and 3GPP core specifications (e.g. TS 23.501, 23.502, 23.401).
• Hands-on experience with IMS architecture (P/I/S-CSCF, TAS, HSS) and end-to-end call flows for SMS delivery, VoLTE, and VoNR.
• Strong understanding of NAS, NGAP/S1AP, GTP, PFCP, Diameter, SIP, and HTTP/2 protocols.
• Proven ability to perform core network traffic forecasting, capacity planning, and dimensioning.
• Demonstrated expertise in defining KPI frameworks, baselines, and thresholds, and in driving performance optimisation.
• Experience managing core network vendors, including leading technical design reviews and acceptance testing.
• Excellent understanding of inbound and outbound roaming architectures and interconnect.
• Hands-on experience with cloud-native network functions and cloud technologies such as Kubernetes, Docker, and public cloud (AWS, GCP).
• Excellent written and verbal communication skills for creating detailed technical documentation and presenting solutions to internal and partner audiences.
• Previous experience mentoring engineers or leading technical teams.

Nice to have

• Experience with Non-Terrestrial Networks (NTN) and 3GPP Rel-17+ NTN.
• Familiarity with Lawful Intercept, emergency services, and core network security.

Details

• Location: Bangalore, India.
• Work mode: onsite 3 days a week in office.