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Senior Lead / Principal Architect – 4G/5G L3 Stack Software
Location: Delhi and Bangalore
Experience Level: 12+ years in 4G/5G L3/Control-Plane Software Development
Domain: Telecommunications, 3GPP LTE & 5G NR Layer 3 Protocols (RRC, NGAP, S1AP, X2AP, XnAP, F1AP, E1AP), Open RAN (O-RAN), vRAN
Role Overview
We are seeking an experienced
Senior Lead / Principal Architect – 4G/5G L3 Stack Software to design, architect, and deliver control-plane software and L3 protocols for LTE (eNodeB) and 5G NR (gNodeB) base stations. In this role, you will lead the architecture for radio resource management, signaling protocols, and inter-node interfaces across vRAN, O-RAN, and custom architectures. You will manage cross-layer platform integrations, drive large-scale product delivery programs, and lead root-cause defect investigations across complex multi-vendor cellular networks.
Roles & Responsibilities
- Architecture & Feature Design: Architect, design, and code higher-layer control-plane features and protocol interfaces, including RRC, S1AP, X2AP, NGAP, F1AP, E1AP, and XnAP for 4G LTE and 5G NR networks.
- Defect Resolution & Field Engineering: Investigate and close complex control-plane failures, including attach/registration failures, handover drops, security-mode failures, RRC resume issues, paging misses, Xn/F1/E1 mis-synchronization, and UE/vendor-specific IOT issues.
- Testing & Interoperability Campaigns: Work closely with verification, OAM, and Core Network teams to build call-flow validation models, stress testing scenarios, multi-vendor interoperability campaigns, and negative/failure-recovery tests.
- Team Leadership & Mentorship: Mentor and review high-performance L3 engineering teams toward delivery excellence and strong code quality.
- Program Management: Drive end-to-end 4G/5G L3 product development, field maintenance, and customer support programs across custom, vRAN, and O-RAN gNodeB/eNodeB deployments.
- Stakeholder Engagement: Communicate effectively with senior internal leadership, Core Network vendors, and external customer stakeholders.
Required Technical Expertise & Skill Sets1. 4G/5G L3 Procedures & Protocol Knowledge
- Core L3 Signaling Protocols: Extensive knowledge of RRC, S1AP, X2AP, NGAP, F1AP, E1AP, and XnAP.
- Key Call Flows & Procedures: Expertise in Attach/Registration, Handover (HO), RRC Connection Re-establishment, Carrier Aggregation (CA), EN-DC (E-UTRA-NR Dual Connectivity), and NR-DC.
- Resource & Mobility Management: In-depth knowledge of mobility control, measurement configuration/reporting, bearer/session signaling, security activation, RLF (Radio Link Failure) handling, cell reselection, paging, and idle/connected mode state transitions.
- Interface Dynamics: Clear understanding of control-plane signaling procedures and how local RRC procedures interact with Core Network entities (AMF, MME, SMF, SGW-C, PGW-C).
- Control Plane & Data Path Integration
- Data Path & Packet Forwarding: L3 data path expertise including GTP-U, DPDK, and VPP.
- Software Architecture: Expertise in Linux environments, Inter-Process Communication (IPC), multi-process/multi-threaded system design, memory pooling, timer/state management, and state machine design.
- Cloud Native & Virtualization: Knowledge of containerization (Docker, Kubernetes, Pods), Linux system performance tuning for virtualized DU/CU deployments on x86/ARM servers, DPDK, Hugepages, and SR-IOV.
- Hardware Acceleration: Understanding of SmartNIC/DPU-assisted data paths and FPGA/SoC-based hardware acceleration architectures.
- Debugging, Log Analysis & Field Tools
- Trace & Log Correlation: Experience in field issue analysis using RRC/NGAP/S1AP/F1AP/E1AP traces, Wireshark decodes, KPI dashboards, and log correlation between RAN and Core; ability to translate field defects into reproducible lab scenarios.
- Protocol Decoding & Standards Compliance: Proficiency in ASN.1 handling, state machine error recovery, and maintaining backward/forward compatibility across 3GPP releases.
- Testing Tools: Hands-on experience with UE trace tools (QCAT) and network testing tools including Viavi, IxLoad Wireless, IxNetwork, Spirent Landslide, and Wireshark.
- 3GPP Wireless Standards Compliance3GPP LTE / E-UTRAN Specifications:
- 36.300 / 36.401: Overall Description (Stage 2) and Architecture description
- 36.331: Radio Resource Control (RRC) protocol
- 36.410 – 36.414: S1 General Aspects, L1, Signaling Transport, S1AP, and Data Transport
- 36.420 – 36.425: X2 General Aspects, L1, Signaling Transport, X2AP, Data Transport, and User Plane Protocol
3GPP 5G NR / NG-RAN Specifications
- 38.300 / 38.401: NR & NG-RAN Overall description (Stage 2) and Architecture
- 38.331: NR Radio Resource Control (RRC) protocol
- 38.410 – 38.415: NG Interface (General aspects, Signaling transport, NGAP, Data transport, PDU session user plane protocol)
- 38.420 – 38.425: Xn Interface (General aspects, L1, Signaling transport, XnAP, Data transport, NR user plane protocol)
- 38.460 – 38.463: E1 Interface (General aspects, L1, Signaling transport, E1AP)
- 38.470 – 38.474: F1 Interface (General aspects, L1, Signaling transport, F1AP, Data transport)
Qualifications & Experience
- Experience: Minimum of 12 years of core 4G/5G L3 stack/control-plane software development experience.
- Program Leadership: Proven experience driving large-scale L3 software development programs and field sustenance.
- Education: Bachelor’s or Master’s degree in Computer Science, Telecommunications, Electronics & Communication Engineering, or a related technical discipline.
Skills: general,software,data,4g,protocol,ran,3gpp,rrc,architecture,data transport
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