NBIOT L2 Engineer

Overview

Plans, designs, develops and tests software systems for Layer 2/3 features of NB-IoT and LTE protocol stacks, using Waterfall or Agile methodologies.

What you'll do

• Design, implement, and debug Layer 2/3 control and data path features
• Maintain MAC scheduler behavior for UL/DL grant decisions and resource allocation
• Work on RLC and PDCP flows for segmentation, retransmission, reordering, and bearer management
• Implement and validate UE/CELL state transitions driven by RRC and S1AP/X2AP messages
• Troubleshoot protocol interoperability and real-world failure scenarios
• Optimize scheduler and bearer behavior for NB-IoT constraints such as coverage, latency, and power efficiency

What you'll need

• Strong understanding of 3GPP LTE/NB-IoT Layer 2 and Layer 3 protocols: MAC scheduling, HARQ, RACH, paging, logical channels, and UE state handling
• RLC modes and retransmission behavior
• PDCP sequence numbering, security, ROHC, and bearer management
• RRC setup/reconfiguration/release and UE control procedures
• S1AP/X2AP signaling and UE/cell context management
• Hands-on experience in C/C++ development for telecom or embedded networking stacks
• Familiarity with low-latency, real-time scheduling and event-driven protocol processing
• Experience with Linux/Unix environments
• Experience with multithreading and shared-memory design
• Experience with timers, state machines, and protocol packet processing
• Experience debugging packet traces and protocol logs
• Understanding of LTE/NB-IoT bearer concepts: SRB/DRB, logical channels and transport channels
• Understanding of UE context, cell context, and RB reconfiguration
• Understanding of connection establishment, mobility, and release procedures

Nice to have

• Experience with NB-IoT or LTE eNodeB stack development
• Knowledge of 3GPP specs: MAC, RLC, PDCP, RRC, S1AP, X2AP
• Familiarity with ASN.1 / protocol encoders/decoders
• Experience with security/encryption functions used in PDCP
• Exposure to scheduler optimization, throughput/latency tuning, and interference handling
• Ability to work with vendor stacks and trace tools such as Wireshark, logs, and internal UE/eNB diagnostics