NBIOT L2 Engineer

Job Summary


Key Responsibilities

• 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

Job Requirements

Must-have skills

• 3GPP LTE/NB-IoT Layer 2/3 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
• Multithreading and shared-memory design
• Timers, state machines, and protocol packet processing
• Debugging packet traces and protocol logs
• Understanding of LTE/NB-IoT bearer concepts: SRB/DRB, logical channels and transport channels
• UE context, cell context, and RB reconfiguration; connection establishment, mobility, and release procedures

Preferred experience

• NB-IoT or LTE eNodeB stack development
• Knowledge of 3GPP specs: MAC, RLC, PDCP, RRC, S1AP, X2AP
• ASN.1 / protocol encoders/decoders
• Security/encryption functions used in PDCP
• 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

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