Flint is looking for a Transmission Engineer for a contracting opportunity with one of the main telco providers in the UK. Key Responsibilities Own and manage the complete E2E performance life cycle across RAN, IP transport/backhaul, and EPC/5GC domains. Develop and maintain performance baselines, KPIs/KQIs, and SLAs across all network layers. Lead complex multi-domain root cause analyses using cross-stack performance indicators and diverse data sources (RAN OSS, crowd-sourced data, transmission, transport, and core network elements). Identify root causes of underperforming KPIs and define corrective measures to improve network performance. Investigate systematic and mission-critical issues affecting service performance. Deliver detailed E2E performance reports with clear recommendations and action plans. Analyse end-to-end signalling flows (S1/X2/NG, GTP-C/U, SIP/IMS, PFCP). Monitor and optimise EPC/5GC KPIs, including registration/attach success, bearer/session setup, VoLTE/VoNR call quality, and handover success. Assess and troubleshoot backhaul performance issues related to latency, jitter, congestion, and packet loss. Collaborate with IP/Transport teams to evaluate routing, QoS, traffic engineering, synchronisation (PTP, SyncE), and network resiliency. Identify bottlenecks across microwave, fibre backhaul, and aggregation networks. Coordinate with Core Engineering teams on capacity planning, feature enablement, and software upgrades. Work cross-