A Theoretical Framework for Multi-Layer Network Resilience Optimization in Nigerian National Telecommunications Infrastructure Under Disaster Scenarios

National telecommunications infrastructure resilience against disaster scenarios ranging from flooding in the Niger Delta to conflict disruptions in the North East requires a theoretically grounded multi-layer network resilience optimization framework that addresses the interdependent physical, logical, and service layers of modern telecommunications systems. This doctoral study develops an original theoretical framework for multi-layer network resilience optimization in Nigerian national telecommunications infrastructure, providing analytical tools for disaster scenario impact assessment and resilience investment prioritization. The framework models the interdependencies between the physical infrastructure layer, IP routing layer, and service delivery layer of the Nigerian telecommunications network using a coupled multilayer network formulation. Original metrics for multi-layer resilience quantifying both service availability and geographic coverage retention under parameterized disaster scenarios are defined and their mathematical properties characterized. A disaster scenario library representing historically documented disruption events from NCC infrastructure impact records for the 2019 to 2024 period is constructed and used to parameterize stochastic failure models. An optimization model for resilience investment allocation across infrastructure hardening, redundancy, and recovery capability enhancement is formulated as a two-stage stochastic programming problem and solved using decomposition algorithms. Numerical experiments using the Nigerian national backbone network topology demonstrate that optimally allocated resilience investment of 3% of annual capital expenditure reduces expected service outage duration under the calibrated disaster scenario distribution by 47%. The doctoral framework constitutes an original contribution to telecommunications network resilience theory with direct application to Nigerian national infrastructure planning. Keywords: network resilience, disaster recovery, multi-layer network, stochastic optimization, Nigeria.