Prepared the technical design and cost estimation documentation for the modernization of the Public Switched Telephone Network (PSTN) of PJSC ‘Ukrtelecom’ under Project B6. The scope included network analysis at local, zonal, interzonal, and national transit levels; traffic forecasting; development of modernization options with maximum reuse of existing switching resources; integration of a national-level packet switch and regional multimedia gateways; organization of special service nodes; and leveraging existing data transmission and synchronization systems. Deliverables covered technical-economic indicators, reuse options for decommissioned switching equipment, digital channel calculations, network topology and routing schemes (including SS7 with STPs), VoIP logical and physical designs, IP addressing plans, synchronization schemes, and network redundancy concepts. The project also included measures for technical information protection, compliance with safety and fire protection requirements, and environmental impact assessment.