Evaluation of IP Multimedia Subsystem Deployment for Enhanced Telecommunications Services at Airtel Nigeria

The IP Multimedia Subsystem architecture provides a service delivery platform for converged voice, video, and data services over packet-switched networks, enabling telecommunications operators to offer rich communication services that compete with over-the-top application providers. This study evaluates the IMS deployment strategy, implementation status, and service delivery outcomes at Airtel Nigeria, with particular attention to Voice over LTE service commercialization and its impact on voice quality and spectrum efficiency. A professional organizational assessment methodology combining structured technical interviews with sixteen network architecture engineers and product development managers, review of IMS deployment and VoLTE rollout documentation, and analysis of VoLTE call quality measurement data from Airtel's Lagos and Abuja operational zones was employed. Results indicate that Airtel's IMS core deployment is complete in major metropolitan areas but IMS coverage extends to only 34% of its LTE network footprint, limiting VoLTE availability for a significant portion of 4G subscribers. VoLTE mean opinion scores in fully deployed zones averaged 4.2, representing a substantial improvement over the 3.1 MOS recorded for circuit-switched voice fallback. Spectrum efficiency gains from VoLTE adoption were estimated at 1.8 times the efficiency of comparable circuit-switched voice traffic. IMS integration with legacy 2G and 3G networks for seamless handover during VoLTE calls was identified as a technical gap affecting call continuity. Recommendations include acceleration of IMS overlay to the full LTE footprint, optimization of single radio voice call continuity handover parameters, and active subscriber migration campaigns to VoLTE-capable handsets. Keywords: IMS deployment, VoLTE, Airtel Nigeria, voice quality, LTE network.