A Theoretical Investigation of Non-Orthogonal Multiple Access Schemes for Dense IoT Deployments in Nigerian Smart Cities

Fifth-generation and beyond-5G wireless networks serving dense IoT deployments in Nigerian smart city environments face a spectrum access bottleneck that orthogonal multiple access schemes cannot resolve at the device densities anticipated for city-wide sensor deployments, and the theoretical characterisation of non-orthogonal multiple access performance under Nigerian channel conditions has not been rigorously established. This study conducted an original theoretical investigation of power-domain and code-domain NOMA schemes for dense IoT smart city environments, developing a novel channel model validated against measurements in Nigerian urban radio environments. A channel sounding campaign was conducted in four locations: Lagos Island CBD, Abuja Phase 1, Kano Municipal, and Enugu GRA, measuring path loss exponents, shadowing statistics, and delay spread at 2.6 GHz and 3.5 GHz bands relevant to 5G IoT deployments. The measured data informed a novel Generalised Nigerian Urban Channel Model (GNUCM) with parameterised distributions that deviate from ITU-R UMa standard models, most significantly in shadowing standard deviation (measured mean 7.8 dB versus ITU-R 4 dB). Theoretical throughput analysis of power-domain NOMA and sparse code multiple access under the GNUCM demonstrated that SCMA provided 43.7 percent higher aggregate throughput than PDMA at 200 devices per km2. An original closed-form outage probability expression for PDMA under the GNUCM was derived, validated by Monte Carlo simulation with less than 2 percent relative error. The study constitutes an original theoretical contribution to NOMA channel modelling for Nigerian smart city environments and recommends NCC incorporate GNUCM into spectrum planning guidelines for 5G IoT licensing.