Developing an Original Theoretical Model for Cognitive Radio Spectrum Management in Nigerian Licensed and Unlicensed Bands

Spectrum scarcity in Nigeria's rapidly growing mobile broadband market is exacerbated by inefficient static spectrum allocation, while large portions of licensed spectrum remain underutilised at any given moment, creating the theoretical conditions for cognitive radio dynamic spectrum access, whose performance under Nigerian regulatory and propagation conditions requires original theoretical modelling. This study developed an original theoretical model for cognitive radio spectrum management in Nigerian licensed and unlicensed frequency bands. The model development incorporated three novel contributions. First, a Spectrum Occupancy Characterisation Study was conducted through real-time spectrum sensing measurements using a software-defined radio (USRP N210) at four cities: Lagos, Abuja, Kano, and Enugu, measuring occupancy across 700 MHz to 5 GHz over a combined 2,400 hours of observation. Results confirmed average occupancy rates of 23.4 to 41.7 percent across measured bands, validating dynamic spectrum access potential. Second, an original Primary User Activity Model was derived as a semi-Markov process with Nigerian-specific state transition distributions fitted to the occupancy measurement data, providing more accurate PU modelling than standard Poisson processes used in the literature. Third, an original Secondary User Throughput Maximisation Framework was derived under interference constraints, using convex optimisation and the developed PU model to compute closed-form expressions for optimal sensing duration and transmission power allocation that maximise cognitive radio throughput without causing harmful interference to primary users. The framework showed 31.4 percent throughput improvement over state-of-the-art sensing algorithms in simulation using the measured PU model. Expert review confirmed the framework's original theoretical contributions.