| Cellular communication systems have transformed from systems deployed by a single mobile network operator while utilizing a single Radio Access Technology (RAT) to multi--RAT, multi--operator systems. However, the inadequate application of the fundamental design principles of classical cellular communication systems when deploying contemporary cellular communication systems leads to large system deployment costs, high system complexity, limited system scalability and suboptimal utilization of system resources. Refined system design principles for contemporary cellular communication systems are developed and presented in this thesis to circumvent the inefficiencies introduced by currently employed system design principles, with emphasis on practical system configurations and deployment scenarios. The proposed enhanced system design principles substantially improve the performance of contemporary data cellular communication systems by exploiting system multiuser diversity and maximizing the utilization of radiofrequency resources.;After establishing the foundation for contemporary cellular communication systems, attention is shifted towards multi--operator systems, in which multiple mobile network operators share network infrastructure elements to reduce system deployment costs. The feasibility of spectrum pooling in multi--operator systems is thoroughly studied to determine the gains and limitations of joint resource allocation under spectrum pooling, with spectrum pooling verified to maximize the overall performance of multi--operator systems. Multi--RAT systems, in which multiple RATs are co--deployed to accommodate varying user equipment capabilities, are then considered, with emphasis on enhancing inefficient system structuring and operation, user access and spectrum management. Similar to multi--operator systems, joint resource allocation with autonomous spectrum assignment at system access points is verified to maximize the performance of multi--RAT systems. Finally, this thesis addresses irregular system deployment scenarios subject to limited multiuser diversity. Specifically, small cell access point performance is enhanced using a system--aided dynamic spectrum access framework designed to enable full spectrum utilization at all system cells. |