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The 3rd Generation Partnership Project (3GPP) submitted the 5G New Radio (NR) system specifications to International Telecommunication Union (ITU) as a candidate fifth generation (5G) mobile communication system (formally denoted as IMT-2020 systems). As part of the submission, 3GPP provided a self-evaluation for the compliance of 5G NR systems with the ITU defined IMT-2020 performance requirements. This paper considers the defined 5G use case families, Ultra Reliable Low-Latency Communication (URLLC), massive Machine Type Communication (mMTC) and enhanced Mobile Broadband (eMBB), and provides an independent evaluation of the compliance of the 3GPP 5G NR selfevaluation simulations with the IMT-2020 performance requirements for connection density, reliability, and spectral efficiency for future mobile broadband and emerging IoT applications. Independent evaluation indeed shows the compliance of the 3GPP 5G NR system with the ITU IMT-2020 performance requirements for all parameters evaluated by simulations.

Fixed Spectrum Allocation (FSA) results in suboptimal spectrum utilization, unbalanced system loading and the inability to adapt to system traffic variations when employed in multi-Radio Access Technology (RAT) systems. This paper proposes the use of flexible spectrum management techniques in multi-RAT systems. A Dynamic Spectrum Management (DSM) framework that addresses the shortcomings of FSA, while ensuring the reliable operation of all co-deployed RATs, is presented. Simulations for a system co-deploying HSPA and LTE show that the proposed framework outperforms FSA schemes and is capable of adapting to system traffic variations.Index Terms-Cellular systems, multi-RAT systems, spectrum management.

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Multi-radio access technology (RAT) cellular communication systems limit connected users to utilizing a single RAT even when employing multi-mode user equipment (UE) capable of utilizing multi-RATs. Single-mode access, combined with static spectrum partitioning between co-deployed RATs and independent resource allocation for employed RATs, results in suboptimal spectrum utilization in multi-RAT systems. This paper models user access in multi-RAT systems and proposes enabling multimode UE to simultaneously utilize multiple RATs, using multi-RAT carrier aggregation, to improve the performance and spectrum utilization of multi-RAT systems. Several realizations of multi-mode access with varying implementation requirements are presented and discussed. Detailed system-level simulations, for a system co-deploying High Speed Packet Access (HSPA) and Long-Term Evolution (LTE), are performed to investigate the gains and limitations of different user access configurations in multi-RAT systems.INDEX TERMS Carrier aggregation, cellular communication systems, multi-carrier systems, multi-radio access technology systems, user equipment.