 on FR2 Relaxed ACLR Requirements on MPR Gating Factor 12.4.5 Multi-Band Support and Carrier Aggregation 12.4.6 OTA Conformance Test Challenges 378 Dual Uplink Performance Challenges for NSA Operation 381 12.5.1 From Single UL to Dual UL Operation 381 12.5.2 EN-DC: Explosion of LTE-CA Combinations as Baseline to 5G 12.5.3 FR1 UE Types and Power Sharing in EN-DC 12.5.4 Dual Uplink Challenges for EN-DC Operation in FR1 Contents 12.5.4.1 Intra-Band Challenges 12.5.4.2 Inter-Band Challenges 12.5.4.3 Example of MSD/A-MPR/MPR Challenge with DC_(n)71AA 388 12.5.5 Dual Uplink Challenges for EN-DC and NN-DC Operation in FR2 Examples of UE Implementation Challenges 392 12.6.1 More Antennas, More Bands to Multiplex, and More Concurrency 12.6.2 FR2 Antenna Integration and Smartphone Design 395 Summary 396 References 397 5G Modem Design Challenges 399 YihShen Chen, Jiann-Ching Guey, Chienhwa Hwang, Peikai Liao, Guillaume Sébire, Weide Wu, and Weidong Yang Introduction 399 High Data Rate, System Flexibility, and Computational Complexity 401 13.2.1 Channel Coding Aspects Versus UE Complexity 401 13.2.2 MIMO and Network Flexibility Versus UE Complexity Low Latency, Flexible Timing, and Modem Control Flow Complexity 13.3.1 Low Latency Aspects Versus Modem Processing Capability 13.3.1.1 Shorter Slot Duration 408 13.3.1.2 Mini-Slot Transmission 408 13.3.1.3 Multiple PDCCH Monitoring Occasions Per Slot 13.3.1.4 Shorter PDSCH/PUSCH Processing Time 410 13.3.1.5 Preemption Indication 13.3.1.6 Front-Loaded DMRS 411 13.3.1.7 OFDM Symbol-Based PUCCH 411 13.3.2 System Flexibility Versus Modem Control Timing 411 13.3.2.1 Flexible Slot Format Indication 412 13.3.2.2 Flexible Scheduling 413 Multi-RAT Coexistence and Modem Architecture 13.4.1 Dual Connectivity and Modem Architecture 13.4.2 Impact of LTE/NR Coexistence on Modem Design 13.4.2.1 Operating in the New NR Band 13.4.2.2 Supplementary Uplink 13.4.2.3 Carrier Aggregation 13.4.2.4 Operating in the Legacy LTE Band 418 13.4.3 Uplink Transmission Design for Minimizing Intermodulation Effec