 for low latency in the first release of NR. In the next release (Release 16), a service called Ultra-Reliable Low Latency Com- munications (URLLCs) is studied as further use cases with tighter requirements have been identified as an important area for NR evolution; also, Release 15 use cases need to be enhanced. The potential physical layer improvements for further latency reduction include the following: PDCCH enhancements: Compact format of DCI, increased PDCCH monitoring capa- bility Uplink control information enhancements: Enhanced HARQ feedback methods such as increased number of HARQ transmission possibilities within a slot Enhancements to scheduling/HARQ/CSI processing timeline 13.3.2 System Flexibility Versus Modem Control Timing ITU-R defined a set of capabilities needed for an IMT-2020 technology to support var- ious use cases and usage scenarios. This set includes the peak data rate, user experi- enced data rate, area traffic capacity, spectrum efficiency, network energy efficiency, mobility, latency, and connected density. These capabilities need not be met simultane- ously - various combinations of these capabilities allow the provision of different types of services. For instance, a mobile broadband service with a very high peak data rate and user experienced data rate need not feature very low latency. For this reason, one of the design philosophies of NR is flexibility. The network, by means of flexible configura- tions, can adapt its many parameters to meet the required capabilities of any particular service. 13 5G Modem Design Challenges Such flexibility leads to challenges in the design and implementation of a device. Job multitasking becomes more complicated with flexibility in configurations. In a modem, multiple operations are executed pipelined and in parallel. They include the support of layer 1 control, data channel processing, HARQ-related signaling, physical layer proce- dures, measurements, and SO forth. These tasks are executed at device components such as DSPs, hardware, memory, and