ntenna port(s), is on a per-CORESET basis. This implies that in mmWave deployments, which rely on beam-sweeping operations, different CORESET and search space configurations corresponding to different received beams are necessary [8,53]. The CCE structure described in the previous section helps reduce the number of blind decod- ing attempts; however, it is required to have mechanisms to limit the number of PDCCH can- didates that the device is expected to monitor. From a scheduling point of view, restrictions in the allowed aggregations are undesirable as they may reduce the scheduling flexibility and require additional processing at the transmitter side. At the same time, requiring the device to monitor all possible CCE aggregations in all configured CORESETs significantly increases device complexity and power consumption. A search space is a set of candidate control chan- nels comprising a set of CCEs at a given aggregation level, which the device is supposed to monitor and decode. Due to multiple aggregation levels, a device can have multiple search New Radio Access Physical Layer Aspects (Part 2) 467 spaces. There can be multiple SSs using the same CORESET or multiple CORESETs config- ured for a device. A device is not expected to monitor PDCCH outside its active bandwidth part. At a configured monitoring occasion for a search space, the devices will attempt to decode the candidate PDCCHs for that search space. Five different aggregation levels corre- sponding to 1, 2, 4, 8, and 16 CCEs can be configured. The highest aggregation level is meant to support extreme coverage requirements [6,8,14]. The number of PDCCH candidates can be configured per search space and per aggregation level. When the UE attempts to decode a candidate PDCCH, the content of the control channel is declared as valid, if the CRC checks and the device can successfully process the contained information, that is, scheduling assignment, and uplink grants. If the CRC does not pass, the information is either subject to uncorrectable transmissi