of control channel elements (CCE), each control channel element consisting of a set of resource element groups (REG). Different code rates for the control channels are realized by aggregating different number of control channel elements. Polar code is used for PDCCH channel coding. Each resource element group carrying PDCCH includes its own DM-RS. QPSK modulation is used for PDCCH modulation. A resource element is the smallest unit of the resource grid consisting of one subcarrier in frequency domain and one OFDM symbol in time domain. A PDCCH corresponds to a set of resource elements carrying DCI. Each NR control channel element consists of six REGs where a REG is equivalent to one resource block (12 resource elements in the fre- quency domain) over one OFDM symbol. The CCE size is designed such that at least one UE-specific DCI can be transmitted within one CCE with lower code rates. An NR REG bundle is further defined comprising 2, 3, or 6 REGs, which provides: (1) it determines the precoder cycling granularity (which affects the channel estimation performance) and (2) it is the interleaving unit for the distributed REG mapping. An NR PDCCH candidate consists of a set of CCEs, that is, 1, 2, 4, 8, or 16, corresponding to aggregation levels (ALs) 1, 2, 4, 8, 16, respectively. A control search space consists of a set of PDCCH can- didates and is closely associated with the ALs, the number of decoding candidates for each AL, and the set of CCEs for each decoding candidate. A search spacein NR Rel-15 is associated with a single CORESET. As shown in Fig. 4.14 CORESET is defined as a set of REGs with a given numerology. In the frequency domain, a CORESET is defined as a set of contiguous or distributed physical resource blocks configured using a six-PRB granularity, within which the UE attempts to blindly decode the DCI. There is no restriction on the maximum number of segments for a given CORESET. In the time domain, a CORESET spans 1, 2, or 3 contig- uous OFDM symbol, and the exact duration is signaled to the UE v