ncreases if carrier-aggregation- or code-block-group-based HARQ-ACK is employed in the downlink. The formats 2-4 are also the formats to use for CSI feedback, again categorized as a short format (2) and long formats (3 and 4). The differentiation between short and long formats is again similar as with the small payload size formats, but there are two variants of the long format. Format 3 provides the maximum payload size allowed by the polar code, while format 4 is able to support a lower UCI payload size, but it allows for multiplexing up to four users on the same resource for better user capacity (Figure 6.23). One restriction with the LTE PUCCH design was symmetric frequency hopping, which is quite suitable for a typical setup but somewhat suboptimal for cases where one band edge is experiencing more interference or needs to be left unused due to adjacent systems. New Radio (NR) PUCCH frequency hopping is supported for the long PUCCH formats (1, 3, and 4) is fully flexible, SO that it is possible to place the first hop of the PUCCH freely in frequency, and the second hop again freely and independently of the first hop to another location in frequency. The number of symbols allocated for the long PUCCH is divided equally between the first and the second hop, and the PUCCH transmission remains contiguous in time. Long PUCCH formats (1, 3, and 4) also support multi-slot PUCCH using repetition. This mechanism is designed for maximum coverage, although it costs more in terms of delay and overhead. When multi-slot PUCCH is used, inter-slot frequency hopping can be employed (Figure 6.24). The UE is configured with PUCCH resource sets, each resource set containing several PUCCH resource configurations including the PUCCH format and its time/frequency location. When the UE receives a DCI on the PDCCH that triggers a corresponding DDDDDDDDDDGGUU 1 slot (14 symbols) Figure 6.23 Switching slot with a two-symbol PUCCH after the switching gap. 6.9 Uplink Signaling Transmission PUCCH 1st hop PUCCH 1st hop PUCCH 2nd hop PUCCH