tion, a total DAI (tDAI). The cDAI included in the DCI indicates the number of scheduled downlink transmissions up to the point that the DCI was received in a carrier first, time second order. The tDAI included in the DCI indi- cates the total number of downlink transmissions across all carriers up to this point in time, that is, the highest cDAI at the current point in time. The cDAI and tDAI are represented with decimal numbers with no limitation. In practice, 2 bits are used for each and the num- bering is calculated in modulo four. This can be compared with the semi-static codebook which would require a fixed number of entries regardless of the number of active transmis- sions. If one transmission on a component carrier is lost, without the DAI mechanism, this would result in mismatched codebooks between the UE and the gNB; however, as long as the device receives at least one component carrier, it knows the value of the tDAI, hence the size of the codebook at this point in time. Furthermore, by checking the values received for the cDAI, it can conclude which component carrier was missed and that a negative acknowledgment should be assumed in the codebook for this position [8]. There are two different types of codebook determination algorithms referred to as Type 1 and Type 2. Each of these types is divided into two cases depending on whether the HARQ-ACK is reported on PUCCH or PUSCH, whose usage are configured and signaled through RRC parameters. The codebook determination algorithm types and the associated RRC parameters are summarized in Table 4.20. New Radio Access Physical Layer Aspects (Part 2) 551 Table 4.20: HARQ-ACK codebook determination [8]. Codebook Determination Type Condition CBG-based HARQ-ACK codebook determination PDSCH-CodeBlockGroupTransmission = ON Type-1 HARQ-ACK codebook determination pdsch-HARQ-ACK-Codebook = semistatic Type-1 HARQ-ACK codebook in PUCCH Type-1 HARQ-ACK codebook in PUSCH Type-2 HARQ-ACK codebook determination pdsch-HARQ-ACK-Codebook = dynamic Type-2 HARQ-ACK codebook in 