C_1A-n77A (Figure 12.18b), where an IMD2 product may lead to approximately 30 dB LTE MSD. This configuration is eligible for SUO, and if the UE decides to request this mode, no MSD would occur. This group is currently specified for 2, 3, 4, and 5 bands (e.g. DC_1A-3A-5A-7A_n78A), but nothing precludes adding more bands. Figure 12.18c illustrates the case of FDD intra-band non-contiguous operation, such as that of DC_3A_n3A, where depending on the gap width, an IMD3 may overlap with either LTE or NR PCC and lead to a large desense. In Rel-15, only SUO is supported, but in Rel-16, the proposed MSD levels beat all 3GPP records with 44 dB MSD using 1 PA UE architecture and approximately 33 dB using 2 PA architecture. Note that this can apply equally to LTE or NR Pcell as their relative positions can be swapped, that is, LTE below NR or NR below LTE. Inter-band combinations can also operate with a third transmission in FR2, as shown in Figure 12.18d with the example of DC_1A_n77A-n257A. The addi- tion of n257 does not contribute to further desense since mmWave modules are physically separated (separate antenna module, Tx chains) and isolated by a large frequency distance. This group is currently specified for 2, 3, 4, and 5 bands (e.g. DC_1A-3A-5A-7A-7A_n257A). Although not shown in Figure 12.18, if one of several bands is added to a "parent 2-band," the EN-DC configuration may lead to new sources of IMD. RAN4 has decided to specify only the additional MSD cases. For example, DC_1A-3A_n77A is a three band extension of case (B) DC_1A_n77A, where The two band "parent" band 1 MSD due IMD2 between n77 and Band 1 remains at 30 dB and is not specified to avoid overloading the tables. However, band 1 as an SCELL may also undergo 31 dB MSD due to an IMD2 between Band 3 and n77. Band 3 as an SCELL may also undergo 31 and 8.5 dB MSD due to an IMD2 and an IMD4, respectively, between Band 1 and n77 transmissions. Other EN-DC variants include FR1 and FR2 and are currently specified up to six bands (e.g. DC_1A-3A-5A-7A_n78A-n257A) 