 TDD and FDD bands, a large back-off may also be required to meet unwanted emissions resulting from the inter-modulation products of the two UL signals. 12.5.4.1 Intra-Band Challenges In the Release 15 specifications, uplink intra-band EN-DC was specified for two bands: 41/n41 and 71/n71. Both bands are used in the United States and are subject to special emission requirements from FCC. Furthermore, uplink intra-band EN-DC is very chal- lenging from an emissions point of view as LTE and NR are transmitted simultaneously on one band; therefore, special MPR solutions were developed for these bands. Note that intra-band EN-DC was also specified for the band 3/n3, but the uplink operation was restricted to single switched uplink only, and therefore there was no need for a special MPR solution as both LTE and NR followed single-carrier MPR definitions. The intra-band EN-DC configurations that needed special MPR were DC_(n)41AA, DC_(n)71AA, and DC_41A-n41A. The first two are contiguous intra-band EN-DC configurations, and the third one is a non-contiguous intra-band EN-DC configura- tion. The term "contiguous" means that the LTE and NR carriers are adjacent and non-contiguous, meaning that there is a frequency gap between them. Special MPR due to specific regional requirements (FCC in these cases) is called A-MPR in the 3GPP specifications; thus, we will be using it from now on. How intra-band EN-DC UE calculates A-MPR depends first of all on whether the UE supports DPS or not. If the UE supports DPS, then the LTE modem sets its output power as defined in the LTE specification 36.101. The NR modem calculates A-MPR from formulas developed by simulations and measurements to take into account joint LTE and NR transmissions. After calculating the A-MPR, the NR modem takes also into account concurrent LTE transmissions and decides whether it needs to further scale the NR transmission power down as explained in the previous chapter. If the UE does not support DPS, both LTE and NR modems make a worst-case assumption in terms 