adjacent channel is defined by the ACS. The two para- meters when combined define the total leakage between two transmissions on adjacent channels. That ratio is called the adjacent channel interference ratio (ACIR) and is defined as the ratio of the power transmitted on one channel to the total interference received by a receiver on the adjacent channel, due to both the transmitter (ACLR) and the receiver (ACS). This relationship between the adjacent channel parameters is given as ACIR = 1/(1/ACLR + 1/ACS). The ACLR and ACS can be defined with different New Radio Access RF and Transceiver Design Considerations In-channel selectivity Narrowband scenario (BS) blocking Out-of-band 1 RB (BS) blocking (CW) Interfering resource CW (UE) blocks In-band Wanted resource blocking blocks LTE wanted signal Receiver operating band Figure 5.10 Illustration of the BS/UE requirements for receiver susceptibility to interference [5,10]. channel bandwidths for the two adjacent channels, which is the case for some requirements set for NR due to the bandwidth flexibility. The ACLR limits for NR devices and base station have been derived based on extensive analysis of NR coexistence with NR or other systems on adjacent carriers. For an NR BS, there are ACLR requirements both for an adjacent channel with an NR receiver of the same channel bandwidth and for an adjacent LTE receiver. The ACLR requirement for NR BS is set to 45 dB. This is considerably more stringent than the ACS requirement for the device, which implies that in the downlink, the device receiver performance will be the limiting fac- tor for ACIR and consequently for coexistence between the base stations and the devices. From a system perspective, this choice is cost-efficient since it moves implementation com- plexity to the BS, instead of requiring all devices to have high-performance RF components. In the case of carrier aggregation in a BS, the ACLR limits are applied as for any multi- carrier transmission, where the ACLR requirement will be defined for the carriers on