ned in [6] and [7] and for 5G in [8] and [9]. Figure 8.20 shows the BTS-to-BTS increase in the noise floor assuming the ACLR is 45 dB, and the UE-to-UE increase in the noise floor assuming the ACLR is 30 dB. The potential interference even with these rather modest assumptions in the victim BTS can be tens of dB above the thermal noise floor even several kilometers away. Sim- ilarly, below, the UE-to-UE interference can be severe even if the UEs are separated by 8 Deployment Aspects Adjacent channel interference, ACLR = 30dB, TX.P = 0.2, f = 3500 MHz Function of pathloss Function of distance, FSPL, ant gain = 0 dB UE to UE isolation (dB) UE to UE distance (km) Figure 8.21 Adjacent channel UE-to-UE interference. Adjacent channel selectivity, TXP = 80 W, f = 3500 MHz, ACS = -52 dBm, BW = 100 MHz f(coupling loss) f(distance), FSPL, tx.gain = 27 dB, rx.gain = 9dB Coupling Loss (dB) BTS to BTS distance (km) Figure 8.22 Adjacent channel receiver selectivity in BTS. hundreds of meters if they are located in open space. At first sight, this may seem not too serious, but if, for example, a special event is considered where there can be thousands of UEs concentrated in small area, the service would be severely impacted. As the ACS performance requirement in 3GPP is very similar to the ACLR requirement, only ACLR pictures are shown here (Figure 8.21). The ACS is a measure of the receiver's ability to receive a wanted signal at its chan- nel frequency at the antenna connector in the presence of an adjacent channel signal, and these are also specified in [8] and [9]. Like the ACLR, the ACS would be a potential cause of degraded performance in BTSs up to several kilometers away in case there is no synchronization and coordination between one's own and adjacent channel opera- tion. Interference considering ACS in BTS reception is shown in Figure 8.22 and in UE reception is shown in Figure 8.23. UE-to-UE ACS poses a smaller problem but would cause issues, for example, in sta- diums where a high concentration of devices would have