y are required to switch between transmit and receive modes simultaneously. The interfering BTS antenna gain here and in the following cases is assumed to be 27 dBi and victim antenna 9 dBi per connector. The receiving end antenna gain is the gain 8 Deployment Aspects Intra-frequency interference, TX.P = 80 W, f = 3500 MHz, BW = 100 MHz f(coupling loss) f(distance), FSPL, tx.g = 27 dB, rx.g = 9 dB Coupling loss (dB) BTS to BTS distance (km) Figure 8.17 Intra-frequency BTS-to-BTS interference increase as a function of coupling loss between BTSs and as a function of distance assuming free space loss between BTSs. Intra-frequency interference, TX.P = 0.2 W, 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 8.18 Intra-frequency UE-to-UE interference. of a single transceiver array boundary connector. The coupling loss is the loss between the transmitter and receiver connectors. Similarly, when two UEs are near each other, for example, in the same room and served by two different BTSs with timing differences, they can interfere with each other. Figure 8.18 show the noise floor increase assuming there is LoS between the two UEs. The victim UE could potentially suffer from interference of tens of dBs above the ther- mal noise even if the separation is tens to hundreds of meters. In special event conditions where the UE density is high, this would quite likely result in severely degraded service. A relatively rare mode of radio propagation which is often called atmospheric ducting is also worth mentioning. During certain weather conditions such as inversion layers, radio waves are bent between different horizontal atmospheric layers of different densi- ties, forming a waveguide. This can result in a radio channel in which the radio waves can follow the curvature of Earth and have much reduced attenuation. Due to the reduced attenuation, interference can occasionally be experienced even hundreds of kilome- ters away. Some geographical areas a