ten-applied technique for cellular radio systems (e.g., WCDMA), it is even more important and more effective in combination with COOPA systems [18]. For conventional cellular systems, antenna tilting requires a difficult trade-off between IF reduc- tion into adjacent radio cells and reduced signal power for UEs of its own radio cell at the cell edge. As CAs form IF-free areas comprising several radio cells, antenna tilting can concentrate on reducing second-instead of first-tier IF. The effect on the overall interference floor can be seen in Figure 7.2, where antenna tilting increases the power ratios between the strongest interferers of the interference floor. As a result, the performance gain due to partial IF cancellation (i.e., a limited number of strongest interferers) is significantly increased. A further, very effective method in this context is Interference Floor Cellular Radio System index eNB index CDF of Strongest Interferers Without Antenna Tilting With Antenna Tilting, OT = 7° Figure 7.2 Interference floor with and without antenna tilting and simulation results for active interference management. At the top, the comparison of UE and eNB indices reveals that strongest IF comes from adjacent cells or second-tier eNBs, where sectors are directed to the center cell. © 2009 by Taylor & Francis Group, LLC Cooperative Transmission Schemes 7bit/s/Hz/cell +300% Default Default + Tilt Default + Tilt + CPS; Default + Tilt + IC; Default + Tilt + CPS + IC; Default + Tilt + CPS + IC + DIC; Capacity in MBits/s Figure 7.3 Gain for active IF management. A CA consists of two sectors and two adjacent NBs. Default = pure SISO; Tilt = antenna tilting; CPS = coordination; IC = IRC; DIC = dynamic IRC of worst-case interferer. advanced IRC at the UEs. When a UE is mobile, the eNBs leading to the strongest interference change quite often [24]. Typical large-scale param- eter (LSP) correlation is in the order of 50 m, which means that, as soon as a UE has moved by about 50 m, another eNB might become the strongest interferer.