imum beam formers is obtained in closed form [50]: (7.17) This interference function is a special case of the generic interference function (7.13). Using this framework, we compare different combining strategies in a multicell scenario. In Figure 7.8, the achievable SINR is plotted over the total transmission power in the system. By achievable SINR, we mean the value at which the CDF equals 0.5. The system consists of seven cell sites, with three sectors each and two antennas per sector. The cell radius is 300 m and the SCME (spatial channel model extended) from the 1st winner project. Each sector contains two randomly placed users with a single antenna each. Thus, we have a system with a total number of 42 transmit antennas and 42 users. The total transmit power is the sum of all the users' individual powers. No power allocation is used, SO each user transmits at full power. Full frequency reuse is assumed, and all users share the same frequency band and time slot. The results are averaged over 500 random experiments. The following space diversity techniques are compared: SD (selection diversity). At each base station, the antenna with the strongest path gain is chosen. MRC (maximum ratio combining). At each base station, MRC is performed with respect to the users' channels. MMSE (minimum mean square error). For each user, the associated base station performs antenna combining such that MMSE is minimized. This corresponds to maximizing the individual SINR. In contrast to the MRC strategy, the interferers' channels are assumed to be known. MRCcoop. Maximum ratio combining is performed jointly for all base sta- tions. This means that all antennas are coherently cooperating. ZFcoop (zeroforcing with full base station cooperation). The difference from MRCcoop is the full knowledge of the interferers' channels. Thus, inter- ference can be completely eliminated by transmitting orthogonally to the interferers' channels. MMSEcoop. All base station antennas are combined coherently, based on the MMSE criterion. For large 