ing for simple exploitation of the spatial dimension by transmission of multiple data streams in parallel [21] over different spatial layers. In certain outdoor scenarios with strong line of sight (LOS), however, the radio channel from a UE to a single site might be rank deficient, thus limiting the achievable spatial multiplexing gains. More © 2009 by Taylor & Francis Group, LLC Cooperative Transmission Schemes severe are frequent coverage holes due to strong shadowing or penetration losses for indoor users served by an outdoor eNB. In such holes, the signal- to-noise ratios (SNRs) are small. Because LTE is a cellular radio system, interference from adjacent radio cells is even more detrimental. From mul- ticell simulations, it is known that about 40% of the UEs will achieve wide- band signal-to-interference-and-noise ratios (SINR) below 0 dB. It is well known from projects like the EU-founded project WINNER [22] that sig- nificant spatial multiplexing gains require-depending on the scenario- SINRs in the order of 5-10 dB or more. SINRs larger than 5 (10) dB will be achieved for only 30 (15)% of best-case UEs. With frequency-flat single- user transmission, as in HSDPA, the major MIMO gains will stem from diversity realized by optimum combining or beam forming. Advanced proposals for frequency-selective MU-MIMO transmission, which go beyond the scope of LTE release 8, cope better with this situation by exploiting frequency-selective multiuser diversity. For this purpose, each UE resource block (RB) with SINRs above average is scheduled with its best-fitting MIMO mode. In combination with codebook-based LTE like beam forming, spatial multiplexing to one or multiple users (SDMA) will be possible on more than 90% of the RBs, even though the SINR of many UEs is below 0 dB due to multicell interference [17]. As will be shown in more detail later, cooperation now turns detrimental interference power into useful signal energy, thus providing macrodiversity and beam-forming gains. Moreover, the channel rank is increased 