l for delivering the theoretical capacity growth. For instance, the capacity of spatially multiplexed MIMO systems is known to degrade in LOS channel conditions, as compared to NLOS conditions, because a dominant LOS path component reduces the channel scattering effects. In practice, LOS conditions are commonplace occurrences in cellular systems. Antenna polarization can be used to compensate the lack of spatially multi- plexing via polarization multiplexing [4-7]. Polarization multiplexing exploits the second strong singular value in the MIMO transfer matrix by using orthogonally © 2009 by Taylor & Francis Group, LLC Early Real-Time Experiments and Field Trial Measurements polarized antennas, also known as cross-polarized antennas. The benefits of using XPD antennas in cellular MIMO-OFDM systems are twofold: Cross-polarized antennas yield a more compact antenna design and they enhance the throughput as compared to copolarized antennas. In this section, we present the measurement results with XPD antennas for a MIMO-OFDMA system. We show a comparison of performance results between XPD and copolarized antennas. The results highlight the importance of XPD antennas in MIMO throughput enhancement in cellular systems. Further analy- sis is also made on the importance of these antennas for OFDMA scheduling, which is an important cross-layer aspect of LTE networks. It is seen that XPD antennas are a better choice for providing user fairness along with sum throughput maximization. 11.4.1 2 x 2 Cross-Polarized MIMO Channel Antennas are distinguished as cross-polarized, copolarized, or dual polarized, depending on the plane of signal propagation. Various studies have been con- ducted to model an XPD MIMO channel closely. For instance, Erceg, Sampath, and Catreux-Erceg [5] presented a simple MIMO channel model that predicts the eigenvalue distribution and the capacity of single polarized MIMO chan- nels for specific antenna configurations. Shafi and others [6] presented a simple three-dimensional cross-polarized model and e