 solution for the two-user case to ensure instan- taneous fairness among the users regarding the number of allocated RBs. 11.3.3 Discussion of Results To conclude, we show the throughput CDF for the outdoor measurements. Figure 11.24 shows the statistics for the individual user rates and the sum rates. The individual user rates ranged from approximately 60 to 70 Mb/s for the median with a total system throughput of 146 Mb/s. We have presented a first real-time PHY and MAC implementation for fre- quency-selective multiuser MIMO using parameters close to the forthcoming 3G LTE standard. High aggregate data rates of more than 100 Mb/s can be realized with incredible flexibility for the resource allocation. We have tested the new MAC © 2009 by Taylor & Francis Group, LLC Long Term Evolution: 3GPP LTE Radio and Cellular Technology Sum-Rate Throughput (Mbps) Figure 11.24 Throughput statistics with fair scheduling. functions in indoor and outdoor measurements with two users moving at pedes- trian speeds. The results confirm the high potential throughput in real propagation environments due to the combination of frequency-selective resource assignment to multiple users, spatial mode selection, and adaptive modulation. Frequency-selective multiuser MIMO is technically feasible for application in next-generation cellular radio, and it implies a significant improvement of the overall system performance. 11.4 Polarization Multiplexing for Multiuser Downlink Antenna polarization techniques have been considered for many years in channel measurement studies. These studies were primarily based on enhancing the signal propagation efficiency. Diversity reception using polarized antennas was utilized as a form of antenna diversity in multiple antenna systems. However, recently, multiple antennas have been observed to provide far more influential multiplexing gains [1] apart from diversity gains. For MIMO systems, signal propagation efficiency alone does not translate to higher realizable through- put. Channel scattering is essentia