UEs PFS, co-pol., 10 UEs PFS, XPD, 2 UEs PFS, XPD, 10 UEs Max-rate, co-pol., 10 UEs Max-rate, XPD, 10 UEs Throughput (Mbps) Figure 11.35 System sum throughput with multiple users. © 2009 by Taylor & Francis Group, LLC Early Real-Time Experiments and Field Trial Measurements path over time. XPD antennas are always seen to outperform copolarized antennas. This observation is consistent with that of colocated users, even though marginal gains are observed due to path loss diversity. The plots are repeated for 10 users, who move along the same path and experi- ence different path loss in each time slot. In OFDMA max-rate scheduling, the sum throughput using copolarized and XPD antennas converges with only 10 users, as in Figure 11.35. This shows that, even for 10 users in the system, the gains of XPD antennas saturate as a result of the channel-hardening effect. One would wonder whether this result is still applicable if additional user fairness is incorporated. With a proportional fair scheduler, a performance gap between XPD antennas and copolarized antennas with 10 users is observed. The throughput difference is approximately 12 Mb/s. These gains are derived from the higher single-user throughput results in Figure 11.28. There it was observed that single-user supportable throughput is higher with XPD antennas for a mean SNR of more than 6 dB. The mean SNR in the measurement track is 27 dB. Therefore, single-user supportable throughput is clearly higher for XPD anten- nas. This higher supportable throughput is more favorable for the purpose of fairness scheduling. For completeness, we show the individual user rate for a random user in the scenario in Figure 11.36 for one, two, and ten UEs. It is observed that the user rate with XPD antennas is always higher. This relates directly to the higher over- all spectral efficiency of XPD antennas. The gap for 10 users between XPD and copolarized antennas is approximately 1.2 Mb/s for the median, a more or less even distribution of sum-throughput gains. Co-Pol., 10 UE XPD, 