a (DA; A = 4/3 versus omnidirectional antenna (OA; A = 2 . The 240° directional antenna of RNs is adjusted to radiate only into the outer hexagons. This is the area that is fully served by RNs as the best server. Figure 8.23 shows that an outer ring of approximately 30% within the hexagon is best served by RNs. We obtain the performance results in Table 8.2 for these two scenarios under "throughput TDM DA G14" and "coverage TDM DA G14." Switching on SDM means all RNs may transmit to and receive from their UTs in parallel and their interference is accounted for. The results are provided in Figure 8.24 for the C 2009 by Taylor & Francis Group, LLC Multihop Extensions to Cellular Networks Table 8.2 Downlink Capacity and Spectral Efficiency of the Discussed Scenarios Scenario DL Capacity (b/s) DL Spectral Efficiency (b/s/Hz) Throughput TDM DA G14 50,973,029 2.8318349554 Throughput SDM DA G14 58,642,110 3.2578950216 Throughput TDM DA GO 48,737,548 2.7076415712 Throughput TDM OA G14 50,730,651 2.8183695086 Throughput SDM OA G14 53,799,503 2.9888612873 Coverage TDM DA G14 34,087,801 1.8937667754 Coverage SDM DA G14 64,801,466 3.6000814652 Coverage TDM DA GO 21,385,809 1.1881005356 Coverage TDM OA G14 34,937,225 1.9409569593 Coverage SDM OA G14 65,309,985 3.6283325128 -2000 -4000 -6000 -6000 -4000 -2000 X (m) Figure 8.24 Best server chosen in a coverage-increasing scenario with sector- ized relay antennas. C 2009 by Taylor & Francis Group, LLC Long Term Evolution: 3GPP LTE Radio and Cellular Technology -2000 -4000 -6000 -6000 -4000 -2000 X (m) Figure 8.25 Best server chosen in a capacity-increasing scenario when spatial multiplexing is switched on (i.e., all relays may send in parallel). This causes intra- cell interference, reducing the effective relay-supported area. coverage scenario and in Figure 8.25 for the throughput-enhancement scenario. Especially in the boundary area between RNs, we observe that no relay can cover this in a useful way because of the strong interference between those RNs. The pre- ceding results