ard Period 0.2 ms 0.2 ms 0.2 ms 0.2 ms Figure 11.25 Subframe structure. Table 11.9 Major radio link parameters. Center frequency 4.65 GHz System bandwidth 400 MHz (4 X 100 MHz) Duplex Waveform CP-OFDM both uplink and downlink TTI length 0.2 ms Subcarrier spacing 75 kHz CP and GP length 0.75 us and 0.95 us Number of subcarriers 1280 subcarriers per carrier Modulation QPSK (R = 1/6, 1/3, 0.5, 0.8), 16-QAM (R = 0.5, 0.8), 64-QAM (R = 0.5, 0.8) 8-stream MIMO Number of RF branches 8 (14 dBm at each branch, 23 dBm in total) 2, 4, or 8 layers depending on the Rank. At the receiver side, MIMO is decoded based on channel estimation using the DM-RS symbol, which is pre-coded with the same pre- coding matrix as the data symbols, and based on MMSE-based channel equalization. Error detection is based on cyclic redundancy check (CRC) bits attached at each trans- port block. One precoding matrix is supported for each rank. The same MCS has been used for each MIMO stream. The theoretical maximum throughput of the system is greater than a total of 10 Gbps throughout the downlink and uplink by using rate 0.8 coded 64-QAM and the 8x8 MIMO scheme. In this trial, the TDD ratio is set to 1: 9 as 11 Measurements +45 pol -45 pol The distance between antenna sub-array Figure 11.26 BTS antenna configuration. uplink: downlink; hence, the theoretical throughput is 1.07 and 9.67 Gbps in the uplink and downlink, respectively. The RF system has eight branches and is configured to have 14 dBm per TX, 23 dBm in total from the system. The base transceiver station (BTS) and user equipment (UE) use the same RF system but with different antenna configurations. The BTS uses a patch array antenna with +45° polarization. The distance between the antenna sub-arrays is 3.31 in the horizontal direction and 2A in the vertical direction. Each sub-array has eight antenna elements and is connected to one RF branch. This is illustrated in Figure 11.26. For the UE side, we used two different antenna configurations: (1) same antenna con- figuration as the BTS an