ranularity. At moderate speed of approximately 5-10 km/h and for moderate numbers of users, the reported results maintain full validity. 11.1.1 Functional Description of the Implemented LTE Downlink and Uplink Figures 11.1 and 11.2 show the functional description of the downlink and uplink transmission chains. The uplink has a discrete Fourier transform (DFT) and inverse discrete Fourier transform (IDFT) in addition to the OFDM transmission chain, while the downlink also incorporates a sync channel at time transmission interval (TTI) 0. 11.1.2 Channel Estimation in Downlink and Uplink 11.1.2.1 Complexity of Optimal Interpolation High-quality channel estimation for 3G LTE is a challenge. Pilots are available only on a sparse grid in the time-frequency domain. On intermediate subcarriers and time slots, channel interpolation has to be used. Because the same set of pilots © 2009 by Taylor & Francis Group, LLC Long Term Evolution: 3GPP LTE Radio and Cellular Technology Table 11.1 Transmission Parameters for the Measurement Results Experimental Current Status of LTE System Parameter System Standard Downlink/uplink, full duplex 2.53/2.68 GHz Various bands including UMTS extension band Antennas base station/terminal 2 TRx/2 TRx 2 TRx/1 Tx, 2 Rx Sampling rate 30.72 MHz Bandwidth used Up to 18 MHz Up to 18 MHz Downlink symbol period/ 71.4/70.1 (37.5) ns 71.4/70.1 (37.5) ns uplink long (short) block (LBs only) Cyclic prefix downlink/uplink 4.6875/4.13 ns 4.6875/4.13 ns Total number of subcarriers 2.048 Up to 2.048 Number of used subcarriers Up to 1.200 Up to 1.200 Transmission scheme downlink OFDMA BLAST OFDMA BLAST Modulation in downlink 4, 16, 64 QAM 4, 16, 64 QAM Transmission scheme uplink SC-FDMA CDD SC-FDMA Modulation in uplink 2, 4, 16, 64 QAM 4, 16, 64 QAM Radio frame duration 10 ms 10 ms 0.5 ms 1.0 ms Symbols/TTI in downlink Symbols/TTI in uplink 6 Long, 2 short 12 Long data, 2 long pilots Resource block size 25 Carriers in 1 TTI 12 Carriers in 1 TTI Channel coding Convolutional Turbo Coding Code rates 1/2, 3/4 Var