tailieunhanh - Vehicular Technologies Increasing Connectivity Part 5

Tham khảo tài liệu 'vehicular technologies increasing connectivity part 5', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | DFT Based Channel Estimation Methods for MIMO-OFDM Systems 111 Unlike in the system in the 3GPP LTE system the time channel SCME typical to urban macro channel model Baum et al. 2005 varies too much due to higher mobility. The orthogonality between training sequences in the 3GPP LTE standard is thus based on the transmission on each subcarrier of pilot symbols on one antenna while null symbols are simultaneously sent on the other antennas. Therefore the LS channel estimates are calculated only for N 150 subcarriers and interpolation is performed to obtain an estimation for all the modulated subcarriers. system 3GPP LTE Channel Model TGn Erceg et al. 2004 SCME Baum et al. 2005 Sampling frequency MHz 20 Carrier frequency GHz 2 FFT size N 64 1024 OFDM symbol duration ụs 4 Useful carrier M 52 600 Cyclic prefix CP 16 72 CP duration ụs MIMO scheme SDM double-Alamouti MIMO rate RM 1 1 2 Ntx Nr 2x2 4x2 Modulation QPSK 16QAM Number of bit m 2 4 FEC conv code 7 133 171 turbo code UMTS Coding Rate Rc 1 2 1 3 Table 1. Simulation Parameters Simulation results Perfect time and frequency synchronizations are assumed. Monte Carlo simulation results in terms of bit error rate BER versus N are presented here for the different DFT based channel estimation methods classical DFT DFT with pseudo inverse and DFT with truncated SVD. The N value can be inferred from the signal to noise ratio SNR Eb Nt a Nt L .SNR No mRcRM a mRcRM 26 where Ó2loise and a2 represent the noise and signal variances respectively. Rc Rm and m represent the coding rate the MIMO scheme rate and the modulation order respectively. and show the performance results in terms of BER versus N for perfect least square LS classical DFT DFT with pseudo inverse DFT Th CP and DFT with truncated SVD for several Th channel estimation methods in 3GPP LTE and system environments respectively. In the context of 3GPP LTE the classical DFT based method presents .