Channel Estimation Method For Ofdm-uwb Systems

Ultra-wideband (UWB) technology is a promising high data-rate, short-distance and low-power wireless transmission solution which has attracted more and more attention both from the academic and the industry. Released as ISO/IEC 26907, Multi-Band Orthogonal Frequency Division Multiplexing (MB-OFDM) UWB technology has finally been approved by the ISO and IEC and became the first UWB standard in the world.First of all, this paper briefly introduces the digital baseband of MB-OFDM UWB systems in which the author emphasizes on presenting a novel low-complexity FPGA implementation of (de)interleaver. The proposed approach uses of dual-port memory from Xilinx IP core which possesses a unique feature that read-width is not necessarily equal to write-width. FPGA synthesis reports are provided that our design can reduce area consumption significantly and the numbers of occupied slices are reduced by 46% and 78% for interleaver and deinterleaver, respectively.After that, as the kernel of this paper, the author proposes a robust and low-complexity channel estimation algorithm using pseudo-pilot for MB-OFDM UWB systems. The propose algorithm can effectively protect against inter-symbol interference (ISI) caused by multipath channel. Without any prior knowledge of channel statistics and noise variance, DFT-based channel estimation is usually used to improve the performance of least square (LS) channel estimation. However, additional FFT/IFFT operations in DFT-based algorithm drastically increase the computational complexity and corresponding area and power consumption, whereas a novel pseudo-pilot assisted channel estimation (PPACE) algorithm is presented in this paper using a 32-point FFT to afford robust and low complexity channel estimation with acceptable performance loss. It will be shown in simulation results that proposed low complexity PPACE algorithm is better than traditional DFT-based algorithm and linear minimum mean square error (LMMSE) algorithm. We also proposed here a generalized low complexity windowing technology for DFT-based channel estimation according to UWB channel model parameters to improve the mean square error (MSE) performance.Moreover, combining with multiple-input multiple-output (MIMO) technology is a promising development and tendency of UWB which can provide more than 1Gbps data rate for ultra-high speed wireless transmission applications. However, for MIMO-OFDM systems the received signal is the superposition of different signals from different antennas and noise. If the channel parameters corresponding to each transmitter and receiver antenna pair are estimated by the approach developed previously in OFDM systems, the signals from other transmitter antenna(s) will become interference. The signal-to-interference ratio will always be less than 0 dB, and the MSE of the estimation will be very large.At last, this paper proposes a low-complexity channel estimation algorithm for MIMO-OFDM UWB system in virtue of PPACE algorithm. The simulation results and the FPGA implementation results prove that the novel algorithm outperforms the traditional MIMO-OFDM channel estimation algorithm and implementation complexity has been reduced dramatically.In conclusion, the PPACE algorithm proposed in this paper can not only be applied in MB-OFDM UWB and MIMO-OFDM UWB systems but also be suitable for other OFDM-based wireless communication systems with minor modification.