tailieunhanh - Ultra Wideband Communications Novel Trends System, Architecture and Implementation Part 8

Tham khảo tài liệu 'ultra wideband communications novel trends system, architecture and implementation part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Synchronization Technique for OFDM-Based UWB System 165 ML -20 -25 -30 _ 0 200 400 600 800 1000 Sample index MMSE 35 30 25 20-0 200 400 600 800 1000 Sample index Fig. 3. Output waveforms of ML and MMSE algorithms at 10 dB SNR Fig. 4. Output waveforms of cc and DT algorithms at 10 dB SNR Fig. 3 depicts the output waveforms of ML and MMSE algorithms at 10 dB SNR. There are plateaus and basins in the output waveforms of ML and MMSE which make the peak energy ambiguous. It is much easier to find accurate timing information in the output waveform of cc in Fig. 4. However there are glitches in cc output waveform which will corrupt the detection of symbol boundary and increase the false alarm probability. The waveform of DT has much lower noise floor compared with cc and there is not any glitch. 166 Ultra Wideband Communications Novel Trends - System Architecture and Implementation Architecture of the matched filter Matched filter is the basic component in timing synchronization for detecting a known piece of signal in noise. The architecture of mated filter determines the complexity and the power consumption of the timing synchronizer. An optimum architecture of the matched filter for OFDM-based UWB is provided as shown in Fig. 5. To satisfy 528 Msps throughput the baseband receiver system of UWB is designed at 132 MHz clock frequency with four parallel paths and twelve-level pipelines. For low complexity both the received signal and the preamble coefficients are truncated to sign-bit. In this case five-bit multipliers can be replaced with NXOR gates. In addition the 128 sign-bits of preamble coefficients are generated by spreading a 16 sign-bit sequence with an 8 sign-bits sequence as follows sgn Ci6 -D i ix 1 j l 2 . 8 1 where fl and bj are 1 or -1. According to 12 the 128 taps matched filter can be decomposed to 16 taps cascaded with 8 taps as shown in Fig. 5. With the decomposition the processing period of the matched filter can be reduced to 19 and the .

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