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Digital Radio

Digital Radio. Group 6 電機四 B92901035 柯浩賢 電機四 B92901038 粘 紘 電機四 B92901049 黃柏堯. Agenda. Motivation System Architecture Assumptions Design problems Waveform simulation. Motivation. Design an all-digital radio tx/rx system

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Digital Radio

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  1. Digital Radio Group 6 電機四 B92901035 柯浩賢 電機四 B92901038 粘 紘 電機四 B92901049 黃柏堯 NTUEE Communication Laboratory Spring, 2007

  2. Agenda • Motivation • System Architecture • Assumptions • Design problems • Waveform simulation NTUEE Communication Laboratory Spring, 2007

  3. Motivation • Design an all-digital radio tx/rx system • Desire to implement channel coding and modulation on hardware • Try to implement software radio on FPGA with fast ADC and DSP knowledge. NTUEE Communication Laboratory Spring, 2007

  4. System Architecture • 8ksps ADC/DAC, 8 bits per sample • 128-bit CC encoder/decoder (Viterbi Algorithm) • 16*16 block interleaver/deinterleaver Mic. 8kHz 128kHz 128kHz 2MHz CC Encoder MOD (BPSK) CODEC (ADC) Interleaver 8 8 Channel CODEC (DAC) Viterbi Decoder 8 DEM (BPSK) 8 Deinterleaver 2MHz 128kHz 128kHz 8kHz Headphone NTUEE Communication Laboratory Spring, 2007

  5. System Architecture Mic. 8kHz 128kHz 128kHz 2MHz CC Encoder MOD (BPSK) CODEC (ADC) Interleaver 8 8 Channel (Digital) CODEC (DAC) Viterbi Decoder 8 DEM (BPSK) 8 Deinterleaver 2MHz 128kHz 128kHz 8kHz Headphone BPSK mapping D/A ..011010.. 10111010 Channel (Analog) We can change frequency and modulation A/D(1M) ..011010.. BPSK De-mapping 10111010 NTUEE Communication Laboratory Spring, 2007

  6. Assumptions • Tx and Rx are perfect synchronized • Fixed phase difference between tx and rx • Use different lines to simultaneously transmit synchronization signal and data NTUEE Communication Laboratory Spring, 2007

  7. Design problems • Synchronization between modules • SYNC signal • Timing of RAM • Double-buffer is necessary in real-time transmission NTUEE Communication Laboratory Spring, 2007

  8. Waveform simulation • CODEC I/O • Channel coding and interleaver • Sinusoidal Modulation and Demodulation • With different sinusoidal frequency NTUEE Communication Laboratory Spring, 2007

  9. CODEC I/O First ADC sample Right channel Left channel NTUEE Communication Laboratory Spring, 2007

  10. CODEC I/O (cont’d) 11100011_10010000 11100011 NTUEE Communication Laboratory Spring, 2007

  11. Channel coding NTUEE Communication Laboratory Spring, 2007

  12. Channel coding (cont’d) 11001100000011… NTUEE Communication Laboratory Spring, 2007

  13. Channel coding (cont’d) 11001100000011… NTUEE Communication Laboratory Spring, 2007

  14. Modulator & Demodulator Modulator + Demodulator: Data rate=64kHz Use 64kHz sin-wave w/ sampling rate = 1MHz NTUEE Communication Laboratory Spring, 2007

  15. Matched Filter & Decision Making Make decision: correlator > 0 => 0 is received Modulator + Demodulator: Data rate=64kHz Use 64kHz sin-wave w/ sampling rate = 1MHz Next received bit will be 1 NTUEE Communication Laboratory Spring, 2007

  16. Use Another Frequency In this case, modulation can bear higher level of noise (signal power quadruple) Modulator + Demodulator: Data rate=64kHz Use 256kHz sin-wave w/ sampling rate = 4MHz NTUEE Communication Laboratory Spring, 2007

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