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Nonbinary Orthogonal Modulation in Direct-Sequence Spread Spectrum Communication Systems

Nonbinary Orthogonal Modulation in Direct-Sequence Spread Spectrum Communication Systems. Michael Y. Tan Home Institution: Clemson University Advisor: Michael B. Pursley Date: August 1, 2002. Outline. Motivation Background System Description Simulation Results Conclusion Future Work.

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Nonbinary Orthogonal Modulation in Direct-Sequence Spread Spectrum Communication Systems

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  1. Nonbinary Orthogonal Modulation in Direct-Sequence Spread Spectrum Communication Systems Michael Y. Tan Home Institution: Clemson University Advisor: Michael B. Pursley Date: August 1, 2002

  2. Outline • Motivation • Background • System Description • Simulation • Results • Conclusion • Future Work

  3. Motivation • Personal Communication Service (PCS) in reverse link • Wireless Local-Area Networks (WLAN)

  4. Background:Direct-sequence spread spectrum (DSSS)

  5. Background (cont.):M-ary Orthogonal Modulation • Definition: If Φ0(t) and Φ1(t) are orthogonal, then • log2(M) bits of data one of M orthogonal signal

  6. Background (cont.):Walsh-Hadamard Signals • Simplest Hadamard matrix: • Relationship between Hx+1 and Hx is:

  7. Description of System:Transmitter • 6 bits of d(t) one of 64 Walsh-Hadamard signals • 1 PN chip per orthogonal signal chip • m(t) is not spread

  8. Description of System (cont.):Channel • Channel with Additive White Gaussian Noise (AWGN) and multipath interference

  9. Description of System (cont.):Receiver

  10. Simulation Process:Matlab • Properties of signals, channel, and receiver: • Coherent demodulation • Chip waveform is rectangular with duration Tc • Multipath delay = multiple of chip duration • Multipath causes intrasymbol interference • Chip-matched filter sampling rate = chip rate • Discrete-time matched filter sampling rate = symbol rate

  11. Results:AWGN

  12. Results:AWGN & One Multipath

  13. Results:AWGN & Two Multipaths

  14. Conclusion: • The system will perform efficiently for sufficiently high power ratio. • Lower desired probability of symbol error leads to smaller range of power ratio that will provide efficient system performance.

  15. Future Work: • Rake receiver • Other modulation techniques

  16. Questions?

  17. m-sequence

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