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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 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
Motivation • Personal Communication Service (PCS) in reverse link • Wireless Local-Area Networks (WLAN)
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
Background (cont.):Walsh-Hadamard Signals • Simplest Hadamard matrix: • Relationship between Hx+1 and Hx is:
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
Description of System (cont.):Channel • Channel with Additive White Gaussian Noise (AWGN) and multipath interference
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
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.
Future Work: • Rake receiver • Other modulation techniques