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: Direct-sequence spread spectrum (DSSS)

Background (cont.): M-ary Orthogonal Modulation Definition: If Φ 0 (t) and Φ 1 (t) are orthogonal, then log 2 (M) bits of data one of M orthogonal signal

Background (cont.): Walsh-Hadamard Signals Simplest Hadamard matrix: Relationship between H x+1 and H x is:

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

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

Description of System (cont.): Receiver

Simulation Process: Matlab Properties of signals, channel, and receiver: Coherent demodulation Chip waveform is rectangular with duration T c 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

Results: AWGN

Results: AWGN & One Multipath

Results: AWGN & Two Multipaths

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

Questions?

m-sequence