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6 December 2002 Power-Efficient Multiple-Subcarrier Modulation Scheme for Optical Wireless Communications
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Proceedings Volume 4873, Optical Wireless Communications V; (2002)
Event: ITCom 2002: The Convergence of Information Technologies and Communications, 2002, Boston, MA, United States
Multiple-subcarrier modulation (MSM) offers several potential advantages for optical wireless systems. MSM makes it possible to perform frequency-division multiplexing, while maintaining the simplicity of intensity modulation and direct detection. Indoor optical wireless systems may be subject to multipath distortion; in such systems, MSM enables transmission at high bit rates with minimal intersymbol interference. The average-power efficiency of MSM is lower than that of baseband modulation techniques, such as on-off-keying or pulse-position modulation, however. We present a technique for improving the average-power efficiency of multiple-subcarrier systems using binary or quadrature phase-shift keying (BPSK, QPSK) with bandlimited pulses, which are, necessarily, not time-limited. In order to insure the non-negativity of the transmitted intensity signal, we use a time-varying bias signal, which is a baseband pulse-amplitude modulation signal also using these pulses. We focus on the problem of designing this time-varying bias signal, which is complicated by the fact that the pulses are not time-limited. We show that the proposed scheme can significantly enhance power efficiency, with only a minimal increase in implementation complexity.
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Byron Yu, Joseph M. Kahn, and Roy You "Power-Efficient Multiple-Subcarrier Modulation Scheme for Optical Wireless Communications", Proc. SPIE 4873, Optical Wireless Communications V, (6 December 2002);

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