Tuyển tập báo cáo các nghiên cứu khoa học quốc tế ngành hóa học dành cho các bạn yêu hóa học tham khảo đề tài: Differential Amplitude Pulse-Position Modulation for Indoor Wireless Optical Communications | EURASIP Journal on Applied Signal Processing 2005 1 3-11 2005 Hindawi Publishing Corporation Differential Amplitude Pulse-Position Modulation for Indoor Wireless Optical Communications Ubolthip Sethakaset Department of Electrical and Computer Engineering University of Victoria P. O. Box 3055 STN CSC Victoria BC Canada V8W 3P6 Email usethaka@ T. Aaron Gulliver Department of Electrical and Computer Engineering University of Victoria P. O. Box 3055 STN CSC Victoria BC Canada V8W 3P6 Email agullive@ Received 31 March 2004 Revised 28 August 2004 We propose a novel differential amplitude pulse-position modulation DAPPM for indoor optical wireless communications. DAPPM yields advantages over PPM DPPM and DH-PIMa in terms of bandwidth requirements capacity and peak-to-average power ratio PAPR . The performance of a DAPPM system with an unequalized receiver is examined over nondispersive and dispersive channels. DAPPM can provide better bandwidth and or power efficiency than PAM PPM DPPM and DH-PIMa depending on the number of amplitude levels A and the maximum length L of a symbol. We also show that given the same maximum length DAPPM has better bandwidth efficiency but requires about 1 dB and dB more power than PPM and DPPM respectively at high bit rates over a dispersive channel. Conversely DAPPM requires less power than DH-PIM2. When the number of bits per symbol is the same PAM requires more power and DH-PIM2 less power than DAPPM. Finally it is shown that the performance of DAPPM can be improved with MLSD chip-rate DFE and multichip-rate DFE. Keywords and phrases differential amplitude pulse-position modulation optical wireless communications intensity modulation and direct detection decision-feedback equalization. 1. INTRODUCTION Recently the need to access wireless local area networks from portable personal computers and mobile devices has grown rapidly. Many of these networks have been designed to support multimedia with high data rates .
