Comparative Performance Analyses for Trellis-Coded PPM and Uncoded PPM systems over Optical Wireless Dispersive Channels

• Main Authors: Hong-Wen Lin, 林鴻文
• Other Authors: MIIN-JONG HAO
• Format: Others
• Language: en_US
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/13240968534267332380

碩士 === 國立高雄第一科技大學 === 電腦與通訊工程所 === 90 === In the wireless optical communication environment, data transmission by an optical signal has the following advantages over a conventional RF signal: offering a large potential bandwidth, immunity to multipath fading, and allowing the reuse of the same spectrum in every room of a building. In practice we use the Pulse Position Modulation (PPM) scheme to increase the power efficiency. However, due to its poor bandwidth efficiency, PPM is more susceptible to intersymbol interference (ISI). In this thesis, we analyze the performance of PPM with trellis-coded modulation (TCM) on indoor wireless infrared channels. We show that the application of TCM to PPM can effectively reduce the influences of ISI induced by dispersive channel. The TCM 8-PPM with the code rate of 2/3 and the TCM 16-PPM with the code rate of 3/4 are used for our study to comply with practical situation. The upper bound and lower bound of the BER performance are derived and the numerical results are compared with these from simulations. We execute the bit-error rate analysis and evaluate the signal-noise ratio requirements for different TCM-PPM schemes over the dispersive channel with various delay spreads. Finally we present Monte Carlo simulation results to verify our analysis. Our results indicate that TCM is a very promising coding technique for L-PPM on high speed infrared channels.