Development, Simulation and Evaluation of the IEEE 802.11a Physical Layer in a Multipath Environment

摘要

This thesis describes the development and simulation of the newly proposed IEEE 802.11a physical layer and demonstrates the effects of Additive White Gaussian Noise (AWGN) and multipath on its performances. The IEEE 802.11a standardization group has selected Orthogonal Frequency Division Multiplexing (OFDM) as the basis for the new 5 GHz standard, targeting a range of data rates from 6 up to 54 Mbps. Coded OFDM (COFDM) is a channel coding and modulation scheme which mitigates the adverse effects of fading by using wideband multicarrier modulation combined with time interleaving and a convolutional error correcting code. A guard interval is inserted at the transition between successive symbols to absorb the intersymbol interference created by the time domain spread of the mobile radio channel. The decoding process is performed using differential demodulation in conjunction with a hard decision Viterbi decoder. The simulation results show a COFDM system capable of indoor environment communications in the presence of known multipath and noise conditions. The results obtained also show that the COFDM configuration is immune to Doppler shift of 5 to 15 Hz.