Multicarrier wireless systems: Enabling studies on carrier frequency and channel estimation.

摘要

Multicarrier (MC) systems are being proposed and tested for wireless data transmission in applications such as broadband wireless networking and digital broadcasting of audio and television. In contrast to wireline signals, wireless communication signals are modulated to available parts of the spectrum called radio frequency (RF). For a free running receiver local oscillator, the MC system performance rapidly deteriorates when the carrier frequency offset between transmitter and receiver is greater than a small fraction of the intercarrier spacing. It is necessary to estimate carrier offset at the receiver and compensate. For power loading and coding in MC communications, multipath channel information must also be estimated.; This dissertation introduces a blind carrier offset estimation which exploits the structure information of OFDM signals. The performance of the estimation algorithm is analyzed as a function of system parameters. The development of a practical software radio testbed which emulates short range multipath channels such as those found in indoor environments is described. The performance of such a system is analyzed under different scenarios and the system sensitivity to perturbations is examined via experimental studies. The extension of this work to a fading resistant multiple access method is discussed next. Specifically we analyze the uplink system performance loss due to carrier offset in these systems. The analysis is supported using simulations. Finally, two blind channel estimators for multicarrier systems are presented.