| This thesis concerns the channel estimation and compensation in wireless communications. In general the base station (BS) has much more computational and power resources than the mobile station (MS). At the same time, the forward link channel (FLC) normally has higher data rate than the reverse link channel (RLC) and thus requires more complicated equalizers. Yet currently, almost all the FLC estimation and compensation tasks are shouldered by the MS. This dissertation puts forward a bent pipe feedback scheme which enables both the FLC and RLC to be estimated and compensated at the BS. Compared to training based channel estimation techniques, this bent pipe scheme also has the advantage of saving bandwidth.;At first the bent pipe scheme with a simple rate changer inserted between the FLC and RLC is introduced. The identifiability conditions and identification algorithms are developed for single input single output channels. This feedback scheme is further extended to multi-input multi-output channels. A more informative rate changer is presented to improve the data utilization efficiency, showing a much improved performance. The idea of bent pipe feedback scheme is then applied to systems with infinite impulse response (IIR) controller and orthogonal frequency division multiplexing (OFDM) systems. The corresponding identification algorithms are developed. |
