Indoor propagation channel appears differently to ultra-wideband (UWB) systems than it does to narrowband systems. UWB signals have very high temporal resolution ability and this implies a frequency-selective channel with rich multipath in practice. To capture the signal energy spread over a multipath environment, a Rake receiver consisting of multiple parallel correlators is used. Performance of UWB systems employing Rake receivers is highly dependent on synchronization and the channel estimation. The channel parameters are the attenuations and delays incurred by the UWB signal along the propagation paths. Maximum-Likelihood (ML) and orthogonal subspace (OS) based methods are considered to estimate the parameters for IEEE 802.15.3a standard indoor multipath channel model. Analyzing the limitations and benefits of these methods, a new combined approach is proposed to improve channel parameter estimation.