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We compare three approaches for modeling the ultra-wideband (UWB) indoor channel delay profile, including the one adopted by the IEEE 802.15.3a Task Group. We do this using a large database we collected (and have reported on previously) spanning numerous indoor environments. Where appropriate, we recalculate model parameters so as to be compatible with the database. We test the models against the database and against each other by computing certain statistical 'attributes' of the ensemble of channel delay profiles, e.g., the probability distribution, across the ensemble, of the root-meansquare (rms) delay spread. We show that each of the modeling approaches yields reasonable agreement with the database for most or all of the attributes tested, and we discuss the relative merits of the three approaches.

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Abstract-A constrained minimum mean square error (CMMSE)-RAKE receiver for multipath fading channels is developed by extending the CMMSE receiver for flat fading channels. Based on the observation that interpath interference causes a bias of the channel estimator in [8], a receiver that can remove such a bias is proposed, plus a closed-form expression of the bit-error rate of the receiver is derived. Computer simulation is used to demonstrate that the proposed receiver can outperform existing RAKE receivers.Index Terms-Frequency-selective fading channels, minimum mean square error (MMSE), multiuser detection.