Browsing by Author "Hottinen, Ari"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Maximum Likelihood Multipath Channel Parameter Estimation in CDMA Systems
    (1998-03-01) Sengupta, Chaitali; Hottinen, Ari; Cavallaro, Joseph R.; Aazhang, Behnaam; Center for Multimedia Communication
    The problem addressed in this paper is the estimation of the channel parameters in a Code Division Multiple Access(CDMA) communication system, in the presence of multipath effects. Maximum likelihood estimation of these parameters has been investigated in the past with the main drawback being the complexity of the multi-dimensional algorithms. The algorithm presented in this paper elegantly decomposes the multiuser problem into a series of single user problems. The algorithm first estimates a composite channel impulse response of each user and then extracts the channel parameters of all the paths of each user from the channel impulse response. We evaluate the performance of the algorithm through simulation studies.
  • Thumbnail Image
    Item
    Performance of Iterative Multiuser Decoding and Channel Estimation in WCDMA Systems
    (2000-05-20) Bhashyam, Srikrishna; Hottinen, Ari; Center for Multimedia Communications (http://cmc.rice.edu/)
    This paper studies the performance of iterative multiuser decoding, interference cancellation, and channel estimation techniques applicable to third generation WCDMA systems. The concept uses a posteriori probabilities of code symbols to enhance detection, decoding and channel estimation in an iterative fashion. Performance is analyzed in a multi-path channel with simulations. It is seen that the proposed concept combats multiuser interference effectively and performs almost as well as single user systems.
  • Thumbnail Image
    Item
    Soft weighted STTD for W-CDMA
    (1999-09-20) Hottinen, Ari; Wichman, Risto; Rajan, Dinesh; Center for Multimedia Communications (http://cmc.rice.edu/)
    The transmit diversity concept adopted for teh FDD mode of the third generation WCDMA system in 3G standardization has an open-loop and a closed-loop mode. The open-loop mode applies a space-time block for two transmit antennas. The closed-loop mode has two sub-modes, which both utilize downloink measurements at terminal and subsequent feedback in controlling the phase and/or gain transmit weights in the transmit antennas in order to approximate matched beamforming. These concepts are summarized in this paper for two transmit antennas and they are compared to a soft-weighted transmit diversity concept, proposed here, in which the relative transmit powers of the space-time encoded signals are controlled by feedback signaling. This leasds to a robust feeback mode in which the terminal is simplified in the sense that it does not require dedicated reference/pilot symbols, or weight verification, as opposed to the current feedback modes.