483 research outputs found
Sequential estimation of time-varying multipath channel for MIMO-OFDM systems
No full textComunicació presentada al IEEE International Symposium on Information Theory (ISIT '08), celebrat a Toronto (Ontario, Canadà) els dies 6, 7, 8, 9, 10 i 11 de juliol de 2008, organitzat per l'Institute of Electrical and Electronics Engineers (IEEE).In this paper, we introduce a pilot-aided multipath channel estimator for Multiple-Input Multiple-Output (MIMO) Orthogonal Frequency Division Multiplexing (OFDM) systems. Typical estimation algorithms assume the number of multipath components and delays to be known and constant, while their/namplitudes may vary in time. In this work, we focus on the more realistic assumption that also the number of channel taps is unknown and time-varying. The estimation problem arising from this assumption is solved using Random Set Theory (RST), which is a probability theory of finite sets. Due to the lack of a closed form of the optimal filter, a Rao-Blackwellized Particle Filter (RBPF) implementation of the channel estimator is derived. Simulation results demonstrate the estimator effectiveness.The work of Ezio Biglieri was supported by the Spanish/nMinistery of Education and Science under Project TEC2006-/n01428/TCM, and by the STREP project No. IST-026905/n(MASCOT) within the 6th framework program of the European/nCommission.The work of Ezio Biglieri was supported by the Spanish/nMinistery of Education and Science under Project TEC2006-/n01428/TCM, and by the STREP project No. IST-026905/n(MASCOT) within the 6th framework program of the European/nCommission
Impact of channel-state information on coded transmission over fading channels with diversity reception
No full textBrowse Journals & Magazines > Communications, IEEE Transact ...> Volume:47 Issue:9 Prev | Back to Results | Next » Impact of channel-state information on coded transmission over fading channels with diversity reception .This paper appears in: Communications, IEEE Transactions on Date of Publication: Sep 1999 Author(s): Taricco, Giorgio Dipt. di Elettronica, Politecnico di Torino, Italy Biglieri, Ezio M.; Caire, Giuseppe Volume: 47 , Issue: 9 Page(s): 1284 - 1287 Product Type: Journals & Magazines 1 1 789660 searchabstract .Abstract We study the synergy between coded modulation and antenna-diversity reception on channels affected by slow Rician fading. Specifically, we assess the impact of channel-state information (CSI) on error probability. We show that with a good coding and constant envelope modulations (for example, phase-shift keying) scheme the loss in performance when CSI is not available is moderate (around 1.5 dB). Moreover, as the diversity order grows, the channel tends to become Gaussia
Space-time decoding with imperfect channel estimation
No full textUnder the assumption of a frequency-flat slow Rayleigh fading channel with multiple transmit and receive antennas, we examine the effects of imperfect estimation of the channel parameters on error probability when known pilot symbols are transmitted among information data. Three different receivers are considered. The first one derives an estimate of the channel [by using either a maximum-likelihood (ML) or a minimum mean square error (MMSE) criterion], and then uses this estimate in the same metric that would be applied if the channel were perfectly known. The second receiver derives again an estimate of the channel, but uses the ML metric conditioned on the channel estimate. Our last receiver simultaneously processes the pilot and data symbols received. Simulation results are exhibited, showing that only a relatively small percentage of the transmitted frame need be allocated to pilot symbols in order to experience an acceptable degradation of error probability due to imperfect channel knowledge. Algorithms for the recursive calculation of the decision metric of the last two receivers are also developed for application to sequential decoding of trellis space-time codes
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