Filtreler

2002 - 20042
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Ayarlar

Yazar: Panayırcı, Erdal × Konu: Diversity ×

Arama Sonuçları

Listeleniyor 1 - 2 / 2
  • Küçük Resim
    Yayın
    Channel estimation for space-time block coded OFDM systems in the presence of multipath fading
    (IEEE, 2002) Panayırcı, Erdal; Çırpan, Hakan Ali
    In this paper, a computationally efficient, non-data-aided maximum a posterlori(MAP) channel estimation algorithm is proposed for orthogonal frequency division multiplexing (OFDM) systems with transmitter diversity using space-time block coding. The Alamouti's transmit diversity scheme with two transmit antennas is employed here and generalized for OFDM systems. The algorithm requires a convenient representation of the discrete multipath fading channel based on the Karhunen-Loeve orthogonal expansion and estimates the complex channel parameters of each subcarriers iteratively using the Expectation Maximization(EM) method, which converges to the true MAP estimation of the unknown channel. Ananalytical expression is derived for the Modified Cramer-Rao. lower bound of the proposed MAP channel estimator. The performance is presented in terms of the mean-square error for a system employing QPS signaling.
  • Küçük Resim
    Yayın
    Adaptive Kalman receiver for OFDM systems with transmit diversity in mobile wireless channels
    (Walter De Gruyter GMBH, 2004-12) Şen, Adnan; Çırpan, Hakan Ali; Panayırcı, Erdal
    A new joint channel tracking and symbol detection scheme is proposed in this paper for pilot symbol assisted transmit diversity OFDM systems by exploiting the correlation of the adjacent subchannels. Modelling the channel frequency response of every subcarrier corresponding to each transmit antenna as random processes, we employ Kalman filters for both channel tracking and subsequent decoding with diversity gain. Among different stochastic models, the AR model is adopted herein for channel dynamics. Since the proposed adaptive receiver uses two Kalman filters to track the variations of the channel and subsequently to detect the information symbols, they are combined in the coupled receiver structure. Finally the performance of the proposed method is studied through experimental results.