Channel interpolation for LTE uplink systems with high mobility using Slepian sequences

Single Carrier Frequency Division Multiple Access (SC-FDMA) has been adopted for 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) uplink communication since it combines the low peak to average power ratio feature of single-carrier transmission systems with the multipath resistance and flexible frequency allocation of orthogonal frequency-division multiple access (OFDMA). Unfortunately, SC-FDMA transmission over time-varyingmultipath fading channels for very high speed environments the subcarrier orthogonality is destroyed giving rise to intercarrier interference (ICI) due to channel variation within an SC-FDMA symbol. This paper is, therefore, focused on the use of timedomain channel interpolator for LTE uplink systems in large Doppler spread scenarios to improve channel tracking performance. The resulting interpolation algorithm is based on the discrete prolate spheroidal wave functions (DPSWF) which is particularly well suited to represent the rapidly time-varying fading channel due to optimum finite time and frequency support feature. The variations of the channel taps are tracked first by a Kalman filter in time domain during training symbols. Then, a DPSWF based channel interpolator is applied to recover the time variation of channel taps between training symbols within two consecutive slots in a single subframe. The performance of the proposed interpolator is compared with a polynomial interpolator whose order is adjusted adaptively to achieve the best fit under particular user mobilities. Moreover, the analytical mean square error (MSE) performance of DPSWF is derived and compared with the simulations. The results show that the DPSWF represents the time-varying fading channel very effectively and the proposed algorithm has excellent channel estimation performance in high SNR even with a very small number of channel interpolation parameters employed in the algorithm. © 2013 Elsevier B.V. All rights reserved. ✩ This work is supported in part by the Turkish Scientific and Technical Research Institute (TUBITAK) under Grant 108E054. Part of the results of this paperwere presented at the IEEE-GLOBECOM,Miami, USA, December 6–10, 2010. ∗ Corresponding author. Tel.: +90 212 4737070x17877; fax: +90 212 4737064. E-mail addresses: [email protected], [email protected] (B. Karakaya), [email protected] (H.A. Çırpan), [email protected] (H. Arslan). URLs: http://www2.itu.edu.tr/∼cirpanh/ (H.A. Çırpan), http://wcsp.eng.usf.edu (H. Arslan). 1 Tel.: +90 212 285 6729; fax: +90 212 285 3565. 2 Tel.: +1 813 974 3940; fax: +1 813 974 5250. 1874-4907/$ – see front matter© 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.phycom.2013.11.005