Conference Paper

A Pilot Design Technique for Single-Carrier Transmission over Fast Fading Relay Channels

Dept. of Electron. & Electr. Eng., Pohang Univ. of Sci. & Technol., Pohang
DOI: 10.1109/GLOCOM.2008.ECP.903 Conference: Global Telecommunications Conference, 2008. IEEE GLOBECOM 2008. IEEE
Source: IEEE Xplore

ABSTRACT Relay-assisted space-time block code (STBC) and space-frequency block code (SFBC) for single carrier frequency-domain equalization (SC-FDE) were presented. They achieve spatial diversity over fading relay channels under the assumption of perfect channel state information (CSI). In this paper, we propose a pilot position selection/detection technique for channel estimation of those systems. Unlike the conventional block-type channel estimation techniques, the proposed scheme superimposes pilots on data-carrying tones whose positions are selected to minimize the distortion of original signals. Without additional pilot overhead, the proposed technique can track the CSI even when the mobile equipment speed is high. The corresponding destination structure and frequency domain equalization are also presented, where the pilot positions are blindly detected and the distorted data symbols are iteratively reconstructed. Simulation results show that the proposed method gives better BER performance than the block-type channel estimation for the distributed SFBC (D-SFBC) SC-FDE over fast fading relay channels, without the loss of spectral efficiency.

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    ABSTRACT: Space-time block coded (STBC) single carrier (SC) transmission was extended in a distributed fashion for practical implementation of user cooperation. However, STBC was designed under the assumption that the channel is static over the duration of a space-time codeword. Thus, the distributed STBC SC system suffers from the time selectivity of wireless fading channels. To achieve a reliable performance over fast fading channels, we propose a distributed space-frequency block coded (D-SFBC) SC transmission. This paper analytically compares the performance of these two distributed SC transmissions over fast fading environment. For evaluation of mean square error (MSE) over fast fading channels, we present a channel model that captures the time-varying nature of wireless channels. It gives an insight into the characteristics of inter-carrier interference and simplifies the evaluation of MSE. Using this model, it is proven that the D-SFBC SC transmission outperforms the D-STBC SC transmission when there exists a severe Doppler spread. Simulation results are also provided to validate our analysis and to compare two distributed single carrier transmission schemes.
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    ABSTRACT: Peak-to-average power ratio (PAPR) regrowth after clipping is one disadvantage of space-frequency block coded orthogonal frequency-division multiplexing (SFBC-OFDM). In this letter, we propose an effective PAPR reduction technique of SFBC-OFDM for multinode cooperative transmission. To reduce PAPR at the source (mobile equipment), the relay applies SFBC encoding, which enables the source to transmit clipped single-input single-output (SISO)-OFDM signals without any increase of PAPR. Simulation results show that the clipped signals of proposed scheme are effectively recovered, and the proposed scheme achieves the diversity of SFBC without the complexity of multiple antennas at the source.
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