Conference Proceeding

A Spectral efficient Relay-Based Transmit Diversity Technique for SC-FDE without Cyclic Prefix

Dept. of Electron. & Electr. Eng., Pohang Univ. of Sci. & Technol. (POSTECH), Pohang
06/2008; DOI:10.1109/ICC.2008.812 In proceeding of: Communications, 2008. ICC '08. IEEE International Conference on
Source: IEEE Xplore

ABSTRACT This paper proposes a relay-based transmit diversity technique for single carrier frequency-domain equalization (SC-FDE). The proposed system achieves spatial diversity over fading channels in a distribution fashion without cyclic prefix (CP), which increases spectral efficiency of conventional relay- based systems. The destruction of channel cyclicity due to the lack of CP is recovered at the input of relay and destination. In order to obtain spatial diversity, the transmit sequence of relay is efficiently generated in time domain, realizing space-frequency block code (SFBC). Corresponding destination structure using FDE, timing synchronization, and highly accurate channel estimation for the proposed system are also presented. Simulation results show that the proposed system approaches the lower bound of full-CP system.

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    ABSTRACT: This paper proposes spectral efficient relay-assisted transmit diversity techniques, i.e., space-time and space-frequency block codes (STBC/SFBC), for single carrier frequency-domain equalization (SC-FDE). The proposed systems achieve spatial diversity over frequency selective channels in a distributed fashion without cyclic prefix (CP), which increases spectral efficiency of conventional relay-assisted systems. In practical mobile applications, the CP-less distributed STBC (D-STBC) SC-FDE suffers from the time selectivity of wireless fading channels, resulting in a deviation from the basic assumption of Alamouti codeword. In order to obtain a reliable performance over doubly selective channels, the CP-less D-SFBC SC-FDE and its efficient implementation are presented. Further, the performance of these two distributed SC transmissions is analytically compared over fast fading (i.e., time selective) environments. For evaluation of mean square error over fast fading channels, we present a channel model that captures the time-varying nature of wireless channels. It is shown through analysis that the CP-less DSFBC SC-FDE outperforms the CP-less D-STBC SC-FDE when there exists a severe Doppler spread. Timing synchronization and highly accurate channel estimation of the proposed systems are also addressed for practical implementations. Simulation results show that the proposed systems approach the lower bound of full-CP systems, thus increasing the spectral efficiency.
    IEEE Transactions on Communications 03/2010; · 1.75 Impact Factor
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    ABSTRACT: This paper develops an amplify-and-forward relaying technique for multiuser wireless cooperative networks under frequency-selective block-fading. Single-carrier frequency division multiple-access with frequency-domain equalization technique is employed at both the relay and destination to combat the inter-block and inter-symbol interference caused by multipath propagation. With the assumption that the full channel state information (CSI) is available at the destination, the relay only knows the uplink channels while no CSI is available at the sources, two power allocation schemes are obtained: (i) to minimize the total transmit power at the relay while maintaining the signal-to-interference-plus-noise ratio (SINR) for each user at the destination above a certain level, and (ii) to maximize the worst SINR among all the users subject to a constraint on total relay transmit power. Analysis and simulation results are provided to illustrate the effectiveness of the proposed schemes.
    Proceedings of the Global Communications Conference, 2009. GLOBECOM 2009, Honolulu, Hawaii, USA, 30 November - 4 December 2009; 01/2009
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    [show abstract] [hide abstract]
    ABSTRACT: This paper develops an amplify-and-forward relaying scheme for multiuser wireless cooperative networks under frequency-selective block-fading. Single-carrier frequency division multiple-access with frequency-domain equalization technique is employed at both the relay and destination to combat the inter-block and inter-symbol interference caused by multipath propagation. With the assumption that the full channel state information (CSI) is available at the destination, the relay only knows the uplink channels while no CSI is available at the sources, two power allocation schemes are developed for the relay: (i) to minimize the total transmit power at the relay while maintaining the signal-to-interference-plus-noise ratio (SINR) for each user at the destination above a certain level, and (ii) to maximize the worst SINR among all the users subject to a constraint on total relay power. In the first problem, it is shown that SINR adaptation is needed not only to guarantee a feasible solution but also to significantly reduce the transmit power at the relay for certain channel conditions. In the second problem, a flexible multi-level water-filling scheme is developed, which can be easily modified to adapt to the different channel conditions as well as different quality-of-service provision strategies.
    IEEE Transactions on Communications 12/2010; · 1.75 Impact Factor

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Ui-Kun Kwon