DocumentCode :
3501178
Title :
Efficient Transmission Schemes for Multiuser MIMO-OFDM Downlink Systems in Time-Varying Channels
Author :
Wang, Hongmei ; Xu, Xibin ; Zhao, Ming ; Wu, Weiling ; Yao, Yan
Author_Institution :
Nat. Lab. for Inf. Sci. & Technol., Tsinghua Univ., Beijing
fYear :
2008
fDate :
11-14 May 2008
Firstpage :
812
Lastpage :
816
Abstract :
The performance of multiuser MIMO-OFDM downlink systems with block diagonalization (BD) depends on the accuracy of the channel state information (CSI) available at the transmitter (CSIT) to a great extent. In time-varying channels, the CSIT is always outdated due to an inherent time delay between the uplink channel estimation and the downlink data transmission in TDD systems. This will lead to drastic degradation in system capacity. In this paper, based on the analysis of the effect of the outdated CSIT on multiuser MIMO- OFDM downlink systems with BD method, two linear processing methods, BD with user selection at the transmitter and total MMSE decoder at the receiver (TBDUS-RTMMSE) and BD at the transmitter and partial MMSE decoder at the receiver (TBD-RPMMSE), are proposed to mitigate the effect. To fulfill them, a new pilot-sending architecture is introduced. Analysis and simulation results show that the two proposed methods can effectively reduce the impairment of the outdated CSIT and improve the system sum capacity in suitable time delay regions of the CSIT.
Keywords :
MIMO communication; OFDM modulation; channel capacity; channel coding; channel estimation; decoding; delays; least mean squares methods; multiuser channels; time-varying channels; TDD system; block diagonalization; channel capacity; channel state information; downlink data transmission; least mean squares method decoder; linear processing method; multiuser MIMO-OFDM downlink system; pilot-sending architecture; time delay; time-varying channel; uplink channel estimation; Channel estimation; Channel state information; Data communication; Decoding; Degradation; Delay effects; Downlink; OFDM; Time-varying channels; Transmitters;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Vehicular Technology Conference, 2008. VTC Spring 2008. IEEE
Conference_Location :
Singapore
ISSN :
1550-2252
Print_ISBN :
978-1-4244-1644-8
Electronic_ISBN :
1550-2252
Type :
conf
DOI :
10.1109/VETECS.2008.177
Filename :
4525733
Link To Document :
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