DocumentCode :
456835
Title :
Promising feedback methods for transmit beamforming in broadband mobile OFDM
Author :
Thomas, Timothy A. ; Baum, Kevin L. ; Sartori, Philippe
Author_Institution :
Commun. Syst. Res. Lab., Motorola Labs, Schaumburg, IL
Volume :
3
fYear :
2006
fDate :
3-6 April 2006
Firstpage :
1239
Lastpage :
1244
Abstract :
This paper details three methods for closed-loop operation in the downlink of a broadband mobile OFDM system: uplink sounding, codebook feedback, and direct channel feedback (DCFB). Uplink sounding is intended for TDD systems and works by the base translating the uplink channel estimates into downlink channel estimates. DCFB is a means of obtaining full channel knowledge in either FDD or TDD systems. In DCFB, the mobile replaces normal transmitted symbols with a DCFB waveform constructed from downlink channel estimates to multiple base antennas. Another feedback method for TDD or FDD is codebook feedback where the mobile chooses a best transmit weight out of a codebook of 2B vectors and then signals this weight back to the base. To track the frequency-selective channel, multiple codebook vectors are sent back corresponding to different parts of the band. Simulation results show that uplink sounding is the best method for obtaining channel information for transmit beamforming, but sounding is only effective in TDD systems. For FDD, DCFB is more flexible, computationally efficient (at the mobile), and effective than codebook feedback for broadband transmit beamforming at the base
Keywords :
OFDM modulation; antenna arrays; broadband networks; channel estimation; codes; feedback; mobile radio; time division multiplexing; 2B vectors; FDD system; TDD system; broadband mobile OFDM system; closed-loop operation; codebook feedback; direct channel feedback; downlink channel estimation; feedback methods; frequency-selective channel; multiple base antennas; multiple codebook vectors; transmit beamforming; transmit weight; uplink channel estimation; uplink sounding; Array signal processing; Base stations; Downlink; Feedback; Frequency conversion; Hardware; Mobile antennas; Multiaccess communication; OFDM; Transmitting antennas;
fLanguage :
English
Publisher :
ieee
Conference_Titel :
Wireless Communications and Networking Conference, 2006. WCNC 2006. IEEE
Conference_Location :
Las Vegas, NV
ISSN :
1525-3511
Print_ISBN :
1-4244-0269-7
Electronic_ISBN :
1525-3511
Type :
conf
DOI :
10.1109/WCNC.2006.1696463
Filename :
1696463
Link To Document :
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