Conference Paper
Equal Gain MIMO Beamforming in the RF Domain for OFDMWLAN Systems.
DOI: 10.1007/9783642166440_13 Conference: Mobile Lightweight Wireless Systems  Second International ICST Conference, MOBILIGHT 2010, Barcelona, Spain, May 1012, 2010, Revised Selected Papers
Source: DBLP
 Citations (13)
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Conference Paper: MIMO transmit beamforming under uniform elemental power constraint
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ABSTRACT: We consider multiinput multioutput (MIMO) transmit beamforming under the uniform elemental power constraint. This is a nonconvex optimization problem, and it is usually difficult to find the optimal transmit beamformer. First, we show that for the multiinput singleoutput (MISO) case, the optimal solution has a closedform expression. Then we propose a cyclic algorithm for the MIMO case which uses the closed form MISO optimal solution iteratively. The cyclic algorithm has a low computational complexity and is locally convergent under mild conditions. Moreover, we consider finiterate feedback methods needed for transmit beamforming. We propose a novel vector quantization method, where the codebook is constructed under the uniform elemental power constraint and the method is referred as VQUEP. Numerical examples are provided to demonstrate the effectiveness of our proposed transmit beamformer designs and the finiterate feedback technique.Signal Processing Advances in Wireless Communications, 2007. SPAWC 2007. IEEE 8th Workshop on; 07/2007 
Conference Paper: Analog Antenna Combining for Maximum Capacity Under OFDM Transmissions.
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ABSTRACT: In this paper, we study beamforming schemes for a novel MIMO transceiver, which performs adaptive signal combining in the radiofrequency domain. Assuming perfect channel knowledge at both the transmit and receive sides, we consider the problem of selecting the transmit and receive RF beamformers that maximize the capacity (MaxCAP criterion) of the system under orthogonal frequency division multiplexing (OFDM) transmissions. This problem is nonconvex and has no closedform solution, therefore the maximum capacity beamformers are found using a gradient search algorithm. Furthermore, it is shown in the paper that, for low signaltonoise ratios (SNR), the MaxCAP criterion is equivalent to maximizing the received SNR (MaxSNR criterion). However, for moderate and high SNRs, the maximum capacity beamformers sacrifice part of the received SNR in order to improve the worst subcarriers and, in this way, they increase the overall capacity of the multicarrier channel. Finally, by means of numerical examples we show that the MaxCAP criterion significantly outperforms the MaxSNR criterion in terms of bit error rate and outage probability.Proceedings of IEEE International Conference on Communications, ICC 2009, Dresden, Germany, 1418 June 2009; 01/2009  01/2009; IEEE Computer Society.
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