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Techniques of Transmitting Beamforming to Control the Generated Weights

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Author(s): Imen Sfaihi | Noureddine Hamdi | Ammar Bouallegue

Journal: International Journal of Communications, Network and System Sciences
ISSN 1913-3715

Volume: 03;
Issue: 07;
Start page: 612;
Date: 2010;
Original page

Keywords: MISO | Beamforming | Limited Feedback | CSI | SSC | FSSC | RW-FSSC | SSC-Schmidt Algorithm

ABSTRACT
In this paper, we consider the limited feedback Transmitting Beamforming for MISO systems. In conventional techniques, all vectors of a large codebook (CB), used for the feedback of the quantized channel state information (CSI), are broadcasted to all users, in a guard period which is followed by data burst periods. Instead of transmitting a high number of codevectors, we thought to divide the CB into several sub-codebooks (SC) and the broadcast would be based on the switch between them. Accordingly, a good performance can be provided while minimizing the required feedback channel capacity applying some proposed techniques such as “the switched Sub Codebook (SSC)” and “the Fairness SSC (FSSC)”. To minimize the quantization error, we propose two other techniques. The first is based on making Transmit SSC vectors controlled by a rotation weight (RW) to obtain almost a zero correlation between the SSC vectors used for the selected spatial channels. The second is based on introducing “the Schmidt algorithm” to construct an orthonormal weights using the generated weights. These two proposed techniques increase the probability of the selection of the worst case user on his best codevector to make zero the angle between his couple codevector and channel response. To analyze and validate the performance of these proposed techniques, simulation results are presented.
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