Enhancing closed-loop wireless systems through efficient feedback reconstruction

doi:10.1109/TVT.2007.900506

Enhancing closed-loop wireless systems through efficient feedback reconstruction

2007-09-01

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DOI：10.1109/TVT.2007.900506

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The closed-loop transmit diversity technique is used to improve the performance of the downlink channel in multiple-input multiple-output (MIMO) communication systems. The wideband code-division multiple-access standard endorsed by the Third Generation Partnership Project (3GPP) adopts a downlink closed-loop scheme based on partial channel state information (CSI) known as mode 1. The information is fed back from the mobile unit to the base station through a low-rate uncoded feedback bit stream. In this paper, several reconstruction techniques are introduced to improve the performance of mode 1 of 3GPP in the presence of feedback error by taking advantage of the redundancy available in the bit stream of the CSI. We propose a number of algorithms for the reconstruction of beamforming weights at the base station with the constraint of a constant transmit power. The performance is examined within a simulated 3GPP framework. It is demonstrated that the proposed algorithms have substantial gain over the conventional method for low, moderate, and high mobile speeds. It is also shown that the proposed algorithms can substitute the antenna weight verification process done at the mobile unit in many cases. The proposed approach is applicable to other feedback schemes as well.

Keywords:

antenna weight verification (AV)

channel feedback

channel state information (CSI)

closed-loop transmit diversity

downlink communication

frequency-division-duplex (FDD) wideband code-division multiple access (WCDMA)

joint source-channel coding

mode 1 of the Third Generation Partnership Project (3GPP)

Enhancing closed-loop wireless systems through efficient feedback reconstruction

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