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Summary: IEEE TRANSACTIONS ON WIRELESS COMMUNICATIONS, VOL. ?, NO. ?, JUNE ? 1
Performance of Optimal Beamforming with
Partial Channel Knowledge
Shimi Shilo, Anthony J. Weiss, Fellow, IEEE, and Amir Averbuch
Abstract
Multiple antenna techniques are used to enhance wireless links and therefore have been studied
extensively. Many practical systems that differ from ideal schemes have been discussed in the literature.
One example is a system that lacks precise channel information at the transmitter. We evaluate analyt-
ically the performance of a multiple input multiple output (MIMO) technique that uses partial channel
knowledge. Specifically, we analyze a scheme with M transmit antennas and N receive antennas,
employing eigenbeamforming at the transmitter and MRC at the receiver. We assume that only partial
channel matrix is known to the transmitter, specifically only P out of N rows of the channel matrix
are known. We derive the optimal beamformer for a single stream transmission case and show that it is
the singular vector of the known channel submatrix. We show that the diversity order of a transmission
scheme where such a precoder is used is MP + N - P and further show that increasing the value of
P by one increases the diversity order by M - 1. We also derive the array gain for this scheme. All
the results are supported by simulations.
Index Terms
MIMO systems, Beamforming, Partial Channel Knowledge, WiMAX, LTE.
I. INTRODUCTION
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