Abstract
This paper proposes a robust transceiver design against the effect of channel state information (CSI) estimation error to optimize precoded uplink (UL) multi-user multiple-input multiple-output (MU-MIMO) transmission in limited feedback system under the consideration of the least-square technique on CSI estimation. To improve this limited feedback precoding, the constrained minimum variance (MV) approach with quadratic form to realize the computationally-efficient optimization problem, advantageously invoking the characteristics of the CSI estimation error, is proposed to suppress the effect of CSI estimation error, multiple user interference and noise. According to the Lagrange multiplier method on this MV approach, the deterministic function to resist uncertain CSI can be obtained to optimize design of the precoder and adaptive matrices jointly. With these optimum adaptive and precoder matrices, an optimum robust weighting matrix can be obtained to facilitate the user-wise detection in precoded UL MU-MIMO system. Performance analysis shows that the proposed robust weighting matrix is an unbiased design and it also can regularize the diagonal loading factor technique, and the detection performance of the proposed robust transceiver design can be predicted simplistically by applying our derived signal-to-interference-plus-noise ratio formulation. Computer simulations are conducted to confirm the efficacy of the proposed design in both perfect and imperfect CSI estimation.
Highlights
An uplink (UL) multi-user multiple-input multiple-output (MU-MIMO) system [1,2] is an important wireless communication technique for the third generation partnership project (3GPP) long-term evolution (LTE) [3,4,5], where multiple users transmit data to a base station (BS)
We have presented a robust transceiver design with joint suppression of effect of multiple user interference (MUI), noise and channel state information (CSI) estimation error in UL MU-MIMO precoding for limited feedback system under considering LS technique on CSI estimation
Since robust transceiver design is difficult to be tractable, the optimization problem with considering design of the precoder and adaptive matrices on the constrained minimum variance (MV) approach subjects to constraint the rejection of CSI estimation error developed in the use-wise detection
Summary
An uplink (UL) multi-user multiple-input multiple-output (MU-MIMO) system [1,2] is an important wireless communication technique for the third generation partnership project (3GPP) long-term evolution (LTE) [3,4,5], where multiple users (i.e., mobile stations) transmit data to a base station (BS). Precoding with the entire CSI feedback in [6] is impractical because the receiver sends all of the CSI to users via a limited feedback channel [9] This conventional detection structure [6] performs terribly due to the involvement of an inaccurate SVD [10] suffered from the effect of uncertain CSI and noise. The robust design in the limited feedback system has more complicated optimization problem due to the involvement of the non-linear characteristic in SVD [14,15] These motivate us to develop a computationallyefficient convex optimization problem to optimize jointly the design of the adaptive and precoder matrices for the robust transceiver design as follows. With the optimum adaptive and precoder matrices, an optimum robust column-wise weighting matrix can be obtained to facilitate the user-wise detection in precoded UL MU-MIMO transmission for limited feedback system. E{·} is an expectation operation, tr (·) is a trace operation and || · ||F represents Frobenius norm
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