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This paper focuses on the feedback scheme for downlink Multi-User Multiple-Input Multiple-Output (MU-MIMO) transmission with linear precoding. When the maximum transmission rank per user is limited to one, the multiple-antenna receiver uses a weight vector to transform MIMO channel matrix into an equivalent Multiple-Input Single-Output (MISO) channel vector. Then a Channel Directional Index (CDI)...
This paper proposes a differential codebook-based method to reduce the feedback overhead for closed-loop MIMO-OFDM systems. With the assumed multimode transmit precoding, both the number of data streams (rank) and the index of precoding matrix are fed back to the transmitter at each sub-band. By exploiting the channel correlation in frequency domain, an enhanced differential codebook (a subset of...
In this paper, we study the channel estimation problem for time division multiplex amplify-and-forward (AF) relay channels. Both the source and the destination and also the in-between relay node comprise multiple antennas, and there are spatial fading correlations in each hop. We first derive a linear minimum mean square error (LMMSE) channel estimator from a simple scenario where there are no correlations...
The transmitter side precoding shows excellent performance for multiuser multiple input multiple output (MIMO) wireless systems. However, joint transmitter and receiver design might achieve further improvement. The optimum precoding and decoding matrices can be solved iteratively. In this paper, we propose a modified joint iterative algorithm, based on minimum mean square error (MMSE) criterion in...
This paper proposes a codebook based limited feedback zero-forcing(ZF) precoding scheme for multi-user multiple-input multiple-output (MIMO) downlink channels. In such system, each user needs to calculate a channel directional index (CDI) and a channel quality indicator (CQI), feedback them to the base station (BS). BS selects the set of active users, and calculates transmit beams through zero forcing...
Detection is one of the key technologies in multiple-input multiple-output system. In this paper we propose a new tree searching scheme which is flexible in the tradeoff between performance and complexity. Sorted QR decomposition based on minimum mean square error (MMSE) criteria is applied as a preprocessing to make the channel easier for tree searching and Fano bias, which is adjustable to achieve...
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