Browsing by Author "Chao, Chi-Liang"

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A Bit Allocation Scheme for MIMO Equal Gain Precoders
(2010)
Chao, Chi-Liang
;
Tsai, Shang-Ho
;
Hsu, Terng-Yin
;
資訊工程學系
;
電機工程學系
We consider the design of the equal gain precoder in flat-fading and limited feedback multiple-input multiple-output (MIMO) systems. The advantage of the equal gain precoder based on the scalar quantization (SQ) is that it is easier to encode the feedback information and no need to construct codebook in advance. In the sort of precoder, the bit allocation methods will dominate the system performance. In this paper, we explore an efficient bit allocation algorithm for the scalar quantized equal gain precoder. The proposed bit allocation scheme can improve the performance of the straightforward scalar quantized equal gain precoder. Compared to the optimal bit allocation scheme with exhaustive search, the proposed algorithm greatly reduces the computational complexity while the performance is near to the optimal scheme.
A DIFFERENTIAL FEEDBACK SCHEME FOR EQUAL GAIN TRANSMISSION IN TEMPORALLY CORRELATED CHANNELS
(2012-01-01)
Chao, Chi-Liang
;
Tsai, Shang-Ho
;
Hsu, Terng-Yin
;
資訊工程學系
;
電機工程學系
The adoption of equal gain transmission (EGT) in MIMO systems can greatly reduce the computational complexity and the design effort of power amplifier. In a temporally correlated channel environment, the channel varies slowly and so does the corresponding beamforming vector. If the slowly varying channel condition can be taken into consideration while designing the feedback schemes of EGT, the computational complexity and feedback overhead of EGT are expected to be further diminished dramatically. In this paper, we propose a differential feedback scheme (DFS) with two algorithms to further improve the performance in EGT. Simulation results show the advantages of the proposed DFS in terms of the feedback overhead and the system performance.
Bit Allocation Schemes for MIMO Equal Gain Precoding
(2011-05-01)
Chao, Chi-Liang
;
Tsai, Shang-Ho
;
Hsu, Terng-Yin
;
資訊工程學系
;
電機工程學系
We design equal gain precoders with scalar quantization in MIMO systems with limited feedback, which do not require the predefined codebook. In such precoders, bit allocation can be used to quantize the precoding vector/matrix to further improve the system performance. There are two conventional bit allocation schemes. One is the uniform bit allocation and the other is the optimal bit allocation obtained by using exhaustive search. The uniform bit allocation is simple but turns out to have obvious performance degradation. On the other hand, the exhaustive search method leads to the optimal performance. However, its computational complexity is extremely high and may be somewhat impractical to be realized. In this paper, we propose two bit allocation schemes for the MIMO equal gain precoder with scalar quantization. Both of the proposed methods are with low complexity and their performance is close to the optimal scheme. Consequently, the proposed bit allocations provide good trade-off between performance and complexity.