Fifth generation wireless networks are expected to utilize wide bandwidths available at millimeter wave (mmWave) frequencies for enhancing system throughput. However, the unfavorable channel conditions of mmWave links...
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Fifth generation wireless networks are expected to utilize wide bandwidths available at millimeter wave (mmWave) frequencies for enhancing system throughput. However, the unfavorable channel conditions of mmWave links, such as, higher path loss and attenuation due to atmospheric gases or water vapor, hinder reliable communications. To compensate for these severe losses, it is essential to have a multitude of antennas to generate sharp and strong beams for directional transmission. In this paper, we consider mmWave systems using uniform planar array (UPA) antennas, which effectively place more antennas on a 2-D grid. A hybrid beamforming setup is also considered to generate beams by combining a multitude of antennas using only a few radio frequency chains. We focus on designing a set of transmit beamformers generating beams adapted to the directional characteristics of mmWave links assuming a UPA and hybrid beamforming. We first define ideal beam patterns for UPA structures. Each beamformer is constructed to minimize the mean squared error from the corresponding ideal beam pattern. Simulation results verify that the proposed codebooks enhance beamforming reliability and data rate in mmWave systems.
This paper proposes a hybrid codebook design algorithm and a distributed codeword selection criterion for multiple-input multiple-output (MIMO) amplify-and-forward (AF) relaying system with power allocation and precod...
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ISBN:
(纸本)9781424456383
This paper proposes a hybrid codebook design algorithm and a distributed codeword selection criterion for multiple-input multiple-output (MIMO) amplify-and-forward (AF) relaying system with power allocation and precoding. The proposed codebook design algorithm exploits a modified LIoyd algorithm and converges to a locally optimal codebook. Closed form solution for power allocation problem is derived in order to maximize the channel capacity. Based on the codebook design algorithm, we further propose a codeword selection criterion which allows base station and relay to independently choose optimal codewords. The criterion effectively decreases the feedback delay in MIMO AF relaying system. Simulation results show that the proposed scheme achieves elegant performance in terms of ergodic capacity with very limited bits of feedback.
Classified vector quantisation (CVQ) of images is a vector quantisation-based coding method for preserving perceptual features while retaining simple vector quantiser distortion measures during codebookdesign and enc...
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Classified vector quantisation (CVQ) of images is a vector quantisation-based coding method for preserving perceptual features while retaining simple vector quantiser distortion measures during codebookdesign and encoding process. In the paper, a new algorithm for CVQ codebookdesign the ‘classified nearest neighbour clustering’ (CNNC) algorith, is presented. The CNNC algorithm is based on a classification process of small image blocks and on an agglomerative clustering algorithm, and is used to design simultaneously M codebooks for M different classes, defined for a CVQ system. The CNNC algorithm can be used with squared error and weighted squared error distortion measures employing one of two optimisation criteria which are presented and tested in the paper. In addition, fast search algorithm is presented aimed at reducing computational efforts encountered during codebookdesign. The CNNC algorithm is shown to provide a systematic and effective method for CVQ codebookdesign making CVQ more feasible and easy to implement.
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