Hybrid analog and digital beamforming (HBF) has been regarded as a key technology for future millimeter wave (mmWave) communication systems due to its ability to obtain a good tradeoff between achievable beamforming gain and hardware cost. In this paper, we investigate the channel estimation and hybrid precoding for mmWave MIMO systems with deep learning. We adopt the hierarchical codebook based algorithm for channel estimation as it requires limited number of pilot transmissions, and enhance its performance by proposing a new codebook design algorithm based on manifold optimization (MO). With the estimated channel state information (CSI) as the input, we develop a robust HBF network (HBF-Net) by applying convolutional layers and attention mechanism, which can be trained to generate a robust HBF matrix targeting at spectral efficiency maximization with imperfect CSI. To further improve the performance, we propose a joint channel estimation and HBF optimization network (CE-HBF-Net). Considering that the adaptively selected HBF vectors in the hierarchical codebook based channel estimation are different for different channel realizations, we skillfully propose an index assign-and-input method to efficiently feed such information to the CE-HBF-Net to reduce the network input dimensions and make the network trainable. Furthermore, we propose a signal self-attention mechanism to enable the CE-HBF-Net to intelligently assign larger weight coefficients to those signals that contribute more to channel estimation. Simulation results show that the well-designed HBF-Net and CE-HBF-Net outperform the conventional HBF algorithms with imperfect channel and exhibit robustness to mismatches between offline training and online deployment stages. INDEX TERMSMillimeter wave (mmWave), channel estimation, hierarchical codebook, manifold optimization (MO), hybrid beamforming (HBF), deep learning (DL), attention mechanism
With the development of computer network technology and communication technology and the popularization of intelligent devices, the application of IT technology and Internet and Internet of things technology has brought profound changes in the field of education. Students are no longer satisfied with the learning in the classroom. The rich way of learning broadens the access to knowledge. The combination of online learning and fragmented learning and other learning methods at anytime and anywhere has become the main way to acquire knowledge. People's reading environment and reading habits have been hitherto unknown changes, only a short while ago, teaching resources also appeared to undergo some column transformation, presenting a new form of traditional textbooks and digital publishing: the integration of development, integration and development of printing paper with rich media resources, integration and development of paper materials and digital resources.
With the development of computer network technology and communication technology and the popularization of intelligent devices, the application of IT technology and Internet and Internet of things technology has brought profound changes in the field of education. Students are no longer satisfied with the learning in the classroom. The rich way of learning broadens the access to knowledge. The combination of online learning and fragmented learning and other learning methods at anytime and anywhere has become the main way to acquire knowledge. People's reading environment and reading habits have been hitherto unknown changes, only a short while ago, teaching resources also appeared to undergo some column transformation, presenting a new form of traditional textbooks and digital publishing: the integration of development, integration and development of printing paper with rich media resources, integration and development of paper materials and digital resources. The Three Stages of the Development Form of Teaching Material Resources The first generation of material resources with the characteristics of mediaTextbooks usually mean what we call textbooks or textbooks, that is, the traditional paper media. The earliest textbook resources construction also includes auxiliary materials, such as synchronous manuals, classroom exercises, experimental guidance materials, exercises and other paper materials. The way of teaching material resources is usually arranged in a simple linear way according to knowledge points [1]. The advantage is to pay attention to the presentation of learning contents, which is more suitable for learners to learn mechanically from easy to difficult.With the advent of computer, projector and other equipment, network open course program (OCW) to carry out teaching resources from the print form gradually to digital media form, compared with the print media, teaching resources has become an auxiliary material, combined with classroom teaching, knowledge in form than before has changed. Therefore, the value of teaching material resources of digital media is basically attached to the teaching material itself, centered on the content of the textbook itself, and the organization form of teaching material resources is not organized according to learners' learning angle, ignoring the needs of learners [2]. The content of this kind of teaching material is relatively simple, only the one-way communication between teachers, teachers and students can not communicate and communicate in time after class, which is closed. The second generation of teaching resources in network media featuresThe emergence of Internet technology has caused great changes in the field of education, with the OCW movement in depth, especially the construction of the national excellent course starting in 2003, the media materials in the internet. The development of technology promotes the transformation of teaching material resources. A video based open education resource is deeply loved by learners. Its manifestations are div...
Smart education represents the trend of education development and reform in the future, and is a new education pattern generated by deep fusion of education and information technology. Smart learning is the necessary means to realize smart education. This paper states the smart learning activities under Internet + education mainly from the connotation, learning environment and learning space of smart learning.
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