Metamaterials are artificial structures with the ability to efficiently control light‐field, attracting intensive attention in the past few decades. People have studied the working principles, design strategies, and fabrication methods of metamaterials, making this field cross and combine with many disciplines, including physics, material science, electronics, and chemistry. In recent years, with the rapid development of high‐efficiency and multifunctional metasurfaces, which are a two‐dimensional version of metamaterials, great efforts have been made to push this material to practical applications. In particular, the introduction of artificial intelligent (AI) algorithms enables metamaterials‐based photonic devices that exhibit excellent performances and intelligent functionalities. In this review, we first introduce the basic concepts, working principles, design methods, and applications of metamaterials, and then focus on the rapidly developing metamaterials research combined with AI algorithms. Finally, we conclude this review with personal perspectives on the current problems and future directions of metamaterials research and developments.
We study the power allocation for incremental redundancy (IR) hybrid automatic repeat request (HARQ) in block fading channel where causal channel state information is known at both the transmitter and the receiver. In IR-HARQ, the traffic is assigned into consecutive transmission rounds, and at each round, the instantaneous mutual information that is required for successful decoding is upper bounded by the data rate that is to be delivered. We propose an HARQ power allocation method that maximizes the average of incremental mutual information at each round, and its throughput quickly converges to the ergodic capacity as the number of retransmissions increases. The numerical results show that the proposed power allocation method achieves almost the full channel capacity with moderate average transmission delay and that it maintains good throughput under stringent delay requirement.Index Terms-HARQ, throughput, incremental redundancy, power allocation, channel state information.
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