Mutual Information Maximization via Joint Power Allocation in Integrated Sensing and Communications System

In this paper, we focus on the power allocation of Integrated Sensing and Communication(ISAC) with orthogonal frequency division multiplexing(OFDM) waveform. In order to improve the spectrum utilization efficiency in ISAC, we propose a design scheme based on spectrum sharing, that is,to maximize the mutual information(MI) of radar sensing while ensuring certain communication rate and transmission power constraints. In the proposed scheme, three cases are considered for the scattering off the target due to the communication signals,as negligible signal, beneficial signal, and interference signal to radar sensing, respectively, thus requiring three power allocation schemes. However,the corresponding power allocation schemes are nonconvex and their closed-form solutions are unavailable as a consequence. Motivated by this, alternating optimization(AO), sequence convex programming(SCP) and Lagrange multiplier are individually combined for three suboptimal solutions corresponding with three power allocation schemes. By combining the three algorithms, we transform the non-convex problem which is difficult to deal with into a convex problem which is easy to solve and obtain the suboptimal solution of the corresponding optimization problem. Numerical results show that, compared with the allocation results of the existing algorithms, the proposed joint design algorithm significantly improves the radar performance.

New Delay Doppler Communication Paradigm in 6G Era:A Survey of Orthogonal Time Frequency Space(OTFS)

In the 6G era,Space-Air-Ground Integrated Network(SAGIN)are anticipated to deliver global coverage,necessitating support for a diverse array of emerging applications in high-mobility,hostile environments.Under such conditions,conventional orthogonal frequency division multiplexing(OFDM)modulation,widely employed in cellular and Wi-Fi communication systems,experiences performance degradation due to significant Doppler shifts.To overcome this obstacle,a novel twodimensional(2D)modulation approach,namely orthogonal time frequency space(OTFS),has emerged as a key enabler for future high-mobility use cases.Distinctively,OTFS modulates information within the delay-Doppler(DD)domain,as opposed to the timefrequency(TF)domain utilized by OFDM.This offers advantages such as Doppler and delay resilience,reduced signaling latency,a lower peak-to-average ratio(PAPR),and a reduced-complexity implementation.Recent studies further indicate that the direct interplay between information and the physical world in the DD domain positions OTFS as a promising waveform for achieving integrated sensing and communications(ISAC).In this article,we present an in-depth review of OTFS technology in the context of the 6G era,encompassing fundamentals,recent advancements,and future directions.Our objective is to provide a helpful resource for researchers engaged in the field of OTFS.

A Brief Introduction on Joint Radar and Communication Systems

Joint radar and communication(JRC)technology is gradually becoming an essential approach to alleviating spectral congestion.Radar and communications systems were designed with common spectral and hardware resources to reduce size,improve performance,reduce cost,and decongest the spectrum.Various approaches have been proposed to achieve the coexistence of radar and communication systems.This paper mainly focuses on the research directions of radar communication coexistence(RCC)and dual-function radar communication systems(DFRC)in JRC technology.We summarize and analyze the existing research problems in the JRC era.According to the characteristics and advantages of JRC technology,we highlight several potentials in military and commercial applications.

Science communication with science fiction movies

“It is not as easy as it looks,”Holden Thorp,Science’s chief editor,commented at the end of 2021,when explaining new research findings of the COVID-19 pandemic to the public had encountered great difficulties.1 As a matter of fact,science communication has never been easy because serious scientific knowledge is prone to be boring rather than interesting.There is only one atypical medium for science communication,i.e.,the science fiction movie(sci-fi movie for short),that has a huge amount of fans.

通信感知一体化的信息理论极限

无线感知已成为通信产业界广泛公认的、下一代无线网络中的原生能力.通信感知一体化将通信和感知功能集成在同一个无线系统中,能够提高资源利用率,减少基础设施开销,并增强通信和感知各自的性能.通信与感知间的性能折衷是通感一体化的关键基础理论问题之一.本文首先指出通感性能极限和可达性能边界是研究通感性能折衷的重要手段,然后从容量–失真理论、基于均方误差的通感性能边界理论、基于感知等效速率的通感性能边界理论,以及面向目标检测的通感性能边界理论4个方面出发,对相关的当前研究进展进行了详细总结与分析.文中指出通感性能折衷可进一步划分为确定–随机折衷和子空间折衷,并详细讨论了现有研究工作中与之相关的结论.在此基础上,讨论了基于实际的5G NR协议与帧结构的通感性能边界理论.最后,本文对通感一体化的信息理论极限中仍需关注和进一步研究的开放问题进行了总结.