| The fifth generation mobile communication network(5G)has been deployed worldwide,and the International Telecommunication Union(ITU)defines its three major application scenarios are enhanced mobile broadband(eMBB),massive machine type communications(mMTC)and ultra-reliable and low-latency communications(uRLLC).There is no doubt that 5G networks can dramatically increase data rates,flexibly support a variety of devices,and accommodate more network connections.However,ITU has predicted in its research that 5G networks will not be able to meet the requirements of future communications after 2030.In this context,researchers are gradually shifting their focus to the sixth generation mobile communication network(6G),which will meet more stringent requirements than 5G,such as ultra-high data rates,spectral efficiency,global coverage,and massive connectivity.Therefore,it is critical to develop sustainable and innovative technologies that will allow future wireless network capacity to increase at a moderately manageable budget,complexity and power consumption.On the other hand,time-varying wireless channels are a major challenge for achieving ultra-reliable wireless communications due to the mobility of users.In recent years,the rise of intelligent reflecting surfaces(IRS)technology has provided new solutions.IRS is regarded as an important enabler for realizing intelligent radio environments,which makes the traditional time-varying wireless environment configurable and tunable to better solve problems such as channel fading and signal interference.Inspired by this,this paper further investigates multiple IRS-assisted wireless communication systems based on an in-depth investigation of research works on IRS,and tries to combine integrated sensing and communications(ISAC)technology to study the potential of IRS in integrated sensing and communications scenarios.The main content and innovation points of this paper are as follows:(1)Based on the in-depth investigation,we systematically summarize the research work on IRS and its technology development status,emphasize the background and significance of the selected topic of this paper.Subsequently,we introduce the theoretical basis of IRS technology in detail,including the technology concepts,working principle,typical features,research directions,communication models and application scenarios.(2)The multiple IRS-assisted wireless communication system is studied,and a new working pattern of IRS similar to the domino game is proposed to solve the problem of serious attenuation of high-frequency signals in future wireless communication.The upper bound on the ergodic capacity and the outage probability of this system under this pattern are analyzed in a more general Nakagami-m fading channel,and give closed-form expressions involving only elementary functions for both that are easy to analyze.To the best of our knowledge,this is the first attempt to conduct IRS-assisted wireless communication performance study in Nakagami-m fading channels.(3)Attempt to apply IRS to integrated sensing and communications scenarios.After introducing the basic concept,current research status,evaluation metrics and application scenarios of integrated sensing and communications,an IRS-assisted integrated sensing and communications is proposed to improve the communication and sensing performance in non-line-of-sight scenarios.First,we analyze the the signal models for radar sensing and communication,and give a low-complexity design scheme of IRS phase shift matrix.Based on this,we estimate the distance and velocity information of the target with the help of the maximum likelihood estimation algorithm,and calculate the data transmission rate. |
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