3D mmWave ISAC network with optimal power allocation for UAV relaying system

Abstract

Integrated sensing and communication (ISAC) is a promising technology for next-generation communication systems, allowing simultaneous data communication and sensing. To achieve highly accurate positioning in sensing system, use of high frequency spectrum of electromagnetic wave such as mmWave is needed. However, since high frequency spectrum suffers severe propagation loss, the coverage of both sensing and communication are narrow. Furthermore, in the presence of blockages, ISAC does not guarantee accurate positioning due to the lack of echo signals reflected from targets. To address this issue, we study a downlink ISAC system with an unmanned aerial vehicle (UAV) relay to expand the sensing and communication coverage by generating the blockage-free detour paths. In this UAV-assisted downlink ISAC system, we aim to transmit information while maintaining high target positioning accuracy by optimizing transmit power allocation. With moving target objects in a three-dimensional (3D) environment, this optimization problem becomes non-trivial due to highly complicated relationship of moving object position. To alleviate this complexity, we derive an approximated state transition model of 3D object and thereby formulate two strictly convex optimization problems that guarantees a unique optimal power allocation solution. Two optimization problems aimed to maximize the information transmission rate of each UAV relay network and maximize the accuracy of the position estimation of the UAV relay network. Numerical results corroborate that the proposed power allocation technique achieves both high positioning accuracy and data transmission rates in an ISAC network involving UAV relays. Furthermore, by comparing the numerical results of both optimization problems, we observe the trade-off relationship between sensing and communication performances.