Low complexity power-efficient waveform design for RIS-aided ISAC
File(s)
Author(s)
Gautam, Prabhat Raj
McCann, Julie
Type
Journal Article
Abstract
We consider an integrated sensing and communication (ISAC) system in which a base station (BS) communicates with several users with the help of a reconfigurable intelligent surface (RIS), sensing targets at the same time. We design a power-efficient ISAC scheme that limits communication and sensing power by maintaining a minimum required signal-to-interference-and-noise ratio (SINR) at the communication user and a minimum required received sensing SINR. The sensing signal is implemented by minimizing the difference between the beampattern of the ISAC signal and the desired beampattern. Unlike the existing state-of-the-art power-efficient ISAC waveforms, the communication signal is also included in the design of the sensing signal to limit its impact on sensing performance. We obtain the communication signal by designing a precoder, that meets the minimum SINR constraint with minimum power, jointly with the passive beamforming at the RIS. To this end, we propose two separate algorithms, viz., one based on alternating optimization, which alternately optimizes passive beamforming and transmit precoder, and the second one based on manifold optimization in which we optimize passive beamforming first, followed by the optimization of the transmit precoder. A low-complexity algorithm based on the first-order optimization condition is employed to produce a sensing signal, which is later projected onto the null space of the communication channel to nullify its effect on the communication performance. The power of the dedicated sensing signal is adjusted to meet the individual sensing SINR constraints at the receiver, which helps reduce the total transmit power. Simulations demonstrate that the proposed algorithms achieve improved communication and sensing performance, with up to a 2 dB reduction in transmit communication power and up to a 4 dB reduction in normalized beampattern along angles outside the target location, compared to the existing state-of-the-art solution.
Date Issued
2026-06-26
Date Acceptance
2026-06-14
Citation
IEEE Transactions on Vehicular Technology, 2026
ISSN
0018-9545
Publisher
Institute of Electrical and Electronics Engineers
Journal / Book Title
IEEE Transactions on Vehicular Technology
Copyright Statement
Copyright © 2026 IEEE. This is the author’s accepted manuscript made available under a CC-BY licence in accordance with Imperial’s Research Publications Open Access policy (www.imperial.ac.uk/oa-policy)
License URL
Publication Status
Published online
Date Publish Online
2026-06-26