Publications

2024

1. ICNC ’24

   Fast Frequency-Direction Mapping Design for Data Communication With True-Time-Delay Array Architecture

   Ding Zhao, Ibrahim Pehlivan , Aditya Wadaskar , and 1 more author

   In International Conference on Computing, Networking and Communications (ICNC) , 2024

   Abs HTML

   In recent times, beamforming architectures utilizing True-Time-Delay arrays have gained significant interest in the field of wide-band data communication due to their abilities to generate frequency-dependent responses with great flexibility. This paper proposes a new heuristic fast algorithm with the goal of beamforming signals to different directions in different sub-bands. The proposed algorithm not only achieves better spectral efficiency than existing heuristic algorithms, but also significantly reduces computation time compared to optimizationbased methods.

2023

1. GLOBECOM ’23

   Structured Two-Stage True-Time-Delay Array Code book Design for Multi-User Data Communication

   Aditya Wadaskar , Ding Zhao, Ibrahim Pehlivan , and 1 more author

   In IEEE Global Communications Conference (GLOBECOM) , 2023

   Abs HTML

   Wideband millimeter-wave and terahertz (THz) systems can facilitate simultaneous data communication with multiple spatially separated users. It is desirable to orthogonalize users across sub-bands by deploying frequency-dependent beams with a sub-band-specific spatial response. True-Time-Delay (TTD) antenna arrays are a promising wide band architecture to implement sub-band-specific dispersion of beams across space using a single radio frequency (RF) chain. This paper proposes a structured design of analog TTD codebooks to generate beams that exhibit quantized sub-band-to-angle mapping. We introduce a structured Staircase TTD codebook and analyze the frequency-spatial behaviour of the resulting beam patterns. We develop the closed-form two-stage design of the proposed codebook to achieve the desired sub-band-specific beams and evaluate their performance in multi-user communication networks.

2022

1. WCNC ’22

   Joint transmit and reflective beamforming for IRS-assisted integrated sensing and communication

   Xianxin Song , Ding Zhao, Haocheng Hua , and 3 more authors

   In IEEE Wireless Communications and Networking Conference (WCNC) , 2022

   Abs HTML

   This paper studies an intelligent reflecting surface (IRS)-assisted integrated sensing and communication (ISAC) system, in which one IRS with a uniform linear array (ULA) is deployed to not only assist the wireless communication from a multi-antenna base station (BS) to a single-antenna communication user (CU), but also create virtual line-of-sight (LoS) links for sensing potential targets at areas with LoS links blocked. We consider that the BS transmits combined information and sensing signals for ISAC. Under this setup, we jointly optimize the transmit information and sensing beamforming at the BS and the reflective beamforming at the IRS, to maximize the IRS’s minimum beampattern gain towards the desired sensing angles, subject to the minimum signal-to-noise ratio (SNR) requirement at the CU and the maximum transmit power constraint at the BS. Although the formulated SNR-constrained beampattern gain maximization problem is non-convex and difficult to solve, we present an efficient algorithm to obtain a high-quality solution by using the techniques of alternating optimization and semi-definite relaxation (SDR). Numerical results show that the proposed joint beamforming design achieves improved sensing performance while ensuring the communication requirement as compared to benchmarks without such joint optimization. It is also shown that the use of dedicated sensing beams is beneficial in enhancing the performance for IRS-assisted ISAC.