This paper exploits the line-of-sight (LoS) and dominant single-bounce non line-of-sight (NLoS) propagation characteristics of millimeter wave (mmWave)/terahertz (THz) channels to facilitate joint position and velocity vector sensing in integrated sensing and communication (ISAC) systems. We develop a signal model that captures how the velocity vector is reflected in the angular velocity of the LoS path and the Doppler shifts of these paths, and characterize the fundamental accuracy limits through the position error bound (PEB) and the velocity error bound (VEB). Next, we propose a two-stage estimation framework to approach these bounds in practice. In the first stage, we propose a space-alternating generalized expectationmaximization (SAGE)-maximum likelihood (ML) algorithm to detect propagation paths and estimate the associated channel parameters. In the second stage, the estimated channel parameters are mapped to sensing parameters, and a weighted least squares (WLS) based fusion algorithm is developed to recover the velocity vector by adaptively combining the radial and tangential velocity information provided by the LoS path with the additional radial velocity information extracted from the dominant single-bounce NLoS paths. Furthermore, a weighted non-linear least squares (WNLS) refinement is proposed to adjust estimated sensing parameters. Simulation results demonstrate that the performance asymptotically approaches the corresponding bounds at medium to high signal-to-noise ratios (SNRs), and the proposed algorithms outperform the baselines in both position and velocity estimation accuracy.
Dong-Qi Luo, Qiang Li, Fan Jiang et al.· IEEE Transactions on Wireles...· 0 citations
Integrated sensing and communication (ISAC) under a cell-free (CF) architecture enables seamless connectivity and sensing coverage by allowing multiple distributed access points (APs) to jointly serve users and detect targets, thereby mitigating cell-edge effects and enhancing spatial diversity. However, wideband CF-ISAC also suffers from frequency-selective fading and strong inter-AP interference. To address these challenges, we investigate a simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS)-assisted ISAC framework, which extends full-space coverage and mitigates multiplicative fading and blockage effects. A joint optimization strategy is developed to maximize the weighted ISAC joint rate by jointly optimizing bandwidth and power allocation, receive beamforming, and active STAR-RIS beamforming. To tackle the non-convexity caused by variable coupling and intricate constraints, an efficient alternating optimization algorithm is developed. The original problem is decomposed into several subproblems: first, a closed-form solution for receive beamforming is derived; next, the resource allocation semi-analytical solutions are obtained via Karush-Kuhn-Tucker (KKT) conditions. Subsequently, the active STAR-RIS coefficients are optimized by capitalizing on fractional programming and majorization-minimization (MM) techniques. Finally, simulation results reveal that the proposed scheme achieves a 20.34% weighted ISAC joint-rate gain over the passive scheme, validating its effectiveness in wideband CF-ISAC systems.
Xintong Zhou, Feng Ke, Xiu-Yin Zhang et al.· IEEE Transactions on Communi...· 0 citations
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