Multiple-input multiple-output (MIMO) integrated sensing and communication (ISAC) is a promising solution to achieve higher performances of dual functionalities. However, the existing cell-free/bistatic MIMO ISAC networks struggle to meet strict requirements for data-intensive communication and accuracy-sensitive radar positioning. To further achieve joint enhancement, we propose a novel network where two ISAC transmitters cooperatively perform communication and target positioning, fully leveraging the advantages of cell-free/bistatic principles in communication/radar systems, referred to as bistatic-enhancement MIMO ISAC. An optimization for joint beamforming design is established to maximize the sum data rate for communication users and minimize a novel positioning-enhanced Cramér-Rao lower bound (CRB) that evaluates positioning accuracy under their corresponding requirements. The established problem is solved under two schemes: cooperative block-level and symbol-level beamforming. The solution under the former scheme is derived by an iterative behavior. Under the latter one, inter-user interference is eliminated and co-channel interference is exploited for useful signal enhancement. The problem can be converted into a convex semi-definite problem (SDP) based on semi-definite relaxation (SDR). Experimental results substantiate the effectiveness of the proposed algorithms. More importantly, the proposed bistatic-enhancement network improves positioning accuracy by 32.5% ∼ 47.5% over the conventional bistatic-site one under different schemes.

Uncrewed aerial vehicle (UAV)-enabled ISAC systems have received widespread attention due to the high mobility of UAVs with good line-of-sight (LoS) paths to ensure communication and sensing performance. However, the existing works on UAV-enabled ISAC mainly focus on optimizing communication performance (e.g., sum rate) and sensing performance, resulting in excessive energy consumption and reducing the flight endurance of the UAV. Motivated by this, we draw a trade-off between such performance and energy consumption to achieve robust and efficient UAV-enabled ISAC. In this work, we aim to maximize the worst-case energy efficiency in UAV-enabled ISAC by jointly designing the beamforming and the UAV trajectory, while ensuring the UAV energy constraints and the ISAC performance. Nevertheless, solving this problem is non-trivial due to its non-convex nature, and the high coupling of the transmit beamforming vectors and the UAV dynamics adds an additional layer of complexity. To effectively address this non-convex issue, we alternately optimize the transmit communication and sense beamforming, as well as the UAV dynamic variables to obtain a sub-optimal solution, and the algorithm complexity is lower than the existing algorithms. Experimental results show a trade-off between energy efficiency and average sum rate. Furthermore, they indicate the superiority of the proposed algorithm to enhance energy efficiency by significantly reducing energy consumption without causing excessive sum rate loss.

On-demand edge computing power networks with both stationary fog nodes co-located with cellular base stations (CFNs) and mobile fog nodes mounted on vehicles (VFNs) provide promising solutions for coping with high spatio-temporal, compute-intensive, and latency-sensitive applications. Joint scheduling and resource allocation in such a network is challenging due to the trade-off between quality of service (QoS) and energy consumption, limited onboard capacity of IoT devices and fog nodes, and urban obstructions that impede line-of-sight links. To address these issues, this work envisions a network assisted by reconfigurable intelligent surface (RIS) with a multi-layer scheme. The computation tasks are offloaded from IoT devices to VFNs and further to CFNs based on the computational demand and latency requirements, and the RIS assists with wireless communication on both links. We jointly optimized the allocation of the subcarriers, the power, the offloading task bits, the time slot, and the RIS beamforming vectors under the constraints of task input bits and computing capability, to minimize the average energy consumption. To address the non-convex issue, we first decompose it into three sub-problems, and then alternately optimize these sub-problems by adopting successive convex approximation (SCA) where a locally optimal solution can be obtained. Simulation results demonstrate the superiority of the proposed offloading strategy where RIS with a multi-layer scheme is introduced in the on-demand edge computing power networks. Also, the effectiveness, feasibility, scalability, and adaptability of the designed algorithm are verified.

Unmanned aerial vehicle (UAV)-enabled massive multiple-input-multiple-output (MIMO) integrated sensing and communication (ISAC) is an emerging platform to perform communication and sensing efficiently and flexibly. However, the existing works barely consider the radar probing tasks and neglect the benefits of the dedicated sensing signal. In this paper, we focus on joint optimizations in radar probing tasks, and a novel indicator is introduced, namely radar probing error. Two optimizations in radar probing tasks are established: i) joint transmit beamforming design for large-scale regional radar probing and communication task; ii) joint transmit beamforming and UAV trajectory design for communication enhancement and radar probing task. For the former task, we adopt both communication and novel sensing precoders to further support the MIMO radar. A semidefinite relaxation is utilized to relax the original non-convex problem, which is proven to be tight. For the latter task, we adopt block coordinate descent to alternately optimize the precoders and UAV trajectory where the fractional programming approach and successive convex approximation are further adopted. Experiment results testify the validation of the proposed methods for radar probing tasks in UAV-enabled MIMO ISAC. Moreover, results show the fundamental trade-off between the dual functions and reveal the effectiveness of the introduced sensing precoder.

Integrated sensing and communications (ISAC) is emerging as one of the six application scenarios for future wireless networks. Characterizing the Pareto boundary is an urgent issue in multiple-input multiple-output (MIMO) ISAC systems. The lack of unified sensing metrics and the neglect of the instantaneous worst-case sensing requirement in the existing works present challenges to this issue. In this paper, we propose a more universal and operable theoretical limit analysis framework where the high-signal-to-noise ratio (SNR) channel capacity is characterized under instantaneous covariance mismatch constraint. We use the covariance mismatch that implies the distance to optimal covariance as the sensing metric. The optimal covariance can be computed by optimizing any key sensing metric. An MIMO ISAC Pareto boundary can be obtained by computing channel capacity under fine-grained sensing thresholds, below which the mismatch must be constrained. In the experiments, three radar modes are considered, and the results show that different radar modes affect capacity performance and a trade-off exists between communication and sensing. In addition, pure communication capacity is the upper bound of the communication capacity in ISAC. Moreover, capacity under instantaneous constraint approaches that under average one in pure MIMO communications when signal length approaches infinity.

Random mixing and circularly shifting for augmenting the training set are used to improve the separation effect of deep neural network (DNN)-based monaural singing voice separation (MSVS). However, these manual methods are based on unrealistic assumptions that two sources in the mixture are independent of each other, which limits the separation effect. This paper proposes a data augmentation method based on variational autoencoder (VAE) and generative adversarial network (GAN), which is called as VAE-GAN. The VAE models the observed spectra of sources (vocal and music) separately and reconstructs new spectra from the latent space. The GAN's discriminator is introduced to measure the correlation between the latent variables of the vocal and music generated by the VAE probability encoder. This adversarial mechanism in VAE's latent space could learn the synthetic likelihood and ultimately decode high quality spectra samples, which further improves the separation effect of general MSVS networks.