The combination of communication and sensing is envisioned as a novel feature in the forthcoming sixth-generation (6G) wireless communication. The conventional approach to the joint sensing and communication (JSAC) system is utilizing one base station (BS) as both a sensing transmitter and a sensing receiver, which is known as monostatic sensing. However, the resulting self-interference issue requires additional hardware promotion to achieve full-duplexing. To overcome this issue, in this paper, we focus on cooperative sensing where the transmitter and receivers are non-co-located, which includes the bistatic and multistatic sensing. Specifically, the system model of cooperative sensing based on mobile networks is established. To demonstrate the feasibility of cooperative sensing, the bistatic radar cross section (RCS) is provided. As for the sensing method, a refined orthogonal matching pursuit (R-OMP) method is proposed to estimate the channel parameters and data fusion is also provided to derive the objects’ positions and velocities. Considering the non-negligible interference in the cooperative JSAC networks, we also discuss interference management in this paper. Simulation results show that the proposed cooperative sensing system improves the position and velocity estimation accuracy by over 20% when compared with monostatic sensing. The preliminary experiment results also verify the feasibility of the proposed system.

In this article, an efficient over-the-air (OTA) calibration and pattern estimation method under the midfield (MF) condition for the fifth-generation (5G) millimeter-wave (mmWave) large-scale arrays is proposed. A new transformation and revision algorithm is developed to calibrate the antenna array fast and accurate. Meanwhile, the time consumed in the accurate beamforming pattern estimation is reduced significantly. The proposed method requires a much smaller size anechoic chamber, a fixed probe antenna, and a vector network analyzer (VNA). The effectiveness is proven with the detailed theoretical analysis and experimented with a 64-element phased array in the 26 GHz band. The calibrated root-mean-square (rms) errors of the phase and magnitude are about 1.8°/0.4 dB. In addition, the proposed calibration and pattern estimation method is tremendously cost-effective and time-saving with similar accuracy as the far-field test method.

In this article, we analyze the signal-to-interference ratio (SIR) coverage probability of a multi-cell downlink system with random traffic arrivals. Based on a theoretical model, in which the base stations (BSs) and devices are deployed as independent Poisson point processes (PPPs), we first present the sufficient and necessary conditions of the ε-stable region for the queueing system. Then, by taking into account the impact of spatially queueing interactions among BSs, we focus on the steady status of the queues and introduce a two-queue-length approximated model for the system. Specifically, in the studied new model, the BSs are separated into two sets in the steady state: the long-queue BS set and the short-queue BS set. The locations of the former are modeled by a Neyman-Scott process and those of the latter are modeled as a residual hole process. By applying the first-order statistic approximation, we further approximate the hole process by a homogeneous PPP with the same density. To model the deployment of the BSs precisely, the related parameters in the approximated model are fitted. Using tools from stochastic geometry and queueing theory, we derive the SIR coverage probability in the steady state. An iterative algorithm is proposed to calculate the active probability of the BSs. To reduce the computational complexity, Beta distribution is applied to approximate the probability density function of the service rate in each iteration of the algorithm. Finally, the effect of the fitting parameters and the accuracy of our analysis are presented via Monte Carlo simulations.

Integrated sensing and communication (ISAC) has caught a great deal of interest and attention since it was identified as a key usage scenario of 6G mobile communications. Whereas cooperative ISAC, taking advantage of the large-scale cellular infrastructure, in addition to the benefit of eliminating full duplex transceivers, is favored by mobile operators. This paper starts with channel modeling and key technologies at the link level, including synchronization, beam management, and advanced sensing algorithms, of cooperative ISAC systems. From a network perspective, it provides optimal base station deployment, receiving node(s) selection, and network interference management to improve system performance. Then, cooperative ISAC enhanced by novel multiple-input multiple-output (MIMO) antenna technologies is introduced. Finally, prototype designs of cooperative ISAC systems at both Sub-7 GHz and millimeter wave bands are presented, respectively. Experimental results in an outdoor environment have verified that with only 3. 5% of the communication capacity cost and 200 MHz bandwidth, a range estimation accuracy of 0.2 m can be achieved within the 500 m range.

Towards the sixth generation (6G) wireless communications, multiple access is a potential technology to achieve thousand times of traffic capacity enhancement comparing with 5G. This paper investigates the feasible signal-to-interference-plus-noise-ratio (SINR) region for the multi-cell downlink and uplink non-orthogonal multiple access (NOMA) systems. Within a cell, the signals of different users are multiplexed on a channel with different power levels and successive interference cancellation is applied at the receivers to decode the signals. For the downlink, based on Perron-Frobenius Theory, we first derive a necessary and sufficient condition for an SINR vector to be feasible under a fixed decoding order. Then, a closed-form expression for the feasible SINR region is given by the union of the SINR regions under all possible decoding orders. Following a similar idea, the expression of the feasible SINR region for the uplink is also derived. Furthermore, the duality between the multi-cell downlink and uplink NOMA systems is explored. It is proved that the two systems have same feasible SINR region under dual channels. Finally, we propose an efficient algorithm to approximate the SINR region boundary. Simulation results are provided to validate the efficiency of the algorithm and compare the performance with orthogonal multiple access scheme.