Fluid antenna (FA) is an emerging technology in recent years to switch physical locations of antennas in a predetermined small space. This paper proposes a reconfigurable intelligent surfaces (RIS)-cooperative framework with FA-assisted non-orthogonal multiple access (NOMA) system, namely FA-RIS-NOMA. Targeting multi-interference scenarios in urban environments, the considered system incorporates a base station (BS) equipped with a conventional antenna and users each equipped with an FA. Additionally, the RIS is utilized to forward signals between BS and users blocked by obstacles. The non-line-of-sight multipath fading characteristics of the RIS-assisted link are modeled as a Nakagami-mchannel. To overcome the multiuser interference and improve the system performance, we develop the NOMA technique for resource allocation. Meanwhile, to reduce the signal processing complexity at the receiver, a group optimization greedy detection method is proposed. To evaluate the system’s reliability, the outage probability for each user is analyzed by using the copula function. This method enables the derivation of the cumulative distribution and probability density functions for the equivalent user-side channel, from which closed-form outage probability expressions are obtained. Numerical results demonstrate that the proposed framework achieves signal-to-noise ratio gains of approximately 9 dB and 8 dB over fixed-antenna and relay-assisted systems, respectively. Furthermore, the proposed detection method reduces computational complexity by over 75% with less than 0.5 dB performance degradation.

This paper studies the simultaneous transmitting and reflecting reconfigurable intelligent surfaces (Active STAR-RIS) assisted cell-free massive MIMO multiple-input multiple-output system with a low-resolution analog-to-digital converter (ADC). An additive quantization noise model (AQNM) is investigated to capture the effect of the low-resolution ADC. Closed-form expressions for linear minimum mean square error channel estimation is derived. Furthermore, we derive the uplink spectral efficiency (SE) in closed form under maximum ratio combined receiver filter. Based on this analytical framework, we undertake a quantitative exploration of how various system parameters influence the uplink SE. Moreover, a detailed trade-off analysis is conducted to evaluate the deployment of supplementary access points (APs) in comparison to the integration of additional RISs. In order to enhance the precision of channel estimation, this paper develops a normalized mean square error optimization framework that minimizes errors across all UEs. This approach simultaneously reduces the pilot transmit power and mitigates pilot contamination during the uplink pilot training phase, utilizing a successive convex approximation method.

Spectral efficiency (SE) and energy efficiency (EE) are two major challenges faced by the sixth-generation wireless communication systems. In this paper, we propose a reconfigurable intelligent surfaces-assisted simultaneous wireless information and power transfer scheme based on fluid antenna port grouping index modulation (RIS-FA-PGIM). The flexible port switching capability of FA overcomes the spatial limitations of traditional antennas, significantly improving the SE. Further-more, in order to improve the SE and EE of the system, this paper jointly optimizes the beamforming matrix at the base station and RIS. Due to the coupling relationship between variables, the optimization problem is non-convex and difficult to solve. In order to solve this problem, an alternating optimization algorithm is proposed, which gradually approaches the global optimal solution through an iterative optimization process. Simulation results show that the system not only achieves outstanding SE performance but also realizes low energy consumption, which verifies the effectiveness and superiority of the scheme.

The study of special vehicle crews' mission responses is essential for optimizing their working conditions and enhancing combat effectiveness. This study investigates the physiological, behavioral, and subjective workload responses of crews with varying experience levels in visual/motion tasks with different demands. A virtual simulation system was employed with 120 participants categorized into professionals, short-term trainees, and novices. EEG, eye movement and NASA-TLX scores were measured across task conditions. Results indicate that as crew experience increases, NASA-TLX scores decrease, physiological responses stabilize, but task completion times lengthen, with distinct behavioral patterns. Novices in low-demand motion tasks produce physiological data statistically like professionals. Short-term trainees in high-demand motion tasks produce coefficient of variation results of physiological data statistically like professionals. These findings suggest that short-term trainees can substitute for professionals in high-demand motion mechanical tasks, with implications for research data reliability assessment and increasing training and operational efficiency.

In the human-machine system of armored vehicles, the cognitive performance state of crews is crucial for the personnel security and combat efficiency. The purpose of this research was to establish a real-time assessment system for cognitive performances of armored vehicle crews, consisting of the data input module, data processing module, data visualization module, and scheduling module. Forty subjects were recruited to cooperate and execute the cross-platform strike task in a virtual simulation platform. The physiological data and operation behavior data was collected during the experiment process. To realize the accurate classification of different cognitive performance states, a multi-source information fusion algorithm was developed based on linear discriminant analysis (LDA) and D-S evidence theory, which included the information collection module, the feature extraction module, and the information fusion module. The results indicated that there existed a significant correlation between the extractive feature indicators (i.e., EOG, ECG, and task performance indicators) and the cognitive performance. The recognition accuracy and the data efficiency of the proposed assessment system were 91.25% and 96.69% respectively by using the complementarity of different evidences, which were higher than the others using partial information sources. This study can provide a reference for the comprehensive assessment of cognitive performance of human operators in military and industrial domains.

With the development of technology, future tractors will become more intelligent. More complex interfaces and several control components tend to cause drivers’ cognitive load to be easily overloaded. Therefore, an evaluation method of the control interface should be proposed from the cognitive load perspective. To realise this concept, first, the influence of the design elements of the interface on behaviour time was investigated and a behaviour time model was established. Consequently, the experimental data could be well fitted by the model (R2 > 0.9), and the behaviour time of the operating interfaces could be effectively predicted. Second, an evaluation index of the interface was proposed based on behaviour time, which could evaluate the interface’s design level. Finally, the validity of the evaluation method was verified. The results provide theoretical guidance for human–machine interfaces for tractors from the perspective of drivers’ cognitive load.

In this paper, a novel active fully-connected reconfigurable intelligent surface assisted space shift keying and code index modulation (AFRIS-SCIM) scheme is proposed. On one hand, by introducing joint space-code index modulation while maintaining low power consumption and complexity, the proposed scheme achieves higher data rates compared to existing one-dimensional index modulation. On the other hand, the proposed active fully-connected architecture achieves a desirable trade-off between reliability and power consumption compared to conventional passive RIS and active RIS architectures. Additionally, to reduce detection complexity at the receiver, a low-complexity detection algorithm is proposed and the upper bound for the bit error rate (BER) of the system is derived. Mathematical models characterizing the system complexity and power consumption are also established to analyze the overall performance. Both theoretical analyses and simulation results demonstrate that the AFRIS-SCIM scheme outperforms existing RIS-IM schemes as well as multidimensional index modulation systems in terms of BER performance.

The reconfigurable intelligent surface (RIS) aided index modulation (IM) is a promising technology for next-generation wireless communications. However, acquiring channel state information (CSI) for RIS-based IM requires expensive pilot overhead, especially for the IM in multiple domains. In this paper, a novel rectangular differential reflecting spatial modulation (RDRSM) system is proposed for the RIS-aided multiple-input multiple-output (MIMO) system. Specifically, the proposed multi-antenna-activated RDRSM (M-RDRSM) scheme utilizes a rectangular dispersion matrix (DM) to jointly map a digital beamforming (DBF) weight vector and a RIS reflection pattern to perform the rectangular differential modulation. A thorough analysis presents that the proposed M-RDRSM scheme can achieve high-spectral efficiency, low complexity of the system, and noncoherent decoding without prior knowledge of CSI in the space-reflection dual-domain IM. Further, the proposed M-RDRSM scheme is simplified to a single-antenna-activated RDRSM (S-RDRSM) scheme, which can reduce the hardware cost and avoid the inter-antenna synchronization problem more effectively. Simulation results demonstrate that the proposed RDRSM scheme performs better in terms of bit error rate performance and achieve a lower decoding complexity than the existing correlated differential IM schemes with the same achievable spectral efficiency.

Abstract Code‐index modulation (CIM) uses the index of spreading code to convey information, which can be integrated with different kinds of MIMO systems to achieve higher throughput. This paper proposes a novel CIM‐integrated space time shift keying scheme called CIM‐STSK. The CIM‐STSK system employs three types of resources to transmit information bits, which are Hadamard codes, dispersion matrix indexes and QAM constellation symbols. The mathematical expression of the bit error rate of the CIM‐STSK system is derived, and the theoretical analysis is validated with Monte Carlo simulation results. Compared with the corresponding CIM‐SS, STSK, CIM‐SM, and CIM‐QSM systems, CIM‐STSK scheme can not only improve spectrum efficiency, but also achieve a better error performance.

Abstract Differential spatial modulation (DSM) is a multi‐antenna differential technology with low power consumption and no demand of channel estimation. It is suitable for communication systems that have fast migration velocity and high requirements for both power consumption and complexity. However, due to the sparse structure and the requirements of differential coding, the spectral efficiency is limited. Therefore, media‐based modulation (MBM) technology is introduced into differential system in this work to improve the spectral. A differential space time media‐based modulation (DSTMBM) system is proposed. While retaining the inherent advantages of the DSM, the additional bits are transmitted through the radio frequency (RF) mirrors in DSTMBM. Unlike traditional DSM, the transmit antenna of DSTMBM system can be activated multiple times. In addition, a theoretical performance is derived, and a low‐complexity (LC) detection algorithm is adopted. Simulation results show that the DSTMBM system has a performance advantage of about 4.5 dB at a high transmission rate compared to traditional DSM systems. Monte Carlo simulation matches the theoretical performance in a wide range. Meanwhile, the LC detection algorithm reduces the complexity by 2–3 orders of magnitude without the bit error rate (BER) performance loss.

An energy‐harvesting decode‐and‐forward cooperative system over correlated Rayleigh fading channels is investigated. Simultaneous wireless information and power transfer (SWIPT) technology is employed at the relay to improve energy efficiency. To overcome the spatial correlation among the transmit antennas, precoding spatial modulation (PSM) is formulated. The average bit‐error probability (ABEP) upper bound is derived and it matches closely with the Monte Carlo simulation results. The influence of the parameters, such as the power‐splitting factor and transmit correlation coefficient, on system performance is studied. The results show that the proposed PSM‐SWIPT system can achieve better ABEP performance than SM‐SWIPT, space shift keying‐SWIPT and multiple‐input–multiple‐output‐SWIPT systems under the same spectral efficiency.