98 research outputs found
Demo: Reconfigurable Distributed Antennas and Reflecting Surface (RDARS)-aided Integrated Sensing and Communication System
Integrated sensing and communication (ISAC) system has been envisioned as a
promising technology to be applied in future applications requiring both
communication and high-accuracy sensing. Different from most research focusing
on theoretical analysis and optimization in the area of ISAC, we implement a
reconfigurable distributed antennas and reflecting surfaces (RDARS)-aided ISAC
system prototype to achieve the dual-functionalities with the communication
signal. A RDARS, composed of programmable elements capable of switching between
reflection mode and connected mode, is introduced to assist in uplink signal
transmission and sensing. The developed RDARS-aided ISAC prototype achieves
reliable user localization without compromising the communication rate,
showcasing its potential for future 6G systems.Comment: 2 pages, 3 figures. Accepted by IEEE/CIC International Conference on
Communications in China, Dalian, China, 202
The impact of benevolent leadership and workplace friendship on job satisfaction through job involvement
Due to the dynamic nature of the global environment, organizations face some challenges in modern society. One of the many challenges that companies face is to satisfy their employees to adapt to a constantly evolving and changing environment and to achieve success and maintain a competitive advantage. To improve employee effectiveness, efficiency, work commitment, and productivity, corporates must meet and satisfy the needs of employees by adopting effective leadership and focus on the relationships at the workplace. The objective of this paper is to analyze the impact of benevolent leadership and friendship at work on employee job satisfaction through job involvement. The study adopted a quantitative methodology. Primary data was collected through self-managed online questionnaires. The questionnaire is taken from several previous articles. The target population consists of employees and employers from China. Simple random sampling is used to collect data from 263 participants. The results indicate a positive relationship between benevolent leadership and employee job satisfaction through job involvement, while friendship at the workplace has no significant effect on job satisfaction through job involvement. The study concludes with some brief prospects that companies and managers need to recognize the importance of benevolent leadership in maximizing the level of employees’ job satisfaction. This paper may contribute to employees’ personal growth and development by encouraging managers to motivate employees with benevolence for achieving organizational goals and improve job involvement and job satisfaction to make more achievements to their work and society
RIS-Aided MIMO Systems with Hardware Impairments: Robust Beamforming Design and Analysis
Reconfigurable intelligent surface (RIS) has been anticipated to be a novel
cost-effective technology to improve the performance of future wireless
systems. In this paper, we investigate a practical RIS-aided
multiple-input-multiple-output (MIMO) system in the presence of transceiver
hardware impairments, RIS phase noise and imperfect channel state information
(CSI). Joint design of the MIMO transceiver and RIS reflection matrix to
minimize the total average mean-square-error (MSE) of all data streams is
particularly considered. This joint design problem is non-convex and
challenging to solve due to the newly considered practical imperfections. To
tackle the issue, we first analyze the total average MSE by incorporating the
impacts of the above system imperfections. Then, in order to handle the tightly
coupled optimization variables and non-convex NP-hard constraints, an efficient
iterative algorithm based on alternating optimization (AO) framework is
proposed with guaranteed convergence, where each subproblem admits a
closed-form optimal solution by leveraging the majorization-minimization (MM)
technique. Moreover, via exploiting the special structure of the unit-modulus
constraints, we propose a modified Riemannian gradient ascent (RGA) algorithm
for the discrete RIS phase shift optimization. Furthermore, the optimality of
the proposed algorithm is validated under line-of-sight (LoS) channel
conditions, and the irreducible MSE floor effect induced by imperfections of
both hardware and CSI is also revealed in the high signal-to-noise ratio (SNR)
regime. Numerical results show the superior MSE performance of our proposed
algorithm over the adopted benchmark schemes, and demonstrate that increasing
the number of RIS elements is not always beneficial under the above system
imperfections.Comment: 30 pages, 8 figures. This paper has been submitted to IEEE journal
for possible publicatio
Achievable Diversity Order of HARQ-Aided Downlink NOMA Systems
The combination between non-orthogonal multiple access (NOMA) and hybrid
automatic repeat request (HARQ) is capable of realizing ultra-reliability, high
throughput and many concurrent connections particularly for emerging
communication systems. This paper focuses on characterizing the asymptotic
scaling law of the outage probability of HARQ-aided NOMA systems with respect
to the transmit power, i.e., diversity order. The analysis of diversity order
is carried out for three basic types of HARQ-aided downlink NOMA systems,
including Type I HARQ, HARQ with chase combining (HARQ-CC) and HARQ with
incremental redundancy (HARQ-IR). The diversity orders of three HARQ-aided
downlink NOMA systems are derived in closed-form, where an integration domain
partition trick is developed to obtain the bounds of the outage probability
specially for HARQ-CC and HARQ-IR-aided NOMA systems. The analytical results
show that the diversity order is a decreasing step function of transmission
rate, and full time diversity can only be achieved under a sufficiently low
transmission rate. It is also revealed that HARQ-IR-aided NOMA systems have the
largest diversity order, followed by HARQ-CC-aided and then Type I HARQ-aided
NOMA systems. Additionally, the users' diversity orders follow a descending
order according to their respective average channel gains. Furthermore, we
expand discussions on the cases of power-efficient transmissions and imperfect
channel state information (CSI). Monte Carlo simulations finally confirm our
analysis
Reconfigurable Distributed Antennas and Reflecting Surface: A New Architecture for Wireless Communications
Distributed Antenna Systems (DASs) employ multiple antenna arrays in remote
radio units to achieve highly directional transmission and provide great
coverage performance for future-generation networks. However, the utilization
of active antenna arrays results in a significant increase in hardware costs
and power consumption for DAS. To address these issues, integrating DAS with
Reconfigurable Intelligent Surfaces (RIS) offers a viable approach to ensure
transmission performance while maintaining low hardware costs and power
consumption. To incorporate the merits of RIS into the DAS from practical
consideration, a novel architecture of ``Reconfigurable Distributed Antennas
and Reflecting Surfaces (RDARS)'' is proposed in this paper. Specifically,
based on the design of the additional direct-through state together with the
existing high-quality fronthaul link, any element of the RDARS can be
dynamically programmed to connect with the base station (BS) via fibers and
perform the connected mode as remote distributed antennas of the BS to receive
or transmit signals. Additionally, RDARS also inherits the low-cost and
low-energy-consumption benefits of fully passive RISs by default configuring
the elements as passive to perform the reflection mode. As a result, RDARS
offers flexible control over the trade-off between distribution gain and
reflection gain to enhance performance. The ergodic achievable rate under the
RDARS architecture is analyzed and closed-form expression with meaningful
insights is derived. The theoretical analysis and simulation results prove that
the RDARS achieves a higher achievable rate than both DAS and RIS. A RDARS
prototype with 256 elements is built for real experiments which shows that the
RDARS-aided system can achieve an additional 21% and 170% throughput
improvement over DAS and RIS-aided systems, respectively.Comment: 13 pages, 9 figure
Throughput Maximization for UAV-enabled Integrated Periodic Sensing and Communication
Unmanned aerial vehicle (UAV) is expected to revolutionize the existing
integrated sensing and communication (ISAC) system and promise a more flexible
joint design. Nevertheless, the existing works on ISAC mainly focus on
exploring the performance of both functionalities simultaneously during the
entire considered period, which may ignore the practical asymmetric sensing and
communication requirements. In particular, always forcing sensing along with
communication may make it is harder to balance between these two
functionalities due to shared spectrum resources and limited transmit power. To
address this issue, we propose a new integrated periodic sensing and
communication mechanism for the UAV-enabled ISAC system to provide a more
flexible trade-off between two integrated functionalities. Specifically, the
system achievable rate is maximized via jointly optimizing UAV trajectory, user
association, target sensing selection, and transmit beamforming, while meeting
the sensing frequency and beam pattern gain requirement for the given targets.
Despite that this problem is highly non-convex and involves closely coupled
integer variables, we derive the closed-form optimal beamforming vector to
dramatically reduce the complexity of beamforming design, and present a tight
lower bound of the achievable rate to facilitate UAV trajectory design. Based
on the above results, we propose a penalty-based algorithm to efficiently solve
the considered problem. The optimal achievable rate and the optimal UAV
location are analyzed under a special case of infinity number of antennas.
Furthermore, we prove the structural symmetry between the optimal solutions in
different ISAC frames without location constraints and propose an efficient
algorithm for solving the problem with location constraints.Comment: 32 pages, This work has been submitted to the IEEE for possible
publicatio
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