5 results
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2. Low-Complexity Beamforming Optimization for IRS-Aided MU-MIMO Wireless Systems.
- Author
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Moon, Seungsik, Lee, Hyeongtaek, Choi, Junil, and Lee, Youngjoo
- Subjects
BILEVEL programming ,BEAMFORMING ,MATRIX inversion ,MATHEMATICAL optimization ,WIRELESS communications ,PROCESS optimization ,SIGNAL-to-noise ratio - Abstract
In this paper, we propose a cost-efficient beamforming optimization algorithm for multi-user wireless communication systems associated with the intelligent reflecting surface (IRS). From the baseline successive refinement algorithm, which gives a sub-optimal solution for the power minimization problem under the signal-to-interference-plus-noise-ratio (SINR) constraint at each user, several optimization techniques are proposed to reduce the computation complexity while maintaining the algorithm-level performance. To reduce the number of required multiply-accumulate (MAC) operations, we first simplify the complicated matrix inversion by utilizing the channel hardening effect. We also present the two-phase refinement process for the group-level optimization of phase-shift elements, further relaxing the computation complexity as well as the processing latency. Applying the proposed optimization techniques, as a result, numerical results show that the fully-optimized algorithm can reduce the computational costs by up to 89.4% while showing less than 1 dB power loss, leading to the practical solution for the next-generation IRS-aided communication. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
3. IRS-Assisted Downlink and Uplink NOMA in Wireless Powered Communication Networks.
- Author
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Lyu, Bin, Ramezani, Parisa, Hoang, Dinh Thai, and Jamalipour, Abbas
- Subjects
WIRELESS communications ,REFLECTANCE ,ENERGY transfer ,SIGNAL-to-noise ratio ,RESOURCE allocation - Abstract
This paper studies the integration of the newly-emerged intelligent reflecting surface (IRS) technology into non-orthogonal multiple access (NOMA)-based wireless powered communication networks (WPCNs). We consider two WPCNs which communicate with a common hybrid access point (HAP), where there exists two types of devices in each WPCN, namely information receiving device (IRD) and harvest-then-transmit device (HTTD). Downlink communication from the HAP to IRDs, downlink energy transfer (ET) from the HAP to HTTDs, and uplink information transmission (IT) from the HTTDs to the HAP are assisted by two IRSs, one in each WPCN. Under this setup, we propose efficient algorithms to optimize reflection coefficients, beamforming vectors, and resource allocation for the sake of uplink sum-rate maximization, taking into account the minimum rate requirement at the IRDs. Numerical results show the considerable performance gain of the proposed NOMA-based scheme as compared to the conventional orthogonal multiple access (OMA)-based counterpart. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
4. Interference Suppression for Railway Wireless Communication Systems: A Reconfigurable Intelligent Surface Approach.
- Author
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Ma, Zheng, Wu, Yanliang, Xiao, Ming, Liu, Gang, and Zhang, Zhengquan
- Subjects
WIRELESS communications ,INTERFERENCE suppression ,RAILROADS ,CHANNEL estimation ,QUALITY of service - Abstract
Due to transmission of train control and dispatch commands, the ultra high reliability is required for railway wireless communication systems (RWCS). However, the quality of service (QoS) of RWCS is affected by external interference and jamming seriously in railway transportation. The external interference and jamming generated from intentional and/or unintentional sources can disturb the transmission of RWCS and be extremely dangerous for the trains’ safety. In this paper, a reconfigurable intelligent surface (RIS) approach is proposed to suppress the interference and jamming in RWCS. By taking the signal-to-interference-plus-noise (SINR) as the QoS metrics, the interference suppression problem with RIS is transformed into a maximizing receiving SINR problem. Two optimum solutions, which one is based on Charnes-Cooper transformation and the other is based on single linear programming, are provided. In order to deploy the RIS in RWCS practically, two low-complexity sub-optimum solutions, which one is to bypass the channel estimation for interference links and the other is to maximize the receiving desired power, are also discussed. The simulations results show that the RIS can be employed in RWCS with considerable anti-interference gain. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
5. Throughput Guarantees for Multi-Cell Wireless Powered Communication Networks With Non-Orthogonal Multiple Access.
- Author
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Huang, Liang, Nan, Runkai, Chi, Kaikai, Hua, Qiaozhi, Yu, Keping, Kumar, Neeraj, and Guizani, Mohsen
- Subjects
WIRELESS communications ,TIME management ,INTERNET speed ,INTERNET of things ,POWER transmission - Abstract
The emerging non-orthogonal multiple access (NOMA) technology can effectively improve the throughput performance of Internet of Things (IoT) devices. Besides throughput maximization, ensuring throughput fairness is a practical design issue when implementing NOMA in wireless powered communication networks (WPCN). To this end, we investigate the joint transmission time and power allocation problem for NOMA communication, aiming to improve the sum-throughput while guaranteeing different wireless devices’ (WDs’) throughput in multi-cell WPCN. In particular, we first analyze the feasibility of the problem by deriving the necessary and sufficient conditions for the existence of feasible solutions and propose an efficient algorithm to obtain the set of feasible values of transmission time allocation. We then propose an efficient algorithm for the transmission time allocation to improve the sum-throughput. During each search iteration, we adopt the successive convex approximation (SCA) approach to transform the non-convex power allocation problem into a sequence of convex problems and obtain the locally optimal transmit power under a fixed transmission time. Numerical simulations show that the proposed algorithm can improve the sum-throughput while guaranteeing each WD’s throughput. [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
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