Channel Estimation for Large Intelligent Surface-Based Transceiver Using a Parametric Channel Model

<div>Large intelligent surface-based transceivers (LISBTs), in which a spatially continuous surface is being used for signal transmission and reception, have emerged as a promising solution for improving the coverage and data rate of wireless communication systems. To realize these objectives, the acquisition of accurate channel state information (CSI) in LISBT-assisted wireless communication systems is crucial. In this paper, we propose a channel estimation scheme based on a parametric physical channel model for line-of-sight dominated communication in millimeter and terahertz wave bands. The proposed estimation scheme requires only five pilot signals to perfectly estimate the channel parameters assuming there is no noise at the receiver. In the presence of noise, we propose an iterative estimation algorithm that decreases the channel estimation error due to noise. The training overhead and computational cost of the proposed scheme do not scale with the number of antennas. The simulation results demonstrate that the proposed estimation scheme significantly outperforms other benchmark schemes.</div>

Channel Estimation for Large Intelligent Surface-Based Transceiver Using a Parametric Channel Model

<div>Large intelligent surface-based transceivers (LISBTs), in which a spatially continuous surface is being used for signal transmission and reception, have emerged as a promising solution for improving the coverage and data rate of wireless communication systems. To realize these objectives, the acquisition of accurate channel state information (CSI) in LISBT-assisted wireless communication systems is crucial. In this paper, we propose a channel estimation scheme based on a parametric physical channel model for line-of-sight dominated communication in millimeter and terahertz wave bands. The proposed estimation scheme requires only five pilot signals to perfectly estimate the channel parameters assuming there is no noise at the receiver. In the presence of noise, we propose an iterative estimation algorithm that decreases the channel estimation error due to noise. The training overhead and computational cost of the proposed scheme do not scale with the number of antennas. The simulation results demonstrate that the proposed estimation scheme significantly outperforms other benchmark schemes.</div>

Evaluation of cell load of the LTE network based on control information decoding

Cell load evaluation is the one of the tools used for the development of methods to increase quality of service (QoS) in cellular networks. For instance, the analysis of mobile traffic usage can be used for network optimization and management in terms of radio resources. Existing assessing methods, such as drive tests or passive evaluations based on analysis of physical channel indicators are either unreliable, inaccurate, or inconvenient. A cell load evaluation method based on decoding and analysing the control channels is presented. The method can reliably monitor the resource allocations and the throughput in a public mobile cell. A real LTE signal recorded from the eNodeB using software defined radio was analysed. The main indicators of the cell were determined, including the efficiency of using resource blocks, the number of active users, and the cell’s throughput. The accuracy of the algorithm was also evaluated in this paper.

On the Spectral Efficiency for Distributed Massive MIMO Systems

Distributed MIMO (D-MIMO) systems are expected to play a key role in deployments for future mobile communications. Together with massive MIMO technology, D-MIMO aims to maximize the spectral efficiency and data rate in mobile networks. This paper proposes a deep study on the spectral efficiency of D-MIMO systems for essential channel parameters, such as the channel power balance or the correlation between propagation channels. For that purpose, several propagation channels were acquired in both anechoic and reverberation chambers and were emulated using channel simulators. In addition, several frequency bands were studied, both the sub–6 GHz band and mmWave band. The results of this study revealed the high influence of channel correlation and power balance on the physical channel performance. Low-correlated and high-power balance propagation channels show better performances than high correlated and power unbalance channels in terms of spectral efficiency. Given these results, it will be fundamental to take into account the spectral efficiency of D-MIMO systems when designing criteria to establish multi-connectivity in future mobile network deployments.

Educational Blockchain: A Secure Degree Attestation and Verification Traceability Architecture for Higher Education Commission

Degree attestation verification and traceability are complex one-to-one processes between the Higher Education Commission (HEC) and universities. The procedure shifted to the digitalized manner, but still, on a certain note, manual authentication is required. In the initial process, the university verified the degree and stamp seal first. Then, a physical channel of degree submission to the receiving ends is activated. After that, the degree is attested while properly examining and analyzing the tamper records related to degree credentials through e-communication with the university for verification and validation. This issue poses a serious challenge to educational information integrity and privacy. Potentially, blockchain technology could become a standardized platform to perform tasks including issuing, verifying, auditing, and tracing immutable records, which would enable the HEC, universities, and Federal Education Ministry (FEM) to quickly and easily get attested and investigate the forge proof versions of certificates. Besides, decentralized distributed data blocks in chronological order provide high security between distributed ledgers, consensus engine, digital signature, smart contracts, permissioned application, and private network node transactions that guarantee degree record validation and traceability. This paper presents an architecture (HEDU-Ledger) and detail design of blockchain-enabled hyperledger fabric applications implementation for degree attestation verification and traceable direct channel design between HEC and universities. The hyperledger fabric endorses attestation records first, and then validates (committer) the degree and maintains the secure chain of tracing between stakeholder peer nodes. Furthermore, this HEDU-Ledger architecture avoids language and administrative barriers. It also provides robustness in terms of security and privacy of records and maintains integrity with secure preservation as compared to that of the other state-of-the-art methods.

Performance of multi-antenna wireless systems based on time reversal

5G wireless mobile communication system is faced with massive equipment access, information security and effective transmission is worth paying attention to. Wireless physical layer security mainly uses encryption principle to enhance the security of information transmission, while time reversal technology combines its electromagnetic characteristics and physical channel characteristics to improve the security performance of wireless communication system. In this paper, a signal transmission model of wireless multi-antenna communication system based on time reversal cavity is proposed and white Gaussian noise is introduced. The simulation results show that the space-time focusing characteristics of time reversal cavity can make the signal energy more concentrated on the target user, which can not only effectively alleviate the communication quality problems caused by multipath effect, but also ensure the security of information transmission process.

Pricing and Coordination Strategies of Dual Channels Considering Consumers’ Channel Preferences

With the rapid development of electronic commerce, consumers can freely buy the same product from a manufacturers’ Internet channel or a resellers’ physical channel. Based on the consumers’ channel preferences, this article classifies consumers into three types and investigates the price decision in a dual-channel supply chain using a Stackelberg game, which assumes that the manufacturer, as the game leader, first sets the wholesale price, then the reseller decides the retail price, according to the wholesale price. Furthermore, some numerical experiments are developed to investigate the impact of consumer acceptance, the degree of customer loyalty, and the proportion of identical shoppers on prices and profits. The results show that whether both the retail price and the wholesale price rise or fall depends on a combination of the cost of the physical channel and the Internet shopper’s acceptance of the Internet channel. The reseller’s profit is always lower than the manufacturer’s profit. The reseller’s profit is lower and the manufacturer’s profit is higher, compared with that of a traditional single channel supply chain. The numerical experiments showed that when an Internet shopper’s acceptance of an Internet channel is lower, the wholesale price and retail price in the dual channels will increase with an increase of the degree of customer loyalty (the proportion of identical shoppers). The reseller’s profit (the manufacturer’s profit) will reduce (rise) with the augmentation of the Internet shopper’s acceptance of an Internet channel. Finally, we design a revenue-sharing contract that can coordinate the supply chain and implement a win–win strategy for all partners. This work makes some contributions to the research area of coordination in dual-channel supply chains.

Review Product Distribution Through Different Channels

This study aims to investigate the literature in product distribution and channel competition. In this study, past work related to the product distribution through different channels is extensively reviewed. Based on the channel differentiation, channel competition is also reviewed. Finally, the study proposes that the future research may focus on helping the producer make a decision whether to sell the product through its own direct channel (online) through a physical channel or both based on the difference between these two channels.

The Role of Correlation in the Performance of Massive MIMO Systems

Massive multiple-input multiple-output (m-MIMO) is considered as an essential technique to meet the high data rate requirements of future sixth generation (6G) wireless communications networks. The vast majority of m-MIMO research has assumed that the channels are uncorrelated. However, this assumption seems highly idealistic. Therefore, this study investigates the m-MIMO performance when the channels are correlated and the base station employs different antenna array topologies, namely the uniform linear array (ULA) and uniform rectangular array (URA). In addition, this study develops analyses of the mean square error (MSE) and the regularized zero-forcing (RZF) precoder under imperfect channel state information (CSI) and a realistic physical channel model. To this end, the MSE minimization and the spectral efficiency (SE) maximization are investigated. The results show that the SE is significantly degraded using the URA topology even when the RZF precoder is used. This is because the level of interference is significantly increased in the highly correlated channels even though the MSE is considerably minimized. This implies that using a URA topology with relatively high channel correlations would not be beneficial to the SE unless an interference management scheme is exploited.