Performance Analysis of Millimeter Wave Massive MIMO Systems in Centralized and Distributed Schemes

This paper considers downlink multi-user millimeter-wave massive multiple-input multiple-output (MIMO) systems in both centralized and distributed configurations, referred to as C-MIMO and D-MIMO, respectively. Assuming the fading channel is composite and comprised of both large-scale fading and small-scale fading, a hybrid precoding algorithm leveraging antenna array response vectors is applied into both the C-MIMO system with fully connected structure and the D-MIMO system with partially connected structure. First, the asymptotic spectral efficiency (SE) of an arbitrary user and the asymptotic average SE of the cell for the C-MIMO system are analyzed. Then, two radio access unit (RAU) selection algorithms are proposed for the D-MIMO system, based on minimal distance (D-based) and maximal signal-to-interference-plus-noise-ratio (SINR) (SINR-based), respectively. For the D-MIMO system with circular layout and D-based RAU selection algorithm, the upper bounds on the asymptotic SE of an arbitrary user and the asymptotic average SE of the cell are also investigated. Finally, numerical results are provided to assess the analytical results and evaluate the effects of the numbers of total transmit antennas and users on system performance. It is shown that, from the perspective of the cell, the D-MIMO system with D-based scheme outperforms the C-MIMO system and achieves almost alike performance compared with the SINR-based solution while requiring less complexity.Peer reviewe

Average transmit power of adaptive ZF very large multi-user and multi-antenna systems

This document is the Accepted Manuscript version of the following article: Dian-Wu Yue, and Yichuang Sun, ‘Average Transmit Power of Adaptive ZF Very Large Multi-user and Multi-antenna Systems’, Wireless Personal Communications, Vol. 81 (3): 1215-1232, April 2015. The final publication is available at Springer via https://doi.org/10.1007/s11277-014-2180-6.In this paper, we investigate adaptive zero-forcing uplink transmission for very large multi-user multi-antenna systems in Rayleigh fading environments. We assume that the number of antennas at the base station (denoted as $$M$$M) is not less than the number of users (denoted as $$K$$K) with each having single antenna, and power control can be done at the transmitter(s) as channel condition changes. Under constraints of individual rates and maximum transmit powers, we adopt the optimal transmit strategy of minimizing the total average transmit power (ATP). We derive and give individual ATP expressions for each link with short- and long-term rate constraints, respectively. Numerical results show that the individual ATP for each link with short term rate constraint is quite close to its long term counterpart when $$M-K$$M-K is large, and its corresponding outage probability can be designed to be nearly zero at the same time. Finally, we present two simple adaptive transmission schemes with constant transmit power satisfying short- and long-term rate constraints, respectively. Both of them are easy to implement, and asymptotically optimal when $$M-K$$M-K grows without bound.Peer reviewe

Energy Efficiency Maximization in IRS-Aided Cell-Free Massive MIMO System

In this paper, we consider an intelligent reflecting surface (IRS)-aided cell-free massive multiple-input multiple-output system, where the beamforming at access points and the phase shifts at IRSs are jointly optimized to maximize energy efficiency (EE). To solve EE maximization problem, we propose an iterative optimization algorithm by using quadratic transform and Lagrangian dual transform to find the optimum beamforming and phase shifts. However, the proposed algorithm suffers from high computational complexity, which hinders its application in some practical scenarios. Responding to this, we further propose a deep learning based approach for joint beamforming and phase shifts design. Specifically, a two-stage deep neural network is trained offline using the unsupervised learning manner, which is then deployed online for the predictions of beamforming and phase shifts. Simulation results show that compared with the iterative optimization algorithm and the genetic algorithm, the unsupervised learning based approach has higher EE performance and lower running time.Comment: 6 pages, 4 figure

Observation of the application effect of low-volume polyethylene glycol electrolyte lavage solution (PEG-ELS) combined with ascorbic acid tablets in bowel preparation for colonoscopy in hospitalized patients

BackgroundThis study explored the effectiveness and safety of low-volume polyethylene glycol electrolyte lavage solution (PEG-ELS) combined with ascorbic acid tablets (PEG-ELS/Asc) in bowel preparation for a colonoscopy.MethodsA total of 240 hospitalized patients who underwent a colonoscopy in Wenzhou People’s Hospital, Wenzhou Third Clinical College of Wenzhou Medical University from July 2020 to June 2022 were randomly divided into two groups, with 120 patients each. All of the participants were given a low-residue or residue-free diet one day before the examination and fasted after dinner (completed before 18:00) the day before the examination. The 2-L PEG-ELS/Asc group took 2-L PEG-ELS plus 10 g ascorbic acid tablets once orally, while the 3-L PEG-ELS group took 3-L PEG orally on several occasions. The primary endpoint was the achievement of preparation adequacy and an overall colon cleansing score of ≥6, both assessed by blinded investigators using the Boston Bowel Preparation Scale (BBPS). The bowel cleansing effect, polyp detection rate, adverse reaction rate, oral drug tolerance rate, renal function, and electrolyte level changes were also compared between the two patient groups.ResultsThere were no significant differences in the success rate of bowel preparation, the detection rate of polyps, or the adverse reaction rate between the two groups (P > 0.05). The tolerance rate of bowel preparation in the 2-L PEG-ELS/Asc group was significantly higher than that in the 3-L PEG-ELS group (93.3% vs. 80.23%) (P < 0.05). The levels of creatinine, serum potassium, serum sodium, and serum chlorine of the two groups before and after bowel preparation were within the normal range. In addition, the intestinal cleaning effect of the two preparation schemes for the hospitalized patients with diabetes and constipation is worse than that of those without these conditions (P < 0.05).ConclusionThe effectiveness and safety of using 2-L PEG-ELS/Asc in bowel preparation for a colonoscopy in hospitalized patients were not inferior to using 3-L PEG-ELS. For patients with diabetes and constipation, the cleansing effect of the two bowel preparation options was not very satisfactory, and further clinical research is needed in this regard

Transmit Power Minimization for MIMO Systems of Exponential Average BER with Fixed Outage Probability

This document is the Accepted Manuscript version of the following article: Dian-Wu Yue, and Yichuang Sun, ‘Transmit Power Minimization for MIMO Systems of Exponential Average BER with Fixed Outage Probability’, Wireless Personal Communications, Vol. 90 (4): 1951-1970, first available online on 20 June 2016. Under embargo. Embargo end date: 20 June 2017. The final publication is available at Springer via https://link.springer.com/article/10.1007%2Fs11277-016-3432-4This paper is concerned with a wireless multiple-antenna system operating in multiple-input multiple-output (MIMO) fading channels with channel state information being known at both transmitter and receiver. By spatiotemporal subchannel selection and power control, it aims to minimize the average transmit power (ATP) of the MIMO system while achieving an exponential type of average bit error rate (BER) for each data stream. Under the constraints on each subchannel that individual outage probability and average BER are given, based on a traditional upper bound and a dynamic upper bound of Q function, two closed-form ATP expressions are derived, respectively, which can result in two different power allocation schemes. Numerical results are provided to validate the theoretical analysis, and show that the power allocation scheme with the dynamic upper bound can achieve more power savings than the one with the traditional upper bound.Peer reviewe

Special issue on cooperative wireless and mobile communications

© The Institution of Engineering and Technology 2013.The fundamental idea of cooperative communications in wireless networks originates from the design of multiple-antenna systems. In multiple-antenna systems, communicating terminals are equipped with multiple antennas to mitigate the effects of multipath fading and optimise the communication rate in the network. Wireless communication nodes like cellular phones and sensor nodes have size restrictions, power supply limitations and are only able to accommodate a limited level of complexity. It is thus unfeasible to equip them with multiple antennas. The effects of multipath fading are critical in cellular, ad hoc and sensor networks because the physical deployment of communicating nodes makes them susceptible to interference. It is imperative to adopt a mechanism to combat fading in such networks. The broadcast nature of the wireless medium makes it easy for the communicating nodes to hear each other. They can share their physical resources specifically their single antennas, thereby creating a virtual multiple-antenna array. Cooperative communications is a concept where several single-antenna nodes cooperate and form a distributed multiple-antenna system which combats multipath fading. In recent years, cooperative communications have received extensive world-wide attention and significant advances in both research and applications have been achieved. The aim of this Special Issue is to publish research papers reflecting the most recent research and application results in cooperative wireless and mobile communications and networks, with emphasis on the physical layer challenges of virtual and distributed multiple-input–multiple-output (MIMO). A good number of submissions have been received. After a rigorous review, 12 papers have been selected for publication in the Special Issue. These papers are, respectively, concerned with randomised distributed space–time coding schemes, full-rate alternate-relaying cooperative systems with simplified detectors, adaptive transmission techniques for cooperative networks with limited feedback, cooperative MC-CDMA downlink transmission with preprocessing, capacity of generalised network MIMO with multicell cooperation, joint and distributed scheduling with power control in mulitcell OFDMA networks, relay selection strategies for two-way mobile relaying networks with analogue network coding protocol, multiple-source multiple-destination relay channels with network coding, cooperative spectrum sensing with hidden Markov models, cognitive relay networks with relay selection, cooperative communication between cognitive and primary users and optimal incentive collaborative primary-secondary transmission. These topics can be broadly classified into the following four directions: development of more general and practical models of cooperative communications (papers 1–4), research of multicell networks with cooperative communications (papers 5 and 6), fusion of cooperative diversity and network coding (papers 7 and 8) and combination of cooperative communications and cognitive radio (papers 9–12). As one of the most important enabling technologies of recent time, cooperative communication techniques will play a crucial role in the development of 5G wireless and mobile networks and receive continued focus of research from world-wide academia and industry. We are grateful to all the authors of the papers for their contribution to the Special Issue. We would also like to thank all the reviewers of the papers for their careful and valuable comments. Assistance from the editorial staff at the IET is much appreciated. Finally, support from Sherman Shen, Editor-in-Chief of IET Communications and Kruna Vukmirovic, IET Journal Development Editor is highly acknowledged.Peer reviewe