Integrating unmanned aerial vehicles (UAVs) into the cellular network as new aerial users is a promising solution to meet their ever-increasing communication demands in a plethora of applications. Due to the high UAV altitude, the channels between UAVs and the ground base stations (GBSs) are dominated by the strong line-of-sight (LoS) links, which brings both opportunities and challenges. On one hand, a UAV can communicate with a large number of GBSs at the same time, leading to a higher macro-diversity gain as compared to terrestrial users. However, on the other hand, severe interference may be generated to/from the GBSs in the uplink/downlink, which renders the interference management with coexisting terrestrial and aerial users a more challenging problem to solve. To deal with the above new trade-off, this paper studies the uplink communication from a multi-antenna UAV to a set of GBSs in its signal coverage region. Among these GBSs, we denote available GBSs as the ones that do not serve any terrestrial users at the assigned resource block (RB) of the UAV, and occupied GBSs as the rest that are serving their respectively associated terrestrial users in the same RB. We propose a new cooperative interference cancellation strategy for the multi-beam UAV uplink communication, which aims to eliminate the co-channel interference at each of the occupied GBSs and in the meanwhile maximize the sum-rate to the available GBSs. Specifically, the multi-antenna UAV sends multiple data streams to selected available GBSs, which in turn forward their decoded data streams to their backhaul-connected occupied GBSs for interference cancellation. To draw useful insights and facilitate our proposed design, the maximum degrees-of-freedom (DoF) achievable by the multi-beam UAV communication for sum-rate maximization in the high signal-to-noise ratio (SNR) regime is first characterized, subject to the stringent constraint that all the occupied GBSs do not suffer from any interference in the UAV's uplink transmission. Then, based on the DoF-optimal design, the achievable sum-rate at finite SNR is maximized, subject to given maximum allowable interference power constraints at each of the occupied GBSs. The numerical examples validate the DoF and sum-rate performance of our proposed designs, as compared to benchmark schemes with fully cooperative, local, or no interference cancellation at the GBSs.
A new remote intelligent video surveillance system is proposed based on the processor of TMS320DM6446 and 3G network in this paper.This system can intelligently analyze video content captured from the camera to detect and store possible hidden troubles,and smartly transmit the monitoring information which conducted by the order of control site to one or more receive side.Data sending model include timing transmit,requested transmit and abnormal transmit.The design avoids large amount of data that 24 hours of continuous storage produce in the traditional video monitoring system,and can easily build on-line monitoring network by some cameras.Thus this system has intelligent surveillance,more convenient installation,good invisibility.
This paper briefly presents a novel spectrum trading model for OFDMA-based cognitive radio systems. In this model, primary users are able to trade their spare subcarriers with secondary users. Specifically, each subcarrier is priced by primary users and sold to secondary users for better utilities. Also, the issues of pricing policies and market equilibrium are discussed.
To address the problems of slow cancellation speed and low cancellation ratio of the current digital domain decomposition algorithm in high hopping speed and dramatically fast environment, this paper proposes an algorithm that uses a look-ahead QR decomposition-based recursive least square approach in the complex domain, aim to achieve fast cancellation and interference cancellation in the digital domain with high cancellation ratio. First, we analyze the iterative boundary of the conventional QRD-RLS algorithm, perform the third-order annihilation-reordering look-ahead, derive the iterative formula of the complex domain look-ahead and the structure of the systolic structure, then analyze the timing relationship of each unit, and finally perform the critical path optimization and build the systolic structure model of the third-order look-ahead. Upon comparison with the QRD-RLS algorithm, this method showcases an enhanced cancellation speed while maintaining a high cancellation ratio. Results from simulations indicate that the cancellation ratio of this method remains consistent with the RLS algorithm.
Intelligent reflecting surface (IRS) is a promising technology for achieving spectrum and energy-efficient wireless networks cost-effectively. Most existing works on IRS have focused on exploiting IRS to enhance the performance of wireless communication or wireless information transmission (WIT), while its potential for boosting the efficiency of radio frequency (RF) wireless energy transmission (WET) still remains largely open. Although IRS-aided WET shares similar characteristics with IRS-aided WIT, they differ fundamentally in terms of design objective, receiver architecture, practical constraints, and so on. In this article, we provide a tutorial overview on how to efficiently design IRS-aided WET systems as well as IRS-aided systems with both WIT and WET, namely, IRS-aided simultaneous wireless information and power transfer (SWIPT) and IRS-aided wireless powered communication network (WPCN), from a communication and signal processing perspective. In particular, we present state-of-the-art solutions to tackle the unique challenges in operating these systems, such as IRS passive reflection optimization, channel estimation, and deployment. In addition, we propose new solution approaches and point out important directions for future research and investigation.
Intracerebral hemorrhage (ICH) is a severe stroke that can adversely affect patient outcomes due to the accompanying inflammatory response. As a result, there is a growing interest in studying inflammation in ICH. We systematically reviewed relevant articles using the Web of Science to understand the literature on this subject. This study aims to provide a comprehensive overview of the field through bibliometric analysis, highlight its current status, identify frontiers, and speculate on future directions. We conducted a bibliometric analysis of the global English literature on inflammation related to ICH research based on the Web of Science from 1993 to the present to address publication trends and research hotspots. A total of 885 publications were included from 1993 to 2023. These articles were authored by 7,375 researchers from 1,639 organizations in 68 countries and published in 571 journals. Collectively, they cited 48,980 references from 5,621 journals. The author who published the most articles was Dr. Zhang, John H. Interestingly, 6 of the top ten most published authors were from China. Regarding the countries that published the most articles, China was at the top of the list, followed by the United States. The most frequently used keywords were "Inflammation", "Neuroinflammation", and "Microglia". Regarding journal publication and reference citations, Stroke was the most published and cited journal. Over the past 30 years, there has been considerable progress in scientific research concerning inflammation in the context of ICH. The pivotal themes of these studies have been immune cells and inflammatory mediators. It is worth noting, however, that most of the published literature on inflammation in ICH pertains to preclinical studies, with comparatively fewer clinical investigations. Several challenges must be addressed to translate these promising research achievements into clinical practice.
Aiming at the situation that normal detection means is hard to find the airborne moving target that has a small RCS and rapid moving speed characteristics, the algorithm of moving target detection is presented based on atmospheric wind field disturbing data detected by lidar. First, through receiving atmospheric wind field disturbance information that is produced by the airborne moving target moving on the air, and the excellent characteristics that lidar has in the detection atmosphere, atmospheric wind field disturbing retrieval model is established to acquire moving target space field distribution condition. Moving target space field change data is acquired based on filtering background air disturbance information, Moving target detection is carried out based on moving target detection algorithm. The result shows there is consistent between moving target detected by the algorithm and experimental result. An effective approach of greatly improving moving target detection ability for the low_detectable target is supplied.
This article presents an overview of the IEEE project 802.15.5 that targets providing mesh capabilities to both high-rate and low-rate wireless personal area networks. Low-rate mesh is built on IEEE 802.15.4 MAC, while high-rate mesh utilizes IEEE 802.15.3 MAC. We seek to share our insights and motivations of the approach adopted in the major components of the standard instead of presenting a la carte items drawn in the specification. We hope this article helps readers of the 802.15.5 standard to better understand the rationale and intent of the protocol design.
본 논문에서는 모노폴 안테나의 각 모드별 전계 분포를 분석하여 전류가 상대적으로 약한 부분(전계가 강한 부분)에 스터브를 이용해 기본 공진 모드에는 영향을 주지 않으면서 안테나의 하모닉 성분인 3차 모드 공진 주파수를 효율적으로 제어하고, 스터브의 두께를 조절하여 임피던스 특성을 조절할 수 있는 방법을 제안한다. 이 방법을 이용하여 일반적인 USB Dongle 크기(<TEX>$20{\times}45mm$</TEX>)에 안테나를 설계하였으며, -10 dB 기준 2 GHz 대역에서 대역폭이 600 MHz(2.3~3 GHz), 5 GHz 대역의 대역폭은 1 GHz(4.9~5.9 GHz)로 WLAN 주파수 대역을 만족하는 성능과 50 % 효율이 달성되었다. This paper presents a new method for designing a dual-band WIFI antenna using the third-order harmonic mode of a monopole antenna whose first-order mode operates at the low frequency band of WIFI. As analysing the current distribution of the third-order mode of this monopole antenna, the strongest point of electric field can be found. Then by attaching a stub at this point, the resonant frequency of the stub radiator can be adjusted from the third-order mode of the monopole antenna into the high frequency band of WIFI and the input impedance at this resonant frequency can be controlled with the width of the branch, without affecting the low frequency band of WIFI (the first-order mode of the monopole antenna). The compact dual-band antenna is designed at the size of an USB(universal serial bus) dongle and the bandwidth covers 600 MHz(2.3~3 GHz) at 2 GHz and 1 GHz(4.9~5.9 GHz) at 5 GHz under -10 dB which is satisfied with WLAN frequency. Efficiency of proposed antenna achieves over 50 % at WLAN frequency.
With bounded resources, traditional DBMS can't process and query the continuous and unbounded data stream in real time, and DBMS is researched widely as a new method to deal with this problem. The efficiency of the process and the query is improved with the new operator and the new query model introduced in DBMS. Firstly, the DSMS concept is introduced, and the principle of DSMS as well as the architecture of DSMS is discussed. Finally several typical DSMS instances are introduced and compared.
This paper studies the newly emerging wireless powered communication network in which one hybrid access point (H-AP) with constant power supply coordinates the wireless energy/information transmissions to/from a set of distributed users that do not have other energy sources. A "harvest-then-transmit" protocol is proposed where all users first harvest the wireless energy broadcast by the H-AP in the downlink (DL) and then send their independent information to the H-AP in the uplink (UL) by time-division-multiple-access (TDMA). First, we study the sum-throughput maximization of all users by jointly optimizing the time allocation for the DL wireless power transfer versus the users' UL information transmissions given a total time constraint based on the users' DL and UL channels as well as their average harvested energy values. By applying convex optimization techniques, we obtain the closed-form expressions for the optimal time allocations to maximize the sum-throughput. Our solution reveals an interesting "doubly near-far" phenomenon due to both the DL and UL distance-dependent signal attenuation, where a far user from the H-AP, which receives less wireless energy than a nearer user in the DL, has to transmit with more power in the UL for reliable information transmission. As a result, the maximum sum-throughput is shown to be achieved by allocating substantially more time to the near users than the far users, thus resulting in unfair rate allocation among different users. To overcome this problem, we furthermore propose a new performance metric so-called common-throughput with the additional constraint that all users should be allocated with an equal rate regardless of their distances to the H-AP. We present an efficient algorithm to solve the common-throughput maximization problem. Simulation results demonstrate the effectiveness of the common-throughput approach for solving the new doubly near-far problem in wireless powered communication networks.
Unmanned aerial vehicles (UAVs) have recently gained growing popularity in wireless communications owing to their many advantages such as swift and cost-effective deployment, line-of-sight (LoS) aerial-to-ground link, and controllable mobility in three-dimensional (3D) space. Although prior works have exploited the UAV's mobility to enhance the wireless communication performance under different setups, the fundamental capacity limits of UAV-enabled/aided multiuser communication systems have not yet been characterized. To fill this gap, we consider, in this paper, a UAV-enabled two-user broadcast channel (BC), where a UAV flying at a constant altitude is deployed to send independent information to two users at different fixed locations on the ground. We aim to characterize the capacity region of this new type of BC over a given UAV flight duration, by jointly optimizing the UAV's trajectory and transmit power/rate allocations over time, subject to the UAV's maximum speed and maximum transmit power constraints. First, to draw essential insights, we consider two special cases with asymptotically large/low UAV flight duration/speed, respectively. For the former case, it is shown that a simple hover-fly-hover (HFH) UAV trajectory with time division multiple access (TDMA)-based orthogonal multiuser transmission is capacity-achieving; while in the latter case, the UAV should hover at a fixed location that is nearer to the user with larger achievable rate and in general superposition coding (SC)-based non-orthogonal transmission with interference cancellation at the receiver of the nearer user is required. Next, we consider the general case with finite UAV speed and flight duration. We show that the optimal UAV trajectory should follow a general HFH structure, i.e., the UAV successively hovers at a pair of optimal initial and final locations above the line segment connecting the two users each with a certain amount of time and flies unidirectionally between them at the maximum speed, and SC is generally needed. Furthermore, when TDMA-based transmission is considered for low-complexity implementation, we show that the optimal UAV trajectory still follows an HFH structure, but the hovering locations can only be those above the two users. Extensive simulation results are provided to verify our analysis, which also reveal useful guidelines to the practical design of UAV trajectory and communication jointly.
Automatic meter reading (AMR) system is known as the communication-based system to read meters. It is an application of smart home with high pertinence and practicability, which can bring on benefits to utility companies (living resources suppliers). The key to designing and implementing an AMR system is communication. Many communication modes have been proposed for AMR system. This paper proposes a ZigBee and Image Picking based Automatic Meter Reading System (ZIP-AMRS) and introduces its implementation in details. As its name suggests, the system uses ZigBee network and image picking technology to collect meter data. Tree routing protocol and end-to-end acknowledge mechanism are adopted to ensure reliable transmission. We installed and verified ZIP-AMRS in an office building, and got the real-time meter picture.
