Bat algorithm–based beamforming for mmWave massive MIMO systems

In this paper, an optimized analog beamforming scheme for millimeter‐wave (mmWave) massive MIMO system is presented. This scheme aims to achieve the near‐optimal performance.by searching for the optimized combination of analog precoder and combiner. In order to compensate for the occurrence of attenuation in the magnitude of mmWave signals, the codebook‐dependent analog beamforming in conjunction with precoding at transmitting end and combining signals at the receiving end is utilized. Nonetheless, the existing and traditional beamforming schemes involve a more difficult and complicated search for the optimal combination of analog precoder/combiner matrices from predefined codebooks. To solve this problem, we have referred to a modified bat algorithm to find the optimal combination value. This algorithm will explore the possible pairs of analog precoder/combiner as a way to come up with the best match in order to attain near‐optimal performance. The analysis shows that the optimized beamforming scheme presented in this paper can improve the performance that is very close to the beam steering benchmark that we have considered.     

Pilot contamination mitigation based on antenna subset transmission for mmWave massive MIMO

This paper tackles the problem of pilot contamination (PC) in mmWave Massive MIMO cellular systems. We propose an analog precoder based on antenna subset transmission technique to mitigate the PC. This technique ensures the interfering signal to become noise‐like signal thus helping a more efficient estimation of channel coefficients. Also, this strategy is low cost and introduces no complexity load. The result shows the effectiveness of the proposed precoder to mitigate PC issue.     

Performance analysis of large-scale MIMO system for wireless backhaul network

In this paper, we present a performance analysis of large-scale multi-input multi-output (MIMO) systems for wireless backhaul networks. We focus on fully connected N nodes in a wireless meshed and multi-hop network topology. We also consider a large number of antennas at both the receiver and transmitter. We investigate the transmission schemes to support fully connected N nodes for half-duplex and full-duplex transmission, analyze the achievable ergodic sum rate among N nodes, and propose a closed-form expression of the achievable ergodic sum rate for each scheme. Furthermore, we present numerical evaluation results and compare the resuts with closed-form expressions.     

Saturation performance analysis of directional CSMA/CA in mmWave WPANs

The millimeter‐wave (mmWave) band offers the potential for multi‐gigabit indoor wireless personal area networks (WPANs). However, there are problems such as the short wavelength and high propagation losses. In order to compensate for these, it is highly recommended to use directional antennas at the physical layer. In this paper, directional carrier sense multiple access/collision avoidance (CSMA/CA) is analyzed in IEEE 802.15.3c, a standard for mmWave WPANs, under a saturated environment. A Markov chain model is presented and analyzed for the no‐acknowledgment (No‐ACK) mode. For the analysis, the device interaction is considered using directional antennas over a shared channel. A Markov chain model is presented in which the features of IEEE 802.15.3c such as backoff counter freezing and the effects of using directional antennas are incorporated. The maximal number of frames that can be transmitted concurrently and successfully is derived by an algorithm, and the system throughput and the average transmission delay are obtained in the closed forms. Numerical results show that the effects of using directional antennas in CSMA/CA and the overall analysis are verified by the simulation. The obtained results illustrate the physical layer impact on the CSMA/CA medium access control protocol, and these insights can be helpful in developing a medium access control protocol for enhancing the performance of mmWave WPANs. Copyright © 2011 John Wiley & Sons, Ltd.     

基于人工智能的基站巡检应用实践

运营商传统的通信基站巡检通过人工方式进行,不仅耗费人力,还存在安全性不高、结果不可验证、信息不全面等问题。主要介绍人工智能技术在运营商基站日常巡检领域的应用实践及面临的挑战,包括智能巡检技术及产业发展概况、运营商传统巡检向智能化转化的需求动力、智能巡检解决方案、效果评价与数据分析等。在此基础上,探讨了电信运营商未来开展AI自动巡检的应用场景与服务模式,提出了智能巡检平台的部署方案建议。     

基于随机几何的毫米波自回传网络中断性能分析

为精确分析具有线性视距(LOS)传输特性的5G 毫米波自回传网络(mW-SBN)中阻塞问题的中断性能,提出了基于随机几何和随机形状理论的毫米波自回传网络中断分析方法。推导了毫米波宏基站(MBS)和微小区(SC)之间距离的统计特性,以及mW-SBN 回传链路中断概率的闭型表达式,得出了mW-SBN 网络参数与回传链路中断概率的关系式。仿真和计算结果表明:mW-SBN 回传链路中断概率主要受MBS 与SC 之间距离及表征阻塞物大小和形状的参数等系统参数影响,仿真结果也印证了得出的理论分析。     

基于ZXJ10平台的移动交换机

本文介绍了在 ZXJ10交换机平台上开发具有 GSM 功能的移动交换机的框架结构,以及 ZXJM-BC 移动交换机的基本特点。     

Radio versus backhaul bottlenecks: an integrated quality of service provisioning approach for small cell gateways

Small cell traffic is expected to experience a continuous increase during the upcoming years, and thus, backhauling challenges should be timely addressed. Regardless the fact that radio resource management continues to be a major research problem in coexisting heterogeneous wireless networks, a mentality shift is observed in the research community towards dealing with wired backhaul bottleneck situations, too. Hence, specific small cell network deployments such as the one considered in this paper have to adopt an integrated quality of service provisioning approach. A femtocell utilizing an existing internet protocol (IP) infrastructure has usually to share the backhaul capacity with several IP networks. As these networks do not provide an efficient admission control process, the capacity allocated to the femtocell can fluctuate unpredictably over time. As a remedy, we propose a scheme for small cells' efficient integration (SCEI) in the IP infrastructure. SCEI is able to manage the total incoming traffic load and continuously adjust the distribution of the backhaul capacity among the existing networks. Simulation results show that SCEI provides significantly higher utilization of the backhaul capacity and more resilience regarding quality‐of‐service‐related metrics in overload state situations compared with state‐of‐the‐art hybrid partitioning techniques. Finally, this work also provides hints on ways that SCEI concepts can be applicable in more future Internet and small cell network deployment variants. Copyright © 2013 John Wiley & Sons, Ltd.     

有人/无人机协同作战

介绍了国外有人/无人机协同作战的发展概况,给出了有人/无人机之间协同作战的几种可能模式,并分析了有人机实现无人机地面控制站功能的可行性。相关结论对该领域技术人员开展有人/无人机协同作战研究具有重要意义。     

长途客车视频监控系统的设计与实现

以移动视频监控为出发点,结合音视频编解码技术、GPS卫星定位、3G无线网络传输等技术,实现对长途客车的实时定位和视频监控。利用无线摄像机、拾音器等车载前端设备进行音视频信息采集,存储在本地磁盘或通过无线网络上传。客车配备自动报警装置,以便报警信息及抓取的图像能够上传至监控中心及时处理。利用集成了语音模块的车载显示屏,实现行车安全提醒。通过内置GPS模块的车载主机,有效节约3G流量。     

GSM移动台的软件设计

本文简要介绍了 GSM 系统中移动台软件的功能、模块结构及其运行流程。着重说明了主要模块的基本功能,并以呼叫建立为例对移动台与系统基站的信令交换进行了较为详细的论述。     

基于地理信息技术的山区农村无线通信基站选址研究

我国山区农村由于地形复杂,移动通信基站建设一直是一个困扰工程技术人员的难题.本文提出了一套基于地理信息系统(GIS)技术的山区基站选址技术方案,并结合广东茂名移动公司系统建设的实践,论证了方案的可行性和正确性.同时本文还对GIS在移动通信领域的应用前景做了初步的预测.     

Proportionally fair load balancing with statistical quality of service provisioning for aerial base stations

Aerial base stations (ABSs) seem promising to enhance the coverage and capacity of fifth-generation and upcoming networks. With the flexible mobility of ABSs, they can be positioned in air to maximize the number of users served with a guaranteed quality of service (QoS). However, ABSs may be overloaded or underutilized given inefficient placement, and user association has not been well addressed. Hence, we propose a three-dimensional ABS placement scheme with a delay-QoS-driven user association to balance loading among ABSs. First, a load balancing utility function is designed based on proportional fairness. Then, an optimization problem for joint ABS placement and user association is formulated to maximize the utility function subject to statistical delay QoS requirements and ABS collision avoidance constraints. To solve this problem, we introduce an efficient modified gray wolf optimizer for ABS placement with a greedy user association strategy. Simulation results demonstrate that the proposed scheme outperforms baselines in terms of load balancing and delay QoS provisioning.     

基于双连接和回传带宽配置的系统吞吐量效用和最大化算法

针对双连接可行的异构无线网络中关于用户关联和回传带宽配置的联合优化问题,构建了一个新的网络吞吐量效用和最大化框架。将该联合优化问题建模为一个非凸的混合整数分式优化问题。为了便于求解,首先将原建模问题进行去分式化转换,然后针对转换后依旧非凸的混合整数非线性优化问题,将其分解为两个优化子问题分别求解。通过固定用户关联变量,得到了最优的回传带宽配置机制;通过固定回传带宽配置因子变量,提出一个有效的迭代算法求解双连接可行的用户关联子问题。相比固定的回传带宽配置机制,所提算法可以获得最优的回传单位带宽配置因子值,同时拥有最优的系统吞吐量和系统吞吐量效用和性能。     

UAV-based LoRaWAN flying gateway for the internet of flying things

The Internet of Things (IoT) is one of the paradigms related to the evolution of telecommunication networks which is contributing to the evolution of numerous use cases, such as smart city and smart agriculture. However, the current communication infrastructure and wireless communication technologies are not always able to guarantee a proper service for these IoT scenarios. Smart solutions are needed to overcome current terrestrial network limitations offering a cost-effective way to extend the current terrestrial network coverage. For example, temporary extensions “on-request” of the terrestrial infrastructure may be a viable solution to allow collecting data generated by nodes outside the current network coverage. Flying objects can help achieve this goal. Various studies supported the use of unmanned aerial vehicles (UAVs) as intermediate nodes between IoT devices and the network. However, such solutions have not been exhaustively tested yet in real-case scenarios. This paper proposes an efficient solution to collect data from multiple IoT sensors in rural and remote areas based on UAVs. It describes the implementation of the proposed UAV-based Long RangeWide Area Network (LoRaWAN) flying gateway able to collect data directly from LoRaWAN sensors during its flight, keep them stored in an onboard memory, and forward them at the end of its flying path to a platform where the authorized users can access them. A prototype of the gateway has been developed to assess the proposed solution through both indoor and outdoor tests aiming to test its feasibility both in terms of communication performance and UAV-required hardware resources.     

直放站在移动通信网中存在的问题及对策

直放站作为移动通信基站系统的有效补充,可以经济、迅速、有效地填补盲区,改善网络质量,带来可观的经济效益,在网络中得到广泛的应用。但是由于CDMA网络自身的特性,CDMA直放站在使用过程中,会出现各种各样的问题。就CDMA直放站在应用过程中存在选址不当造成掉话率高、直放站质量原因引起的问题、直放站设计不当引发问题等提出相应的解决办法。     

移动通信基站天线测试中时域门最佳设置研究

针对移动通信基站天线测试系统场地反射波的干扰问题,在此提出了一种基于矢量网络分析仪时域门设置的反射波消除方法。首先分析了不同种类的基站天线和测试时天线所处的状态参数,然后通过分析其对时域门选择的影响,得出了时域门设置需要满足的条件,最后综合权衡时域门参数的设置,将时域门设置到最佳状态。实测数据表明,该方法能够有效地消除测试场地反射波的影响,保证被测天线的测量准确性,仿真验证了方法的正确性与有效性。     

基于GIS的移动通信基站管理系统

使用VB.Net和Mapinfo的MapX组件,结合SQL Server2000数据库,实现了移动通信基站的可视化管理。将移动基站分布信息、呼叫信息、切换信息等在电子地图上以不同的视图标示,为移动基站网络建设的优化配置提供一定的支持,也使运维人员对系统的管理和维护更加直观。     

Age of information analysis for internet of things information status update system with cellular backhaul and dedicated energy harvesting beacons

The Internet of Things (IoT) that is usually deployed with the assistance of cellular backhaul and energy harvesting (EH) is characterized by the status update freshness. However, the traditional nature EH results in the loss of information freshness due to the randomness of nature energy process. Although using wireless energy transferring (WET) to charge sensors can overcome this problem, this method has low-energy efficiency. With these considerations, this paper proposes a novel IoT system under cellular communication scenario by simultaneously exploiting the nature EH and WET. The proposed IoT system is consisted of a cellular backhaul subsystem, a wireless EH and transferring (WEHT) subsystem, and a wireless sensor status update subsystem. The WEHT subsystem employs the dedicated power beacons harvesting energy from natural energy source and transferring the harvested energy to sensor. For the proposed IoT system, this paper first investigates the WEHT subsystem and constructs the Markov Chain (MC) of discrete energy states as well as the MC state transition matrix. Second, the average AoI and peak AoI (PAoI) are formulated by separately considering cellular backhaul and EHTBs. The AoI (PAoI) comparison shows that the proposed EHTB-based IoT system can outperform the conventional non-EHTB one where the sensor directly harvests energy from natural source. At the same time, the numerical results exploit the impact of system parameters on AoI and PAoI, respectively. It is found that there exists a trade-off between the nature energy arrival and EHTB energy transfer so that the average minimum AoI and PAoI are achieved.     

无人机对IMSE通信干扰仿真研究

基于高层体系结构（HLA）技术,设计了无人机对改进型移动用户设备（IMSE）通信干扰仿真系统,利用该仿真系统进行了仿真,得出了无人机采用不同飞行高度进行通信干扰时IMSE网络性能的指标参数,为研究无人机对IMSE实施通信干扰效果提供了一种有效的方法。