DTV repeater emission mask analysis

Terrestrial digital television (DTV) requires careful planning in the allocation of RF channels, especially during the transition period when intermixing both analog and digital signals in the same coverage area. One important issue to consider is adjacent channel interference, which limits the number of RF channels utilized in any given area. This issue is important in the deployment of not only full service stations, but also of secondary stations such as translators, on-channel repeaters, and low power television stations. Full service stations have FCC rules that limit the amount of adjacent channel splatter by requiring the splatter energy to remain below a rigid emission mask. Currently there are no FCC rules for translators and low power television stations. The paper discusses typical DTV transmitter splatter sidebands and their causes, as well as specific methods for interference analysis from adjacent channel DTV splatter into adjacent NTSC or DTV signals. Two rigid emission masks ("simple" and "stringent") are proposed and evaluated. Several filter designs are computer simulated and analyzed for minimizing adjacent channel splatter interference as well as in-band DTV signal degradation. Linear pre-correction techniques are analyzed for various length (15-tap and 31-tap) transversal filter equalizers. The simulation is verified by measuring and evaluating DTV system performance for two hardware band-pass filters individually placed at the output of a low power (30 W average) transmitter.     

Development of Ka-band 100-W peak power MMPM

Various types of millimeter-wave radio systems are being developed for strong broadband service demands such as fixed wireless access, local multipoint distribution service, as well as satellite communications. In each system, the higher data rate transmission requires more powerful amplification devices. This paper describes the development of a Ka-band 100-W peak power millimeter-wave power module, traveling wave tube-based millimeter-wave amplification module, used for millimeter-wave fixed wireless access base stations and Ka-band satellite Internet terminals.     

Energy payback time of the high‐concentration PV system FLATCON®

The ecological benefit and sustainability of a new energy technology and its potential to reduce CO₂ emissions depend strongly on the amount of energy embodied in the materials and production processes. The energy payback time is a measure for the amount of time that a renewable energy system has to operate until the energy involved in its complete life‐cycle is regenerated. In this paper, the energy payback time of the high‐concentration photovoltaic system FLATCON® using III–V semiconductor multi‐junction solar cells has been evaluated. Considering the energy demand for the system manufacturing, including transportation, balance of system and system losses, the energy payback time turns out to be as low as 8–10 months for a FLATCON® concentrator built in Germany and operated in Spain. The energy payback time rises slightly to 12 to 16 months for a system installed in Germany. The main energy demand in the production of such a high‐concentration photovoltaic system was found to be the zinced steel for the tracking unit. Copyright © 2005 John Wiley & Sons, Ltd.     

Shallow water acoustic networks

Underwater acoustic networks are generally formed by acoustically connected ocean bottom sensor nodes, autonomous underwater vehicles (AUVs), and surface stations that serve as gateways and provide radio communication links to on-shore stations. The quality of service of such networks is limited by the low bandwidth of acoustic transmission channels, high latency resulting from the slow propagation of sound, and elevated noise levels in some environments. The long-term goal in the design of underwater acoustic networks is to provide for a self-configuring network of distributed nodes with network links that automatically adapt to the environment through selection of the optimum system parameters. This article considers several aspects in the design of shallow water acoustic networks that maximize throughput and reliability while minimizing power consumption     

Sharing issues between FPLMTS and fixed services

Any sharing between future public land mobile telecommunication systems (FPLMTS) and fixed services must be on the basis of maintaining high reliability and performance for both services. The focus of this article is to examine the following. Can mobile and fixed systems share the same frequency band? How much unwanted signal power is received by each system from the other? How does the unwanted signal power vary as mobile users roam in an area covered by the main-beam and the sidelobes of the fixed service? What effects do the parameters of FPLMTS (transmitter power, bandwidth, etc.) and the parameters of the fixed service (antenna directivity, power, bandwidth, etc.) have on the unwanted signal power levels? How is the unwanted power level affected by the path geometry, in particular fixed service antenna height and propagation conditions (congested areas) between the mobile and fixed stations?     

Microcell Automatic Propagation Measuring System and Service-Area Evaluation

Microcellular systems, such as the Personal Handyphone System, need a large number of cell stations to cover service areas. Therefore, a quick and efficient means to evaluate a service area is of great importance. This paper describes a new microcell automatic propagation measuring system (MAPS) employing location recognition and cell-site identification. Service-area evaluation of microcellular systems based on field experiments in urban and suburban areas is also described. Measurement location is recognized using the Global Positioning System, an optical-fiber gyroscope, and a vehicle speed sensor. Cell-site identification is determined through cell-station ID. Computer-aided propagation-data processing using a map database is adopted for service area mapping. This enables evaluation of cell overlaps, out-of-service areas, cell shapes, interference, etc. This system greatly improves the efficiency in propagation measurement and evaluation of service area for microcellular systems.     

安徽省综合观测资料基础数据库系统设计与实现

为了实现安徽省国家级、区域级自动气象站,自动土壤水分观测站等各类综合观测资料的数据采集存储、加工处理、报文生成等功能,利用最新数据库镜像、数据同步技术,设计、建成了一套高效、稳定、安全、易用的省级综合观测资料基础数据库系统。该数据库系统提供API接口和Web Service接口两种数据接口访问模式,可满足现有气象业务、科研对实时综合观测数据的服务需求。     

Factors Affecting the Choice of Frequency Band for DBS Systems in the United States

The prospective operator of a system intended primarily for broadcasting directly to homes in the United States (as opposed to distributing programming to CATV head ends or terrestrial broadcasting stations) must choose between two frequency bands: 12.2-12.7 GHz and 11.7-12.2 GHz. The first of these bands is allocated to the broadcasting-satellite service (BSS) with the assignment of frequencies, orbital positions, sense of polarization, and maximum radiated power to service areas governed by an international plan. The other band is allocated to the fixed-satellite service (FSS), but with a footnote permitting use of transponders already authorized in the FSS to be used for BSS transmissions under certain constraints on maximum radiated power and mutual interference. This paper examines the differences between the two frequency bands in terms of their impact on a number of factors of practical interest to a DBS system operator.     

Application of system design principles to high channel density air-ground telephone service

Directed toward FCC Docket 16073 on air-ground telephone service by single sideband, a study has been made of a high channel density 450-MHz communication system employing 6 groups of 10 channels each in a 300-kHz band. To accomplish necessary tolerance to out-of-band transmitter radiation, all mobile stations need automatic power output control. Other important system features, such as privacy and first come, first serve from queue when all busy, result from the use of a common data channel. With the accomplishment of the necessary equipment and logical techniques, a communication system of much greater frequency utilization appears technically and economically feasible.     

Cognitive Radio with Reinforcement Learning Applied to Multicast Downlink Transmission with Power Adjustment

This paper shows how channel assignment in multicast terrestrial communication systems with distributed channel occupancy detection can be improved using intelligence based on reinforcement learning and transmitter power adjustment. It is shown how such schemes greatly reduce the number of reassignments and improve the dropping probability, at the expense of increased blocking. It is found that using different minimum quality of service threshold percentages can partly control and improve the performance, in place of the more traditional SINR threshold levels. The paper also shows how a power adjustment technique is developed which significantly reduces the level of overlap between adjacent base stations, and further reduces interference and transmitter power.     

Dynamic Data Rate and Transmit Power Adjustment in IEEE 802.11 Wireless LANs

In this paper a novel link adaptation algorithm is proposed that is capable of adjusting the transmit power level and the data rate jointly to the radio channel conditions. The proposed method relies solely on link quality information available at the transmitter by employing the reception or non-reception of the acknowledgment frames as a measure of the channel quality with respect to the power level and data rate. The method is fully compatible with the 802.11 wireless LAN standard. In contrast to many other proposals, it neither relies on the RTS/CTS protocol nor requires a feedback channel to transmit link-quality estimates from the receiver to the transmitter. Different strategies for optimizing the data rate and power level are given. These depend on the scenarios considered, the number of active stations, and the service requirements. The two main strategies are either to drive the system towards the highest possible data rate and adjust the rate and power levels accordingly (“high-performance” mode) or to focus on power saving, possibly trading this for other performance criteria such as throughput or delay performance (“low-power” mode). Other special cases, such as power or rate only adaptation, are also discussed. It can be shown that in most cases the best choice for achieving low transfer times, maximizing throughput, and alleviating the hidden terminal problem is to transmit at the highest possible rates and with high power levels. This “high-performance” mode of operation also minimizes the transmission times, which in turn maximizes the time for putting idling components into a sleep mode, thereby minimizing the overall power consumption.     

Spectrum resource allocation for wireless packet access withapplication to advanced cellular Internet service

The advanced cellular Internet service (ACIS) is targeted for applications such as Web browsing with a peak downlink transmission rate on the order of 1-2 Mbits/s using a wide-area cellular infrastructure. In order to provide bandwidth on demand using scarce radio spectrum, the medium-access control (MAC) protocol must: 1) handle dynamic and diverse traffic with high throughput, and 2) efficiently reuse limited spectrum with high peak rates and good quality. Most of the existing approaches do not sufficiently address the second aspect. This paper proposes a dynamic packet assignment (DPA) scheme which, without coordinating base stations, allocates spectrum on demand with no collisions and low interference to provide high downlink throughput. Interference sensing and priority ordering are employed to reduce interference probability. A staggered frame assignment schedule is also proposed to prevent adjacent base stations from allocating the same channel to multiple mobiles at the same time. Simulation results based on a packet data traffic model derived from wide-area network traffic statistics, which exhibit a “self-similar” property when aggregating multiple sources, confirm that this method is able to reuse spectrum efficiently in a large cellular system having many users with short active periods. Distributed iterative power control further enhances spectrum efficiency such that the same channel can be simultaneously reused in every base station     

Digital video broadcasting over satellite (DVB‐S): a system for broadcasting and contribution applications

The general system concepts for digital television transmission and broadcasting by satellite, developed within the European digital video broadcasting (DVB) Project and standardized by ETSI are described. The system (EN 300 421) is designed to provide direct‐to‐home (DTH) multi‐programme TV services in the BSS and FSS bands and is addressed to consumer integrated receiver decoders (IRDs), as well as collective antenna systems (SMATV) and cable television head‐end stations, with a likelihood of remodulation. The system operational modes have been extended in 1998 (EN 301 210) to cover also ‘contribution’ applications by satellite, such as conveying vision and sound material between TV studios, or from remote locations directly to the broadcaster's premises through light and portable up‐link terminal digital satellite news gathering (DSNG). The exploitation of the multiplex flexibility allows the use of the transmission capacity for a variety of TV service configurations. The use of flexible and advanced error protection techniques, based on the concatenation of Reed‐Solomon and convolutional codes (with Viterbi decoding), allows optimum adaptation to different satellite transponder characteristics, i.e. bandwidth and power, providing high service quality and availability with small receiving antennas (DTH applications) or transmitting terminals (DSNG applications). Copyright © 2000 John Wiley & Sons, Ltd.     

Taming the dragons-designing danger out of the Hong Kong MTR

The Hong Kong mass transit railway (MTR) was designed to have four routes, of which three are in service so far. It has 39 km of double track and 37 stations and carries up to 90000 passengers per hour in each direction under crush conditions. Design of the system is therefore vital in terms of safety and the stations, trains and power supplies are discussed while considering this aspect     

DS—CDMA系统中的功率分配算法的研究

第三代移动通信系统设计要求支持多媒体通信。由于各个业务在接收端所要求的功率不同,这就要求系统必须进行有效的功率分配。文章提出了一种基于信道特征（如业务量）的功率分配算法,并通过系统分析验证了该算法能确保各种业务的业务质量的同时提高系统的容量。     

Base station location in a cellular CDMA system

We consider a cellular CDMA system in which blocking is enforced when the relative interference exceeds a certain threshold level. This paper addresses a radio network design problem in such a CDMA system. Given the data of call‐traffic distributed over the service area and potential sites of base stations, the objective of the problem is to locate base stations so as to minimize the associated cost for establishing base stations while keeping the probability of blocking under control. We develop an efficient algorithm for solving the design problem. Computational experiments with real‐world data are conducted to show both the efficiency and the practicality of the proposed design method. This revised version was published online in August 2006 with corrections to the Cover Date.     

无线多媒体DS—CDMA系统中的功率分配算法研究

本文提出一种基于信道特征（如业务量）的功率分配算法,并通过系统分析验证了该算法是能很好地在保证各业务的业务质量同时提高系统的容量。     

一种基于MODEM的计算机远程监控系统

介绍一种通过公共电话交换网（PSTN）连接,用于供电系统的计算机远程监控系统。该系统由上位计算机、调制解调器、程控交换机和下位单片机系统组成。系统按分布式结构设计,可实现对多个太阳能供电站点的实时监控,应用于程控交换基站、无线通信基站供电系统的监控。结果证明系统具有操作方便、工作可靠、成本低廉等特点。     

基于GIS智能打点的5G网络投诉“黑点”区域整治研究

基于百度等地图类API服务能力,结合微区域、微网格边界等地理信息系统(GIS)打点数据,以及干扰、容量、故障等网络O域数据,一方面前移至在线客服一线使用,提升5G网络投诉位置的定位精准性、缩短投诉打点时长;另一方面面向网络优化人员,系统自动汇聚5G网络投诉集中的“黑点”区域,形成分级预警整治能力,指导通过新建基站、网络优化等手段解决5G网络问题,提升5G客户满意度。     

Performance study for a microcell hot spot embedded in CDMAmacrocell systems

The code-division multiple-access (CDMA) system can provide more capacity than other systems, and the hierarchical layer of cells is required for system design. However, the problem is whether the same radio frequency (RF) channels used in a CDMA overlayed/underlayed macrocell and microcell structure also obtain a high capacity as in the homogeneous structure. We investigate the interference of uplink and downlink from both the microcell and macrocell under a hierarchical structure. A downlink power control scheme and two power control methods for the uplink are also considered. Performance measures such as blocking probability, C/I, capacity, and service hole area are also obtained by computer simulation. Besides, some extra efforts for a microcell are also noted, such as more power need to be transmitted by a microcell base station (BS) if the same RF channels are used in the hierarchical structure. The capacities of macrocell and microcell in the overlaying/underlaying structure are limited by the uplink and downlink, respectively. With downlink power control, the microcellular capacity can be increased. However, the combination of downlink power control for the microcell and C/I uplink power control for the macrocell causes the overall system capacity to significantly increase