The concept of an integrated terrestrial/land mobile satellite system

Potential satellite markets in the public safety (disaster relief, emergency medical, and law enforcement) and common carrier (mobile radio telephone) service areas are identified. The public mobile telephone segment is then examined to illustrate a methodology for identifying a potential satellite addressable market, including capacity requirements for roughly sizing a satellite. It is postulated that satellites could serve this lower density (mobiles per square kilometer), thin-route market at a competitive cost and thus complement terrestrial systems in the urban and more densely populated areas to provide an integrated nationwide mobile service.     

An outband paging protocol for energy-efficient mobile communications

A new protocol is proposed for reducing the power consumption of battery-powered terminals in a mobile computing environment. We exploit the fact that, in a mobile data network, mobile terminals do not continuously receive data and therefore they need not continuously operate their receivers. Nevertheless, they need to check their traffic condition periodically, that is, whether there are pending data for them or not. The proposed energy-efficient protocol is based on a paging procedure wherein a dedicated channel is used to alert (page) terminals with pending traffic. Each terminal may check its traffic condition whenever it decides to by monitoring the paging channel. The protocol is evaluated through an approximated theoretical model and through computer simulation. We focus on deriving approximate formulas for the mean message delay, the message delay variance and the power consumption. It is shown that the proposed protocol can achieve considerable power saving at a cost of increased message delivery delay.     

基于卫星导航定位系统自适应抗干扰控制

在全球卫星导航系统抗干扰问题的研究中,自适应波束形成技术很好地解决了与信号不同来向的干扰的抑制问题。但对与信号同向的窄带干扰抑制程度不够,同时会滤除部分导航信号。针对以上问题,提出了一种改进的自适应波束干扰抑制算法。首先,通过级联IIR格型陷波器预测并抑制与信号同向的窄带干扰,然后,利用基于直接数据域自适应波束形成技术抑制剩余的宽带干扰。该改进算法能够有效的滤除窄带和宽带干扰,提升卫星导航系统的抗干扰性能,并在实际卫星通信应用中更具处理的实时性。最后,通过仿真实验证明了该算法的可行性。     

浅谈卫星广播电视系统的接收天线

分析了前馈式抛物面天线和后馈式抛物面天线主要部件（如反射面、馈源喇叭、极化变换器、圆矩匹配器等）的工作原理，并讨论了天线的主要指标：增益、旁瓣特性、噪声温度和极化轴比。     

A narrowband, high capacity integrated voice/data mobile radiosystem for dispatch-related broadcast applications

This paper presents the design and performance analysis of a narrowband, mobile radio system optimized for dispatch-oriented broadcast applications in the 450 and 800 MHz frequency bands. The proposed system is significant since present-generation systems have proven incapable of providing the increased capacity demanded by new data services such as mobile data terminals, automatic vehicle location, and mobile facsimile. The centerpieces of the proposed design are a dynamic multiplexing technique known as packetized data, voice dedicated (PDVD) burst switching, which allows transmission of data within the silence gaps inherent in speech, and a noncausal signal processing technique called lookahead, which provides the data sources with advance knowledge of where the silence gaps will occur. Simulation results are given for two dispatch-oriented broadcast applications with widely differing traffic statistics, showing the flexibility and efficiency of the proposed system. The results show that for either application, the proposed integrated voice/data system can be retrofitted into existing 450 and 800 MHz public and private land mobile radio channels and, compared to conventional voice-only systems, can provide the user with full data services plus a tripling of voice capacity     

Android移动端电视直播系统的设计与实现

以移动流媒体体系结构和流媒体传输控制协议族为基础,在家庭电视机顶盒和无线路由器的基础上,设计一种基于Android系统框架的电视直播系统.机顶盒通过DVB-C获取稳定的数字信号然后硬转码把音视频数据编码成适合移动端播放的AAC和H.264格式并通过HLS协议实现移动端高清电视直播.经验证,该系统可以在现有的家庭多媒体资源基础上实现移动端电视节目的高清同步观看,具有很好的可行性和商业价值.     

北斗导航系统的移动导航定位终端设计分析

卫星定位导航技术目前应用极为广泛,与人民生活息息相关,在手机定位、精准授时、汽车导航、智能交通、智能监控、智能家居、国际救援等等领域应用比较成熟。文章介绍了北斗导航系统的移动导航定位终端的分类和北斗定位基本原理、结构;设计了北斗导航系统的移动导航定位终端,给出了设计的结构、硬件电路以及操作系统。     

An integrated voice/data system for mobile indoor radio networks

A centralized, integrated voice/data radio network for fading multipath indoor radio channels is proposed and analyzed. The packets of voice and data are integrated through a movable boundary method. The uplink channel access uses a framed-polling protocol whereas the downlink uses a time-division multiple-access (TDMA) scheme. This system dynamically switches between two transmission rates and uses multiple antennas to maximize the throughput in the fading multipath indoor environment. Throughput and delay characteristics of the system are analyzed using four different techniques. The results are compared with those of Monte Carlo computer simulations. A simple relationship between the number of voice terminals and the throughput of the data traffic are derived for an upper bound of 10-ms delay for the data packets     

An efficient reliable one-hop broadcast in mobile ad hoc networks

A reliable one-hop broadcast is a fundamental communication primitive in mobile ad hoc networks in which a message from the source node is guaranteed to be delivered to all nodes within the source node’s transmission range. Despite the importance of it, reliable one-hop broadcast is not easy to accomplish due to collisions in wireless networks known as Hidden Terminal Problem. This paper presents a MAC protocol that not only guarantees reliable one-hop broadcast but also achieves it efficiently by exploring as many simultaneous executions of the communication as possible. In addition to the data packets, the proposed algorithm utilizes the control packets that prevent packet collisions, and at the same time, make the simultaneous communications possible to improve the network throughput. Simulation results show the effectiveness of the proposed algorithm.     

北斗/罗兰组合导航系统中伪距导航定位解算新算法研究

为提高北斗／罗兰组合导航系统伪距导航定位解算的精度和改善对动态目标的实时跟踪,本文提出了一种新方法,采用镜像映射法解具有病态的矛盾方程组以提高精度,以及将伪距导航定位解算方程模型转换为具有贯序输入输出数据的系统辨识模型,然后用递推最小二乘法,对所求的北斗／罗兰组合导航系统伪距导航定位信息一接收机的三维位置参数和时钟误差参数进行动态快速实时估计。     

An integrated voice and data multiple-access scheme for a land-mobile satellite system

A Land-Mobile Satellite System (LMSS) is a satellite-based communications network which provides voice and data communications to mobile users in a vast geographical area. By placing a "relay tower" at a height of 22300 mi, an LMSS can provide ubiquitous radio communication to vehicles roaming in remote or thinly populated area. LMSS is capable of supporting a variety of services, such as two-way alphanumeric service, paging service, full-duplex voice service, and half-duplex dispatch service. A Network Management Center (NMC) will handle the channel requests, channel assignments, and in general the network control functions. A pool of channels is managed at the NMC to be shared by all mobile users. An integrated demand-assigned multiple-access protocol has been developed for the experimental LMSS. The pool of channels is divided into reservation channels and information channels. The information channels can be assigned by the NMC to be either voice channels or data channels. Each mobile user must send a request through one of the reservation channels to the NMC via the ALOHA random-access scheme. Once the request is received and processed, the NMC will examine the current traffic condition and assign an information channel to the user. NMC will periodically update the partitions between the reservation channels, voice channels, and data channels to optimize system performance. Data channel requests are queued at the NMC while voice channel requests are blocked calls cleared. Various operational scenarios have been investigated. Tradeoffs between the data and voice users for a given delay requirement and a given voice call blocking probability have been studied. In addition, performance impacts of such technological advancements as satellite on-board switching and variable bandwidth assignment are discussed.     

一种适用于GEO卫星移动通信系统流业务的无线资源管理方法

提出了一种适用于GEO卫星移动通信系统流业务的无线资源管理方法,保障在共享信道上传输的流业务的速率和延时需求.该方法由3个功能实体组成：1）接纳控制/信道分配实体,用于接受或拒绝新的资源请求;2）分组调度实体,负责为每个连接提供所需的传输服务,满足传输速率要求;3）质量控制实体,监测目前系统为当前服务提供的QoS是否与签约QoS一致.在NS2仿真平台建立了相应的系统模型,进行了动态仿真.     

卫星导航与5G移动通信融合架构与关键技术

随着我国社会经济科技等领域的飞速发展,卫星导航技术在经济建设中占有越来越重要的位置.同时,以提供定位服务的小区密集化、大规模阵列天线等技术为代表的5G通信为导航通信一体化奠定了基础.卫星导航和5G移动通信技术的融合,将极大地扩展导航的范围,提升导航的精度.本文综合国内外最新研究成果,首先提出了卫星导航与5G移动通信融合体系架构;然后在总结A-GNSS技术的基础上,阐述了基于5G的A-GNSS系统架构和关键技术;最后,在介绍5G基站定位技术的基础上,全面详细地阐述了卫星导航与5G混合定位架构和关键技术.     

VHF数据通信在卫星导航系统中的应用

数据链技术是国际民航未来航行系统中的一个重要环节,对CNS／ATM中通信,导航和监视等各个领域提供基础支持。对导航而言,近年来蓬勃发展的GNSS（卫星导航）技术给全球航行系统带来了深刻的变革。为解决单纯的GNSS（GPS,GLONASS等）信号精度和完好性等方面的问题,出现了GBAS,SBAS和ABAS等一系列增强系统。这其中,数据链技术无不扮演了一个重要的角色。本文拟以陆基增强系统（GBAS）为例,对数据通信链技术在卫星导航中的应用做一个论述。１．GBAS（陆基增强系统）的提出GPS等卫星导航技术是利用一定数量的卫星数据…     

车载接收卫星电视直播节目的天线自动跟踪系统

利用姿态测量技术，用陀螺传感器对汽车行驶中航向角的变化量进行测量。单片机对测得的数据进行处理后控制伺服系统驱动伺服马达，转动天线使得天线中心轴始终对准卫星，确保汽车在行驶过程中接收卫星电视直播节目能正常工作，并对长时间行驶累积的误差进行修正。     

基于MEMS技术的微型组合导航传感系统研究

大型无人机的航姿系统、大气数据系统及惯性导航系统等导航设备因结构复杂、体积、重量大及价格昂贵等因素,无法在微型无人机(MAV)上使用.本文采用PC104嵌入式微机、MEMS集成技术、数据融合技术及GALILEO技术,实现了一种用于微型无人机的微型组合导航传感系统.以C语言及汇编语言作为系统软件的开发平台,增强了系统软件的可维护性及可扩展性.该系统集飞机航姿系统、大气数据系统、惯性导航传感器等功能于一身.实验室和现场的测试结果表明,该传感系统提高了导航精度,简化了结构,缩小了体积,减轻了重量.该系统拟用于微型无人机.     

Communicating via a processing broadcast satellite

Three dependent users are physically separated but communicate with each other via a satellite. Each user generates data which it stores locally. In addition, each user sends a message to the satellite. The satellite processes the messages received from the users and broadcasts one common message to all three users. Each user must be capable of reconstructing the data of the other two users based upon the broadcast message and its own stored data. Our problem is to determine the minimum amount of information which must be transmitted to and from the satellite. The solution to this problem is obtained for the case where subsequent data triples that are produced by the users are independent and identically distributed. The three symbols within each triple are assumed to be dependent. Crucial for the solution is an achievability proof that involves cascaded Slepian-Wolf (1973) source coding     

一种新型GPS/DR组合导航系统

利用三个陀螺仪和一个里程计提出一种新型GPS/DR组合导航系统。首先推导了这种组合导航系统的状态方程,然后给出了松组合方式的滤波方程。最后用实测算例对这种新型组合导航系统进行了验证,结果表明,相比于SINS系统、传统的DR系统,这种DR系统在车载系统应用中具有更好的优势;而且这种组合导航系统能够很好地提高单一导航系统的导航精度。