基于“北斗”的语音通讯传输

北斗卫星导航系统是我国自主研发且具有通信能力的区域性卫星导航系统,具有其他导航系统不具备的双向短报文通信功能。针对用户在抢险救灾等各种复杂环境中对语音通讯的需要,在北斗卫星导航系统短报文通信功能的基础上,设计一种可用于语音传输的系统。基于现有的北斗通信终端通过硬件扩展实现语音通信传输功能;通过语音压缩技术解决大量语音数据有效传输的问题。结合试验对语音数据进行分析,系统能顺利进行语音通信,语音质量达到预期效果。     

北斗短报文可靠性传输机制在人防中的应用

受限于环境、通信频度和通信容量等因素，基于北斗的人防警报控制系统存在数据发送延迟高、排队较长和丢包等问题，无法保证警报控制的实时性和可靠性。为此，提出了一种实现北斗三号短报文可靠传输的方法。在北斗人防通信协议中增加“丢包率控制”字段，减少发送图片/语音等长数据时不必要的丢包重传次数，减少传输时间；在此基础上，利用北斗三号指挥型用户机阵列实现轮询发送人防统控通信数据，有效解决北斗通信频度的限制因素，提高人防系统数据传输的通信效率。通过采用差异化可靠通信机制，在不影响用户体验的条件下，极大地提高了消息的实时性和可靠性。对比实验结果表明，该方法可以有效提升人防统控系统的可靠性和传输效率。     

基于北斗卫星的太阳能资源监测系统设计

在野外设置的太阳能资源监测站,由于无公网信号,往往面临着数据无法远程传输的问题。针对此问题设计基于北斗卫星的太阳能资源监测系统。系统结构由单片机控制器、北斗通信模块、传感器检测模块、太阳能电池管理电路组成。系统电源采用具有MPPT功能的CN3767芯片管理太阳能电池板充电电路。太阳能资源监测系统采集到的数据,按照根据北斗短报文的通信速率及容量特点设定的数据协议进行编码,然后利用北斗模块的短报文功能进行数据的传输。设计的太阳能资源监测系统完成了现场太阳能资源的监测及数据的传输功能。该系统实现了偏远地区太阳能资源监测站的自动化、数字化管理需求。     

基于国密算法的北斗短报文加密方案

北斗短报文是北斗导航系统的特色功能,它可以实现用户间双向短消息通信,具有覆盖范围广、无通信盲区、通信距离远和实现简单等特点,在交通运输、农业渔业、水文监测、气象预报、救灾减灾、公共安全、能源等多个行业拥有广泛的应用.但是北斗卫星导航系统针对民用应用通信的安全非常薄弱,应用数据采用明文传输,存在信息泄露和非法篡改的安全风...     

语音信号的数据压缩技术

1 前言多媒体通信是数据通信、语音通信和图像通信的结合,因此有大量的数据需要存储、处理和传输。尤其是语音和图像信息,数据量庞大,对微机容量和传输信道带宽都有很高要求,必须采用数据压缩技术对信号进行压缩存储和传输。数据压缩作     

北斗RDSS授时性能分析

目前,我国已经发射了北斗三号卫星无线电测定业务(Radio Determination Satellite Service, RDSS)的59,60和61号3颗GEO卫星,加上原有的北斗二号的1～5号GEO卫星,总共有8颗GEO卫星为导航用户提供导航定位、短报文通信、卫星授时和星基增强等RDSS业务服务。由于GEO卫星距离地表距离超过3.6万km,卫星属于高轨卫星,其服务质量受到轨道精度、配置星载原子钟、大气延迟和卫星硬件延迟等影响严重。针对北斗RDSS授时相关研究目前鲜有报道,尤其平稳过渡波束和北斗三号卫星的相关内容尚未开展研究。深入分析了北斗RDSS提供的单向授时和双向授时服务质量,研究目标包括目前可用的全部北斗二号卫星、平稳过渡波束和北斗三号卫星。基于北斗RDSS授时接收机连续30 d的北斗实测RDSS授时数据的试验验证表明,平稳过渡波束较北斗二号授时结果改善不明显;北斗二号双向授时结果较单向授时结果改善了电离层延迟,授时结果提高了约30%;北斗三号双向授时结果较北斗二号双向授时结果改善了轨道误差和卫星钟差等,授时结果则改善了60%。充分说明了轨道误差和卫星钟差是影响北斗RDSS...     

基于北斗三号和天通卫星通信的信道收发模块设计与实现

如今战争信息化迅猛发展,卫星通信极大地解决了通信距离短的问题,而且多数情况下只需要手持便携终端即可通信。我国天通通信卫星和北斗三号卫星均在不久前已经组网,覆盖了我国甚至全球,可满足语音、短报文等通信需求。但是目前的终端只实现了天通或者北斗等单一的模式,或者需要两种主机来实现车载和车下两种应用场景。因此,文章设计了一种基于北斗三号和天通卫星通信的信道收发模块,解决了只能实现单一模式卫星通信的问题,可以实现北斗三号、北斗二号和天通多模式通信,同时也解决了车上放置和车下便携等多场景应用模式。     

北斗预警信息压缩传输系统的设计与实现

北斗卫星单次短报文通信数据量及服务频率限制了长预警信息数据的传输。针对该问题,通过研究预警信息数据协议,设计预警信息压缩传输系统。为了提高预警信息传输效率,设计一种基于固定位长和RLE算法的混合压缩编码;为了提高预警信息传输成功率,设计基于预警信息压缩包的传输协议。此外,利用图形界面语言Qt完成人机交互界面并实现了预警信息压缩包的解码。最后,设计基于误报避免机制的预警信息显示,并给出算法的流程。实验结果表明,所设计的预警信息压缩传输系统能够有效地提高长预警信息数据传输效率和传输成功率,而且可在相关基于北斗卫星的预警信息发布系统中作为参考。     

基于北斗卫星的潜标数据回收技术研究

基于我国自主研发的北斗卫星,设计了一套潜标数据回收系统,采用卫星通信方式对潜标数据进行实时传输,卫星通信方式选用北斗一代卫星进行数据传输。由主控芯片STM32L控制系统工作状态,通信定位芯片RD0538对位置信息进行采集并解析,最后将待传回数据和定位数据通过北斗一代卫星进行报文传输。测试结果表明,该系统定位精度误差符合海上使用要求。该系统结构简单、占用体积小,用户可以设置系统发送频率。对该系统进行降低功耗的改进后,可将其工作时间延长至9天。     

基于气象观测无线传感网多协议网关系统设计

为了扩大气象观测无线传感网覆盖范围,实现气象数据跨地域研究共享,设计Tiny OS、北斗卫星和Wi-Fi多种通信方式的融合网关。网关系统面向气象观测无线传感网,将气象观测无线传感网采集的传感器数据与北斗卫星的定位授时数据通过Wi-Fi传输到近距离观测终端,同时在北斗卫星通信中心站使用北斗卫星共享数据。测试结果表明,该多协议网关系统可以稳定传输气象无线传感网观测数据和北斗卫星数据,扩大气象观测无线传感网的覆盖面积,方便全国气象数据的交流和共享。     

基于北斗短报文的野外光谱观测设备通信系统设计

为解决偏远地区野外光谱设备通讯盲区问题,设计了一种基于北斗卫星通信的远程数据传输系统。通过仪器通信电路板、北斗终端和室内数据中心软件的配合,实现设备远程通信功能。在该系统的配合下观测设备无人值守工作,避免人工频繁跑场,去除人为测量误差。针对北斗通信丢包,设计了数据重传功能,解决数据丢失问题。目前,该设计已应用于自动化场地观测辐射计,并在敦煌辐射校正场实地工作,满足数据通信要求。同时,该系统也可应用于其他需要远程无线通信的仪器设备。     

基于北斗系统的装甲车辆信息监控系统研究

通过对北斗卫星导航系统的功能、通信性能的分析,介绍了基于北斗系统的装甲车辆信息监控系统。系统通过车载北斗系统、传感设备分别采集车辆位置信息和状态信息,将各种数据信息进行封装,并利用北斗系统作为通信链路,发送相关信息至控制中心,实现车辆信息监控。     

SBS TDMA-DA system with VAC and DAC

This paper describes many of the design considerations involved in developlng the demand assignment (DA) subsystem of the TDMA satellite communication system for Satellite Business Systems. Each earth station has a satellite communications controller (SCC) which requests capacity to meet current voice and data traffic demands. A central reference station frequently reallocates capacity based on the requests of all the earth stations in a network. To minimize the amount of satellite capacity required, the SCC has a circuit-switching capability for voice calls as well as for digital data calls. Furthermore, the SCC employs voice activity, compression (VAC) and data activity cornpression (DAC), In which the amount of capacity requested is based on measured average speech activity as well as the number of off-hook voice ports and the number of off-hook data ports. Data calls are queued on a first-come, first-served basis when capacity is not immediateiy available. The reference station distributes excess capacity according to a nonlinear table lookup procedure so that the voice call blocking probability is equalized across the network. The DA system makes much more efficient use of satellite transmission capacity than a design with fixed-capacity trunk routes.     

Integration of Voice and Data in the Wideband Packet Satellite Network

The Wideband (packet satellite) network is an experimental 3 Mbit/s communications system developed under sponsorship of the Defense Advanced Research Projects Agency and the Defense Communications Agency. This system is being used to evaluate the use of packet transmission for efficient voice communication, voice conferencing, and integration of voice and data over a satellite channel. Each station in the Wideband network consists of an earth terminal (dedicated 5 m antenna plus associated IF/RF equipment), a burst-modem and codec unit, and a station controller. Station controllers provide interfaces to host computers (including packet speech sources) and manage the allocation of the satellite channel on a TDMA demand-assigned basis. TDMA demand-assignment is implemented using a reservation-based packet-oriented protocol capableof handling traffic at multiple priority levels. The channel protocol provides a reservation-per-message mode of service (datagrams) to support transmission from bursty traffic sources and a reservation-per-call mode of service (streams) to support traffic with more regular arrival statisticS (e.g., vioce). A distributed scheduler running in every station controller eliminates the need for a central control station and minimizes network transit delay for datagram transmission as well as stream creation, modification, and deletion. In this paper we describe the protocols and mechanisms upon which the Wideband packet satellite network is based.     

C-PRMA: a centralized packet reservation multiple access for localwireless communications

Packet-switched technology has been demonstrated as effective in cellular radio systems with short propagation delay, not only for data, but also for voice transmission. In fact, packet voice can efficiently exploit speech on-off activity to improve bandwidth utilization over time division multiple access (TDMA). Such an approach has been first suggested in the packet reservation multiple-access (PRMA) technique, an adaptation of the reservation ALOHA protocol to the cellular environment. However, being PRMA-based on a fixed frame scheme, it cannot thoroughly take advantage of the very short propagation delays encountered in microcellular systems that allow, for instance, the immediate retransmission of packets lost because of the interference noise from adjacent cells. We present the centralized PRMA, a natural enhancement of PRMA, in which the base station (BS) plays a central role in scheduling the transmissions of mobile stations (MSs). As a consequence, the transmission scheduling is very flexible and can account for the different traffic rate and delay constraints that emerge from voice and data integration. A packet retransmission policy to recover corrupted packets can be implemented and operated efficiently to provide an acceptable grade of service, even in a very noisy environment. The simulation results presented show the quantitative improvements of the centralized packet reservation multiple-access (C-PRMA) performance with respect to PRMA     

一种北斗三号RDSS性能实时监测的实现方法

随着北斗三号系统应用的逐步推广,北斗RDSS功能在边防、气象、交通、航空和应急搜救等行业中应用越来越广泛,因此北斗RDSS性能监测是推动北斗RDSS服务应用的重要途径。设计了一种北斗三号RDSS性能实时监测的系统实现方案,系统具备安全性、高可靠性和易扩展性,满足数据采集、接收、存储、处理和管理监控等各个功能的基础支撑需求;针对RDSS的性能评价内容进行了设计,包含通信内容查询、接收信号类型、波束数量和波束功率、通信成功率、定位精度及通信时延等功能指标。最后,通过在对天环境条件下的实际测试验证,分析了测试结果数据,验证了方案的可行性。提出的方案具备RDSS性能监测实时性强、连续监测、及时预警和远程推送的特点,可以通过网络向相关用户推送相关信息,使用户能够方便快捷地掌握RDSS使用性能,为用户RDSS应用提供保障。     

分组卫星话音／数据综合的混合多址协议性能研究

本文讨论了一种用于分组话音／数据综合的混合多址协议，该协议是固定分配与随机访问的混合，并且赋予话音分组优先传输权，从而保证了无重传话音分组有较小的丢失概率。本文进行了详细的理论分析，并得出了性能比较特性，所得结果认为这是一个兼顾话音／数据综合的较好协议，且具有一定的灵活性。     

Proposal and performance evaluation of an efficient multiple-access protocol for LEO satellite packet networks

This paper deals with a modified version of the packet reservation multiple-access (PRMA) protocol suitable for integration of real-time (voice) and best effort (data) traffic in low Earth orbit (LEO) satellite communication systems. The proposed scheme differs from previous alternatives on the method adopted to handle access requests for voice and data terminals, and to transmit data messages. An analytical approach is proposed and validated in the case of voice and classical (i.e., geometric distributed) data traffic in order to derive system performance in terms of mean data message delay and voice packet dropping probability. However, in order to better highlight the advantages of the proposed approach typical interactive and background traffics types have been also considered. Performance comparisons with previous proposed PRMA protocols for voice and data transmission in LEO satellite communication systems are also shown in order to highlight the better behavior of the proposed scheme. Finally, a brief discussion concerning the extension of the proposed S-PRMA protocol to the case of different satellite communication systems is also provided.