4G空中接口的特征及其在多址及双工方式上的挑战…

本文从第四代移动通信(4G)空中接口的初步需求出发,介绍了第四代移动通信空中接口的特点,重点介绍了第四移动通信系统空中接口在多址及双工方式上的挑战。     

4G空中接口的特征及其在多址及双工方式上的挑战…

本文从第四代移动通信(4G)空中接口的初步需求出发，介绍了第四代移动通信空中接口的特点，重点介绍了第四移动通信系统空中接口在多址及双工方式上的挑战。     

LTE空中接口在卫星通信中的适用性

目前LTE体制已成熟,在卫星通信系统中应用LTE技术有利于星地一体化网络的发展.移动卫星系统在4G网络中成功应用的一个关键因素是设备和地面系统得到最大的通用性.一种有效的解决这个问题的方法是利用地面空中接口作为卫星空中接口的基础.由于3GPP(The 3rd Generation Partnership Project...     

全球卫星移动个人通信与铱系统

自从１９９０年美国摩托罗位公司提出低轨道全球卫星移动通信系统－铱系统以来，其前所未有的星上处理，星上交换和星际链路等高新技术以及系统本身不依赖地面通信网的固有特点，出现了多种不同用途和特点的卫星通信系统。本文着重对全球卫星移动通信系统，铱系统的概况，关键技术参数，业务类型和我国市场前景以及北京关口站试验工程的进展情况等作了简要的介绍。     

天地一体化网络空口波形仿真

卫星通信作为地面通信网络的重要补充,在应急通信、海事通信等方面具有不可替代的作用。近年来随着全球互联网的迅猛发展,卫星通信总体上朝着大容量、高速率、宽带化的方向发展,并逐渐出现了与地面网络融合的趋势。为发展天地一体化网络、真正实现全球无缝覆盖,需要在空口波形上进行一体化设计。针对天地一体化空中接口波形设计方案,在分析了现有的5G候选波形的基础上,提出可以将GFDM作为天地一体化网络的波形,分析了GFDM的功率谱密度、误码率、频谱效率以及PAPR性能。     

美军MUOS系统及关键技术分析

移动用户目标系统(MUOS)作为未来美军军事通信转型的重要组成部分,能够满足美军全球范围高性能战术卫星通信能力的需求.在深入描述了MUOS系统构架、信息流的基础上,分析比较了MUOS与地面蜂窝WCDMA移动通信系统,从信道传输特性、环路传输时延以及信道衰落形式等方面指出了两者之间的差别.从空中接口、RAKE接收、抗干扰、功率控制和无线电资源管理等方面着重分析了MUOS系统的关键技术,对比地面蜂窝WCDMA移动通信,指出了MUOS在相应技术上做的改进和区别.最后从空间段、地面段和用户段三个层面归纳了MUOS系统目前发展现状,总结其未来研究趋势,并指出我国卫星移动通信发展应借鉴的地方.     

面向手机直连的低轨卫星通信：关键技术、发展现状与未来展望全文替换

为满足全时、全域通信需求,低轨卫星通信将成为6G的重要组成部分。通过对地面移动通信协议体制进行适应性改进,低轨卫星可为地面移动手机终端提供直连服务。介绍了面向手机直连的低轨卫星通信关键技术和商业项目发展现状,探讨了未来需解决的关键问题和潜在技术途径。     

移动卫星通信中的码——时分多址（CTDMA）技术

考虑到中，低轨道星座移动通信系统与地面移动多的多模式互联性要求，本文提出的码－时分多址及其射频接口体系概念，就是为实现移动卫星通信系统与地面移动通信网络合多模式工作和满足动态通信环境的需要，并具体阐述了有关ＣＴＤＭＡ移动降临通信系统在技术方面的优越性。     

6G网络中的星地一体化

基于全球移动通信系统“使用一代、建设一代、研发一代”的发展思路,6G的研究已启航3年。本文针对6G网络中融合地面网络（TN）和非地面网络（NTN）展开研究,分析了6G移动通信网络愿景与卫星通信特点,探讨了星地一体化的融合网络架构研究方向,简要介绍了星地一体化的潜在技术。     

后三代移动通信系统的发展驱动与服务应用

众所周知，3G移动通信系统可以提供相对2G有所改善的Internet多媒体业务．如WCDMA系统的空中接口可以提供户外中速率(384kbit／s)和室内环境下的高速率(2Mbit/s)的信号传输，而且它还采用空中接口的统计复用技术，提高了分组模式传输的效率。但是，第二三代移动通信系统仍然有着很多不足和缺陷。由于     

Optimized handover and resource management: an 802.21‐based scheme to optimize handover and resource management in hybrid satellite‐terrestrial networks

Satellite communications can provide fourth generation (4G) networks with large‐scale coverage. However, their integration to 4G is challenging because satellite networks have not been designed with handover in mind. The setup of satellite links takes time, and so, handovers must be anticipated long before. This paper proposes a generic scheme based on the Institute of Electrical and Electronics Engineers 802.21 standard to optimize handover and resource management in hybrid satellite‐terrestrial networks. Our solution, namely optimized handover and resource management (OHRM), uses the terrestrial interface to prepare handover, which greatly speeds up the establishment of the satellite link. We propose two mechanisms to minimize the waste of bandwidth due to wrong handover predictions. First, we leverage the support of 802.21 in the terrestrial access network to shorten the path of the signaling messages towards the satellite resource manager. Second, we cancel the restoration of the satellite resources when the terrestrial link rolls back. We use OHRM to interconnect a digital video broadcasting and a wireless 4G terrestrial network. However for the simulation tool, we use a WiMAX as the terrestrial technology to illustrate the schemes. The simulation results show that OHRM minimizes the handover delay and the signaling overhead in the terrestrial and satellite networks. Copyright © 2013 John Wiley & Sons, Ltd.     

Satellite UMTS/IMT2000 W-CDMA air interfaces

The third-generation IMT-2000 initiative of the International Telecommunication Union is aiming at the provision of a limited family of global standards providing worldwide multimedia wireless services in a host of environments encompassing indoor picocells to satellite megacells. The ITU IMT-2000 initiative has been supported by several regional standardization bodies such as the European Telecommunication Standard Institute with its Universal Mobile Telecommunication System. In this article a few air interface proposals for the satellite component of UMTS/IMT-2000 based on adaptation of the emerging terrestrial wideband CDMA standards are reviewed. In particular, S-UMTS requirements are examined together with W-CDMA applicability to the satellite environment. It is shown that with minor adaptations, the terrestrial W-CDMA air interface provides an efficient solution for the satellite UMTS component. This commonality will certainly help in the realization of low-cost low-size dual-mode user terminals encompassing both terrestrial and satellite components     

Filter bank‐based multiple access in next‐generation satellite uplinks: A DVB‐RCS2‐based experimental study

In the context of the on‐going evolution of satellite communications (SatCom) systems to their next generation, and in the direction of their integration with fifth generation (5G) terrestrial networks, it is of interest to study in depth the applicability in realistic SatCom of waveforms that have shown promise to meet the 5G requirements. This paper presents a comparative study, based on total degradation (TD) over a range of output back‐off (OBO) values, on out‐of‐band emission and spectral efficiency, of frequency division multiple access (FDMA) schemes employing offset quadrature amplitude modulation‐based filter bank multi‐carrier (FBMC /OQAM), classical orthogonal FDMA (OFDMA), and their single‐carrier counterparts to illustrate the potential gains from the integration of the FBMC waveforms in the satellite context and standards. The air interface simulated follows the digital video broadcasting (DVB) family of standards for the satellite uplink, considering both time and frequency synchronization impairments and two typical input constellations. Our results confirm the superiority of the single‐carrier (SC) schemes in such a nonlinear environment. The SC‐FBMC waveform is shown to be the most practical candidate since it is shown to attain a TD performance similar to that of SC‐OFDM at absolutely no cost in spectral efficiency.     

LTE RLC UM模式在卫星通信中的适应性研究

卫星环境和地面环境差异显著,存在链路时延大、信道衰落较平坦和波束覆盖范围广等特点,因此卫星移动通信4G化不能照搬地面LTE标准。针对GEO卫星通信特点,分析了LTE RLC UM模式在大时延卫星链路中的适应性,重点对RLC UM参数sn-Field Length和t-Reordering的功能和取值进行了论述,给出了对驻留时间T的建模。采用C语音实现了RLC协议仿真,并用仿真结果验证了RLC UM模式的各项参数和业务速率对驻留时间T的影响,可为LTE over Satellite设计提供参考。     

US Air Force communications in Desert Storm

The US Central Command Air Forces' (USCENTAF) communications network for Operations Desert Shield and Desert Storm is described. The Central Command Air Forces network utilized 27 SatCom terminals, 27 automatic switches, and 27 terrestrial links and had the responsibility of providing air traffic services across six countries at 24 locations handling 350000 flight operations. The system complexity and air traffic operations, satellite transmission system, terrestrial transmission system, and voice switched network are discussed     

Next generation satellite systems for aeronautical communications

U.S. airspace is reaching its capacity with the current air traffic control (ATC) system. The number of flights is constantly rising and it is estimated to be over 58 million per year by 2005. The FAA has undertaken several projects to modernize the National Airspace System (NAS) to ensure the safety of the increasing number of flights. Of special importance is the modernization of the air–ground communications infrastructure, which is the heart of the ATC. The current plan in the modernization of the air–ground communications is to migrate from analog voice only system to integrated digital voice and data system. The next generation satellite systems can be an alternative to the terrestrial air–ground systems by their low propagation and transmission delays, global coverage, high capacity and free flight suitable characteristics. In this paper, we give an overview of the current and the future ATC architectures, describe the systems and the communications issues in these systems and develop a framework in which next generation satellite systems can be integrated to the future ATC systems. Copyright © 2004 John Wiley & Sons, Ltd.     

Next-generation mobile satellite networks

Due to the increasing demands of multimedia services supporting high bit rates and mobility, ATM, TCP/IP, and satellite technology are going to be associated to form the internetwork infrastructure of future global systems. In this scenario, distinctions between terrestrial and satellite communications systems, as well as between fixed networks and 3G mobile networks, will cease to exist in a global coverage wireless system. The European Action COST252 actively participated in developing the satellite component of UMTS     

S-WiMAX: adaptation of IEEE 802.16e for mobile satellite services - [WiMAX update]

Mobile satellite services are attracting renewed attention stemming from the FCC ancillary terrestrial component ruling that allows satellite spectrum to be used for integrated terrestrial services in the footprint of the satellite. This attention is focused on the development of dual-mode satellite-terrestrial devices to facilitate hybrid satellite-terrestrial networks intended by the ATC order. The satellite component in these dual-mode devices is best adapted from the air interface chosen for the ATC to optimize form factor, especially for small hand-held devices, mobility management, power efficiency, and a common core network functionality. With the advent of WiMAX as a viable 4G technology, satellite adaptation of WiMAX has been considered for the satellite services coupled with WiMAX ATC. The main considerations for satellite adaptation of WiMAX, relative to its terrestrial counterpart, are reduced link margin and longer transmission delays ? both absolute delay from the center of a spot beam to the satellite and differential delay between the beam edge and the beam center to the satellite. These considerations suggest adaptation of the subchannelization schemes, the frame synchronization methods, and the ranging process in WiMAX to make it operable over satellite, while keeping the general framework of the WiMAX protocol stack intact, thereby facilitating the incorporation of S-WiMAX into a common baseband processor with terrestrial WiMAX; this allows S-WiMAX to be added to terrestrial WiMAX devices with minimal cost and formfactor impact. Methods for these adaptations are considered here.     

Air interface identification for Software Radio systems

Reconfigurable Software Radio (SR) equipment is considered as the next evolutionary step in the mobile communications. One of the most crucial properties of a SR terminal is that it is capable of using a wide range of air interface standards, providing a seamless interoperability between different standards and an enhanced roaming capability, paving way to a more flexible and efficient use of spectral resources. This multimode operation has to be supported by a number of key functionalities, one of which is the air interface identification. A SR terminal, when switched on, has to be able to locate and identify the air interfaces available in the frequency environment, and while connected to a network, it has to monitor the presence of alternative air interfaces to perform interstandard handover if necessary. In our work, we propose exploiting the distinct cyclostationary properties of signals from different air interfaces as features for air interface identification.