开发和利用C频段资源的新途径

本文简要介绍可在赤道平面以外的空间充分利用C频段频谱资源的两种技术手段——倾斜轨道同步卫星和高空通信平台,并就相关系统的潜在通信容量以及新系统与现存系统的干扰协调等问题作了初步探讨。     

2000年广播电视技术发展展望 四、电视卫星广播

利用卫星传输远距离的电视节目,是六十年代以来通信事业上的重大突破。其传输方式可分为转播方式和直播方式两种。转播方式通常是广播与通信业务共用频段。如加拿大ANIK卫星,美国的PBS广播卫星,印度尼西亚、巴西和中国的国内卫星都是采用通信频段(4/6GHz),地面接收电视的天线口径3～6米。除C频段外,国际上已采用Ku频段中功率通信卫星转播电视节目,地面可采用2米     

高空平台站(HAPS)获得新增频谱资源划分

HAPS是指位于距离地面18到50公里的空中通信平台站。它相对于地球准静止,具有通信范围大、时延低等特点,能够为偏远地区和恶劣地形条件下的地区建设关口站或开展大容量通信服务提供便捷、经济的解决方案。特别是在地震、洪水等严重自然灾害导致常规通信系统瘫痪时,HAPS还能够快速地提供有效应急通信服务。2019年世界无线电通信大会(WRC-19)通过审议1.14议题"促进人们获取通过高空平台台站提供的宽带应用"并作出决议,在全球范围内,在固定业务划分下新增38GHz^39.5GHz频段,扩展31GHz^31.3GHz频段标识用于高空平台站(HAPS)固定通信(双向使用),在满足H A P S应用需求的同时,对H A P S下行方向使用提出了具体限制以保护现有的固定、移动和卫星固定业务台站不受影响。     

平流层通信及相关技术

蜂窝和个人移动通信系统（ＰＣＳ）需要大量广布的天线塔、基站、有线或微波线路，卫星通信系统地面设施相对较少，但ＧＥＯ系统的用户终端笨重且昂贵，信号时延大；ＭＥＯ和ＬＥＯ卫星相对于地面的快速运动使系统的构成和控制复杂化，并且卫星发射和维护费用高，高空航空平台（ＨＡＡＰ）无线通信系统（即平流层通信）实为折衷方案，本文讨论了此类通信系统的特点和实现的可能性。     

一种无人机载超视距通信系统

针对中、高空长航时无人机超视距通信系统普遍采用Ku频段卫星中继存在信号可用带宽有限、干扰源众多、机载端设备较大的现状,提出了一种基于Ka频段卫星的无人机超视距通信系统总体与分系统工程实现方案,并给出了关键设计要素。在详细推导链路计算公式基础上,以前向速率为51.2 kb/s、返向速率为8 Mb/s为例进行了链路余量预算与数值仿真分析,并与传统Ku频段方案在传输速率、抗干扰能力、天线口径等方面进行了分析比较。结果表明,在同等条件下所设计的系统性能可提高20%左右。飞行试验结果验证了该方案的合理性、可行性、有效性和工程可实现性,为无人机超视距通信系统总体设计和工程实现提供了思路与参考。     

新一代动中通Ka频段卫星通信在新华社的应用前景剖析

一.Ka频段技术背景综述相比于普通的地面通信,卫星通信具有覆盖范围广等多种优点。尤其在应急、国土监测、远洋通信等普通地面通信系统无法使用的情况下,卫星通信将发挥极其重要的作用。而在卫星通信系统中,Ka频段相较于传统的Ku频段,具有明显的优势。相比于传统的Ku频段通信卫星,Ka频段卫星能够支持的通信节点数量远远大于Ku频段。而且,Ka频段通信卫星具有4倍于Ku频段卫星的     

卫星移动业务C频段的干扰研究

分析了卫星移动业务与地面固定业务共用C频段时,对该频段地面固定业务的干扰情况。以世界无线电通信大会议题提出的卫星移动业务候选频段为背景,从理论上分析了卫星移动系统上行链路与下行链路对固定业务的干扰情况。利用国际电联相关建议搭建了干扰分析模型,并进行了仿真分析。通过分析,在假设的场景下,卫星移动业务的上行链路会对地面固定业务产生干扰,而上行链路不会产生干扰。     

平流层飞艇通信系统关键技术探讨

平流层飞艇通信系统同时具有微波中继和卫星通信的优点,可与地面控制单元、空中中继单元以及多种无线用户构成通信网络,已成为国内外的研究热点。国际电信联盟（ITU）已分配给高空通信系统47.2～47.5GHz和47.9～48.2GHz的工作频段。然而到目前为止,世界上还没有一款真正可以投入使用的平流层飞艇通信系统,飞艇平台和通信载荷方面均存在多个关键技术迫切需要解决。     

高空平台信息系统--新一代无线通信体系(下)

高空平台站(HAPS)是近年来正处于先期研究、但尚未成功演示的新型信息系统。它利用平流层稳定的气象条件和良好的电波传输特性,通过平台实现地面用户之间、平台之间或平台与卫星之间的通信连接,具有布局灵活、应用广泛、成本低廉、安全可靠等优点。积极开展高空平台与有关信息系统的研究,有助于我国在通信事业上与国际先进技术保持同步,为通信事业开拓一个新的领域。     

高空平台信息系统--新一代无线通信体系(上)

高空平台站(HAPS)是近年来正处于先期研究、但尚未成功演示的新型信息系统。它利用平流层稳定的气象条件和良好的电波传输特性,通过平台实现地面用户之间、平台之间或平台与卫星之间的通信连接,具有布局灵活、应用广泛、成本低廉、安全可靠等优点。积极开展高空平台与有关信息系统的研究,有助于我国在通信事业上与国际先进技术保持同步,为通信事业开拓一个新的领域。     

High Altitude Platform Station (HAPS): A Review of New Infrastructure Development for Future Wireless Communications

This paper looks into the relatively new field of high altitude platform stations. HAPS is seen as a ‘middle ground’ between the terrestrial and satellite cases, and aims to exploit of the advantages of both types of system. Since HAPS is such a new field, this paper focuses on the technology behind a HAPS communications system, how this has developed, and compares it to the terrestrial and satellite equivalents. One important area that is being investigated is the applications for which HAPS should be used. This is a critical issue if a significant business case is to be made for HAPS. Worldwide HAPS projects and research issues are also highlighted. Finally, the review concludes with the remarks on the future of HAPS for wireless communications systems.     

HAPS通信覆盖及链路特性分析

由高空平台(HAP)构成的信息系统将是新一代的无线通信系统,它融合了陆地和卫星通信系统的优势,又不同程度地避免了两者的缺点,在通信领域的应用得到了广泛认同,是现有通信方式的有效补充。通过重点研究高空平台站(HAPS)通信的覆盖特性、多波束小区划分方案、链路特性及功率控制等关键问题,提出了一种适应HAPS通信多波束小区划分方案,并且通过计算与仿真分析比较,说明提出方案更适应HAPS通信场景,为HAPS通信的工程实现提供了参考。     

Analytical investigation on sharing band overlaid high altitude platform station-terrestrial CDMA system

Uplink inter-system interference factor for sharing band overlaid high altitude platform stations (HAPS) and terrestrial CDMA system has been investigated. A simple model is proposed and key parameters affecting the interference factor are identified. The results suggest that appropriate design of the system could provide reasonable sharing capacity.     

Capacity of the WCDMA System Using High Altitude Platform Stations

In this paper, we provide a method to estimate the capacity of the wideband code division multiple access (WCDMA) scheme using High Altitude Platform Stations (HAPS), and demonstrate the results. This is to validate that the HAPS system is one of the most effective solutions to provide high quality wireless communication services, such as IMT-2000 services. We use a practical system model which describes the HAPS system most appropriately, and this leads to realistic estimation results. We estimate the reverse and forward link capacity of the HAPS WCDMA system and compare it to that of the terrestrial system. The estimation results show that the capacity of the HAPS WCDMA system is about 1.2–1.67 times larger than that of the terrestrial system.     

Spectrum Correlated Criteria and Their Impacts on High Altitude Platform Station (HAPS) and Fixed Satellite Service (FSS) Coexistence in Frequency Range 5,850–7,075 MHz

High altitude platform station (HAPS) is an innovative technology which delivers some unique features, contrary to conventional communications networks, such as fixed satellite service (FSS). The absence of confirmed spectrum emission mask (SEM) of HAPS and its diversity to work within FSS networks are significant issues in evaluating the coexistence of HAPS and FSS. At this juncture, a practical SEM for HAPS gateway links is proposed which will endeavor to assess its functionality and its ability to coexist with FSS. HAPS SEM’s impact on coexistence issues are exposed upon consideration of criteria such as MD, NFD and ACIR. These facets are well-described and their measured amounts for specific applicable SEMs are proposed. Therefore, reckoning process regarding these factors is ascertained. It must be said that the remarked criteria and their amounts for HAPS gateway links are unprecedented. The simulation parameters are well organized based upon International Telecommunication Union and World Radiocommunications Conferences periodicals. The aim of this article is to shed more light on the associated facets of the HAPS network spectrum and their impressions on HAPS and FSS networks coexistence. The assessments have been performed for HAPS gateway links in the 5,850–7,075 MHz frequency band where FSS uplink frequency band in C-band (5,925–6,725 MHz) partially intrude with HAPS gateway links. Therefore, HAPS gateway links channelization regarding FSS uplink channel is appraised and light is shed on the impact of HAPS and FSS coexisting in the same frequency band.     

Experiments on IMT-2000 Using Unmanned Solar Powered Aircraft at an Altitude of 20 km

Several countries are keenly interested in the research and development of novel wireless communication systems using high altitude platform stations (HAPS) because of their great potential benefits. In June and July 2002, we carried out the world's first experiment on International Mobile Telecommunication 2000 (IMT-2000) by radio relay via transponders onboard an unmanned solar powered aircraft at an altitude of 20 km. This experiment demonstrated for the first time the feasibility of applying the IMT-2000 system using a HAPS and a compact cellular phone designed for terrestrial cellular systems. Two experiments were carried out over Kauai Island in Hawaii, USA. In the first experiment, we were unable to establish an IMT-2000 link connection via the aircraft at 20 km because the onboard transponder for the reverse link received unexpected signals from a terrestrial cellular system in commercial use 200 km away on Oahu Island. However, we managed to establish the link by connecting a high gain external antenna to the cellular phone. After the first flight experiment, we developed an onboard receiving antenna with a low sidelobe level to suppress interference signals. In the second experiment, we successfully achieved IMT-2000 video communication with a cellular phone. This paper presents the experimental results and analysis of these IMT-2000 communication experiments.     

A New Approach of Channel Modeling in HAPS Based Networks and Their System Performance Analysis

This paper concerns channel modeling for High Altitude Platform Systems (HAPS) and the performance evaluation of Hybrid_ARQ in the WiMAX network provided by HAPS. The stratospheric platform or HAPS is currently a new proposal for WiMAX technology. Firstly we study the HAPS channel behavior as a Finite State Markov Channel (FSMC). In this way, the range of magnitude of the fading channel gain is partitioned into a finite number of states; then based on level crossing rates, the state transition probabilities are derived. The validity of the proposed model is evaluated by theoretical and link level simulation results. Next, we use the derived state transition probabilities as channel model parameters in OPNET simulator for HAPS-WiMAX to calculate HARQ system level measures. The paper compares the performance obtained using two different models in fading effects, i.e. AWGN and our HAPS channel model. In addition, the influence of parameters is analyzed through comparison between our model and the Stanford University Interim (SUI) channel models, in terms of the Bit Error Rate (BER).     

HAPS系统与卫星通信系统综合组网研究

HAPS系统拥有巨大的通信价值,现已成为空间通信的研究热点.本文将先对HAPS系统的特点和通信优势做具体的介绍,在此基础上展开HAPS系统与卫星通信系统组网优势以及应用的分析.最后详细讨论了HAPS系统与卫星通信系统组网将面临的关键技术和问题.     

Designing the interworking of terrestrial and satellite IP-basednetworks

The design of effective interworking between a multimedia terrestrial backbone and a satellite access platform is a key issue for the development of a large-scale IP system designed for transporting multimedia applications with QoS guarantees. This article focuses on the design of a gateway station that acts as an interworking unit between the two segments of the systems. The guarantee of differentiated QoS for applications within the envisaged global IT system is achieved effectively by assuming that the IP IntServ model in the satellite access system is combined with a DiffServ fixed core network, in which the RSVP aggregation protocol is implemented. Thus, the design activity of the IWU mainly focuses on the following issues: seamless roaming between the two heterogeneous wireless and wired environments, efficient integration between the two IP service models (IntServ and DiffServ), and suitable mapping of terrestrial onto satellite bearer for traffic with different profiles and QoS requirements     

Spectrum allocation method for cognitive satellite network based on service priorities

By using spectrum allocation technology of cognitive radio into integrated satellite and terrestrial networks,the satellite communication network can share spectrum with the terrestrial network and improve utilization efficiency of frequency spectrum in the satellite communication system.Firstly,a spectrum resource sharing model in integrated satellite and terrestrial networks was introduced,and the scenery that cognitive satellite downlinks use the vacant spectrum of terrestrial network was analyzed.Then,the interference and signal model was analyzed.Finally,considering different priority types of satellite terrestrial terminals,a spectrum allocation scheme based on priority was proposed,which could ensure the total throughput in satellite downlink communication and increase the throughput of high-priority terrestrial terminals.