GEO与NGEO卫星频谱共存干扰抑制技术（一）

由于对低延时实时系统和宽带数据的需求日益增加,人们越来越关注如何在几个可用的频带中部署更多的近地轨道（LEO）和中地轨道（MEO）卫星。当可用的非静止轨道（NGEO,即LEO/MEO）卫星数目增多时,其与在轨的地球静止轨道（GEO）卫星频谱共存已经成为了一种必须。在这种情况下,为了使它们的频谱可以共用,探索一项技术来抑制GEO和NGEO系统间的干扰是非常关键的。更具体地说,在GEO和NGEO卫星网络共存的情况下,共线干扰可能是一个严重的问题,特别是在赤道上空。本文提供了几个关于如何在NGEO卫星链路和GEO卫星链路共存情况下频率共用的研究。除此之外,本文提出了几种认知方法来解决共线干扰,也提出了未来研究方向。     

In‐line interference mitigation techniques for spectral coexistence of GEO and NGEO satellites

The interest towards the deployment of Low Earth Orbit (LEO)/Medium Earth Orbit (MEO) satellite systems in several frequency bands is increasing due to the requirement of low latency for real‐time systems and high demand of broadband data. When the number of usable Non‐Geostationary (NGEO) satellites, that is, LEO/MEO in space, increases, the frequency coexistence between the NGEO satellite systems with the already existing geostationary (GEO) satellite networks becomes a requisite. In this context, it is crucial to explore interference mitigation techniques between GEO and NGEO systems in order to allow their spectral coexistence. More specifically, in the coexistence scenario of GEO and NGEO satellite networks, in‐line interference may be a serious problem, especially in the equatorial region. In this paper, we provide several frequency sharing studies in the context of the coexistence of an NGEO satellite link with another NGEO/GEO satellite link. Furthermore, we carry out interference analysis between GEO and MEO satellite systems considering the case of the O3b satellite system and propose an adaptive power control technique for both the uplink and downlink scenarios in order to mitigate the in‐line interference. Moreover, we suggest several cognitive solutions for mitigating the in‐line interference and provide future research issues. Copyright © 2014 John Wiley & Sons, Ltd.     

5G基站与邻频系统之间的干扰问题研究

针对5G基站与卫星地球站等邻频系统在频率共用、地理共存情况下出现的干扰问题,对5G基站被干扰情形进行了理论计算,对其他台站被干扰情形以及合法台站之间的共存进行了分析研究,提出了在出现同频干扰时能提升干扰定位效率的方法,包括使用实时频谱功能分析同频信号,运用5G NR解调功能对信号进行识别,以及结合车载同频多辐射源定位方法来确定干扰源的大致位置。     

25.25～27.5 GHz频段卫星间业务与IMT系统兼容性研究

基于现有技术参数,研究了25.25～27.5 GHz频段国际移动通信（IMT）系统与卫星间业务数据中继卫星（DRS）系统间的干扰共存情况。采用集总干扰评估方法,比较了数据中继卫星经度分别在59°、85°、113°时,IMT基站对其造成干扰的情况。此外,还通过固定干扰余量,推导了IMT基站总数及其与IMT发射功率之间的关系。研究结果可为未来25.25～27.5 GHz频段IMT系统设计与部署、5G频率规划提供借鉴。     

Bandwidth Overlap Factor for Feasible Coexistence of LTE-A and Point to Multipoint LMDS Systems

The necessity to share the radio spectrum becomes highly significant in the recent time due to emerging new wireless technologies and, the cost and difficulty in attaining new frequency spectrum licenses. However, spectrum sharing leads to substantial interference between the close systems especially in the same frequency band. In this paper, we present a spectrum sharing scheme to investigate coexistence feasibility results in interference from orthogonal frequency division multiplexing (OFDM)-based Long Term Evolution-Advanced (LTE-A) into point to multipoint (P-MP) local multipoint distribution service (LMDS). This method proposes a spectrum frequency mask for the OFDM-based LTE-A according to bandwidth overlapping method with the P-MP LMDS system. The relative power spectral density of the proposed spectrum emission mask due to bandwidth overlap has been mathematically derived in a more compact closed-form. It shows smoother and 1.7 dB less than that of traditional OFDM mask in the main spectrum bandwidth which in turn leads to reduce the interference effects to LMDS system. The coexistence coordination studies are made at the frequency of 3500 MHz, on the base of co-primary operation and co-located systems. The numerical results demonstrate that the difference in amount of the required carrier frequency for safe coexistence increases as LMDS sector size increases. In addition, OFDM system with small channel bandwidth is much more affected than the wider channel bandwidth in terms of the necessary minimum guard bandwidth for harmless coexistence when the LMDS cell size changes from 0.5 to 3 km².     

低轨卫星通信系统干扰分析及策略研究

卫星通信技术日益进步,低轨卫星通信系统已然成为新的发展趋势.由于频谱资源受限,低轨卫星通信系统可能面临自身及与外部地面和卫星系统的同频干扰问题.文章指出从外部系统对低轨卫星通信系统干扰、低轨卫星通信系统对外部系统干扰以及低轨卫星通信系统内部干扰3个方面进行了系统干扰场景分析,在此基础上,根据不同的干扰情况分别给出了外部...     

Broadband satellite system technologies for effective use of the12-30 GHz radio spectrum

Broadband satellite systems are an integral part of communications technology, aiming to provide a wide range of services to a society that increasingly expects ubiquitous access to broadband telecommunication services. Key drivers behind the development of these systems include rapid growth in the use of the Internet, PC- and TV-based e-commerce and interactive broadcasting services. In the UK, broadband satellite service trials are currently being conducted by BT, amongst others, with a primary objective of providing services to areas where asymmetric digital subscriber line (ADSL) technology has not been deployed. Two key factors for the success of broadband satellite technology lie in the area of overcoming constraints associated with frequency spectrum and orbital resources. This paper provides a review of technologies employed in geostationary (GSO) and nongeostationary (NGSO) satellite networks designed for the provision of broadband services to fixed and portable ground terminals within the 12 to 30 GHz frequency range. After reviewing the system design parameters related to the use of the radio frequency spectrum, consideration is given to the issues involved in sharing spectrum between GSO and NGSO satellite networks     

Satellite spacing and frequency sharing for communication and broadcast services

Satellite relays complicate the problem of sharing a limited frequency spectrum that is in great demand. This paper reviews the problem and outlines a general approach for efficient use of orbits and spectrum. The protection of received signals, the equipment capabilities, and systems considerations pertinent to the problem are reviewed before systematically examining the principal direct and scatter modes of interference. Conclusions derived include the following. The full potential use of orbits and spectrum for satellite systems can provide enormous capacities greatly exceeding any current proposals, but it requires careful coordination of many system parameters. The use of spectrum for microwave or satellite relays to fixed terminals could evolve to intense full sharing by both types of service without seriously limiting either one or requiring unreasonable accommodation. The satellite down links for area coverage to small terminals (e.g., mobile and broadcast services) can share fully and intensively the spectrum above VHF that is used for terrestrial mobile and broadcast services without seriously limiting the potential of any of the services. Although the greatest potential capacity of the spectrum lies above 16 GHz, for most down-link applications propagation factors make it more attractive to share the spectrum below about 16 GHz much more intensively before making extensive use of the higher frequencies. Providing the satellite down-link spectrum for area coverage to small terminals deserves priority consideration. For this purpose the UHF band is most attractive; the merit of the spectrum rapidly diminishes for higher frequencies.     

频率重用技术干扰问题研究

随着移动通信技术的飞速发展和移动数据业务量的爆发性增长,全球多个国家开始了LTE的商用进程。随着LTE的进一步发展,现有2G网络将有部分频率重用于LTE,这必将带来LTE与GSM系统间的共存干扰,为了保证LTE与GSM系统能够正常运行,制定完善的邻频共存保护方案是频率重用技术需要解决的关键问题之一。本文通过对GSM与LTE系统间的邻频干扰问题进行深入研究,提出了不同LTE制式与GSM共存时的保护间隔方式,为频率重用技术的发展奠定了坚实的基础。     

Coexistence of the broadcasting satellite service with fixed service systems in frequency bands above 10 GHz

The allocation of certain frequency bands to both the broadcasting satellite service and the fixed service on a primary basis raises the issue of coexistence, whenever the two types of services are located in the same area and no coordination/agreement is effected. Although regulatory institutions have issued general guidelines concerning future systems, the effect of frequency sharing by numerous operating satellite earth terminals should be examined. The present paper provides an analytical methodology for the prediction of the carrier-to-noise plus interference ratio (CNIR) of broadcasting satellite systems, suffering from interference from an adjacent terrestrial link at frequencies above 10 GHz. The proposed model takes into account the aggravation of intersystem interference due to the spatial inhomogeneity of precipitation. A simplified version of the analytical model, useful for back of the envelope computations is also presented. Some interesting case studies are finally examined.     

CDMA通信卫星系统容量分析

对基于码分多址(CDMA)体制的通信卫星系统及其容量进行了分析,从系统的角度,提出了CDMA体制的通信卫星系统容量的数学模型。定量分析了用户数量与系统的扩频增益、抗干扰能力指标、卫星转发器饱和功率等的关系,容量分析的结果可供人们在选择和设计通信卫星系统时参考。     

Criteria to Improve Time-Delay Estimation of Spread Spectrum Signals in Satellite Positioning

Positioning accuracy in satellite navigation systems depends on time-delay estimation (TDE) between satellite transmitted codes and local receiver replicas. This paper explores the fundamental limits of TDE accuracy of spread spectrum signals making use of estimation theory. In particular, this contribution derives some criteria to improve positioning accuracy in the additive white Gaussian noise (multipath-free) scenario, focusing on the (satellite) transmitter side of a direct sequence spread spectrum (DS-SS) system. Three different solutions based on the minimization of the variance of the TDE are presented. The first method derives a design criterion for the shaping pulse format. The second approach outlines a method to design binary pseudorandom spreading sequences. The third solution considers a joint shaping pulse-spreading code optimization to derive band-limited, non-binary spreading waveforms. Performance of the proposed solutions is compared with that of existing DS-SS signals for current satellite positioning systems. Possible countermeasures to the effects of multipath propagation are also discussed.     

Joint cooperative spectrum sensing and channel selection optimization for satellite communication systems based on cognitive radio

Cognitive radio has attracted considerable attention because of its ability to make full use of the available spectrum resources for wireless terrestrial communication networks. In addition, the satellite communication scenario, which requires a transparent air interface to integrated/hybrid Satellite–Terrestrial communication systems and provides a supplement for other multimedia services, will cause frequency scarcity. Satellite communication systems based on cognitive radio are available under scenarios that involve transmission with changing communications. In this paper, a cooperative spectrum‐sensing algorithm based on a time or bandwidth‐based cooperative spectrum‐sensing model of an integrated/hybrid cooperative satellite communication system is proposed. Moreover, the concept of weighted cooperative spectrum sensing is introduced. Compared with the traditional single‐user spectrum‐sensing algorithm, the cooperative spectrum sensing is able to cope with the interference to the primary user caused by a secondary user better. In addition, multiple earth stations that use some part of the bandwidth cooperatively to perform spectrum sensing throughout the whole frame can detect the presence of primary user in time. The satellite component combines the sensing results from earth stations to reach a final decision, and the optimal combination weights to maximize the detection probability of the secondary user are obtained. Numerical results that demonstrate the performance of the proposed algorithm are presented. Copyright © 2015 John Wiley & Sons, Ltd.     

群时延失真对扩频通信性能影响的仿真与分析

首先简要介绍了卫星通信中扩频系统的基本模型和表达式,给出了系统在失真信道中进行计算机仿真的基本模型。然后,利用通信系统仿真软件包ACOLADE,建立了扩频系统在群时延失真信道中的仿真模型,建立了群时延失真信道模型,进行了QPSK、QPSK＋DS、QPSK＋FH等体制在群时延失真信道的特性仿_真分析,最后得出了一些有一定参考价值的分析结果。     

基于特征扩频的卫星转发器频谱资源聚合研究

针对CDMA卫星通信系统受到严重外部干扰,且可连续使用的频谱受限问题,提出3种基于特征扩频的卫星转发器频谱聚合方案,实现多个转发器频谱高效聚合的同时对抗系统受到的外部干扰。通过仿真表明,所提方案能够克服基于现有认知多载波CDMA方法进行卫星转发器频谱聚合的设计复杂度较高、频谱聚合效率低的缺点,并且所提整体特征扩频方案在性能和支持用户数方面均优于另外2种多载波特征扩频方案,提高了系统对多个转发器的非连续频谱利用率,进而提升系统容量。     

基于认知无线电的WiMAX系统共存方案研究

如何利用广播电视频段及免授权频段中的空闲频谱、防止干扰和实现共存对WiMAX系统有重要意义.根据WiMAX系统标准,结合认知无线电技术,研究通过调整信号带宽和利用频谱池技术实现WiMAX系统共存.利用Matlab仿真软件.在移动WiMAX基带链路上,以频谱池思想为基础,对使用认知无线电前后的WiMAX系统性能进行了仿真...     

Space-Time Optimum Combining for CDMA Overlay for Personal Communications Systems

The requirement to suppress narrowband interferences in CDMA communication stems from the overlay concept, i.e., coexistence of different types of signals in the same frequency band. This paper describes the performance analysis of a direct-sequence (DS) CDMA personal communication system sharing a common spectrum with narrowband microwave radio links in the 1.85 to 1.99 GHz band. The coexistence of these two systems within the same frequency band will improve the overall spectrum efficiency, but will also cause interference to both systems. In this paper it is shown that joint spatial and temporal optimum combining provides an efficient means of improving the performance of the DS-CDMA system through cancellation of the narrowband signal and the co-channel interferences. The proposed space-time architecture provides degrees of freedom for both diversity and interference cancellation. It is shown that the joint space-time receiver is robust with respect to the narrowband interference signal bandwidth and its carrier frequency offset from the DS-CDMA carrier frequency.     

一种适于卫星定位与通信系统的扩频ALOHA信道模型

随着人们对通信需求的不断增长，带来了如何有效地利用频率问题，同时也产生了越来越多的多址技术。本文将扩频技术与随机ＡＬＯＨＡ通信方式相结合，提出了一种适于卫星定位与通信系统的扩频ＡＬＯＨＡ信道模型。并对此信道的信道利用率进行了计算，得到了好的结果。全文还对定位与通信构成一体化系统的可实现性做了详细描述。最后，简单介绍了双星定位及通信系统的定位原理。     

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.     

Non-regenerative satellite switched FDMA (SS/FDMA) payload technologies

Satellite switched frequency division multiple access (SS/FDMA) satellite systems are new adaptations of the basic FDMA architecture for multiple beam spacecraft. Present multibeam satellite systems feature on-board interbeam connections operating on a transponder channel basis, e.g. 72 MHz. SS/FDMA on board connectivity is based on much narrower channels and consequently achieves a much better utilization of spectrum resources whenever connectivity requirements are of the order of fractions of a transponder bandwidth. This work presents a critical analysis of various non-regenerative SS/FDMA satellite systems, identifies the technological requirements to be met in order to achieve the practical realization of SS/FDMA on-board processors and, finally, proposes two novel variable bandwidth variable centre frequency (VBVCF) demultiplexers with continuous and discrete reconfigurability.