Concurrent development and verification of an all‐software baseband for satellite ground operations

Communication systems are adopting all‐software architectures, because of their scalability, extensibility, flexibility, and cost‐effectiveness. This paper introduces a concurrent approach to the development and verification of baseband systems for satellite ground operations based on the behaviour‐driven development methodology. The open‐source GNU Radio development kit is used for developing the software‐defined radio baseband signal processing, as well as simulating the satellite and realistic channel impairments. The system performance at the end shows deviations of less than 1 dB with respect to the ideal performance and the Green Book standards specified by the Consultative Committee for Space Data Systems.     

一种卫星地面站伺服跟踪测控软件的实现

根据卫星小型移动式地面站的特点,开发了一种卫星伺服跟踪测控软件。本软件依据卫星轨道参数控制伺服跟踪系统,完成对卫星的实时跟踪。它以星载任务管理为核心,利用高优先级线程来完成伺服数据发送、采集和存储工作,采用tchart组件绘制了伺服跟踪效果图,可对伺服跟踪效果进行测试。实际运行效果表明,该软件能满足任务要求,模块化程度高,具有良好的扩展性。     

卫星载荷软件的层次化设计

介绍了卫星技术的发展对未来载荷软件设计的要求,提出了层次化设计这样一种新的思路.通过对载荷软件功能的分析、提炼和抽象,将载荷软件划分为相对独立的3个层次,即系统层、协议层和应用层,采用这样的分层架构设计,可以最大限度地实现软件的高内聚、低耦合,提高软件的可移植性、可重用性和可靠性,节省研制时间及成本.     

基于工作流技术的柔性软件系统开发

软件柔性技术是目前软件开发研究的热点之一,通过对软件系统中柔性要素的分析,引入柔性工作流技术模型,建立了一个柔性软件开发过程,即通过抽象、转移和重构三个阶段对软件的系统进行柔性开发,并结合多年实际开发工作,对软件系统的柔性化进行了详细阐述.     

LTE‐based satellite communications in LEO mega‐constellations

The integration of satellite and terrestrial networks is a promising solution for extending broadband coverage to areas not connected to a terrestrial infrastructure, as also demonstrated by recent commercial and standardisation endeavours. However, the large delays and Doppler shifts over the satellite channel pose severe technical challenges to traditional terrestrial systems, as long‐term evolution (LTE) or 5G. In this paper, 2 architectures are proposed for a low Earth orbit mega‐constellation realising a satellite‐enabled LTE system, in which the on‐ground LTE entity is either an eNB (Sat‐eNB) or a relay node (Sat‐RN). The impact of satellite channel impairments as large delays and Doppler shifts on LTE PHY/MAC procedures is discussed and assessed. The proposed analysis shows that, while carrier spacings, random access and RN attach procedures do not pose specific issues and hybrid automatic repeat request requires substantial modifications. Moreover, advanced handover procedures will be also required due to the satellites' movement.     

基于软件无线电技术的通用卫星模拟器设计

航天测控站配备的传统的卫星模拟器功能单一,通用性差,已经不能满足目前卫星发展的多种测控体制、多种卫星平台的实际需求.为满足这一需求,研究了一种基于软件无线电技术的通用卫星模拟器,在70 MHz中频上进行数字化处理,实现了多体制、多星共用的功能.该卫星模拟器具有体积小、精度高、稳定性好、操作维护简单的特点.     

A discrete‐components millimeter‐wave satellite beacon receiver for Q‐band propagation experiment

Ever increasing bandwidth requirements in satellite communications continuously push the frequency limits. Q‐ band (33 – 50 GHz) is the next frequency band to be populated; however, at these frequencies, the Earth's troposphere (weather) profoundly alters the radio propagation conditions. Therefore, in order to properly plan radio links, accurate statistical models of radio channels are necessary. These statistical models are built upon empirical data, ie, measurements, which are furthermore used to design appropriate Propagation Impairment Mitigation Techniques. The Q‐ band lacks such data, hence the statistical models are inadequate. To address this problem, we propose a cost‐effective, easy to replicate Q‐ band beacon receiver to leverage the Alphasat propagation campaign. We present a step‐by‐step implementation process of the receiver's fundamental part, a Low‐Noise Block, which translates input 39.402 GHz signal into 162 MHz output signal with a conversion gain of 52 dB. The receiver furthermore utilizes software define radio for signal processing and other data manipulation. Here, we describe the receiver implementations in great details, supplementing the crucial parts with laboratory validation results. Finally, we show 2 example datasets, showing usual data obtained during heavy showers and on a quiet day, respectively.     

Call admission control for non‐geostationary orbit satellite networks and other capacity‐varying networks

Many networks, such as non‐geostationary orbit satellite (NGOS) networks and networks providing multi‐priority service using advance reservations, have capacities which vary over time for some or all types of calls carried on these networks. For connection‐oriented networks, call admission control (CAC) policies which only use current capacity information may lead to excessive and intolerable dropping of admitted calls whenever the network capacity decreases. Thus novel CAC policies are required for these networks. We present the admission limit curve (ALC) and prove it is a constraint limiting the conditions under which any causal CAC policy may admit calls and still meet call dropping guarantees on an individual call basis. The ALC also leads to a lower bound on the call blocking performance achievable by any causal CAC policy which provides dropping guarantees to individual calls. Also, we introduce a new CAC policy which uses knowledge of future capacity changes to provide dropping guarantees on an individual call basis and which achieves blocking performance close to the lower bound. Copyright © 2000 John Wiley & Sons, Ltd.     

Distributed object‐oriented switching system software platform design

Key technologies are presented and evaluated for establishing a distributed object‐oriented switching system platform. This platform is based on CORBA, which can enhance software productivity and system scalability and is thus widely used in the information technology field. Conditions and requirements specific to switching systems, such as very high‐performance and non‐stop operation, are analysed and mapped to the main elements of CORBA. How to deploy and bind objects so as to minimize the processing load is clarified. Mechanisms that guarantee system reliability (saving calls in service when a system failure occurs and avoiding the spread of faults) are also presented. Evaluation of the number of dynamic program steps for systems using fully compliant CORBA, improved CORBA, and a proprietary high‐speed object‐request broker (ORB) shows that constructing a communication switching system by using the high‐speed ORB approach is sufficient, but CORBA‐compliant approaches should be used to provide an interoperable interface for communicating with external compliant systems. Copyright © 2001 John Wiley & Sons, Ltd.     

Adaptive frequency‐hopping schemes for CR‐based multi‐link satellite networks

In this paper, we study two dynamic frequency hopping (DFH)–based interference mitigation approaches for satellite communications. These techniques exploit the sensing capabilities of a cognitive radio to predict future interference on the upcoming frequency hops. We consider a topology where multiple low Earth orbit satellites transmit packets to a common geostationary equatorial orbit satellite. The FH sequence of each low Earth orbit–geostationary equatorial orbit link is adjusted according to the outcome of out‐of‐band proactive sensing scheme, performed by a cognitive radio module in the geostationary equatorial orbit satellite. On the basis of sensing results, new frequency assignments are made for the upcoming slots, taking into account the transmit powers, achievable rates, and overhead of modifying the FH sequences. In addition, we ensure that all satellite links are assigned channels such that their minimum signal‐to‐interference‐plus‐noise ratio requirements are met, if such an assignment is possible. We formulate two multi‐objective optimization problems: DFH‐Power and DFH‐Rate. Discrete‐time Markov chain analysis is used to predict future channel conditions, where the number of states are inferred using k‐means clustering, and the state transition probabilities are computed using maximum likelihood estimation. Finally, simulation results are presented to evaluate the effects of different system parameters on the performance of the proposed designs.     

Dynamic pricing for load‐balancing in user‐centric joint call admission control of next‐generation wireless networks

Next‐generation wireless networks (NGWN) will be heterogeneous, comprising of a number of radio access technologies (RATs) co‐existing in the same geographical area. In NGWN, joint call admission control (JCAC) algorithms are required to select the most appropriate RAT for each incoming call. It is envisaged that these JCAC algorithms will be user‐centric (i.e. will consider users' preferences in making RAT selection decisions) in order to enhance user satisfaction. However, user‐centric JCAC algorithms can lead to highly unbalanced traffic load among the available RATs in NGWN because users act independently, and most of them may prefer to be connected through a particular RAT. Highly unbalanced traffic load in NGWN will result in high overall call blocking/dropping probability and poor radio result utilization. To address this problem, we propose dynamic pricing for balancing traffic load among available RATs in heterogeneous wireless networks where users' preferences are considered in making RAT selection decisions. By dynamically adjusting the service price in each of the available RATs, the proposed user‐centric JCAC scheme evens out the unbalanced traffic load caused by independent users' preferences. The JCAC scheme uses fuzzy multiple attribute decision‐making (MADM) technique to select the most appropriate RAT for each incoming call. We develop a Markov model to evaluate the overall call blocking/dropping probability and percentage load in each RAT in heterogeneous wireless networks. Performance of the proposed JCAC scheme is compared with that of a scheme that does not use dynamic pricing. Simulation results are given to show the effectiveness of the proposed JCAC scheme. Copyright © 2009 John Wiley & Sons, Ltd.     

Bandwidth‐constrained digital pre‐compensation technique for multi‐carrier satellite communications

A wide variety of imperfections impact end‐to‐end performance in multiple‐carrier per transponder transparent satellite links. Analysis of the link architecture leads to the identification of the sources and characteristics of distortion experienced by a typical multi‐carrier signal. This paper introduces a new remote pre‐compensation technique that takes this analysis into account to compensate for the specific distortion that occurs in the satellite channel. The proposed technique succeeds in compensating both linear and nonlinear channel distortions while overcoming the numerous challenges associated with remote waveform predistortion. Excellent linearisation performance has been observed across a wide range of link scenarios, even for high power amplifiers already linearised in the analogue domain. In addition, through an extensive end‐to‐end simulation campaign and a field programmable gate array implementation of the new algorithms, feasibility of the technique has been verified. Copyright © 2015 John Wiley & Sons, Ltd.     

一种卫星定位组件测试软件的设计与实现

卫星定位组件作为一门较新项目,同时作为对可靠性要求至高的高科技武器产品中的重要组件,在保证产品的可靠性方面,需要构建高覆盖面的组件测试方法,通过充分测试暴露产品问题才能更好地提高产品的性能,保证可靠性。卫星定位组件测试软件利用串口技术能够实时接收解调组件的输出数据,直观显示所有定位数据信息,为组件开发者判断组件的工作状态提供依据,同时软件要有数据存储和二次计算的能力,处理能力能够覆盖组件所有测试参数。     

A novel MAC protocol for IDMA‐based multi‐beam satellite communication systems

Considering the limitations of satellite communication systems and advantages of new emerging interleave‐division multiple access (IDMA) technology, IDMA is introduced into the satellite systems, providing a new solution for multiple access techniques of satellite systems. To further validate the IDMA into satellite systems, a novel medium access control (MAC) scheme is proposed. In the random access channel, the interleave‐division slotted ALOHA method is adopted to alleviate the collision of access requests. Furthermore, a novel minimum power allocation scheme based on signal‐to‐interference‐plus‐noise ratio (SINR) evolution is proposed to maximize the capacity of such an interference‐sensitive system. By virtue of SINR evolution, our proposed scheme can accurately estimate multi‐user detection efficiency with low computational cost and further reduce the transmitted power, illustrating the high power efficiency of IDMA. To further enhance the performance of the MAC protocol, an effective call admission control scheme considering the effect of power control error is designed and combined into our MAC protocol. Analysis and simulation results show that, by taking full advantage of the chip‐by‐chip multi‐user detection technique, the proposed IDMA MAC protocol achieves high throughput and low average packet delay simultaneously, with low onboard processing complexity in the multi‐beam satellite communication systems. Copyright © 2013 John Wiley & Sons, Ltd.     

Subgrouping‐based multicast transmission over high‐throughput satellite systems with beam cooperation

This paper investigates the multicast transmission for multicast services in high‐throughput satellite (HTS) systems. Considering the multibeam multicast feature of HTSs, cooperative transmission among beams is involved in to improve the efficiency of the multicast transmission. Since the multicast transmission rate depends on the worst user channel state, all the users experience an unreasonably low rate. In this situation, subgrouping techniques are employed to increase transmission rates of users. A subgrouping‐based multicast transmission problem aiming at maximizing the lowest transmission rate of the users is studied to guarantee fairness among users. We formulate the problem as a max–min optimization problem and propose two low‐complex subgrouping algorithms for this problem. Additionally, we also consider multicasting in a single beam and devise a two‐layer transmission scheme for it. In the performance evaluation part, besides the impact of parameters on subgrouping performance, we analyze the performance and the computational complexity of the proposed algorithms. The results indicate that the two subgrouping algorithms can achieve favorable performance with low complexity.     

Priority‐based adaptive routing in NGEO satellite networks

In a non‐geostationary satellite constellation with inter satellite links (ISLs), there could be many shortest paths between two satellites in terms of hop count. An efficient routing algorithm should effectively use these paths in order to distribute traffic to ISLs in a balanced way and to improve the performance of the system. This paper presents and evaluates a novel priority‐based adaptive shortest path routing (PAR) scheme in order to achieve this goal. PAR sets the path towards the destination in a distributed manner, using a priority mechanism depending on the past utilization and buffering information of the ISLs. Moreover, to avoid unnecessary splitting of a flow and to achieve better utilization of ISLs, enhanced PAR (ePAR) scheme is proposed. This paper evaluates performance of the proposed techniques by employing an extensive set of simulations. Furthermore, since there are a number of ePAR parameters that should be adjusted depending on the network and traffic characteristics, a detailed analysis of ePAR scheme is provided to form a framework for setting the parameters. This paper also includes a method for adaptation of the proposed algorithms to minimum‐delay path routing. Copyright © 2006 John Wiley & Sons, Ltd.     

An anti‐repeater‐jamming approach based on blind source separation for the downlink of satellite communication systems

In this paper, an anti‐jamming approach is proposed for the downlink of satellite communication systems when encountering a hostile repeater‐jamming. Based on blind source separation, this approach can eliminate repeater‐jamming by separating the mixtures of the communication signals and the repeater‐jamming. Meanwhile, oversampling method is employed to transform the underdetermined mixing of signals into a determined mixing for facilitating the separation. In the simulations, the symbol error ratio (SER) of the separated communication signals can approximate the theory SER, and the anti‐repeater‐jamming capacity can arrive to nearly 28 dB.     

An anonymous biometric‐based remote user‐authenticated key agreement scheme for multimedia systems

We analyze the security of the Li et al . authentication scheme and show its vulnerability to off‐line password‐guessing and replay attacks. We design a new anonymous authentication scheme. The proposed scheme not only removes the drawback of the scheme of the Li et al . scheme but also protects user's anonymity. Moreover, we show validity of our proposed scheme using Burrows, Abadi, and Needham logic. Our scheme is comparable in terms of the communication and computational overhead with related schemes. Copyright © 2015 John Wiley & Sons, Ltd.     

Perfect match model‐based link assignment to design topology for satellite constellation system

In satellite constellation network, the satellites visible from one satellite are more than communication terminals (CTs) equipped. Each inter‐satellite link (ISL) would occupy one CT on each of two satellites connected by this ISL. Therefore, a fundamental problem considering link assignment is how to assign limited CTs for each satellite to establish ISLs with its visible satellites. Link assignment scheme based on perfect match model (LAS‐PMM) is proposed to make full use of huge bandwidth provided by CT. In LAS‐PMM, the problem of assigning all the CTs of each satellite to establish ISLs is modeled as a perfect matching problem, where a perfect matching is searched over a mixed complete bipartite graph. Simulation results show that LAS‐PMM is better than the regular and greedy LASs, in terms of CT utilization and average node‐to‐node distance. Copyright © 2015 John Wiley & Sons, Ltd.