Stochastic resonance is widely applied to detect weak signal in a strong noise background be-cause it can enhance the signal-to-noise ratio(SNR). A weak single frequency signal detection method based on under-sampling stochastic resonance is proposed to solve the problem that traditional stochastic resonance can be only applied to deal with small parameter signals. Stochastic resonance is successfully ex-panded into the applications of the large parameter signals on the basis of scale-transformation and retrieve technology in the under-sampling stochastic resonance. Moreover,the algorithm overcomes the limit that signal frequency must be more than 50 times of the sampling frequency in the second sample algorithm. The model of weak signal detection based on under-sampling stochastic resonance is put forward. Finally, detecting the weak single frequency signal under SNR=-27 dB background by the method proposed in this paper is simulated. The result proves the validity of the method. The sampling frequency in the method is much less than that in the traditional methods and this is helpful to apply stochastic resonance in improving the performance of the Costas loop.

In broadband satellite multimedia (BSM) system, burst time plan (BTP) is always periodically generated. We find that this method can have a great effect on the system response ability to bandwidth requests. A general analysis model of BTP generation method is given. An optimized BTP generation (O-BTPG) method is presented by deducing the optimal bandwidth allocation period (BAP) and bandwidth allocation latency (BAL) without considering the signaling overhead caused by BTP. Then a novel asynchronous BTP generation (A-BTPG) method in which the BTP is generated asynchronously according to the traffic load from users' bandwidth requests is proposed. Simulation results show that A-BTPG can flexibly realize a trade-off between the system response ability and BTP signaling overhead. What's more, it can be widely used in various regenerative onboard switching BSM systems.

According to the status that COMPASS system′s PNT(Position,Navigation,and Timing) is asymmetry in the worldwide,the polar constellation and rose constellation are proposed to enhance the COMPASS,and then their coverage performances are simulated and analysed.Furthermore,the structure and principle of enhanced COMPASS system are discussed.By using the index of position dilution of precision and the number of visible satellites,the performance of enhanced system is comparatively analysed.

Timeslots assignment can have a great impact on the bandwidth allocation efficiency in multi-frequency time division multiple access (MF-TDMA) satellite system. In this paper a multiple frequency channels reserved timeslots assignment algorithm is proposed for MF-TDMA user terminals (UTs) with real-time traffic. The scheme can reserve several frequency channels simultaneously for one UT and realize fast timeslots block searching within a MF-TDMA frame. Computational complexity analysis demonstrates the performance of the proposed method on computational efficiency. What's more, simulation results show that both channel utility and connection rejection ratio can be improved compared with existing algorithm.

Considering the scenario of cognitive radio Networks(CRN) single channel opportunistic spectrum access,a single channel opportunistic spectrum access model was established which provided CR QoS guarantee and also promised interference-free to primary radios(PR).The model aimed at maximizing the useful cognitive radio network(CRN) throughput which was a new metric defined.The minimum rate gap-based access strategy was proposed and the corresponding minimum rate gap based channel and power allocation(MRG-CPA) algorithm and MAC protocol was demonstrated.Simulation results show that MRG-CPA provides more useful CRN network throughput as well as improves the CR QoS guarantee rate than existing solutions such as the first Fit Deceasing algorithm,best fit deceasing algorithm and least rate requirement based channel and power allocation algorithm.

The machine-to-machine (M2M) communication enables information exchange between machine devices, which can be carried out without or with minimal human interaction. In this paper, we analyse the outage probability of satellite M2M communication system using amplify-and-forward (AF) and decode-and-forward (DF) relaying schemes. Both the channel feedback delay and multiple interferers at the relay and destination are taken into consideration. The channels of the two hops are modeled as Rayleigh and Rician, respectively. The closed-form outage probability expressions for both AF fixed-gain and DF relaying system are obtained, and the validness of our analytical results are verified by the Monte Carlo simulations. It is shown that the channel delay affects the outage probability performance more significantly compared with the interferences. It is also worthy to note that the DF relaying system provides better performance than AF fixed-gain relaying system, especially when the feedback delay is short. Moreover, it can be found that the performance gaps of the two relaying schemes become trivial as the feedback delay increases.

为满足多点波束宽带卫星系统各波束不同的业务需求,提高星上功率利用率,对多点波束卫星的功率分配进行优化。在充分考虑卫星下行链路信道条件的不同及各波束最小容量需求的基础上,以服务公平性和容量最大化为目标进行建模,提出了一种波束间功率优化分配算法OIBPA（optimized inter-beam pow-er allocation）,并采用凸优化理论对该优化算法进行分析。通过仿真分析,该算法与传统的功率分配算法相比,在考虑信道条件的基础上提高了卫星的功率利用效率,降低了计算复杂度,且可以根据业务优先级进行灵活地调整,适用于多点波束宽带卫星系统。

During the bandwidth on demand(BoD) procedure of the broadband satellite multimedia(BSM) system,the BoD performance is very sensitive to the bandwidth allocation period(BAP) and bandwidth allocation latency(BAL) by using periodical burst time plan generation(P-BTPG) method.The BoD model is given and the optimal-burst time plan generation(O-BTPG) method is presented by developing the optimal BAP and BAL.Then the large signaling overhead of O-BTPG is focused.An asynchronous burst time plan generation(A-BTPG) method which can generate the BTP asynchronously according to the bandwidth requirements is proposed.The expression of optimal schedule duration and schedule instant is developed,and the workflow is given.Two different bandwidth allocation algorithms were chosen to evaluate performance of the BTP generation methods.Simulation results show that A-BTPG method can be used widely.It can improve the bandwidth responsive ability of the system while controlling the BTP overhead.

本文首先介绍了南太平洋大学卫星远程教育网络USPnet的发展历史及现状,重点分析了网络由最初只能提供单向语音通信到目前支持交互式多媒体通信的发展历程;然后分析了USPnet的VSAT网络架构,主校区作为主站,各分校区作为远端站;最后介绍了USPnet提供的应用,包括交互式数据、语音通信和视频会议等。

本文主要介绍俄罗斯Gascom公司Yamal卫星通信系统的发展现状,并重点对系统中目前在轨的两颗卫星及将要发射的三颗卫星进行了阐述。

The bandwidth management issues in broadband multimedia satellite communication system using multiple frequency-time division multiple access (MF-TDMA) were concerned. The framework of bandwidth management structure was proposed in a hierarchical manner. Some key problems were reviewed from large scale, moderate scale and micro scale aspects respectively.

The existing resource optimization allocation strategies of multi-beam communication satellite don′t take the coupling relationship of power and bandwidth into consideration. In order to further improve the utiliza-tion of satellite resources,a joint optimization algorithm of power and bandwidth is proposed,which gives full consideration to the co-channel interference and the different traffic demands of each beam. This algorithm is proposed on the basis of the system fairness and can be solved by an iterative method. Compared with the tradi-tional fixed allocation method,the joint optimization algorithm is more flexible on the redistribution of on-board resources,which increases the system capacity and improves 10% of the traffic match ratio through simulation results. The joint optimization algorithm improves the efficiency of the on-board resource utilization.

Large area code(LAS) based on Hadamard Matrix and large loosely code based on Laurent Polynomial are firstly discussed,then the performance of LAS code is analysed,including duty ratio,correlation properties,the length of Interference Free Window(IFW) and total number.The normalized system capacity in LAS-CDMA system and traditional CDMA system is given by theoretical analysis,subsequently the BER performance of the LAS code and Gold code in quasi-synchronous CDMA systems is simulated.The simulations show that the LAS code has the characteristics of uniform IFW.The multiple access interference is smaller for the LAS code with different LA code.LAS-CDMA has advantages on normalized system capacity system over traditional CDMA system and BER performance is significantly better than that of application of Gold code.

宽带多媒体卫星(BSM)系统是以传输高速宽带多媒体业务为典型特征的一类新型卫星通信系统,此类系统与传统卫星通信系统最大的不同在于承载的业务由低速的数据及话音(64kbit/s以下)转变为图像、声音、视频相结合的高速率、交互式宽带多媒体业务,这类业务也称为卫星宽带多媒体业务. 1概述 针对系统终端的传输能力,欧洲电信标准化组织基于终端所能够提供的基本信息速率对宽带多媒体卫星给出了界定:①固定终端(如小型甚小口径天线等)应不低于2.048Mbit/s;②移动终端(如手持机等)应不低于64kbit/s;③可搬移式终端(如便携站等)应与固定终端大体相同.

根据既不对主用户（Primary Radio user,PR）产生干扰,又对认知无线电用户（Cognitive Radio user,CR）提供QoS保证的原则,将认知无线电网络（Cognitive Radio Network,CRN）中多信道接入频谱共享问题建模为混合整数非线性规划。采用多级功率限制保证PR不被干扰,以CR物理层能够提供的速率作为信道和功率分配的依据,提出将能够为CR提供最大传输速率的信道分配给该CR的分配策略,将混合整数非线性规划转化为整数线性规划,并给出集中式启发算法和基于功率速率比（Power Rate Ratio,PRR）最小的分布式启发算法求解该整数线性规划。仿真结果表明,文中给出的算法能够提供较高的CRN吞吐量和较好的CR用户QoS保证。

In this paper, Symbol-Error-Rate (SER) performance analysis is provided for a Decode-and-Forward (DF) cooperative scheme in satellite mobile channel environment. We present a satellite mobile cooperative communication system model and derive two generalized error probability expressions with Cyclical Redundancy Check (CRC) or not. We also derive and simulate SER of the proposed system over different satellite mobile channels. The results show that the analytical results are in great accordance with the ones obtained by simulation. Also, it was shown that, whether or not adopt CRC depends on the channel link quality between the source node and the relay node.

We consider the problem of transmit power allocation for the multi-beam broadband multimedia satellite communication systems. An efficient power allocation strategy based on the different traffic demand of each beam is proposed to guarantee the fairness of the system. First we solve this convex optimization problem by dual methods, and then use a heuristic algorithm to obtain the optimum power allocation of each beam, and also compare the capacity distribution of each beam when the link conditions (rain attenuation) are different.

The rapid development of modern wireless communication technology requires more and more spectrum which renders the transaction from static spectrum allocation to dynamic spectrum allocation.Aimed at the question that multiple networks access an coordinated spectrum access spectrum(CSAB) through a central spectrum broker,an improved dynamic spectrum allocation mechanism was proposed based on real-time spectrum demand and offer mapping(RT-DOM).As contrast with general sequential dynamic spectrum allocation(S-DSA) mechanism,the RT-DOM focuses on the spectrum requirement change between two consecutive dynamic periods,and maps the released spectrum(spectrum offer) and the new spectrum demand,in order to make less the spectrum handover than S-DSA.And the simu-lation results show that the spectrum handover reduces at least 75% while allocation gain reduces very little.

The Burst Time Plan (BTP) generation is the key for resource allocation in Broadband Satellite Multimedia (BSM) system. The main purpose of this paper is to minimize the system response time to users’ request caused by BTP generation as well as maintain the Quality of Service (QoS) and improve the channel utilization efficiency. Traditionally the BTP is generated periodically in order to simplify the implementation of the resource allocation algorithm. Based on the analysis we find that Periodical BTP Generation (P-BTPG) method cannot guarantee the delay performance, channel utilization efficiency and QoS simultaneously, especially when the capacity requests arrived randomly. The Optimized BTP Generation (O-BTPG) method is given based on the optimal scheduling period and scheduling latency without considering the signaling overhead. Finally, a novel Asynchronous BTP Generation (A-BTPG) method is proposed which is invoked according to users’ requests. A BSM system application scenario is simulated. Simulation results show that A-BTPG is a trade-off between the performance and signaling overhead which can improve the system performance insensitive to the traffic pattern. This method can be used in the ATM onboard switching satellite system and further more can be expended to Digital Video Broadcasting-Return Channel Satellite (DVB-RCS) system or IP onboard routing BSM system in the future.

Focused on the multimedia application,the CFDAMA（Combined Free/Demand Assigned Multiple Access） protocol was improved to RA-CFDAMA.RA-CFDAMA is easier to realize in the onboard switching broadband satellite system compared with the previous one.Simulation shows that RA-CFDAMA performs better in the transmission delay between terminals.