共查询到19条相似文献,搜索用时 250 毫秒
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为了应对灰霾对星地量子通信信道所带来的突发性干扰,根据灰霾天气下量子信号在自由空间中的衰减指数,本文提出了一种基于信号功率衰减最低的最优链路量子卫星切换策略。当目前的星地链路参数满足切换条件时,地面用户通过对不同信道中量子信号功率衰减系数的比对,测试到最小衰减卫星链路,基于对光子态Bell基的测量,完成卫星间的量子纠缠交换,建立新的纠缠信道,保证通信在切换过程中的连续性。仿真结果表明,当系统呼损率为5%,能见度为1km,地面用户数分别为50、100、300,轨道高度为300km和1400km时,量子卫星的切换成功率分别为95%、93.6%、91.8%和92%、90%、87%。由此可见,本策略能够在保证通信可靠性的前提下,实现星地间量子信道的平稳切换,提高量子卫星通信系统在灰霾背景下链路的有效性。 相似文献
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空间光骨干网络是我国空间信息网络的核心。为了对空间光骨干网络中的协议体系、网络架构和关键技术进行可行性验证,开发了基于OPNET和STK(satellite tool kit,卫星工具包)联合的空间光骨干网络仿真平台。设计了由4颗GEO卫星组成的天基骨干网、由10颗LEO卫星组成的天基接入网;开发了由物理层到应用层的光网络协议仿真模型和LEO、GEO、地面站3种节点进程模型,对光骨干网络进行了仿真测试。仿真结果表明:空间光骨干网络最大时延为5.48 s,最小为0.35 s,网络全局平均时延为1.06 s,地面站实时吞吐量最大值为0.88 Gb/s,最小为0.3 Gb/s,证明该平台可准确模拟空间光骨干网络功能,满足空间业务高效传输的需求,为空间光骨干网络性能验证提供仿真平台支持。 相似文献
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低轨道量子卫星是构建全球天地一体化量子保密通信网的重要组成部分。单颗低轨量子卫星服务时间有限,为了保证卫星与地面用户之间的持续通信,地面终端需要及时切换至其他可供服务的卫星。为了解决降雪环境干扰下地面多用户量子卫星切换场景下的阈值判决问题,分析了大气雪环境对量子星地链路的衰减影响,提出了一种基于演化博弈的多属性量子卫星切换策略。根据用户的带宽、卫星剩余服务时间及链路衰减三个属性定义效用函数,根据星间传输时延、信道纠缠度定义开销函数,最终得到用户的收益函数,建立演化博弈切换模型。仿真结果表明,该策略具有稳定性和公平性,能够有效均衡卫星的负载,且与基于最低链路衰减和最优纠缠度的单属性切换策略相比,切换成功率分别提升了1.2%和1.5%,这对未来降雪干扰环境下低轨量子卫星网络的多用户动态切换有一定的参考意义。 相似文献
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在分析星地链路几何结构及传播模型的基础上,研究基于联合代数重建技术的星地链路反演二维垂直降雨场的方法.利用实测降雨资料构建3类降雨场,并搭建3条17 GHz垂直极化星地链路进行数值仿真.实验结果表明:单星地链路无法实现二维垂直降雨场的重构,反演场与真实场的相关系数分别为0.556,0.504和0.364;基于双星地链路的反演结果和真实场的相关系数均高于0.98,平均偏差分别为0.122, 0.159和0.537 mm/h,欧式距离均低于0.9 mm/h,熵的相对误差均小于1.6%,基本实现了二维垂直降雨场的反演;三星地链路的应用进一步提升了反演精度,相关系数接近于1,能够精准重构降雨场.实验结果验证了基于星地链路的垂直降雨场反演方法的可行性、准确性和有效性.星地链路的架设和维护简单,探测降雨范围广,易于在高原、山区、海岛等传统地面观测资料缺失的地区使用,可以作为已有降水测量手段的补充. 相似文献
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实际星地光通信系统的发射光束为高斯型的情况下,跟瞄误差和大气闪烁是星地激光链路中的主要信道噪声源。在结合两者对系统性能影响的前提下,对星地激光通信链路进行了理论分析和模型建立。基于该模型对星地激光链路中光束发散角与跟瞄误差之比的优化选择问题进行了研究。结果表明:对于上行链路,在不同误码率需求下都存在一个光束发散角与跟瞄误差的最佳比值,使得上行链路余量最大;对于下行链路,在不同误码率要求下均存在一个光束发散角与跟瞄误差的最佳比值,使得下行发射光功率的需求最小。利用最优化方法和最小二乘法拟合,得到星地激光链路中光束发散角与跟瞄误差的最佳比值和系统误码率的经验公式。 相似文献
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Optical burst switching (OBS) is an optical switching paradigm which offers a good tradeoff between the traditional optical circuit switching (OCS) and optical packet switching (OPS) since it has the relatively easy implementation of the first and the efficient bandwidth utilization of the second. Hence, OBS is a promising technology for the next generation optical Internet. A buffer-less OBS network can be implemented using ordinary optical communication equipment without the need for either wavelength converters or optical memories. In an OBS network, burst-loss performance is a critical concern. In OBS, the data-burst transmission is delayed by an offset time (relative to its burst control packet (BCP), or header) and the burst follows its header without waiting for an acknowledgment for resource reservation. Thus, a burst may be lost at an intermediate node due to contention, which is generally resolved according to the local routing and bandwidth information. The routing table maintained in each OBS node is generally pre-computed and fixed to forward the data bursts. Such a static forwarding feature might have limited efficiency to resolve contentions. Moreover, a burst may be lost and the network may be congested when a network element (e.g., fiber link) fails. In this paper, an efficient integrated scheme based on dynamic routing and burst segmentation has been proposed to improve reliability of data transport and network load balancing in optical burst switched networks. Simulation results demonstrate that the proposed approach reduces effectively blocking probability and hence contention. Further, it provides end-to-end throughput performance also. Hence, it establishes an appropriate tradeoff between loss rate and end-to-end throughput. 相似文献
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调研了传统光传(FBL)网络的几种拓扑结构, 就可靠性和实时性两方面对它们进行了分析和比较。选择采用一个包含256个节点的mesh光交换网络, 它具有冗余拓扑结构能承受3处链路故障, 保证了网络的可靠性。以网络中发生链路故障的数目, 及多个故障同时发生时故障的邻近程度来衡量网络故障的严重性。对所有链路故障情形进行仿真, 测试端到端的通信延迟。仿真结果表明, 采用这种网络拓扑结构的光传网络, 即使在发生较为严重的故障的情况下, 端到端通信路由的跳数增加不大, 仍能满足实时通信的要求。 相似文献
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To improve the restoration performance of a multicast service of multi-protocol label switching transport profile (MPLS-TP) enabled optical network,this letter proposes a local-node initiated fast restoration (LNIFR) scheme for MPLS-TP optical multicast service.The proposed scheme allows the local node to establish a segment of fast loopback label switch path by the local node along the upstream of the failed node or link to the nearest downstream node.The fast restoration of optical multicast trees is realized through this part restoration,which focuses on failed node or link.Simulation analysis and results demonstrate that the new scheme outperforms the other schemes in terms of restoration time and success rate. 相似文献
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We propose an all-optical hybrid network composed of optical code division multiple access (CDMA) rings interconnecting through a reconfigurable wavelength division multiplexing (WDM) metro area ring. This network retains the advantages of both the optical CDMA and WDM techniques, including asynchronous access and differentiated quality of service, while removing the hard limit on the number of subscribers and increasing network flexibility. The all-optical network is enabled by using nonlinear optical loop mirrors in an add/drop router (ADR) that performs code conversion, dropping, and switching asynchronously. We experimentally demonstrate the functionalities of the ADR in the proposed scheme asynchronously and obtain error-free performance. The bit-error rate measurements show acceptable power penalties for different code routes. 相似文献
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The hybrid optical-wireless access network (HOWAN) is a favorable architecture for next generation access network. It is an optimal combination of an optical backhaul and a wireless front-end for an efficient access network. In this paper, the HOWAN architecture is designed based on a wavelengths division multiplexing/time division multiplexing passive optical network (WDM/TDM PON) at the optical backhaul and a wireless fidelity (WiFi) technology at the wireless front-end. The HOWAN is proposed that can provide blanket coverage of broadband and flexible connection for end-users. Most of the existing works, based on performance evaluation are concerned on network layer aspects. This paper reports physical layer performance in terms of the bit error rate (BER), eye diagram, and signal-to-noise ratio (SNR) of the communication system. It accommodates 8 wavelength channels with 32 optical network unit/wireless access points (ONU/APs). It is demonstrated that downstream and upstream of 2 Gb/s can be achieved by optical backhaul for each wavelength channel along optical fiber length of 20 km and a data rate of 54 Mb/s per ONU/AP along a 50 m outdoor wireless link. 相似文献
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In this paper we present an analytical model, which considers the effects of the switching time on the network performance in service differentiated optical packet/burst switching (OPS/OBS) networks. Our results indicate that the switching time must be less than 10 % of the packet/burst duration in order to avoid any significant reductions in the network performance. Furthermore, regarding a network with full wavelength conversion, we show that the benefits of statistical resource sharing are almost non-existent for low priority traffic when the switching time is large. 相似文献
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Jianxin Ma Ruijiao Zhang Junjie Zhang Xiangjun Xin 《Fiber and Integrated Optics》2013,32(5-6):217-229
AbstractA novel full duplex fiber wireless link providing alternative wired and 60-GHz wireless access is proposed based on a polarization orthogonal dual-tone optical millimeter-wave signal. In a hybrid optical network unit, the downlink optical signal can be decomposed as a single-sideband optical millimeter-wave signal (baseband optical signal) for wireless (wired) access by a polarization controller and polarization beam splitter. The uplink optical carrier abstracted from the downlink optical signal makes the hybrid optical network unit free from the optical source. The simulation results show that both downlinks and uplinks for either wired or wireless access can maintain quite good performance over 60 km of fiber. 相似文献
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Optical burst switching is a switching technology that is able to provide viable switching for optical internet with the present day technology. This paper presents a new medium access protocol for wavelength division multiplexing based optical burst switched metro ring network namely distributed queue optical burst switched ring (DQOBSR). It is a slotted, distributed queue access protocol with fixed bus structure and simple wavelength assignment. The topology consists of two unidirectional, counter rotating rings and the medium access protocol is based on distributed queuing. The protocol provides zero blocking with acceptable access delays. A mathematical model is also presented to determine the mean access delay which is the important performance parameter for the protocol. The simulation and model based results are compared and found to be in good agreement. 相似文献