共查询到20条相似文献,搜索用时 156 毫秒
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对流层散射通信信道建模及系统性能仿真 总被引:2,自引:1,他引:1
对流层散射通信是一种利用对流层媒质的不均匀性来实现超视距通信的方式.在分析对流层散射信道的统计特性的基础上,根据WSSUS假设建立了快衰落特性下的散射信道仿真模型,并进行了系统性能的实验仿真.同时通过理论计算,得出了该信道误码率的理论曲线,并与仿真结果进行比较,证明了对流层散射信道模型的合理性,该模型为分析系统的性能提供了一个有效的系统平台. 相似文献
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对流层散射通信是一种超视距无线通信方式,其传输速度、传输质量都与其他通信方式相比具有绝对的优势,在军事领域中通信传输方面占据着重要的地位.本文主要针对ITU-R617和NBS-101两种预计方式对流层散射通信传输损耗进行分析,明确不同应用模式下对流层散射通信传输损耗的实际情况,为对流层散射通信传输的研究提供了可靠的研究依据. 相似文献
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基于对流层大气不均匀体散射机制的对流层散射通信是微波超视距通信的一种重要方式。对于对流层散射通信系统,其超视距远距离通信能力由传播路径上天线波束公共体积内具有不同几何尺度和介电特性的不均匀散射体所确定。针对对流层散射通信电路几何参数的设计需求,通过构建对流层散射超视距路径模型,分析了对流层散射通信系统随收发天线仰角及收发点距离变化时公共散射体的离地高度、特征尺度及传播路径损耗特性,其计算结果可用于对流层散射实验设计和超视距通信性能分析参考。 相似文献
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大气波导传播现象研究及通信应用设想 总被引:1,自引:0,他引:1
对流层中的大气波导是一种支持高性价比超视距通信的优质通信信道资源。介绍了大气波导的陷获折射传播机制及波导分类;基于华北地区、黄海海域典型链路试验结果,研究了大气波导与对流层散射双模式传播现象,分析了大气波导的存在性、信道传输特性和通信可用性;鉴于大气波导低损耗高电平、不连续但有日变化趋势性发展规律的特点,提出波导/散射联合超视距弹性通信技术及基于大气波导的容中断伺机通信技术设想,其对波导资源的高效利用可支持超视距通信效能的显著提升。 相似文献
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Optimal mode selection and synchronization for robust videocommunications over error-prone networks 总被引:1,自引:0,他引:1
Cote G. Shirani S. Kossentini F. 《Selected Areas in Communications, IEEE Journal on》2000,18(6):952-965
We describe an effective method for increasing error resilience of video transmission over bit error prone networks. Rate-distortion optimized mode selection and synchronization marker insertion algorithms are introduced. The resulting video communication system takes into account the channel condition and the error concealment method used by the decoder, to optimize video coding mode selection and placement of synchronization markers in the compressed bit stream. The effects of mismatch between the parameters used by the encoder and the parameters associated with the actual channel condition and the decoder error concealment method are evaluated. Results for the binary symmetric channel and wideband code division multiple access mobile network models are presented in order to illustrate the advantages of the proposed method 相似文献
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利用大气散射效应,无线紫外(UV)通信能够提供非视距的无线光通信.推导了紫外无线通信信道的脉冲响应近似解析表达式,以此研究紫外信道的特性.得出了信道长度,码间干扰和信道误码率与收发机光学几何结构,数据速率的关系.研究表明,信道带宽和时延扩展主要取决于大气条件,即大气衰减系数,同时得到了信道容量与衰减系数,通信距离的关系... 相似文献
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为了掌握基于椭圆球面波的非正弦通信短波信道误码率性能,比较不同通信体制短波信道误码率性能的优劣,对Watterson短波信道模型原理进行了分析,根据Watterson短波信道模型原理,结合基于椭圆球面波的非正弦通信特点,提出了基于椭圆球面波的非正弦通信短波信道仿真方法,并对短波信道误码率性能进行了仿真。理论分析和仿真结... 相似文献
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在卫星移动通信环境下,由于信道时变特性以及巨大的往返传输延迟,极大地限制了卫星自适应编码调制(adaptive coding and modulation)技术的应用.为了解决这个问题,根据卫星移动通信上下行链路的视线信道分量满足近似互易性的特点,本文提出了一种基于部分信道信息的自适应调制编码方法.在满足平均发射功率和平均比特错误率的约束条件下,导出了最优的自适应编码调制策略和功率分配方法.提出的方法克服了现有自适应方法的局限性,同时,通过频谱效率性能的仿真验证了提出方法的有效性. 相似文献
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Land mobile satellite communication systems at Ka/K band (30/20 GHz) are attracting more and more attention to researchers because of its frequency band availability and the possibility of using small earth stations and satellite antennas for the systems. However, the Ka/K-band communications also give significant challenges in the system design due to severe channel impairments expected from the satellite links. In this paper, K-band channel characteristics are studied and compared with those at L band. The channel is modeled as Rayleigh multipath fading with the line-of-sight (LOS) component following a lognormal distribution. The first and second-order statistics of the fading channel are studied. Dual-space diversity reception is investigated to combat the flat channel fading. The bit error rate performance of coherent binary phase shift keying (BPSK) with ideal bit and carrier phase synchronization over the fading channel at K band is evaluated theoretically and verified by computer simulations in the case with and without diversity reception. 相似文献
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In this paper, a uniform circular antenna array (UCAA) combining genetic algorithm (GA) or asynchronous particle swarm (APSO) for finding out global maximum of multi-objective function in indoor ultra-wideband (UWB) communication system is proposed. The algorithm is used to synthesize the radiation pattern of the directional UCAA to reduce the bit error rate (BER), to increase received energy and channel capacity in indoor UWB communication system. Using the impulse response of multipath channel, the BER of the synthesized antenna pattern on binary antipodal-pulse amplitude modulation system can be calculated. Based on topography of the antenna and the shooting and bouncing ray/image techniques, the synthesized problem can be reformulated into a multi-objective optimization problem which would be solved by the GA and APSO. Numerical results show that the fitness value and convergence speed by APSO is better than those by GA. The results also show that for multi-objective problem APSO compared to GA can reduce the BER substantially. Moreover, APSO can get better results for both line-of-sight and non line-of-sight cases. 相似文献
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A new decorrelating arrangement for asynchronous up-link direct sequence code division multiple access communication, which employs coherent detection with pilot symbol aided channel estimation, is proposed. The proposed coherent scheme improves the bit error rate (BER) and exhibits no error floor compared to the previous noncoherent schemes. The BER performance for BPSK is obtained by simulations over a frequency-nonselective Rayleigh fading channel 相似文献