卫星移动通信信道模型和误码率特性分析

在对卫星移动信道传输特性统计模型研究分类的基础上，给出了适合卫星移动信道的部分阴影扩展模型。用试验和修正的方法给出了模型参数，得到的模型适用于非静止轨道变仰角信道，分析了非静止轨道卫星通信系统窄带调制和宽带扩频调制的误码率性能，得到了有意义的结论。     

移动卫星通信信道研究

分析了移动卫星通信信道的传输特征，建立并计算机模拟了移动卫星信道的统计模型，并在此基础上，建立了理想的Ｋ用户直接扩频码分多址（ＤＳ－ＣＤＭＡ）收发系统，研究其下行链路的误码性能。     

阴影环境下陆地移动卫星信道的模型研究

陆地移动卫星信道通常用全阴影模型和部分阴影模型进行分析。本文利用全阴影模型的研究结论,就实际陆地移动卫星信道部分阴影模型的仿真问题,拟合了模型参数与卫星仰角之间的关系。通过统计特性的数值计算,验证了部分阴影模型与全阴影模型的一致性。     

移动卫星通信信道的系统仿真

本文对移动卫星通信的三种典型信道模型进行了完整的系统仿真，得出ＱＰＳＫ调制信号经过不同信道后的误比特率曲线，包括上／下行链路两次衰落的情况。经分析比较发现，信道的性能主要取决于信道参数，各种因素的影响可以归结到对这些参数的影响，而在非静止轨道移动卫星通信中，仰角是影响系统误码性能的重要因素。     

大容量FDM-FM信号干扰数字卫星系统的计算机模拟

本文用计算机模拟的方法研究高速QPSK数字卫星系统受大容量FDM-FM信号同波道干扰时的系统误码特性。根据卫星信号的窄带传输特点,建立并在计算机上实现了卫星QPSK调制解调系统、卫星行波管的非线性特性、大容量FDM-FM干扰信号以及噪声的基带等效模型。构成了适合于研究干扰和噪声条件下高速QPSK数字卫星系统误码特性的计算机模拟系统。利用此等效系统对不同信扰比和不同信噪比条件下卫星高速QPSK信号的传输误码进行了模拟,得到了上行和下行大容量FDM-FM信号干扰时的误码特性曲线,并对模拟结果进行了讨论。     

区域导航对流层延迟误差修正模型研究

本文研究了电波大气折射理论，分析了传播误差因素，阐述了区域导航信号的传播路径与 GNSS 卫星导航的不同，论述了对流层延迟对区域导航信号测量精度的影响，设计了满足区域导航系统应用需求的对流层延迟误差修正模型，并通过仿真研究，验证了所设计区域导航对流层延迟误差修正模型的可行性，并给出了该模型在远距离低仰角和近距离高仰角下的误差修正能力。     

无线紫外光MIMO直升机助降ALOS链路性能分析

无线紫外光通信具有高速率高可靠性的特点,可以满足复杂环境下的通信。通过直升机助降的过程提出近似直视通信方式,并研究了无线紫外光MIMO系统的ALOS通信链路模型,同时计算了弱湍流条件下ALOS链路中MIMO系统的误码性能,并仿真分析其信噪比、发射功率、发射（接收仰角）以及通信距离对误码率的影响。计算分析当发射（接收）仰角小于35时,误码率随着发射（接收）仰角的增大,其增长趋势比较明显,当大于35时,误码率随着发射（接收）仰角的增大,其增长趋势变缓。结果表明,在无线紫外光ALOS链路中,采用天线阵列和多探测器的MIMO技术能够较好地降低误码率和抑制大气湍流,并提高抗衰弱能力。     

差分基准台与GPS用户的卫星仰角和它们间距离的关键研究

该文利用几何关系和空间波传播原理，近似地将地面等效为一平面，在此基础上，讨论了用户在等效平面的投影点和它对卫星的仰角以及卫星的折合高度，分析了在卫星投影点位于用户和基准台的基线上的条件下，卫星投影点沿基准线发生变化时GPS用户和差分基准台对卫星的仰角和它们之间距离的对应关系，并给出具体的数学关系式和算法流程以及计算机仿真曲线图。     

移动卫星通信系统的轨道和覆盖特性分析（下）

移动卫星通信系统的轨道和覆盖特性分析（下）刘彤浩，陈振国３卫星系统的覆盖特性３．１卫星覆盖图卫星覆盖区域是由卫星高度ｈ、最小仰角Ｅ１决定的，如图５所示。假设地球观察点的位置分别用纬度Ｌｅ、经度ｌｅ来表示，星下点的位置分别用纬度Ｌｓ、经度ｌｓ表示；系统...     

相控阵雷达对IKONOS卫星的截获效能分析

从技术上探求了基于STK平台的相控阵雷达截获IKONOS卫星的方法。简要介绍了IKONOS卫星的基本信息及部分参数，并给出了基于STK的相控阵雷达空间目标监视模型，分析了基于STK的相控阵雷达空间目标监视模型搜索屏的仰角与截获IKONOS卫星次数的关系，为有效监视IKONOS卫星提供了重要依据。     

Digital transmission through a land mobile satellite channel

An analytical derivation of the probability of bit error noncoherent frequency-shift keying (FSK) and coherent phase-shift keying (PSK) signals transmitted through a land-mobile satellite channel is described. The channel characteristics used in the analysis are based on a recently developed model which includes the combined effects of fading and shadowing. Analytical expressions for the probability of bit error of FSK and coherent phase-shift keying (CPSK) signals are obtained. The results show that large amounts of signal-to-noise ratio (SNR) are required to compensate for the combined effect of fading and shadowing. An analytical expression for the irreducible probability of bit error of a CPSK signal due to phase variations caused by fading and shadowing is derived. The results described should be useful in the design of land mobile satellite communication systems     

基于马尔可夫过程的卫星移动信道模型及长期预测方法

卫星移动信道可被描述为基于有限状态马尔可夫过程的衰落模型,该文分析了卫星信道的可预测性,然后基于加权预测思想提出了一种卫星移动信道长期预测方法,该方法在当前信道采样的基础上进行二次采样,采样频率大于马尔可夫状态转移速率的2倍,利用信道状态的相关性和信道状态转移概率信息来加权预测未来长期内的信道状态,并依据自回归预测模型给出信道预测输出值,仿真结果表明,采用此方法对卫星信道未来的信道状态进行预测,在信噪比较高时均方误差能够达到10-2量级,在自适应传输过程中可以降低系统平均误比特率,且能够提高系统吞吐量性能,这对卫星移动通信系统的自适应传输和自适应资源分配都具有一定的指导意义。     

The capture effect in multiaccess communications-the Rayleigh andlandmobile satellite channels

The capture phenomenon and its consequences in nonbitsynchronous mobile packet radio networks for binary phase-shift-keying (BPSK) and differential phase-shift-keying modulation are investigated. Exact values of the bit error probability for given signal-to-noise ratios of colliding BPSK signals are derived. Packet error rates, which are needed for analysis of slotted random multiple access methods, are obtained by simulation. Two kinds of mobile radio channels are considered: the Rayleigh fading channel and the land mobile satellite channel. In the latter, because of shadowing, the probability that one of several colliding data packets is correctly received can be on the same order as the probability that a single packet that is not experiencing a collision is correctly received. The influence of Reed-Solomon codes on packet error probabilities is also studied. A slotted ALOHA system using the land mobile satellite channel is analyzed. It is found that with significant shadowing, the overall system throughput may reach the point-to-point throughput. Also, the code rate cannot be optimized in a straightforward manner by assuming one single transmission at a time     

MoM solutions to building blockage of mobile satellite communications

This article presents a full-wave propagation model for arbitrary profile of building blockage in mobile satellite communications, by solving the electric field integral equation for induced surface currents using the method of moments. Asymptotic expressions are used to simplify the integrals. Scattered fields are then found by the radiation equations derived from Maxwell equations. The total received fields around different profiles of buildings are calculated as a function of space, elevation angle and frequency. The results agree well with measurements and other published data. Various useful parameters for designing robust and reliable communication systems like frequency response, average fade duration and coherence bandwidth are found. Performance of mobile satellite system is evaluated in terms of bit error rate of mobile satellite system in frequency non-selective, slowly fading channel.     

Spread-spectrum path diversity in a shadowed Rician fadingland-mobile satellite channel

The effects of two types of path diversity techniques, namely selection diversity and maximal ratio combining, on the bit error probability are investigated for direct-sequence spread-spectrum (DS/SS) transmission in a land mobile satellite channel using coherent binary phase-shift keying (BPSK) modulation. It is assumed that the channel consists of a log-normally shadowed line-of-sight signal plus Rayleigh distributed multipath signals. The bit error probability is evaluated for light, average, and heavy shadowing. The performance is also measured in terms of the outage probability     

A Measurement of the MARISAT L-Band Signals at Low Elevation Angles Onboard Mobil Aero

The MARISAT-to-shipL-band signals used in maritime mobile satellite communications service are degraded by fading and scintillation at low elevation angles. These degradations are attributed to multipath effects arising from ionospheric, tropospheric, and/or sea surface diffractions. To characterize such degradations, measurements were made at the Southbury earth station and onboard the S.S. Mobil Aero while the ship was en route from Norfolk, VA, to Texas City, TX. Measurements include monitoring the carrier-to-noise ratio (C/N) of time-division multiplex/time-division multiple access (TDM/TDMA) voice carriers and measuring the bit error rate (BER) of 2400/1200 bit/s digital data transmissions through a voice channel. Results indicated that bothC/Nand BER are severely degraded at elevation angles below 5° due to propagation anomalies. Information useful for design considerations of future maritime communications systems is summarized.     

阴影移动卫星信道中采用DPD和MRC的PRCPM的检测性能

本文给出了阴影移动卫星信道中采用差分相位检测(DPD)和最大比组合(MRC)的部分响应连续相位调制(PRCPM)信号的检测性能,并给出了实际阴影移动卫星信道中该方案的检测性能数值计算结果.     

Path diversity performance of DS-CDMA systems in a mobile satellitechannel

We derive easy to compute semianalytical expressions for the bit error rate performance of coherent and differentially coherent binary phase-shift keying direct-sequence code-division multiple-access systems operating in a mobile satellite channel. The channel is modeled as frequency nonselective with diversity gain obtained through path diversity. This is the scenario when a signal is transmitted to all satellites in view, and the received replicas are independently demodulated and combined at the receiving side. Our analysis extends previous results to the case of unequal mean powers and Rice factors in the combined signals: a valid assumption if we consider that the satellites are in view with different elevation angles. Furthermore, the effect of independent shadowing on each diversity branch is also considered     

Convolutionally interleaved PSK and DPSK trellis codes forshadowed, fast fading mobile satellite communication channels

Using a model from the literature, the performance of convolutionally interleaved phase-shift-keying (PSK) and differential phase-shift-keying (DPSK) trellis codes for digital speech transmission over shadowed mobile satellite communication channels is determined by computer simulation. First the characteristics of fading channels are examined and analyzed in terms of the probability distributions of amplitude, phase, and burst errors. A statistical method, using a histogram approach, is utilized along with the simulations of fading channels to generate these probability distributions. A test for channel burst error behavior is presented. A periodic convolutional interleaver/deinterleaver to be used with trellis coding to combat slow fading in digital, shadowed mobile satellite channels is designed. This interleaver ha less than half the time delay for the same bit error performance than a block interleaver. The results show that the periodic convolutional interleaver provides considerable improvement in the error and time delay performance of mobile satellite communication channels for up to average shadowing conditions as compared to other techniques