Dual-Space Diversity over Land Mobile Satellite Channels Operating in the L and K Frequency Bands

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.     

On the Design of Downlinks for Satellite Commuication Systems Using TFM and Convolutional Codes: A Simulation Approach with TOPSIM III

The performance of a TFM scheme applied to a satellite downlink with an on-board regenerative repeater is evaluated by using a time domain simulation software package TOPSIM III. The TFM bit error rate in the presence of nonlinearities and adjacent channel interference is evaluated by means of semianalytic methods. The capabilities of convolutional codes for reducing the overall channel bit error rate are also investigated. Design guidelines are finally outlined for advanced satellite communication systems in which the joint use of nonconventional modulation schemes (like TFM) and of convolutional codes results in improved performance with respect to both bandwidth exploitation and system flexibility.     

An Effective Error Control Scheme for Satellite Communications

The conventional go-back-NARQ is inadequate for error control on satellite channels due to the large round-trip delay and high bit rate. The throughput efficiency of this system drops rapidly as the channel error rate increases. In this paper, a variation of the go-back-NARQ is described. This variation reduces the effect of the round-trip delay, and hence increases the system throughput efficiency. Therefore, it may find applications m satellite communication systems or other systems where round-trip delay is large.     

An Integrated Design Approach to 30/20 GHz Trunking Systems

A design procedure for 30/20 GHz trunking systems is presented which permits the joint optimization of the satellite links and the terrestrial links between diversity terminals of individual earth stations. This process involves the generation of uplink and downlink power control functions (PCF's), which depend on 1) the rapidity with which power control can be exercised, relative to the rate of variation of atmospheric attenuation, and 2) the available uplink and downlink HPA power. The PCF's combine to produce a link availability curve (LAC), which describes the uplink/downlink fade combinations for which a specified bit error rate (BER) can be maintained. The set of required terminal separation distances (TSD's) can generally be computed from the LAC, together with the marginal uplink and downlink attenuation distributions. Methods of implementing uplink and downlink power control are discussed. In particular, several alternatives for determination of uplink attenuation and selection of the appropriate transmit terminal are contrasted.     

Estimation of the error performance objectives for satellite communication systems

We consider the physical layer error performance parameters and design criteria for digital satellite systems established by ITU‐R Recommendation S.1062, where the performance objectives are given in terms of the bit error rate (BER) divided by the average number of errors within a cluster. It is well known that errors on satellite links employing forward error correction (FEC) schemes tend to occur in clusters. The resulting block error rate is the same as if it was caused by randomly occurring bit errors with an error‐event ratio of BER/α, where α is the average number of errors within a cluster. The factor, α, accounts for the burstiness of the errors and also represents the ratio between the BER and the error‐event ratio. This paper proposes theoretical methods to estimate the factor, α. Using the weight distributions of the FEC codes, we derive a set of expressions for the factor, α, as well as their compact lower bounds. We present lower bounds for various FEC schemes including binary BCH codes, block turbo codes, convolutional codes, and turbo codes. The simulation results show that the proposed lower bounds are good estimates in the high signal‐to‐noise ratio region. Copyright © 2008 John Wiley & Sons, Ltd.     

Quality estimation of PSK modulated signals

The use of the Ka band (30/20 GHz) for satellite communication systems raises the problem of dealing with rain attenuation. A very important problem in fade countermeasure systems is the need to detect signal quality quickly and accurately. In fact, the countermeasure has to be initiated before the signal degradation effect an the bit error rate is detected by the user. This article presents an overview of different methods to evaluate signal quality, which are based on the availability of soft quantized levels of PSK demodulated signals at the receiver. It is shown that this class of methods has a good theoretical performance. Also, an innovative procedure is presented which adapts one of the methods to some existing hardware, and tunes up a set of parameters in order to compensate for the fact that the hardware is to same extent impaired     

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     

Measurement and Modeling of Amplitude Scintillations on Low-Elevation Earth-Space Paths and Impact on Communication Systems

Amplitude scintillations occurring on low-elevation earthspace paths can be large enough to significantly degrade the quality of satellite communications links atX-band and higher frequencies. This paper presents measurements of amplitude scintillations on low-elevation (7.1° and 8.9°) satellite downlinks atX-band. The statistical distributions of scintillation amplitude and rms intensity are approximated using the Moulsley-Vilar model [1]. An analytical approximation of this model is presented and is shown to be an easy means of predicting system outage time due to scintillations. Theoretical estimates of the average bit error rate for a digital satellite link subject to scintillation fading are presented for NCFSK and CPSK modulations. Other ways in which scintillations can affect a satellite communication link are discussed, and results are also presented showing the seasonal and diurnal variability of the scintillation intensity and long-term correlation with ground temperature.     

Performance of PSK signal transmitted over satellite channel

The authors determine the bit error rate of a digital satellite system with phase modulation when at the input of the satellite only Gaussian noise is added, while at the input of the earth station they assume both Gaussian noise and an interference approximated by the sum of n sinusoidal signals     

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     

Bit Error Probability and Bit Outage Rate in Chaos Communication

This paper investigates the notion of the probability of bit error (PBE) and its distribution in chaos-based communication systems; these are seen as being the fundamental quantities to both the well-known bit error rate (BER) and the new concept in chaos communications of bit outage rate (BOR). The form of the distribution illustrates the degree to which bit error rate is a stable representation of performance. Bit outage rate is another measure of performance which gives practically helpful information about bit error. For a simple coherent chaos-shift-keying system the distribution of bit error probability is derived exactly, and theoretically exact formulas for the bit outage rate and bit error rate are presented. Two specific cases are developed to obtain useful qualitative and quantitative information. The cases concern independent Gaussian spreading, as a lower benchmark and logistic map spreading, as typical of effective chaotic spreading. Comparisons are obtained between these spreading distributions and between different extents of their spreading, calibrated against per bit signal to noise ratio. A general conclusion is that bit outage and bit error rates are complementary measures of performance.     

Effect of multiple access interference on performance of multi-beamCDMA-based LEO satellite systems

A practical model is presented for analysing the multiple access interference (MAI) due to all visible interfering users in CDMA-based multispot beam LEO satellite systems. The authors calculate the average bit error rate with perfect power control for different numbers of interfering users. Showing that the amount of MAI has a substantial effect on the system capacity     

非静止轨道移动卫星通信中CDMA误码性能分析

分析了非静止移动卫星通信中ＣＤＭＡ的误码性能。考虑移动卫星的信道模型为有遮蔽的菜斯衰落模型，并将卫星覆盖的最小仰角对误码的影响引入到该模型中，推出了在高斯近似多址干扰下和最大似然二阶分集下，用户数、仰角和码长与误码的关系式，计算了数值曲线并讨论了结果。     

Analysis of Coherent Satellite Communication Systems in the Presence of Interference and Noise

This paper presents the analysis and evaluation of bit error probabilities of coherent MPSK nonlinear satellite communication systems, in which there is uplink noise, downlink noise, and CW tone interference with random phase uniformly distributed over the interval [0, 2π]. The evaluation of bit probabilities also includes intersymbol interference whose statistical distribution is constructed through a two-dimensional moment technique. This moment technique is as effective and accurate as the standard Gauss quadrature formulas (GQF), yet more versatile than GQF for evaluating an expectation over random variables. Some numerical examples for the performance of satellite channels are illustrated.     

卫星相干光通信跟瞄误差对链路性能的影响

以星间相干激光通信链路的接收机相干效率为研究对象,分析了动态跟瞄误差对相干效率的影响,将相干效率引入到星间相干激光通信链路方程,推导了跟瞄误差波前失配条件下的相干光通信链路的误码率概率表达式,对卫星激光通信链路中跟瞄对准误差导致的相干效率下降、链路误码性能劣化情况进行了仿真计算。结果表明,由于跟瞄对准误差波前失配的影响,相干激光通信接收终端具有一个优化的接收孔径,在本仿真条件下,LEO-GEO星间链路动态跟瞄误差为0.5μrad时,优化接收孔径为0.5 m,链路可获得最佳误码性能。     

Impairment of digital transmission through a Ka band satellite channel due to weather conditions

This paper describes an analytical derivation of the performance impairment of a non-coherent FSK signal and a coherent PSK signal due to fading caused by weather conditions at Ka band. Analytical results on the effect of signal phase variation on a coherent PSK signal are included. Numerical values in terms of probability of bit error are given for the two digital signals. These results should be useful to a system designer of satellite communications systems at Ka band. © 1998 John Wiley & Sons, Ltd.     

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.     

Turbo乘积码在卫星ATM系统中的应用

Turbo乘积码(TPC)是一种性能优异的前向纠错编码技术.卫星ATM技术代表了卫星通信网络的研究方向.研究了TPC在卫星ATM系统中的应用方案.首先,分析了卫星信道对ATM信元传输带来的影响;然后对TPC的编、解码的方法进行了简要介绍,并阐述了TPC的优越性能;最后,提出了一种卫星ATM网络中应用TPC的解决方案,并通过仿真得到了该方案的性能曲线.仿真结果证明,TPC的应用能够大幅降低卫星信道的误码率,使ATM信元能够正确传输.     

Effects of pointing errors and channel fading on the performance of free‐space optically‐preamplified PPM systems

In this paper, we study the impact of pointing errors and channel fading on the performance of free‐space, optically preamplified, M ‐ary PPM systems. We consider two types of free‐space optical links: (i) inter‐satellite links and (ii) inter‐building links. For inter‐satellite links, only pointing error is considered. Starting with a Rayleigh model for the pointing error angle, we derive analytically the PDF for the pointing error parameter and for the signal‐to‐noise ratio (SNR) per bit. For inter‐building links, we derive the density function for the SNR per bit that includes the combined effects of pointing errors and channel fading, assuming Rayleigh‐distributed pointing errors. The channel fading models considered in this study for inter‐buildings links are the log‐normal and gamma–gamma models. We provide the error probability as a function of the average SNR per bit for both types of links. To cover systems with and without forward error correction, we compute the average SNR per bit required to achieve a bit error rate of 10^?4 and 10^?9. The corresponding power penalties are computed for different symbol sizes, scintillation indexes, and pointing jitters. Copyright © 2016 John Wiley & Sons, Ltd.     

协作通信技术在卫星系统中的应用

针对卫星移动通信信道具有复杂时变衰落的特点,提出了将协作通信技术引入卫星系统,从而达到抗衰落、获取分集增益的目的。具体给出了卫星与用户之间彼此协作的模型,且仿真了卫星相互协作时系统的误码率曲线。仿真结果表明,协作通信会降低系统误码率,并带来显著的性能增益。