COMPLEX CDMA VERSUS FDMA/SCPC FOR LOW AND MEDIUM BIT RATE APPLICATIONS FOR FIXED SATELLITE SERVICES

In this paper, the performance of a DS-CDMA asynchronous satellite communication system, using four-phase sequences with near-optimum correlation properties, is analysed and compared with the result achievable by adopting the FDMA/SCPC approach. The comparison is carried out on the basis of the number of the simultaneous active channels in the network and of spectral efficiency. In addition, a similar CDMA system using four-phase sequences, constructed by means of binary Gold sequences having the same family size, has been analysed, and notable performance differences have been found. In particular, the use of four-phase near-optimal sequences provides an increase of about 50 per cent in the spectral efficiency. This result expands the convenience of using CDMA over a wider set of bit rate values, even for fixed satellite communications. Convolutional coding and Viterbi soft decoding are also included in the system. Simulation results are shown for some values of bit error probabilities of practical interest.     

Design considerations for a larger inmarsat standard ship earth station

A new standard of INMARSAT ship earth station for multi-channel operation could find particular application on large passenger ships and off-shore oil/gas platforms. This paper provides estimates of platform and ship motions and discusses general design requirements, notably of the antenna system. The discussion includes consideration of possible modulation and multiple access techniques. Single channel per carrier (SCPC) operation is advocated which permits easy integration with the present service to single channel INMARSAT Standard-A ship earth stations. Major parameter/relative cost trade-off curves needed in an overall ship earth station design optimization are presented.     

SCPC卫星通信系统中计算互调噪声功率谱的一种快速方法

本文利用ＳＣＰＣ的特点，提出和推导了ＳＣＰＣ卫星通信系统中互调噪声功率的一种快速计算方法。对于１３００个载波的ＳＣＰＣ系统，在普通的３８６／３３ＰＣ机上，利用此法计算时间仅需１５ｍｉｎ，因此它对ＳＣＰＣ系统设计具有使用价值。     

Digital audio broadcasting: High-grade service quality through on-board processing techniques

A digital audio broadcasting (DAB) satellite system is presented here which provides a high-grade quality of service for some hundreds of channels. This, with minimum cost of the radio set and of the broadcasting station, greatly improves the radio broadcasting service throughout the world, especially in areas where deployment of conventional relay infrastructure is difficult and not yet cost-effective. Potential broadcasters located in the visible hemisphere can directly up-link their programming to the DAB satellites. Broadcasters can also copy each up-link channel and steer flexibility to any beam or combination of satellite beams. The paper illustrates the advantages and the feasibility of a DAB system based on geostationary satellites with on-board processing generating signals of MCPC (multiple channel per carrier) type. This multiplexing technique allows large system margins. This solution allows the satellite L-band TWTA amplifiers to be operated in saturation and eliminates the intermodulation noise associated with the transmission of FDMA channels. A powerful coding scheme has been selected to create a ‘robust’ down-link. In this way several high-power DAB channels of radio programming, with selectable data rate, are directly delivered to the users.     

On-board digital signal processing technologies for present and future SCPC systems

Devices and architectures for on-board SCPC (single channel per carrier) multi-carrier demodulators suitable for use in satellites to be launched between the present and the year 2000 are discussed in the light of trends in the development of device technology towards lower on-board weight and power consumption. It is shown that at the present time (equivalent to about 1990 for on-board use). The choice of demodulation scheme depends on the number of channels available for regeneration on board the satellite. The total weight and power consumption for several suitable on-board multicarrier demodulation schemes are predicted for 1990, 1995 and 2000, as functions of the number of channels to be regenerated.     

卫星数字电视常用的传输方式

卫星数字电视的频带利用方式通常有SCPC和MCPC两种方式,本文介绍了这两种传输方式及其优缺点。     

Ka卫星网络传输探究

由于Ka频段宽带卫星具有高质量、低成本、广覆盖、小终端等优势特点,使其成为宽带卫星发展方向。文章通过分析Ka卫星的优势和我国Ka卫星网络的建设情况,结合广电行业需求,探究Ka卫星网络与广电行业生产的适配。     

Simulation of an on-board hierarchical multistage digital FDM demultiplexer for mobile scpc satellite communications

This paper is focused on the finite-precision time-domain simulation of the hierarchical multistage method detailed in References 1 and 2 for demultiplexing of an FDM signal being composed of L = 32 slot signals. This approach to FDM demultiplexing is based on the processing of complex signals by linear-phase FIR filters, where at any stage of processing the respective signals are always oversampled by a factor of two. The simulation results fully confirm the system performance predicted in Reference 1 by modelling the distortions (spectral foldover and quantization noise) inherent in the system: assuming an ideal FDM signal at the input port of the analogue anti-aliasing bandpass filter in front of the analogue-to-digital converter, a minimum signal-to-distortion ratio (S/D) of 30 dB is achieved at all L output ports of the demultiplexer with {w, w_F, w_i} = {11,12,14}, as anticipated in Reference 1. The signal word length w apply to the A/D conversion, w_F to requantization between the filter stages, and w_i to filter internal signal processing.     

胜利油田卫通网设计中若干问题的分析

VSAT网络在石化领域的应用是目前卫星通信行业一个重要业务增长点,该文结合胜利油田VSAT网络设计中的几个具体问题,探讨了卫星通信在石化行业的组网,重点是频段及通信体制的选择、天线的选型和如何实现带宽的按需分配。     

SCPC／DAMA卫星通信系统中的信道强拆方案探讨

本文提出了ＳＣＰＣ／ＤＡＭＡ卫星通信系统中三种信道强拆的方案，并分析了其特点和应用场合。