摘要:

A satellite ground segment which is capable of supporting a uni-directional paging service for land mobile users is described. The system is configured around existing satellites and the VHF wide-area paging network. A suitable transmission format is proposed which employs multi-level frequency shift keying, dual time diversity and Reed-Solomon forward error correction. The anticipated performance of the transmission format is discussed. Proposed implementations of the mobile paging receiver and transmitter data-formatting modulation equipment are presented.

DOI:10.1049/jiere.1988.0018

出版商:IERE    

年代:1988

数据来源: IET

摘要:

This paper presents a selective overview of a study into On-Board Processing (OBP) techniques applied to telecommunications satellites. It describes a representative set of business system mission requirements which are used to define the principle functions needed within the OBP payload. The functions relating to translating up link frequency division channels to time division and baseband switching are investigated. Use of simulation and simple breadboarding has supplemented initial theoretical trade-offs. A specification for a prototype demonstrator incorporating the selected designs is outlined.

DOI:10.1049/jiere.1988.0019

出版商:IERE    

年代:1988

数据来源: IET

摘要:

The current environment of satellite communications and the opportunities for new satellite based services are described. Data distribution is one such service which can be offered on a flexible basis with call-by-call and demand assignment. The paper outlines the main features of a data distribution system known as Pandata, which combines the use of spread spectrum modulation with a multiplex and calling unit.

DOI:10.1049/jiere.1988.0020

出版商:IERE    

年代:1988

数据来源: IET

摘要:

The techniques employed in the design of a high performance, phase-shift-keyed data modem for satellite communications and the results obtained in trials carried out on a prototype modem over a satellite link are described. Digital signal processing techniques enable a high performance modem to be designed, which is capable of operation close to the theoretical limit. The use of custom designed integrated circuits in the production equipment allows the performance to be achieved without cost penalty relative to currently available products. The digital implementation also offers the user the flexibility of full IEEE 488 or RS232 remote control of all important functions, including CCITT data rates from 32 kbit/s to 4.096 Mbit/s and an intermediate frequency from 52 MHz to 88 MHz.

DOI:10.1049/jiere.1988.0021

出版商:IERE    

年代:1988

数据来源: IET

摘要:

It is attractive to be able to alter the coding rate, and hence the error correcting power, of a forward error correcting coder/decoder (codec) to provide a codec whose error correction capability can be matched to the requirements of the data communication system in which it is used.Punctured coding applied to convolutional encoding/Viterbi decoding offers a method of achieving this. Intelsat have specified punctured coding to provide flexibility in selecting either 1/2 or 3/4 rate coding in their Open Network Intermediate Data Rate system. This paper discusses the modification of a proprietary constraint length 7, 1/2-rate codec to operate with punctured coding at rates up to 7/8.Following a brief discussion of the requirements for variable rate coding in communication systems the practical implementation of a prototype codec and considerations relating to performance characterization are discussed.Experimental results at coding rates of 1/2, 2/3, 3/4, and 7/8 are given, together with simulation of performance at 15/16 coding rate to demonstrate the sensitivity of performance to path history length at higher coding rates. It is concluded that the method is very suitable to provide variable coding rates between 1/2 and 7/8 but suffers from increasingly severe practical disadvantages at coding rates above 7/8.

DOI:10.1049/jiere.1988.0022

出版商:IERE    

年代:1988

数据来源: IET

摘要:

The performance of a satellite communications link is largely defined by the modulation and forward error correction coding scheme used. The ultimate performance is defined by the theoretical Shannon capacity but practical schemes currently fall far short of this limit. To aid the search for improved modulation techniques, a test facility has been developed which will allow potentially advantageous schemes to be evaluated via a satellite link, without the need to develop dedicated modem hardware. The facility has been constructed using a virtual memory computer which handles the generation and capture of analogue waveforms in real time. The generalized design allows the transfer function of a satellite channel with a bandwidth up to 200 kHz to be assessed and so provides for the testing of an arbitrary waveform modulation scheme within this bandwidth limit.

DOI:10.1049/jiere.1988.0023

出版商:IERE    

年代:1988

数据来源: IET

摘要:

The paper describes the 5.6 metre Ku-band earth station installed at RSRE Defford to support the British National Space Centre (BNSC) sponsored programme for the evaluation of satellite communication equipment and the demonstration of new satellite service concepts. Details are given of the facilities provided and the physical layout of the earth station, together with some discussion of the essential design parameters.

DOI:10.1049/jiere.1988.0024

出版商:IERE    

年代:1988

数据来源: IET

摘要:

Frequency congestion in the established C-band (6/4 GHz) and Ku-band (14/11 GHz) used for fixed service satellite communications (satcom) will eventually impose a move to the Ka-band (30/20 GHz) space allocation. Japan is already providing internal Ka-band satcom services via its nationalCS-2spacecraft which was launched in 1983.CS-2is the first of a number of national and international satellites carrying Ka-band payloads which are promised in the next five years to provide both fixed telecommunication services and inter-satellite relays. Europe's first experimental venture into this new band will be starting in 1989 with the launch of the European Space Agency's (ESA)Olympussatellite.This paper describes a national project aimed at securing for the UK a share of this future space market. This is the development by Marconi of an advanced 30/20 GHz space craft transponder for the Royal Signals and Radar Establishment (RSRE) at Defford as part of a programme sponsored by the British National Space Centre (BNSC). This experimental transponder will provide the UK springboard for the development and testing of the many novel features of tomorrow's communications satellite payloads.

DOI:10.1049/jiere.1988.0025

出版商:IERE    

年代:1988

数据来源: IET