Thesis (MScEng)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: A low earth orbit satellite system can be useful in numerous communication applications
where physical connections are not possible. Communication time available from any point on
earth to the satellite is less than one hour per day. This one hour is fragmented into smaller
time slots due to the satellite orbiting. This is not much time to transfer data and there is
even less time available to transfer data when there are other external factors affecting the
system. It is thus crucial to optimise the satellite communications link so that more data can
be transferred per orbit.
The goal of this thesis is to improve the performance of a low earth orbit satellite communication
channel by varying certain parameters of the system, such as the protocol used,
modulation scheme, packet size, transmission power etc. and then to observe how these
parameters influence the system. The protocols that were chosen to be implemented are
CSMA-CA, CSMA-CA with DSSS technology and Round-Robin Polling.
A simulator for each protocol was designed with the Opnet platform, so that specific parameters
could be changed and the results observed, in order to optimise the communications link
between the satellite and ground stations.
The results showed that there is no particular configuration of modulation scheme, packet
size, transmission power etc. presenting the best overall solution for LEO satellite communications.
It must be considered what the specific LEO satellite application would be used for and
the characteristics required by that specific application. A suitable configuration must subsequently
be chosen from the set of configurations available to satisfy most of the application
requirements. / AFRIKAANSE OPSOMMING: ’n Satelliet met ’n lae wentelbaan kan gebruik word in verskeie kommunikasie toepassings
waar fisiese verbindinge nie noodwendig moontlik is nie. Die kommunikasietyd van enige
punt van aarde af na die satelliet, is minder as een uur per dag. Hierdie tyd word nog verder
verklein omdat die satelliet besig is om, om die aarde te wentel. ’n Uur is glad nie baie tyd
om data oor te dra nie en in realiteit is daar nog minder tyd beskikbaar as daar eksterne
faktore op die sisteem inwerk. Dus is dit baie belangrik om die satelliet kommunikasiekanaal
te optimiseer sodat soveel moontlik data as moontlik oorgedra kan word per omwenteling.
Die doel van hierdie tesis is om die deurset van die kommunikasiekanaal van n lae wentelbaan
satelliet te optimiseer, deur verskeie parameters te verander soos, protokol wat gebruik word,
modulasie skema, pakkie grootte, transmissiekrag ens. en dan waar te neem hoe dit die
sisteem beïnvloed. Die protokolle wat geïmplementeer is, is CSMA-CA, CSMA-CA met DSSS
tegnologie en Round-Robin Polling.
’n Simulator vir elke protokol was ontwerp in die Opnet simulasie platform, sodat die spesifieke
parameters verander kon word om die resultate te bestudeer met die doel om die kommunikasiekanaal
tussen die satelliet en grond stasies optimaal te benut.
Die resultate het bewys dat daar geen spesifieke konfigurasie van modulasie skema, pakkie
grootte, transmissiekrag ens. is wat die algehele beste oplossing is nie. Die spesifieke applikasie
waarvoor die lae wentelbaan satelliet gaan gebruik word moet geanaliseer word sowel
as die spesifieke karakteristieke van daai applikasie. Daarvolgens moet n unieke konfigurasie
opgestel word wat meeste van die applikasie se behoeftes bevredig.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/71930 |
| Date | 12 1900 |
| Creators | Bezuidenhout, Quintus |
| Contributors | Wolhuter, R., Stellenbosch University. Faculty of Engineering. Dept. of Electrical and Electronic Engineering. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 104 p. : ill. |
| Rights | Stellenbosch University |
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