Projects:2014S1-13 S-band Communication for Small Satellite
Contents
Project Summary
Design an S-band communications board intended for operations on board a 3U CubeSat.
Team
Group Members
- Aaron Hardman
- Daniel Dac Vien
Project Supervisors
- Dr Braden Phillips
- Dr Behnam Jamali
Motivation
Project Status
At this stage the project is behind our planned schedule. We had initially planned to have a completed software simulation of the system and hardware components defined by now. Currently we have a simulation of our system in GNURadio but there are errors present in this. These errors are related to the testing of the BER of the signal. We have tried to run offline evaluations of the BER but when the test files became to large, ie in the realm of MB's, we needed to use GNURadio's live BER calculator. Unfortunately this brough about another error. When we attempted to compare the two bit streams created in GNURadio we encountered synchronisation errors with these two streams, even if we are one bit out the entire simulation will be wrong. We have not as of yet been able to resolve this issue with the simulation and we believe we will need to create our own GNURadio module to deal with the unsynchronised bit streams.
We have been able to develop numerous test environments for the project. These test environments use GNURadio and we have begun a Matlab simulation as well, however this Matlab simulation is in an early stage still and requires significant work. The GNURadio test environments include the one displayed below which is capable of testing GMSK, DQPSK and FSK modulaiton techniques and the effect that fading and noise will have on the system. We have also been able to set up a test environment with hardware that allows students to send digitally modulated and FM data from one GNURadio computer to another. They are capable of encoding, sending and then decoding this data.
With respect to hardware we have also not completely met the initial goals we had set ourselves out. Initially we planned to have selected hardware to be used in the transceiver. Instead we have been able to produce a definitive listing of potential hardware to be used and what hardware cannot be used. In addition to this we have also been able to produce an in depth listing of the current hardware that is employed in cubesats and the reasoning behind the choices that have been made.
Preliminary Findings
At this stage we have no definitive data to suggest a modulation technique that can be used. We have only been able to narrow it down to 3 potential schemes, GMSK DQPSK and FSK. Instead we have been able to setup multiple test environments that only contain one small error that when fixed will ensure proper testing can be completed. From the small bit stream tests we performed DQPSK was the best performing modulation technique, however the bit streams were too small to make this finding valid.
GNURadio Simulation System
Below is a picture of the system we created in GNURadio to simulate the channel affects on our signal.
