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An investigation of an algorithm for error detection and correction in transceivers for nanosatellites
Author(s)
Sivate, Themba
Date Issued
2024
Type
Thesis
Publisher
Cape Peninsula University of Technology
Abstract
One of the biggest problems faced by many organizations in the space science industry is the
inability to determine the accuracy of the data received from satellites. A satellite collects data
from a point of interest, store the data on the onboard storage, then transmits it to the ground
when the ground station is visible. The problem arises when the satellite loose connection to
the ground station while it was transmitting data, resulting in corrupt and unusable data. The
purpose of this study is to identify a possible solution to this problem by investigating and
developing an algorithm that can be used to determine the accuracy of the data received from
the satellite and provide an 8-bit error correction. This study focuses on Very High Frequency
(VHF) and Ultra High Frequency (UHF) Transceivers which are used for light weigh data
transfer between a nanosatellite and a ground station. Since the transceiver normally transfers
data at a rate of 9600bps (depending on the application), we can easily simulate such data
transfer using a universal asynchronous receiver-transmitter (UART) based transceiver such
as nRF24L01+ with a baud rate of 9600bps. In the nanosatellite industry, little to no research
about error detection and correction, especially for VHF/UHF Transceivers.
The proposed solution uses an ASCII table as a base for signing and validating data
exchanged wirelessly between the nanosatellites and the ground stations. The error detection
is archived by computing both the number of characters and the sum of the characters as the
corresponding decimal value of each character is found in the ASCII table. Both variables are
then set as a header separated by a pipe (vertical bar) into the actual payload sent by satellite
to the ground station. Once the data arrives at the ground station, we recompute to check the
payload’s accuracy and the possibility of data recovery if any was lost. Data recovery is
archived by computing the difference between the sum from the header and the sum computed
on arrival, and by comparing the number of characters from both ends. When 8 bits (single
character) of data is lost, such data is recovered from the ASCII table using the difference
computed. This method was chosen because any programming language understands the
ASCII standard and can be implemented at both application and firmware level, which is crucial
for bare metal implementation as it supports power efficiency.
The experimental results show that the proposed algorithm always detects invalid payloads.
Furthermore, the experimental results show that the data recovery rate is 100% when the data
loss is a single byte (8 bits). An increased payload size was also noticed due to the appended
header, which then increased the time it takes for data to be transferred from the satellite to
the ground station. A response command was also sent indicating the data integrity status of
the payload received, allowing the satellite to delete such payload as the onboard storage is
limited.
inability to determine the accuracy of the data received from satellites. A satellite collects data
from a point of interest, store the data on the onboard storage, then transmits it to the ground
when the ground station is visible. The problem arises when the satellite loose connection to
the ground station while it was transmitting data, resulting in corrupt and unusable data. The
purpose of this study is to identify a possible solution to this problem by investigating and
developing an algorithm that can be used to determine the accuracy of the data received from
the satellite and provide an 8-bit error correction. This study focuses on Very High Frequency
(VHF) and Ultra High Frequency (UHF) Transceivers which are used for light weigh data
transfer between a nanosatellite and a ground station. Since the transceiver normally transfers
data at a rate of 9600bps (depending on the application), we can easily simulate such data
transfer using a universal asynchronous receiver-transmitter (UART) based transceiver such
as nRF24L01+ with a baud rate of 9600bps. In the nanosatellite industry, little to no research
about error detection and correction, especially for VHF/UHF Transceivers.
The proposed solution uses an ASCII table as a base for signing and validating data
exchanged wirelessly between the nanosatellites and the ground stations. The error detection
is archived by computing both the number of characters and the sum of the characters as the
corresponding decimal value of each character is found in the ASCII table. Both variables are
then set as a header separated by a pipe (vertical bar) into the actual payload sent by satellite
to the ground station. Once the data arrives at the ground station, we recompute to check the
payload’s accuracy and the possibility of data recovery if any was lost. Data recovery is
archived by computing the difference between the sum from the header and the sum computed
on arrival, and by comparing the number of characters from both ends. When 8 bits (single
character) of data is lost, such data is recovered from the ASCII table using the difference
computed. This method was chosen because any programming language understands the
ASCII standard and can be implemented at both application and firmware level, which is crucial
for bare metal implementation as it supports power efficiency.
The experimental results show that the proposed algorithm always detects invalid payloads.
Furthermore, the experimental results show that the data recovery rate is 100% when the data
loss is a single byte (8 bits). An increased payload size was also noticed due to the appended
header, which then increased the time it takes for data to be transferred from the satellite to
the ground station. A response command was also sent indicating the data integrity status of
the payload received, allowing the satellite to delete such payload as the onboard storage is
limited.
Additional information
Thesis (MEng (Satellite Systems and Applications))--Cape Peninsula University of Technology, 2024
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