Design of Software-Defined Radio-Based Adaptable Packet Communication System for Small Satellites

Yasir M O Abbas,Kenichi Asami

doi:10.3390/aerospace8060159

Abstract

Software-defined radio (SDR) devices have made a massive contribution to communication systems by reducing the cost and development time for radio frequency (RF) designs. SDRs opened the gate to programmers and enabled them to increase the capabilities of these easily manipulated systems. The next step is to upgrade the reconfigurability into adaptability, which is the focus of this paper. This research contributes to improving SDR-based systems by designing an adaptable packet communication transmitter and receiver that can utilize the communication window of CubeSats and small satellites. According to the feedback from the receiver, the transmitter modifies the characteristics of the signal. Theoretically, the system can adopt many modes, but for simplicity and to prove the concept, here, the changes are limited to three data rates of the Gaussian minimum shift keying (GMSK) modulation scheme, i.e., 2400 bps GMSK, 4800 bps GMSK and 9600 bps GMSK, which are the most popular in amateur small satellites. The system program was developed using GNU Radio Companion (GRC) software and Python scripts. With the help of GRC software, the design was simulated and its behavior in simulated conditions observed. The transmitter packetizes the data into AX.25 packets and transmits them in patches. Between these patches, it sends signaling packets. The patch size is preselected. Alternatively, the receiver extracts the data and saves it in a dedicated file. It directly replies with a feedback message whenever it gets the signaling packets. Based on the content of the feedback message, the characteristics of the transmitted signal are altered. The packet rate and the actual useful data rate are measured and compared with the selected data rate, and the packet success rate of the system operating at a fixed data rate is also measured while simulating channel noise to achieve the desired Signal-to-Noise Ratio (SNR).

Highlights

Software-defined radio (SDR) is a flexible technology that enables the design of an adaptive communications system
Eutelsat Quantum will be the first generation of universal satellites able to serve any region of the world and adjust to new business without the need to procure and launch an entirely new satellite
Data inputs and outputs are handled by the user datagram protocol (UTP) and transmission control protocol (TCP) network protocols

Summary

Introduction

Software-defined radio (SDR) is a flexible technology that enables the design of an adaptive communications system. A generic hardware design can be used to address various communication needs, with varying frequencies, modulation schemes and data rates [1]. The radio implementation process includes setting the filtering parameters, such as the pass and stop band frequencies, as well as digital quadrature transformations and data rate adjustments using up and down sampling processes. Recent improvements in analogue to digital converter technology have led to the development of software-defined radios with digital receivers [2]. Eutelsat Quantum will be the first generation of universal satellites able to serve any region of the world and adjust to new business without the need to procure and launch an entirely new satellite. Amateur operators have built many SDR-based ground stations; station enters the beam width of the satell

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