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Project Overview

The communications system will be a combination of two major components, the on-board computer and the LimeSDR transceiver. These two components will allow complete customization of telecommand and control, all the way down to the digital encoding and modulation techniques. This is one of the major advantages of employing a Software Defined Radio (SDR) system. New modulation techniques can simply be programmed into the board, instead of having to make an entirely new hardware-based board. This will allow us to save time and money experimenting with different communication techniques, while simultaneously allowing us to find the best possible way to communicate with the ground station.

The main component of the communication system will be the onboard computer that is responsible for decoding, encoding, and processing all the digital packets created by the system. The computer will be running a low overhead Linux distribution, most likely ARCH-LINUX, to save on CPU time and overall power consumption. This will allow us to have a BASH shell open and run all the commands to the computer by simply echoing the transmitted packets into the BASH shell, sending the output into a buffer file, and then transmitting that buffer file back to the ground. This system will be a more secure, customizable, and independent version of typical wireless communication protocols such as SSH or VNC since it operates over normally inaccessible HAM bands.

The second major component of the communication system will be the LimeSDR mini, responsible for modulating all digital signals. The LimeSDR is an FPGA equipped with the LMS7002M radio transceiver, capable of achieving full duplex operation. The system is based off the concept of a Multiple Input Multiple Output (MIMO) system, which allows the communication to be transmitting and receiving simultaneously. Capable of operating from 10 MHz to 3.5 GHz, the LimeSDR mini will likely operate on the S-Band (2 – 4 GHz) or L-Band (1-2 GHz) to reduce the effect of atmospheric noise, and allow for higher bandwidth signals, both of which will increase the total data transmission rate of the system.