FPGA based transmitter design using adaptive coding and modulation for low earth orbit satellite communications

In this thesis, a field-programmable gate array (FPGA) based design of high rate transmitter using adaptive coding and modulation for low earth orbit satellite communications is implemented. The communication channel varies due to orbital movements of low earth orbit satellites and the rotation of the earth around its own axis. To provide efficient and uninterrupted communication in this varying environment, a transmitter structure employing adaptive coding and modulation has been designed. The developed transmitter structure with adaptive coding and modulation is modelled in MATLAB. Then, the digital design of the developed structure is done based on the MATLAB model. This design is verified with reference MATLAB design in behavioral simulations. After behavioral simulations are done, the design is implemented on an FPGA. The FPGA implementation is done on Xilinx Kintex Ultrascale xcku060 FPGA because it provides high performance, and its space grade model will be on product line by the end of 2020. The coding rates achieved, and the spectral efficiency results are obtained for the designed transmitter structure employing adaptive modulation and coding. It is observed that its spectral efficiency is 7,068 at the highest speed it can operate. Timing analysis of the design was also made as a result of the hardware implementation. With the timing analysis, the highest system clock signal frequency that it can operate on has been determined. The data rates of the system are derived by using the clock signal frequencies. It is observed that the new transmitter structure implemented on xcku060 FPGA can reach an output rate of 75 Megasymbols per second (Msps) and output sample rate of 300 Megasamples per second (MSps). It supports input speeds varying between 50.7225 and 530.1 Megabits per second (Mbps) according to the design's operating mode.