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The space-time line code (STLC), which has been recently proposed in the literature, assumes fully known channel state information at the transmitter and not the receiver. However, the effective channel gain is still required at the receiver to coherently detect M-ary quadrature amplitude modulation (MQAM) symbols. In this paper, we propose pilot-aided STLC systems, which do not require the effective channel gain at the receiver to detect the MQAM symbols. In order to further improve the error performance of the proposed schemes, we present the pilot-aided STLC systems with transmit antenna selection (TAS). Using a more direct and simpler approach, we derive the average symbol error probability (ASEP) of the coherent 1 Â 2 STLC systems with TAS, which represents the lower bound of the pilot-aided 1 Â 2 STLC systems with TAS. For comparison, in a similar manner, we also derive the ASEP of the coherent 2 Â 2 STLC systems without TAS, which represents the lower bound of the pilot-aided 2 Â 2 STLC systems. For pilot-aided 1 Â 2 STLC systems with TAS, the gap between the simulated symbol error rate (SER) and the derived theoretical ASEP lower bound is very small. For a given number of transmit antennas, the simulated SER and theoretical ASEP also show that the error performance of the pilot-aided 2 Â 2 STLC systems with or without TAS is superior to the pilot-aided 1 Â 2 STLC systems with TAS by at least 1.8 dB.

This research will analyze the tradeoffs between coverage optimization based on Position dilution of precision (PDOP) and cost of the launch vehicle. It adopts MATLAB and STK tools along with multiple objective genetic algorithms (MOGA) to explore the trade space for the constellation designs at different orbital altitudes. The objective of optimal design solutions is inferred to determine the economic and efficient LEO, MEO, HEO or hybrid constellations and simulation results are presented to optimize the design of satellite constellations. The benefits of this research are the optimization of satellite constellation design, which reduces costs and increases regional and global coverage with the least number of satellites. The result of this project is the optimization of the number of constellation satellites in several orbital planes in LEO orbit. Validations are based on reviewing the results of several simulations. The results of graphs and tables are presented in the last two sections and are taken from the results of several simulations.

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