الفهرس 
Chapter 1 IntroductionOnly 14 pages are availabe for public view
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Abstract
The expanding need for wide bandwidth is a current and significant concern for all future communications. One use that requires constant, secure connectivity for data transfer is military communications. Due to its capacity to communicate at a high data rate, the Free Space Optical (FSO) communication technology presents an alluring solution to the existing issue.
FSO is an extremely secure kind of communication because it employs laser technology, which communicates at a wavelength that is invisible to the human eye and hence difficult to detect and intercept. Its advantages are limited by the fact that it is a line-of-sight com- munication technology and is well known to be significantly influenced by air attenuation, especially in the presence of channel turbulence.
Using analytic and simulation techniques, we provide a thorough analysis of the serial and cooperative relays for downlink relays and uplink orbital optical satellite communica- tion in this thesis. We then compare our findings to those of the direct link. In order to derive the new closed form for two crucial performance indicators, Bit Error Rate (BER) and Outage Probability (OP), we considered an aggregate channel model consisting of two hops between orbital links with only geometric and pointing error loss in the first downlink hop and assumed a second downlink hop with atmospheric turbulence and atmospheric attenuation.
In order to reduce OP and BER, the thesis contributions focused on the physical layer performance of end-to-end cooperative relays with the best relay selection, best channel characteristics, and best number of relays. The optimum design was then employed to reduce the necessary receiver aperture radius. Our results show a significant improvement in the proposed system’s performance over a direct link at various system parameters.
The closed-form OP and BER for the new proposed system are obtained using various required channel characteristics. Key design factors for realistic downlinks and uplinks of laser satellite communication (SatCom), including operating wavelengths, OGS height above sea and surface level, atmospheric turbulence parameters, and average aperture ra- dius, have been determined using analysis and modeling techniques.
The analytical and simulation approaches include a detailed comparison of the results with some of the prior literature while taking into account various factors impacting the system’s performance.
Three new linkage models have been proposed to connect GEO satellites with OGS through LEO satellites with downlink and uplink optical satellite communication using different main system parameters.
We developed a novel closed form for the two most widely used optical indicators, presented an optical satellite cooperative relay, and contrasted the output of our model with that of an end-to-end direct link. Our findings show that the cooperative model typically outperforms other system topologies.
The operating wavelength, zenith angle, OGS height, distance, and turbulent channel of the system all play a role in this thesis. If we produce a better system design in accordance
with the parameters, the best relay selection often offers higher system performance.
A Monte Carlo (MC) simulation is used to confirm the veracity of these analytical model results, and it demonstrates a decent level of agreement. As the system’s OP and BER performance increased, we had to decide between a key design principle available at various relay counts (1, 2, 3, 4).
A thorough investigation of uplink optical satellite relay communication is conducted, and the resulting data is compared to that of traditional direct links, downlink cooperative relays, and downlink serial relays at various system parameters. In terms of the outage probability and bit error rate, we examined the uplink relay model in the case of different frequencies and the number of relays over the necessary aperture radius.
The findings indicate that the number of relays has a major impact on system perfor- mance; however, in order to optimize optical satellite cooperative relay performance, it is still necessary to choose the channel turbulence, OGS height, operational wavelength, and an appropriate number of relays.