## 4 Discussion
The implementation of LDPC coding results in a more stable connection and improved link budget performance, leading to a 6.5 dB coding gain. The Reed-Solomon code offers a 4.7 dB coding gain, ensuring reliable transmission over long distances. The approach based on Golay code demonstrates an improvement of 2.9 dB, reinforcing their advantage in maintaining link stability. The results confirm that error correction codes significantly enhance the link margin by reducing required Eb/No values for a given BER. This paper provides a detailed analysis of the sensitivity of the link budget to the modulation scheme for a series of representative satellite communication scenarios. However, the results obtained are not strictly limited to these configurations but can be extended and adapted for other types of satellite networks, including dynamic constellations and hybrid networks integrated with terrestrial infrastructure. Although the specific values of the link performance may vary depending on the technical parameters used, the fundamental principles highlighted in this work, such as the importance of choosing an appropriate modulation scheme for each type of link, remain applicable in a wide range of satellite communication scenarios. To validate the results obtained, we made a comparison with the existing literature. Obviously, an exact comparison is not possible because we did not identify an analysis identical to the one in our work from the perspective of scenarios or coding techniques. In [30] the authors implemented a link budget analysis for a LEO nano-satellite. In the analysis, they compared 3 types of modulations and did not consider an error correction code. The results obtained showed that BPSK and MSK modulation have identical results and are the most suitable to ensure a high link margin. The modulation order is low, which implies limitations in the amount of information transmitted, but for the specific application implemented, it seemed sufficient. The results shown in [31] show that for a classic geostationary connection based on the DVB-S2 standard, QPSK is the most robust one and can be selected in case of bad channel conditions and 16 APSK modulation for better channel conditions. In [32] it is shown that for S-band GEO mobile satellite communication systems, QPSK modulation together with Turbo code ensures a relevant link budget for a 12.2 kbps VoIP link in LTE-based technology, but there is no comparison with another analysis scenario. In [33], the author studied link budgets to support communications between LEO CubeSats and ground stations as well as inter-satellite LEO communications. For BPSK and QPSK modulation in combination with an error correction mechanism (code type not specified), the author was able to obtain a positive margin for the scenarios studied, sufficient for the proposed applications. Unlike previous experiments, this work provides an analytical framework that can be used for the design of future multi-orbit satellite systems, taking into account the link performance for high modulation orders and various types of correction codes. A summary of the previously described notions is shown in Table 14.  
As the limitations of the current study, the model assumes a propagation environment based on typical parameters, where the analysis focused on point-to-point links, without examining the effect of interference from frequency reuse scenarios in dense satellite constellations. Integrating interference models and studying their impact on modulations would be an important step towards optimizing next-generation satellite communications.