## 8 Conclusions  
This paper explored different transparent architectures for 5G NTN based on a mega-constellation. In particular, we studied the time performance offered when the backhaul, the midhaul, and the NR signal are relayed. To this end, we firstly conducted the performance characterization of Starlink, which resulted in a maximum bitrate on UDP of almost 50 Mbps in uplink and 440 Mbps in downlink, as well as a mean RTT of less than 55 ms. Then, we developed a testbed that combined mega-constellation connectivity and open-source software, specifically OAI and Open5 GS, to operate a 5G NTN network. Finally, we carried out a testing phase to measure the RTT and jitter achieved by each of the proposed architectures. The results proved that the backhaul and midhaul architectures achieve similar performance. In midhaul, we disabled a non-standard timer implemented by OAI for the RA procedure, as it expired due to the non-real-time implementation of RFSimulator. The NR architecture obtained the worst performance, since RFSimulator was designed for Ethernet connections. The traffic compression implemented on Starlink demonstrated this. This technological limitation demonstrated that RFSimulator is a straightforward solution that enables UE registration on the network, albeit with limited service performance. From this work, we conclude that transparent architectures provide benefits for certain use cases, such as those primarily focused on backhaul and midhaul. We also validate the usage of mega-constellations in 5G networks, emphasizing their outstanding performance. Nevertheless, the Uu protocol stack involves time-sensitive procedures that pose significant challenges for transparent architectures, so the latency reduction between UE and gNB offered by regenerative architectures may be crucial. So far, we envision the co-existence of both types of architectures, since they address distinct use cases and offer complementary benefits. **Author Contributions:** Conceptualization, O.B., A.C. and J.A.R.-d.-A. ; methodology, O.B., A.C. and J.A.R.-d.-A. ; software, O.B. ; validation, O.B. ; formal analysis, O.B. ; investigation, O.B. ; resources, O.B., A.C. and J.A.R.-d.-A. ; data curation, O.B., A.C. and J.A.R.-d.-A. ; writing--original draft preparation, O.B. ; writing--review and editing, O.B., A.C. and J.A.R.-d.-A. ; visualization, O.B. ; supervision, A.C. and J.A.R.-d.-A. ; project administration, A.C. and J.A.R.-d.-A. ; funding acquisition, A.C. and J.A.R.-d.-A. All authors have read and agreed to the published version of the manuscript. **Funding:** This work is co-funded by the Generalitat de Catalunya and the European Social Fund (Joan Oro Grants to hire research staff in training FI 2023, no. 2023 FI-1 00861); by the Government of Catalonia in the scope of the NewSpace Strategy for Catalonia; by the CDTI and the European Union NextGenerationEU/PRTR (Call \"Ayudas Cervera para Centros Tecnologicos 2023\", the Grant 6G-DIFERENTE, ref. number CER-20231018); by the Spanish Ministry of Economic Affairs and Digital Transformation and the European Union (NextGeneration EU) in the framework of the Recovery Plan, Transformation and Resilience (PRTR) (Call UNICO I+D 5G 2021, ref. number TSI-063000-2021-8-6 SSatNet-SeS); and by the European Union's Horizon Europe under Grant Agreement no. 101096526 (ETHER). It is partially supported by Spanish MCIN / AEI/ 10.13039/501100011033/FEDER/UE through PID2023-146378 NB-I00. **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable.