## 7 Discussion  
The previous results prove the feasibility of 5G NTN with transparent architectures based on mega-constellations. In terms of outcomes, this paper not only experimentally demonstrates the integration of mega-constellations into the 3 GPP sector but also provides time metrics to assess the performance experienced by end users. These findings may encourage the community to continue exploring space solutions based on mega-constellations as transparent payloads, as well as their potential applications. The architectures proposed in this work have various practical advantages and disadvantages. The relay of the backhaul enables the roll-out of reliable and robust terrestrial infrastructure in remote locations, eliminating concerns about wired connections to the 5 GC. However, expenses are considerable, as it requires having the entire RAN deployed in the target area. The relay of the midhaul lowers these costs by simplifying the complexity of the remote terrestrial infrastructure, which only comprises the DU and RU. This architecture maintains low-level procedures (e.g., synchronization and resource allocation) close to end users while externalizing all other functionalities, leading to delays in internal gNB procedures generated from upper layers (e.g., RRC connection setup). The relay of NR prevents the roll-out of remote terrestrial infrastructure and heavily affects the radio interface between UE and gNB, as has been demonstrated. The trade-off of each architecture shall be considered by operators. In use cases where the deployment of remote infrastructure is not the primary concern, transparent architectures may be well-suited. They offer potential advantages thanks to simpler satellite technologies, such as the reduction in service costs for end users and the straightforward integration with external networks. As an example of the value of this type of architecture, we can assume that a terrestrial operator plans to serve a remote and unserved town by deploying a number of gNBs locally. These base stations will access transparent satellites to reach the distant operator's 5 GC. In this way, the operator is efficiently meeting the town's service needs without requiring a complex wired connection to its 5 GC. The particular case of relaying the NR signal may be challenging, since the two-hop path (ground-space-ground) between UE and gNB notably increases latencies of critical transmissions. This results in negative issues, such as the potential congestion of Hybrid Automatic Repeat Request (HARQ) streams caused by packet losses or delays, or the expiration of certain timers in time-sensitive procedures. Likewise, other problems related to low layers can arise, e.g., difficulties during UE-gNB synchronization. All these challenges lead us to propose regenerative architectures in order to achieve a one-hop path (ground-space) between UE and gNB. In this way, latency is reduced, and thus challenges are slightly mitigated. In this work, a hypothetical usage scenario of regenerative instead of transparent architectures would have presented different challenges. Regardless of the different methodologies that we should have followed, enhancements of time metrics would possibly not exist, as two hops would still be required to reach the destination. However, some of the ex plained technological limitations would likely not have occurred. For instance, the latency reduction in the midhaul could have mitigated the difficulties caused by the non-real-time nature of RFSimulator. Despite this, the identification of benefits in regenerative architectures implies the need for a dedicated study to demonstrate these assumptions. That work would undoubtedly face significant challenges, such as direct radio communication between the UE and the gNB hosted in the satellite. Regenerative architectures offer potential advantages, including reduced latency between the UE and the gNB, and enhanced management of radio resources.