HackMDCell Pattern Generation
Space and HAPS systems typically feature larger cells compared to cellular networks. In addition, the cells may be moving (without a fixed earth reference point) in case of NGSO (Non Geostationary Satellite Orbit) satellite or HAPS system.
跟cellular network相比，Space & HAPS系統的cells比較大並且會移動。
These large cells especially at low operational elevation angles will create a significant differential propagation delay between a UE at cell centre and UE at cell edge and the ratio of the differential increases as the altitude of the satellite and HAPS decreases. In other words, the ratio between propagation delays at cell centre and cell edge is likely to be higher in the context of HAPS as compared to geostationary satellite systems.
Cell的中心UE與邊緣UE的propagation delay差異明顯(特別在低仰角時)，
並且其差比隨衛星與HAPS的高度增加。
The differential delay due to large cell size may create near far effect between UEs during the initial access procedure when the UEs positions are not known. This may require an extended acquisition window to improve performance.
在UEs的位置不知道的時候，在大的cell裡，UEs在進行initial access procedure時會引發near-far effect，這可能需要擴展的採集窗口以提高性能。??
Note however that if the UE position becomes known during a session, the differential delay can be compensated by the network.
但若在session期間得知UEs的位置的話就能補償延遲
The mobility management should accommodate the specific cell patterns (size and position) of NTN networks. Moreover, cells in the non-terrestrial network may cross borders between countries.
Mobility management應要能容納NTN網路中的cell patterns(因為有不同大小且會移動的cells) 另外要注意cell可能會跨國界。
In particular, this will affect the identification method of cells, the design of tracking and location areas, the roaming and billing procedures as well as location based services.
這將影響:
- cells的識別方法
- 追蹤與位置區域的設計
- 漫遊
- 或基於位置的服務
Furthermore, NGSO and HAPS systems generate cells which move around. This causes hand-over to occur not only for mobile units but also for fixed UEs. However, the hand-over caused by such NTN may be anticipated, by exploiting trajectory models such as satellite ephemeris.
因為NGSO與HAPS產生的cell會移動，因此在hand-over上不僅僅考慮移動的UEs，連固定位置的UEs都必須考慮會有hand-over的問題。
Paging and Hand-over procedures should be adapted to take into account the relative motion of the cell pattern with respect to the tracking area. Further analysis on tracking area design may need to be carried out. Mobility management is also to be considered.
paging和hand-over應考慮到cell pattern相對於tracking area的運動。 可能需要對tracking area設計進行進一步分析，還應考慮mobility management。
