# Worldwide Coverage Mobile Systems for
## 7 Conclusions  
Smart Cities is a fact that must be faced during the next decade to transform cities into smart. The Smart Cities concept includes the management fo the different services offered to citizens, including health, education, administration, energy, transportation, etc. These services are supported by ICT. Appropriate infrastructures are required to provide ubiquitous access to services and information, in a worldwide context. Satellite communications seem to be the way to achieve worldwide mobile communications and ubiquitous access to services and data. Among the various satellite constellation types, LEO is identified as the most appropriate for different reasons, among them, lower satellites construction and launch costs, smaller antennas size, and lower transmission power (which affects battery life).  
Hence, the main motivation for this investigation is the need for providing worldwide coverage for mobile communications, even in polar regions, and terrestrial mobile networks cannot offer such a feature. The main limitation of the terminals is the antenna size factor, and novel antennas must be developed. Hence, this paper has analysed and compared the most relevant features and design methods of antennas aimed at worldwide mobile communications using LEO satellite constellations. The main constraints for the integration of those antennas in the future terminals for global coverage communications are size, weight, and steering capabilities.  
Three systems, which are currently being deployed, were taken as references: OneWeb, SpaceX, and Telesat. These constellations operate in the same frequency band in the terrestrial segment (Ku-band). The operation requirements were analysed to establish the antenna design constraints. A novel design technique, named SIW (Substrate Integrated Waveguide), was introduced due to its integration capability.  
The main contribution of the authors is the conception of a novel antenna based on the new SIW technology, operating in the Ku-band, aimed at global coverage mobile communications through LEO satellites. The features of the designed antenna were compared with the ones from other attacks. Benefits, advantages, and drawbacks of the proposed antenna were highlighted. The proposed antenna demonstrates to be a beneficial solution to meet the design constraints for such an application: appropriate performance, light, low cost, and small size factor.  
Although the novel antenna seems to be appropriate for the described purpose, further investigation is needed to obtain antennas with smaller size.  
Both authors contributed equally. Both authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
The authors declare no conflict of interest.  
The following abbreviations are used in this manuscript:  
\begin{tabular}{l l} AR BW & Axial Ratio Bandwidth \\ ee6 MBB & enhanced Mobile BroadBand \\ CP & Circular Polarization \\ DL & Downlink \\ ESA & European Space Agency \\ GEO & Geostationary Earth Orbit \\ HEO & High Earth Orbit \\ HMSIW & Half-Mode Substrate Integrated Waveguide \\ FFTH & Fibre to the Home \\ ICT & Information and Communicatio Technologies \\ ITU & International Telecommunication Union \\ KPI & Key Performance Indicator \\ LEO & Low Earth Orbit \\ \end{tabular}  
LNB Low Noise Block MEO Medium Earth Orbit SAR Synthetic Aperture Radar SM Substrate Integrated Waveguide UE User Equipment UL Uplink VSWR Voltage Standing Wave Ratio WiMax Worldwide Interoperability for Microwave Access