In-Flight User Terminals Based On Active Array Antenna For LEO Scenario Including Soft Handover
In-Flight Connectivity services through satellite systems are expected to grow exponentially throughout the 2020 decade. The deployment of new geostationary orbit satellites with superior bandwidth and, particularly, the coming of mega-constellations in low and medium earth orbits (LEO/MEO) with high throughput and low latency, which is ideal for real time services, will result in higher demand and lower running costs. However, there is a significant issue to consider in this type of scenario, the high density of satellites available and their movement introduce not only a continuous tracking in the user terminal but also a mandatory handover when the communication needs to be transferred from one satellite to the next one. Nowadays, user terminals based on reflectors and flat panels with electro-mechanical steering lose the communication during the handover because break-before-make procedure is applied. Beam re-pointing and signal re-connection take a certain time, consequently, the quality of service (QoS) is degraded. Alternatively, two-reflector/flat panel terminals can mitigate this effect and provide make-before-break functionality for seamless handovers in RX, while in TX it can be omitted. However, this solution is not convenient for in-flight terminals which are expected to be compact and low profile to reduce the impact on fuel consumption. In this paper, to approach LEO/MEO scenarios with frequent handovers and high quality of service, the active phased array antennas are addressed to offer better performance than the reflectors. The advantages are listed as follows: much faster beam re-pointing; more compact size and lower profile; reconfigurability of the aperture; and, multiple beam capable for seamless handovers. These characteristics are desired by satellite operators, service providers and airlines, who can get ancillary revenues by offering In-Flight connectivity and entertainment to passengers as well as supporting flight operations and airlines/aircrafts services and maintenance.