Ground Stations of Arrays to Increase the LEO Download Capacity

Abstract

To lower costs and reduce latency, a network of adaptive array ground stations, distributed across the United States, is considered for the downlink of a polar-orbiting low earth orbiting (LEO) satellite. Assuming the X-band 105 Mbps transmitter of NASA's Earth Observing 1 (EO-1) satellite with a simple line-of-sight propagation model, the average daily download capacity in bits for a network of adaptive array ground stations is compared to that of a single 11 m dish in Poker Flats, Alaska. Each adaptive array ground station is assumed to have multiple steerable antennas, either mechanically steered dishes or phased arrays that are mechanically steered in azimuth and electronically steered in elevation. Phased array technologies that are being developed for this application are the spacefed lens (SFL) and the reflectarray. Optimization of the different boresight directions of the phased arrays within a ground station is shown to significantly increase capacity; for example, this optimization quadruples the capacity for a ground station with eight SFLs. Several networks comprising only two to three ground stations are shown to meet or exceed the capacity of the big dish. Cutting the data rate by half, which saves modem costs and increases the coverage area of each ground station, is shown to increase the average daily capacity of the network for some configurations.

Orthogonal Versus Zero-Forced Beamforming in Multibeam Antenna Systems: Review and Challenges for Future Wireless Networks

“…The antenna challenges are to limit gain and power efficiency losses due to array amplitude tapers, beam cross-overs, and to greatly reduce the side lobe interference accumulation at each user, occurring in current systems employing multiple beam forming matrices [8]. Furthermore, the need for efficient and flexible adaptive multiple beam forming with co-channel interference suppression in future satellite communications at space [36], [37] and ground [38] segments is well recognized [39]. Similarly, 5G mobile communications base stations and user equipment require multiple beams and low interference.…”