Unmanned aerial vehicle (UAV) beam pointing and data rate optimization for high throughput broadband access
Systems and methods configured to form and manage different types of beams toward target ground terminals to “optimally” communicate with the terminals. In one set of embodiments, the UAV generates a set of beams to cover cells on the ground, the beams are divided into groups, and the UAV communications system deterministically and sequentially turns a subset of the beams on/off to reduce cross-beam interference and increase system throughput. In another embodiment, in order to increase throughput, the UAV communications system determines the highest data rate on the downlink and uplink that are decodable at the receiver given the received signal to interference plus noise ratio (SINR) while maintaining a low packet error rate. Systems and methods are described to determine the UAV antenna pattern toward different terminals needed for SINR calculation and data rate determination.
1. An unmanned aerial vehicle (UAV) broadband access system comprising:
an antenna sub-system comprising at least one antenna aperture configured to form a plurality of beams toward a ground coverage area, where the plurality of beams are further subdivided into a plurality of groups of co-active beams;
wherein at least a portion of the plurality of groups of co-active beams are co-frequency;
a UAV radio sub-system comprising one or more transmitters and receivers and configured to transmit and receive signals to and from a set of ground terminals within the ground coverage area; and
wherein the UAV radio sub-system further comprises logic configured to:
assign at least one ground terminal in at least one beam to transmit during a given time slot;
estimate one or more UAV downlink beam gains for the at least one beam assigned to the at least one ground terminal based on one or more of: one or more UAV position coordinates, one or more UAV orientations, and at least one ground terminal location;
determine an optimal downlink data rate for the at least one beam based at least in part of the estimated one or more UAV downlink beam gains; and
transmit downlink data packets to the assigned at least one ground terminal in the at least one beam based at least in part on the determined optimal downlink data rate.
2. The UAV broadband access system of claim 1 , wherein the UAV radio sub-system further comprises logic configured to:
determine an optimal uplink data rate that can be decoded on an uplink based on the measured uplink signal strength and at least one criteria; and
receive uplink data packets based at least in part on the determined optimal uplink data rate.
3. The UAV broadband access system of claim 2 , wherein the UAV radio sub-system further comprises logic configured to send the measured uplink signal strength or the determined optimal uplink data rate to the assigned at least one ground terminal.
4. The UAV broadband access system of claim 1 , wherein the UAV radio sub-system further comprises logic configured to:
schedule downlink transmissions to the assigned at least one ground terminal in the at least one beam; and
receive measured downlink signal strength estimates from the assigned at least one ground terminal on the at least one co-active co-frequency beam.
5. The UAV broadband access system of claim 4 , wherein the UAV radio sub-system further comprises logic configured to:
determine an optimal downlink data rate based at least in part on the received measured downlink signal quality estimates and at least one other criteria; and
transmit downlink data packets based at least in part on the determined optimal downlink data rate.
6. The UAV broadband access system of claim 1 , wherein the UAV radio sub-system further comprises logic configured to:
estimate one or more UAV uplink beam gains based at least in part on one or more of: one or more UAV position coordinates, one or more UAV orientations, and at least one ground terminal location;
determine an optimal uplink data rate based at least in part of the estimated one or more UAV uplink beam gains; and
receive uplink data packets based at least in part on the determined optimal uplink data rate.
7. The UAV broadband access system of claim 6 , wherein the estimated one or more UAV uplink beam gains are performed at a plurality of UAV positions on a cruising orbit.
8. The UAV broadband access system of claim 1 , wherein the UAV radio sub-system further comprises logic configured to:
compute an uplink interference power of an interfering uplink of at least one other ground terminal that transmits during a same time slot as the assigned at least one terminal;
determine an optimal uplink data rate based at least in part on the computed uplink interference power; and
receive uplink data packets based at least in part on the determined optimal uplink data rate.
9. The UAV broadband access system of claim 1 , wherein the UAV radio sub-system further comprises logic configured to:
compute a total uplink interference based at least in part on all ground terminals that are scheduled to transmit at a same time slot as the assigned at least one ground terminal;
compute an expected signal strength from the assigned at least one ground terminal;
compute an expected uplink signal quality of the assigned at least one ground terminal based on the computed total uplink interference and the computed expected signal strength from the assigned at least one ground terminal;
determine an optimal uplink data rate based at least in part of the computed expected uplink signal quality at the assigned at least one ground terminal; and
receive uplink data packets based at least in part on the determined optimal uplink data rate.
10. The UAV broadband access system of claim 1 , wherein the UAV radio sub-system further comprises logic configured to:
compute an downlink interference power of an interfering downlink of at least one other ground terminal that receives during a same time slot as the assigned at least one ground terminal;
determine an optimal downlink data rate based at least in part on the computed downlink interference power; and
transmit downlink data based at least in part on the determined optimal downlink data rate.
11. The UAV broadband access system of claim 1 , wherein the UAV radio sub-system further comprises logic configured to:
compute a total downlink interference based on all ground terminals that are scheduled to receive at a same time slot as the assigned at least one ground terminal;
compute an expected signal strength at the assigned at least one ground terminal;
compute an expected downlink signal quality of the assigned at least one ground terminal based on the computed total downlink interference and the computed expected signal strength at the assigned at least one ground terminal;
determine an optimal downlink data rate based at least in part of the computed expected downlink signal quality at the assigned at least one ground terminal; and
transmit downlink data packets based at least in part on the determined optimal downlink data rate.
12. A method for receiving data packets in a UAV broadband access system, comprising:
forming at least one beam toward a ground coverage area;
measuring an uplink signal estimate of received signals on the formed at least one beam;
determining an optimal uplink data rate that can be decoded on the uplink based on the measured uplink signal estimate and at least one criteria; and
receiving uplink data packets on the formed at least one beam based at least in part on the determined optimal uplink data rate.
13. The method of claim 12 , further comprising:
transmitting a reference signal on at least one other beam;
receiving a measured downlink signal estimate of the at least one other beam from at least one ground terminal within the ground coverage area;
determining an optimal downlink data rate based at least in part on the received measured downlink signal estimate and at least one other criteria; and
transmitting downlink data packets based at least in part on the determined optimal downlink data rate.
14. The method of claim 13 , further comprising transmitting the measured uplink signal estimate to the at least one ground terminal within the ground coverage area.
15. A ground terminal apparatus configured to communicate with an unmanned aerial vehicle (UAV) broadband access system, the ground terminal apparatus comprising:
a radio transceiver configured to transmit and receive signals to and from the UAV;
a processor coupled to the radio transceiver; and
logic configured to:
determine one or more beams that are associated with the UAV;
determine one or more time slots that are assigned for transmission;
transmit one or more reference signals according to the determined one or more time slots and determined one or more beams;
measure a downlink signal estimate of received signals on a downlink;
determine an optimal downlink data rate that can be decoded on the downlink based on the measured downlink signal estimate and at least one criteria;
receive downlink data packets based at least in part on the determined optimal downlink data rate; and
wherein the transmitted one or more reference signals are associated with the UAV.
16. The ground terminal apparatus of claim 15 , wherein each group of co-active beams are further associated with one or more frequencies.
17. The ground terminal apparatus of claim 15 , wherein the one or more reference signals are further encoded with a UAV beam specific code that identifies the determined one or more beams from a plurality of beams.
18. The ground terminal apparatus of claim 15 , wherein the determined one or more beams are further associated with a group of co-active beams.