U.S. patent application number 15/478032 was filed with the patent office on 2017-07-20 for antenna beam management and gateway design for broadband access using unmanned aerial vehicle (uav) platforms.
The applicant listed for this patent is Ubiqomm LLC. Invention is credited to Ahmad Jalali, Dhinakar Radhakrishnan.
Application Number | 20170207847 15/478032 |
Document ID | / |
Family ID | 55068378 |
Filed Date | 2017-07-20 |
United States Patent
Application |
20170207847 |
Kind Code |
A1 |
Jalali; Ahmad ; et
al. |
July 20, 2017 |
ANTENNA BEAM MANAGEMENT AND GATEWAY DESIGN FOR BROADBAND ACCESS
USING UNMANNED AERIAL VEHICLE (UAV) PLATFORMS
Abstract
Systems and methods for creating beams from a non-terrestrial
vehicle (e.g., unmanned aerial vehicle (UAV)) toward user terminals
and gateways on the ground. Another aspect of the disclosure
includes systems and methods for switching the UAV beams toward the
user terminals and gateways as the UAV moves in its orbit. Still
another aspect of the disclosure describes systems and methods for
routing traffic from user terminals to the internet via multiple
gateways.
Inventors: |
Jalali; Ahmad; (San Diego,
CA) ; Radhakrishnan; Dhinakar; (San Diego,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ubiqomm LLC |
San Diego |
CA |
US |
|
|
Family ID: |
55068378 |
Appl. No.: |
15/478032 |
Filed: |
April 3, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14486916 |
Sep 15, 2014 |
9614608 |
|
|
15478032 |
|
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62024421 |
Jul 14, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04W 84/06 20130101;
H04W 88/16 20130101; Y02D 70/164 20180101; H04B 7/18504 20130101;
Y02D 70/446 20180101; H01Q 25/00 20130101; H04W 40/06 20130101;
H04W 16/28 20130101; Y02D 70/444 20180101; H04B 7/0695 20130101;
H01Q 1/28 20130101; H04B 7/0617 20130101; H04B 7/2041 20130101;
Y02D 70/322 20180101; Y02D 30/70 20200801; Y02D 70/122
20180101 |
International
Class: |
H04B 7/185 20060101
H04B007/185; H04W 40/06 20060101 H04W040/06; H04W 16/28 20060101
H04W016/28; H04B 7/06 20060101 H04B007/06; H04B 7/204 20060101
H04B007/204 |
Claims
1.-20. (canceled)
21. A system for providing broadband access using unmanned aerial
vehicles (UAVs), comprising: a first antenna system comprising
multiple first antenna sub-apertures, where each first antenna
sub-aperture is configured to form at least one first beam toward
one or more user terminals; a second antenna system comprising
multiple second antenna sub-apertures, where each second antenna
sub-aperture is configured to form at least one second beam toward
one or more gateways of a set of ground gateways configured to
provide connectivity to a core network; a first set of radio
transceivers and modems configured to transmit and receive a
plurality of first signals to/from the one or more user terminals;
a second set of radio transceivers and modems configured to
transmit and receive a plurality of second signals to/from the one
or more gateways; a router/processor sub-system configured to route
packets between the one or more user terminals and the one or more
gateways and to manage the at least one first and at least one
second beams, where the router/processor sub-system is further
configured to: determine at least one fading condition that affects
transmission or reception of the plurality of first or second
signals; and intelligently manage power consumption based on the
determined at least one fading condition.
22. The system of claim 21, where: the multiple second antenna
sub-apertures are comprised of K antenna elements, each spaced at
substantially a half wavelength apart from an adjacent antenna
element; each of the second antenna sub-apertures are configured to
form M beams via one or more appropriate phases of the K antenna
elements; wherein K and M are integer values; and wherein the
router/processor sub-system is configured to select at least one of
the M beams based on a determined signal quality.
23. The system of claim 21, where the router/processor sub-system
is configured to: measure at least two signal to interference plus
noise ratios (SINRs) from a received signal on a primary beam
associated with a primary gateway and at least one other candidate
beam; compare the at least two SINRs associated with the primary
beam and the at least one other candidate beam; and determine when
the primary beam should be switched to the at least one other
candidate beam based at least in part on the comparison.
24. The system of claim 21, where the router/processor sub-system
is configured to: measure at least two signal to interference plus
noise ratios (SINRs) from a received signal on a primary beam and
at least one other neighbor beam; compare the at least two SINRs
associated with the primary beam and the at least one other
neighbor beam; and determine when the primary beam should be
switched to a neighbor beam based at least in part on the
comparison; and execute the beam switch from the primary beam to
the neighbor beam.
25. The system of claim 21, where the router/processor sub-system
is configured to: determine a minimum transmit power to achieve a
target signal quality for a given beam; and adjust a power
amplifier associated with the given beam to achieve the minimum
transmit power.
26. The system of claim 25, where the target signal quality is
determined based on a rain fade condition and the adjustment of the
power amplifier comprises increasing the minimum transmit power in
order to compensate for the rain fade condition.
27. The system of claim 21, where the router/processor sub-system
is configured to: receive a beam change request originating from
the one or more user terminals; and execute the beam change request
so as to switch beams for the one or more user terminals.
28. The system of claim 21, where the router/processor sub-system
is configured to: measure at least two signal to interference plus
noise ratios (SINRs) from a received signal on a primary beam
associated with a primary gateway and at least one inactive beam;
compare the at least two SINRs associated with the primary beam and
the at least one inactive beam; and determine when the primary beam
should be switched to the at least one inactive beam based at least
in part on the comparison.
29. A method for providing broadband access via an unmanned aerial
vehicle (UAV), comprising: forming at least one first beam towards
one or more user terminals; forming at least a second beam towards
one or more gateways; transacting a first plurality of signals with
the one or more user terminals; transacting a second plurality of
signals with the one or more gateways via the second beam;
monitoring the one or more gateways for a blockage condition; and
when a blockage condition occurs, forming a third beam towards one
or more diversity gateways and transacting the second plurality of
signals via the third beam.
30. The method of claim 29, further comprising switching the second
beam to an inactive state when the blockage condition occurs.
31. The method of claim 30, further comprising monitoring the one
or more diversity gateways with the third beam in the inactive
state when the blockage condition is not present.
32. The method of claim 29, wherein the act of monitoring the one
or more gateways for the blockage condition comprises measuring a
signal to noise ratio (SNR).
Description
PRIORITY AND RELATED APPLICATIONS
[0001] This application claims priority to co-pending and co-owned
U.S. Provisional Patent Application Ser. No. 62/024,421 filed Jul.
14, 2014, and entitled "METHODS AND APPARATUS FOR MITIGATING FADING
IN A BROADBAND ACCESS SYSTEM USING DRONE/UAV PLATFORMS", which is
incorporated herein by reference in its entirety.
[0002] The application is also related to co-owned and co-pending
U.S. patent application Ser. No. 14/295,160 filed on Jun. 3, 2014,
and entitled "METHODS AND APPARATUS FOR MITIGATING FADING IN A
BROADBAND ACCESS SYSTEM USING DRONE/UAV PLATFORMS"; co-owned and
co-pending U.S. patent application Ser. No. 14/222,497 filed on
Mar. 21, 2014, and entitled "BROADBAND ACCESS TO MOBILE PLATFORMS
USING DRONE/UAV"; and co-owned and co-pending U.S. patent
application Ser. No. 14/223,705 filed on Mar. 24, 2014, and
entitled "BROADBAND ACCESS SYSTEM VIA DRONE/UAV PLATFORMS", each of
the foregoing incorporated by reference herein in its entirety.
COPYRIGHT
[0003] A portion of the disclosure of this patent document contains
material that is subject to copyright protection. The copyright
owner has no objection to the facsimile reproduction by anyone of
the patent document or the patent disclosure, as it appears in the
Patent and Trademark Office patent files or records, but otherwise
reserves all copyright rights whatsoever.
BACKGROUND
[0004] 1. Technological Field
[0005] The present disclosure describes, among other things,
systems and methods for creating beams from an unmanned aerial
vehicle (UAV) toward user terminals and gateways on the ground.
Another aspect of the disclosure includes systems and methods for
switching the UAV beams toward the user terminals and gateways as
the UAV moves in its orbit. Still another aspect of the disclosure
describes systems and methods for routing traffic from user
terminals to the internet via multiple gateways.
[0006] 2. Description of Related Technology
[0007] As internet traffic has increased, new technologies are
needed to deliver broadband access to homes and enterprises at
lower cost and to places that are not yet covered. Examples of
current broadband delivery systems include terrestrial wired
networks such as DSL (Digital Subscriber Line) on twisted pair,
fiber delivery systems such as FiOS (Fiber Optic Service), and
geo-stationary satellite systems. The current broadband access
systems have a number of short comings. One issue is lack of
service in remote and/or lightly populated areas. Geo-stationary
satellites do provide service in remote areas of the developed
world such as the United States. Poorer areas of the world,
however, lack adequate satellite capacity.
[0008] A notable reason satellite capacity has not been adequately
provided in poor regions of the world is the relatively high cost
of satellite systems. Due to adverse atmospheric effects in
satellite orbits, satellite hardware must be space qualified and is
costly. Launch vehicles to put the satellites in orbit are also
costly. Moreover, due to the launch risk and the high cost of
satellites, there may be significant insurance costs for the
satellite and the launch. Therefore, broadband satellite systems
and services are relatively costly and difficult to justify,
particularly in poorer regions of the world. It is also costly to
deploy terrestrial systems such as fiber or microwave links in
lightly populated regions. The small density of subscribers does
not justify the deployment cost.
[0009] Despite the broad variety of ways for providing broadband
access to consumers in the prior art, none achieve the desired
level of flexibility and cost, particularly for consumers that
reside in remote or sparsely populated geographic areas. Moreover,
terrestrial based methods for providing broadband access to
consumers do not provide the requisite flexibility for changing
populations and densities. Accordingly, methods and apparatus are
needed that provide the requisite level of desired flexibility and
cost for providing broadband access to consumers.
SUMMARY
[0010] The present disclosure describes, inter alia, systems and
methods for creating beams from an unmanned aerial vehicle (UAV)
toward user terminals and gateways on the ground.
[0011] In a first aspect, a system for providing broadband access
using unmanned aerial vehicles (UAVs) is disclosed. In one
embodiment, the system includes a first antenna system includes
multiple first antenna sub-apertures, where each first antenna
sub-aperture is configured to form at least one first beam toward
one or more user terminals; a second antenna system includes
multiple second antenna sub-apertures, where each second antenna
sub-aperture is configured to form at least one second beam toward
one or more gateways of a set of ground gateways configured to
provide connectivity to a core network; a first set of radio
transceivers and modems configured to transmit and receive a
plurality of first signals to/from the one or more user terminals;
a second set of radio transceivers and modems configured to
transmit and receive a plurality of second signals to/from the one
or more gateways; and a router/processor sub-system configured to
route packets between the one or more user terminals and the one or
more gateways and to manage the at least one first and at least one
second beams.
[0012] In one variant, the multiple second antenna sub-apertures
include K antenna elements, each spaced at substantially a half
wavelength apart from an adjacent antenna element. Each of the
second antenna sub-apertures are configured to form M beams via one
or more appropriate phases of the K antenna elements, and the
router/processor sub-system selects one of the M beams based on a
determined signal quality.
[0013] In an alternative variant, the router/processor sub-system
is configured to: measure at least two signal to interference plus
noise ratios (SINRs) from a received signal on a primary beam
associated with a primary gateway and at least one other candidate
beam; compare the at least two SINRs associated with the primary
beam and the at least one other candidate beam; and determine when
the primary beam should be switched to the at least one other
candidate beam based at least in part on the comparison.
[0014] In yet another variant, the router/processor sub-system is
configured to: execute a UAV beam switch request configured to
cause at least one user terminal to be switched to a different
beam.
[0015] In yet another variant, the router/processor sub-system is
configured to: determine a minimum transmit power to achieve a
target signal quality for a given beam; and adjust a power
amplifier associated with the given beam to achieve the minimum
transmit power.
[0016] In yet another variant, the target signal quality is
indicative of a rain fade condition and the adjustment of the power
amplifier includes increasing the transmit power in order to
compensate for the rain fade condition.
[0017] In yet another variant, the router/processor sub-system is
configured to: measure at least two signal to interference plus
noise ratios (SINRs) from a received signal on a primary beam and
at least one other neighbor beam; compare the at least two SINRs
associated with the primary beam and the at least one other
neighbor beam; and determine when the primary beam should be
switched to a neighbor beam based at least in part on the
comparison; and execute the beam switch from the primary beam to
the neighbor beam.
[0018] In yet another variant, the router/processor sub-system is
configured to: measure at least two signal to interference plus
noise ratios (SINRs) from a received signal on a primary beam
associated with a primary gateway and at least one inactive beam;
compare the at least two SINRs associated with the primary beam and
the at least one inactive beam; and determine when the primary beam
should be switched to the at least one inactive beam based at least
in part on the comparison.
[0019] In a second aspect, an antenna fixture for providing
broadband access using UAVs is disclosed. In one embodiment, the
antenna fixture includes a multi-faceted antenna structure having a
plurality of apertures, each of the apertures further including a
plurality of sub-apertures. Each sub-aperture is responsible for
forming at least one beam.
[0020] In one variant, the multi-faceted antenna structure includes
apertures that are placed at an angle with respect to a given
aperture; the apertures that are placed at an angle are further
configured to provide coverage to a location at the edge of a
coverage area for the antenna fixture.
[0021] In yet another variant, the multi-faceted antenna structure
is further configured to form at least one beam toward one or more
gateways of a set of ground gateways that are configured to provide
connectivity to a core network.
[0022] In yet another variant, the formed at least one beam
originates from one of the apertures that are placed at an angle
with respect to the given aperture.
[0023] In a third aspect, a system for providing broadband access
is disclosed. In one embodiment, this system includes a plurality
of gateways, each of the gateways being coupled to a core network;
one or more user terminals; and an unmanned aerial vehicle (UAV).
The UAV includes a first antenna system configured to form at least
one first beam towards the one or more user terminals; a second
antenna system configured to form at least one second beam toward
the one or more gateways; a first set of radio transceivers and
modems configured to transmit and receive a first plurality of
signals to/from the one or more user terminals; a second set of
radio transceivers and modems configured to transmit and receive a
second plurality of signals to/from the one or more gateways; and a
router/processor sub-system configured to route packets between the
one or more user terminals and at least one of the plurality of
gateways and to manage the at least one first and at least one
second beams.
[0024] In one variant, the system collectively comprises a beam
network, the beam network having a frequency reuse of at least
three such that a given beam is assigned a given frequency such
that adjacently located beams to the given beam do not share the
given frequency.
[0025] In yet another variant, the frequency reuse reduces
interference between adjacent beams thereby increasing a signal to
noise plus interference ratio (SINR) and an achieved data rate.
[0026] In yet another variant, the gateways include a first gateway
disposed at a first location of a UAV coverage area and a second
gateway disposed at a second location of the UAV coverage area, the
first and second locations being disposed at opposite ends of the
UAV coverage area thereby providing gateway diversity for the
system.
[0027] In yet another variant, the second gateway provides
connectivity for the UAV to the core network when the first gateway
is blocked from providing connectivity to the UAV during UAV
maneuvering.
[0028] In yet another variant, the router/processor sub-system of
the UAV is configured to: measure at least two signal to
interference plus noise ratios (SINRs) from a received signal on a
primary beam associated with a primary gateway and at least one
other candidate beam; compare the at least two SINRs associated
with the primary beam and the at least one other candidate beam;
and determine when the primary beam should be switched to the at
least one other candidate beam based at least in part on the
comparison.
[0029] In yet another variant, the at least one other candidate
beam comprises an inactive beam.
[0030] In yet another variant, the UAV further includes a power
management subsystem that is configured to manage power consumption
for the UAV based at least in part on measured atmospheric
conditions.
[0031] In a fourth aspect, systems and methods for switching the
UAV beams toward the user terminals and gateways as the UAV moves
in its orbit are disclosed.
[0032] In a fifth aspect, systems and methods for routing traffic
from user terminals to the internet via multiple gateways are
disclosed.
[0033] In a sixth aspect, systems and methods for managing power
control so as to minimize UAV power usage are disclosed.
[0034] In a seventh aspect, systems and methods for terminal
antenna and gateway antenna beam steering towards a UAV are
disclosed.
[0035] In an eighth aspect, systems and methods for providing a
phased array approach to UAV beam forming are disclosed.
[0036] These and other aspects shall become apparent when
considered in light of the disclosure provided herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0037] In the following figures, similar components are identified
using the same reference label. Multiple instances of the same
component in a figure are distinguished by inserting a dash after
the reference label and adding a second reference label.
[0038] FIG. 1.1 is a graphical depiction of one exemplary beam
network design configured to serve user terminals.
[0039] FIG. 1.2 is a graphical depiction of one exemplary beam
network design configured to connect to gateways.
[0040] FIG. 2.1 is a graphical depiction of one exemplary unmanned
aerial vehicle (UAV) antenna fixture for forming beams to user
terminals and gateways.
[0041] FIG. 2.2 is a graphical depiction of one exemplary unmanned
aerial vehicle (UAV) antenna sub-aperture for forming beams to user
terminals and gateways.
[0042] FIG. 3 is a high level representation of one exemplary
hardware architecture of one exemplary unmanned aerial vehicle
(UAV), useful in conjunction with the various aspects described
herein.
[0043] FIG. 4 is a high level block diagram of an unmanned aerial
vehicle (UAV), routing data traffic to a core network via multiple
gateways.
[0044] FIG. 5 is a logical representation of exemplary electronic
beam forming circuitry.
[0045] All Figures.COPYRGT. Copyright 2014 Ubiqomm, LLC. All rights
reserved.
DETAILED DESCRIPTION
[0046] Reference is now made to the drawings, wherein like numerals
refer to like parts throughout.
[0047] As used herein, the term "unmanned aerial vehicle" and "UAV"
are used interchangeably and refer to any type of aerial vehicle
that is intended to operate without an onboard human pilot.
Examples, of these unmanned aerial vehicles or UAVs include,
without limitation, drones, robocopters, balloons, blimps,
airships, etc. These UAVs may include propulsion systems, fuel
systems, and onboard navigational and control systems. In one
exemplary embodiment, the UAV includes a fixed wing fuselage in
combination with a propulsion means (e.g., a propeller, jet
propulsion, etc.). In alternative embodiments, the UAV comprises a
so-called robocopter, propelled by, for example, one or more
rotors. The UAV may carry fuel onboard or may function using
alternative energy sources that do not necessarily need to be
carried onboard such as, for example, solar energy.
Exemplary UAV Beam Network and Beam Switching Mechanism--
[0048] In one embodiment, an unmanned aerial vehicle (UAV) provides
broadband access to user terminals in an area of radius as large as
300 km. As will be discussed next, two (2) different UAV antenna
systems are needed: (i) a first antenna system to provide coverage
to user terminals which are referred to generally herein as "UAV
user terminal antenna systems", and (ii) a second antenna system to
provide coverage to gateways which are referred to generally herein
as "UAV gateway antenna systems". In at least certain deployment
scenarios, the gateways may be located farther from the UAV
coverage area compared to the user terminals because the wireline
connectivity to the gateway may not be available close to the
UAV.
[0049] FIG. 1.1 illustrates one possible beam network design
configured to serve user terminals. As shown, the beam network 100
has a frequency reuse of three (3) among the beams, i.e. the
available spectrum is divided into three bands of F1, F2, and F3
and each beam is assigned one of the three frequency bands in such
as a way that no two adjacent beams use the same frequency. The
dashed circles 110 depict the beams that cover each hexagonal area
120. The hexagons 120 are shown to help visualize the contiguous
coverage area, however the actual beam footprints overlap (as shown
by the dashed circles). The three dashed circle types correspond to
the three frequency bands. Frequency reuse reduces interference
from adjacent beams and helps increase signal to noise plus
interference ratio (SINR) and the achieved data rate.
[0050] While the illustrated embodiment depicts a beam network that
comprises thirty seven (37) beams arranged according to a frequency
reuse factor of three (3), artisans of ordinary skill will readily
appreciate that a different number of beams and/or frequency reuse
factors may be used to suit a variety of other network
considerations (e.g., cost, coverage, network complexity, etc.).
For example, such a choice in the number of beams and/or frequency
reuse factors may be chosen so as to reduce the level of
interference from adjacent beams while helping to increase SNIR and
the achieved data rate.
[0051] As will be discussed below (see e.g., Exemplary Antenna
Systems), there are generally two types of antenna systems used in
UAVs. In so-called "fixed beam" systems, the beams are not actively
adjusted/steered to compensate for UAV roll and other movements. In
one exemplary embodiment of a fixed beam system, the network of
beams should be designed so that the beams cover a wider area than
the anticipated coverage area (e.g., where the user terminals are).
The reason for the wider coverage area is that as the UAV rolls,
the beams formed on the ground as shown in FIG. 1.1 will move on
the ground. Therefore, the beams must cover a wider area so that as
the beams move due to UAV roll/turn, the desired average area of
user terminals will still be covered by beams. In so-called "active
beam steering" systems, such as e.g., phased arrays, the UAV
adjusts the beams so the beams stay fixed on the same location
("footprint") on the ground despite the movement of UAV.
[0052] As previously noted, for fixed beam systems, the beams will
move with respect to any user terminals within the coverage area
due to UAV movements (such as roll and turn). Generally, the
approach to handle beam movements is to switch the user terminal
from one beam to another as the beams move.
[0053] The hardware architecture 300 for UAV communications payload
to handle this beam switching is shown in FIG. 3. The
communications payload is an apparatus which comprises antenna
sub-apertures 302, 314 configured to form beams toward gateways and
user terminals, modems 306 configured to demodulate/modulate
signals from/to user terminals, modems 310 configured to
demodulate/modulate signals from/to gateways, a set of radio
transceivers and power amplifiers 312, 304 that are configured to
connect to the UAV gateway, and user terminal antenna sub-apertures
314, 302. A processor/router subsystem 308 is configured to, inter
alia, provide the requisite broadband access between the user
terminals and the gateways.
[0054] The user terminal radio sub-system is configured to
demodulate and decode signals from the beam(s) to which the user
terminal has been assigned (i.e., as used herein, the so-called
"primary beam" or "primary set"). The beam(s) that are adjacent to
the user terminal's primary beam are referred to as the "neighbor
set beams" or "neighbor set" for the user terminal. The user
terminal's radio sub-system will periodically tune to the frequency
channels of the neighbor set beams and measure one or more signal
to interference plus noise ratios (SINRs) corresponding to the
preamble signals that the UAV communications payload has
transmitted on those beams. In one embodiment, this periodic tuning
will occur at regular (i.e., fixed) intervals. Alternatively, this
tuning may occur at dynamic intervals (periodically or
aperiodically). For example, in one embodiment, the frequency of
time between periods of measurement for the neighbor set SINR(s)
may increase as a function of signal quality. In other words, as
the SINR(s) measurement for the neighbor set improves, the periodic
tuning may occur more frequently in anticipation of a possible
switch from the primary beam set to a different beam.
Alternatively, the interval of periodic tuning may be adjusted as a
function of UAV motion (e.g., as a result of the roll and pitch
motions of the UAV).
[0055] In yet another alternative embodiment, the user terminal may
also search one or more preambles of the neighbor set beams when
the SINR of its primary set falls below a threshold. If the user
terminal radio sub-system detects a beam in the neighbor set whose
SINR (or other signal quality metric), is within a certain
threshold of that of the user terminal's primary beam, then the
user terminal may request that the UAV communications payload
switch the user terminal to a different beam. In other cases, where
the user terminal radio sub-system detects a beam in the neighbor
set whose SINR (or other signal quality metric) is acceptable and
where the user terminal's primary beam is unacceptable, then the
user terminal may request that the UAV communications payload
switch the user terminal to a different beam. Still other schemes
for triggering user terminal switch-over will be made apparent to
those of ordinary skill, given the contents of the present
disclosure. Similarly, for clarity, FIG. 3 depicts all signaling
from user terminals being received at the user terminal modems and
processed by the router/processor sub-system 308; however, it is
appreciated that various other configurations may be substituted
with equal success by ones of ordinary skill in the related arts,
the depicted embodiment being merely illustrative.
[0056] In some circumstances, the gateways may be as far as 300 km
away from the center of the UAV's coverage area. Further
complicating matters, exemplary UAV may be stationary or moving
(e.g., according to a circular pattern, clover pattern, etc.)
around the center of coverage. Moreover, the UAV may go through
roll and pitch motions which could result in obstructing the view
of any antennas installed under the UAV. For example, if a gateway
is placed far from the UAV such that the elevation angle from the
gateway toward the UAV is lower than the angle that the UAV will
roll, then the UAV antenna may be blocked with respect to the
specified gateway during the roll. Here, the elevation angle from a
user terminal/gateway to the UAV is defined to be the angle between
the line tangent to earth from the location of the user
terminal/gateway and the line connecting the user terminal/gateway
to the UAV position. One way to solve this blockage condition is to
use a second gateway 140, such as for example that shown in FIG.
1.2, which is far enough from the first gateway 130 that it would
be visible during the UAV roll while the first gateway is blocked.
Even though the UAV loses coverage to one gateway, the other
gateway will be in the coverage of UAV antenna and can provide
connectivity to the UAV. In other words, gateway blockage due to
distance and UAV movement (e.g., banking) may be solved using
gateway diversity. In some cases, gateway diversity may also be
used to mitigate rain fade.
[0057] FIG. 1.2 shows an exemplary implementation of a beam network
100 configured to provide coverage to gateways 130, 140. FIG. 1.2
provides for up to N beams from the UAV toward gateway positions;
however, as shown, only beams N and N/2 are transmitting, whereas
the other beams (e.g., 1, 2, N/2+1, N-1, etc.) are not. The central
circle 150 in the middle represents the coverage to user terminals
(which was also illustrated in FIG. 1.1). The number of UAV beams
needed to connect to gateways depends, in an exemplary
implementation, on the frequency band used and the antenna gain
needed. For example, a UAV may add more beams where there is
significant interference, or alternatively reduce beams where there
is very little traffic, etc.
[0058] Consider the exemplary scenario where the UAV turns a
previously inactive beam "on" as the gateway passes through the
beam's coverage area. As the UAV moves around in e.g., a circle,
previously inactive beams may have better visibility to the
gateway. As each UAV beam passes over the gateway, the UAV gateway
beam management system switches the UAV gateway beam serving the
gateway from one beam to another. In one aspect of the present
disclosure, the UAV communication system considers one or more of a
number of factors when determining to switch to another beam (e.g.,
signal strength, network considerations, geographic location,
etc.). In one embodiment, even though only a few beams are actively
transmitting to a gateway (as shown, beams N and N/2 are
transmitting to gateway A 130 and B 140 respectively), the modems
connected to the inactive beams receive and monitor signals sent by
the gateway. FIG. 3 shows a high level hardware block diagram of
the UAV beam switching scheme. During operation, the UAV
communication modems 310 compare the SINR received from each
gateway on all UAV gateway beams (both active and inactive beams);
when an inactive beam has a received SINR that meets one or more
prescribed criteria (e.g., is within a threshold of the active
transmitting beam), then the UAV communication system may switch
the transmitting beam to the new beam.
[0059] In some instances, the criterion/criteria (e.g., threshold)
may be statically set or dynamically modified so as to optimize
operation. For example, a threshold which is small may result in
pre-emptive switching (and/or unnecessary "chum"), whereas a
threshold which is large may provide slower switching which could
degrade performance.
[0060] Where there are multiple gateways, then multiple UAV gateway
beams may be transmitting simultaneously. For example, as shown in
FIG. 1.2 two gateways 130, 140 (i.e., gateways A and B) are on
opposite sides of the UAV coverage area. In this case, the UAV
gateway beams that are transmitting toward the two gateways are not
neighboring beams, and therefore do not cause interference to each
other. While FIG. 1.2 reduces gateway beam interference through
intelligent management of the spatial locations of the gateways, it
is appreciated that other measures to prevent interference may be
used. For example, gateway beams may be on different frequencies,
use different time slots, and/or spreading codes, etc.
Exemplary Antenna Systems--
[0061] In one exemplary embodiment, the UAV comprises one or more
UAV user terminal antenna systems and one or more UAV gateway
antenna systems. The user terminal antenna system is configured to
communicate with one or more user terminals whereas the gateway
antenna systems are configured to communicate with one or more
gateways.
[0062] Referring now to the UAV user terminal antenna system, the
antenna fixture at the UAV is configured to cover a wide range of
elevation angles toward the user terminals. As an illustration,
FIG. 2.1 shows an exemplary implementation of a UAV antenna fixture
200 configured to serve user terminals. The multi-faceted antenna
structure has multiple apertures 202 to cover a wide range of
angles. Additionally, this antenna has multiple apertures which are
designed to be conformal and aerodynamic. The antenna fixture 200
of FIG. 2.1 has seven (7) apertures/face. Each aperture covers a
corresponding area (which may or may not overlap with other
apertures). Each aperture comprises one or more smaller
sub-apertures 204 shown as rectangles. Each sub-aperture element
204 creates one beam. The antenna fixture 200 is designed such that
it is flat in the middle and tapers down toward the surface of the
UAV at an inclination angle so that the antenna sub-apertures
placed on the antenna fixture provide coverage to different areas.
In one exemplary embodiment, the antenna may be installed under the
UAV however it is appreciated that other implementations may place
antennas at other locations so as to accommodate other uses.
[0063] The aperture 202 in the center, (as shown, numbered 7),
covers locations closest to the UAV. Apertures 1 through 6 provide
coverage to locations at the edge of the coverage. Antenna
apertures 1 through 6 are placed at an angle with respect to
aperture 7 in order to cover farther distances. As previously
described, apertures 1 through 7 each comprise antenna
sub-apertures and each of these sub-apertures creates a different
beam on the ground. For example, in order to form the thirty-seven
(37) beams of FIG. 1.1, the antenna fixture of FIG. 2.1 would need
thirty-seven (37) sub-apertures each creating one beam, distributed
among the seven (7) different faces, such that the sub-apertures
generate the desired coverage area.
[0064] Referring now to the UAV gateway antenna system, the gateway
may be placed much farther from the center of coverage area than
the user terminals, therefore in one exemplary embodiment, the UAV
antenna fixture serving the gateways would typically need to point
its beams at lower elevation angles toward the gateway. In one
implementation, the shape of the antenna fixture for gateways is
the same as that of the UAV user terminal antenna fixture 200
(shown in FIG. 2.1); however, in order to provide the
aforementioned lower elevation angles toward the gateway, the UAV
antenna fixture for the gateway will need N sub-apertures placed
around the circumference of the fixture tilted down with respect to
the chord of the wing to cover father distances from the UAV where
the gateways may be. In one such implementation, the N
sub-apertures provide 360.degree. of coverage in azimuth, directed
at substantially a 45.degree. angle of elevation.
[0065] Since the gateway may be in a wide area with a wide range of
different elevation angles with respect to the UAV, the UAV gateway
antenna system may be required to support a significant coverage
area. Consider the following implementation where the gateways may
be anywhere between 5.degree. to 50.degree. of elevation with
respect to the UAV. The sub-aperture beams must cover an elevation
angle range of 45.degree. (i.e., 50.degree.-5.degree.), but the
typical beamwidth of each antenna sub-aperture is only 12.degree..
Under such a system, the UAV gateway antenna system includes four
(4) beams each of beamwidth 12.degree. to cover a radial angular
region of 45.degree.. However, the exemplary antenna fixture design
(similar to that of FIG. 2.1) only has one sub-aperture antenna to
cover the 45.degree. radial angular range. Accordingly, in one such
variant, the antenna subsystem creates four (4) fixed beams using
beam forming techniques with the sub-aperture antenna unit. In
other words, the beam forming can be performed in only one
direction along the radial axis. The four (4) beams can be fixed
beams and the UAV communications payload will choose one of the
four (4) fixed beams for communications.
[0066] Referring now to FIG. 2.2, an alternative embodiment of a
UAV gateway antenna system sub-aperture 250 is shown and described
in detail. In one exemplary embodiment, the sub-aperture comprises
antenna elements 252 spaced by a half wavelength along the length
of the sub-aperture as shown in FIG. 2.2 where K antenna elements
are shown. The K antennas elements 252 of the sub-aperture 250
shown in FIG. 2.2 may be phased using four (4) different set of K
phases applied to the K elements. Each set of K phases will create
a different beam pointing to one of four (4) different possible
beam positions spaced at, in one exemplary embodiment, 12.degree.
spacings. The software in the modem sub-system of the UAV
communications payload will choose one of the four (4) possible
beams and instruct the sub-aperture circuitry to turn the
corresponding beam on by using the appropriate set of eight (8)
phases from among the four (4) sets.
[0067] While the foregoing discussion contemplates two different
antenna fixtures (i.e., one to form beams toward the user
terminals, and the other to form beams toward the gateways), it is
appreciated that various other configurations will be made readily
apparent to those of ordinary skill in the related arts, given the
contents of the present disclosure. For example, various ones of
the foregoing components and/or functions may be combined into a
single fixture, or alternatively may be distributed across a
greater number of fixtures.
Exemplary Scheme for Power Control to Minimize UAV Power
Usage--
[0068] The power amplifier (PA) power of the UAV gateway and user
terminals transmitters are, in an exemplary configuration)
configured to compensate for rain/atmospheric fade. In one
exemplary embodiment, weather conditions will be provided to the
UAV via weather data transmissions from the gateway(s).
Alternatively, the weather conditions may be determined by the UAV
itself. It is appreciated that rain fade conditions may also be
determined by the UAV based on direct signal measurement, however
alternative implementations may consider information from other
sources. For instance, the UAV can include a pulse-Doppler radar
subsystem (not shown) that provides information regarding
rain/atmospheric fade to the processor/routing subsystem (308, FIG.
3) in order for the PA of the UAV gateway and user terminal
transmitters to control power to individual ones of the transmitted
beams. Those of ordinary skill in the related arts will appreciate
that in clear sky conditions, the PA power can be reduced by as
much as 10 dB or more depending on the frequency band. In one
exemplary embodiment, the UAV communications payload system
incorporates dynamic power control based on measured received SINR,
other quality measurements, and/or other network considerations.
For instance, under clear sky conditions the UAV can be expected to
have an optimal SINR based on calibration and measurements. As SINR
is reduced due to e.g., rain fade, then the communications payload
system will increase the transmit power toward the user terminals
or gateways that are experiencing rain fade. Typically, only part
of the UAV's coverage area may be impacted by rain fade. Therefore,
the UAV can selectively increase power on the specific UAV user
terminal beams that are in rain conditions to optimize its total
power consumption without adversely affecting coverage. By
intelligently managing power consumption, the average power usage
of the UAV communications payload will be significantly less than
the peak power usage (i.e., only where all beams are in rain fade
will the UAV require its peak consumption).
Exemplary UAV Modem and Beam Switching Apparatus--
[0069] As discussed previously herein, FIG. 3 shows the high level
hardware block diagram of an exemplary configuration of a radio
system 300 that communicates with the gateways and manages beam
formation (e.g., switching beams toward gateways, etc.). In the
illustrated embodiment, there are N possible UAV beams toward the
gateways. Only one of the N beams will be transmitting to a
specific gateway (as shown in FIG. 3). The remaining transmitters
are off. As can be seen in FIG. 3, all of the receivers that are
attached to the N UAV gateway antenna sub-apertures are on and
monitoring received signals. In one embodiment, the UAV gateway
modems can receive signals on their respective beams to measure a
signal quality metric such as SINR. The modems send the measured
SINRs to the processor unit subsystem 308. The processor subsystem
308 will compare the measured SINRs from different
sub-apertures/beams and will, based on relative SINR values,
determine if the primary UAV gateway beam should be switched to a
different UAV gateway beam/antenna sub-aperture (or the "candidate
beam"). In the present context, the term "UAV primary gateway beam"
refers without limitation to the UAV gateway beam/antenna
sub-aperture providing coverage to a gateway.
[0070] If a switch is necessary, then the processor configures the
modems corresponding to the two beams (both the candidate beam, as
well as the primary beam) to execute a switch, and informs the
gateway as to the beam switching event, the new beam, and the time
the beam will be switched. Once the beam toward a given gateway is
switched, then the processor/router sub-system 308 can resume
normal operation. As shown in FIG. 3, the processor/router
sub-system 308 can route packets received from the modems 306
serving the user terminal beams to the modem 310 that is connected
to the new UAV primary gateway beam.
Exemplary Terminal Antenna and Gateway Antenna Beam Steering Toward
UAV--
[0071] At high frequencies such as 28 GHz and 47 GHz (e.g., as
recommended by ITU for HAPS (High Altitude Platforms)), high user
terminal and gateway antenna gains are needed to achieve high data
rates in the presence of rain fade. In order to provide such high
gain, the beamwidth of the antennas could be as low as a few
degrees. Unfortunately, the angle subtended from the user terminal
location to the circle around which the UAV cruises at altitude is
much larger than such beamwidths of the user terminal antennas.
Accordingly, in one exemplary embodiment of the present disclosure,
the user terminal antenna steers its beam to track the movement of
the UAV. Since a UAV may have a variety of different movement
patterns, the beam steering should provide elevation angle as well
as azimuth angle with respect to the UAV (i.e. in at least two
axes).
[0072] Those of ordinary skill will appreciate that user terminals
may use electronic beam forming in both elevation and azimuth axes,
electronic beam steering in one axis and mechanical steering in the
other axis, or mechanical beam steering in both axes. Various beam
steering systems are associated with different cost considerations.
For example, since the rate at which the user terminals must steer
their beams may be rather low, mechanical beam steering may be
feasible with a small motor. Other implementations which require
faster steering, may be based on electrical beam forming, etc.
[0073] In some embodiments, beam steering may be done as a
combination of multiple techniques. For example, a user terminal or
gateway modem measures SINR, or some other signal quality measure,
using, for example, the preambles preceding packets. An antenna
steering mechanism makes small perturbations to the antenna beam
position and measures SINR from these preambles. Using the measured
SINRs at different beam perturbations, the beam steering algorithm
chooses the best beam position from among the measured positions.
The beam perturbation and adjustment process continuously adjusts
the beam position. Other information such as GPS based position of
the UAV, the heading of the UAV, and/or the UAV's roll/pitch
measured using gyroscope/accelerometer, will be periodically sent
to the user terminal and gateways and may also assist in steering
the antenna beams.
Exemplary Phased Array Approach to UAV Beam Forming--
[0074] In one exemplary embodiment, the antenna fixture 200 of FIG.
2.1, requires one sub-aperture 204 per beam, and creates a fixed
beam forming system where the beams are not actively steered. The
main advantage of fixed beam forming scheme is its simplicity from
a hardware and software perspective. For example, and referring now
to FIG. 5, the baseband circuitry 500 for forming M beams toward M
different terminals is illustrated. The baseband circuitry of FIG.
5 uses a phased array approach to dynamically form multiple beams
toward M different terminals. Signals to be transmitted to the M
different terminals each may come from a different modem. N antenna
elements are used to form beams toward M terminals. The beam toward
the terminal labeled j is formed by multiplying the signal destined
to user j by N coefficient C.sub.j1, . . . C.sub.jN, and sending
results to the N antenna elements. The coefficients C.sub.j1, . . .
C.sub.jN determine the shape of the beam that is formed toward the
j-th terminal. To form all M beams, the coefficients that are sent
to each antenna element corresponding to different terminals are
summed, up-converted, amplified, and applied to the corresponding
antenna element as shown in FIG. 5. Other methods for implementing
a phased array approach would be readily understood by one of
ordinary skill, given the contents of the present disclosure.
Exemplary Inter-Gateway Traffic Routing with Multiple
Gateways--
[0075] FIG. 4 shows a block diagram of the system 400 that routes
traffic from the UAV (via the communications payload 402) to the
gateway(s) 404 and vice versa. The network comprises a number of
gateways 404 that communicate with the UAV Communications Payload
(UCP). The gateways are connected via a wireline or microwave
backhaul to a Core Network Element (CNE) 406. The CNE is a router
that connects the UAV network with the rest of the internet 408.
The CNE has a pool of IP addresses (typically an IP subnet) from
which it can allocate IP addresses for individual user terminals.
The CNE routes all data traffic to and from the UAV network and the
internet.
[0076] As the UAV moves, the signal quality of the UAV radio links
to the gateways will change due to UAV roll and movements and/or
due to rain fade, atmospheric effects, etc. Generally, the network
deployment is configured so as to ensure that at least one gateway
will be in radio contact with the UAV at all times. The gateways
maintain IP tunnels with the CNE and also periodically notifies the
CNE of the quality of their link with the UAV.
[0077] Data arriving from a user terminal at the UCP 402 will be
distributed across all the gateways 404 associated with the user's
coverage. The gateways in turn send the IP packets on to the CNE
406 via the backhaul and IP tunnels. For data coming from the
internet for the pool of IP addresses assigned to UAV network, the
CNE uses multi-path routing techniques to distribute the IP packets
across the different gateways. The multi-path IP routing will take
into account signal strength of each gateway corresponding to a
respective UAV and accordingly distribute the data so as to ensure
delivery.
[0078] It will be recognized that while certain aspects of the
disclosure are described in terms of a specific sequence of steps
of a method, these descriptions are only illustrative of the
broader methods of the disclosure, and may be modified as required
by the particular application. Certain steps may be rendered
unnecessary or optional under certain circumstances. Additionally,
certain steps or functionality may be added to the disclosed
embodiments, or the order of performance of two or more steps
permuted. All such variations are considered to be encompassed
within the disclosure disclosed and claimed herein.
[0079] While the above detailed description has shown, described,
and pointed out novel features of the disclosure as applied to
various embodiments, it will be understood that various omissions,
substitutions, and changes in the form and details of the device or
process illustrated may be made by those skilled in the art without
departing from the disclosure. This description is in no way meant
to be limiting, but rather should be taken as illustrative of the
general principles of the disclosure. The scope of the disclosure
should be determined with reference to the claims.
* * * * *