U.S. patent application number 16/707010 was filed with the patent office on 2020-05-07 for maintaining contiguous ground coverage with high altitude platforms.
The applicant listed for this patent is LOON LLC. Invention is credited to Cyrus Behroozi.
Application Number | 20200145095 16/707010 |
Document ID | / |
Family ID | 53403487 |
Filed Date | 2020-05-07 |
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United States Patent
Application |
20200145095 |
Kind Code |
A1 |
Behroozi; Cyrus |
May 7, 2020 |
MAINTAINING CONTIGUOUS GROUND COVERAGE WITH HIGH ALTITUDE
PLATFORMS
Abstract
Example methods and systems for adjusting the beam width of
radio frequency (RF) signals for purposes of balloon-to-ground
communication are described. One example method includes
determining, based on respective locations of a plurality of
balloons and areas covered by respective ground-facing
communication beams of the balloons, a contiguous ground coverage
area served by the plurality of balloons, where the communication
beam of a balloon defines a corresponding individual coverage area
within the ground coverage area, determining a change in position
of at least one of the balloons, based on the change in position of
the at least one balloon, determining an adjustment to a first of
the individual coverage areas in an effort to maintain the
contiguous ground coverage area after the change in position of at
least one of the balloons, and adjusting a width of the
ground-facing communication beam of the balloon corresponding to
the first individual coverage area in order to make the determined
adjustment to the first individual coverage area.
Inventors: |
Behroozi; Cyrus; (Menlo
Park, CA) |
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Applicant: |
Name |
City |
State |
Country |
Type |
LOON LLC |
Mountain View |
CA |
US |
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|
Family ID: |
53403487 |
Appl. No.: |
16/707010 |
Filed: |
December 9, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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16277014 |
Feb 15, 2019 |
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16707010 |
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15810539 |
Nov 13, 2017 |
10230453 |
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16277014 |
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14132584 |
Dec 18, 2013 |
9847828 |
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15810539 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04B 7/2606 20130101;
H01Q 1/28 20130101; H04B 7/18506 20130101; H04W 16/26 20130101;
H04W 72/046 20130101; H04W 64/003 20130101; H04B 7/18504
20130101 |
International
Class: |
H04B 7/185 20060101
H04B007/185; H01Q 1/28 20060101 H01Q001/28; H04B 7/26 20060101
H04B007/26; H04W 16/26 20060101 H04W016/26; H04W 64/00 20060101
H04W064/00; H04W 72/04 20060101 H04W072/04 |
Claims
1. A signal routing method comprising: determining, by one or more
processors in a communication network, state information for a
plurality of high altitude platforms forming at least part of the
communication network, the state information including one or more
of location data for each of the plurality of high altitude
platforms, communication link information or meteorological
information; determining, by the one or more processors according
to the state information, one or more routing paths for a
communication signal through a subset of the plurality of high
altitude platforms, at least one of the one or more routing paths
is transparent without signal conversion; selecting, by the one or
more processors, a transparent routing path from among the one or
more routing paths; and transmitting the communication signal to a
receiver device via the transparent routing path.
2. The signal routing method of claim 1, wherein the transparent
routing path comprises a plurality of free-space optical links
between the subset of high altitude platforms.
3. The signal routing method of claim 1, wherein determining the
one or more routing paths includes identifying adaptive routing
between first and second high altitude platforms of the plurality
of high altitude platforms, where a lightpath between the first and
second high altitude platforms is determined and set-up when a
connection is needed and released at a later time.
4. The signal routing method of claim 3, wherein the lightpath is
determined dynamically depending upon at least one of a current
state, a past state, or a predicted state of the plurality of high
altitude platforms.
5. The signal routing method of claim 1, wherein determining the
one or more routing paths includes evaluating which paths implement
wavelength division multiplexing.
6. The signal routing method of claim 1, wherein selecting the
transparent routing path includes assigning a same wavelength for
all optical links on the transparent routing path.
7. The signal routing method of claim 1, wherein one or more of the
plurality of high altitude platforms comprises a balloon.
8. A system comprising: a plurality of high altitude platforms
forming at least part of a wireless communication network; and a
control system including one or more processors, the one or more
processors being configured to: determine state information for the
plurality of high altitude platforms, the state information
including one or more of location data for each of the plurality of
high altitude platforms, communication link information or
meteorological information; determine, according to the state
information, one or more routing paths for a communication signal
through a subset of the plurality of high altitude platforms, at
least one of the one or more routing paths is transparent without
signal conversion; select a transparent routing path from among the
one or more routing paths; and inform all high altitude platforms
along the transparent routing path of the selection.
9. The system of claim 8, wherein one or more of the high altitude
platforms along the transparent routing path comprise one or more
lighter-than-air platforms.
10. The system of claim 9, wherein the one or more lighter-than-air
platforms comprise one or more balloons.
11. The system of claim 8, wherein the transparent routing path
comprises a plurality of free-space optical links between the
subset of high altitude platforms.
12. The system of claim 8, wherein the determination of the one or
more routing paths includes identification of adaptive routing
between first and second high altitude platforms of the plurality
of high altitude platforms, where a lightpath between the first and
second high altitude platforms is determined and set-up when a
connection is needed and released at a later time.
13. The system of claim 12, wherein the lightpath is determined
dynamically depending upon at least one of a current state, a past
state, or a predicted state of the plurality of high altitude
platforms.
14. The system of claim 8, wherein determination of the one or more
routing paths includes evaluation of which paths implement
wavelength division multiplexing.
15. The system of claim 8, wherein selection of the transparent
routing path includes assignment of a same wavelength for all
optical links on the transparent routing path.
16. A non-transitory computer readable medium having instructions
stored therein, the instructions, when executed by a computing
system, cause the computing system to perform a signal routing
method comprising: determining state information for a plurality of
high altitude platforms forming at least part of the communication
network, the state information including one or more of location
data for each of the plurality of high altitude platforms,
communication link information or meteorological information;
determining, according to the state information, one or more
routing paths for a communication signal through a subset of the
plurality of high altitude platforms, at least one of the one or
more routing paths is transparent without signal conversion;
selecting a transparent routing path from among the one or more
routing paths; and transmitting the communication signal to a
receiver device via the transparent routing path.
17. The non-transitory computer readable medium of claim 16,
wherein determining the one or more routing paths includes
identifying adaptive routing between first and second high altitude
platforms of the plurality of high altitude platforms, where a
lightpath between the first and second high altitude platforms is
determined and set-up when a connection is needed and released at a
later time.
18. The non-transitory computer readable medium of claim 17,
wherein the lightpath is determined dynamically depending upon at
least one of a current state, a past state, or a predicted state of
the plurality of high altitude platforms.
19. The non-transitory computer readable medium of claim 16,
wherein determining the one or more routing paths includes
evaluating which paths implement wavelength division
multiplexing.
20. The non-transitory computer readable medium of claim 16,
wherein selecting the transparent routing path includes assigning a
same wavelength for all optical links on the transparent routing
path.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] The present application is a divisional of U.S. patent
application Ser. No. 16/277,014, filed on Feb. 15, 2019, which is a
continuation of U.S. patent application Ser. No. 15/810,539 filed
on Nov. 13, 2017, which application is a continuation of U.S.
patent application Ser. No. 14/132,584 filed on Dec. 18, 2013, now
U.S. Pat. No. 9,847,828, issued on Dec. 19, 2017, the contents of
which are incorporated herein by reference, as if fully set forth
in this description.
BACKGROUND
[0002] Computing devices such as personal computers, laptop
computers, tablet computers, cellular phones, and countless types
of Internet-capable devices are increasingly prevalent in numerous
aspects of modern life. As such, the demand for data connectivity
via the Internet, cellular data networks, and other such networks,
is growing. However, there are many areas of the world where data
connectivity is still unavailable, or if available, is unreliable
and/or costly. Accordingly, additional network infrastructure is
desirable.
SUMMARY
[0003] Example methods and systems for adjusting the beam width of
radio frequency (RF) signals for purposes of balloon-to-ground
communication are described. An example balloon may be capable of
transmitting ground-facing communication signals with different
beam widths in order to cover different areas on the ground. An
example group of balloons, such as balloons operating as part of a
balloon network, may provide service to a contiguous coverage area
on the ground. Movements of one or more of the balloons may be
determined that might cause a gap in coverage. In order to maintain
contiguous coverage, the beam width of one of the balloons may be
adjusted to change the individual coverage area of the balloon.
[0004] In one example, a method is provided that includes
determining, based on respective locations of a plurality of
balloons and areas covered by respective ground-facing
communication beams of the balloons, a contiguous ground coverage
area served by the plurality of balloons, where the communication
beam of a balloon defines a corresponding individual coverage area
within the ground coverage area, determining a change in position
of at least one of the balloons, based on the change in position of
the at least one balloon, determining an adjustment to a first of
the individual coverage areas in an effort to maintain the
contiguous ground coverage area after the change in position of at
least one of the balloons, and adjusting a width of the
ground-facing communication beam of the balloon corresponding to
the first individual coverage area in order to make the determined
adjustment to the first individual coverage area.
[0005] In another example, a system is provided that includes a
plurality of balloons, and a control system configured to
determine, based on respective locations of the balloons and areas
covered by respective ground-facing communication beams of the
balloons, a contiguous ground coverage area served by the balloons,
where the communication beam of a balloon defines a corresponding
individual coverage area within the ground coverage area, determine
a change in position of at least one of the balloons, based on the
change in position of the at least one balloon, determine an
adjustment to a first of the individual coverage areas in an effort
to maintain the contiguous ground coverage area after the change in
position of at least one of the balloons, and provide instructions
to adjust a width of the ground-facing communication beam of the
balloon corresponding to the first individual coverage area in
order to make the determined adjustment to the first individual
coverage area.
[0006] In a further example, a non-transitory computer readable
medium having stored therein instructions that when executed by a
computing system, cause the computing system to perform functions
is disclosed. The functions may include determining, based on
respective locations of a plurality of balloons and areas covered
by respective ground-facing communication beams of the balloons, a
contiguous ground coverage area served by the plurality of
balloons, where the communication beam of a balloon defines a
corresponding individual coverage area within the ground coverage
area, determining a change in position of at least one of the
balloons, based on the change in position of the at least one
balloon, determining an adjustment to a first of the individual
coverage areas in an effort to maintain the contiguous ground
coverage area after the change in position of at least one of the
balloons, and adjusting a width of the ground-facing communication
beam of the balloon corresponding to the first individual coverage
area in order to make the determined adjustment to the first
individual coverage area.
[0007] In yet another example, a system may include means for
determining, based on respective locations of a plurality of
balloons and areas covered by respective ground-facing
communication beams of the balloons, a contiguous ground coverage
area served by the plurality of balloons, where the communication
beam of a balloon defines a corresponding individual coverage area
within the ground coverage area, means for determining a change in
position of at least one of the balloons, based on the change in
position of the at least one balloon, means for determining an
adjustment to a first of the individual coverage areas in an effort
to maintain the contiguous ground coverage area after the change in
position of at least one of the balloons, and means for adjusting a
width of the ground-facing communication beam of the balloon
corresponding to the first individual coverage area in order to
make the determined adjustment to the first individual coverage
area.
[0008] These as well as other aspects, advantages, and
alternatives, will become apparent to those of ordinary skill in
the art by reading the following detailed description, with
reference where appropriate to the accompanying figures.
BRIEF DESCRIPTION OF THE FIGURES
[0009] FIG. 1 is a block diagram illustrating an example balloon
network.
[0010] FIG. 2 is a block diagram illustrating an example
balloon-network control system.
[0011] FIG. 3 shows a high-altitude balloon according to an example
embodiment.
[0012] FIG. 4 is a simplified block diagram illustrating a balloon
network that includes super-nodes and sub-nodes, according to an
example embodiment.
[0013] FIG. 5A shows a balloon and a communication signal with a
first beam width, according to an example embodiment.
[0014] FIG. 5B shows a balloon and a communication signal with a
second beam width, according to an example embodiment.
[0015] FIG. 6 is a block diagram of a method, according to an
example embodiment.
[0016] FIG. 7A illustrates a top view of a configuration of three
balloons and corresponding communication beams, according to an
example embodiment.
[0017] FIG. 7B illustrates a top view of another configuration of
three balloons and corresponding communication beams, according to
an example embodiment.
[0018] FIG. 7C illustrates a top view of yet another configuration
of three balloons and corresponding communication beams, according
to an example embodiment.
[0019] FIG. 7D illustrates a top view of a further configuration of
three balloons and corresponding communication beams, according to
an example embodiment.
[0020] FIG. 7E illustrates a top view of an additional
configuration of three balloons and corresponding communication
beams, according to an example embodiment.
DETAILED DESCRIPTION
I. Overview
[0021] Examples of methods and systems are described herein. It
should be understood that the words "example" and "exemplary" are
used herein to mean "serving as an example, instance, or
illustration." Any embodiment or feature described herein as
"exemplary" is not necessarily to be construed as preferred or
advantageous over other embodiments or features. The example or
exemplary embodiments described herein are not meant to be
limiting. It will be readily understood that certain aspects of the
disclosed systems and methods can be arranged and combined in a
wide variety of different configurations, all of which are
contemplated herein.
[0022] Furthermore, the particular arrangements shown in the
Figures should not be viewed as limiting. It should be understood
that other embodiments may include more or less of each element
shown in a given Figure. Further, some of the illustrated elements
may be combined or omitted. Yet further, an exemplary embodiment
may include elements that are not illustrated in the Figures.
[0023] Example embodiments relate to an aerial communication
network using a plurality of balloons with communication equipment
to facilitate wireless communication among the balloons and with
ground-based stations and/or other ground subscribers. Balloons can
be formed of an envelope supporting a payload with a power supply,
data storage, and one or more transceivers for wirelessly
communicating information to other members of the balloon network
and/or to wireless stations located on the ground. To communicate
with ground-based stations and/or other ground subscribers while
aloft, the balloons can be equipped with one or more radio
frequency (RF) antennas mounted to the balloon payload so as to be
ground-facing.
[0024] In particular, one or more transceivers may be used by a
balloon to transmit and/or receive communication data to and/or
from ground-based stations and/or other ground subscribers located
within a certain area underneath the balloon at ground level. In
some examples, a group of neighboring balloons may provide
contiguous coverage at ground level. For instance, service may be
provided from at least one balloon within a network of balloons to
subscribers located on the ground anywhere within a region.
[0025] In general, the beam width of a ground-facing RF
communication signal may be inversely proportional to the strength
of the signal at ground level. A narrowly focused beam (e.g., from
a high-gain antenna on a balloon) may provide a stronger signal,
while a broader beam (e.g., from a low-gain antenna on a balloon)
may spread out the power over a larger area and therefore may not
provide as strong a signal. Accordingly, in some examples, a group
of balloons may provide coverage over an area with minimal overlap
between areas covered by neighboring balloons in order to provide a
strong signal (and/or a signal with a high signal-to-noise ratio)
to ground-based subscribers.
[0026] In some instances, one or more balloons within a network may
change position in a way that may create a gap in coverage at
ground level. For example, one or more of the balloons could change
horizontal (latitudinal and/or longitudinal) position and/or
altitude. A balloon may change position based on factors partially
or completely outside the control of the balloon network (e.g.,
wind) and/or may be controlled to change position based on fleet
planning algorithms which may be used to position balloons within
the network. The change(s) in position may change the areas covered
by each of the balloons on the ground based on the current beam
widths of ground-facing communication beams in use by the balloons.
In some instances, a determination may be made (either before a
change in position occurs, during the change in position, or after
the change in position) that a gap may occur in the ground coverage
provided by the balloon network.
[0027] In such circumstances, the beam width of a ground-facing
communication signal from one or more balloons may be adjusted in
an effort to maintain contiguous coverage on the ground. For
instance, if neighboring balloons travel far away from a particular
balloon, the balloon may increase its beam width to increase its
coverage area (e.g., to provide coverage to areas that were
previously covered by other balloons). In other examples,
neighboring balloons may travel close to a particular balloon, such
as when each of the balloons is assigned to help provide coverage
to a highly populated area (e.g., a sporting event). In such an
instance, the particular balloon may decrease the beam width of its
ground-facing communication signal to decrease the size of its
coverage area and provide a stronger signal to a smaller area on
the ground, for example.
[0028] A balloon may be equipped to adjust the beam width of a
ground-facing RF communication beam in different ways. In one
example, a beam width may be adjusted by selecting from two or more
discrete antennas, each capable of transmitting a signal with a
different beam width. For instance, a balloon may be equipped with
two different RF antennas: one high-gain antenna for transmitting
narrow RF beams and one low-gain antenna for transmitting broader
RF beams. In further examples, a balloon may be equipped with three
or more different antennas, each capable of transmitting an RF
signal with a different beam width. In other examples, the beam
width of a balloon may be continuously adjustable, such as by
adjusting the spacing between a radiator and a ground-facing
reflector that may operate to reflect a communication beam toward
the ground.
[0029] In additional examples, a balloon network may service ground
subscribers with a level of demand that varies based on location
(e.g., a highly populated area may have greater demand than an area
with fewer people). In such examples, the beam widths of one or
more balloons may be controlled and/or adjusted in order to provide
a certain amount of coverage to particular areas on the ground
based on demand level. For instance, each balloon may have a
limited capacity of data that it can transmit to ground subscribers
(e.g., 10 MB/s). One or more balloons covering an area with a
certain demand level (e.g., 100 MB/s) may change position so that
the balloons may no longer provide enough coverage to satisfy the
demand level using the current beam widths. In such circumstances,
one or more balloons may adjust the beam widths of their
ground-facing communication signals in order to satisfy the demand
for coverage at ground level.
[0030] Example systems and methods therefore may allow for RF
communication from a group of balloons to ground-based stations
and/or other ground subscribers. A balloon may adjust the beam
width of a ground-facing communication beam based on changes in
position of one or more of the balloons.
II. Example Balloon Networks
[0031] In order that the balloons can provide a reliable data
network in the stratosphere, where winds may affect the locations
of the various balloons in an asymmetrical manner, the balloons in
an exemplary network may be configured move latitudinally and/or
longitudinally relative to one another by adjusting their
respective altitudes, such that the wind carries the respective
balloons to the respectively desired locations.
[0032] Further, in an exemplary balloon network, the balloons may
communicate with one another using free-space optical
communications. For instance, the balloons may be configured for
optical communications using ultrabright LEDs or possibly lasers
for optical signaling (although regulations for laser
communications may restrict laser usage). In addition, the balloons
may communicate with ground-based station(s) using radio-frequency
(RF) communications.
[0033] In some embodiments, a high-altitude-balloon network may be
homogenous. More specifically, in a homogenous
high-altitude-balloon network, each balloon is configured to
communicate with nearby balloons via free-space optical links.
Further, some or all of the balloons in such a network, may also be
configured communicate with ground-based station(s) using RF
communications. (Note that in some embodiments, the balloons may be
homogenous in so far as each balloon is configured for free-space
optical communication with other balloons, but heterogeneous with
regard to RF communications with ground-based stations.)
[0034] In other embodiments, a high-altitude-balloon network may be
heterogeneous, and thus may include two or more different types of
balloons. For example, some balloons may be configured as
super-nodes, while other balloons may be configured as sub-nodes.
(Note also that some balloons may be configured to function as both
a super-node and a sub-node.)
[0035] In such a configuration, the super-node balloons may be
configured to communicate with nearby super-node balloons via
free-space optical links. However, the sub-node balloons may not be
configured for free-space optical communication, and may instead be
configured for, e.g., RF communications. Accordingly, a super-node
may be further configured to communicate with nearby sub-nodes
using RF communications. The sub-nodes may accordingly relay
communications from the super-nodes to ground-based station(s)
using RF communications. Configured as such, the super-nodes may
collectively function as backhaul for the balloon network, while
the sub-nodes function to relay communications from the super-nodes
to ground-based stations.
[0036] FIG. 1 is a simplified block diagram illustrating a balloon
network 100, according to an exemplary embodiment. As shown,
balloon network 100 includes balloons 102A to 102E, which are
configured to communicate with one another via free-space optical
links 104. Configured as such, balloons 102A to 102E may
collectively function as a mesh network for packet-data
communications. Further, balloons 102A to 102D may be configured
for RF communications with ground-based stations 106 via RF links
108.
[0037] In an exemplary embodiment, balloons 102A to 102E are
high-altitude balloons, which are deployed in the stratosphere. At
moderate latitudes, the stratosphere includes altitudes between
approximately 10 kilometers (km) and 50 km altitude above the
surface. At the poles, the stratosphere starts at an altitude of
approximately 8 km. In an exemplary embodiment, high-altitude
balloons may be generally configured to operate in an altitude
range within the stratosphere that has lower winds (e.g., between 5
and 20 miles per hour (mph)).
[0038] More specifically, in a high-altitude-balloon network,
balloons 102A to 102E may generally be configured to operate at
altitudes between 17 km and 22 km (although other altitudes are
possible). This altitude range may be advantageous for several
reasons. In particular, this layer of the stratosphere generally
has mild wind and turbulence (e.g., winds between 5 and 20 miles
per hour (mph)). Further, while the winds between 17 km and 22 km
may vary with latitude and by season, the variations can be modeled
in a reasonably accurate manner. Additionally, altitudes above 17
km are typically above the maximum flight level designated for
commercial air traffic. Therefore, interference with commercial
flights is not a concern when balloons are deployed between 17 km
and 22 km.
[0039] To transmit data to another balloon, a given balloon 102A to
102E may be configured to transmit an optical signal via an optical
link 104. In an exemplary embodiment, a given balloon 102A to 102E
may use one or more high-power light-emitting diodes (LEDs) to
transmit an optical signal. Alternatively, some or all of balloons
102A to 102E may include laser systems for free-space optical
communications over optical links 104. Other types of free-space
optical communication are possible. Further, In order to receive an
optical signal from another balloon via an optical link 104, a
given balloon 102A to 102E may include one or more optical
receivers. Additional details of balloons implementations are
discussed in greater detail below, with reference to FIG. 3.
[0040] In a further aspect, balloons 102A to 102D may utilize one
or more of various different RF air-interface protocols for
communication ground-based stations 106 via RF links 108. For
instance, some or all of balloons 102A to 102D may be configured to
communicate with ground-based stations 106 using protocols
described in IEEE 802.11 (including any of the IEEE 802.11
revisions), various cellular protocols such as GSM, CDMA, UMTS,
EV-DO, WiMAX, and/or LTE, and/or one or more propriety protocols
developed for balloon-to-ground RF communication, among other
possibilities.
[0041] In a further aspect, there may scenarios where RF links 108
do not provide a desired link capacity for balloon-to-ground
communications. For instance, increased capacity may be desirable
to provide backhaul links from a ground-based gateway, and in other
scenarios as well. Accordingly, an exemplary network may also
include downlink balloons, which provide a high-capacity
air-to-ground link.
[0042] For example, in balloon network 100, balloon 102E is
configured as a downlink balloon. Like other balloons in an
exemplary network, a downlink balloon 102E may be operable for
optical communication with other balloons via optical links 104.
However, a downlink balloon 102E may also be configured for
free-space optical communication with a ground-based station 112
via an optical link 110. Optical link 110 may therefore serve as a
high-capacity link (as compared to an RF link 108) between the
balloon network 100 and a ground-based station 108.
[0043] Note that in some implementations, a downlink balloon 102E
may additionally be operable for RF communication with ground-based
stations 106. In other cases, a downlink balloon 102E may only use
an optical link for balloon-to-ground communications. Further,
while the arrangement shown in FIG. 1 includes just one downlink
balloon 102E, an exemplary balloon network can also include
multiple downlink balloons. On the other hand, a balloon network
can also be implemented without any downlink balloons.
[0044] In other implementations, a downlink balloon may be equipped
with a specialized, high-bandwidth RF communication system for
balloon-to-ground communications, instead of or in addition to a
free-space optical communication system. The high-bandwidth RF
communication system may take the form of an ultra-wideband system,
which provides an RF link with substantially the same capacity as
the optical links 104. Other forms are also possible.
[0045] Ground-based stations, such as ground-based stations 106
and/or 108, may take various forms. Generally, a ground-based
station may include components such as transceivers, transmitters,
and/or receivers for communication via RF links and/or optical
links with a balloon network. Further, a ground-based station may
use various air-interface protocols in order communicate with a
balloon 102A to 102E over an RF link 108. As such, a ground-based
station 106 may be configured as an access points via which various
devices can connect to balloon network 100. Ground-based stations
106 may have other configurations and/or serve other purposes
without departing from the scope of the invention.
[0046] Further, some ground-based stations, such as ground-based
station 108, may be configured as gateways between balloon network
100 and one or more other networks. Such a ground-based station 108
may thus serve as an interface between the balloon network and the
Internet, a cellular service provider's network, and/or other types
of networks. Variations on this configuration and other
configurations of a ground-based station 108 are also possible.
[0047] A. Mesh-Network Functionality
[0048] As noted, balloons 102A to 102E may collectively function as
a mesh network. More specifically, since balloons 102A to 102E may
communicate with one another using free-space optical links, the
balloons may collectively function as a free-space optical mesh
network.
[0049] In a mesh-network configuration, each balloon 102A to 102E
may function as a node of the mesh network, which is operable to
receive data direct to it and to route data to other balloons. As
such, data may be routed from a source balloon to a destination
balloon by determining an appropriate sequence of optical links
between the source balloon and the destination balloon. These
optical links may be collectively referred to as a "lightpath" for
the connection between the source and destination balloons.
Further, each of the optical links may be referred to as a "hop" on
the lightpath.
[0050] Further, in order to operate as a mesh network, balloons
102A to 102E may employ various routing techniques and self-healing
algorithms. In some embodiments, a balloon network 100 may employ
adaptive or dynamic routing, where a lightpath between a source and
destination balloon is determined and set-up when the connection is
needed, and released at a later time. Further, when adaptive
routing is used, the lightpath may be determined dynamically
depending upon the current state, past state, and/or predicted
state of the balloon network.
[0051] In addition, the network topology may change as the balloons
102A to 102E move relative to one another and/or relative to the
ground. Accordingly, an exemplary balloon network 100 may apply a
mesh protocol to update the state of the network as the topology of
the network changes. For example, to address the mobility of the
balloons 102A to 102E, balloon network 100 may employ and/or adapt
various techniques that are employed in mobile ad hoc networks
(MANETs). Other examples are possible as well.
[0052] In some implementations, a balloon network 100 may be
configured as a transparent mesh network. More specifically, in a
transparent balloon network, the balloons may include components
for physical switching that is entirely optical, without any
electrical involved in physical routing of optical signals. Thus,
in a transparent configuration with optical switching, signals
travel through a multi-hop lightpath that is entirely optical.
[0053] In other implementations, the balloon network 100 may
implement a free-space optical mesh network that is opaque. In an
opaque configuration, some or all balloons 102A to 102E may
implement optical-electrical-optical (OEO) switching. For example,
some or all balloons may include optical cross-connects (OXCs) for
OEO conversion of optical signals. Other opaque configurations are
also possible.
[0054] In a further aspect, balloons in an exemplary balloon
network 100 may implement wavelength division multiplexing (WDM),
which may help to increase link capacity. When WDM is implemented
with transparent switching, physical lightpaths through the balloon
network may be subject to the "wavelength continuity constraint."
More specifically, because the switching in a transparent network
is entirely optical, it may be necessary to assign the same
wavelength for all optical links on a given lightpath.
[0055] An opaque configuration, on the other hand, may avoid the
wavelength continuity constraint. In particular, balloons in an
opaque balloon network may include the OEO switching systems
operable for wavelength conversion. As a result, balloons can
convert the wavelength of an optical signal at each hop along a
lightpath.
[0056] Further, various routing algorithms may be employed in an
opaque configuration. For example, to determine a primary lightpath
and/or one or more diverse backup lightpaths for a given
connection, exemplary balloons may apply or consider shortest-path
routing techniques such as Dijkstra's algorithm and k-shortest
path, and/or edge and node-diverse or disjoint routing such as
Suurballe's algorithm, among others. Additionally or alternatively,
techniques for improving QoS may be employed when determining a
lightpath. Other techniques are also possible.
[0057] B. Station-Keeping Functionality
[0058] In an exemplary embodiment, a balloon network 100 may
implement station-keeping functions to help provide a desired
network topology. For example, station-keeping may involve each
balloon 102A to 102E maintaining and/or moving into a certain
position relative to one or more other balloons in the network (and
possibly in a certain position relative to the ground). As part of
this process, each balloon 102A to 102E may implement
station-keeping functions to determine its desired positioning
within the desired topology, and if necessary, to determine how to
move to the desired position.
[0059] The desired topology may vary depending upon the particular
implementation. In some cases, balloons may implement
station-keeping to provide a substantially uniform topology. In
such case, a given balloon 102A to 102E may implement
station-keeping functions to position itself at substantially the
same distance (or within a certain range of distances) from
adjacent balloons in the balloon network 100.
[0060] In other cases, a balloon network 100 may have a non-uniform
topology. For instance, exemplary embodiments may involve
topologies where balloons are distributed more or less densely in
certain areas, for various reasons. As an example, to help meet the
higher bandwidth demands that are typical in urban areas, balloons
may be clustered more densely over urban areas. For similar
reasons, the distribution of balloons may be denser over land than
over large bodies of water. Many other examples of non-uniform
topologies are possible.
[0061] In a further aspect, the topology of an exemplary balloon
network may be dynamic and adaptable. In particular,
station-keeping functionality of exemplary balloons may allow the
balloons to adjust their respective positioning in accordance with
a change in the desired topology of the network. For example, one
or more balloons could move to new positions to increase or
decrease the density of balloons in a given area. Further, in some
embodiments, balloons may be in continuous or nearly continuous
motion, and station-keeping may involve moving balloons so as to
try to meet certain requirements for e.g., coverage in various
areas.
[0062] In some embodiments, a balloon network 100 may employ an
energy function to determine if and/or how balloons should move to
provide a desired topology. In particular, the state of a given
balloon and the states of some or all nearby balloons may be input
to an energy function. The energy function may apply the current
states of the given balloon and the nearby balloons to a desired
network state (e.g., a state corresponding to the desired
topology). A vector indicating a desired movement of the given
balloon may then be determined by determining the gradient of the
energy function. The given balloon may then determine appropriate
actions to take in order to effectuate the desired movement. For
example, a balloon may determine an altitude adjustment or
adjustments such that winds will move the balloon in the desired
manner.
[0063] C. Control of Balloons in a Balloon Network
[0064] In some embodiments, mesh networking and/or station-keeping
functions may be centralized. For example, FIG. 2 is a block
diagram illustrating a balloon-network control system, according to
an exemplary embodiment. In particular, FIG. 2 shows a distributed
control system, which includes a central control system 200 and a
number of regional control-systems 202A to 202B. Such a control
system may be configured to coordinate certain functionality for
balloon network 204, and as such, may be configured to control
and/or coordinate certain functions for balloons 206A to 206I.
[0065] In the illustrated embodiment, central control system 200
may be configured to communicate with balloons 206A to 206I via
number of regional control systems 202A to 202C. These regional
control systems 202A to 202C may be configured to receive
communications and/or aggregate data from balloons in the
respective geographic areas that they cover, and to relay the
communications and/or data to central control system 200. Further,
regional control systems 202A to 202C may be configured to route
communications from central control system 200 to the balloons in
their respective geographic areas. For instance, as shown in FIG.
2, regional control system 202A may relay communications and/or
data between balloons 206A to 206C and central control system 200,
regional control system 202B may relay communications and/or data
between balloons 206D to 206F and central control system 200, and
regional control system 202C may relay communications and/or data
between balloons 206G to 206I and central control system 200.
[0066] In order to facilitate communications between the central
control system 200 and balloons 206A to 206I, certain balloons may
be configured as downlink balloons, which are operable to
communicate with regional control systems 202A to 202C.
Accordingly, each regional control system 202A to 202C may be
configured to communicate with the downlink balloon or balloons in
the respective geographic area it covers. For example, in the
illustrated embodiment, balloons 204A, 204D, and 204H are
configured as downlink balloons. As such, regional control systems
202A to 202C may respectively communicate with balloons 204A, 204D,
and 204H via optical links 206, 208, and 210, respectively.
[0067] In the illustrated configuration, where only some of
balloons 206A to 206I are configured as downlink balloons, the
balloons 206A, 206D, and 206H that are configured as downlink
balloons may function to relay communications from central control
system 200 to other balloons in the balloon network, such as
balloons 206B, 206C, 206E to 206G, and 206I. However, it should be
understood that it in some implementations, it is possible that all
balloons may function as downlink balloons. Further, while FIG. 2
shows multiple balloons configured as downlink balloons, it is also
possible for a balloon network to include only one downlink
balloon.
[0068] Note that a regional control system 202A to 202B may in fact
just be particular type of ground-based station that is configured
to communicate with downlink balloons (e.g., such as ground-based
station 112 of FIG. 1). Thus, while not shown in FIG. 2, the
control system shown in FIG. 2 may be implemented in conjunction
with other types of ground-based stations (e.g., access points,
gateways, etc.).
[0069] In a centralized control arrangement, such as that shown in
FIG. 2, the central control system 200 (and possibly regional
control systems 202A to 202C as well) may coordinate certain
mesh-networking functions for balloon network 204. For example,
balloons 206A to 206I may send the central control system 200
certain state information, which the central control system 200 may
utilize to determine the state of balloon network 204. The state
information from a given balloon may include location data,
optical-link information (e.g., the identity of other balloons with
which the balloon has established an optical link, the bandwidth of
the link, wavelength usage and/or availability on a link, etc.),
wind data collected by the balloon, and/or other types of
information. Accordingly, the central control system 200 may
aggregate state information from some or all the balloons 206A to
206I in order to determine an overall state of the network.
[0070] The overall state of the network may then be used to
coordinate and/or facilitate certain mesh-networking functions such
as determining lightpaths for connections. For example, the central
control system 200 may determine a current topology based on the
aggregate state information from some or all the balloons 206A to
206I. The topology may provide a picture of the current optical
links that are available in balloon network and/or the wavelength
availability on the links. This topology may then be sent to some
or all of the balloons so that a routing technique may be employed
to select appropriate lightpaths (and possibly backup lightpaths)
for communications through the balloon network 204.
[0071] In a further aspect, the central control system 200 (and
possibly regional control systems 202A to 202C as well) may also
coordinate certain station-keeping functions for balloon network
204. For example, the central control system 200 may input state
information that is received from balloons 206A to 206I to an
energy function, which may effectively compare the current topology
of the network to a desired topology, and provide a vector
indicating a direction of movement (if any) for each balloon, such
that the balloons can move towards the desired topology. Further,
the central control system 200 may use altitudinal wind data to
determine respective altitude adjustments that may be initiated to
achieve the movement towards the desired topology. The central
control system 200 may provide and/or support other station-keeping
functions as well.
[0072] As noted, FIG. 2 shows a distributed-control arrangement,
with regional control systems 202A to 202C coordinating
communications between a central control system 200 and a balloon
network 204. Such an arrangement may be useful in a balloon network
that covers a large geographic area. In some embodiments, a
distributed control system may even support a global balloon
network that provides coverage everywhere on earth. Of course, a
distributed-control arrangement may be useful in other scenarios as
well.
[0073] Further, it should be understood that other control-system
arrangements are possible. For instance, some implementations may
involve a distributed control system with additional layers (e.g.,
sub-region systems within the regional control systems, and so on).
Alternatively, control functions may be provided by a single,
centralized, control system, which communicates directly with one
or more downlink balloons.
[0074] In a further aspect, control and coordination of a balloon
network may be shared between a ground-based control system and a
balloon network to varying degrees, depending upon the
implementation. In fact, in some embodiments, there may be no
ground-based control system. In such an embodiment, all network
control and coordination functions may be implemented by the
balloon network itself. For example, certain balloons may be
configured to provide the same or similar functions as central
control system 200 and/or regional control systems 202A to 202C.
Other examples are also possible.
[0075] Furthermore, control and/or coordination of a balloon
network may be de-centralized. For example, each balloon may relay
state information to, and receive state information from, some or
all nearby balloons. Further, each balloon may relay state
information that it receives from a nearby balloon to some or all
nearby balloons. When all balloons do so, each balloon may be able
to individually determine the state of the network. Alternatively,
certain balloons may be designated to aggregate state information
for a given portion of the network. These balloons may then
coordinate with one another to determine the overall state of the
network.
[0076] Further, in some aspects, control of a balloon network may
be partially or entirely localized, such that it is not dependent
on the overall state of the network. For example, individual
balloons may implement station-keeping functions that only consider
nearby balloons. In particular, each balloon may implement an
energy function that takes into account its own state and the
states of nearby balloons. The energy function may be used to
maintain and/or move to a desired position with respect to the
nearby balloons, without necessarily considering the desired
topology of the network as a whole. However, when each balloon
implements such an energy function for station-keeping, the balloon
network as a whole may maintain and/or move towards the desired
topology.
[0077] D. Illustrative Balloon Configurations
[0078] Various types of balloon systems may be incorporated in an
exemplary balloon network. As noted above, an exemplary embodiment
may utilize high-altitude balloons, which typically operate in an
altitude range between 17 km and 22 km. FIG. 3 is a simplified
block diagram illustrating a high-altitude balloon 300, according
to an exemplary embodiment. As shown, the balloon 300 includes an
envelope 302, a skirt 304, a payload 306, and a cut-down system 308
that is attached between the balloon 302 and payload 304.
[0079] The envelope 302 and skirt 304 may take various forms, which
may be currently well-known or yet to be developed. For instance,
the envelope 302 and/or skirt 304 may be made of a highly-flexible
latex material or may be made of a rubber material such as
chloroprene. Other materials are also possible. Further, the shape
and size of the envelope 302 and skirt 304 may vary depending upon
the particular implementation. Additionally, the envelope 302 may
be filled with various different types of gases, such as helium
and/or hydrogen. Other types of gases are possible as well.
[0080] The payload 306 of balloon 300 may include a processor 312
and on-board data storage, such as memory 314. The memory 314 may
take the form of or include a non-transitory computer-readable
medium. The non-transitory computer-readable medium may have
instructions stored thereon, which can be accessed and executed by
the processor 312 in order to carry out the balloon functions
described herein.
[0081] The payload 306 of balloon 300 may also include various
other types of equipment and systems to provide a number of
different functions. For example, payload 306 may include optical
communication system 316, which may transmit optical signals via an
ultra-bright LED system 320, and which may receive optical signals
via an optical-communication receiver 322 (e.g., a photo-diode
receiver system). Further, payload 306 may include an RF
communication system 318, which may transmit and/or receive RF
communications via an antenna system 324. The payload 306 may also
include a power supply 326 to supply power to the various
components of balloon 300.
[0082] Further, payload 306 may include various types of other
systems and sensors 328. For example, payload 306 may include one
or more video and/or still cameras, a GPS system, various motion
sensors (e.g., accelerometers, gyroscopes, and/or compasses),
and/or various sensors for capturing environmental data. Further,
some or all of the components within payload 306 may be implemented
in a radiosonde, which may be operable to measure, e.g., pressure,
altitude, geographical position (latitude and longitude),
temperature, relative humidity, and/or wind speed and/or direction,
among other information.
[0083] As noted, balloon 306 includes an ultra-bright LED system
320 for free-space optical communication with other balloons. As
such, optical communication system 316 may be configured to
transmit a free-space optical signal by modulating the ultra-bright
LED system 320. The optical communication system 316 may be
implemented with mechanical systems and/or with hardware, firmware,
and/or software. Generally, the manner in which an optical
communication system is implemented may vary, depending upon the
particular application.
[0084] In a further aspect, balloon 300 may be configured for
altitude control. For instance, balloon 300 may include a variable
buoyancy system, which is configured to change the altitude of the
balloon 300 by adjusting the volume and/or density of the gas in
the balloon 300. A variable buoyancy system may take various forms,
and may generally be any system that can change the volume and/or
density of gas in envelope 302.
[0085] In an exemplary embodiment, a variable buoyancy system may
include a bladder 310 that is located inside of envelope 302. The
buoyancy of the balloon 300 may therefore be adjusted by changing
the density and/or volume of the gas in bladder 310. To change the
density in bladder 310, balloon 300 may be configured with systems
and/or mechanisms for heating and/or cooling the gas in bladder
310. Further, to change the volume, balloon 300 may include pumps
or other features for adding gas to and/or removing gas from
bladder 310. Additionally or alternatively, to change the volume of
bladder 310, balloon 300 may include release valves or other
features that are controllable to allow air to escape from bladder
310.
[0086] Further, the balloon 300 may include a navigation system
(not shown). The navigation system may implement station-keeping
functions to maintain position within and/or move to a position in
accordance with a desired topology. In particular, the navigation
system may use altitudinal wind data to determine altitudinal
adjustments that result in the wind carrying the balloon in a
desired direction and/or to a desired location. The
altitude-control system may then make adjustments to the density of
the balloon chamber in order to effectuate the determined
altitudinal adjustments and cause the balloon to move laterally to
the desired direction and/or to the desired location.
[0087] Alternatively, the altitudinal adjustments may be computed
by a ground-based control system and communicated to the
high-altitude balloon. As another alternative, the altitudinal
adjustments may be computed by a ground-based or satellite-based
control system and communicated to the high-altitude balloon.
Furthermore, in some embodiments, specific balloons in a
heterogeneous balloon network may be configured to compute
altitudinal adjustments for other balloons and transmit the
adjustment commands to those other balloons.
[0088] As shown, the balloon 300 also includes a cut-down system
308. The cut-down system 308 may be activated to separate the
payload 306 from the rest of balloon 300. This functionality may be
utilized anytime the payload needs to be accessed on the ground,
such as when it is time to remove balloon 300 from a balloon
network, when maintenance is due on systems within payload 306,
and/or when power supply 326 needs to be recharged or replaced.
[0089] In an alternative arrangement, a balloon may not include a
cut-down system. In such an arrangement, the navigation system may
be operable to navigate the balloon to a landing location, in the
event the balloon needs to be removed from the network and/or
accessed on the ground. Further, it is possible that a balloon may
be self-sustaining, such that it theoretically does not need to be
accessed on the ground.
[0090] Note that movement and locations of balloons, such as
balloon 300, can vary since winds in the stratosphere may affect
the locations of the balloons in a differential manner. A balloon
in an example network may be configured to change its horizontal
position by adjusting its vertical position (i.e., altitude). For
example, by adjusting its altitude, a balloon may be able to find
winds that will carry the balloon horizontally (e.g., latitudinally
and/or longitudinally) to a desired horizontal location. Wind speed
and/or direction may vary with altitude, and since current wind
velocities as well as weather forecasts are available, in
principle, a balloon may be directed to a location by identifying
an altitude at which a wind direction takes a balloon to along a
desired trajectory. However, a balloon without other forms of
propulsion may be constrained to follow the wind and there may not
be a single altitude with winds taking the balloon along the
desired trajectory. In addition, to control a fleet of balloons,
movement of the balloons should occur from one location above the
surface of the Earth to another in a predictable manner.
[0091] E. Example Heterogeneous Network
[0092] In some embodiments, a high-altitude-balloon network may
include super-node balloons, which communicate with one another via
optical links, as well as sub-node balloons, which communicate with
super-node balloons via RF links. Generally, the optical links
between super-node balloons have more bandwidth than the RF links
between super-node and sub-node balloons. As such, the super-node
balloons may function as the backbone of the balloon network, while
the sub-nodes may provide sub-networks providing access to the
balloon network and/or connecting the balloon network to other
networks.
[0093] FIG. 4 is a simplified block diagram illustrating a balloon
network that includes super-nodes and sub-nodes, according to an
exemplary embodiment. More specifically, FIG. 4 illustrates a
portion of a balloon network 400 that includes super-node balloons
410A to 410C (which may also be referred to as "super-nodes") and
sub-node balloons 420 (which may also be referred to as
"sub-nodes").
[0094] Each super-node balloon 410A to 410C may include a
free-space optical communication system that is operable for
packet-data communication with other super-node balloons. As such,
super-nodes may communicate with one another over optical links.
For example, in the illustrated embodiment, super-node 410A and
super-node 401B may communicate with one another over optical link
402, and super-node 410A and super-node 401C may communicate with
one another over optical link 404.
[0095] Each of the sub-node balloons 420 may include a
radio-frequency (RF) communication system that is operable for
packet-data communication over one or more RF air interfaces.
Accordingly, each super-node balloon 410A to 410C may include an RF
communication system that is operable to route packet data to one
or more nearby sub-node balloons 420. When a sub-node 420 receives
packet data from a super-node 410, the sub-node 420 may use its RF
communication system to route the packet data to a ground-based
station 430 via an RF air interface.
[0096] As noted above, the super-nodes 410A to 410C may be
configured for both longer-range optical communication with other
super-nodes and shorter-range RF communications with nearby
sub-nodes 420. For example, super-nodes 410A to 410C may use using
high-power or ultra-bright LEDs to transmit optical signals over
optical links 402, 404, which may extend for as much as 100 miles,
or possibly more. Configured as such, the super-nodes 410A to 410C
may be capable of optical communications at speeds of 10 to 50
GB/sec.
[0097] A larger number of balloons may then be configured as
sub-nodes, which may communicate with ground-based Internet nodes
at speeds on the order of approximately 10 MB/sec. Configured as
such, the sub-nodes 420 may be configured to connect the
super-nodes 410 to other networks and/or to client devices.
[0098] Note that the data speeds and link distances described in
the above example and elsewhere herein are provided for
illustrative purposes and should not be considered limiting; other
data speeds and link distances are possible.
[0099] In some embodiments, the super-nodes 410A to 410C may
function as a core network, while the sub-nodes 420 function as one
or more access networks to the core network. In such an embodiment,
some or all of the sub-nodes 420 may also function as gateways to
the balloon network 400. Additionally or alternatively, some or all
of ground-based stations 430 may function as gateways to balloon
network 400.
III. Example Adjustable Air-to-Ground Communication Beams
[0100] In some examples, a balloon's communication system may be
capable of transmitting RF signals to ground-based stations and/or
other ground subscribers using two or more different beam widths.
For instance, a balloon may be equipped with a high-gain antenna
capable of transmitting a narrow-beam signal as well as a low-gain
antenna capable of transmitting a wide-beam signal. By using a
broader beam width, a balloon may be able to reach ground
subscribers within a larger area on the ground underneath the
balloon. However, a broader beam may not provide as strong a
communication signal as a narrow beam because the power may be
dispersed over a greater area. In further examples, balloons may be
equipped with more than two antennas, each capable of transmitting
RF communication beams with different beam widths.
[0101] A balloon may then adjust the beam width of a ground-facing
communication signal by selecting a different antenna to transmit
an RF communication signal toward subscribers on the ground. For
instance, a balloon using a high-gain antenna to transmit a
narrow-beam signal may increase the beam width by switching to a
low-gain antenna in order to cover a larger area on the ground. In
further examples, a balloon may be equipped with a transceiver
containing multiple antennas capable of transmitting RF
communication signals with different beam widths in order to
facilitate the process of adjusting beam width by switching between
antennas.
[0102] In other examples, a balloon may be capable of transmitting
an RF communication beam with a continuously adjustable beam width.
For instance, the balloon may contain a ground-facing antenna that
includes a radiating element situated to radiate toward a
reflector. The reflector may be a dish, such as a quasi-parabolic
dish that may be spherically invariant. The radiating element can
emit signals toward the reflector, which results in radiation
emitted from the antenna with a directional emission pattern. The
directional emission pattern can be approximated as a cone-shaped
region with an apex located near the antenna. The directivity of
the emission pattern is thus determined by the breadth or
narrowness of the region illuminated by the emission pattern, and
can be characterized by an opening angle of the conical surface
bounding the illuminated region. The opening angle (and thus the
antenna directivity) may be determined, at least in part, by the
separation distance between the radiating element and the
reflector. Generally, a greater separation distance corresponds to
a narrower emission pattern, whereas a lesser separation distance
corresponds to a broader emission pattern. In this example, the
width of the emission pattern may therefore be adjusted dynamically
by moving the radiating element in the antenna closer or further
from the reflector.
[0103] FIG. 5A illustrates an example high-altitude balloon 502
with a ground-facing antenna situated to illuminate a geographic
region 506 at ground level. The balloon 502 can be similar to the
balloon 300 described in connection with FIG. 3 and can include an
RF communication system mounted to a payload for operating the
ground-facing antenna, similar to the RF communication system 318
in the payload 306 of the balloon 300. The ground-facing antenna
may emit an RF communication beam 504 that causes a signal at
ground level that substantially spans the geographic region 506.
The communication beam 504 may have an angular span .theta..sub.1
that corresponds to the size of the geographic region 506 on the
ground, such as a circumference of a circular region on the
ground.
[0104] In some examples, the angular span of a balloon's
communication beam may be adjusted in order to change the size of
the geographic region reached by the beam at ground level. For
instance, the balloon may be equipped with two or more RF antennas,
each capable of transmitting RF communication beams with different
beams. The beam width of a ground-facing RF communication beam may
then be modified by switching between two different antennas. In
some examples, multiple antennas may be incorporated within a
single transceiver to facilitate switching between antennas (and
communication beam widths). Or, in other examples, the balloon may
be equipped with an RF antenna capable of transmitting a
continuously adjustable RF communication signal.
[0105] FIG. 5B illustrates the balloon 502 transmitting a
communication beam with a broader beam width than FIG. 5A. More
specifically, the balloon 502 may illuminate the geographic region
510 by transmitting a communication beam 508 from a ground-facing
antenna so as to substantially span the geographic region 510 at
ground level. The communication beam 508 may have an angular span
.theta..sub.2 that corresponds to the size of the geographic region
510 on the ground. By increasing the width of the communication
beam 508 and the corresponding angular span .theta..sub.2, a
greater area may be covered by the communication beam 508 at ground
level. While the adjustable communication beams 504, 508 are
described herein in connection with the high-altitude balloon 502
for purposes of convenience, it is specifically noted that a
communication system with antenna(s) capable of transmitting RF
communication beams with an adjustable beam width may be mounted
to, and used in connection with, a variety of high altitude
platforms, such as other lighter-than-air devices and the like.
[0106] Additionally, it is noted that the discussion herein
generally refers to transmission of radio signals with adjustable
beam widths (or emission patterns) to illuminate geographic regions
(e.g., the geographic regions 506, 510 at ground level illuminated
by the communication beams 504, 508). However, due to the general
reciprocity between emission and reception of radio signals in
antenna theory and design, it is recognized that the discussion
throughout generally has equal application to the reception of
signals from a particular ground-level geographic region. That is,
the antenna(s) with adjustable beam widths may be used additionally
or alternatively to receive signals arriving from the emission
patterns (e.g., from within the geographic regions 506, 510 at
ground level). In such an example, adjusting the beam width may
allow a receiving antenna (mounted to the high-altitude balloon) to
receive communication signals from ground-based stations and/or
other ground subscribers from different geographical regions on the
ground, such as shown in FIGS. 5A and 5B.
IV. Example Methods
[0107] FIG. 6 is a block diagram of a method, according to an
example embodiment. The method 600 may be carried out by one or
more computing systems located on an individual balloon and/or
multiple balloons in communication with one another. In further
examples, all or some of method 600 may be carried out by a control
system of a balloon network. For example, some or all of method 600
may be carried out by a central control system and/or regional
systems such as the ones described above with respect to FIG. 2.
The control system(s) may communicate with the balloons within the
balloon network. In some examples, the parts of the method 600 may
be combined, separated into additional parts, and/or carried out in
a different order than shown. Other configurations are also
possible.
[0108] More specifically, the method 600 may initially involve
determining a contiguous ground coverage area served by a group of
balloons, as shown by block 602. A contiguous ground coverage area
over a region may be formed by the individual coverage areas from
each of the balloons within the region. Particular points within
the ground coverage area may be served by at least one of the
balloons so that the balloon can transmit and/or receive an RF
communication signal which reaches the points at ground level.
[0109] For example, a particular balloon may cover a certain area
on the ground located underneath the balloon (e.g., a circle on the
ground with a center point directly under a horizontal position of
the balloon in the air). The size of the area covered by a
particular balloon may be based on the altitude of the balloon as
well as the width of a ground-facing communication beam of the
balloon. A broader beam width may cover a greater area on the
ground. Additionally, a balloon higher in altitude may cover a
greater area on the ground than a balloon lower in altitude, if
both balloons are using the same beam width. In certain examples,
balloons may be equipped with RF antennas that project a signal
over an individual coverage area with a different shape besides a
circle as well (e.g., an ellipse).
[0110] In some examples, when the individual coverage areas from
each of the balloons are added together (e.g., when the circles on
the ground are combined), a contiguous ground coverage area over a
certain region may be formed. The ground coverage area may be
contiguous in that it does not contain any gaps in coverage (e.g.,
points on the ground that are not served by any of the balloons). A
contiguous ground coverage area could cover a particular
geographical region, a city, or a country, for example.
[0111] In some examples, the contiguous ground coverage area may be
determined by positioning balloons within a network at certain
horizontal positions and/or altitudes, and then selecting beam
widths for ground-facing communication signals from the balloons to
cover an entire area. In other examples, the contiguous ground
coverage area may be determined only by selecting beam widths for
the communication signals, such as when the positions of the
balloons are partially or totally uncontrollable by the balloon
network. In certain examples, beam widths (and corresponding
individual coverage areas) may be chosen to provide contiguous
coverage over the region with a minimal amount of overlap between
individual coverage areas. In other examples, multiple balloons may
cover certain overlapping areas on the ground for redundancy
benefits.
[0112] FIG. 7A illustrates a top view of an example configuration
of three balloons and corresponding individual coverage areas. More
specifically, a first balloon 702 may be equipped with a
communication system 704 that includes a ground-facing RF antenna
that may project an RF communication signal over the area 706 on
the ground underneath the balloon 702. Additionally, a second
balloon 708 may be equipped with a communication system 710 that
includes a ground-facing RF antenna that may project an RF
communication signal over a different area 712 on the ground.
Furthermore, a third balloon 714 may be equipped with a
communication system 716 that includes a ground-facing RF antenna
that may project an RF communication signal over another different
area 718 on the ground.
[0113] A contiguous ground coverage area may then be formed by the
regions 706, 712, 718. Any point on the ground within the coverage
area may be covered by at least one of the balloons 702, 708, 714.
In this simplified example, three balloons are shown, but a ground
coverage area could include individual coverage areas from hundreds
or thousands of balloons within a network, as well. Additionally,
the communication systems 704, 710, 716 of the balloons may all be
the same in some examples, or they may be different on different
balloons in other examples as well.
[0114] In further examples, a ground coverage area may include
different levels of coverage to different parts of a region based
on demand level. For instance, certain areas may have denser
populations or greater service demands for other reasons. Each
balloon may have a limit on the capacity of data that it can
transmit to ground subscribers (e.g., 1 MB/s, 10 MB/s, or 100
MB/s). Accordingly, in some examples, a certain number of balloons
may be positioned over a region in order to satisfy the demands
within the region at ground level. A sufficient level of coverage
may therefore be provided by a balloon network to meet the
different demands of each section of the ground coverage area.
[0115] The method 600 may then involve determining a change in
position of at least one of the balloons, as shown by block 604.
More specifically, the horizontal (latitudinal and/or longitudinal)
position and/or altitude of individual balloons within a network
may change over time. For instance, wind or other environmental
factors may cause balloons to change position. Additionally, in
some examples, individual balloons may periodically be assigned to
relocate to different areas for purposes of providing coverage
and/or for other tasks.
[0116] In some instances, movements of one or more balloons within
the network may be expected to cause a gap in coverage at ground
level. For instance, a balloon that was the only balloon providing
coverage to a particular area directly under the balloon may be
blown in a horizontal direction so that the balloon is no longer
over the particular area and no longer provides coverage to the
area using its current ground-facing beam width. In some examples,
a prediction about a possible gap in coverage may be made in
advance based on expected balloon movements (e.g., a weather
forecast may predict wind in a particular direction). In other
examples, the prediction may occur partway through balloon
movements or after certain balloon movements have already occurred
as well.
[0117] FIG. 7B shown an example configuration of the three balloons
from FIG. 7A where one of the balloons has moved horizontally. More
specifically, balloon 714 may have moved to the right so that the
area 706 on the ground covered by the balloon 702 no longer touches
the area 718 covered by the balloon 714. In such a circumstance, a
gap in the ground coverage area may occur in between the balloon
702 and the balloon 714. In some examples, a determination may be
made that a gap may occur before the balloon 714 has started to
move or while the balloon 714 is partway through a change in
position as well.
[0118] The method 600 may then involve determining an adjustment to
an individual coverage area of one of the balloons in an effort to
maintain contiguous ground coverage, as shown by block 606. More
specifically, a beam width of one or more of the balloons may be
increased or decreased in order to preserve contiguous ground
coverage after one or more of the balloons have changed position.
By increasing the beam width of a particular balloon, the
individual coverage area of the balloon (e.g., the circle on the
ground) may be increased, such as to prevent a gap in coverage on
the ground that may otherwise occur.
[0119] In some examples, a minimal increase in an individual
coverage area of a balloon may be determined in order to maintain
contiguous ground coverage. For instance, the individual coverage
area of a balloon may not be increased any more than necessary in
order to avoid reducing the signal strength at ground level. In
other examples, the individual coverage areas of multiple balloons
may be adjusted. For instance, the coverage areas of two or three
different balloons may each be increased in order to prevent a
possible gap in coverage. In certain examples, individual coverage
areas of some balloons may be increased while individual coverage
areas of other balloons may be decreased as well.
[0120] The method 600 may further involve adjusting a width of the
ground-facing communication beam of the balloon in order to adjust
the individual coverage area of the balloon, as shown by block 608.
More specifically, the individual coverage area of the balloon may
be adjusted as previously determined by adjusting the balloon's
beam width in order to maintain contiguous ground coverage after
one or more of the balloons change position. In some examples, an
adjustment to a beam width of the communication signal from one of
the balloons may be completed before the balloons have changed
position to a point where a gap in service to the area may
occur.
[0121] The beam width of a ground-facing communication beam of a
balloon may be adjusted using any of the methods described above.
For instance, a balloon's communication system may switch between
two or more RF antennas, each capable of transmitting a signal with
a different beam width. Or a balloon may be equipped with an
antenna with a continuously adjustable beam width, in which case
the beam width may be adjusted by adjusting the spacing between a
radiator and a ground-facing reflector, for example.
[0122] FIG. 7C shows another configuration of the three balloons
from FIG. 7B. More specifically, the beam width of the balloon 714
may be increased in order to cover a larger area 718 at ground
level. By increasing the individual coverage area 718 of the
balloon 714, any gap in coverage that may have occurred as a result
of the change in position of the balloon 714 may be avoided. In
other examples, the individual coverage area 706 of the balloon 702
or the individual coverage area 712 of the balloon 708 may be
increased instead in order to maintain contiguous coverage. In
further examples, a combination of the individual coverage areas
706, 712, and 718 may also be increased in order to avoid a gap in
coverage.
[0123] In certain examples, different sections of a ground coverage
area may be associated with different levels of demand from ground
subscribers as previously noted. In such examples, contiguous
ground coverage may therefore be defined as a level of coverage
that meets the level of demand over an entire region. For instance,
an adjustment to an individual coverage area of a balloon may be
determined as part of Method 600 in an effort to avoid an
insufficient level of service to a particular region (in addition
to or instead of a literal gap in coverage). For example, the
demand level of a particular area may require service from at least
two balloons. In such an example, if one of the balloons moves
horizontally away from the area (e.g., as in FIG. 7B), the beam
width of the balloon or a different balloon may be increased in
order to ensure that the area continues to have a sufficient level
of service at ground level.
[0124] In other examples, a change in position of one or more
balloons may include a change in altitude. If a balloon rises in
altitude, the individual ground coverage area of the balloon may
increase, assuming a fixed beam width. Similarly, if the balloon
decreases in altitude, the individual ground coverage area of the
balloon may decrease, assuming a fixed beam width. In some
examples, changes in altitude of one or more of the balloons in an
area may therefore be expected to cause a gap in the coverage
provided by a group of balloons at ground level.
[0125] In certain examples, the beam width of a balloon may be
adjusted in order to keep the individual coverage area of the
balloon on the ground fixed or at least approximately fixed as the
balloon changes in altitude. For instance, as a balloon increases
in altitude, the angular span of a ground-facing communication beam
may be narrowed so that the beam spans roughly the same area at
ground level. Additionally, as the balloon decrease in altitude,
the angular span of a ground-facing communication beam may be
broadened so that the beam spans roughly the same area at ground
level. In some examples, a balloon's antenna can be configured such
that the emission patterns at least approximately span the same
ground level geographic region regardless of the elevation of the
balloon. Thus, the balloon can be configured to maintain
communication with a substantially fixed geographic region even as
the balloon ascends and descends to various elevations.
[0126] Moreover, a narrower ground-facing communication beam may
have a greater directional gain. As such, the increased directional
gain of the beam's emission pattern may at least partially
compensate for the greater distance between the balloon and the
ground level when the balloon is at a higher altitude. For example,
the radiation at ground level in the covered geographic region may
have comparable intensity whether from a broader emission pattern
with the balloon at a lower altitude or from a narrower emission
pattern with the balloon at a higher altitude. The more directed
emission pattern from a balloon at a higher altitude may thereby at
least partially compensate for the altitude-dependent variations in
radiation intensity at ground level.
[0127] FIG. 7D shows a top view of an example configuration of
three balloons, with one balloon lower in altitude than the other
two balloons. More specifically, balloon 714 may change position by
decreasing in altitude relative to balloons 702 and 708. If the
beam width of the ground-facing communication beam from the
communication system 716 of the balloon 714 is kept fixed, the
individual coverage area 718 of the balloon at ground level may
decrease in size. In some examples, the change in altitude of the
balloon 714 may be expected to cause a gap in ground coverage, such
as in the section of the ground between the area 706 covered by the
balloon 702 and the area 718 covered by the balloon 714.
[0128] In order to maintain contiguous ground coverage, the beam
width of the balloon 714 may be adjusted to account for the change
in altitude of the balloon 714. In particular, in some examples,
the beam width of the balloon 714 may be adjusted in order to keep
the individual coverage area 718 of the balloon 714 relatively
fixed in size regardless of the current altitude of the balloon
714. As the altitude of the balloon 714 increases, the beam width
may be narrowed in order to keep the ground coverage area 718 from
increasing in size. Additionally, as the altitude of the balloon
714 decreases, the beam width may be widened in order to keep the
ground coverage area 718 from decreasing in size.
[0129] FIG. 7E illustrates a top view of another example
configuration of the balloons from FIG. 7D. More specifically, the
beam width of the ground-facing communication beam from the
communication system 716 on the balloon 714 may be increased in
order to keep the ground coverage area 718 of the balloon 714 from
decreasing in size as the balloon 714 drops in altitude. In some
examples, adjustments to the beam width of the balloon 714 may be
made far enough in advance of any changes in altitude by the
balloon 714 that contiguous coverage on the ground from the group
of balloons may be maintained. In other examples, beam widths of
balloon 702 and/or balloon 708 may be adjusted as well or instead
in an effort to maintain contiguous coverage as the balloon 714
changes altitude.
[0130] In some examples, balloons may generally operate between a
first altitude near a low end of a desired stratospheric altitude
for a high-altitude balloon (e.g., 18 km), and a second altitude
near a high end of a desired stratospheric altitude for a
high-altitude balloon (e.g., 25 km). In order to maintain a
relatively constant coverage area on the ground as a balloon
changes altitude from the first altitude to the second altitude,
the angular span of an example emission pattern at the first
altitude can be approximately 90.degree. (e.g., an approximately
conical radiation pattern with a 45.degree. half-width), and the
angular span of an example emission pattern at the second altitude
can be approximately 70.degree. (e.g., an approximately conical
radiation pattern with a 36.degree. half-width).
[0131] In a further example, beam widths of ground-facing
communication signals from balloons can be adjusted to account for
variations in ground-level elevation. For example, a balloon can
include an antenna with an emission pattern that is adjusted based
on the altitude of the balloon, relative to ground level
immediately below the balloon. In other words, the emission pattern
can be adjusted based on the absolute altitude, relative to
sea-level, such as detected by ambient pressure, and can
additionally or alternatively be adjusted based on altitude,
relative to ground. Thus, the balloon may be configured to at least
partially compensate for variations in relative altitude (e.g., due
to the balloon passing over regions with variations in ground level
altitude) in order to maintain an at least approximately constant
geographic span and/or intensity level of radiation reaching ground
level. In one example, the balloon may traverse over a region with
a series of ground elevation changes (e.g., hills, valleys, slopes,
flat areas, mountains, etc.). An example balloon may dynamically
adjust the radiation pattern of its ground-facing antenna to at
least partially compensate for altitude-dependent variations in the
radiation that reaches the ground from the balloon. For example,
the emission pattern may be relatively broad while over a high
elevation region (and low relative altitude). Similarly, the
emission pattern may be relatively narrow while over a low
elevation region (and high relative altitude).
[0132] In some examples, the relative altitude (i.e., distance from
ground to balloon) can be determined by predetermined ground-level
elevation data in combination with position information (e.g., as
determined by a GPS receiver or the like) and one or more altitude
sensors on the balloon (e.g., altimeters and/or pressure sensors
and the like). Upon determining position information for the
balloon, such as latitude and longitude coordinates, a mapping
database can be accessed to determine a corresponding ground level
elevation immediately below the balloon. The ground-level
elevation, which can be determined by a computer system on the
balloon (e.g., similar to the computer system 312 in the payload
306 of the balloon 300) and/or by a remote server in communication
with the balloon, can then be combined with the altitude of the
balloon as determined via the on-board sensors to determine the
distance from the balloon to the ground (i.e., the relative
altitude). In other examples, the balloon may include sensors
configured to directly sense and/or determine the relative altitude
of the balloon, such as downward facing radar and the like.
[0133] In a further example, the beam width of a balloon can be
adjusted to account for influences on the radiation from the
balloon due to atmospheric effects, such as weather patterns in the
troposphere. As an example, particular portions of the spectrum may
be sensitive to inclement weather due to increases in radiation
attenuating water vapor and/or droplets in the troposphere, for
example. To achieve a desired radiation intensity at ground level
(e.g., a minimum signal to noise ratio), the emission pattern may
be narrowed in response to detecting certain weather patterns. In
other words, the radiation pattern may be narrowed so as to
increase the directional gain in the illuminated region at ground
level, to account for radiation attenuating weather patterns in the
atmosphere between ground level and the high-altitude balloon. In
some examples, such weather-related effects can be accounted for by
systems that dynamically detect weather patterns and communicate
accordingly with the balloon. In other examples, such
weather-related effects can be detected directly via sensors on the
balloon. Additionally or alternatively, such weather conditions
(and/or other signal degrading phenomena) can be inferred through
detection of degradation in signal strength at stations at
ground-level. In other words, the signal-to-noise ratio (or other
measure of signal strength) at ground-based stations can be used as
feedback information to dynamically adjust the emission pattern,
and thus the directional gain, of a ground-facing antenna on the
balloon.
[0134] In other examples, adjustments to beam widths of
ground-facing communication beams on one or more balloons may be
made based on multiple simultaneous changes in position of
balloons, possibly including both horizontal changes in position
and changes in altitude. For instance, rather than keeping the
coverage area of an individual balloon relatively constant as the
balloon changes in altitude, beam widths of other neighbouring
balloons may instead be increased or decreased in order to maintain
contiguous coverage or a desired level of coverage to certain
regions. A control system may leverage disclosed systems and
methods in order to adjust beam widths of ground-facing
communication signals from balloons in more complex networks as
well, including networks that contain hundreds or thousands of
balloons.
V. Conclusion
[0135] The examples given in the preceding sections are meant for
purposes of explanation and are not meant to be limiting. Other
types of balloons and/or balloon networks may benefit from the
disclosed systems and methods for adjusting ground-facing RF
communication beam widths as well, without departing from the
spirit or scope of the subject matter presented herein.
[0136] Further, the above detailed description describes various
features and functions of the disclosed systems, devices, and
methods with reference to the accompanying figures. In the figures,
similar symbols typically identify similar components, unless
context dictates otherwise. The example embodiments described
herein and in the figures are not meant to be limiting. Other
embodiments can be utilized, and other changes can be made, without
departing from the spirit or scope of the subject matter presented
herein. It will be readily understood that the aspects of the
present disclosure, as generally described herein, and illustrated
in the figures, can be arranged, substituted, combined, separated,
and designed in a wide variety of different configurations, all of
which are explicitly contemplated herein.
[0137] With respect to any or all of the ladder diagrams,
scenarios, and flow charts in the figures and as discussed herein,
each block and/or communication may represent a processing of
information and/or a transmission of information in accordance with
example embodiments. Alternative embodiments are included within
the scope of these example embodiments. In these alternative
embodiments, for example, functions described as blocks,
transmissions, communications, requests, responses, and/or messages
may be executed out of order from that shown or discussed,
including substantially concurrent or in reverse order, depending
on the functionality involved. Further, more or fewer blocks and/or
functions may be used with any of the ladder diagrams, scenarios,
and flow charts discussed herein, and these ladder diagrams,
scenarios, and flow charts may be combined with one another, in
part or in whole.
[0138] A block that represents a processing of information may
correspond to circuitry that can be configured to perform the
specific logical functions of a herein-described method or
technique. Alternatively or additionally, a block that represents a
processing of information may correspond to a module, a segment, or
a portion of program code (including related data). The program
code may include one or more instructions executable by a processor
for implementing specific logical functions or actions in the
method or technique. The program code and/or related data may be
stored on any type of computer readable medium such as a storage
device including a disk or hard drive or other storage medium.
[0139] The computer readable medium may also include non-transitory
computer readable media such as computer-readable media that stores
data for short periods of time like register memory, processor
cache, and random access memory (RAM). The computer readable media
may also include non-transitory computer readable media that stores
program code and/or data for longer periods of time, such as
secondary or persistent long term storage, like read only memory
(ROM), optical or magnetic disks, compact-disc read only memory
(CD-ROM), for example. The computer readable media may also be any
other volatile or non-volatile storage systems. A computer readable
medium may be considered a computer readable storage medium, for
example, or a tangible storage device.
[0140] Moreover, a block that represents one or more information
transmissions may correspond to information transmissions between
software and/or hardware modules in the same physical device.
However, other information transmissions may be between software
modules and/or hardware modules in different physical devices.
[0141] While various aspects and embodiments have been disclosed
herein, other aspects and embodiments will be apparent to those
skilled in the art. The various aspects and embodiments disclosed
herein are for purposes of illustration and are not intended to be
limiting, with the true scope and spirit being indicated by the
following claims. Functionally equivalent methods and apparatuses
within the scope of the disclosure, in addition to those enumerated
herein, will be apparent to those skilled in the art from the
foregoing descriptions. Such modifications and variations are
intended to fall within the scope of the appended claims.
* * * * *