U.S. patent application number 15/332976 was filed with the patent office on 2017-04-13 for methods and apparatus for mitigating fading in a broadband access system using drone/uav platforms.
The applicant listed for this patent is UBIQOMM LLC. Invention is credited to Ahmad Jalali.
Application Number | 20170105139 15/332976 |
Document ID | / |
Family ID | 54323166 |
Filed Date | 2017-04-13 |
United States Patent
Application |
20170105139 |
Kind Code |
A1 |
Jalali; Ahmad |
April 13, 2017 |
METHODS AND APPARATUS FOR MITIGATING FADING IN A BROADBAND ACCESS
SYSTEM USING DRONE/UAV PLATFORMS
Abstract
Systems and methods for mitigating the effects of atmospheric
conditions such as rain, fog, cloud in a broadband access system
using drone/UAVs. In one embodiment, terminal and drone radio and
transmission medium fixture sub-systems comprise multiple
transmission media. In one embodiment, in response to changes in
atmospheric conditions the drone radio sub-system switches
transmission medium to reduce the effects of atmospheric
conditions. In another embodiment, the terminal and drone radio
sub-systems equalize the data rates among terminals in response to
changes in atmospheric conditions observed by different terminals.
In another embodiment, the drone radio sub-system adjusts the
transmit power on the downlink to different terminal according to
fading due to atmospheric conditions on each link.
Inventors: |
Jalali; Ahmad; (San Diego,
CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
UBIQOMM LLC |
San Diego |
CA |
US |
|
|
Family ID: |
54323166 |
Appl. No.: |
15/332976 |
Filed: |
October 24, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14295160 |
Jun 3, 2014 |
9479964 |
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15332976 |
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61981128 |
Apr 17, 2014 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L 5/0094 20130101;
H04W 52/241 20130101; H04W 52/04 20130101; B64C 39/024 20130101;
H04W 28/04 20130101; H04W 72/0473 20130101; H04W 74/00 20130101;
H04B 7/18504 20130101; H04L 5/0071 20130101; H04L 5/006 20130101;
H04W 52/143 20130101; H04L 5/0078 20130101; H04L 5/0096 20130101;
H04B 17/336 20150115; B64C 2201/122 20130101; H04L 1/00 20130101;
B64C 39/00 20130101; H04L 5/00 20130101 |
International
Class: |
H04W 28/04 20060101
H04W028/04; B64C 39/02 20060101 B64C039/02; H04B 17/336 20060101
H04B017/336; H04W 72/04 20060101 H04W072/04; H04B 7/185 20060101
H04B007/185; H04L 5/00 20060101 H04L005/00 |
Claims
1. A drone configured to provide broadband access to one or more
terminals, the drone comprising: at least one transmission medium
fixture comprising a plurality of transmission mediums configured
to provide coverage to one or more terminals; wherein various ones
of the plurality of transmission mediums are associated with
different resistances to different fading conditions; at least one
radio sub-system configured to: demodulate and decode one or more
first signals received from the one or more terminals; and modulate
and transmit one or more second signals to the one or more
terminals; and a drone switching sub-system configured to switch
data received at the drone to another receiving unit of the one or
more terminals and/or one or more drones; wherein the drone
switching sub-system is configured to select a transmission medium
based on a measured fading condition.
2. The drone of claim 1, wherein: the one or more terminals
comprise one or more ground-based mobile terminals; the drone radio
sub-system is further configured to determine an amount of
transmission resources to be allocated to one or more downlinks of
the different ones of the one or more ground-based mobile terminals
to equalize a data rate among the different ones of the one or more
ground-based mobile terminals according to a fairness criterion;
and the drone switching sub-system further comprises a scheduler,
the scheduler configured to schedule the determined amount of
transmission resources to the downlink of the different ones of the
one or more ground-based mobile terminals.
3. The drone of claim 2, wherein the drone radio sub-system is
further configured to: determine a change on an uplink signal
quality received from different ones of the one or more
ground-based mobile terminals due to one or more atmospheric
conditions; and determine an amount of transmission resources to be
allocated to an uplink of the different ones of the one or more
terminals to equalize a data rate among the different ones of the
one or more terminals according to at least one fairness criterion;
and the scheduler is further configured to: schedule the determined
amount of transmission resources to the uplink of the different
ones of the one or more terminals; and inform the different ones of
the one or more terminals of respective scheduled transmission
resources.
4.-5. (canceled)
6. The drone of claim 1, wherein the drone radio sub-system is
further configured to: determine a change in an amount of power
allocated on a downlink to at least one of the one or more
terminals to equalize the data rate among different terminals
according to at least one fairness criterion; and adjust the power
allocated to the downlink of to one or more of the one or more
terminals.
7. The drone of claim 6, wherein the drone radio sub-system is
further configured to: encode terminal data; map the coded bits
onto constellation symbols; scale the coded symbols from each
terminal destined to different antenna elements to form a beam
toward a respective terminal; sum the scaled coded symbols for
different terminals destined to a same antenna aperture to form
multiple beams, one toward each respective terminal; modulate the
resulting symbols onto the selected transmission medium and
transmit the resulting signal through the corresponding antenna
aperture.
8. The drone of claim 7, wherein the drone radio subsystem is
further configured to choose the scale for coded symbols for each
terminal to adjust the power sent to a terminal on the respective
downlink.
9. A method of providing broadband access using a plurality of
drones, the method comprising: measuring a signal quality metric
for one or more terminals of a plurality of terminals; comparing
the measured signal quality metric versus one or more threshold
values; determining if the signal quality metric of the one or more
terminals has degraded due to one or more atmospheric conditions;
and select a different transmission medium when the signal quality
metric of the one or more terminals has degraded.
10. The method of claim 9, further comprising: determining a number
of transmission resources that an uplink and downlink to the one or
more terminal needs in order to equalize the throughput to
different ones of the plurality of terminals according to a
specified fairness criterion; informing a scheduler of the
allocated number of transmission resources for a terminal link of
the one or more terminals; and sending a message to one or more
terminals comprising respective uplink transmission resource
allocations.
11. The method of claim 9, further comprising switching to a second
transmission medium to mitigate atmospheric-related fading.
12. The method of claim 9 further comprising adjusting a power
allocated to each terminal on a downlink according to a change in
the measured signal quality metric.
13. A mobile terminal, comprising: a mobile terminal radio
sub-system comprising at least one transmission medium fixture
configured to receive data signaling on at least two transmission
mediums having different resistance to atmospheric effects, the
mobile terminal radio sub-system configured to: demodulate and
decode one or more first signals received on at least one
transmission medium of the at least two transmission mediums from
at least one of one or more drones; responsive to a switch
instruction, the at least one transmission medium fixture switches
to a different transmission medium of the at least two transmission
mediums.
14. The mobile terminal of claim 13, wherein the mobile terminal
radio sub-system is further configured to: measure a received
downlink signal quality to determine a signal quality change due to
atmospheric conditions; and send the measured signal quality to the
at least one radio sub-system of the one or more drones.
15. The mobile terminal of claim 13, wherein the mobile terminal
radio sub-system is further configured to measure a change in a
received downlink signal quality to determine a signal quality
change due to one or more atmospheric conditions; and send the
measured change in a received downlink signal quality to the drone
radio sub-system.
16. The mobile terminal of claim 13, wherein the mobile terminal
radio sub-system is further configured to: measure a received
downlink signal quality to determine a change in signal quality due
to one or more atmospheric conditions; and send the measured signal
quality to at least one drone.
17. The mobile terminal of claim 13, wherein the one or more
atmospheric conditions are selected from the group consisting of:
(i) fog, (ii) clouds, and (iii) rain.
18. (canceled)
19. The mobile terminal of claim 13, wherein the mobile terminal
radio sub-system is further configured to: receive a schedule of
transmission resources to use for communication with at least one
drone; and configure communication to the at least one drone based
on the received schedule.
20. The mobile terminal of claim 13, wherein the measured signal
quality comprises a signal to interference plus noise ratio (SINR).
Description
PRIORITY
[0001] This application claims priority to co-owned, co-pending
U.S. Patent Provisional Application Ser. No. 61/981,128, filed on
Apr. 17, 2014, and entitled "METHODS AND APPARATUS FOR MITIGATING
FADING IN A BROADBAND ACCESS SYSTEM USING DRONE/UAV PLATFORMS", the
foregoing being incorporated by reference herein in its
entirety.
RELATED APPLICATIONS
[0002] The application is related to co-owned, co-pending U.S.
patent application Ser. No. 14/222,497, and entitled "BROADBAND
ACCESS TO MOBILE PLATFORMS USING DRONE/UAV", filed on Mar. 21,
2014, and co-owned, co-pending U.S. patent application Ser. No.
14/223,705 entitled "BROADBAND ACCESS SYSTEM VIA DRONE/UAV
PLATFORMS", filed on Mar. 24, 2014, each of the foregoing
incorporated by reference herein in its entirety.
COPYRIGHT
[0003] A portion of the disclosure of this patent document contains
material that is subject to copyright protection. The copyright
owner has no objection to the facsimile reproduction by anyone of
the patent document or the patent disclosure, as it appears in the
Patent and Trademark Office patent files or records, but otherwise
reserves all copyright rights whatsoever.
BACKGROUND
[0004] 1. Technological Field
[0005] The present disclosure describes, among other things,
aspects of a system for broadband internet access using drones as a
platform to relay internet traffic among different types of
terminals.
[0006] 2. Description of Related Technology
[0007] As internet traffic has increased, new technologies are
needed to deliver broadband access to homes and enterprises at
lower cost and to places that are not yet covered. Examples of
current broadband delivery systems include terrestrial wired
networks such as DSL (Digital Subscriber Line) on twisted pair,
fiber delivery systems such as FiOS (Fiber Optic Service), and
geo-stationary satellite systems. The current broadband access
systems have a number of short comings. One issue is lack of
service in remote and/or lightly populated areas. Geo-stationary
satellites do provide service in remote areas of the developed
world such as the United States. Poorer areas of the world,
however, lack adequate satellite capacity.
[0008] A notable reason satellite capacity has not been adequately
provided in poor regions of the world is the relatively high cost
of satellite systems. Due to adverse atmospheric effects in
satellite orbits, satellite hardware must be space qualified and is
costly. Launch vehicles to put the satellites in orbit are also
costly. Moreover, due to the launch risk and the high cost of
satellites, there may be significant insurance costs for the
satellite and the launch. Therefore, broadband satellite systems
and services are relatively costly and difficult to justify in poor
regions of the world. It is also costly to deploy terrestrial
systems such as fiber or microwave links in lightly populated
regions. The small density of subscribers does not justify the
deployment cost.
SUMMARY
[0009] The present disclosure describes, inter alia, systems and
methods for broadband access to homes, enterprises, and mobile
platforms (such as airplanes and vehicles) using a network of
drones.
[0010] In a first aspect, a drone is disclosed. In one embodiment,
the drone is configured to provide broadband access to one or more
terminals, and includes: at least one transmission medium fixture
comprising at least one transmission medium configured to provide
coverage to one or more terminals; at least one radio sub-system
configured to demodulate and decode one or more first signals
received from the one or more terminals, and modulate and transmit
one or more second signals to the one or more terminals; and a
drone switching sub-system configured to switch data received at
the drone to another receiving unit of the one or more terminals
and/or the one or more drones.
[0011] In one variant, the one or more terminals comprise one or
more ground-based mobile terminals. The drone radio sub-system is
further configured to determine an amount of transmission resources
to be allocated to one or more downlinks of the different ones of
the one or more ground-based mobile terminals to equalize a data
rate among the different ones of the one or more ground-based
mobile terminals according to a fairness criterion. A scheduler is
also included, the scheduler configured to schedule the determined
amount of transmission resources to the downlink of the different
ones of the one or more ground-based mobile terminals.
[0012] In another aspect, a method of providing broadband access
using a plurality of drones is disclosed. In one embodiment, the
method includes: measuring a signal quality metric; comparing the
measured signal quality metric for one or more terminals of a
plurality of terminals versus one or more threshold values; and
determining if the signal quality metric of the one or more
terminals has degraded due to one or more atmospheric
conditions.
[0013] In one variant, the method further includes determining a
number of transmission resources that an uplink and downlink to the
one or more terminals needs in order to equalize the throughput to
different ones of the plurality terminals according to a specified
fairness criterion. In another variant, a scheduler is informed of
the allocated number of transmission resources for each terminal
link; and a message is sent to one or more terminals comprising
respective uplink transmission resource allocations.
[0014] In another aspect, a mobile terminal is disclosed. In one
embodiment, the terminal includes a mobile terminal radio
sub-system comprising at least one transmission medium fixture
configured for use with at least two transmission mediums. In one
variant, the mobile terminal radio sub-system is configured to:
demodulate and decode one or more first signals received on at
least one transmission medium of the at least two transmission
mediums from at least one of one or more drones; modulate and
transmit the one or more first signals on the at least one
transmission medium to the at least one of the one or more drones;
and responsive to a switch instruction, the at least one
transmission medium fixture switches to a different transmission
medium of the at least two transmission mediums.
[0015] This disclosure describes systems and methods for mitigating
rain, fog, cloud and other atmospheric effects for a drone based
broadband access system to homes, enterprises, and mobile
platforms. The system comprises one or more drones, each drone
comprising at least one transmission medium fixture supporting at
least one radio frequency or free space optics transmission medium
configured to provide coverage to one or more ground/mobile
terminals. Each drone comprises at least one radio sub-system
configured to demodulate and decode one or more first signals
received from the one or more ground/mobile terminals on at least
one transmission medium. The drone radio sub-system is further
configured to modulate and transmit one or more second signals to
the one or more ground/mobile terminals on at least one
transmission medium. Drone communications system further comprises
a switching sub-system configured to switch data received at the
drone to another receiving unit. Each ground/mobile terminal
comprises systems and methods to demodulate and decode the one or
more second signals received on at least one transmission medium
from at least one of the one or more drones corresponding thereto;
and to modulate and transmit the one or more first signals on at
least one transmission medium to the at least one of the one or
more drones.
[0016] One aspect of the disclosure comprises systems and methods
for: the ground/mobile terminal radio sub-system to measure changes
in received downlink signal quality due to rain, fog, cloud and
other atmospheric conditions, and to send the measured signal
quality to the drone radio sub-system; the drone radio sub-system
to determine the amount of time that must be allocated to the
downlinks of the different ground/mobile terminals to equalize the
data rate among different terminals according to some fairness
criterion; and the scheduler at the drone processor to schedule the
determined number of time slots or bandwidth to the downlink of
different ground/mobile terminals.
[0017] Another aspect of the disclosure comprises: a drone radio
sub-system to determine changes on the uplink signal quality
received from different ground/mobile terminals due to rain, fog,
cloud and other atmospheric conditions; the drone radio sub-system
to determine the amount of time that must be allocated to the
uplink of the different ground/mobile terminals to equalize the
data rate among different terminals according to some fairness
criterion; and the scheduler at the drone processor to schedule the
determined number of time slots or bandwidth to the uplink of
different ground/mobile terminals.
[0018] Another aspect of the disclosure comprises systems and
methods for the ground/mobile terminal radio sub-system to measure
changes in received downlink signal quality due to rain, fog, cloud
and other atmospheric conditions, and to send the measured signal
quality to the drone radio sub-system; the drone radio sub-system
to determine whether to switch to a different transmission medium
on the downlink with less fading from atmospheric conditions, and
to send the information on the new medium and the time to switch to
the new downlink medium to the ground/mobile terminal; the drone
radio sub-system to switch to the new medium on the downlink at the
specified time; and a ground/mobile terminal to switch to the new
medium on the downlink at the specified time.
[0019] The system further comprises systems and methods for: the
drone radio sub-system to measure changes in received uplink signal
quality due to rain, fog, cloud and other atmospheric conditions;
the drone radio sub-system to determine whether to switch to a
different transmission medium on the uplink with less fading due to
atmospheric conditions, and to send the information on the new
medium and the time to switch to the new uplink medium to the
ground/mobile terminal; the drone radio sub-system to switch to the
new medium on the uplink at the specified time; and the
ground/mobile terminal to switch to the new medium on the uplink at
the specified time.
[0020] Another aspect of the disclosure comprises systems and
methods for: the ground/mobile terminal radio sub-system to measure
changes in received downlink signal quality due to rain, fog, cloud
and other atmospheric conditions, and to send the measured signal
quality to the drone radio sub-system; the drone radio sub-system
to determine changes in the amount of power allocated on the
downlink to each ground/mobile terminal to equalize the data rate
among different terminals according to some fairness criterion; and
the drone radio sub-system to adjust the power allocated to
downlink of each ground/mobile terminal.
[0021] The TX unit of the drone radio sub-system comprises systems
and methods for: encoding each terminal's data and mapping the
coded bits onto constellation symbols; scaling the coded symbols
from each terminal destined to different antenna elements to form a
beam toward the terminal; summing the scaled coded symbols from
different terminals destined to the same antenna aperture to form
multiple beams, one toward each terminal; amplifying and
up-converting the summed signal to the appropriate frequency band;
and transmitting the resulting signal through the corresponding
antenna aperture. In another aspect of the disclosure, the drone TX
unit comprises systems and methods to choose the scaling for coded
symbols for each terminal to adjust the power sent to that terminal
on the downlink.
[0022] These and other aspects shall become apparent when
considered in light of the disclosure provided herein.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] In the following figures, similar components are identified
using the same reference label. Multiple instances of the same
component in a figure are distinguished by inserting a dash after
the reference label and adding a second reference label.
[0024] FIG. 1 is an exemplary block diagram of a drone/Unmanned
Aerial Vehicle (UAV) based broadband access to internet system.
[0025] FIG. 2A-2B are block diagrams of exemplary drone and
ground/mobile terminal radio sub-systems.
[0026] FIG. 3 is an exemplary diagram of drone based broadband
access system using multiple transmission media to provide coverage
to an area.
[0027] FIG. 4 is a flow chart illustrating an exemplary process to
adjust one or more data rates on the links between terminals and
the drone in response to rain or other atmospheric conditions.
[0028] FIG. 5 is a flow chart of an exemplary process to switch a
transmission medium between a drone and a terminal to mitigate
fading due to e.g., atmospheric conditions such as rain, fog,
and/or clouds.
[0029] FIG. 6 is a block diagram of an exemplary apparatus
configured to control transmission power on one or more downlinks
to different terminals and further configured to form beams toward
the one or more different terminals.
[0030] FIG. 7 is a flow chart of an exemplary process to adjust
power transmitted on one or more downlinks to one or more different
terminals in response to changes in atmospheric conditions such as,
e.g., rain, fog, and/or clouds.
[0031] All Figures .COPYRGT. Copyright 2014 Ubiqomm, LLC All rights
reserved.
DETAILED DESCRIPTION
[0032] Reference is now made to the drawings, wherein like numerals
refer to like parts throughout.
[0033] In view of the challenges and hurdles in both expense and
access to remote, poor or otherwise underserved regions, there
exists a need for improved broadband access. Accordingly, a system
that has much lower hardware cost, has much lower launch/deployment
cost, and is more easily scalable is needed.
[0034] Until recently drones, also known as Unmanned Aerial
Vehicles (UAVs), have been extensively used by military, as well as
for some scientific applications such as weather information
gathering. Commercial applications of drones/UAVs include package
delivery systems, video gathering systems, and communications
systems. This disclosure describes aspects of a communications
system design that are optimized for using drones/UAVs as the
communications platform. Since drones/UAVs have the capability to
fly at much lower altitudes than satellites do, such drone systems
have an exemplary benefit of not needing the expensive space
qualification of the satellite systems. Furthermore, drones/UAVs
also do not need the expensive launch systems of satellites. Since
the drone/UAV hardware cost is relatively small compared to
satellites, and there is less of a launch risk, then there is a
reduced need for additional insurance costs. Principles of the
present disclosure therefore provide high capacity drone/UAV based
broadband communication systems. As such, the relatively low cost
of the drone/UAV hardware and operation cost, and its high capacity
result in a low cost broadband delivery system.
[0035] Another exemplary advantage of a drone/UAV system configured
according to the present disclosure over satellite systems is the
low communication signal delay achievable by the drone/UAV systems.
For instance, geo-stationary satellites typically have a round trip
communication signal delay from ground to the satellite and back to
ground of about 0.5 seconds which significantly impacts the quality
of services that require low round trip delays. Even high altitude
drones/UAVs (e.g., altitudes of 25 kilometers), would typically
have a round trip communication signal delay of about 2
milliseconds to terminals on the ground for distances up to 300
kilometers from the drone. Accordingly, the low delay of drone/UAV
based system of the present disclosure may enable similar real time
quality as compared to terrestrial broadband access systems.
[0036] Another exemplary advantage of drones (configured according
to the present disclosure) is that the drones may be deployed one
at a time in areas with radiuses of 300 km or less and immediately
provide service within the drone's footprint. In contrast,
satellite systems may need to cover a wide area before service may
be provided (such as a large part of the CONUS (CONtinental US) in
the case of geo-satellite systems, or most of the earth in the case
of LEO (Low Earth Orbit) satellite systems). Therefore, drone based
systems offer improved scalability when compared to satellite
systems, as a network provider can send one drone and start service
in its footprint, test the market acceptance of the service, and
then send more drones in areas that need service. Furthermore, a
network provider could deploy the drones in only areas of the
country where there is a high demand for the service. In the
remainder of this disclosure we use the term drone to refer to both
drones and UAVs. In addition, it should be noted that principles of
the present disclosure may be equally applied to other types of
aerial vehicles. For example, blimps or balloons may be implemented
alternatively, or in addition to, the drones as discussed herein,
to provide the broadband access system. Additionally, while the
disclosed embodiments are described with respect to UAVs, it should
be appreciated by those of ordinary skill in the related arts that
drones are by no means limited to aerial operation; drones may
include watercraft, land-based vehicles, submersibles, and even
spacecraft variants, such implementations being within the skill of
an ordinary artisan, given the contents of the present
disclosure.
[0037] FIG. 1 illustrates one exemplary drone 110 configured
according to the present disclosure. In one embodiment, each drone
110 has a drone radio sub-system 112 and at least one drone
transmission medium fixture 114. The physical medium used to
transmit the information may be electromagnetic waves (e.g., radio)
in different frequency bands or Free Space Optics (FSO). The term
"transmission medium aperture" refers to an antenna aperture when
considering electromagnetic waves, and refers to an optical lens
when considering FSO. Therefore, the aperture of the transmission
medium fixture may be an antenna when using electromagnetic waves,
or an optical aperture when using FSO. As shown in FIG. 2A, the
drone radio sub-system 112 includes four (4) sub-systems: the
receiver 318 that demodulates and decodes the signal received from
an aperture of the transmission medium fixture 114; the transmitter
sub-system 316 that modulates the data received from processor 314
and sends the resulting signal through an aperture of the
transmission medium fixture 114; the processor sub-system 314 that
carries out functions such as configuring the receiver 318 and
transmitter 316 sub-systems, processing the data received from the
receiver 318 sub-system, determining the data to be transmitted
through the transmitter sub-system 316, as well as controlling the
transmission medium fixture 114; and the memory sub-system 312 that
contains program code and configuration, and system parameter
information that are accessed by the processor 318.
[0038] As shown in FIG. 2A, the radio sub-system transmitter 316
and receiver 318 sub-systems support multiple frequency bands,
F.sub.1 . . . F.sub.n, as well as FSO, and each sub-system
comprises multiple TX and RX units corresponding to each supported
frequency band F.sub.1 . . . F.sub.n or FSO. As will be discussed
below, the specific frequency band, F.sub.1 . . . F.sub.n, or FSO,
that is used for communication to a specific Ground Terminal (GT)
depends on the relative distance of the GT to the drone, as well as
the atmospheric conditions at a given time. As used herein, a
"ground terminal" may refer to a fixed terminal or a terminal on a
mobile platform such as a vehicle or an aircraft.
[0039] In one embodiment, a mechanism configured to connect the
appropriate transmitter and receiver frequency or FSO units to the
processor is disclosed. In one implementation, the radio sub-system
112 comprises a switching sub-system 315 that switches the data
from processor 314 to the appropriate radio transmitter TX unit to
modulate the data using the appropriate medium and to transmit the
modulated signal through the corresponding medium aperture.
Similarly, a switching sub-system 315 switches the data from the
appropriate RX units of the receiver sub-system 318 to the
processor sub-system 314. The transmission medium fixture 114 as
shown in FIG. 2A includes a number of apertures supporting
frequency bands F1 to Fn and FSO. The TX and RX units of the
transmitter and receiver sub-systems are connected to the aperture
corresponding to the same frequency band or FSO.
[0040] Depending on the altitude of the drone 110, each drone 110
may cover an area on the ground with a radius of tens of kilometers
to hundreds of kilometers or more. In one exemplary embodiment,
drones 110 are configured to communicate with at least three kinds
of ground terminals: one type of terminal is the Ground Terminal
(GT) 120 (see FIG. 1), such as terminals at home or enterprises to
provide internet connectivity to a home or enterprise; a second
type of terminal is installed on mobile platforms such as vehicles
or airplanes; a third type is what is referred to as the internet
Gateway (GTW) 130 which is connected to the internet. GTs 120
transmit and receive data from the internet using the drone network
as an intermediary connection to network infrastructure. The
drone's 110 radio sub-system 316 aggregates traffic received from
the GTs 120 and may aggregate traffic received from multiple GTs
120 and send the aggregated data to the internet via one of the
GTWs 130. Therefore, in one embodiment, the GTWs 130 provide higher
data rates from/to drones than the data rates provided from the GTs
120. In these embodiments, the gain of the GTW medium aperture
sub-system is larger than that of the GT 120, and the GTW 130
transmitter transmits at a higher power than the GTs 120.
[0041] As shown in FIG. 2A, drone 110 further comprises a drone
switching sub-system 116. The switching sub-system 116 may route
data received from one GT 120 to another GT 120 in the footprint of
the drone, or from one GT 120 to a GTW 130 which is in turn
connected to the internet 136.
[0042] As shown in FIG. 2B, in one embodiment, the GT 120 is
configured with two main sub-systems, a ground/mobile terminal
radio sub-system 122, and a ground/mobile terminal transmission
medium fixture 124. The GT radio sub-system 122 comprises four (4)
sub-systems: the receiver 418 that demodulates and decodes the
signal from drone medium aperture sub-system 124 the transmitter
sub-system 416 modulates the data and sends the resulting signal
through an aperture of the transmission medium fixture 124; the
processor sub-system 414 is configured to execute software to
perform various functions (such as configuring the receiver 418 and
transmitter 416 sub-systems, processing the data received from the
receiver sub-system 418, determining the data to be transmitted
through the transmitter sub-system 416, as well as controlling the
transmission medium fixture 124, etc.); and the memory sub-system
412 contains program code and configuration data, and system
parameters information that are accessed by the processor 414. The
switching sub-system 415 connects the processor to the appropriate
transmitter or receiver units of the transmitter 416 and receiver
418 sub-systems.
[0043] The link between the drones and the GTs 120 may operate in
different parts of the spectrum, F.sub.1 . . . F.sub.n, or FSO.
Since different parts of the spectrum are susceptible to
atmospheric effects to different degrees, the range of the signal
from the drone 110 to the ground terminals will depend on the
particular frequency band being used. Frequencies above 10 GHz may
suffer higher losses from rain fade than frequencies below 10 GHz;
generally, higher frequencies incur higher fades. Frequencies above
10 GHz may also incur attenuation due to atmospheric gases such as
oxygen and carbon dioxide (CO.sub.2), as well as water vapor.
Optical signals suffer primarily from fog and clouds.
[0044] In one embodiment of the present disclosure, a mechanism
that detects and mitigates the effects of atmospheric losses is
disclosed. In one variant, the disclosed mechanisms also optimize
trade-offs between frequencies and ranges (e.g., higher frequencies
have lower ranges). Specifically, different RF frequencies and
optical links have different ranges, therefore the disclosed
apparatus efficiently creates a wide coverage area using the
different available frequency and optical bands.
[0045] FIG. 3 shows an exemplary embodiment where two frequency
bands F.sub.1 and F.sub.2 and FSO are used by the drone 110 and the
GTs 120. The coverage area in the footprint of the drone 110 is
divided into a number of rings. The innermost ring that is served
by all frequency bands as well as FSO has the smallest range. The
next two rings shown in FIG. 3 may be too far for FSO to reliably
reach. As shown in FIG. 3, frequency band F1 has the largest
coverage ring. In one embodiment, F.sub.1 has a lower frequency
than F.sub.2; alternatively, the frequency band F.sub.1 may be
configured with a higher EIRP (Effective Isotopic Radiated Power)
than F.sub.2. GTs 120 in the outermost ring of the coverage area
would be served using the F.sub.1 frequency band, GTs 120 in the
ring in the middle would be served using either F.sub.1 or F.sub.2
spectrum, and GTs 120 that are in the innermost ring could be
served using F.sub.1, F.sub.2 or FSO. Note that more than two
frequency bands may be used by the drone 110 and GTs 120 and the
embodiments described in this disclosure extend to any number of
frequency bands and/or FSO, etc.
[0046] In one implementation, rain fade may be mitigated by
allocating enough link margin in the link budget for the different
frequency bands based on their fading characteristics. In some
cases, relying on allocating adequate link margin to mitigate rain
or other atmospheric effects may be undesirable (e.g., where
desired reliability would require excessive amounts of margin,
etc.) Below, additional exemplary techniques are described to
reduce the amount of link margin needed to mitigate rain and other
atmospheric effects.
[0047] In one aspect of this disclosure, the drone 110 and GT radio
sub-systems 122 measure a signal quality metric, such as SINR
(Signal to Interference plus Noise Ratio), from the received
messages from GTs (such as GTs 222, 232, and 212 shown in FIG. 1).
The data rate from/to the drone 110 is adjusted according to the
measured SINR. If the SINR received at a drone 110 or at a GT 120
degrades due to rain fade, resulting in a reduction in the data
rate between the drone 110 and the GT 120, then in one exemplary
implementation the degradation may be remedied by allocating more
time slots or more frequency to the specific affected GT 120 to
compensate for the lower data rate on the corresponding link.
Suppose, for example, that the data rate between the drone and a
specific GT 120 is reduced by a factor of four (4) due to rain
fade. If four (4) times the number of time slots is allocated to
the impacted GT 120, then the overall throughput the GT 120
experiences is the same as without any rain fade. In one variant,
if more time is allocated to a GT 120 in rain fade, then at least
some time is taken from other GTs 120. However, if only a small
fraction of GTs 120 in the footprint of a drone 110 are impacted by
atmospheric related fade, then taking time slots from other GTs 120
and allocating more time slots to the GT 120 in fade will reduce
the throughput of the GTs 120 by a very small amount. The foregoing
exemplary scheme (adjusting the number of time slots assigned to
each GT 120 according to the data rate between the GT 120 and the
drone) aims to equalize the throughput between different GTs 120
which have been assigned the same grade of service in terms of
throughput. Those of ordinary skill in the related arts, given the
contents of the present disclosure, will readily appreciate that
similar schemes may be implemented based on e.g., frequency,
spreading factors, etc.
[0048] FIG. 4 describes a flow chart of the exemplary scheme used
to adjust the amount of time allocated to the link between a GT 120
and a drone 110 in response to rain or other atmospheric effects.
In step 402, the drone 110 or GT radio sub-system 122 measures a
signal quality metric (such as SINR) based on the received
messages. Common examples of quality metrics may include without
limitation: Received Signal Strength Indication (RSSI), Signal to
Noise Ratio (SNR), Bit Error Rate (BER), Packet Error Rate (PER),
Block Error Rate (BLER), etc. In one embodiment, the drone 110 or
GT radio sub-system 122 monitors a change in the SINR between the
received messages.
[0049] The changes in signal quality metrics may be monitored
continually between the received messages and/or at periodic
intervals. In one implementation, the periodic intervals may be
dynamically changed. The periodic interval may be based on a
current measurements and/or an amount of change between
measurements (between messages and/or over a time period). For
example, signal quality measurements may be provided at different
intervals based on how quickly the signal quality changes. A
rapidly fading channel requires faster updates, whereas a
relatively stable radio link can provide less frequent updates.
[0050] In still other embodiments, the signal quality metrics may
be polled or otherwise provided as requested. For example, in
certain situations the drone 110 or GT 120 may be queried, and the
resulting collection of measurements may be used for e.g., network
optimization, initial deployment coverage assessment, handover
assessment, redundancy coverage assessment, etc.
[0051] In step 404, the GT radio sub-system 122 sends the signal
quality metric on the uplink to the drone radio sub-system 112. In
one embodiment, the measured signal quality metric may be sent on
the uplink on a periodic basis to the drone radio sub-system 112 or
sent when the measured signal quality metric exceeds one or more
threshold values. In one implementation, the measured signal
quality metric comprises the measured SINR of one or more
previously received messages. In another variant, the measured
signal quality metric comprises a running average of SINR over
multiple received messages.
[0052] In other embodiments, the drone radio sub-system 112 sends
the signal quality metric on the downlink to the GT radio
sub-system 122. Similarly, the measured signal quality metric may
be sent on the downlink on a periodic basis to the GT radio
sub-system 122 or sent when the measured signal quality metric
exceeds one or more threshold values.
[0053] In step 406, the drone radio sub-system 112 or GT radio
subsystem 122 determines the effective performance that the GT 120
or drone 110 will receive (or can be expected to receive), based on
the measured signal quality. Common examples of performance may
include e.g., the amount of data (e.g., throughput), the delay in
data (e.g., latency), retransmission metrics, predicted BER (or
PER, BLER), etc. By determining the effective performance, the
drone radio sub-system 112 or GT radio subsystem 122 can determine
whether the radio link is adversely impacted by atmospheric
effects.
[0054] In some embodiments, the drone radio sub-system 112 or GT
radio subsystem 122 may additionally consider other factors in
addition to effective performance. For example, such factors may
include e.g., historic performance (e.g., based on time of day
and/or position), the rate of change of performance (e.g., to
detect impending fast fading), known network traffic demands (e.g.,
peak hour demands, etc.)
[0055] In step 408, the drone radio sub-system 112 or GT radio
subsystem 122 determines the amount of additional resources that
must be allocated to the radio link. For example, a drone radio
sub-system 112 may mitigate atmospheric effects in order to provide
a similar grade of service for an impacted GT 120 as other GTs 120
with the same promised grade of service.
[0056] Those of ordinary skill in the related arts will readily
appreciate that "resources" are broadly used to refer to any
physical or virtual element of limited availability within the
network. Common examples of resources include e.g., time slots,
frequency bands, spreading codes, bandwidth, transmission power,
etc. In one embodiment, the additional resources are allocated
using one or more fairness criterion. In one implementation,
fairness criterion refers to the scheme for allocating an amount of
resources to different terminals. One exemplary fairness criterion,
referred to as "equal grade of service" scheduling, attempts to
provide the same average throughput to all terminals. To achieve
equal grade of service more time is allocated to terminals that
have lower signal quality and/or which receive data at lower data
rates. Another exemplary fairness criterion referred to as "equal
grade of time" scheduling allocates the same amount of time to
multiple GTs 120. In equal grade of time scheduling, different GTs
120 will receive different average data throughputs commensurate
with their received signal quality.
[0057] In some implementations, the allocation can take effect
immediately. Alternatively, in some implementations, an appropriate
time for the allocation to take effect must be determined. For
example, in some instances, the radio link between the drone and/or
GT is subject to broader network or usage considerations such as
e.g., network traffic, neighboring interference and/or other radio
links, etc. Under such conditions, the drone and/or GT must
coordinate the allocation so as to e.g., minimize impact on
neighbors, or optimize overall benefits gained.
[0058] In step 410, the drone radio sub-system 112 or GT radio
subsystem 122 changes the scheduler parameters that determine how
many resources are allocated to each GT 120. Responsively, the
communication between the drone 110 and each GT 120 is configured
in accordance with the scheduled parameters, and thereafter the
allocation can take effect. In some embodiments the allocation
change may occur at e.g., a prescribed effective time (e.g., via a
time stamp), at a predetermined time (e.g., at the start of the
next cycle, frame, etc.), responsive to a trigger event (such as
signaling), etc.
[0059] While the foregoing example is presented with respect to a
drone radio sub-system 112 and a GT radio subsystem 122, the
concepts described therein can be generalized to a network of
multiple drones and/or GTs. Moreover, it should be further
appreciated by those of ordinary skill in the related arts given
the contents of the present disclosure, that various steps of the
method may be performed by other entities; for example, an
evaluation of fairness criterion may be performed by a drone or GT
network controller, etc.
[0060] Another exemplary method may mitigate atmospheric fade by
switching a terminal that is operating at a higher frequency band
to a lower frequency band. As previously noted, different frequency
bands have different susceptibility to atmospheric effects. For
example, a terminal using the higher frequency F.sub.2 that is
experiencing excessive rain fade is configured to switch to a lower
frequency band F.sub.1 (or another frequency with more rain fade
margin). The GT radio sub-system 122 makes measurements of a signal
quality metric such as SINR (Signal to Interference plus Noise
Ratio) on the received messages from the drone 110 and reports the
measured SINR or another signal quality to the drone radio
sub-system 112. In one implementation, if the measured SINR falls
below a certain threshold, then the drone radio sub-system 112 may
initiate switching the communication link to the second frequency
band F.sub.1 by sending a message configured to inform the GT 120,
of the switch to the alternative frequency. Since the second
frequency incurs less rain fade, the link quality will improve by
switching to a second frequency. Note that the drone radio
sub-system 112 may also decide to switch the operating frequency to
a second frequency based on the SINR or another signal quality
metric measurement at the drone receiver. Similarly, with regards
to FSO which suffers from fog and clouds, the system will switch
from FSO to a radio frequency mode, F.sub.1 or F.sub.2 when the
fade in FSO mode is excessive. This hybrid drone radio sub-system
construction allows use of multiple transmission media in order to
provide high throughput, and at the same time optimizes the use of
each medium according to the rain and other atmospheric conditions.
Note that switching the GTs 120 to the medium that has the least
rain/atmospheric loss at a given time also allows the system to
maximize the overall system throughput.
[0061] FIG. 5 is a flow chart of an exemplary mechanism useful for
detecting rain and other atmospheric fades, and to switch the
transmission medium to a second medium. In step 502, the drone
radio sub-system 112 or GT radio subsystem 122 measures a signal
quality metric, such as SINR. The signal quality metric is measured
from one or more communications between the drone and the GT. The
measured signal quality metric may be measured from one or more
particular types of received messages. Alternatively, the signal
quality metric may be measured on any message received at a
determined periodic interval. The periodic interval may be set as a
predetermined time or may be configured to dynamically change based
on one or more parameters. In one such implementation, the periodic
interval is changed based at least in part on the measured signal
quality metric.
[0062] In step 504, the measured signal quality metric is reported
to the drone radio sub-system 112 or GT radio subsystem 122. The
reported measured signal quality metric may comprise a measurement
of a particular communication itself or may comprise a change in a
measured signal quality metric. The GT radio sub-system 122 may be
configured to report the measured SINR on a periodic basis,
reported upon the measured SINR exceed a threshold, or a
combination of both. In one implementation, the periodic basis is
configured to dynamically change based at least in part on the
value of the measured and/or reported SINR.
[0063] In step 506, the drone radio sub-system 112 or GT radio
subsystem 122 determines whether the measured signal quality metric
is below a certain threshold indicating excessive fade due to rain,
fog, cloud or other effects. If the measured signal quality metric
is below a threshold then the drone radio sub-system 112 or GT
radio subsystem 122 switches the transmission medium to an
alternate transmission medium (e.g., from F.sub.2 to F.sub.1, or
from FSO to a radio frequency mode, F.sub.1 or F.sub.2). In some
embodiments, the drone radio sub-system 112 or GT radio subsystem
122 requests that the transmission medium be switched (causing
another supervisory entity to responsively perform the switch). For
example, the drone radio subsystem 112 may decide to request a
transmission medium change based on uplink SINR measurements at the
drone receiver. Alternatively, the GT radio subsystem 122 may
request a switch of the transmission medium based on the downlink
SINR measurement by sending a message to the drone 110 with
information on the new transmission medium and the time to switch
to the new medium. One exemplary benefit of having the drone 110
decide when to switch transmission medium, as shown in FIG. 5, is
that the drone may have information on all traffic and thus may be
better suited to schedule GTs 120 on different media, while
balancing the traffic among different media. It is appreciated
however, that in GT initiated embodiments, the GT 120 may have
information which the drone 110 may not be aware of (e.g.,
application requirements, etc.) In still other embodiments, a core
network entity may manage connectivity, handovers, etc.
[0064] Another aspect of the present disclosure is the use power
control to mitigate effects of atmospheric fade on the downlink. In
one exemplary embodiment of the drone radio and transmission medium
fixture design, the drone radio sub-system 112 and each antenna
aperture for each frequency generate multiple beams to different
GTs 120. The total power transmitted by an antenna aperture is
configured to be sharable among the multiple beams formed toward
different GTs 120. The GTs 120 served by a drone 110 may be located
in a wide geographic area where all GTs 120 are not simultaneously
affected by e.g., rain. When some GTs 120 experience atmospheric
fade, the drone radio sub-system 112 may allocate more power to the
downlink on the beam toward the affected GT 120. The GT radio
sub-system 122 measures SINR received on the downlink pilot signals
and reports the measured values to the drone 110 in signaling
messages sent to the drone 110 on the uplink. The drone radio
sub-system 112 determines the amount of rain fade based on the
expected SINR values in absence of rain. The drone radio sub-system
112 then may increase the power allocated to the downlink of the
affected GTs 120 (i.e., whose received SINR have decreased due to
rain fade). Note that even in the power control scheme just
described, in one exemplary implementation, certain power margins
are allocated in the link budget of the downlink from the drone 110
in order to compensate for rain fade. However, using power control
and allocating more power only on the downlink beams to GTs 120 in
rain fade, the rain fade margin in effect is shared among different
GTs 120, and therefore may result in less link margin being
allocated to rain fade as compared to a scheme where each downlink
is allocated its own dedicated rain fade margin. The power control
based rain fade mitigation scheme, therefore, may significantly
reduce the required rain fade margin, thereby resulting in a more
efficient system. The above mentioned exemplary power control based
rain fade mitigation scheme may increase effectiveness in streaming
services where the traffic mainly flows on the downlink to the
terminal.
[0065] FIG. 6 is a block diagram of an exemplary modulation and
power control sub-system for the transmitter (TX) unit of FIGS. 2A
and 2B. In one embodiment, the parameters of FIG. 6 are configured
such that antenna beams are formed simultaneously toward as many as
M terminals using an antenna aperture comprised of N antenna
elements. Those of ordinary skill in the related arts, given the
contents of the present disclosure, will readily appreciate that
other antenna configurations may be used, the foregoing
configuration being purely illustrative. The data for the j-th
terminal is encoded using error correction coding block 610-j, and
then mapped onto constellation symbols in block 612-j, as shown for
terminals 1 and M. Coded data symbols for the j-th terminal,
denoted by S.sub.j, are scaled by coefficients C.sub.jk where k is
the index of the antenna element. Coefficients C.sub.jk are
designed to form beams toward each terminal. The scaled symbols
from different terminals that are destined to the same antenna
element are then summed using the summing device 614-k, where k is
the index of the summer corresponding to the k-th antenna element.
The output of the summer 614-kis then amplified and up converted
using block 616-k and then sent to antenna element 618-k.
[0066] FIG. 7 is a flow chart of an exemplary power control based
mechanism to mitigate rain fade. In step 702, the GT radio
sub-system 122 measures received SINR or some other signal quality
metric from the pilot signals on the downlink. In step 704, the GT
radio sub-system 122 sends the measured SINR to the drone radio
sub-system 112 in a message on the uplink. In step 706, the drone
radio sub-system 112 compares the received SINR measurement from
the GT 120 against a target SINR. If the measured SINR is smaller
than the target, then in step 708 the drone radio sub-system 112
increases the power on the downlink to the specified GT 120. If the
measured SINR is above the target, then in step 710 the drone radio
sub-system 112 decreases the power on the downlink to the specified
GT 120.
[0067] It will be recognized that while certain aspects of the
disclosure are described in terms of a specific sequence of steps
of a method, these descriptions are only illustrative of the
broader methods of the disclosure, and may be modified as required
by the particular application. Certain steps may be rendered
unnecessary or optional under certain circumstances. Additionally,
certain steps or functionality may be added to the disclosed
embodiments, or the order of performance of two or more steps
permuted. All such variations are considered to be encompassed
within the disclosure disclosed and claimed herein.
[0068] While the above detailed description has shown, described,
and pointed out novel features of the disclosure as applied to
various embodiments, it will be understood that various omissions,
substitutions, and changes in the form and details of the device or
process illustrated may be made by those skilled in the art without
departing from the disclosure. This description is in no way meant
to be limiting, but rather should be taken as illustrative of the
general principles of the disclosure. The scope of the disclosure
should be determined with reference to the claims.
* * * * *