WO1999013598A1

WO1999013598A1 - Wireless communication using atmospheric platform

Info

Publication number: WO1999013598A1
Application number: PCT/US1998/018670
Authority: WO
Inventors: Peter H. Diamandis; Marc Arnold; Nicholas J. Colella
Original assignee: Angel Technologies Corporation
Priority date: 1997-09-08
Filing date: 1998-09-08
Publication date: 1999-03-18
Also published as: TW421935B; AU9380298A; WO1999013598B1

Abstract

A communication system is provided in which an airborne atmospheric platform located in the Earth's atmosphere communicates with a network of satellites and with ground-based users. Because of its location in the atmosphere, the atmospheric platform takes advantages of previously unused high frequencies in communicating with the satellite network. The atmospheric platform communicates with ground-based users at a second, lower frequency.

Description

Wireless Communication Using Atmospheric Platform

FTELD OF THE INVENTION

The present invention is directed to a system and method for providing wireless

communications through the use of atmospheric platforms stationed between a satellite

network and Earth-bound users in order to provide connectivity between any two

Earth-bound users anywhere on the planet. The present invention is particularly

advantageous when employed in wireless broadband communication systems and

wireless telephony communication systems.

BACKGROUND OF THE TNNENTIQN

Over the last two decades, the worldwide appetite for timely information and

effective communications services has grown tremendously. In recent years, new

forms of communications services and technologies have become well-known (e.g.,

the Internet, faxes, modems, pagers, cell phones, etc.). In parallel with the increase in

demand, new forms of technology have been developed to deliver voice, data, sound

and video at ever increasing speed and decreasing costs.

The broadband communications market segment is the most recent to explode

in demand. Simply stated, a broadband communications system is one which is able

to provide any two users with bit rates sufficient for high-speed data and video. At the

time of the present invention, broadband is defined as multi-megabit per second rates

(e.g., speeds greater than 1 Megabit/second), which are far in excess of the multi-

kilobit per second rates (for example, 28.8 kbps) currently supported by the telephone networks. An analogy can be made to a pipe carrying water. A narrow pipe cannot

convey a very large quantity of water in a short period of time. However, a very large

pipe can move significantly more water in the same amount of time. A broadband

communications system is similar to a very wide pipe in the sense that it can move the required volume (or bits) per unit time of information efficiently. ^{~~ *}

Currently, consumers and businesses are demanding the ability to connect with

other users within their city and outside their city at high data rates (multi-megabit per

second data rates, for example) in order to transmit and receive video, data and

images.

Broadband communications is currently provided through either wired or

wireless means. In a wired broadband system, communication between parties is

facilitated by a physical connection, either through a cable plant, the telephone

network (i.e. twisted copper pair), or optical fiber. While wired broadband solutions

can be highly reliable, they are often too expensive to install and are typically

regionally deployed. Therefore, wired broadband systems therefore cannot readily

service a widespread community of subscribers.

Several types of wireless broadband solutions currently exist. One type of

wireless broadband communications system involves terrestrial towers. According to

this approach, multiple towers are installed around a region to be served, each tower

serving a particular area of users. Wireless signals are transmitted from tower to tower, thereby facilitating broadband communications between users. An example of such a tower-based system currently in use is called Local Multipoint Delivery System (LMDS). Tower-based wireless broadband solutions suffer from an important disadvantage. Namely, tower-based solutions only provide local coverage on the

order of city blocks. Although many towers can be used to support large population of

users, multiple towers are expensive to install, undesirable to view and require high capacity data communication lines to interconnect towers. - -- . -_

Another type of wireless broadband communications system uses satellites to

communicate directly with Earth-bound users. Several types of satellites are used in

these types of systems. Satellite-based broadband can be supported from Low-Earth

orbit (LEO), medium-Earth orbit (MEO), highly elliptical orbit (HEO) or

geostationary Earth orbit (GEO) satellites. Satellite-based wireless broadband systems

offer the benefit of providing large area coverage (unlike terrestrial solutions), but

suffer from four major limitations. Specifically, satellite-based wireless broadband

systems (1) are power limited; (2) are stationed at great distance from the end user; (3)

require transmission through the entire atmosphere in order to reach their target user;

and, (4) are limited because of power and distance to the number of users they can

serve per area, and cannot therefore serve high density population centers effectively.

Another segment of the communications market experiencing unprecedented

growth is wireless telephony. Two modes currently are used for wireless telephony:

wireless telephony for mobile users (known as cellular or PCS) and wireless telephony

to homes or businesses (known as fixed wireless telephony or wireless local loop). In

most of the developed world, mobile wireless telephony is growing at high rates. To

support the increased demand, it is currently necessary to erect towers or place antennas on the tops of buildings such that a typical city requires hundreds of towers or antenna sites in order to provide sufficient coverage and capacity. These towers are expensive to build and are limited in that they establish fixed service locations and

require costly modification as populations shift and market demands change.

Fixed wireless telephony enjoys particular application in developing countries, -

where wired telephony infrastructure does not exist. The quickest and easiest way to

provide the population of those countries with basic telephone service is via wireless

telephony. Wireless telephony eliminates the need to bury cable or string wire.

Currently, wireless telephony in areas without a wired telephony infrastructure is

supported by establishing either a terrestrial tower-based system, which suffer from

the same disadvantages noted above.

Therefore, a need exists for a more efficient and effective system and method

of providing communications services to users.

SUMMARY OF THE INVENTION

According to the present invention, atmospheric platforms can be used for providing wireless communications services, for example, to 'super-metropolitan

areas' which are 10's to 100's of miles in diameter. Atmospheric platforms have the

advantage of ample power. Such platforms can operate above most commercial air

traffic and weather, and above most of the atmosphere and its moisture. From this

altitude they are also able to communicate with various satellites in various orbits. Also because of their altitude, the atmospheric platforms are able to use high frequency links for "atmospheric platform to satellite" linkages because of the clear line of sight and lack of scattering and absorption. The connectivity between terrestrial users, atmospheric platforms and satellites are the basis for this invention

and offer unique communications architectures for transacting data, images, sound, video and video-telecόnferencing worldwide. - -- - --

More specifically, according to the present invention, an atmospheric platform

services a footprint of Earth-bound users and communicates with the users via

wireless means. The atmospheric platform also communicates with a satellite

constellation orbiting the Earth, again through wireless means. The atmospheric

platform is located in the upper regions of the Earth's atmosphere, above the altitude

bands of commercial civilian aviation and adverse weather. Because of the height of

the atmospheric platform above the Earth, it is able to communicate with the satellite at high frequencies that are practically unusable for broadband communications

between a satellite and a terrestrial user. Such high frequencies would typically be

distorted and attenuated by rainfall and atmospheric gases. Having an atmospheric

platform placed in the upper atmosphere allows the atmospheric platform to utilize

high frequencies in communications with the satellite and then communicate with the Earth-based users with lower frequencies. Such a combination of satellites and

atmospheric platforms allows for data to be transacted more efficiently between any

two users on the planet than was possible with older prior art systems. The present

invention is particularly useful in broadband data communications systems and

wireless telephony systems, both mobile and fixed. BRIEF DESCRIPTION OF THE FTGURES

Figure 1 is a diagram depicting a first embodiment of the present invention.

Figure 2 is a diagram depicting communication between users in different

footprints according to the first embodiment of the present invention. -

Figure 3 is a diagram illustrating the advantages obtained according to the first

embodiment of the present invention.

Figure 4 is a diagram depicting a second embodiment of the present invention.

Figure 5 is a diagram depicting a third embodiment of the present invention.

Figure 6 is a diagram depicting particular advantages of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

According to the present invention, atmospheric platforms are used in

conjunction with a satellite network in order to facilitate communications between

ground-based users. Referring to Figure 1, a communication system is provided in

which ground-based users 103 can be interconnected in a manner which allows them

to communicate using very high data rates. The system of Figure 1 includes an

atmospheric platform 102 which is located above the Earth in the upper region of the

atmosphere. More specifically, the location of atmospheric platform 102 must be

above the flight corridors of commercial and general aviation air traffic and above

significant weather. It is preferred that the atmospheric platform 102 be located at

least 52,000 feet above ground. Also shown in Figure 1 are satellites 101 which orbit

the Earth and communicate with atmospheric platform 102. Atmospheric platform 102 is capable of communicating with a multitude of satellites 101 interconnected by

intersatellite linkages 105. These intersatellite linkages 105 typically utilize wide

swaths of spectrum at higher frequencies to interconnect such satellites.

The operation of the system depicted in Figure 1 will first be described for the

situation in which users within the same "cone of commerce" or "foOtprint"

communicate with each other. Users within the same "cone of commerce" or

"footprint" are those users 103 which are served by the same atmospheric platform

102. Referring to the figure, if user 103-1 wishes to communicate with user 103-2,

user 103-1 sends a wireless signal 107 to the atmospheric platform 102. The

frequency of the signal 107 between the atmospheric platform and the user must be

such that the signal has acceptable propagation characteristics in the atmosphere. The

signal 107 may be attenuated too strongly by rain droplets and atmospheric gases. In a

wireless broadband communication system, it is preferred that the frequency of the

signals 107 be well under 60 GHz. In a wireless telephony system, it is preferred that

the frequency of signals 107 be less than 10 GHz.

Next, the atmospheric platform communicates either directly with the other

user, here user 103-2, or with a gateway 104. Gateway 104 is connected either to the

public switched telephone network or to a fiber backbone which provides access, for

example, to the Internet.

Users 103 can communicate with other users outside of their own footprint by

one of two methods. As in the example, user 103-1 wishing to communicate with

another user outside of his or her own footprint first sends a message to its local atmospheric platform 102. Then, the atmospheric platform sends a wireless signal 107

to a gateway 104, again connected to either the public switched telephone network or to a fiber backbone connected to the Internet.

A second way for a user to communicate outside his or her own footprint is

depicted in Figure 2. A user 206 communicates via signal 211 (having a frequency ^~~

appropriate for terrestrial wireless applications as signal 107 described with respect to

Figure 1) to an atmospheric platform 200. The atmospheric platform 200 in turn

communicates via wireless signal 212 with a satellite 201. Significantly, signal 212

can utilize a higher frequency as compared to the frequency of signals between the

atrnospheric platform and a user (i.e., signals 211 in Figure 2 and signals 107 in Figure

1). Satellite 201 is one of several in a collection of satellites. At any given time, each

satellite has an associated atmospheric platform which services a unique footprint

containing users. In the present example, satellite 201 communicates via intersatellite

linkage or wireless signal 202 through satellite 203 to satellite 204. Satellite 204 then

communicates via wireless signal 212 with its associated atmospheric platform 205.

Atmospheric platform 205 services the user 209 with whom user 206 wishes to

communicate. Atmospheric platform 205 communicates via wireless signal 211 to

user 209 in footprint 210, thus effecting communication between users in different

footprints. In this way, communication traffic can be "backhauled" or moved between

different points contained in different footprints.

Atmospheric platforms (for example, platform 102 in Figure 1; platforms 200,

205 in Figure 2; and platform 304 in Figure 3) in accordance with the present invention can be any device which remains airborne above commercial and general aviation air traffic (approximately, 52,000 feet or higher) and which is capable of

physically supporting a wireless telecommunications payload. The atmospheric

platform must be able to supply the payload with sufficient power, environmental control and thermal conditioning over a designated location or a designated flight path ^~ In other words, the atmospheric platform must be capable of station-keeping; it

cannot be a free-floating device. Preferably, the atmospheric platform according to

the present invention includes an antenna array, a power generation capability, on¬

board digital switching, receive and transmit radios, a power-distribution bus, and

environmental control and conditioning. As previously described, the atmospheric

platform must be positioned at an altitude above commercial and general aviation and

adverse weather, for example, approximately 52,000 feet. However, it is possible that

a Concorde aircraft or an unusual storm might occasionally be found at that altitude.

Such occasional occurrences by aviation and/or adverse weather are not detrimental to

the present invention as long as the atmospheric platform is at an altitude where such

occurrences are rare. The acceptable height above the Earth for placement of the

atmospheric platform is dependent on the season, latitude and geography being

considered. For example, it is possible to effectively operate the atmospheric platform

at a lower altitude over polar regions as opposed to tropical regions where the weather

(the tropopause) reaches higher into the atmosphere. So, for example, the atmospheric

platform could be a lighter than air craft, for example, a balloon, or the atmospheric

platform could be an airplane. Preferably, the atmospheric platform is a high altitude long operation (HALO) aircraft which travels above the Earth at the required altitude in an a circle having a radius less than 5 miles.

The atmospheric platform of the present invention includes onboard digital

switching. Referring to Figure 2, the user 206 can communicate with atmospheric platform 200 via wireless signal 211. The atmospheric platform 200 carries on board ^~-

a digital switch 213 which can decide where the bits of data are to be sent. For

example, the information transmitted by user 206 via signal 211 to atmospheric

platform 200 can either stay within the footprint 208 and be sent to user 2Q7, or the

information can be sent out of the network via signal 112 which communicates to satellite 201.

Employing an atmospheric platform between the satellite and the ground offers

particular advantages according to the present invention. First, referring to Figure 3,

the present invention allows the satellite 301 and the atmospheric platform 304 to

communicate via signal 303 which has a very high frequency, typically at 60-90 GHz

or much higher such as laser light. These very high frequency signals are strongly

degraded by the atmosphere and therefore were not used with the prior art methods,

for example, where a satellite communicated directly with the ground. Therefore, the

present invention effectively utilizes previously unused higher frequencies in which

considerable bandwidth is available. Once the satellite 301 interconnects with the atmospheric platform 304 at the high-frequency signals 303, atmospheric platform 304

can then use its own onboard power and antenna to essentially repeat or magnify

signals at lower frequencies to communicate with ground based users. Further, according to the present invention, the atmospheric platform, because of its abundant power, large antenna array and proximity to the ground is able to

project a frequency reuse pattern through a multi-beam cellular pattern 306 and

through dedicated spot beams within the given footprint 305. A frequency reuse pattern is a well known method of making efficient usage of spectrum. The number-

and size of the beams in a frequency reuse pattern is a function of the platform

altitude, antenna array size, frequency used, available power, and the switching and

network management capabilities. The amount of throughput between a terrestrial

user and an atmospheric platform can be much higher per unit area than between a

terrestrial user and a satellite.

Figure 4 illustrates a second, preferred embodiment of the present invention.

As shown in Figure 4, an ideal configuration for the present invention includes a ring

of satellites around the Earth's equator containing of 5 - 8 satelhtes 401 at an altitude

band of 6000 - 12,000 km above the Earth. A minimum of five (5) satelhtes is

required in the ring. Five satelhtes in the ring permits failure of one satellite while

allowing the remaining satellites to communicate with each other. Ideally, the ring

should contain six (6) satellites. With a ring of six satelhtes, every airborne

atmospheric platform 404 is able to "see" at least two satellites at a given time. Eight

(8) satelhtes in the ring allows for spare satellites. The system of Figure 4, with satellites at approximately at 9,000 km above the

Earth provides coverage for +/- 50 degrees of latitude, i.e., it is high enough to cover most of the Earth's populated regions without incurring significant round-trip time delays due to the distance between the atmospheric platform and the satellite.

In a preferred embodiment, the addition of atmospheric platforms to the

satellite ring around the equator, in effect, allows the footprint of the satellite system

to be extended. Referring to Figure 6, satellite 601, positioned above the Earth at the ^~~

equator, is able to communicate directly with locations covered by the footprint

indicated by reference number 602. The size of this footprint is determined by the

minimum "look angle" indicated by reference number 603. The typical minimum look

angle is 5 to 10 degrees, which for a satellite at an altitude of approximately 9,000

kilometers would provide communications to +/- 50 degrees latitude. This mtnimnm

look angle, and therefore the footprint size, is limited in order to set the maximum

amount of atmosphere through which the satellite signal must propagate. However, satellite 601 can readily communicate with atmospheric platform 604, which is outside

of the footprint because signals traveling between the satellite and the atmospheric

platform are not as strongly attenuated by the thin, dry atmosphere at altitudes above

52,000 feet. Atmospheric platform 604 can now communicate with users within its

own footprint, which is significantly outside of the satellite's footprint 602. Therefore,

the preferred embodiment as described effectively allows the footprint of satellite 601

to be increased through the use of atmospheric platforms outside of the range of the sateUite's own footprint. While Figure 6 shows only one atmospheric platform 604, in

typical practice, multiple atmospheric platforms would be used. A third embodiment is found in Figure 5 which illustrates a highly elliptical system. Because most of the Earth's population is in the northern latitudes, highly eUiptical satellite orbits with apogees above the northern region of Earth, provide

exceUent coverage over these regions. In other words, the loiter time for the sateUites

502 shown in Figure 5 are greatest above the northern latitudes, thus aUowing

effective service to the Earth's most populated regions. Though Figure 5 shows only

two eUiptical orbits populated by multiple satelhtes, multiple elliptical sateUite orbits

populated by satellites could be employed to serve northern latitudes.

Several types of elliptical orbit can be used. For example, Molniya orbits

which cause the satellite to travel very close to the Earth (less than 1,000 kUometers)

when passing the southern-most region of the globe and very high above the Earth

(approximately 40,000 kilometers) when passing over the northern-most regions.

Other eUiptical orbits, not as extreme as Molniya orbits, have so-called apogees on the

order of 6,000 - 10,000 kilometers. These types of orbits can also be used with the

present invention.

The present invention is not limited to the particular embodiments described

above which have been chosen to illustrate the invention, with reference to the

accompanying drawings.

Claims

WE CLAIM:

1. A communication system comprising:

a pluratity of ground-based users;

at least one sateUite traveling in an orbit around the Earth;

at least one airborne atmospheric platform located above said plurality of ground-based users and below the altitude of at least one sateUite;

wherein said atmospheric platform communicates via wireless signals

with said at least one sateUite and said ground-based users.

2. The communication system of claim 1 wherein said atmospheric

platform conmiunicates with said at least one sateUite utilizing a first frequency band

and with said ground-based users through a second frequency band.

3. The communication system of claim 2 wherein said first frequency band

is shifted higher than said second frequency band.

4. The communication system of claim 2 wherein said first frequency band

is greater than 50 GHz and said second frequency band is less than 50 GHz.

5. The communication system of claim 2 wherein said first frequency band

is greater than 60 GHz and said second frequency band is less than 60 GHz.

6. The communication system of claim 4 wherein said first frequency band is less than 100 GHz.

7. The communication system of claim 6 wherein said second frequency band is higher than 100 MHz.

8. The communication system of claim 1 wherein said communication

system is a wireless broadband communication system.

9. The communication system of claim 1 wherein said communication

system is a wireless telephony communication system.

10. The communication system of claim 4 wherein said first frequency band

is at laser wave lengths.

11. The communication system of claim 1 wherein said atmospheric

platform communicates with said at least one sateUite at a frequency not practicaUy

aUowing sufficient signal strength to rehably communicate in said communication system.

12. The communication system of claim 11 wherein said atmospheric

platform communicates with said ground-based users at a frequency capable of passing through the atmosphere with sufficient reliability for use in said communication system.

13. The communication system of claim 1 further comprising at least one -

gateway which is connected to terrestrial communications networks.

14. The communication system of claim 1 wherein said atmospheric

platform is located in the Earth's atmosphere.

15. The communication system of claim 14 wherein said atmospheric

platform is located at an altitude higher than most commercial and general aviation.

16. The communication system of claim 15 wherein said atmospheric

platform is located at an altitude higher than substantiaUy aU adverse weather.

17. The communication system of claim 14 wherein said atmospheric

platform is located at an altitude of at least 52,000 feet above MSL (mean sea level).

18. The communication system of claim 1 wherein said atmospheric

platform is a lighter than air craft.

19. The communication system of claim 1 wherein said atmospheric platform is a high altitude long operation aircraft.

20. The communication system of claim 19 wherein said high altitude long

operation aircraft is pUoted.

21. The communication system of claim 19 wherein said high altitude long

operation aircraft is unpttoted.

22. The communication system of claim 19 wherein said high altitude long

operation aircraft travels in a circle having a radius less than approximately 5 miles.

23. The communication system of claim 1 wherein said atmospheric

platform carries means for routing said wireless signals.

24. The communication system of claim 23 wherein said means for routing

comprises a data communications switch.

25. A communication system for interconnecting a plurahty of ground-based

users, comprising: a network of sateUites orbiting the Earth at the equator; a plurahty of airborne atmospheric platforms located between said network of satelhtes and said ground-based users, said plurahty of airborne atmospheric platforms communicating with said network of satelhtes and said ground- based users.

26. The communication system of claim 25 wherein said network of

satelhtes includes five to eight satelhtes at an altitude of approximately 6,000 to 9,000 km above the Earth.

27. The communication system of claim 25 wherein said network of

satelhtes includes six satellites.

28. A communication system for interconnecting a plurahty of ground-based

users, comprising:

a network of satelhtes orbiting in an eUiptical orbit;

a plurahty of airborne atmospheric platforms located between said

network of satelhtes and said ground-based users, said plurahty of airborne

atmospheric platforms communicating with said network of satelhtes and said ground-

based users.

29. A method of increasing the effective footprint of a satellite, comprising: providing at least one satellite orbiting above the Earth; providing at least one ground-based user at a location outside of the footprint of said sateUite;

providing at least one airborne atmospheric platform capable of

communicating with said^t least one sateUite and said at least one ground-based user;

transmitting a first signal from said at least one sateUite to said at least

one atmospheric platform;

transmitting a second signal related to said first signal from said at least

one atmospheric platform to said at least one ground-based user.

30. A method for providing broadband communications to a plurahty of

ground-based users, comprising:

providing at least one sateUite orbiting above the Earth;

providing at least one airborne atmospheric platform capable of

communicating with said at least one sateUite and said plurahty of ground-based users;

transmitting a first signal from said at least one sateUite to said at least

one atmospheric platform;

transmitting a second signal related to said first signal from said at least

one atmospheric platform to at least one of said plurahty of ground-based users.

31. An atmospheric platform for use in a communication system, said

atmospheric platform providing a communication link between ground-based users

and orbiting satellites, wherein said atmospheric platform communicates with said satelhtes at a first frequency band and said ground-based users at a second frequency band.

32. The atmospheric platform of claim 31 wherein said first frequency band

is higher than said second frequency band.

33. The atmospheric platform of claim 32 wherein said first frequency band is less than 100 GHz.

34. The atmospheric platform of claim 33 wherein said second frequency band is above 100 MHz.

35. The atmospheric platform of claim 31 further comprising:

a power generation unit;

data communication switching means for routing signals through said

communications link;

receive and transmit radios;

a power distribution system;

environmental control; and

thermal conditioning means.