halo network by risvan new
TRANSCRIPT
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ABSTRACTScaled Composites Incorporated, a partner of Angel Technologies Corporation
(www.broadband.com), has recently built and will soon flight test a High Altitude Long
Operation (HALO) airplane specially engineered for providing wireless communications
networks. The HALO airplane has a fixed-wing airframe with twin turbofan propulsion. It
will be FAA certified for piloted operation. Its high altitude flight regime was pioneered
in the 1950s and its components will benefit from decades of aerospace industry
experience and innovation.
The HALO Network will serve tens of thousands of subscribers within a super-metropolitan area, by offering ubiquitous access throughout the networks signal
"footprint". The HALO aircraft will carry the "hub" of a wireless network having a star
topology. The initial HALO Network is expected to provide a raw bit capacity exceeding
16 Gbps, which by utilizing packet-switching could, for example, serve 50,000 to 100,000
subscribers requiring links with DS1-equivalent peak data rates in both directions. Three
HALO aircraft will fly in shifts to provide continuous service, 24 hour per day by 7 days
per week, with an overall system reliability of 99.9% or greater. The HALO airplane willfly above commercial airline traffic and adverse weather at altitudes higher than 51,000
and will provide a communications service footprint or "Cone of Commerce" of
approximately 120 kilometers in diameter. Any subscriber within that region will be able
to access the HALO Networks ubiquitous multi-gigabit per second "bit cloud" upon
demand.
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CONTENTS1. INTRODUCTION TO HALO NETWORK 01
2. HALO NETWORK 04
3. NETWORK SERVICES 07
4. HALO NETWORK ARCHITECTURE 07
5. HALO AIRCRAFT 10
6.COMMUNICATIONS PAYLOAD 137. APPLICATIONS 18
8. FUTURE PLANS 19
9. ADVANTAGES 22
10. CONCLUTION 23
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INTRODUCTION TO HALO NETWORKThe word on just about every Internet user's lips these days is "broadband." We
have so much more data to send and download today, including audio files, video files
and photos, that it's clogging our wimpy modems. There's a new type of service being
developed that will take broadband into the air.
The communication payload of HALO aircraft is at the apex of a wireless super-
metropolitan area network. The links are wireless, broadband and line of sight.
Subscribers access service on demand and will be able to exchange video, high-resolution
images, and large data files. Information addressed to non-subscribers or to recipients
beyond the regions served by the HALO network will be routed through the dedicated
HALO Gateway connected to the public switched network or via business premise
equipment owned and operated by service providers connected to the public networks.
The fig. shows angel technology.
This diagram shows how the HALO Network will enable a high-speed wireless Internet
connection
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At least three companies are planning to provide high-speed wireless Internet
connection by placing aircraft in fixed patterns over hundreds of cities. Angel
Technologies is planning an airborne Internet network, called High Altitude Long
Operation (HALO), which would use lightweight planes to circle overhead and provide
data delivery faster than a T1 line for businesses. Consumers would get a connection
comparable to DSL. Also, AeroVironment has teamed up with NASA on a solar-
powered, unmanned plane that would work like the HALO network, and Sky Station
International is planning a similar venture using blimps instead of planes.
The computer most people use comes with a standard 56K modem, which means
that in an ideal situation your computer would downstream at a rate of 56 kilobits per
second (Kbps). That speed is far too slow to handle the huge streaming-video and musicfiles that more consumers are demanding today. That's where the need for bigger
bandwidth -- broadband -- comes in, allowing a greater amount of data to flow to and
from your computer. Land-based lines are limited physically in how much data they can
deliver because of the diameter of the cable or phone line. In an airborne Internet, there is
no such physical limitation, enabling a broader capacity.
Several companies have already shown that satellite Internet access can work.
The airborne Internet will function much like satellite-based Internet access, but without
the time delay. Bandwidth of satellite and airborne Internet access are typically the same,
but it will take less time for the airborne Internet to relay data because it is not as high up.
Satellites orbit at several hundreds of miles above Earth. The airborne-Internet aircraft
will circle overhead at an altitude of 52,000 to 69,000 feet (15,849 to 21,031 meters).
At this altitude, the aircraft will be undisturbed by inclement weather and flying
well above commercial air traffic.
Networks using high-altitude aircraft will also have a cost advantage over
satellites because the aircraft can be deployed easily -- they don't have to be launched into
space. However, the airborne Internet will actually be used to compliment the satellite
and ground-based networks, not replace them. These airborne networks will overcome
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the last-mile barriers facing conventional Internet access options. The "last mile" refers
to the fact that access to high-speed cables still depends on physical proximity, and that
for this reason, not everyone who wants access can have it. It would take a lot of time to
provide universal access using cable or phone lines, just because of the time it takes to
install the wires. An airborne network will immediately overcome the last mile as soon as
the aircraft takes off.
The airborne Internet won't be completely wireless. There will be ground-based
components to any type of airborne Internet network. The consumers will have to install
an antenna on their home or business in order to receive signals from the network hub
overhead. The networks will also work with established Internet Service Providers
(ISPs), who will provide their high-capacity terminals for use by the network. These ISPshave a fiber point of presence their fiber optics are already set up. What the airborne
Internet will do is provide an infrastructure that can reach areas that don't have broadband
cables and wires.
The HALO network will provide consumers with a broadband digital utility for
accessing multimedia services, the internet, and entertainment services. The network at
the subscriber's premise will be standards based and employ a user interface as simple as
today's typical consumer modem. Consumers will be able to access video, data, and the
internet rates ranging from 1 to 5 Mbps. Angle will offer higher data rates at the
broadband market matures.
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HALO NETWORK
Overall Concept
The attributes of the HALO Network are illustrated in the fig. below. Many
types of subscribers will benefit from the low price of HALO Network broadband
services schools, families, hospitals, doctor's offices, and small to medium size
businesses. The equipment will connect to existing network and telecommunications
equipment using standard broadband protocols such as ATM and SONET. The HALO
Gateway provides access to the Public Switched Telephone Network (PSTN) and to the
internet backbone for such services as the World Wide Web and electronic commerce.
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Key Features
The key features the HALO Network are summarized below
Seamless ubiquitous multimedia services
Adaptation to end user environments
Enhanced user connectivity globally
Rapidly deployable to sites of opportunity
Secure and reliable information transactions
Bandwidth on demand provides efficient use of available spectrum
Service Attributes
There are various classes of service to be provided .A consumer service would
provide 1-5 Mbps communication links. A business service would provides 5-12.5 Mbps
links .Since the links would be "bandwidth-on-demand," the total available spectrum
would be time-shared between the various active sessions. The nominal data rates would
be low while the peak rates would expand to a specified level. A gateway service can be
provided for "dedicated" links of 25-155 Mbps. Based on the LMDS spectrum and 5-fold
reuse, the service capacity would be 10000 to 75000 simultaneously , symmetrical T1
circuits (1.5 Mbps) per communication payload. The HALO Aircraft would provide
urban and rural coverage from a single platform to provide service to:
100-750000 subscribers
40-60 mile diameter service area (1250 to 2800 square miles)
Coverage of the New York City Metropolitan Area by HALO Aircraft
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Network Access
Various methods for providing access to the users on the ground are feasible. The
figure below shows one approach where each spot beam from the payload antenna serves
a single "cell" on the ground in a frequency-division multiplex fashion with 5 to 1
frequency reuse, four for subscriber units and the fifth for gateways to the public network
and to high rate subscribers. Other reuse factors such as 7:1 and 9:1 are possible. Various
network access approaches are being explored.
Cell Coverage by Frequency Division Multiplexing using Spot Beams
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Network ServicesThe HALO mode provides a multitude of connectivity options as shown below.
It can be used to connect physically separated Local Area Networks (LANs) within a
corporate intranet through frame relay adaptation or directly though LAN bridgers and
routers. Or it can provide video conference links through standard ISDN or T1 interface
hardware. The HALO Network may use standard SONET and ATM protocols and
equipment to take advantage of the wide availability of these components.
HALO NETWORK ARCHITECTURE
Network Elements
The major elements of the HALO Network are shown below. The HALO
Network interfaces to the Public Switched Telephone Network (PSTN) and to the
Internet backbone through the HALO Gateway. On the subscriber side, the HALO
Network provides connectivity to local network provides connectivity to local networks
of various kinds.
The HALO Network Architecture
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Network Architecture
At the apex of a wireless Cone of Commerce, the payload of the HALO
Aircraft becomes the hub of a star topology network for routing data packets between any
two subscribers possessing premise equipment within the service coverage area. A single
hope with only two links is required, each link connecting the payload to the subscriber.
The links are wireless, broadband and line of sight.
Information created outside service area is delivered to the subscriber's
consumer premise equipment ("CPE") through business premise equipment ("BPE")
operated by Internet Service Providers ("ISPs") or content providers within that region,
and through the HALO Gateway ("HG") equipment directly connected to distant
metropolitan areas via leased trunks. The HG is a portal serving the entire network.
It avails system-wide access to content providers and it allows any subscriber
to extend their communications beyond the HALO Network service area by connecting
them to dedicated long-distance lines such as inter- metro optical fiber.
The HALO Network
The CPE, BPE and HG all perform the same functions; use a high gain antenna
that automatically tracks the HALO Aircraft; extract modulated signals conveyed
through the air by millimeter waves; convert the extracted signals to digital data;
provide standards-based data communications interfaces, and route the digital data to
information appliances, personal Computers and workstations connected to the
premise equipment. Thus, some of the technologies and components, both hardware
and software, will be common to the designs of these three basic network elements.
The CPE, BPE and HG differ in size, complexity and cost, ranging from the CPE
which is the smallest, least complex ,lowest priced and will be expressively built for the
mask market; followed by the BPE, engineered for a medium size business to provide
access to multiple telecommuters by extending the corporate data communications
network; to the HG which provides high bandwidth wireless data trunking to Wide Area
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Network ("WANs") maintained and operated by the long distance carriers and content
handlers who wish to distribute their products widely.
In other words the CPE is a personal gateway serving the consumer. The BPE
is a gateway for the business requiring higher data rates. The HG, as a major element of
the entire network, will be engineered to serve reliably as a critical network element. All
of these elements are being demonstrated in related forms by terrestrial 38 GHz and
LMDS vendors. Angel will solicit the participation of key component suppliers for
adapting their technologies to the HALO Network. As with all wireless millimeter
wave links, high rainfall rates can reduce the effective data throughput of the link to a
given subscriber.
Angel plans to ensure maximum data rates more than 99.7% of the time, reduced
data rates above an acceptable minimum more than 99.9% of the time and to limit
outages to small areas (due to the interception of the signal path by very dense rain
columns) less than 0.1% of the time Angel plans to locate the HG close to HALO orbit
center to reduce the slant range from its high gain antenna to the aircraft and hence its
signal path length through heavy rainfall.
Field of View
Angel assumes the "minimum look angle" (i.e., the elevation angle above the local
horizon to the furthest point on the orbit as seen by the antenna of the premise equipment) is
generally higher than 20 degrees. This value corresponds to subscribers at the perimeter of the
service footprint. In contrast, cellular telephone designers assume that the line of sight from a
customer to the antenna on the nearest base station is less than 1 degree. Angel chose such a high
look angle to ensure that the antenna of each subscriber's premise equipment will very likely have
access to a solid angle swept by the circling HALO Aircraft free of dense objects, and to ensure
high availability of the service during heavy rainfall to all subscribers.The high look angle also allows the sharing of this spectrum with ground-
based wireless networks since usually high-gain, narrow beams are used and the antenna beams
of the HALO and ground-based networks will be separated in angle far enough to ensure a high
degree of signal isolation.
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HALO Aircraft Field of View
HALO AIRCRAFTThe HALO Aircraft is under development and flight testing is expected to
occur by mid-1998. The aircraft has been specially designed for the HALO Network
with the Communications Payload Pod suspended from the underbelly of its fuselage.
HALO Aircraft with Suspended Communications Payload
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The HALO Aircraft will fly above the metropolitan center in a circular orbit of
five to eight nautical miles diameter. The Communications Payload Pod is mounted to a
pylon under the fuselage. As the aircraft varies its roll angle to fly in the circular orbit,
the Communications Payload Pod will pivot on the pylon to remain level with the
ground.
The HALO aircraft fuselage contains the Airborne Switching Node ("ASN"), the
primary coolant loop, and power conditioning. Packing switching and network
management functions are performed by the ASN. The communications pod suspended
beneath the aircraft fuselage contains the millimeter wave antenna array with
amplifiers and transceivers. It converts millimeter waves to and from digital signals and
is composed of an array of antennas that beam signals to subscribers and to the HG.
Power and coolant flow between the platform and the payload through a pylon mount
which, in turn, can maintain the payload pod level relative to the ground about the
aircraft roll axis if required. A standard optical interface conveys digital communications
data across the pylon interface that connects the ASN to the Mux/Demux circuitry in the
Pod, which, in turn, impresses the modulated signal upon or extracts it from the
millimeter wave carrier.
HALO Aircraft with Its Communications Pod
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From a payload perspective, the HALO aircraft is a "flying antenna". It is being
prepared for flight testing by Burt Rutan and his team at Scaled Composites during the
summer 1998.
The aircraft configuration is fixed wing with carbon composite materials.
Propulsion will be provided by FAA-certified twin fan jets. The platform will be operated
by a pilot and co-pilot. The crew cabin will be pressurized to provide a comfortable
"shirt sleeve" work environment. Station keeping will be performed by an auto-pilot
utilizing coordinates provided by the Global Position Satellite constellation. The two
pilots will alternate the duty of flying the airplane. The pilot who is relieved of flight
responsibility can be made available to perform routine status checks of the
communications payload, including the operations of the components of the ASN in the
fuselage section, as well as those in the suspended Pod. Smart diagnostics data
regarding health, status, and operation of the communications equipment will be
graphically displayed to the pilot to enable early detecting and forecasting of problems.
Similar but wider data streams will be sent to the local operations center on the ground
through the Gateway to enable technicians to monitor the status, health, and
performance of the airborne communications node.
Proteus Aircraft
Weight 9,000 pounds at takeoff5,900 pounds empty
Wingspan 77 ft 7 inches (23.7 m)Expandable to 92 feet (28 m)
Length 56.3 ft (17.2 m)
Height 17.6 ft (5.4 m)
Engines 2 turbofan engines2,300 pounds of thrustRange 18 hours
Speed 65 knots (75 mph/120.7 kph)to 250 knots (288 mph/463.5 kph)
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COMMUNICATIONS PAYLOADThe HALO Network will use an array of narrow beam antennas on the HALO
Aircraft to form multiple cells on the ground. Each cell covers a small geographic area,
e.g., 4 to 8 square miles. The wide bandwidths and narrow beam widths within each
beam or cell are achieved by using MMW frequencies. Small aperture antennas can be
used to achieve small cells. For example, an antenna having a diameter of only one foot
can provide a beam width of less than three degrees. One hundred dish antennas can be
easily carried by the HALO Aircraft to create one hundred or more cells throughout the
service area. If lensed antennas are utilized, wider beams can be created by combining
beams through each lens aperture, and with multiple feeds behind each lens multiple
beams can be formed by each compound lens.
If 850 MHz of spectrum is assumed, then a minimum capacity of one full-duplex
OC-1 (51.84 Mbps) channel is available per cell. For example, a single platform reusing
850 MHz of spectrum in 100 cells would provide the equivalent of two, OC-48 fiber optic
rings. Higher capacities are possible by increasing the number of cells. By using
Asynchronous Transfer Mode (ATM) technology with over-the-air dynamic bandwidth
allocation, this capacity can be shared by multiple users in an efficient manner. An ATM-
like packet switch on the HALO Aircraft provides the network switching capability to
cross-connect all users within the coverage area as well as connections to other users
through gateways. The elements in the communications payload are shown below. It
consists of MMW transceivers, pilot tone transmitter, high-speed modems, SONET
multiplexers, packet switch hardware and software, and associated ancillary hardware
such as power supplies, processors, etc.
The major design options for antennas in the Communications Payload are to
utilize either platform-fixed beams or earth-fixed beams. For the case of platform-fixed
beams, each antenna would have a fixed field of view. The total field of view for the
entire HALO Network would be the sum of these fields of view of the individual
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antennas. The network could initially have a small footprint and as demands on the
HALO services increase, additional antennas could be added to the Communications
Payload. This results in a modular design, readily adaptable for growth.
Platform-fixed beams are simpler to construct generally, but require the
"handoffs" between beams to be accomplished by the packet switching equipment as
the beams "sweep" across the ground with the movement of the aircraft. However, the
cost and performance penalties for frequently changing the virtual path through the
packet switch may be appreciable.
An alternative is to electronically steer the beams so they remain "fixed" on the
ground as the aircraft moves. These results in more electronic and physical complexity
for the antennas, but this may be a good trade-off to make since the burden on the
packet switch and its network management software would be greatly reduced. These
trade-offs are still being assessed.
Functional Block Diagram of the Communications Payload
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For the case of earth-fixed beams, each antenna would have a wider field of view
than the sum of the beams in that antenna since each beam can be steered in all
directions. Each beam could be capable of steering throughout the HALO footprint, or
could be assigned a smaller portion. If there are "gaps" in the required coverage due to
such things as rivers, hills, or forests, then the earth-fixed beams can be steered away
from these undesirable coverage zones and more efficient usage of the antennas might
result compared to the case of platform-fixed beams.
Premise EquipmentA block diagram describing the CPE (and BPE) is shown below. It entails three
major sub-groups of hardware: The RF Unit (RU) which contains the MMW Antenna
and MMW Transceiver; the Network Interface Unit (NIU); and the application terminals
such as PCs, telephones, video servers, video terminals, etc. The RU consists of a small
dual-feed antenna and MMW transmitter and receiver which is mounted to the antenna.
An antenna tracking unit uses a pilot tone transmitted from the Communications Payload
to point the antenna toward the airborne platform.
The MMW transmitter accepts an L-band (950 - 1950 MHz) IF input
signal from the NIU, translates it to MMW frequencies, amplifies the signal using a
power amplifier to a transmit power level of 100 - 500 mW of power and feeds the
antenna. The MMW receiver couples the received signal from the antenna to a Low
Noise Amplifier (LNA), down converts the signal to an L-band IF and provides
subsequent amplification and processing before outputting the signal to the NIU.
Although the MMW transceiver is broadband, it typically will only process a single 40
MHz channel at any one time. The particular channel and frequency is determined by the
NIU.
The subscriber equipment can be readily developed by adapting from existing
equipment for broadband services.
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Premise Equipment for The HALONetwork
Functional Block Diagram of the Subscriber Equipment
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The NIU interfaces to the RU via a coax pair which transmits the L-band TX
and RX signals between the NIU and the RU. The NIU comprises an L-band tuner and
down converter, a high-speed (up to 60 Mbps) demodulator, a high-speed modulator,
multiplexers and demultiplexers, and data, telephony and video interface electronics.
Each user terminal will provide access to data at rates up to 51.84 Mbps each way. In
some applications, some of this bandwidth may be used to incorporate spread spectrum
coding to improve performance against interference (in this case, the user information
rate would be reduced).
The NIU equipment can be identical to that already developed for LMDS and
Otherbroadband services. This reduces the cost of the HALO Networkservices to the
consumer since there would be minimal cost to adapt the LMDS equipment to thisapplication and we could take advantage of the high volume expected in the other
services. Also, the HALO RU can be very close in functionality to the RU in the other
services (like LMDS) since the primary difference is the need for a tracking function for
the antenna. The electronics for the RF data signal would be identical if the same
frequency band is utilized
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Ease of installation
Angel has designed the HALO Network and the consumer premise equipment
(CPE) to ensure ease of installation by the consumer. The CPE, whether delivered or
purchased through a retailer, is designed for rapid installation and ease of use. The
antenna is self-pointing and is mounted on an outside area offering clear view of the
HALOAircraft.
APPLICATIONSThe ultimate backend platform for wireless, Airborne is a seamless, turnkey solution the
management and distribution of content of micro-Entertainment networksAirborne seamlessly handles:
User-friendly, web-based interface
Support for text, voice, image and multimedia files
Client-specific content scheduling and menu generation
Mobile device recognition and optimization Multilingual content
Extensive usage and analytical reporting
Editorial tools
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FUTURE PLANS
NASA's Sub-space Plans
Not to be left out of the high-flying Internet industry, NASA is also playing a role
in a potential airborne Internet system being developed by AeroVironment. NASA
and AeroVironment are working on a solar-powered, lightweight plane that could fly
over a city for six months or more, at 60,000 feet, without landing. AeroVironment
plans to use these unmanned planes as the carrier to provide broadband Internet
access.
The Helios aircraft will be equipped with telecommunications equipment and stay
airborne for six months straight.
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Helios is currently in the prototype stage, and there is still a lot of testing to be
done to achieve the endurance levels needed for AeroVironment's
telecommunications system. AeroVironment plans to launch its system within three
years of receiving funding for the project. When it does, a single Helios airplane
flying at 60,000 feet will cover a service area approximately 40 miles in diameter.
Helios Aircraft
Weight 2,048 pounds (929 kg)
Wingspan 247 ft (75.3 m)
Length 12 ft (3.7 m)
Wing Area 1,976 square ft (183.6 m2)
Propulsion
14 brushless, 2-horsepower,
direct-currentelectric motors
Range
1 to 3 hours in prototype tests
6 months when fully operational
Speed 19 to 25 mph (30.6 to 40.2 kph)
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The Helios prototype is constructed out of materials such as carbon fiber, graphite
epoxy, Kevlar and Styrofoam, covered with a thin, transparent skin. The main pole
supporting the wing is made out of carbon fiber, and is thicker on the top than on the
bottom in order to absorb the constant bending during flight. The wing's ribs are made of
epoxy and carbon fiber. Styrofoam comprises the wing's front edge, and a clear, plastic
film is wrapped around the entire wing body
The all-wing plane is divided into six sections, each 41 ft (12.5 m) long. A pod
carrying the landing gear is attached under the wing portion of each section. These pods
also house the batteries, flight-control computers and data instrumentation. Network hubs
for AeroVironment's telecommunications system would likely be placed here as well.
It seems that airborne Internet could take off in the very near future. If and when
those planes and blimps start circling to supplement our current modes of connection,
downloading the massive files we've come to crave for entertainment or depend on for
business purposes will be a snap -- even if we live somewhere in that "last mile."
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ADVANTAGES
Unique feature of these solar-electric air-craft that make then appealing platforms
for telecommunications applications include:
Long flight durations up to 6 months or more.
Minimal maintenance cost due to few moving parts.
High levels of redundancy (e. g. aircraft could lose multiple motors and still
maintain station and land safely - most failure modes do not require
immediate response by ground operator)
Highly autonomous controls which enable one ground operator to control
multiple aircraft.
Use of solar energy to minimize fuel costs.
Tight turn radius which makes platform appear geostationary from ground
equipment perspective (i. e. enables use of stationary antennas) and enables
multiple aircraft to serve same area using same frequency spectrum.
Flexible flight facility requirements (aircraft can take off from even a dirt
field and in less distance than the length of its wingspan
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CONCLUSION
Finally I conclude that the HALO aircraft can be thought of as a very tall
tower or very low altitude satellite. Contracted to terrestrial broadband networks, the
HALO Network offers ubiquitous, anyone-to-anyone broadband linkages throughout
the footprint. HALO networks can be introduced to highly promising markets around
the world on a selective basis. "Continuous improvement" is a significant attribute of
the HALO network. It enables Angel to meet the increasing expectations of present
customers, and to open new markets requiring lesser capability by re-assigning
earlier-generation hubs.