HALO  HALO Network

The Cone of Commerce™

James N. Martina and Nicholas J. Colellab
aRaytheon TI Systems, MS 8497, 6600 Chase Oaks Blvd, Plano, TX 75023
bAngel Technologies, Magna Place, Suite 760, 1401 S Brentwood Blvd, St. Louis, MO 63144

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5.1 The ISP Marketplace
5.2 The Local ISP
5.3 Local Area Networks & Telecommuting

6.1 Space Networks
6.2 Atmospheric Networks
6.3 Terrestrial Networks
6.3.1 Digital Subscriber Line Services (xDSL)
6.3.2 38 GHz Millimeter Wave
6.3.3 AT&T Wireless Local Loop
6.3.4 Cable




Angel Technologies Corporation ("Angel") and its partners are creating a wireless broadband metropolitan area network to interconnect tens to hundreds of thousands of users each at multi-megabit per second data rates for multi-media file transfers and interactive discourse. A high altitude long operation (HALO™) aircraft will circle above commercial airline traffic to serve as the hub of the broadband network for providing ubiquitous signal coverage and dedicated point-to-point connections throughout a footprint encompassing a typical metropolitan center, its suburbs, and beyond. Broadband wireless services will be delivered to diverse enterprises to promote new forms of collaborative work and information exchange, thus creating a virtual "Cone of Commerce™" with the HALO™ aircraft at its apex.

This presentation will introduce the HALO™ Network and describe the flow of messages within and beyond the signal footprint in terms of the basic network elements. The aircraft design will be described and its payload attributes will be highlighted. The concept of operations and key operational factors will be addressed. Types of services will be described. The advantages of the HALO™ Network relative to terrestrial and space layers will be summarized for broadband services. Near term actions will be stated.

Keywords: HALO™ Aircraft, HALO™ Network, Cone of Commerce™, broadband wireless services, metropolitan area network

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Passage of the 1996 Telecommunications Act and the slow growth of infrastructure for transacting multimedia messages (those integrating voice, text, images, sound, and video) have stimulated an intense race to deploy non-traditional infrastructure to serve businesses and consumers at affordable prices. The game is new and the playing field is more level than ever before. Opportunities exist for entrepreneurs to challenge the market dominance enjoyed for years by incumbents.

An electronic "information fabric", a quilt of space, atmospheric, and terrestrial data communications layers, will emerge linking digital information devices anywhere on the Earth. Packet-switched data networks will meld with connection-oriented telephony networks. Communications infrastructures will be shared efficiently among users to offer dramatic reductions in cost and large increases of data rates. An era of inexpensive bandwidth will soon begin.

The convergence of innovative technologies and manufacturing capabilities affecting aviation, millimeter wave wireless, and multi-media communications industries enables Angel to pursue new wireless broadband communications services. The HALO™ Network will offer ubiquitous access to any subscriber within a "super metropolitan area" from an aircraft operating at high altitude. The aircraft will serve as the hub of the HALO™ Network serving tens of thousands of customers. Each customer will be able to communicate at multi-megabit per second data rates through a simple-to-install subscriber unit. The HALO™ Network will be steadily evolved at a rapid pace defined by the emergence of advanced technology world-wide. The HALO™ Network will be a wireless communications network solution. It is an evolving template to be deployed globally on a city-by-city basis.

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Subscribers in homes, commercial ventures, and education and health services will be able to communicate with each other and with producers/distributors of information, special content, and entertainment by simply accessing a "data tone" much like telephone subscribers today use a dial tone. The subscriber's premise equipment will be standards-based and will require a level of understanding by the subscriber no higher than an ordinary modem for today's personal computers. A small dome mounted on the outside of the premise will house a high-gain antenna that will automatically track the HALO™ aircraft circling miles away at high altitude.

Premise Equipment for The HALO™ Network

At the apex of a wireless Cone of Commerce™, the payload of the HALO™ aircraft will serve as 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 hop with only two links is required; each link connecting the payload to a subscriber. The links are wireless, broadband and line of sight.

Information created outside the 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") directly connected to distant metropolitan areas. 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 have functions in common: 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, and priced for the mass 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 Networks ("WANs") maintained and operated by the long distance carriers or national and international ISPs. In other words, the CPE is a personal gateway serving the consumer. The BPE is a gateway for businesses 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. Consequently, the unit price of the HG will be significantly higher than the unit prices of the other two elements. 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, rainfall will reduce the strength of the signal received by a given subscriber. Angel plans to ensure maximum data rates more than 99.7% of the time, provide 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 the HALO™ orbit center to reduce the slant range from its high-gain antenna to the aircraft and hence the length of the signal path through heavy rainfall.

Angel assumes the minimum look angle ("MLA") will be higher than 20 degrees typically, perhaps as low as 10 degrees for regions with low rainfall attenuation. The MLA corresponds to subscribers at the perimeter of the service footprint and is defined to be the elevation angle above the local horizon to the furthest point on the orbit as measured from the antenna of the premise equipment. In contrast, cellular telephone designers assume that the line of sight angle from a customer to the antenna on the nearest base station is less than 1 degree. Angel chose such a relatively 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.

A frequency reuse approach similar to traditional cellular mobile networks can be employed in the HALO™ Network. The available spectrum would be divided into frequency sub-bands that are projected from the communications pod as separate "beams". Details on this approach are also described in a related paper, "Broadband Wireless Services from a HALO™ Aircraft".1 Herein, a simple frequency re-use pattern is described to illustrate how the service area can be covered to share bandwidth among multiple users and how dedicated bandwidth can be provided to premier customers. A less aggressive re-use pattern may be required to satisfy co-channel interference issues in an actual airborne network.

Suppose the frequency bands providing the up and down links to the HALO™ aircraft are divided into five (5) equal sub-bands {A, B, C, D, and E}. A subset of four (4) sub-bands {A, B, C, and D} can then be arranged to form a square tile which, in turn, is tessellated to cover the service area. Each sub-band within a tile, whether labeled A, B, C, or D, will serve many subscribers who share the capacity available in the beam spot corresponding to that sub-band.

On the other hand, sub-band {E} is "orthogonal" in frequency to the other four (i.e., its spectrum is disjoint of the other four sub-bands). It offers frequencies not used in any tiles. Consequently, it can be located anywhere within the signal area to serve premiere customers on a dedicated basis. (This assertion requires the separation between neighboring {E} beam spots be not less than the minimum distance linking the centers of neighboring tiles within the service area, assuming all sub-bands involve similar size antenna apertures on the HALO™ aircraft.)

Each frequency tile repeated on the ground corresponds to a single airborne antenna "cell" in the pod suspended beneath the HALO™ aircraft. The antenna cells are arranged somewhat like the photo-receptors forming the eye of a common household fly to cover the service area. Each cell creates multiple beams, four in our example {A,B,C,D}, through a common refractive optical train specifically optimized for millimeter wave throughput. Whereas, the {E} beam spots are created by conventional, high-gain antennas that are pointed and stabilized by electro-mechanical gimbals and servos. An advanced antenna based upon digital beam forming can, in principle, replace the group of mechanically stabilized antennas, thus eliminating moving components and multiple interfaces through a consolidation of electronic and millimeter wave components. However, it may be burdened by high costs. Whereas, there are many years of experience associated with flying mechanically stabilized antennas on a variety of military and civilian aircraft. Angel will solicit vendors to explore the feasibility of applying and adapting antenna design breakthroughs at lower frequencies, such as at the Personal Communications Services ("PCS") band near 2 GHz, to the millimeter wave regime.

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The HALO™ aircraft fuselage contains the Airborne Switching Node ("ASN"), the primary coolant loop, and power conditioning. Network management functions are performed by the ASN. The communications pod 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, maintains the payload pod level relative to the ground about the aircraft roll axis. 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, impress the modulated signal upon or extract it from the millimeter wave carrier.

HALO™ Aircraft with Its Communications Pod

Asynchronous Transfer Mode ("ATM") circuitry have strong appeal for implementing the HALO™ Network. They enable multimedia file transfers, allow effective data bandwidth sharing (bandwidth on demand), and offer Quality-of-Service options. An ATM-based architecture can be scaled to increase network capacity. The fierce global competition among ATM vendors will likely ensure an attractive and rapidly-evolving suite of components for implementing both the airborne and ground elements of the HALO™ Network. On the other hand, the global pool of experts implementing advanced ATM networks is small compared to that for frame relay (Ethernet) technologies. Also, frame relay appears to be defending its hold as the "de facto" technology for high-speed local area networks ("LANs"). The technology choice for implementing the HALO™ Network will likely be the winner of the high-speed, low-cost LAN battle.

From a payload perspective, the HALO™ aircraft is a "flying antenna". Burt Rutan and his team at Scaled Composites have invoked simplicity and durability to produce a reliable aircraft for Angel's wireless communications services. The team has incorporated pragmatic features to maximize the value of Angel's high altitude real estate. The first HALO™ aircraft is under construction and scheduled for first flight during 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 residing in a crew cabin of ergonomic design. The cabin will be pressurized to provide a "shirt sleeve" work environment. Station keeping will be performed by an auto-pilot utilizing coordinates provided by the Global Position Satellite constellation.

The payload bearing attributes of the HALO™ aircraft include:

  • 2300 lb. for the airborne elements of the HALO™ Network:
    • 1500 lb. for the communications pod,
    • 300 lb. for pod interfaces and fairing,
    • 500 lb. for the Switch / Network in the HALO™ fuselage;
  • 18 ft diameter payload pod housing the antennas and interfaces suspended below the aircraft;
  • 40 KVA power for the airborne network elements with matched thermal management; and
  • Bank angle compensation of the pod.

Advances in component performance and packaging methods occurring in the consumer electronics and personal computer industries will enable progressive weight reduction of the airborne elements, especially those affecting the digital functions of the HALO™ Network without corresponding increases in cost. Consequently, more capability will be packaged per pound and greater performance may be realized per pound as the equipment is upgraded.

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The HALO™ aircraft will execute a circular orbit of roughly 5 to 8 miles in diameter at an altitude ranging from 52,000 to 60,000 feet. From that vantage, broadband services can be offered to users over an area of several thousand square miles or larger encompassing a typical major city and its surrounding towns and communities.

Piloted Aircraft: In order to streamline the aircraft development and FAA certification processes, the HALO™ aircraft will be manned with two pilots. The additional operating costs associated with this strategy is acceptable in light of the advantages gained. Over time, Angel may transition to single pilot operation to be followed by unmanned autonomous operations.

Number of Aircraft per Site: Angel will maintain a continual HALO™ aircraft presence on-station above each market served. Although each HALO™ will be able to remain airborne in excess of 15 hours, Angel has planned for 8 hour mission times on station. Three aircraft will be allocated for each isolated site: one on-station, one ascending or descending or being prepared for flight at the local or regional airport facility, and one spare.

Ground Turnaround Time: An emphasis on "line replaceable unit" maintenance will allow Angel's dedicated personnel to perform regular and unscheduled maintenance actions between missions.

Weather Diversions: Angel will pursue a certificate under FAR23 regulations and will be authorized to operate in the full range of normal instrument flight conditions. However, Angel's operational plan is conservative and calls for the HALO™ aircraft to avoid significant weather by prompt diversion to alternate municipal airports with current and forecast conditions approaching visual flight rules. Even the largest storm systems are a few hundred miles across, a distance easily traversed by HALO™ aircraft.

The following factors contribute to Angel's expectation of achieving high operating reliability with HALO™ aircraft:

  • Lessons over decades with airborne military transport and express freight aircraft operations will be applied. The military has maintained continuous around-the-clock operations of strategic aircraft since the 1950's but at high cost. Of greater relevance, priority parcel delivery services have refined aircraft fleet operations. Angel will adopt industry practices ensuring affordable around-the-clock availability.
  • Angel will utilize fleet redundancy to ensure continuity of service in anticipation of worst case failure scenarios. Angel will position standby HALO™ aircraft on the ground and, when required, in the air.
  • HALO™ aircraft fleet operations will be steadily improved as the aircraft design is refined and as operating behaviors and performance are logged, analyzed, and utilized to upgrade choices of components and maintenance activities.
  • The simple, robust design of HALO™ aircraft exceeds the reliability of typical fan jet aircraft. Angel's HALO™ aircraft design will benefit from the aerospace industry's decades of reliability engineering to achieve unparalleled levels of mission reliability.
  • HALO™ aircraft incorporate redundant mission critical systems. The HALO™ aircraft's systems are being selected for high reliability. Where necessary, systems are being designed with fail-passive redundancy to ensure sufficient time for a replacement HALO™ aircraft to arrive on-station.

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Subscribers of communications for voice, text, data, image, sound, and video are being served by data rates ranging over nearly three decades, i.e., from approximately 10 Kbps to 10 Mbps. Because of Angel's unique and agile architecture, the Company will be able to offer customers various types of service. Consumers requiring multi-media information are likely to require data rates in the range of 128 Kbps to 1 Mbps with bursts up to 5 Mbps. Businesses desiring to provide access to their corporate network at the metropolitan scale may require fractions of 10 Mbps for their external users. As a premium service, Angel will provide dedicated wireless pipes with data rates up to 25 Mbps.

The HALO™ Network can serve broadband applications for the business and consumer markets:

  • Internet/WWW Access for Small and Medium Businesses
  • Telecommuting
  • Portable Subscriber Units (Low Mobility)
  • Video-Conferencing
  • Entertainment
  • Telemedicine
  • Tele-education
  • Civil Services
  • Electronic Shopping and Commerce

Angel is focusing on two key market segments: wholesale capacity for use by the Internet Service Provider, and extension of corporate data networks of small and medium businesses.

5.1 The ISP Marketplace
Internet Service Providers ("ISPs") already deliver Internet access service to one out of every ten households in the United States. This ratio is expected to increase, whereby 35 percent of all homes will gain access during the year 2000.

Today, access service is provided by five types of competitors:

  • National ISPs (e.g., AOL, CompuServe, Microsoft Network)
  • Regional Bell Operating Companies ("RBOCs")
  • Independent (Local) ISPs
  • Cable Operators
  • Wireless Service Providers (satellites, or terrestrial wireless via millimeter waves at the LMDS and 38 GHz bands, wireless local loop at the PCS bands, or packet relay at the ISM bands).

About 70 percent of homes occupied by customers are being served by large National ISPs. The remaining 30 percent of customers' homes are being served by Local ISPs that range in size from hundreds to tens of thousands of customers. Most consumers are utilizing 28.8 Kbps dial-up modems, and a small percentage have already migrated to 56 Kbps modems. Most businesses are utilizing 128 Kbps ISDN lines and a very small number of the businesses are utilizing DS-1 connections (1.544 Mbps).

5.2 The Local ISP
The local ISPs are perhaps the most entrepreneurial and fastest growing segment of the market, expanding at rates approaching 75 percent per year. In order to maintain this rapid rate of growth in the face of new competition from the RBOCs and the cable companies, these local ISPs are anxious to adopt new technologies that will allow them to differentiate their services. The local ISPs think they will be required to provide megabit per second rates to homes and business by the turn of the century in order to survive. However, they are precluded from using the cable infrastructure as cable companies are viable competitors to them. Similarly, the RBOCs' plan to offer high-speed Internet access through Digital Subscriber Line ("DSL") services and may also compete directly with the local ISPs. Whereas, the HALO™ Network will allow the ISPs to offer distance-insensitive connections within the HALO™ Network service area, bypassing the Local Exchange Carriers and the Interexchange Carriers, to substantially reduce their cost of service.

5.3 Local Area Networks & Telecommuting
Angel will pursue corporations with intranets and enterprise networks that need to extend their LAN beyond the corporate facilities to their employees' homes, regional offices, and field locations. Angel will also serve corporate applications including the "office-in-a-briefcase" and other types of portable offices.

Angel plans to target small and medium businesses (1 to 1,000 employees) with the following attributes:

  • Manage distributed operations across the metropolitan region;
  • Utilize employees who typically telecommute;
  • Require the exchange of large data files with their customers or suppliers; and
  • Have a sizable extemporaneous work force of consultants and temporaries.

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Given the lack of infrastructure to support the current and projected demands for broadband data communications, an intense race has begun to deploy broadband networks to satisfy businesses and consumers. These networks include satellite constellations, atmospheric alternatives to HALO™ aircraft, and terrestrial wired and wireless networks. The space layer includes satellites operating at geo-synchronous orbit ("GEO") and low-Earth orbit ("LEO"). The atmospheric layer includes high-altitude autonomous airships (i.e., dirigibles) and the HALO™ aircraft. The terrestrial layer includes wireless data transport at millimeter wave carrier frequencies, AT&T's wireless data service at the PCS frequency band, data transport over coaxial cable installed for cable television, and an assortment of digital subscriber line services ("xDSL") over twisted wire pairs installed for telephone networks.

Angel will have several parameters to vary in order to enhance the performance and to increase the capacity of the HALO™ Network. For example, enhancements of network capacity can be realized by increasing the number of cells in the communications pod, or the number of beam feeds per cell, or both, along with appropriate scaling of electronics. Alternatively, the bandwidth per beam spot can be widened or the encoding order increased. Performance enhancements practical at the system level, however, will be determined by trades and balances. Increasing the system capacity more than ten-fold within several years after the introduction of the first network may be realizable. Also, from the perspective of a single communications link, the components in the string from the subscriber to an information provider or to the WAN through the HG will embody advancements and improvements from earlier generation HALO™ Networks. Service quality will be improved and capacity will be increased through parallel growths of the knowledge and technological bases.

6.1 Space Networks
Satellite networks are targeting a diverse set of wireless communications markets. New generations of satellites promise to deliver consumer and business applications including mobile telecommunications service, "bandwidth-on-demand" interactive data communications, and direct broadcast satellite service. For example, Hughes Network Systems recently announced the release of Direct Duo for delivering "Turbo Internet" service from Direct PC and the more than 200 channels of digital satellite TV available from Direct TV. The Internet service is asymmetric. The uplink from the consumer is slower, using a dial up modem, than the downlink. The consumer must commit a phone line to the service. Turbo Internet is starting to penetrate the consumer market and may be a market stimulus for new hybrid multi-media products.

GEO satellites have been in commercial operation for over 30 years and have transformed inter-continental communications and broadcasting. GEO satellites orbit the Earth nearly 23,000 miles above its surface. Such a great distance severely limits the bandwidth possible with small antennas and introduces signal delay. While desktop video-conferencing may be awkward through a link between the ground and GEO satellites, the primary disadvantages of GEO satellites are high capital expense, limited bandwidth, and beam spot areas quite large relative to those possible with the HALO™ Network.

At least, seven broadband satellite networks are under development utilizing the Ka-Band (19 GHz and 28 GHz bands). These constellations will target regional and global services such as interactive video, video-conferencing, high-speed Internet access, LAN extension and inter-continental multi-media file transfers, by offering data bandwidths and channel capacities much greater than available now in orbit or planned for by the mobile satellite carriers. Customers will access LEO systems through small aperture subscriber units made possible by a signal path distance much shorter than to GEO.

On the downside, satellites are plagued by critical risks including launch, architecture, complex international regulatory policies, difficult maintenance and obsolescence. Moreover, satellite systems are "all or nothing" multi-billion dollar investments with significant financing risks. In contrast, the HALO™ aircraft involve routine aircraft flight operations well established by the commercial air freight and passenger airline industries. The HALO™ Network has only one airborne communications hub per city in a simple "star" network configuration instead of a "mesh" network of many satellites involving cross-links. Spectrum opportunities can be pursued on a city-by-city basis instead of negotiated on a global scale. The central node of the HALO™ Network, the airborne hub, can be routinely serviced for optimal performance. The modular nature of the HALO™ Network facilitates the adoption and integration of technologies recently proven and evolved by world-wide competition. The relatively low altitude of the HALO™ Network hub allows frequency reuse on a length scale appropriate for metropolitan area networks. Finally, the HALO™ Network is an evolving "template" that can be deployed one market at a time to ease the financing commitment of growing a global business.

6.2 Atmospheric Networks
Two development stage companies intend to deliver wireless communications services from unmanned platforms operating in the stratosphere. Sky Station and SkySat plan to develop "lighter-than-air" high altitude dirigibles. Both platforms require technological innovations affecting propulsion, structures, and mission control software. The Federal Aviation Administration ("FAA") will be required to pioneer new acceptance procedures in order to approve the commercial operation of massive (semi-) autonomous platforms at high altitude, above or near dense population centers. Whereas, the HALO™ aircraft has a conventional design, is operated by human pilots, and its flight operations map onto existing approval procedures of the FAA. The HALO™ aircraft will operate in a flight envelope similar to the U2 aircraft, whose aerodynamics were established nearly 40 year ago. Unlike a slow moving dirigible, the HALO™ aircraft will possess an airspeed high enough to maintain station during high wind speed. The HALO™ aircraft has a fixed-wing airframe and is powered by conventional turbo fan propulsion. It embodies descendants of basic aircraft components refined by multiple tens of thousands of man-years of collective engineering efforts.

6.3 Terrestrial Networks
Terrestrial networks include both wired and wireless solutions. The telephone service companies (LECs, RBOCs, IXCs) offer high capacity services (e.g., DS-1, DS-3 and higher) over twisted wire pairs on a limited basis. They have not significantly penetrated the small business and consumer markets due to the high cost of installation and high monthly service rates. While they have penetrated the smaller market of large companies who can afford to purchase high-speed services for their corporate networks, the telephone companies continue to struggle with developing low-cost alternatives for broadband services. Furthermore, they are feeling significant pressure from the cable television companies and ISPs who are pursuing the home and small business markets. Wireless networks are emerging and bode significant promise for both U.S. and foreign markets.

6.3.1 Digital Subscriber Line Services ("xDSL")
In lieu of committing enormous capital to duplicating the existing infrastructure with dedicated high speed lines and new switches, the telephone companies are pursuing a rescue technology with the hope of squeezing high bandwidth services out of their huge copper wire investment. A family of services, referred to as "xDSL", has yet to be standardized. xDSL requires a special modem at each end of the twisted pair line. The modems use sophisticated algorithms to increase the data rate; their costs may remain high despite hoped for economies of scale. Furthermore, costly upgrades to the switching fabric of the central offices and the subscriber line interface cards are required to accommodate demands imposed on the infrastructure by xDSL services versus "bread and butter" commercial telephony. Although a promising technology, xDSL has challenges to overcome, and field tests with realistic noise levels may be diminishing enthusiasm. xDSL deployment strategies anticipate a large investment of fiber to the neighborhood before ubiquitous coverage can be offered. Many telephone companies and vendors appear to be waiting out the technology risk and the setting of standards before making substantial capital commitments for bridging the "last mile" to the customer with xDSL.

However, xDSL technologies may prove to be very useful for inter-connecting computer networks in neighboring buildings and thus may become a dominant technology for increasing the speed of "internal" corporate data communications. If so, the proliferation of low-cost, short-distance xDSL technologies may stimulate a demand for high-speed metropolitan scale "external" wireless networks like the HALO™ Network, by exaggerating the difference of data rates of internal and external corporate networks.

6.3.2 38 GHz Millimeter Wave
Terrestrial millimeter wave service companies, e.g., Advanced Radio Telecom and Winstar Communications, both licensees under the FCC's "38 GHz" band for wireless broadband transmissions utilizing 100 MHz channels, are in the early stages of deploying point-to-point broadband data links with limited point to multi-point capabilities. There is no commercial wireless venture offering a point to multi-point network for distributing high-speed data and multimedia interactivity over a metropolitan distance scale. Angel's HALO™ Network may emerge as one of the first point to multi-point networks for interactive broadband communications and may offer an attractive complement to terrestrial millimeter wave service companies.

Terrestrial millimeter wave networks rely on the installation of antennas atop buildings or other high structures in order to create line-of-sight links free of objects. Roof rights and building/riser access must be negotiated for each link. Networking customers in neighborhoods with low roofs and mature trees can be problematic. Connecting to a small office/home office in the suburbs can be more difficult than establishing an urban link due to natural objects and man-made structures obstructing the signal path. Consequently, providing "any-to-any" coverage by a terrestrial millimeter wave network is difficult. On the other hand, Angel's HALO™ Network will provide standalone wireless multi-point connectivity to the end user and it can serve as a network hub for millimeter wave operators. Angel could effectively wholesale its capacity to terrestrial operators, thus helping them to expand coverage within a given market.

6.3.3 AT&T Wireless Local Loop
AT&T recently announced its intention to utilize its investment in PCS spectrum and cellular telephony infrastructure to offer ISDN-like bit rates in Wireless Local Loops to provide a "last mile solution" to wired networks. AT&T is planning to allocate 10 MHz of its PCS spectrum to provide wireless point to multi-point service to 80 to 90 percent of the households in the respective PCS footprint. To effectively develop such a network, AT&T will need to integrate newly developed proprietary hardware and software. The quality and reliability of such a service are unknown. AT&T is targeting narrow-band services like faxing, telephony, and data communications at several times higher rates than common household modems for personal computers. Price reductions of 56 Kbps modems expected over the next several years will define a very aggressive price range to AT&T's wireless interface to consumer-owned personal computers, since AT&T's advertised service will offer only about a factor of two higher speed for data transfers.

6.3.4 Cable
Cable operators are facing a significant threat from direct broadcast satellite companies and wireless cable companies. With the advent of cable modems, the cable TV companies see a new opportunity in two-way data communications. Although this would appear to be an excellent diversification strategy, there are technical challenges affecting the delivery of an effective two-way broadband service. Specifically, cable systems are designed to send signals one way preferentially; i.e., broadcast video from the head end to the consumer. In order for this infrastructure to deliver symmetric two-way transmissions, the cable operators will be required to invest in switching backbones and line upgrades. This will be a large commitment since a minor fraction of cable infrastructure today is compatible with high-speed two-way communication.

@Home is a promising venture targeting the home market. It utilizes the cable network to offer high-speed Internet access and services. @Home has deployed its own high-capacity Internet backbone and provisioned it with large memory caches at each service region, in order to reduce latencies typical of Internet routing and to store frequently requested information content as close as possible to the customer. @Home is a consumer market pioneer and stimulator. It has bundled music channels, news services, and entertainment. Entrepreneurs are creating new software applications and products to profit from growing consumer demand for broadband services. Angel believes that emerging consumer information applications and products targeting @Home will also find a home in the HALO™ Network.

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Angel and its partners will harvest the "state of the industry" world-wide for components of proven performance and will preferentially emphasize integration over basic developments to realize system-level capabilities. While development of a small set of enabling components will be required, in particular those related to the millimeter wave antenna, most components of the network will be adapted from the telecommunications, data communications, and computer industries where they have well understood performance characteristics and strong bases of support. Innovation will occur predominantly at the system level as it affects packaging and integration. Proprietary software will be developed to manage data traffic flows and to allocate network resources. However, as pervasively as possible, the software load will integrate objects and modules refined by data communications applications and will be adapted to the HALO™ Network.

The first aspect of Angel's development approach is to routinely adopt and integrate proven components and to pioneer only those items not available from established sources. The second aspect is to progressively test and demonstrate systems and subsystems and to allow the knowledge so gained to accelerate progress. During the next twelve months, Angel and its partners will execute tasks pertaining to the development and implementation of the HALO™ Network including, but not limited, to the following:

  • Solicit prepared "white paper" responses from vendors of HALO™ Network components and subsystems.
  • Cultivate strategic vendor relationships.
  • Commence software specification and development.
  • Assess basic network components.
  • Perform flight experiments of basic network components with general aviation aircraft.
  • Flight test the HALO™ developmental aircraft.
  • File with the FCC for access to millimeter wave experimental spectrum and establish U.S. "standing" for usage of millimeter wave spectrum by the HALO™ Network.
  • Expand Angel's engineering team.

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Angel and its partners are creating a wireless broadband "super-metropolitan" area network to interconnect tens to hundreds of thousands of subscribers each at multi-megabit per second data rates. A HALO™ aircraft will operate above commercial airline traffic to serve as the hub of the millimeter wave wireless broadband network providing ubiquitous coverage as well as dedicated point-to-point connections. Broadband wireless services will be delivered to diverse enterprises to promote new forms of dialogue and interaction. The two primary market segments will be wholesale capacity to Internet Service providers and retail broadband services to small and medium size businesses for extending their corporate data networks to the metropolitan scale. The HALO aircraft will commence flight testing during the first half of 1998. Angel plans to work closely with the vendor community and will cultivate partnerships with strategic vendors. Angel plans to hire engineers of superb talent.


Dr. Nicholas J. Colella is the Chief Technology Officer of Angel Technologies Corporation. In prior years, he held senior technical and leadership positions at Lawrence Livermore National Laboratory. He invented the RAPTOR/TALON theater ballistic missile defense concept and served as DOD's executing agent for pioneering low-cost, high-altitude, long-endurance unmanned aircraft, high mass fraction kinetic kill interceptors, electro-optics and RF/laser communications systems. He co-created Brilliant Pebbles, led LLNL's spacecraft design and survivability projects, and developed ultra-wide-field-of-view (one-steradian) cameras employing spherically concentric refractive optics for tracking satellites and space objects. He is a founding partner of an electronics multi-chip module company and the National Robotics Engineering Consortium at Carnegie Mellon. Dr. Colella received his Ph.D. in Physics at Carnegie Mellon in 1986.

James Martin is the lead systems engineer and project manager for the HALO™ communications payload under development at Raytheon TI Systems for Angel Technologies. At AT&T Bell Labs, he developed cellular wireless telecommunications equipment and underwater fiber optic transmission systems. Mr. Martin has recently published a "Systems Engineering Guidebook" with the CRC Press. His specialty is systems engineering management, systems architecting and the total systems engineering process.


  1. J. Martin and N. Colella, "Broadband Wireless Services from a HALO™ Aircraft," Proc. of the SPIE International Symposium on Voice, Video, and Data Communications: Broadband Engineering for Multimedia Markets, 1997.

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