Status as of July 2006: Project Cancelled October 2002!
Number of Satellites
Teledesic LLC, a satellite communications services company, today announced that it has suspended work under its satellite construction contract with Italian satellite manufacturer Alenia Spazio SpA and will significantly reduce its staff as it evaluates possible alternative approaches to its business.
"We continue to believe that the Teledesic system would be useful to governments around the world in connection with disaster relief, anti-terrorism, defense services and other critical government activities. We also believe that providing ubiquitous, quality broadband service to the world, including those three billion people who have never had service, will be a viable business and remains a worthy mission," said Teledesic Co-CEO William Owens. "Teledesic's global license for 1 GHz of nongeostationary satellite spectrum with international ITU priority is widely viewed as a significant regulatory achievement that is not likely to be duplicated."
Early this year, Teledesic engaged Alenia to build the first two satellites of its planned 30-satellite constellation of mid-earth orbiting satellites designed to provide broadband communications to any part of the globe. However, after continually reviewing the foreseeable financial markets and the commercial prospects for satellite point-to-point communications, the company does not believe that it is prudent, purely on speculation, to continue the substantial capital expenditures required to construct and launch the satellites consistent with the timing required to meet FCC and ITU regulatory milestones. Over the past ten years, Teledesic has spent hundreds of millions of dollars on design and development of global broadband satellite system concepts.
"Teledesic has dedicated and talented employees passionate about the Teledesic vision, leading industrial partners, and some of the most astute private investors from around the world," said Teledesic Chairman and Co-CEO Craig McCaw. "We have met our regulatory milestones to date and remain financially solvent. Our decision to suspend our activities results from an unprecedented confluence of events in the telecommunications industry and financial markets. We do not presently see elements in place that would result in returns to our shareholders that are commensurate with the risk. We continue to believe that the Teledesic service would ultimately provide unique and measurable benefits to the world, and we are looking at scenarios to preserve the ability for that service to be realized."
WASHINGTON - Oct. 2nd, 2002 (Spacenews) -- Citing a bleak global investment climate, Teledesic LLC has halted work on a large satellite constellation that was intended to provide high-speed data communications services anywhere in the world.
In a statement, Teledesic, led by cellular pioneer Craig O. McCaw, also said it would lay off a significant number of employees.
Teledesics decision throws into limbo a contract signed earlier this year with Alenia Aerospazio SpA of Rome. Under that contract, the Italian space company was to have supplied the first two spacecraft in a system intended to eventually consist of 30 satellites in medium Earth orbit.
Plans at one time called for launching 840 Teledesic spacecraft. Later that number was pared down to 288.
In the Sept. 30 statement, Teledesic of Bellvue, Wash., said it cannot justify additional expenditures on the project because of the state of the worlds financial markets and the outlook for satellite-based point-to-point communications services.
"Our decision to suspend our activities results from an unprecedented confluence of events in the telecommunications industry and financial markets. We do not presently see elements in place that would result in returns to our shareholders that are commensurate with the risk," McCaw, Teledesics chairman and co-chief executive officer, said.
BELLEVUE, Washington February 1, 2002 Teledesic LLC, a satellite communications services company, today announced that it has signed an agreement with the Italian satellite manufacturer Alenia Spazio SpA, a Finmeccanica company, to build satellites for Teledesic's global, broadband Internet-in-the-Sky® satellite communications network.
"Our agreement with Alenia Spazio is an important step toward developing our global broadband satellite communications network," said Teledesic President Dennis James. "This agreement with a well-respected international satellite manufacturer as our partner enables us to begin deploying our system economically."
KIRKLAND, Wash. -- November 5, 2001 ICO Global Limited, the satellite holding company formed by telecommunications entrepreneur Craig McCaw, today announced that it has reached final agreement on its merger with New ICO Global Communications (Holdings) Limited. ICO Global, previously known as ICO-Teledesic Global Limited, also has agreed with Teledesic Corporation to end their proposed merger to allow both companies the greatest flexibility in the current economic market.
In May 2000, ICO Global, based in Kirkland, Wash., proposed the mergers of ICO and Teledesic with ICO Global. Bellevue, Wash.-based Teledesic is developing a global broadband satellite communications network. London-based ICO is developing a mobile satellite system to offer high-quality mobile voice services and medium-speed wireless Internet and other packet-data services.
"To maintain maximum flexibility in this market, it is prudent to keep ICO and Teledesic independent as the needs for satellite services continue to evolve in the changing international landscape," McCaw said.
Both ICO and Teledesic will continue to aggressively pursue their independent - yet complementary - business plans. It is possible that a merger between the two entities may be re-evaluated in the future.
The ICO Global-New ICO merger is subject to ICO Global shareholder approval.
Oct 16, 2000 Space & Tech Digest : Teledesic LLC has ended its agreement with Motorola Inc. to provide it with satellites. The two companies issued a joint statement that said they had a reached a "mutual decision" to terminate an agreement that had made Motorola the prime contractor for the Teledesic satellite system. No reason for the termination was given other than to allow Teledesic "the flexibility to pursue alternative approaches for building its global, broadband satellite communications network."
Motorola has invested US$150 million into Teledesic while receiving US$250 million from the venture when the contract was signed as down payment for engineering work Motorola had done prior to the contact. At the time Motorola joined the Teledesic project, it abandoned Celestri, its own project to develop a satellite constellation for high-speed communications. During the past year, Motorola had reassigned some of its employees and stopped subcontractor work on Teledesic, not wanting to incur additional costs without a final contract. Planned reviews of the Motorola-Teledesic system had been delayed for months as Teledesic reviewed investments in other satellite ventures. Motorola retains its investment in Teledesic.
Teledesic may downsize its constellation further, although no indication has been given of when it plans to unveil its new plans for the Teledesic satellite system. It is unclear how changes to the constellation will be received by regulatory authorities.
Earlier this year Teledesic merged with ICO. ICO's satellites are being modified to support higher data rates that might allow them to do some high-speed data communications, in addition to the telephony applications originally planned for the satellites. ICO's prime contractor has been Hughes Electronics Corp.'s, now Boeing Satellite Systems
288 Satellites + spares in 1375km circular low earth orbit. Broadband data and voice services.
This is from Teledesic:
TECHNICAL DETAILS OF THE TELEDESIC NETWORK
The Teledesic Network uses a constellation of 840(??) operational interlinked low-Earth orbit satellites and up to four operational spares per orbital plane to provide global access to a broad range of voice, data and video communication capabilities. Through its global partnerships, the Network provides switched digital connections between users of the Network and, via gateways, to users on other networks. A variety of terminals accommodate " on-demand" channel rates from 16 Kbps up to 2.048 Mbps ("E1"), and for special applications up to 1.24416 Gbps ("OC-24"). This allows a flexible, efficient match between system resources and the requirements of users diverse applications.
The Teledesic Network provides a quality of service comparable to todays modern terrestrial communication systems, including fiber-like delays, bit error rates less than 10-10, and a link availability of 99.9% over most of the United States. The 16 Kbps basic channel rate supports low-delay voice coding that meets "network quality" standards.
The initial Teledesic constellation will support a peak capacity of 1,000,000 full-duplex E-1 connections, and a sustained capacity sufficient to support millions of simultaneous users. The actual user capacity will depend on the average channel rate and occupancy. The system design allows graceful evolution to constellations with much higher capacity without altering the system architecture, spectrum plan or user terminals. The network capacity estimates assume a realistic, non-uniform distribution pattern of users over the Earths land masses.
The system provides 24 hour seamless coverage to over 95% of the Earths surface and almost 100% of the Earths population.
2. THE CONSTELLATION OVERVIEW
The Teledesic constellation design supports the network requirements for quality, capacity and integrity. To provide high-quality, high-speed wireless channels at the intended peak user density levels requires substantial bandwidth. The only feasible frequency band internationally allocated to Fixed Satellite Service that meets Teledesics requirements is the Ka band. High rain attenuation, terrain blocking, and other terrestrial systems in this band make it difficult for earth terminals to communicate reliably with a satellite at a low elevation angle. The Teledesic constellation uses a high elevation mask angle to mitigate these problems. A low orbit altitude is used to meet the requirements for low end-to-end delay and reliable communication links that use low power and small antennas. The combination of low altitude and high elevation mask angle results in a small coverage area per satellite and a large number of satellites for global coverage. A high degree of coverage redundancy and the use of on-orbit spares support the network reliability requirements.
3. THE NETWORK
End users will be served by one or more local service providers in the United States and in each host country. Terminals at gateway and user sites communicate directly with Teledesics satellite-based network and through gateway switches, to terminals on other networks.
The network uses fast packet switching technology based on the Asynchronous Transfer Mode ("ATM") technology now being used in Local Area Networks ("LAN"), Wide Area Networks ("WAN"), and the Broadband Integrated Services Digital Network ("B-ISDN"). All communication is treated identically within the network as streams of short fixed-length packets. Each packet contains a header that includes address and sequence information, an error-control section used to verify the integrity of the header, and a payload section that carries the digitally-encoded voice or data. Conversion to and from the packet format takes place in the terminals. The fast packet switch network combines the advantages of a circuit-switched network (low delay digital pipes), and a packet-switched network (efficient handling of multi-rate and bursty data). Fast packet switching technology is ideally suited for the dynamic nature of a LEO network.
Each satellite in the constellation is a node in the fast packet switch network, and has intersatellite communication links with eight adjacent satellites. Each satellite is normally linked with four satellites within the same plane (two in front and two behind) and with one in each of the two adjacent planes on both sides. This interconnection arrangement forms a non-hierarchical "geodesic," or mesh, network and provides a robust network configuration that is tolerant to faults and local congestion.
4. ADAPTIVE ROUTING
The topology of a LEO-based network is dynamic. Each satellite keeps the same position relative to other satellites in its orbital plane. Its position and propagation delay relative to earth terminals and to satellites in other planes change continuously and predictably. In addition to changes in network topology, as traffic flows through the network, queues of packets accumulate in the satellites, changing the waiting time before transmission to the next satellite. All of these factors affect the packet routing choice made by the fast packet switch in each satellite. These decisions are made continuously within each node using Teledesics distributed adaptive routing algorithm. This algorithm uses information transmitted throughout the network by each satellite to "learn" the current status of the network in order to select the path of least delay to a packets destination. The algorithm also controls the connection and disconnection of intersatellite links.
The network uses a "connectionless" protocol. Packets of the same connection may follow different paths through the network. Each node independently routes the packet along the path that currently offers the least expected delay to its destination. The required packets are buffered, and if necessary resequenced, at the destination terminal to eliminate the effect of timing variations. Teledesic has performed extensive and detailed simulation of the network and adaptive routing algorithm to verify that they meet Teledesics network delay and delay variability requirements.
5. COMMUNICATIONS LINKS AND TERMINALS
All of the Teledesic communications links transport data and voice as fixed-length (512) bit packets. The basic unit of channel capacity is the "basic channel", which supports a 16 Kbps payload data rate and an associated 2 Kbps "D-channel" for signaling and control. Basic channels can be aggregated to support higher data rates. For example, eight basic channels can be aggregated to support the equivalent of an 2B + D ISDN link, or 97 channels can be aggregated to support an equivalent T-1 (1.544 Mbps) connection. A Teledesic terminal can support multiple simultaneous network connections. In addition, the two directions of a network connection can operate at different rates.
The links are encrypted to guard against eavesdropping. Terminals perform the encryption/decryption and conversion to and from the packet format. The uplinks use dynamic power control of the RF transmitters so that the minimum amount of power is used to carry out the desired communication. Minimum transmitter power is used for clear sky conditions. The transmitter power is increased to compensate for rain.
The Teledesic Network accommodates a wide variety of terminals and data rates. Standard Terminals will include both fixed-site and transportable configurations that operate at multiples of the 16 Kbps basic channel payload rate up to 2.048 Mbps (the equivalent of 128 basic channels). These terminals can use antennas with diameters from 16 cm to 1.8 m as determined by the terminals maximum transmit channel rate, climatic region, and availability requirements. Their average transmit power varies from less than 0.01 W to 4.7 W depending on antenna diameter, transmit channel rate, and climatic conditions. All data rates, up to the full 2.048 Mbps, can be supported with an average transmit power of 0.3 W by suitable choice of antenna size.
Within its service area, each satellite can support a combination of terminals with a total throughput equivalent to over 125,000 simultaneous basic channels.
The Network also supports a smaller number of fixed-site GigaLink Terminals that operate at the OC-3 rate ("155.52 Mbps") and multiples of this rate up to OC-24 ("1.24416 Gbps"). Antennas for these terminals can range in size from 28 cm to 1.6 m as determined by the terminals maximum channel rate, climatic region and availability requirements. Transmit power will range from 1 W to 49 W depending on antenna diameter, data rate, and climatic conditions. Antenna site-diversity can be used to reduce the probability of rain outage in situations where this is a problem.
GigaLink Terminals provide gateway connections to public networks and to Teledesic support and data base systems including Network Operations and Control Centers ("NOCCs") and Constellation Operations Control Centers ("COCCs"), as well as to privately owned networks and high-rate terminals. A satellite can support up to sixteen GigaLink terminals within its service area.
Intersatellite Links ("ISLs") interconnect a satellite with eight satellites in the same and adjacent planes. Each ISL operates at 155.52 Mbps, and multiples of this rate up to 1.24416 Gbps depending upon the instantaneous capacity requirement.
6. EARTH-FIXED CELLS
One benefit of a small satellite footprint is that each satellite can serve its entire coverage area with a number of high-gain scanning beams, each illuminating a single small cell at a time. Small cells allow efficient reuse of spectrum, high channel density, and low transmitter power. However, if this small cell pattern swept the Earths surface at the velocity of the satellite (approximately 25,000 km per hour), a terminal would be served by the same cell for only a few seconds before a channel reassignment or "hand-off" to the next cell would be necessary. As in the case of terrestrial cellular systems, frequent hand-offs result in inefficient channel utilization, high processing costs, and lower system capacity. The Teledesic Network uses an Earth-fixed cell design to minimize the hand-off problem.
The Teledesic system maps the Earths surface into a fixed grid of approximately 20,000 "supercells," each consisting of nine cells . Each supercell is a square 160 km on each side. Supercells are arranged in bands parallel to the Equator. There are approximately 250 supercells in the band at the Equator, and the number per band decreases with increasing latitude. Since the number of supercells per band is not constant, the "north-south" supercell borders in adjacent bands are not aligned.
A satellite footprint encompasses a maximum of 64 supercells, or 576 cells. The actual number of cells for which a satellite is responsible varies by satellite with its orbital position and its distance from adjacent satellites. In general, the satellite closest to the center of a supercell has coverage responsibility. As a satellite passes over, it steers its antenna beams to the fixed cell locations within its footprint. This beam steering compensates for the satellites motion as well as the Earths rotation. (An analogy is the tread of a bulldozer that remains in contact with the same point while the bulldozer passes over).
Channel resources (frequencies and time slots) are associated with each cell and are managed by the current "serving" satellite. As long as a terminal remains within the same Earth-fixed cell, it maintains the same channel assignment for the duration of a call, regardless of how many satellites and beams are involved. Channel reassignments become the exception rather than the normal case, thus eliminating much of the frequency management and hand-off overhead.
A database contained in each satellite defines the type of service allowed within each Earth-fixed cell. Small fixed cells allow Teledesic to avoid interference to or from specific geographic areas and to contour service areas to national boundaries. This would be difficult to accomplish with large cells or cells that move with the satellite.
7. MULTIPLE ACCESS METHOD
The Teledesic Network uses a combination of multiple access methods to ensure efficient use of the spectrum. Each cell within a supercell is assigned to one of nine equal time slots. All communication takes place between the satellite and the terminals in that cell during its assigned time slot (see Figure 5). Within each cells time slot, the full frequency allocation is available to support communication channels. The cells are scanned in a regular cycle by the satellites transmit and receive beams, resulting in time division multiple access ("TDMA") among the cells in a supercell. Since propagation delay varies with path length, satellite transmissions are timed to ensure that cell N (N=1, 2, 3,...9) of all supercells receive transmissions at the same time. Terminal transmissions to a satellite are also timed to ensure that transmissions from the same numbered cell in all supercells in its coverage area reach that satellite at the same time. Physical separation (space division multiple access or SDMA) and a checkerboard pattern of left and right circular polarization eliminate interference between cells scanned at the same time in adjacent supercells. Guard time intervals eliminate overlap between signals received from time-consecutive cells.
Within each cells time slot, terminals use Frequency Division Multiple Access ("FDMA") on the uplink and Asynchronous Time Division Multiple Access ("ATDMA") on the downlink. On the uplink, each active terminal is assigned one or more frequency slots for the calls duration and can send one packet per slot each scan period (23.111 msec). The number of slots assigned to a terminal determines its maximum available transmission rate. One slot corresponds to a Standard Terminals 16 Kbps basic channel with its associated 2 Kbps signaling and control channel. A total of 1800 slots per cell scan interval are available for Standard Terminals..
The terminal downlink uses the packets header rather than a fixed assignment of time slots to address terminals. During each cells scan interval the satellite transmits a series of packets addressed to terminals within that cell. Packets are delimited by a unique bit pattern, and a terminal selects those addressed to it by examining each packets address field. A Standard Terminal operating at 16 Kbps requires one packet per scan interval. The downlink capacity is 1800 packets per cell per scan interval. The satellite transmits only as long as it takes to send the packets queued for a cell.
The combination of Earth-fixed cells and multiple access methods results in very efficient use of spectrum. The Teledesic system will reuse its requested spectrum over 350 times in the continental U.S. and 20,000 times across the Earths surface.
8. SYSTEM CONTROL
The network control hierarchy is distributed among the network elements. Terminals and other network elements use a packet-based protocol for signaling and control messages (similar to the ISDN D-channel and CCITT Signaling System No. 7). The network handles these "control" packets in the same manner as normal information packets.
The highest levels of network control reside in distributed, ground-based systems that are connected via GigaLink Terminals to the satellite network. Database systems provide terminal/user feature and service profiles, authentication and encryption keys, call routing data, and other administrative data. Administrative systems, from "network-level" to local "in-country" systems, provide secure access to various levels of the database and billing systems.
High-level call control functions reside in feature processors and gateway switches. The feature processor controls intra-network calls as well as the initial setup of inter-network calls which involve a gateway. Only control and signaling packets are passed to the feature processor; user packets are transmitted through the network over the path of least delay. A gateway switch controls calls that are connected through that switch.
The satellite-based switch node includes some mid-level call control functions in addition to its packet routing function. It manages the assignment, supervision, and release of all channels in its coverage area and the "hand-off" of channels to other satellites. It also monitors channel signal quality and initiates uplink power control when required.
Terminals control some low-level call control functions similar to those of a cellular or ISDN functional signaling terminal. These functions include user authentication, location registration, link encryption, monitoring and reporting of channel quality, channel assignments and hand-offs, and D-channel signaling.
9. SATELLITE AND LAUNCH OVERVIEW
The Teledesic satellite is specifically designed to take advantage of the economies that result from high volume production and launch. All satellites are identical and use technologies and components that allow a high degree of automation for both production and test. To minimize launch cost and the deployment interval, the satellites are designed to be compatible with over twenty existing international launch systems, and to be stacked so that multiple satellites can be launched on a single vehicle. Individual satellites, the constellation as a whole, and the COCCs are designed to operate with a high degree of autonomy.
The initial constellation includes a number of active on-orbit spares that can be used to "repair" the Network immediately if a satellite is removed from service temporarily or permanently. Routine periodic launches will be used to maintain an appropriate level of spares in each orbit plane. Launch vehicles and satellites that have reached the end of their useful life are deorbited. They disintegrate harmlessly on re-entry, and will not create space debris.
The full version of this article is available on Teledesic's web site.
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