Communication system and method using stochastically distributed orbiting satellites

Abstract

A wireless communication system for transmitting data to a ground station includes a plurality of stochastically distributed orbiting satellites equipped with a plurality of antennas that traverse a portion of the Earth's surface divided into zones. The ground station has a unique address that identifies itself and the zone in which it is located. A local area network associated with a ground node includes at least one satellite that stores an identifier of a satellite antenna paired with a ground station antenna to form a wireless link for transmitting the satellite's onboard data to the ground station. Other satellites in the local area network store the address of the ground node and an identifier of an antenna paired with an antenna in another satellite that also stores the address of the ground node. A wide area network includes at least one satellite, each of which stores an identifier of an antenna paired with an antenna of another satellite that stores a ground node zone to form at least one inter-satellite wireless link. If the data-carrying satellite is not within a local area network associated with the destination ground node or the wide area network, the satellite transmits data toward the ground node's zone. [Selection diagram] Figure 5

Description

[Technical Field]

[0001] [CROSS-REFERENCE TO RELATED APPLICATIONS] This application claims the benefit of U.S. Provisional Patent Application No. 62 / 697,250, filed July 12, 2018, and U.S. Provisional Patent Application No. 62 / 739,245, filed September 30, 2018, which are incorporated by reference as if fully set forth herein. [Background technology]

[0002] [Technical field to which the invention belongs]

[0003] The present invention relates to transmitting data from one terrestrial node to another or from one satellite node to another satellite node, and more particularly to a communications system and method that uses a novel routing protocol and node design for establishing wireless links between satellites and terrestrial nodes, and even more particularly to such a system and method that employs multiple satellites stochastically distributed at uncertain geolocations without requiring precise attitude control.

[0004] <Detailed explanation>

[0005] Applicant's U.S. Pat. Nos. 1,084,536, 1,085,200, and 1,0291,316, and International Publication WO 018 / 039292, which are incorporated by reference as part of this disclosure as set forth in their entireties, describe a number of innovative satellite-based wireless communication systems and methods. Certain preferred implementations of these systems use constellations of over 100 satellites in low Earth orbit at altitudes of approximately 500 miles. Until Applicant's approach described in these documents, the typical solution to the problem of creating a wireless link in a satellite-based communication system was to use satellites in tightly controlled orbits with precisely controlled attitudes. Conventional wisdom has suggested that this was the preferred method for ensuring that antennas on two satellites, or on a satellite and a ground station, were paired to enable the transmission of signals between them.

[0006] While this conventional approach typically supported inter-satellite communications, the need to maintain satellites in fixed orbits at tightly controlled attitudes required rocket thrusters and rocket fuel, which added to the size, expense, and weight of the satellite. Other possible approaches to attitude control included intelligent placement of the satellite's solar panels and mechanical means for manipulating them to maintain the satellite in a desired orientation, which also added to the satellite's weight and complexity. However, the larger and heavier the satellite, the more expensive it is to launch into orbit, and the more complex the design, the higher the cost of each satellite. Applicant's system breaks the paradigm of requiring tight control of satellite position and attitude by using small, lightweight satellites in untethered orbits that do not require attitude control. Eliminating the need for rockets, rocket thrusters, and other structural components allows for lighter, smaller, and cheaper satellites, potentially reducing the overall cost of implementing a global satellite-based communications system by orders of magnitude.

[0007] Applicant's previously disclosed satellite-based systems can nevertheless be made even more economical and reliable by employing more advanced satellite deployment strategies, routing protocols, satellite architectures, and antenna configurations. Approaches discussed herein include, but are not limited to, reducing the number of satellites or other types of aerial nodes, providing a limited degree of satellite attitude stabilization, restricting satellite orbits to latitudes near the Earth's equatorial or polar orbits, using aerial nodes other than satellites, using aerial nodes at various altitudes, using innovative antenna designs, using sophisticated algorithmic techniques to facilitate wireless links between nodes, and employing satellite configurations that enable launch and deployment using CubeSat vehicles (see Wikipedia entry "CubeSat," https: / / en.wikipedia.org / wiki / CubeSat). Summary of the Invention

[0008] One object of the present invention is to provide a space-based multi-node communication system and method that reduces the amount of information that must be exchanged between system nodes and minimizes the computations required to create a preferred and / or optimal wireless path for data communication from an originating terrestrial node to a destination terrestrial node.

[0009] The systems and methods described herein are particularly adapted for performing space-based communications using a probabilistically distributed constellation of satellites that rely on the probability of creating wireless links between satellites and between satellites and ground stations via antenna pairing. The detailed description of various embodiments that follows includes various routing strategies and satellite configurations, antenna architectures, and satellite deployment techniques to facilitate antenna pairing and wireless link creation.

[0010] In some aspects, the systems and methods disclosed herein include at least one satellite employing a routing protocol by referencing its geographic location, determined via onboard electronics interfacing with a global navigation satellite system. In other aspects, the routing protocol involves freeform routing, where some or all of the probabilistically distributed satellites in the constellation are unaware of their geolocation or the geolocation of other satellites.

[0011] In another important aspect, the present invention includes a routing protocol that can be used to support a distributed ledger maintained across a constellation of multiple probabilistically distributed satellites.

[0012] A further aspect of the present invention increases the probability of pairing antennas on different probabilistically distributed satellites in a constellation through novel satellite configurations with attitude stabilization. These satellite configurations can include unique antenna configurations to further increase the probability of pairing antennas on different satellites to create a wireless link.

[0013] As this description proceeds, it will be appreciated that many of the various aspects and features of the system nodes, and in particular those comprising the satellite embodiments and satellite-based routing protocols described herein, may be used in various combinations depending on the requirements and general purpose of a particular communication system.

[0014] This Summary is provided merely to introduce a selection of concepts in a simplified form that are described in more detail below. It is not necessarily intended to identify key or essential features of the subject matter claimed herein, nor is it intended for use as an aid in determining the scope of the claimed subject matter. [Brief explanation of the drawings]

[0015] The objects of the present invention will be better understood from the following detailed description of the preferred embodiments, taken in conjunction with the accompanying drawings, in which like numerals and letters refer to like features, and in which:

[0016] [Figure 1A] 1 illustrates the geometric principles associated with the use of satellites in low Earth orbit in the space-based communications systems disclosed and claimed herein. [Figure 1B] 1 illustrates the geometric principles associated with the use of satellites in low Earth orbit in the space-based communications systems disclosed and claimed herein.

[0017] [Figure 2] 1 illustrates generally an embodiment of a satellite suitable for use in the space-based communications system disclosed and claimed herein.

[0018] [Figure 3] A representation of the various operational components of the satellite depicted in Figure 2.

[0019] [Figure 4] Mercator projections of the Earth and orbital paths of satellites as shown in FIGS. 2 and 3 in systems for providing long-range electronic communications, where a first system embodiment includes a single satellite in a low Earth equatorial orbit and a second system embodiment includes a single satellite in a low Earth polar orbit.

[0020] [Figure 5] 4 is a Mercator projection diagram showing the orbital paths of satellites such as those shown in FIGS. 2 and 3 deployed at various altitudes in low Earth orbits with different inclinations relative to the equator, illustrating a further system embodiment for providing data transmission over long distances using a constellation of multiple stochastically distributed satellites.

[0021] [Figure 6]FIG. 6 is a schematic diagram illustrating a local area routing network including wireless links created to transmit data to terrestrial nodes in an embodiment of a long-range system including a multi-satellite constellation such as that shown in FIG.

[0022] [Figure 7] 7 is a flowchart illustrating a recursive logic method using the routing protocols described herein, including the local area routing network shown in FIG. 6, for transmitting data to a destination terrestrial node via a long-range multi-satellite constellation.

[0023] [Figure 8] 8 is a world map showing the locations of satellite and terrestrial nodes used to illustrate an exemplary application of the routing protocol described in connection with FIGS. 6 and 7. FIG.

[0024] [Figure 9] We present one way in which a system using satellites at different altitudes can reduce the number of radio links between distant terrestrial nodes.

[0025] [Figure 10] 1 shows an example of a multi-satellite route between two terrestrial nodes.

[0026] [Figure 11A] 6 illustrates a schematic representation of a rotating satellite according to an alternative embodiment of the system shown in FIGS. 4 and 5. [Figure 11B] 6 illustrates a schematic representation of a rotating satellite according to an alternative embodiment of the system shown in FIGS. 4 and 5. [Figure 11C] 6 illustrates a schematic representation of a rotating satellite according to an alternative embodiment of the system shown in FIGS. 4 and 5.

[0027] [Figure 12] FIG. 10 is a bottom perspective view of an alternative satellite embodiment of a circular cylindrical configuration.

[0028] [Figure 13] FIG. 13 is an exploded view of the circular sidewall of the satellite in FIG. 12 showing the placement of the satellite antennas.

[0029] [Figure 14] FIG. 13 is a side view of the satellite of FIG. 12.

[0030] [Figure 15] FIG. 13 is a top view of the satellite of FIG. 12.

[0031] [Figure 16] FIG. 16 is a cross-sectional view taken along line 16-16 in FIG.

[0032] [Figure 17] FIG. 17 is a cross-sectional view taken along line 17-17 of FIG. 16.

[0033] [Figure 18] FIG. 10 is a perspective view of another alternative satellite configuration.

[0034] [Figure 19] 10 illustrates an alternative antenna configuration that can be incorporated into the satellites shown in the previous figures to improve wireless link creation and data transmission in the space-based systems described herein.

[0035] [Figure 20] 20 is a schematic diagram of a control circuit in a satellite having the antenna configuration of FIG. 19.

[0036] [Figure 21] FIG. 1 is a schematic isometric view of a CubeSat implementation of a satellite that can be used in the systems described herein.

[0037] [Figure 22] 1A-1C illustrate several examples of various types of antenna-based communication systems that may be implemented using the concepts disclosed herein.

[0038] Although the drawings are not strictly to scale, those skilled in the art will nevertheless readily understand that the following detailed description of the preferred embodiments is sufficient to make and use the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0039] The following detailed description is intended to provide specific examples of particular embodiments that illustrate various ways of implementing the claimed subject matter. It is written to take into account the level of knowledge of those skilled in the art to which the claimed subject matter pertains. Accordingly, certain details may be omitted as they are not necessary to enable such persons to practice the embodiments described herein.

[0040] The following detailed description of certain preferred embodiments of the present invention is organized as follows. I. Definition II. Basic principles of communication systems and satellite design A. Satellite Design: Antenna Configuration and On-board Control Circuits B. Single-Satellite Dedicated Messaging System 1. Single-satellite messaging system – equatorial orbit 2. Single-Satellite Messaging System - Polar Orbit C. Multiple Satellite Communication Systems 1. Multiple satellite constellations 2. Routing and Data Transmission Protocol D. Distributed Ledger Systems 1. Blockchain principles applied to wireless routing 2. Distributed Ledgers in Probabilistic Systems III. Alternative Satellite Construction and Deploying Strategies A. Rotating satellite 1. Counter-rotating satellites 2. Satellites rotating at different angular velocities 3. Other Considerations B. Satellite configuration with attitude stabilization C. Alternative Antenna Configurations D. CubeSat compatibility IV. Further Applications of the Disclosed Concepts V. Summary and Conclusions

[0041] 1. Definition

[0042] The following description uses a number of terms intended to have particular meanings. One of the central concepts of certain embodiments of the system described and claimed herein is that satellites may be in "stochastically distributed" or "unconstrained orbits," both of which are related to the term "random orbit" used in Applicant's prior U.S. Patent Nos. 10,084,536, 10,085,200, 10,291,316, and WO 2018 / 039292. The intended meaning of these terms is that once deployed in orbit, a satellite is permitted to assume any orbital path without the application of motive force to the satellite by its onboard propulsion system. However, none of the terms are intended to exclude the initial deployment of a satellite at a particular orbital inclination, altitude, or attitude, or at a particular geolocation relative to other satellites in the system. Stated differently, a "stochastically distributed," "unconstrained," or "random" orbit refers to a satellite that is deployed such that its position relative to other satellites and the Earth is not controlled at any time after insertion into the orbit, although it may initially be deployed in a manner designed to provide coverage (service area) of a particular swath of the Earth's surface. While satellites need not be randomly deployed in a mathematical sense, it is within the scope of these terms to use mathematical methods to determine satellite deployment direction, inclination, altitude, velocity, etc., which take into account the geographic area of ​​the Earth served by a radio path using one or more satellites. Furthermore, individual satellites may be launched in different orbital directions (eastward or westward around the Earth) in combination with any of the aforementioned or other deployment techniques. For example, satellites may be released at different velocities and in different directions from a launch vehicle traveling in an orbital direction (i.e., generally eastward or westward), so that after a period of time, they will separate into "random" orbits in an essentially unconstrained manner. This frequently causes constellations of multiple satellites to appear to Earth's observers as stochastically distributed in random orbits.

[0043] In the systems described herein, the terms "passive attitude control" and the related term "no active attitude control" as applied to a satellite mean that the satellite does not have an attitude control mechanism with parts that are moved to different positions by a powered onboard device to intentionally change the satellite's attitude relative to an external reference frame. Examples of active attitude control mechanisms are propulsion systems with thrusters that can impart momentum to the satellite to rotate it, or mechanical actuators with moving parts that are used to change the satellite's center of gravity or angular momentum, or the position and / or orientation of the satellite's solar panels. These terms do not exclude the use of passive means for changing or controlling attitude without moving parts; satellites tend to adopt a particular attitude over time due to their structure and the materials used in their manufacture. Furthermore, these terms do not exclude the use of various approaches, such as using means to stabilize the satellite's attitude within certain limits. This can include techniques such as selectively switching one or more electromagnet arrays to change their interaction with the Earth's magnetic field in a way that affects the satellite's attitude. Similar techniques now known or developed in the future are also covered by the terms "passive attitude control" and "no active attitude control."

[0044] Other terms used in the following description are "data communications" and "routing messages." Unless otherwise indicated explicitly or by context, "data communications" includes content (digitally or otherwise) transmitted over wireless links between satellites or between satellites and ground stations. The system described herein is particularly well-suited for transmitting data in packets, defined in the generally accepted sense herein as a collection of digital data having a portion (sometimes called a "payload") representing the content of the transmission and a control portion (sometimes called a "header" or "trailer") containing information that enables the payload to be successfully delivered, such as source and destination addresses, error detection codes, and sequence information. Routing messages are radio signals transmitted from nodes (ground or airborne) in the system that contain information or have characteristics that can be used to determine the suitability of a node for inclusion in a multilink. A given radio signal can include both routing messages and data communications. Throughout this description, the term "radio" is not limited to electromagnetic radiation at frequencies commonly referred to as radio waves. It is meant to encompass electromagnetic radiation of any frequency capable of transmitting information, including light, microwave, VHF ("very high frequency"), UHF ("ultra high frequency"), etc.

[0045] A "node" is a physical object that transmits radio signals intended to be received by other nodes and has one or more transceivers for receiving radio signals transmitted from other nodes. A node may be a ground station on the Earth (a terrestrial node) or a transceiver above the Earth's surface (an "aerial node"). Aerial nodes include, but are not limited to, satellites orbiting the Earth, balloons, and unmanned aerial vehicles. A terrestrial node may either be a fixed structure on the Earth's surface, or one or more transceivers mounted on a low-altitude unmanned aerial vehicle (a "drone"), or one or more transceivers mounted on a balloon (an "elevated terrestrial node") maintained in a substantially fixed position, typically at an altitude of about 500 feet or less. Elevated terrestrial nodes allow more users in sparsely populated areas to connect to the communication system.

[0046] As those skilled in the art will recognize, in describing the subject matter disclosed and claimed herein, the control circuits and components described and depicted in the various figures are intended to be illustrative of any electronic computer system capable of performing the functions attributed thereto. Such computer systems typically include necessary input / output interface devices, a central processing unit (CPU) with a suitable operating system, application software for executing program instructions, and transient and non-transient memory modules. Furthermore, terms referring to elements of a system are used herein for ease of reference. For example, terms such as "component," "module," "system," "device," and "interface" are generally intended to refer to any computer-related entity—hardware, hardware and software (firmware), software, or a combination of running software—unless the context clearly dictates otherwise. Furthermore, the terms "module" or "component" do not imply a self-contained structure per se, but rather may include various hardware and firmware that combine to perform a particular function. In that regard, a component or module may be, but is not limited to, a processor, processor object, executable file, thread of execution, program, and / or process running on a computer. By way of example, both an application running on an electronic computing device and the device itself may be a component. One or more components can reside within a process and / or thread of execution and a component can be localized on one computer and / or distributed between two or more computers.

[0047] II. Basic principles of communication systems and satellite design

[0048] In communications systems in which airborne nodes, such as satellites, exchange radio signals with terrestrial nodes and / or other satellites, one of the important parameters is the distance from the satellite to the horizon on the Earth's surface. Figures 1A and 1B illustrate the relationship between the altitude of an airborne node, such as satellite S, and its surface "footprint," defined by the distance from the satellite to the horizon EH. Ground stations beyond that distance cannot see the satellite and therefore cannot exchange radio signals with it. If satellite S is at an altitude AL of 200 miles, its footprint (area) on the Earth's surface is related to its distance to the Earth EH by the equation DH = [(R + 200 )2 -R 2 ] 1 / 2 where R is the radius of the Earth E. If R is assumed to be 4,000 miles, then DH is approximately 1,280 miles. This is the theoretical radius from which a satellite can be seen from a point on the Earth. The satellite's footprint (the surface area of ​​the Earth visible to the satellite) is π*DH 2 <<5,100,000 square miles (those skilled in the art will understand that these theoretical values ​​will not be accurate in all instances because the line of sight to the satellite may be shallow at the horizon and trees, buildings, hills, etc. can reduce the actual distance and footprint). For the same reason, the distance at which two satellites in circular orbits at the same altitude can see each other is roughly twice the distance DH. One of the challenges in any satellite-based communications system is designing the satellites and ground stations so that their respective antennas can pair to create a radio link over these large distances.

[0049] For reference in the description of various embodiments below, the following table sets out the distance to the horizon (DH), footprint, and duration (length of time required for one orbit) for satellites at different altitudes.

[0050] [Table 1] This table highlights one of the trade-offs involved in designing satellite-based communications systems: while horizon distance and corresponding footprint increase with increasing orbital altitude, the strength of the radio signal between the satellite and the ground also decreases with increasing altitude. This and other design considerations are discussed in the following sections.

[0051] A. Satellite Design: Antenna Configuration and On-board Control Circuits

[0052] Applicant's previous U.S. Patent Nos. 10,084,536, 10,085,200, and 10,291,316, as well as International Publication No. WO 2018 / 039292, disclose satellite designs capable of creating wireless links between satellites and ground stations, and between satellites. These satellite designs can influence the routing protocols described herein and are used in describing certain fundamental features of these protocols. Improved satellite designs and deployment strategies for that purpose also form part of this disclosure and are discussed further below.

[0053] FIG. 2 is a schematic diagram of an embodiment of a satellite 10 that can be used as an airborne node in the communications system described further below in this Section II. The salient features of the structure and operation of this satellite are fully described in the above-referenced patents and publications and are repeated here for the reader's convenience. While satellite 10 is shown with an outer casing in the shape of a sphere centered at CT, those skilled in the art will recognize that the satellite can have a different shape if dictated by other design considerations, as described further below in Section III. While certain features of the satellite are described with reference to a coordinate system having mutually orthogonal x, y, and z axes, this coordinate system is used strictly for illustrative purposes in describing the features of the satellite. For example, the coordinate system imposed in FIG. 2 can be thought of as being attached to the satellite and changing its angular orientation relative to the Earth as the satellite changes orientation (attitude).

[0054] The exemplary satellite 10 includes multiple antenna modules 12, one of which is shown in highly schematic form in FIG. 2 for illustrative purposes. Each antenna module in this example comprises a directional antenna that transmits and receives radio signals with greater power in a predetermined direction. This embodiment uses circular dish parabolic antennas, each occupying a solid angle Ω with an apex at a point within the satellite. Antenna reflectors (omitted from the drawing for clarity) may be recessed below the surface of the satellite. The number of discrete antenna modules incorporated into the satellite will depend on the particular application and antenna design of the system. Additionally, the antenna modules may be configured in any other configuration that enables them to perform the functions described herein. In one embodiment, Ω in steradians would be selected to enable a specific number of antenna modules distributed around the satellite to transmit and receive radio signals over a sufficiently large spherical area, and to receive and transmit radio signals from and to ground station transceivers and antennas on other satellites to perform the operation of the system described below. The actual configuration of the antenna modules 12 can be determined using known antenna design principles to achieve that goal.

[0055] A satellite used in this system would be structurally robust enough to withstand the stresses of launch and prolonged exposure to the hostile environments it would encounter in orbit, and large enough to accommodate the various electronic and mechanical components required for its operation, as described in more detail below in connection with FIG. 3.

[0056] It will be appreciated that satellites and antennas suitable for use in the present system can take different forms, depending on tradeoffs familiar to those familiar with engineering complex systems. One aspect of the particular method described herein involves transmitting radio signals from multiple antennas on one or more satellites for reception by antennas on other satellites. Increasing the number of antennas on a satellite node will increase the coverage of radio signals transmitted and received from other nodes, thereby increasing the probability that a signal from one node will be received by another node. It will also be appreciated that more antennas per satellite may allow for a reduction in the number of satellites placed in orbit in a multi-satellite system. While such satellites would be more expensive and heavier, thus increasing launch costs, other factors may offset the increased cost, as fewer satellites may need to be launched. Those skilled in the art will also recognize that the systems described herein may be implemented using satellite nodes having a collection of antennas transmitting with less than full 360° spherical coverage.

[0057] The satellite 10 also includes a plurality of solar panels, three of which, 14a, 14b, and 14c, are shown in FIG. 2. In the illustrated embodiment, the solar panels are oriented in mutually perpendicular planes and spaced equidistantly around the satellite 10. For purposes of describing the positions and orientations of the solar panels in this embodiment, the satellite equator 16 is defined as the great circle intersected by the satellite surface by a plane parallel to the xy plane and passing through the center of the sphere, CT. The reference meridian 18 is defined as the great circle intersected by the satellite surface by a plane parallel to the xz plane and passing through the center of the sphere, CT. Finally, the standard meridian 20 is defined as the great circle intersected by the satellite surface by a plane parallel to the yz plane and passing through the center of the sphere, CT. Solar panel 14a is mounted to the satellite by a suitable mounting structure 22a at the intersection of the equator 16 and the reference meridian 18. Solar panel 14b is mounted to the satellite by a suitable mounting structure 22b at the intersection of the equator 16 and the normal meridian 18. The solar panel 14c is then mounted to the satellite at the intersection of the reference meridian 18 and the standard meridian 20 by a suitable mounting structure 22c.

[0058] Solar panels are generally planar with solar cells distributed on one or both surfaces to generate electricity when the solar cells are exposed to sunlight. For maximum effectiveness, planar solar panels are mounted in mutually orthogonal planes to ensure an adequate number of solar cells are exposed to sunlight regardless of the satellite's angular orientation. In the illustrated embodiment, solar panel 14a resides in the xz plane, solar panel 14b resides in the xy plane, and solar panel 14c resides in the yz plane. It will be understood that the satellite also includes three more companion solar panels, where the equator, reference meridian, and standard meridian intersect on opposite sides of the satellite. The companion solar panels (indicated by a prime (') in FIG. 3) are preferably oriented in the same plane as their counterparts 14a, 14b, and 14c shown in FIG. 2. Each solar panel is depicted as being perpendicular to the satellite's surface so as not to interfere with the transmission and reception of radio signals by antennas adjacent to the solar panel.

[0059] It will be understood that FIG. 2 is intended only to illustrate features of the satellite 10 necessary for understanding the present embodiment. Those skilled in the art will appreciate that an actual satellite for implementing the present system may have design features not shown in the schematic diagram of FIG. 2. For example, good design practice may dictate that the antenna apertures be recessed below the surrounding surface of the satellite to reduce the possibility of impact damage from space debris. Alternatively, additional protection may be provided by covering each antenna aperture (recessed or not) with a sheet of material that is transparent to signals transmitted by and received at the satellite. The design and placement of the solar panels 14 shown in FIG. 2 are also highly schematic, and the system disclosed and claimed herein is not limited to any particular solar panel configuration, placement, or means of placement. In another variation, the antennas can be positioned so that the solar panels are mounted flush with the satellite surface in the spaces between the antenna apertures.

[0060] FIG. 3 illustrates schematically the various components housed by a satellite 10 (link node) for generating a radio path over which data transmissions can be sent and received from other nodes. As those skilled in the art will readily appreciate, the control circuits and components illustrated and depicted in the various figures in the description of this and other embodiments and aspects of the communications system comprising the subject matter disclosed and claimed herein are meant to be exemplary of any electronic computer system capable of performing the functions attributed thereto. Such computer systems typically include necessary input / output interface devices and a central processing unit (CPU) with appropriate operating system and application software for executing program instructions. A satellite's onboard computer system also has appropriate memory modules for storing information. Furthermore, terms referring to elements of the system are used herein for ease of reference and do not limit their function or mode of operation.

[0061] Referring more particularly to FIG. 3, satellite 10 is shown in a view in the xz plane of FIG. 2. It will be understood that FIG. 3, like many other depictions used herein to describe the subject communications system and their components, is not to scale. As shown in FIG. 2, solar panels 14a and 14c are shown, along with the diametrically opposed companion solar panels 14a' and 14c' described above. Also depicted are multiple antenna modules 12a, 12b, 12c, 12d, 12e, and 12f, intended as a schematic representation of all antenna modules aboard satellite 10 for transmitting and receiving wireless signals as described above in connection with FIG. 2. This schematic is intended to convey the principles of operation of this embodiment, in which multiple antenna modules can be combined to transmit and receive wireless signals to and from nodes in multiple radial directions. (However, as previously mentioned, the system described herein can also be implemented using link nodes having antenna arrays transmitting with less than full 360° spherical coverage.)

[0062] The satellite 10 includes a power module 30 capable of providing a reliable source of power for operating the satellite components. The power module 30 includes a rechargeable battery that is charged by electricity generated by solar panels. Appropriate power conditioning equipment provides constant power to the various electronic components carried by the satellite, even if the solar panels spend half of each satellite orbit outside the view of the sun. In addition to the power module, the satellite includes a central processing unit 40 having an operating system module 42 that stores operating software for controlling the various functions of the satellite. As shown in FIG. 3, the CPU 40 is operatively connected to all of the antenna modules 12 via power and data links 40a, 40b, 40c, 40d, 40e, 40f, etc.

[0063] Figure 3 also shows three main operating modules under the control of the operating system module 42. The global navigation satellite system (GNSS) module 44 communicates with global navigation satellite systems. Examples include the U.S.-based Global Positioning Satellite (GPS) system, the European Union's Galileo system, Russia's GLONASS system, and China's BeiDou system. This module enables satellites to determine their position relative to the Earth's surface in a manner employed by all known global navigation satellite systems. Radio signals exchanged between system nodes via the antenna module 12 are used by a path generation module 46, which includes antenna pairing circuitry for executing logic described further below, to generate radio paths comprising radio links supporting data communication between two or more nodes. The data transfer module 48 includes data transmission circuitry for controlling the transmission of data (content) between nodes, as described in more detail below. As alluded to above, the illustration in FIG. 3 of separate modules for route creation and data movement does not necessarily mean that identifying the radio links used in a radio path and transmitting data between the linked nodes is other than part of a more or less single process of creating a preferred radio path for transmitting data communications from one satellite to another, or between a satellite and a terrestrial node.

[0064] Another important feature of certain systems and methods described herein is that the satellites can operate without active on-board attitude control. However, certain configurations for providing passive attitude control to stabilize the satellite attitude within certain limits can improve system operation, as described in Section III.B, without substantially adding to the costs of manufacturing and launching the satellite. Thus, in one basic form, the satellites are capable of orbiting regardless of their angular orientation. It is expected that the satellites can be deployed from a launch vehicle such as a space station. In some embodiments, it may be preferable to attempt to deploy them with as little angular velocity as possible, although in certain embodiments, no special effort is required in that regard. In some system embodiments described herein, the satellites can tumble as they orbit and still create a radio path, meaning that the satellites do not need to be in a known, predetermined orientation (attitude). Satellites can be stochastically distributed through unconstrained orbits, and the lack of active attitude control, or in some cases, attitude stabilization within certain limits, eliminates the need for heavy and costly on-board systems to operate on-board mechanisms, such as rocket thrusters, to change or maintain the satellite's position or attitude. Additionally, each satellite may include tracking telemetry to detect when its orbit is deteriorating and needs to be replaced, and to comply with any national or international protocols applicable to the orbital body, although providing such telemetry is expected to be relatively simple and inexpensive.

[0065] B. Single-Satellite Dedicated Messaging System

[0066] The satellites described above are sufficiently inexpensive to manufacture and launch that they can be used in private communications systems that are particularly suited to transmitting email communications. The basic principles underlying such a system will be explained with reference to Figure 4, which is based on a standard Mercator projection of the Earth showing the Equator (0° latitude), the Tropic of Cancer (23.5° North latitude), and the Tropic of Capricorn (23.5° South latitude), and also shows reference lines at 0° longitude, 90° East, 180° East, and 270° East (90° West).

[0067] 1. Single-Satellite Message System - Equatorial Orbit

[0068] According to Greg Weiler's proposed "03b" satellite communications system, it has been observed that the population of the developing regions between the Tropics of Cancer and Capricorn generally has limited or no access to the Internet. See the Wikipedia entry "03b" (https: / / en.wikipedia.org / wiki / 03b_(satellite)). This refers to the 3 billion people who live in a swath of the Earth's surface centered on the equator and who are said to have limited or no access to the Internet. However, the hundreds of millions of dollars spent to date to partially implement the 03b system appear to rely on expensive traditional communications satellites equipped with rocket thrusters to maintain tightly constrained orbits and attitudes. Applicant's system disclosed herein can provide communications services to the same population for a fraction of the cost.

[0069] In this embodiment, the orbital path OP depicted by the double dashed line in FIG. E This embodiment will be described by reference to a single satellite S100 in a satellite system. It will become apparent as the description proceeds that such a single satellite system has a specific purpose, but allows communication with remote terrestrial locations that are difficult to reach by electronic communication. In this embodiment, satellite S100 E2 and 3, launched into a circular orbit from a location near the equator, such as the Guiana Space Center GS used by the European Space Agency and the French National Center for Space Studies (CNES). This point is at 5 degrees north latitude, so a satellite launched due east (or west) would follow an orbital path OP illustrated as a very shallow sinusoidal wave centered on the equator with a north-south maximum distance of about 340 miles (covering a band about 680 miles wide). E The following discussion takes advantage of the fact that satellites constructed as described herein are very inexpensive to build and launch into orbit, allowing a group of individual users or a small business to launch a single satellite and support a private messaging system that limits its use to system subscribers only.

[0070] In this embodiment, we will use an example of a satellite orbiting at an altitude of approximately 400 miles. From Table 1 above, satellite S100 should be able to see all or substantially all of the 3,200 mile wide points on the Earth's surface bounded by the Tropic of Cancer and the Tropic of Capricorn during each orbit. This is because the orbital path OP E First and second exemplary footprints F1 having a diameter of approximately 3,600 miles are shown at various locations within the E and F2 E (Table 1, 400-mile-altitude orbit). Furthermore, for a 400-mile-altitude off-equatorial orbit, the orbital path "shifts" with respect to the ground by about 24° (≈1,600 miles) with each successive orbit (a depiction of which is omitted from Figure 4 for clarity). Thus, even with the slightly off-equatorial orbit shown in Figure 4, portions of the Earth's surface north and south of the tropics would see the satellite every day. If a satellite could be deployed with an orbital path that precisely tracks the equator, it would be visible to all, or nearly all, of the 3,200-mile-wide swath of the tropics between every orbit.

[0071] As an example of how one ground station communicates with another in such a system, consider a subscriber located in Uyo, Nigeria, who wants to send a message to another subscriber in Leyte, Philippines. Uyo is at 5 degrees north latitude (about 340 miles from the equator), and Leyte is at 11 degrees north latitude (about 750 miles from the equator). A satellite launched from the Guiana Space Center (5 degrees north) into a 400-mile high orbit will pass within the field of view of both Uyo (5 degrees north) and Leyte (11 degrees north) in each orbit. This is called F1. E and F2 E The footprint is shown.

[0072] In a typical routing protocol, a Uyo subscriber composes a message on their electronic device with an optional app to be sent to a Leyte user. The app can provide address information identifying the latitude and longitude of the Leyte subscriber's ground station. This message cannot be uploaded to the satellite until it is within view of Uyo. Because the satellite's orbital period is 97 minutes (Table 1), the user may have to wait almost that long for the message to be uploaded. Typically, the user's device communicates with a ground station with multiple directional antennas that sends emails periodically (e.g., every minute) until the satellite returns a acknowledgment handshake to the ground station that the transmission was received. Repeated transmissions by the ground station can occur in the background. Optionally, the satellite can send a notification to the user when the satellite successfully receives the message.

[0073] The satellite stores destination information in its route generation module 48 in the form of Leyte's longitude and latitude. The satellite also knows its location via the GNSS module 44. When the satellite is within view of the Leyte destination coordinates, its data transfer module begins transmitting messages over all of its antennas 12. Thus, Uyo is at 7 degrees east longitude and Leyte is at 125 degrees east longitude, meaning it takes approximately 32 minutes or less for the satellite to be within range of the Leyte destination ground station after receiving the message from the Uyo origin ground station. Upon receiving the message, the destination ground station returns a confirmation handshake to the satellite. Preferably, the satellite stores the confirmation handshake in some way (such as setting a flag) and transmits it to the Uyo ground station to complete its orbit. It will be understood that the satellite can transmit a message directly to the destination ground station if it is within view of the satellite (a two-hop route).

[0074] A system with a single satellite in equatorial (or near-equatorial) orbit at a very low altitude is limited in the area of ​​the Earth's surface accessible to the system. Deploying satellites at higher altitudes increases coverage, but makes it more difficult to create a radio link with a ground station because radio signals attenuate as they travel longer distances. An alternative approach could use multiple satellites at low altitudes, substantially equally spaced in equatorial (or near-equatorial) orbit. This does not substantially increase the cost of the system due to the low cost of manufacturing and launching satellites.

[0075] In the above example, the user (or an app on their device) needs to know the full address information of the destination ground station. In an alternative embodiment, a user associated with a particular ground node can send a traditional email to a user associated with another ground station. In this embodiment, the sender enters the address information in the familiar email format "recipient@internetserviceprovider.xxx." The user device can include an app that knows the location of the ISP's server on the ground that has access to the ISP's email network. When the user uploads an email to the satellite, it includes the longitude and latitude of the ISP's server, and when the satellite is within range of the server, it sends the email as described above. The ISP then uses its network to deliver the email.

[0076] 2. Single-Satellite Messaging System - Polar Orbit

[0077] Figure 4 also shows, in dash-dot lines, the ground orbit of a single satellite, S100P, launched in a substantially circular polar orbit at an altitude of 200 miles. At that altitude, the satellite has an orbital period of approximately 91 minutes, orbiting the Earth approximately 16 times each day. The ground orbit thus follows successive polar orbital paths, OP1p, OP2p, OP3p, OP4p, OP5p, OP6p, etc., covering approximately 22 degrees of longitude. The ground orbits of these six orbital satellites are shown for a longitudinal swath encompassing Uyo and Leyte. (The lines representing these orbital paths are broken across the central latitude for clarity.) On the left side of Figure 4, the polar-polar orbital paths OP3p, OP4p, OP5p, and OP6p are shown in their entirety on the opposite side of the Earth (180 degrees to the right of their respective counterparts in the figure). The 1,200-mile diameter footprint FPo at the equator is shown for the "left" footprint of orbital path OP3p (see Table 1 for the 200-mile high orbit). The dashed circle FPo represents the footprint at the equator of satellite S100P on orbital path OP4p, and the dashed-dotted strip FP 45shows the satellite footprint for the same orbital path at 45 degrees north latitude (the satellite footprint is actually circular on the ground, but due to distortions introduced by the Mercator projection, it gets longer on the drawing as the satellite moves further from the equator). It can be seen from Figure 4 that every point on the Earth's surface "sees" satellite S100P at least once each day.

[0078] Sending a message from Uyo, Nigeria, to Leyte, Philippines, can proceed similarly to that described above with respect to a single satellite in equatorial orbit. A user in Uyo uploads a message with address information identifying the latitude and longitude of the Leyte subscriber's ground station. This message cannot be uploaded to the satellite until it is within view of Uyo, which could take nearly 12 hours if the satellite has just left view of Uyo. From the size of the footprint FP0, it can be seen that it could take up to six orbits, or approximately 9 hours at 91 minutes per orbit (Table 1), for a satellite carrying email to come within view of the destination coordinates in Leyte. While this is longer than the time required for a satellite in equatorial orbit, placing satellites in polar orbit allows communication between any two points on the Earth's surface, not just a strip on either side of the equator. Furthermore, the footprint FP0 45 indicates that at latitudes far from the equator, satellites are available to many ground stations in populated areas such as North America and Western Europe for only one or two orbital passes. In fact, when a satellite receives a message, it may be within view of the destination ground station.

[0079] In an alternative embodiment, a polar orbiting system could use an ISP's server to send email as described above, rather than waiting for the satellite to complete several orbits before it can transmit its message to a distant destination ground station. This often makes a single satellite polar orbiting messaging system more attractive, as it substantially reduces the time it takes for a mail message to reach its destination.

[0080] Those skilled in the art will appreciate that a single satellite orbiting in an orbital plane inclined to the equator has certain advantages over systems in which it is in a 0° orbital plane (around the equator) or a 90° orbital plane (polar orbit). For example, the concomitant increase in coverage area, as described above, allows messages to be sent directly from the satellite where the message was uploaded to the destination ground station, but serves a wider area. Increasing the number of satellites makes these types of two-hop routes more likely to be established over a particular area (because more satellites are available to receive messages from ground stations in that area) and also more likely to be established over a larger area (because more areas have at least one satellite visible at a particular time).

[0081] The system described in this Section II.B. is very inexpensive and, as mentioned above, is suitable for private messaging systems, where a user or small or medium-sized enterprise (SME) can launch a single satellite and limit use to system subscribers only. However, the long potential latency period (the time between when a user sends a message and when it is received) in a single satellite system may be unacceptable to certain users. It is also somewhat impractical for accessing and using the Internet for other purposes, but the described system is fully scalable and can be made more functional for those applications by simply adding more satellites. Because satellite manufacturing and launch costs are minimal, even small and medium-sized enterprises can take advantage of this technology.

[0082] C Multiple satellite communication system

[0083] In Section II.C., we discuss systems involving multiple stochastically distributed satellites in orbits inclined at different angles relative to the equator. These kinds of systems can be used in a variety of applications, not just data communications. For example, deploying a satellite constellation and using a data communications routing protocol according to the principles described in this section can also support a space-based distributed ledger implementation, as described in Section II.D. below.

[0084] 1. Multiple satellite constellations

[0085] Figure 5 will be used to discuss an exemplary system that uses multiple satellites at different altitudes and inclinations to reduce latency and enhance the functionality of the basic email system described above. The drawing shows satellites in four orbits with different inclinations. The first orbit, OT1, shown in double dashed lines, represents six satellites deployed in a circular orbit around the equator at 200 miles altitude from the Guiana Space Center (GS) at 5 degrees north latitude. The second orbit, OT2, shown in dashed lines, represents six satellites deployed in a circular orbit at 200 miles altitude from the Satish Dhawan Space Center (SD) in India (13 degrees north latitude). x The third orbit OT3 shown by the long dashed line represents the satellite S3 deployed in a circular orbit at an altitude of 400 miles from Cape Canaveral (CC) in Florida (28 degrees north latitude). x The fourth orbit, OT4, shown in short dashed lines, represents satellite S4x deployed in a circular orbit at an altitude of 800 miles from the Baikonur Cosmodrome in Kazakhstan (45 degrees north latitude). For purposes of illustration, Reykjavik, Iceland is also shown at 64 degrees north latitude, but it will be understood that these are meant to be examples of the orbital tracks that satellites in the system may assume. The orbits may be either forward or reverse, and similarly, may be circular or elliptical, or some satellites may be in one type of orbit and others in the other type (i.e., any combination of forward, reverse, circular, and elliptical).

[0086] An exemplary embodiment, comprising 25 satellites in the configuration shown in Figures 2 and 3, each in orbital orbits OT1 and OT2, designed to primarily serve the equatorial region between the Tropics of Cancer and Capricorn, will be used to illustrate some of the basic principles of a first routing protocol for transmitting communications in a multi-satellite system. The satellites in orbit are processed as described above in connection with Figure 4, so that after a certain time, a ground observer will see them randomly (probabilistically) distributed in the sky. The amount of time required to achieve the probability distribution can be reduced by judiciously timing the deployment of satellites in each orbital orbit, for example, by deploying satellites in specific orbital orbits at substantially equal intervals. While it is theoretically possible to use sufficiently sophisticated algorithms to predict, or at least estimate, the positions of satellites as a function of time and thus predetermine deployment timing, the present system does not require prediction of the positions of satellites relative to one another. This is because, as a stochastic system, it relies on the probability of establishing radio links between different airborne nodes and between airborne and terrestrial nodes. The satellites in orbital orbits OT1 and OT2 are distributed among satellites S1 in orbit OT1, and among satellites S2 in orbit OT2. x (Fig. 4 Orbital path OP E The dashed-dotted circle FP1 and the satellite S2 in orbit OT2 are x has a footprint of 5,000,000 square miles, represented by the dotted circle FP2 (see 200 mile high orbit in Table 1).

[0087] One consideration in a system using multiple satellites in unconstrained probabilistic orbits is how many satellites are likely to be within line-of-sight from a given point on the Earth's surface at any given time. In this example, the area of ​​the swath of Earth between the Tropics of Cancer and Capricorn is approximately 80,000,000 square miles (40% of the Earth's surface, which is approximately 200,000,000 square miles). With 50 satellites in orbits OT1 and OT2, each satellite "covers" approximately 6.25% of that swath (5,000,000 square miles divided by 80,000,000 square miles). Therefore, any point on the surface between the tropics will, on average, "see" at least 3 of the 50 satellites (50 x 0.0625 = 3). At the same time, there is a 93.75% probability that no satellites will be visible from a particular point on Earth between the tropics. With 50 satellites, there is a 0.9375 chance that any given point on Earth in that region will not be able to see at least one satellite. 50 0.040 (i.e., about 1 in 25). Furthermore, the system is fully scalable by adding satellites to the constellation. For example, the probability that any given point on Earth will not be able to see at least one satellite is 0.9375 times lower when the constellation is 100 satellites (0.9375). 100 ≒0.0016), and by a factor of about 400,000 if the constellation contains 200 satellites.

[0088] The number of other satellites that any given satellite can "see" is also an important factor in assembling a multi-satellite radio path; in this embodiment, each satellite can theoretically "see" approximately 2,600 miles above the horizon (2 × D from Table 1). Interference from ground structures in a given satellite's horizon EH may reduce that distance, so 2,400 miles is likely a more conservative estimate. The area of ​​a circle with a radius of 2,400 miles is approximately 18,000,000 square miles, which is 22.6% of the 80,000,000 square mile area intersected by the 50 satellites in the constellation. This means that, on average, any given satellite will see at least 11 other satellites in the constellation (22.6% of the 50). Even if the antenna structure shown in FIG. 2 can only cover 60% of the satellite's sphere (due to design limitations such as the need to provide a site for mounting solar panels), it is likely possible to pair an antenna between a particular satellite and at least one of the other 11 potentially available satellites. (Section III below describes satellite and antenna configurations that facilitate antenna pairing between system nodes, including satellite-to-satellite radio links.) Furthermore, increasing the number of satellites in the constellation increases the probability that an antenna on one satellite can be paired with an antenna on another satellite.

[0089] Important attributes of the present system include, but are not limited to, the ability to scale up to more complex systems incorporating more satellites and other types of airborne nodes at different altitudes, the ability to accommodate a wide variety of deployment strategies, and the ability to compensate for orbital decay and satellite failure. Additional satellites can be deployed in higher orbits to increase their surface footprint and the distance at which they can see other satellites. Furthermore, the system continues to function as satellites decrease in altitude due to inevitable decay in their orbits due to drag caused by the atmosphere. Replacement satellites can be launched at low cost because they are inexpensive to manufacture and do not need to be placed in a specific location compared to satellites already in orbit. Thus, if satellites fail, they can be replaced inexpensively without affecting system operations, making satellites used in the system described in this disclosure essentially disposable, while the system remains operational even if a satellite is lost.

[0090] Satellite constellation S1 in orbital trajectories OT1 and OT2 x and S2 x Those skilled in the art will readily appreciate that the routing protocols and principles described below in connection with this embodiment (x=250) are applicable to systems having satellites at other altitudes and following other orbital trajectories. Figure 5 also illustrates a system having multiple satellites S3 in a third orbit OT3. x and a constellation with multiple satellites S4xin in a fourth orbit OT4. Satellite S3x in track OT3 has a footprint of approximately 10,000,000 square miles, represented by the long dashed circle FP3, and will see other satellites at distances up to approximately 3,500 miles (400 mile high orbit in Table 1). Satellite S4x in track OT4 has a footprint of approximately 21,000,000 square miles, represented by the dashed ellipse segment FP4, and will see other satellites at distances up to approximately 5,000 miles (800 mile high orbit in Table 1). In particular, satellite S4 xThe shaded area associated with the footprint of indicates that satellites launched from sufficiently northern locations at sufficient altitudes would enable transmissions to and from ground stations at very northern (and southern) terrestrial latitudes. It will become apparent from the following discussion that the routing protocols described herein support communications with constellations including satellites in these types of more highly inclined orbits, thus enabling reliable data transmission between virtually any two points throughout the occupied region of the Earth.

[0091] 2. Routing and Data Transmission Protocol

[0092] As mentioned earlier, the basic principles underlying the path generation protocol for a multi-satellite system will first be described in relation to a constellation of 50 satellites in 200-mile-altitude circular orbits OT1 and OT2. While this system could incorporate satellites orbiting at higher altitudes, lower-orbit satellites would offer an advantage in that they require less power to create radio links with ground stations. For example, a reduction in altitude from, say, 400 miles to 200 miles could provide as much as a 6 dB power advantage. Furthermore, while the orbits of low-altitude satellites would decay more quickly due to atmospheric drag, the satellites used in current systems can be small enough to burn up quickly as they enter the atmosphere farther.

[0093] Since, on average, three satellites will be visible from any ground station (see diagram above), there is a reasonable chance that a radio signal can be uploaded instantly from any ground station within the covered band during the tropics, with only satellite overhead, or at most a short delay. (As noted, the more satellites present in the constellation, the higher the probability that at least one satellite will be able to receive this transmission in real time.) Radio signals transmitting data are usually in the form of packets, with the contents in the payload section and destination information in the header or trailer section.

[0094] Routing Protocols for Data Transmission: The data transmission routing protocols described herein generally enable data transmissions that require less computing power and therefore reduce satellite battery consumption. Data transmissions are sent from satellite to satellite via wireless links between antennas within the satellites, using the basic satellite design shown in Figures 2 and 3. The wireless links are created by antenna pairing circuitry contained in the route creation module 46 within each satellite. Section III.C. below describes embodiments including novel satellite and antenna configurations for creating wireless links between system nodes useful in implementing the routing protocols described herein.

[0095] In this embodiment, the region of the Earth served by the system (in this example, the swath of the Earth between the Tropics of Capricorn) is divided into zones, the number of which is somewhat arbitrary. The zones should be large enough to maximize the probability that at least one satellite will be in every zone at any given time. That is, the size of the zones is selected based, at least in part, on the number of satellites in the system and the amount of Earth's surface they traverse. In this embodiment, the swath between the equator and each of the Tropics of Cancer and Capricorn is divided into 20 substantially rectangular zones. The circumference of the Earth at the equator is approximately 25,000 miles, and the distance from the equator to each tropic is approximately 1,600 miles. Thus, the area of ​​each zone is approximately 2,000,000 square miles (1,250 miles x 1,600 miles). Each of the resulting 40 zones is assigned a unique identifier, such as a sequential number, and all ground nodes are assigned unique address information. Additionally, each ground node in the system stores location information identifying the zone number in which it is located. In an alternative configuration, terrestrial nodes can store the latitudinal and longitudinal boundaries of the zones. The satellites refresh their geolocations at short intervals. In the embodiment described here, the routing protocol establishes two routing networks: a local area routing network and a wide area routing network.

[0096] In current routing protocols, all terrestrial nodes in the system create a local area routing network that defines routes to itself as the destination for data transmission. Referring to Figure 6, the creation of a local area routing network for a particular terrestrial node GN begins with the continuous transmission of an initiation routing message (RMI) into space at predetermined intervals, typically approximately once every four seconds. If the particular terrestrial node is a permanent terrestrial ground station equipped with an array of directional antennas, it will transmit high-power beams in all directions, i.e., across the entire hemispherical region surrounding the ground station. Such ground stations typically have virtually unlimited power, which increases the likelihood that the initiation routing message will be received by at least one satellite in the orbital constellation. When a satellite receives an initiation routing message (RMI) from the initiation terrestrial node GN, it begins creating the local area routing network by noting (i.e., storing) certain information contained in the initiation routing message. This includes terrestrial node address information, which includes a zone portion identifying the zone in which the terrestrial node is located and a unique address portion containing unique address information associated with each individual terrestrial node. The satellite receiving the initiation routing message also determines the quality Q of the initiation routing message, as further described in the following paragraphs. The satellite that receives the initiating routing message from the initiating ground station is referred to as the "primary satellite" for convenience. Each satellite's antenna has a unique identifier, and each primary satellite stores the identification information of the antenna that received the initiating routing message and the terrestrial node address information associated with the terrestrial node GN. The link between the primary satellite and the terrestrial node is indicated by a bold dashed line in Figure 6. The satellite's antenna pairing circuitry only accepts initiating routing messages (RMI) from terrestrial nodes within the zone in which the satellite is located. As mentioned above, the zone size is selected taking into account the number of satellites and the system's coverage area, increasing the likelihood that at least one satellite will serve every zone, thus enabling local area networks to be assembled for every zone.

[0097] Figure 6 illustrates local area route creation for five primary satellites 1A, 1B, 1C, 1D, and 1E. In the figure, the initiating routing message is referenced by the reference "RMIX," where "X" is the primary satellite that received the routing message. It will be understood that in an actual system, there may be many more satellites that receive the initiating routing message, as well as many satellites within the terrestrial node's zone that do not receive the initiating routing message. The quality Q of each initiating routing message, as determined by the receiving primary satellite, is given in parentheses with each routing message. Quality Q is a quantitative parameter that indicates the desirability of a wireless link between two nodes for supporting inter-modal data transmission, as explained further below. In the current system, Q is measured signal strength. Other implementations are possible, such as including error coding data in the routing message and then evaluating the extent to which the routing message contains erroneous data. However, measured signal strength is one preferred parameter because it avoids the need to include additional data in the routing message, which would increase the bandwidth, power, and time required for transmission.

[0098] In the next step in creating the local area routing network, all primary satellites transmit primary routing messages on all antennas. The primary routing messages include terrestrial node address information and the quality of the initiating routing message. Satellites that receive the primary routing messages are called secondary satellites. The drawing shows four secondary satellites, 2A, 2B, 2C, and 2E. Consistent with the terminology above, the primary routing messages are referenced by the reference "RM1X," where "X" is the secondary satellite that received the primary routing message. Routing messages received by the secondary satellites are indicated by dash-dotted lines. Each secondary satellite records the identity of the antenna that received the primary routing message. The secondary satellite also determines the quality Q of the received primary routing message.

[0099] Figure 6 illustrates the operation of the routing protocol when a satellite such as secondary satellite 2A receives two routing messages identifying the same ground node. x receives the primary routing message RM1A at antenna A y Suppose that satellite 2A receives primary routing message RM1B. RM1B has a higher quality (Q=8) than RM1A (Q=6), but the route to ground node GN through satellite 1B includes link RMIB with quality Q=1. Even though satellite 2A has a higher sum of the qualities of links RMIB (Q=8) and RM1B (Q=1), its other potential route to ground node GN includes link RM1B with the lowest quality (Q=1). Therefore, applying the principle that "a chain is only as strong as its weakest link," antenna A receives primary routing message RM1A (Q=6). x That is, satellite 2A discards (does not store) the antenna from which it received the routing message with the lowest quality (lowest signal strength) among the initiation and primary routing messages, and stores the identifiers of the antennas from which it received other primary routing messages. This sub-route is shown by the thick dashed-dotted line indicating the link established via the preferred primary routing message RM1A. Potential links that have been discarded are not shown by the thick dashed-dotted line. The secondary satellite discards the selected antenna A. x The satellite ID of the local area routing network (LAN) is stored, along with the quality Q (Q=2) of the minimum quality routing signal (RMIA) received on that satellite and the terrestrial node address information of the terrestrial node GN that has the route. In some cases, the primary routing message is not received by any satellite, e.g., satellite 1D in Figure 6. In that case, the local area routing network through that satellite has only a single link.

[0100] The secondary satellite then transmits a secondary routing message to all of its antennas. The secondary routing message includes the address information of the terrestrial node and the lower of the quality Q of the respective initiating and primary routing messages linking the primary and secondary satellites to the primary satellite and the terrestrial node. In FIG. 6, the secondary routing message is referenced by the reference "RM2X," where "X" identifies the satellite ("tertiary satellite") that received the secondary routing message. As a first example, two of the secondary routing messages transmitted by satellite 2A are received by two tertiary satellites, 3A and 3C, respectively. Satellite 3A receives the secondary routing message RM2A1, and satellite 3C receives the secondary routing message RM2A2. Because the only potential route from satellite 3A back to the terrestrial node is through satellites 2A and 1A, tertiary satellite 3A stores the antenna identifier that received the routing message RM2A1 and the terrestrial node address information of terrestrial node GN. Potential links established via secondary routing messages are represented by dash-dot lines with selected links in bold.

[0101] Satellite 3C receives three secondary routing messages: RM2A2, RM2B2 (satellite 3B received RM2B1), and RM2C (from tertiary satellite 2C). Routing message RM2A2 includes the quality (Q=2) of the initiating routing message RMIA, as described above. Routing message RM2B2 from satellite 2B includes the quality (Q=3) of the initiating order routing message RMIC from satellite 1C to satellite 2B because it is the lower of the quality Q of RM1C1 (Q=4) and RM1C (Q=3). Routing message RM2C from satellite 2C includes the quality (Q=3) of the initiating order routing message RMIC from satellite 1C to satellite 2B because it is the lower of the quality Q of RM1C2 (Q=5) and RM1C (Q=3). Satellite 3B determines the quality of each of the received secondary routing messages and the quality of the weaker link to the ground node via the secondary and primary satellites. Therefore, satellite 3C selects the sub-route through satellite 2C established by RM2C because the lowest quality of the link back to the primary satellite via that route is Q=3 (RMIC) compared to Q=2 for both routing messages RM2B2 and RMIA. Satellite 3C stores the antenna that received the secondary routing message RM2C and the terrestrial node address information of terrestrial node GN.

[0102] The principles underlying the selection of a preferred radio sub-route from a primary satellite back to a terrestrial node can be described in general terms through an understanding of the algorithm used by the satellite's route generation circuitry to select a preferred tertiary routing message based on the sub-route. The route generation circuitry of each tertiary satellite performs two determinations: first, it determines the quality of each secondary routing message received from each secondary satellite and matches it to the underlying link quality contained in the associated secondary routing message, RMIA (Q=2); RM2A2 (Q=7), RM2B2 (Q=2) matched with RMIC (Q=3), and RM2C (Q=5) matched with RMIC (Q=3). The two identify a preferred secondary routing message representing a secondary sub-route from the tertiary satellite to a terrestrial node via the primary satellite. This secondary sub-route includes a third wireless link between the tertiary satellite and the secondary satellite associated with the preferred secondary routing message. In this example, the preferred tertiary routing message is RM2C because all of its links have higher quality than the first, second, or third wireless links associated with the other received secondary routing messages. That is, all of the links in the sub-route through RM2C, RM1C2, and RMIC have higher quality than the lowest quality link of any other possible sub-route (Q=3 for RMIC, Q=2 for RMIA and RM2BOB). The satellite's memory stores the antenna identifier from which the preferred tertiary routing message was received and address information associated with the terrestrial node.

[0103] Those skilled in the art will appreciate that the local area routing network shown in FIG. 6 is somewhat idealized in that it depicts a network that extends geographically from a terrestrial node. While this facilitates the explanation of how a local area network associated with a terrestrial node is created, the stochastic distribution of satellites and the long distances separating them may result in higher-order satellites being closer to the terrestrial node than the lower-order satellites to which they are linked. However, it will be apparent from the following description that a local area routing network with that type of topology is still useful for directing data transmissions to the initiating terrestrial node. Similarly, it is possible for a given order of routing messages to be received by a satellite already identified as part of a route back to the terrestrial node. In that case, the receiving satellite already has the unique address of the originating terrestrial node memorized and ignores the routing message. That is, routing messages of different orders are transmitted consecutively in their respective time slots, established via the satellite's Global Navigation Satellite System (GNSS) module 44's access to the master clock of the cooperating GNSS system clock. Thus, if a given satellite has already received a routing message as described above, it will ignore subsequent routing messages.

[0104] The local area routing network is not limited to three tiers of satellites. It can be extended to four or more tiers constructed in the same manner as described above. However, as will become clear as this description progresses, a three-tier system is believed to serve the purpose of directing data transmissions to ground nodes without requiring excessive time, computational power, or bandwidth, and any sub-routes with links below a certain threshold of Q are not stored. For example, if the threshold Q is 3, then information (antenna identifiers and values ​​of Q) about the sub-routes from satellites 1A, 2A, and 3A and the sub-route from 1B shown in FIG. 6 is not stored, and the sub-routes are not established.

[0105] In the preferred routing protocol, a wide-area routing network is autonomously created by the satellite and takes into account data transmissions uploaded to the satellite from originating terrestrial nodes and addressed to terrestrial nodes not served by the local area network containing that satellite. The wide-area routing network is constructed using the same principles described above to create the local area routing network by using a series of routing messages, dropping potential links of low quality, and storing the antenna identifiers on each satellite that received the routing message, which are used to identify preferred links with other satellites. The primary difference from local area routing networks is that wide-area routing networks are zone-based, and their purpose is to establish optimized routes toward the zone to which the uploaded data transmission is destined. Furthermore, they are initiated by the satellite, not the ground station.

[0106] Every satellite in every zone creates a wide-area routing network for itself. This process begins when an initiating wide-area satellite transmits an initiating wide-area satellite routing message to all of its antennas, indicating its geolocation using the same format as the zone portion of the ground node's address information. Satellites that receive the first wide-area satellite routing message transmit a second wide-area satellite routing message that includes the initiating wide-area satellite's zone and the signal strength of the received first wide-area satellite routing message. Creation of a wide-area network route proceeds in the same manner as described in connection with FIG. 6 for a predetermined number of hierarchies, preferably at least three hierarchies, although more hierarchies can be established in a given system. Every satellite in a wide-area network includes the initiating wide-area satellite's zone and the antenna it uses to transmit data transmissions to the next satellite in the network destined for that zone. For example, when a satellite that is part of a local area network initiates the process of creating a wide-area network, there is a certain amount of overlap in the transmissions and calculations used in creating the local area routing network.

[0107] Data transmission using local and wide area routing networks

[0108] This description will be used as an example of a data transmission from an originating terrestrial node that includes a packet of data with a header that includes address information associated with a destination terrestrial node. One component of the address information is location information, such as a zone number, of the destination terrestrial node. The address information also includes unique address information associated with that particular destination terrestrial node.

[0109] A typical data transmission process is described with reference to the flowchart in FIG. 7, which shows how any satellite in the system processes a packet of data on the satellite and has address information (zone and unique terrestrial node address) for transmission to a destination terrestrial node. The destination terrestrial node for data transmission corresponds to the initiating terrestrial node in the local area routing network route creation description above. It will be understood that a satellite typically carries many packets addressed to an infinite number of destinations. FIG. 7 shows how the data transmission circuitry in the satellite's data movement module processes individual packets of data. Packets can be processed in any order, but in one implementation, packets are time-stamped as they are received and processed in chronological order.

[0110] In step S102, the data transmission circuitry in the satellite holding the packet determines whether one of its antennas is paired with the antenna of the destination earth station whose unique address is included in the packet. In other words, if the packet being processed by the satellite contains a unique address portion that matches a unique address portion stored by the satellite, it means that the satellite is within the local area network associated with the destination earth node, and the answer in step S102 is yes. As discussed above in connection with Figure 6, all satellites in the hierarchy of the local area network leading to a particular destination earth node have in memory the antenna pair that will transmit data to the destination earth node. In step S104, the packet is transmitted accordingly.

[0111] The second part of step S102 determines whether the data transmission circuitry in the satellite is linked to a satellite in the local area routing network that leads to the destination terrestrial node addressed by the packet. As part of the routing protocol, after the local area network and wide area network are refreshed, all satellites in all local area networks transmit an announce routing message from all their antennas at short intervals (typically every 1 to 4 seconds). The announce routing message contains the address information of the terrestrial node stored by the transmitting local area network satellite. A satellite receiving an announce routing message first determines whether it has the same unique address portion contained in the announce routing message in its memory. If so, this means that the receiving satellite is already within the local area network associated with the destination terrestrial node, and it ignores the announce routing message. If the receiving satellite does not already store the unique address portion associated with the destination terrestrial node, it stores the antenna that received the announce routing message and the address information of the unique terrestrial node. The receiving satellite also determines the quality Q (e.g., signal strength) of the received announce routing message. If the satellite receives the announce routing message on more than one antenna, the satellite stores the identifier of the antenna that received the announce routing message with the highest quality. If the satellite is thus connected to a local area network satellite associated with the destination terrestrial node via the announce routing message, the answer to the second part of step S102 is YES, and the packet is transmitted accordingly in step S104. (In an alternative approach, the announce routing message could include quality information stored by the satellite transmitting the announce routing message, allowing the receiving satellite to select a route to the terrestrial node according to the principles used to assemble local area networks and wide area networks.)

[0112] If the answer to step S102 is NO, the process proceeds to step S106, where it is determined whether the satellite holding the packet has memory zone information that matches the zone information of the packet being processed. That is, if the satellite processing the packet is part of a wide area network that includes a satellite in the zone of the destination earth station, the answer to step S106 is YES. This indicates that the satellite holding the packet for transmission has identified an antenna paired with the satellite that has a route to the zone containing the destination earth station, and in step S108, the packet is transmitted on the antenna identified as part of creating the wide area routing network. In other words, step S108 forwards the packet to the next satellite in the wide area network that leads to the zone in which the destination terrestrial node is located. It should be understood that the second part of step S102 is optional in that it serves to increase the probability that one of the satellites in the wide area routing network associated with the destination zone will "find" a satellite in the local area network associated with the destination terrestrial node in that zone. However, the data transmission process may also depend on the possibility that a satellite in the wide area network associated with a particular zone is also part of the local area network of the destination terrestrial node in that zone, especially considering that the network refreshes periodically and almost certainly includes a different satellite with each refresh cycle.

[0113] If the answer in step S106 is NO, the satellite holding the packet uses a vector routing approach to send the packet in the direction of the terrestrial node's zone, per the terrestrial node's address information in the packet header (or trailer). In step S110, the satellite waits for an acknowledgment signal from another satellite that received the packet (the receiving satellite returns an acknowledgment signal using the antenna that received the packet). If an acknowledgment signal is not received within a time substantially shorter than the network refresh interval (1-4 seconds), the answer in step S114 is NO, and the packet is returned to the queue for reprocessing beginning with step S102. In a preferred embodiment, the packet can be held in a database that is accessed in a predetermined pattern. If an acknowledgment signal is not received in step S110, the packet remains in the database for subsequent access according to the predetermined pattern.

[0114] The recursive hierarchical logic governing the data transmission protocol allows all satellites to perform essentially the same programming steps, greatly simplifying data transmission throughout the system. It also accounts for the system's probabilistic support by examining each data packet to determine how to route it to its destination according to the hierarchy shown in the flowchart of Figure 7. By retaining the packet for a short period of time during which the receiving satellite may not be en route to its destination, any satellite holding a data packet is expected to be able to forward it to its destination virtually instantaneously, while accounting for the probabilistic nature of the system's reliability for a probabilistically distributed satellite constellation. Although numerous local-area and wide-area routing networks exist, each satellite in the system only needs to know the local-area route to the destination terrestrial node and, if it does not have a local-area route to the destination, the wide-area route to a zone of distant destination terrestrial nodes. This minimizes the computational load on individual satellites while simultaneously reducing power consumption. Alternative routing approaches and methods described below further facilitate route creation and data transmission.

[0115] Figure 8 will be used to explain some examples of data transmission, making use of the diagram in Figure 6 and the flow chart in Figure 7. In the first case, a user in Uyo wants to send a message to a user in N'Djamena, Chad. 10 If satellite S16 receives a data transmission from the Uyo user's terrestrial node and is the primary satellite (FIG. 6) with respect to the N'Djamena user's terrestrial node (step S102), satellite S2 transmits the packet-by-packet message directly to the N'Djamena terrestrial node using the antenna identified during route generation, as described above (step S104). Note that if satellite S16 receives an initiation routing message from the N'Djamena terrestrial node, satellite S16 is not the primary local area network satellite associated with N'Djamena because it is not in the same zone. However, even though N'Djamena and satellite S16 are in different zones, satellite S16 is associated with the N'Djamena ground station and satellite S2 10 In this case, if satellite S16 carries a packet from Uyo with a unique address portion associated with the N'Djamena ground node, it will be considered as a secondary satellite in the local area network (Figure 6). 10 (Step S104). In all cases, packets in a data transmission are processed separately and reassembled in the proper order when all packets arrive at their destination. Because routes are periodically refreshed, packets of a particular data transmission may be sent over different routes. In accordance with known practice, packets include appropriate ordering information and error codes to enable packets of a single data transmission to be properly reassembled when they arrive at their destination.

[0116] In a second example, a user in Uyo wishes to send an email or other communication to a server at a particular ground station in Mumbai, India. The communication, as noted, is in the form of packets, each packet containing address information for the ground node, including a zone portion identifying the zone of the destination ground node, and a unique address portion containing unique address information associated with the destination ground node. The data transmission is transmitted via satellite S2.10 Assume that the data is uploaded only to satellite S2, and that satellite is not part of the local area network associated with the destination Mumbai ground station. In that case, 10 first determines whether it has on-board connectivity to a satellite in its local area network that leads to the Mumbai terrestrial node, as indicated by a possible announce routing message received from a satellite in that local area network, i.e., satellite S2 10 compares the terrestrial node address information in the data transmission packet with the terrestrial node address information stored in the satellite (step S102). If the answer is YES, satellite S2 10 transmits a packet on the antenna associated with the received announce routing message (step S104).

[0117] If the satellite does not have a memory containing unique address information associated with the packet's unique ground node address, the satellite S2 10 determines whether the memory has ground node address information with the same zone portion as the zone address information in the onboard packet (zone Z5). That is, whether the destination zone of the packet is the same as that of satellite S2. 10 7. The next step is to determine whether the packet is within the wide area routing network associated with zone Z5 in Mumbai (step S106), noting that this is the same zone to which the wide area network containing zone Z5 is connected. If so, the next step is to transmit the packet via the antenna identified in creating that wide area routing network (step S108). Note that all satellites receiving a packet from a ground node or another satellite process the packet according to the flowchart of FIG. 7. The probabilistic nature of the system, combined with the fact that every ground station has a wide area local area network associated with it, makes it nearly certain that a satellite within the wide area network to a particular zone will be able to connect to the local area network associated with a particular ground station in that zone.

[0118] As another example, consider a data transmission from Uyo destined for a ground station in Leyte. The data transmission is from satellite S2 10 Assume that the satellite is not associated with any local area or wide area network associated with the Leyte ground station. In that case, satellite S2 10 transmits data packets on its antenna pointing generally towards zone Z7 where the Leyte ground station is located. In a preferred embodiment, the antenna beamwidth is ±30° around the vector pointing towards the Leyte zone. 10 waits for an acknowledgment from the satellite that it received the packet. If an acknowledgment is not received, the packet being processed is returned to the queue to be reprocessed from step S102, as indicated by the "no" arrow in Figure 7. Again, the stochastic nature of the system acts to reduce or eliminate the time the satellite must hold the packet, thus minimizing delays in delivering the packet containing the data transmission to its destination.

[0119] In one variation of the system described above, zone boundaries can be adjusted to facilitate data transmission to areas of large population density, such as urban areas. For example, if zone boundaries would otherwise divide a metropolitan area, such as New York or Mumbai, into two or more zones, the boundaries can be adjusted so that a single zone encompasses as many ground nodes in that area as feasible. This has the potential to require fewer of the steps shown in FIG. 7 for packets destined for such areas by increasing the number of ground stations in these types of dense areas served by a single local area routing network.

[0120] The stochastic nature of the system also causes minimal delays in uploading data transmissions to the satellite constellation. Therefore, the ground node of the preferred embodiment transmits data packets sequentially. In one embodiment, the ground node may retain packets that have not been acknowledged by the satellites by returning an acknowledgment signal and retransmit them according to a predetermined timing scheme. The low 200 mile altitude of the satellites in this system also increases the probability of successfully uploading data packets to the satellite constellation. Furthermore, the scalability of the system allows for the deployment of additional satellites as part of the system if latency is deemed unacceptable for a given system. That is, because satellites are inexpensive to manufacture and launch, a system operator can deploy 50 or 100 or more additional satellites for minimal overhead.

[0121] As a final step in the data transmission, a destination terrestrial node that successfully receives all of the packets of a particular data transmission uploaded to the originating satellite can optionally send an acknowledgment transmission to the originating terrestrial station. Such an acknowledgment would typically be automatically sent in the same format as the original data transmission, i.e., as one or more packets with a header or trailer containing address information back to the originating terrestrial station and a content portion with the acknowledgment. The acknowledgment message would be sent back to the originating terrestrial node using the same routing protocol as the original transmission described above.

[0122] The above-described routing protocol significantly reduces the amount of data that must be transferred between satellites for long-distance transmission in space-based systems requiring inter-satellite communications. This is done by distributing the routing computations among the satellites, rather than requiring every satellite to know every route to every ground node in the system. This novel approach reduces the time and battery power required for data transfer by orders of magnitude and is one of the features of a space-based system that uses satellites that do not need to be maintained in fixed geographic locations and precise attitudes to support worldwide data transmission. Additionally, the scalable nature of the system allows for incremental improvements in system performance at minimal cost.

[0123] Additional optional fixes

[0124] The routing protocol and data transmission method described above can be implemented in a variety of ways. One is by a group of individual users, each with their own ground station. In another application, a system could be configured to receive messages addressed to a group of subscribers served by a single cellular telephone tower, such as in a small island or other isolated location situation, in which case the system would have a ground node that directs messages to the cellular tower. The address information for the ground node in this type of system would include the telephone number of the intended subscriber so that the cellular system can direct them accordingly. This same type of system could be incorporated into a more traditional cellular system with multiple towers serving a large area. In that case, one or more ground nodes could service the entire system, thereby introducing a data transmission into the cellular system where it is treated like any other transmission. Another variation could include one or more ground stations comprising a hub, such as a WiFi router, accessible to multiple users.

[0125] The above routing example requires the user to know the complete address information of the destination ground station. In an alternative embodiment, when a user associated with a particular ground node wishes to send an email to a user associated with another ground station, they can enter the address information on their electronic device in the familiar email format "recipient@internetserviceprovider.xxx." When the user sends an email from her device, the device will know the address information of the ISP server, and if necessary, the user's ground station can add the zone in which the ISP server is located to the email. Using the current system, the transmission is directed to the ISP server, and the ISP will send the email via conventional means to the email address.

[0126] One enhancement to the above routing protocol can utilize the ability to group data packets en route to a particular destination with other on-board data packets destined for the same zone. For example, assume a satellite is carrying data packets en route to a particular zone. In practical applications, many data packets in different transmissions being handled by a single satellite may be destined for the same zone. To make data transmission more efficient, the satellite can sort the packets it carries by their destination zone and then transmit them using the method described above in connection with FIG. 7. Those skilled in the art will appreciate that this sorting process can be implemented in many ways, such as using a relational database. This enhancement, in which packets in different data transmissions destined for the same zone are grouped for transmission, further reduces the computational capacity and power consumption required to implement data transmission in the present system.

[0127] In another alternative embodiment, the constellation can include multiple satellites at other, higher altitudes to reduce the number of inter-satellite hops in the final path. Figure 9 illustrates the principles involved in requiring satellites at higher altitudes to reduce the number of inter-satellite hops in the final path. It will be recalled that the constellation of this embodiment can have satellites in orbits at different altitudes. Figure 9 illustrates a system including satellite S200 in a 200-mile orbit and satellite S800 in an 800-mile orbit. Because the radio link length between two satellites in a 200-mile orbit is typically 2,500 miles or less, a radio path between London and a location 7,000 miles away would require at least five links, L2001, L2002, L2003, L2004, and L2005, between the London ground station and the Leyte ground station. See Table 1. On the other hand, because a satellite in an 800-mile orbit can see ground stations approximately 2,500 miles away and other satellites approximately 5,000 miles away (see footprint FP4 in Figure 5), a radio path could theoretically be established with only two satellites from London via links L8001, L8002, and L8003 to Leyte via satellites S8001 and S8002. Thus, satellite S8001 could receive a data transmission uploaded from London and be in a local-area routing network to ground stations over 7,000 miles away, including Chicago (4,000 miles) and Los Angeles (5,400 miles) (see Figure 6). However, at the very least, incorporating high-altitude satellites into the constellation increases the probability that the destination ground station is in a zone served by a wide-area routing network with a satellite receiving the data transmission from the originating ground station, thus eliminating step S108 (Figure 7) from the data transmission process in many cases.

[0128] In one embodiment, the routing protocol described above can be relied upon to automatically create links involving satellites at different altitudes. However, in another embodiment, inter-satellite routing messages contain all of the information described in connection with FIG. 6 used to create local and wide-area networks, along with the quality of all links back to the initiating ground station (for local-area routing networks) or initiating satellite (for wide-area routing networks). The routing message also contains a counter indicating the number of satellites in the network; this counter is incremented by each satellite that receives a routing message from that satellite, thus keeping track of the number of inter-satellite hops back to the starting point. Furthermore, a satellite receiving multiple routing messages does not discard the routing message with the weakest quality; rather, it discards only those routing messages below a certain quality threshold. The inter-satellite route back to the initiating ground station or initiating satellite then selects the route with the fewest inter-satellite hops. This favors the selection of higher-altitude satellites, since they typically require fewer hops to the destination. Routes involving higher-altitude satellites are also less likely to be discarded, since the quality of the wireless links incorporating them is typically lower than links between lower-altitude satellites that are closer together.

[0129] D. Distributed Ledger Systems

[0130] A satellite infrastructure having multiple satellites in a probabilistic constellation using routing and transmission protocols such as those described above can also be applied to distributed ledger systems. That is, features of the route creation and data transmission methods described above can be used to provide terrestrial users with access to a space-based distributed ledger system and to transmit ledger-related data between satellites. These systems and methods enable rapid reception, receipt, and distribution of ledger-related messages between users and satellites, and thus can serve to create a standard blockchain system for storing and verifying distributed information across a blockchain. Furthermore, the principles for creating a blockchain system described herein can also be used for data transmission.

[0131] 1. Blockchain principles applied to wireless routing

[0132] The satellite communications system described herein is particularly adapted for applying the principles underlying distributed ledger technology. A blockchain is a distributed ledger that is verified and copied across multiple computers, typically numbering hundreds or thousands. As applied to the systems and methods described herein, each satellite can be considered a node in the blockchain used to record and distribute information. In certain applications, terrestrial nodes can also be included as nodes in the blockchain.

[0133] Blockchain principles can be applied to the system in a variety of ways. For example, each time a data transmission is uploaded to an initial satellite node, the data transmission can be recorded as a transaction that is distributed to all nodes in the system, as described in more detail below. As noted above, other transactions can also be recorded at each node, such as an acknowledgment signal returned to the destination terrestrial node after the data transmission is complete.

[0134] These recorded transactions can be used for a variety of purposes: for example, the number of times a particular user accesses the system and the number of data transmissions completed can be used by the system owner for billing purposes or to compile statistics regarding usage or successful transmissions.

[0135] 2. Distributed Ledgers in Probabilistic Systems

[0136] By way of background, the Internet uses many different technologies that utilize distributed ledgers to track, record, and verify various transactions. As various prior art satellite systems expand their capabilities, satellites can be used to transport various data transmissions that are part of a particular application of a blockchain or blockchain-related ledger. An additional step would be to include blockchain and distributed ledger logic within the satellites. Such satellites could function similarly to more traditional terrestrial computers, storing, maintaining, and transporting various blockchain transactions. Because each blockchain and distributed ledger is unique, each would preferably have its own constellation of satellites or include a way to partition the operating modules within the satellites within a single constellation.

[0137] However, even if a given distributed ledger system includes satellites, the terrestrial internet that would still exist has several weaknesses. One weakness that stands out in the internet-blockchain system is privacy issues. Today's internet consists of numerous connections between hubs. Each hub of the internet provides forwarding and routing functions.

[0138] Router manufacturers indicate that they can store some of the traffic they route, essentially making it publicly accessible to the distributed ledger systems that use such routers. For example, even if router manufacturers cannot read the contents of blockchain transmissions, the unique formatting systems used with different blockchain applications can help identify the specific blockchain application being implemented. With this knowledge, a fairly simple computer program can create lists of blockchain originators, blockchain authenticators, and, in some instances, senders of confidential financial information, information about virus protection systems that may be useful to unauthorized users ("hackers"), and many other types of cloud-based information that senders wish to maintain authenticity.

[0139] Recently, hacking has already proven to be a problem that can undermine internet confidentiality. For example, it has been reported that several well-known apps intended for different functions have actually read users' emails without their knowledge. Such apps installed on a user's device, with or without the user's knowledge, can easily read the keystrokes the user was typing into the securitization system and transmit secret communications that were later added to the blockchain. Hackers can also access satellite or ground station routers, retrieve and modify information, and reintroduce false information into the network. The possibility exists that a sophisticated hacker can access communications at different points along its path and read, modify, or even delete specific blocks of information.

[0140] Similarly, in addition to electronic security issues, there are physical security issues. Many countries rely on undersea cables to provide connectivity to internet servers in other countries. These cables are easy to find and cut. The destruction of a few key cables could impair the operation of current major blockchain applications. Furthermore, terrestrial cables that cross international borders form a critical part of the complex global infrastructure that supports the internet. Some strategically located countries could cut the cables and face serious challenges to their internet.

[0141] The systems and methods described herein support a novel approach in which satellites are responsible for blockchain processing. Previously, satellite-based blockchain systems would have been infeasible due to the cost of manufacturing satellites, maintaining them in predetermined orbits, and enabling instant communication between them. The above-described system uses inexpensive satellites probabilistically distributed in low Earth orbit that can be responsible for all or nearly all of the storage and transmission of both transactions and blockchain authentication issues. One important aspect is that such a system can be completely privately owned and operated, supporting an additional level of privacy and electronic security. Furthermore, a satellite system incorporating the principles described herein increases the physical security of the system, inexpensively replacing any satellites that are destroyed by collision with other objects in space, disintegrate through orbital decay, or otherwise disintegrate. Furthermore, by its nature, the system continues to operate with little or no loss of system capability even if a satellite is lost.

[0142] The present blockchain approach seeks to enable a large or large group of low-cost satellites, such as those described in this disclosure, to be responsible for transaction transfers. To this end, the approach creates a space-based network that can track blockchain transactions and verify them as authorized under the blockchain's rules. Generally speaking, this requires all satellites to maintain records that agree on a common set of proven facts. The satellites must also approve and record all new transactions. Essentially, each satellite is part of a satellite routing mechanism. Furthermore, each satellite is also a member of a team of satellites that records and authenticates each transaction. Furthermore, satellites must be adaptable to the various potential types of blockchains that are presented to them. This goal creates the need for a new type of satellite communications paradigm that can be utilized to provide various types of services, such as cloud storage, transaction routing, and email delivery.

[0143] While the distributed ledger concepts presented herein can operate using satellites at various altitudes, the example used to demonstrate the operation of one such system is described using satellites in a 100-mile altitude circular orbit. This implementation may have many advantages over systems employing higher altitude satellites. Those skilled in the art will appreciate that the use of lower satellites represents a trade-off in that higher satellites see further above the horizon, thus facilitating inter-satellite links. However, a system with satellites in a 100-mile altitude orbit may be more advantageous in distributed ledger applications. Compared to satellites at a 200-mile altitude, the lower altitude may increase the received signal strength between ground users and the satellite by more than 6 dB. This provides more predictable results in ensuring the rapid distribution of transaction information between satellites and ground users. Furthermore, as discussed above, 100-mile altitude satellites can be used in combination with higher altitude satellites to improve the feasibility of creating the inter-satellite links necessary to distribute interaction information throughout the system. Although the present exemplary embodiment contemplates a network of approximately 200 satellites, 400 satellites would provide a greater degree of redundancy in that there would be more potential inter-satellite wireless links if the system relied on the probability of making such links between probabilistically distributed satellites. The system could also function with fewer than 200 satellites, perhaps as few as 20, but this could result in undesirable delays in the exchange of information between satellites.

[0144] The satellites described above in connection with Figures 2 and 3 are used in the distributed ledger application of the present invention. The satellite's CPU 40 includes a blockchain management module (not shown) that performs blockchain functions such as message forwarding and storing previous blockchain activity. A key issue, addressed in detail in the previous discussion of routing data transmissions through a satellite communications system, is establishing wireless communication between satellites. Thus, if the system is to provide blockchain communication, transaction approval, and blockchain validation, the system must provide information from a single satellite nearly instantaneously to all or nearly all of the other satellites in the system.

[0145] A system designed to utilize the portion of the Earth's surface between 60 degrees north and 60 degrees south latitude would provide access to almost the entire world population, as can be seen from Figure 5. The area of ​​this serviced portion of the Earth is approximately 175,000,000 square miles. A satellite in a 100-mile-high orbit has a footprint of approximately 2,500,000 square miles, which represents approximately 1.4% of the service area traversed by the satellite. Thus, on average, any given point within the system's service area will see approximately 3 out of 200 satellites. At the same time, there is a 98.6% probability that a satellite will not be visible from any particular point in this service area. There is only a 0.986 ± 0.059 (i.e., 1 in 17) chance that any point on Earth will not be able to see at least one satellite. As already mentioned, a system with probabilistically distributed satellites is fully scalable by adding satellites to the constellation. For example, if the constellation had 300 satellites (0.986 300 ≈0.0145), the chances that any given point on Earth will not be able to see at least one satellite drops to 1 in 70.

[0146] As with the data transmission systems discussed above, the number of other satellites that any given satellite can "see" is also an important factor in a distributed ledger system; in this embodiment, each satellite can theoretically "see" other satellites approximately 1,800 miles above the horizon (2 × D from Table 1). For the purposes of this discussion, ignoring that interference from ground structures in a given satellite's horizon EH may reduce that distance, the area covered by a circle with a radius of 1,800 miles is approximately 10,000,000 square miles, which is 5.7% of the 175,000,000 square mile area intersected by the 200 satellites in the device, meaning that any given satellite can see at least 11 other satellites in the constellation (5.7% of 200). Even if the antenna structure shown in FIG. 2 can only cover 60% of the satellite's sphere (due to architectural limitations such as the need to provide a site for mounting solar panels), it is likely possible to pair an antenna between a particular satellite and at least one of the other 11 potentially available satellites. Furthermore, increasing the number of satellites in the constellation will correspondingly increase the probability of successfully pairing an antenna in one satellite with an antenna in another satellite.

[0147] The following describes a potential method for disseminating communications from a ground user at an initiating satellite across the globe. Assume a cycle time of 1 / 10 of a second. Each of the 200 satellites is given a precise time to transmit within that 1 / 10 of a second. For example, the first satellite can transmit data at 0.1005 seconds. The second satellite can transmit data at 0.1010 seconds. Thus, a time slot exists for each satellite. Conservatively, assume that each satellite can establish radio links supporting data communications with at least four of the 11 satellites within its range. At the end of the first cycle, the first satellite will have transmitted its data to approximately four other satellites. In the next 0.1-second cycle, those four satellites will attempt to transmit the same data to the other eight of the 11 satellites. By the end of the third 0.1005-second cycle, the chance of excluding a single satellite in the first group becomes small. The satellites described above in connection with Figures 2 and 3 are particularly suited to establishing these inter-satellite connections, with the route generation module 46 and data transfer module 48 configured to support the distribution of communications among the global satellites. At the same time, communications are spread across the globe in all directions. Because the satellites can see 1,800 miles above the horizon, theoretically, it takes only six to eight cycles to transmit a communication to the other side of the Earth, 12,500 miles away. However, given the probability distribution of satellites, a more realistic estimate is within approximately one second (10 cycles at 0.10 cycles per second), meaning that nearly every satellite received the original transmission. The satellites' GNSS modules communicate with the Global Navigation Satellite System, providing a common clock for all satellites.

[0148] This type of system can be used for a variety of different blockchains. Some systems rely on the use of standardized smartphones, while others allow for the possibility of designing specific secure devices to operate only on specific satellite systems. Also, in some applications, it is advantageous if the operating code and blockchain algorithms are stored in permanent, unrewritable memory within the satellite, making it virtually impossible for hackers to modify the code. Furthermore, all messages and all blockchains are preferably securitized using appropriate hashing and securitization algorithms. To communicate with users on the ground, each satellite stores the geographic location of all users and uses a GNSS module to determine when it is within line of sight of a user and communicates onboard information to designated users.

[0149] Advantages of such systems include the use of small, stochastically distributed satellites, which allows the system to continue service even if some are destroyed. This contrasts with systems using larger satellites that must be maintained in a predetermined orbit by heavy rocket thrusters, which requires the satellites to carry heavy rocket fuel. Because link creation in such systems relies on satellites in precisely controlled positions, the loss of just a few satellites in a controlled orbit can bring the entire system down. However, if some of the satellites in the systems described herein go out of service, data communications with the entire satellite constellation and ground nodes are still supported, and satellites that are out of service for any reason can be easily and inexpensively replaced if desired.

[0150] Furthermore, the system has a high degree of electronic security. In addition to using unalterable computer code, another advantage is that each pair of antennas generally transmits a relatively narrow beam back and forth between them. Even if another satellite that is not part of the system is in nearby orbit, it cannot be part of the system satellite's beam-matching logic, and therefore it has proven difficult, if not impossible, to monitor more than a few signal exchanges between system satellites. Near-perfect secrecy may further be achieved by using a hashing algorithm suitable for inter-satellite communications.

[0151] Figure 10 illustrates the free-form nature of the process for creating routes between satellites in a space-based distributed ledger system such as that described in this section, and in a data transmission system that uses the routing protocol described in Section II.C. in connection with data transmission. Figure 10 illustrates how the system described herein can indirectly link two ground stations GN1 and GN2 that are theoretically close enough to be within the line of sight of a single satellite. In Figure 10, ground stations GN1 and GN2 are only approximately 200 miles apart. As shown in the figure, in a distributed ledger system, the number of 200 satellites in a 100-mile-high orbit is represented by the notation LX, where "X" is the number of satellites, and at an orbital altitude of 100 miles, a satellite can "see" ground stations at least 800 miles away and other satellites approximately 1,600 miles away. These are conservative estimates based on the distances in Table 1 and take into account the possibility of interference from topographical features or tall structures on the ground. In theory, either satellite L89 or L162 could form links with both ground stations, since they are both within about 400 miles of the farthest satellite (GN1-L162).

[0152] However, the routing techniques employed by the system described herein can connect two nearby ground stations by linking multiple satellites, some of which may be beyond the range of either of the ground stations and provide a stronger sub-route between the ground stations than satellites within range of both. For example, satellite L192 is approximately 1,000 miles from the closer ground station GN2, but using the methods described herein, it can form part of the route between the ground stations. From FIG. 10, it will be further understood that the local area network shown in FIG. 6 is an idealized representation, and higher-order satellites are not necessarily farther from their starting ground node than lower-order satellites within the same local area network. For example, satellite L64 may be a primary satellite associated with ground node GN2, 350 miles away, while satellite L89 may be a secondary satellite within the same local area network, despite being closer (250 miles) to ground node GN2.

[0153] III. Replacement Satellite Construction and Deployment Strategies

[0154] As mentioned above, the above space-based data transmission technologies and distributed ledger systems can be realized using the basic satellite architecture shown in Figures 2 and 3. However, this section describes several strategies to increase the probability of creating inter-satellite radio links and make them more robust and long-lived so that more information can be communicated between satellites in a shorter time. These strategies include configurational variations on the satellite architecture in Figures 2 and 3, satellite attitude control, rotating satellites, enhanced antenna designs, and CubeSat compatibility, to name a few.

[0155] A. Orbiting satellite

[0156] Designing a satellite-based wireless mesh system according to the above description involves numerous tradeoffs between a wide variety of parameters. Two specific parameters that serve opposing purposes and therefore require judicious selection are the beamwidth of the radio signals transmitted by the antennas and the antenna's power (gain). On the other hand, a larger beamwidth increases the probability that beam alignment can be achieved, but a larger beamwidth reduces the antenna's gain. Conversely, a narrower beam increases antenna gain but reduces the probability of beam alignment between nodes. This tradeoff is particularly important for satellite nodes because the satellite antenna configuration must take into account the satellite's weight and size, which limit the number of antennas it can carry, as well as constraints on the power available from onboard batteries. Also, some radio beams may be weakened by grazing on the Earth's surface, which can partially chain the signal before reaching the receiving node, making it desirable to increase the number of possible beam alignments between nodes.

[0157] Achieving an appropriate tradeoff between beamwidth and antenna gain is critical to the efficient functioning of satellite-based systems with stochastically distributed satellites, which depend on the statistical probability of creating a route using a satellite-to-satellite radio link. Typically, satellite antennas point into space toward each other and toward the Earth to enable the establishment of links between nodes. A fundamental property of this system is its dependence on transmissions of sufficient strength to reach other nodes (ground stations and satellites). The system relies on having enough satellites in orbit and making appropriate design tradeoffs, including beamwidth versus gain, to increase the probability of being able to establish proper communications between system nodes, both satellites and ground stations.

[0158] This embodiment utilizes satellites that rotate about an axis, which increases the likelihood that communications over a high quality link can be created, as described herein. With orbiting satellites, beamwidths can be reduced with a corresponding increase in gain.

[0159] The principles involved may be explained using as an example a satellite configuration such as that shown in Figure 2, with 25 antennas covering approximately 60% of the spherical satellite's surface. A rough estimate of the probability that a radio beam transmitted by such a satellite will be received by another similar satellite is therefore approximately 36% (0.6 x 0.6). Those skilled in the art will appreciate that this is only an estimate, since radio beams have side lobes that increase, to some extent, the probability that a link will be established. Doubling the satellite diameter also doubles the diameter d of the parabolic dish antenna. The formula α = (k x γ) / d halves the half-maximum beamwidth (HPBW). While the beam area is only one-quarter the size, the antenna gain increases by four times, or approximately 6 dB. Meanwhile, the probability of a beam match between satellites is approximately 2% (36% x (1 / 4)). 2 ) is reduced to

[0160] In this embodiment, the use of satellites that spin about an axis of rotation enhances the establishment of wireless links by antenna pairing via beam alignment between the satellites. In one embodiment, the satellites themselves have the same components as the satellites depicted in Figures 2 and 3 and described in the associated text above.

[0161] To illustrate the operation of a typical system using rotating satellites, the satellites are assumed to deploy at an angular velocity w = 2p rad / sec (60 rpm). Those skilled in the art will understand that this example is not meant to be limiting, and that the use of any angular velocity effective for establishing radio paths and transmitting data as described and claimed herein is within the scope of this disclosure. Those skilled in the art will understand that the angular velocity w used in a particular system will depend on factors such as the application performed by the system (transmitting data or maintaining a distributed ledger), the number of satellites in the constellation used by the system, and the amount and nature of information transferred over the inter-satellite link. It is expected that a velocity of approximately 1 revolution per minute (w ≈ 1 rpm) will be preferred for many of the systems described herein. While the orientation of the rotation axis will not be controlled, principles of physics dictate that each satellite assumes an axis of rotation passing through its center of mass, and that the axis of rotation precesses about an angular velocity co. However, as will become apparent from the following discussion, the orientation of the axis of rotation at any given time does not affect the creation of the radio link.

[0162] A rotating satellite increases the probability that a transmitted radio beam will be received by another satellite because the satellite antenna "sweeps" the area as the satellite rotates. This is shown in Figure 11A, a schematic cross-section through the "equator" of satellite S, which corresponds to equator 16 of satellite 10 in Figure 2. ω This can be understood by examining the figure. ωincludes five antennas 121, 122, 123, 124, and 125, each with a 35° HPBW, equally spaced about its equator 16 and rotating about the z-axis with angular velocity w. A RL located at the equatorial plane, away from the satellite, will "see" five antennas as the satellite makes one orbit. It will be understood that this number will be different for locations not in the equatorial plane, but the principle still applies. It will also be understood that most locations (including earth stations) at a distance from the satellite will still see multiple antennas as the satellite rotates, although the number may increase or decrease due to precession about the axis of rotation. Thus, the first satellite S ω A second satellite with its equatorial plane in the orbit of the Earth has about a 10% chance (5 antennas x 2% per antenna) of being able to create a radio link with a 6 dB gain increase relative to a satellite not deployed to rotate intentionally. The probability of creating a beam match with a ground station antenna increases similarly.

[0163] It will be appreciated that this is a highly idealized representation, ignoring factors such as the precession of satellites about their rotational axes, but nevertheless illustrates the concept that rotating satellites present an increased probability for the creation of a beam match between two satellites. Nevertheless, given the large number of probabilistically distributed orbiting satellites available for information transfer, the increased probability of beam matching using rotating satellites is sufficient in many, if not most, cases to enable the assembly of radio paths or distributed ledgers with higher quality links between the multiple satellites and ground stations of a system.

[0164] 1. Counter-rotating satellites

[0165] Alternatively, the satellites may be deployed with a percentage, e.g., 50%, rotating about their rotation axis in a first direction and the remainder rotating in the opposite direction. FIG. 11B uses like numerals for like parts of FIG. 11A and shows satellite S rotating in a first direction with angular velocity ω. ω1This principle is demonstrated by showing a second satellite Sω2 rotating at the same angular velocity −ω (in the opposite direction). ω1 Antenna 125 and Satellite S ω2 11B illustrates how the beam alignment of the antennas 124 on each satellite is maintained longer than if the two satellites were rotating in the same direction. That is, when the satellites are rotating in opposite directions, the opposing antennas on the satellites are traveling at essentially the same linear velocity relative to each other. On the other hand, when the satellites are rotating in the same direction, their relative linear velocity is twice their respective linear velocities. With a sufficient number of satellites in orbit, it is quite possible to have multiple counter-rotating satellites over any given geographic area over which a radio path is established. Therefore, the likelihood of quickly establishing a relatively long-lasting satellite-to-satellite link is increased by deploying at least some, preferably about one-half, of the satellites that rotate in the opposite direction from the others. Furthermore, not only will the two antennas on each satellite remain aligned longer, but as soon as they rotate out of view of each other, the two other antennas on the satellite will be aligned, thus enabling a rapid refresh of the radio link between the satellites. In the example shown in FIG. 11B, satellite S ω1 Antenna 121 and satellite S ω2 The antenna 125 is then aligned.

[0166] Like the example used to illustrate the improved utilization efficiency of rotating satellites discussed above, this is also an idealized description of how counter-rotating satellites can create a longer-lasting radio link between them; in addition, in addition to the assumptions underlying the above explanation, two counter-rotating satellites may not be present at any one time over the area where a radio path is desired between two ground stations. Nevertheless, these examples taken together illustrate the point that rotating satellites, particularly counter-rotating satellites, may provide a sufficient probability of establishing a relatively high-gain radio link between random-orbit satellites to enable reliable data communication between the two satellites. And, because antennas point in multiple directions (preferably throughout the spherical space surrounding the satellites), in most cases, the chances of establishing a radio link between the satellites may be enhanced by using rotating satellites.

[0167] 2. Satellites rotating at different angular velocities

[0168] A variation of the above embodiment employs satellites that rotate at different angular velocities. This variation is shown diagrammatically in FIG. 11C, where satellite S ω1 rotates with angular velocity ω1, and S ω2 rotate toward the other at a different angular velocity, −ω2. An advantage of this system is that the antennas on the counter-rotating satellites can be out of phase, in the sense that the antenna on one satellite can point directly into space between the antennas on the second satellite, as shown in Figure 11C. If the satellites were rotating at the same angular velocity, this situation could persist for a long time, thus weakening the radio link between the satellites or perhaps preventing the establishment of a link altogether. Rotating the satellites at different angular velocities increases the likelihood that the angularly positioned antennas on both satellites will face each other (be in phase), thereby making it possible to establish a useful radio link between them. For example, in the case shown in Figure 11C, satellite S ω1 The antenna 122 above is satellite S ω2The antennas on the satellites are exactly 180° out of phase, with the pointing directly into space between antennas 124 and 125 on the satellite. If π1 = 1.33 × β2, then satellite S ω1 Antenna 125 and Satellite S ω2 The antennas 125 are aligned in a straight line as the satellite rotates.

[0169] It is believed that the use of satellites rotating at different angular velocities would further reduce any possible delays in establishing inter-satellite and inter-satellite radio links. In an exemplary approach, the cohort of satellites can be divided into five groups having different angular velocities according to the following table: [Table 2] The above discussion explains how this can tend to increase the probability of establishing beam alignment between the antennas on each satellite.

[0170] For satellites used in the particular system described herein, angular velocities much lower than on the order of w ≈ 1 rpm may be preferred. As discussed in Section III.B., it is expected that an attitude-stabilized satellite will be more likely to form a link at lower angular velocities than a free satellite, regardless of its attitude. Furthermore, the improved antenna configurations discussed in Section III.C. are expected to improve the likelihood of forming links between different satellites.

[0171] By the same token, implementation of this system may also allow for more beam alignments in a given period of time because antennas on one satellite have a greater chance of aligning sufficiently with antennas on another satellite to form a beam alignment if the satellites are counter-rotating at different angular velocities. As two satellites rotate, there may not be a beam alignment at a specified time or for a particular interval. However, as they continue to rotate at different angular velocities, the antennas on the satellites are more likely to form a beam alignment because the antennas on each satellite are more likely to align at some point. This may take multiple satellite rotations, but rotating at different angular velocities greatly increases the probability of more matches occurring as the satellites continue to rotate. Thus, as satellites move in orbit and rotate about their axes providing multiple satellite cohorts, each rotating at different angular velocities, this likely increases the likelihood of generating more beam matches between pairs of satellites during any given time interval.

[0172] 3. Other Considerations

[0173] One technique for controlling satellite rotation is by intelligently configuring the satellite's solar panels to generate a torque about the satellite's axis of rotation due to the momentum of photons striking the solar panels. In one such embodiment, the solar panels have solar cells on only one side. For example, with reference to FIGS. 2 and 3, for a satellite deployed to rotate counterclockwise about the z-axis (as viewed from the negative z direction), each solar panel 14a would have one side, i.e., a side facing the viewer relative to the solar panel 14a on the right side in FIG. 3, and a side facing the viewer relative to the other solar panel 14a on the left side in FIG. 3. The remaining solar panels would still have solar cells on both sides. Although larger solar panels would increase air resistance on the satellite, it is believed possible through intelligent design to provide solar panels sized, configured, and oriented to generate a net torque on the satellite.

[0174] Similarly, it is believed that the mass of satellite components can be selectively distributed to rotate the satellite components about a particular axis. Because batteries are expected to form a large proportion of the satellite's mass, they will preferably be located at the satellite's center of mass and have a symmetric mass distribution about the axis of rotation. Furthermore, the unintended effect of the Earth's magnetic field on the satellite's rotation can be minimized by using non-ferromagnetic materials, such as aluminum, for major structural components whenever possible.

[0175] Those skilled in the art will understand that excessive angular velocity can generate large centrifugal forces that can potentially damage a satellite. Atmospheric drag limits rotation speed to an extent that depends on the satellite's altitude, and it is expected that the design of any of the above techniques for maintaining rotation can be adjusted (e.g., through area selection and solar panel placement) to prevent the generation of damaging centrifugal forces. However, because satellite altitudes are not otherwise controlled, the rotation speed of some of them may be reduced, but they will still be usable as nodes in a communications system. And, to the extent that older satellites continue to rotate at lower angular velocities, the effect will be to automatically take advantage of the improved performance made possible by using satellites rotating at different angular velocities. Similarly, satellites that become unusable for any reason, such as damage from excessive centrifugal forces, can be easily replaced because they are inexpensive to construct, launch, and deploy.

[0176] As noted above, some or all of the above-described passive means for controlling the satellite's attitude can be used. That is, in one variation, one or more solar panels could have solar cells on only one side of the satellite so as to exert an unbalanced moment on the satellite, causing it to tip over. Another variation could involve placing ferromagnetic materials at selected locations on the satellite that would generate forces that change magnitude and direction as the satellite traverses the Earth's magnetic field.

[0177] B. Satellite configuration with attitude stabilization

[0178] Another approach that can increase the probability of creating a wireless link between stochastically distributed satellites is to employ a satellite configuration that makes more antennas available for pairing with other satellites. A first alternative configuration is depicted schematically in Figures 12-15. Figure 12 is a bottom perspective view of a cylindrical satellite 110 incorporating this embodiment. Figure 13 is an exploded view of the satellite's circular sidewall, showing the placement of the satellite antennas. Figure 14 is a side view of the satellite, and Figure 15 is a top view showing the beamwidth of the satellite antennas. The terms "top" and "bottom" are used for convenience to indicate directions away from and toward the Earth's surface, respectively, when the satellite is in its operating orientation, and it will be understood that the terms "side" or "sidewall" are similarly relative to "top" and "bottom."

[0179] Referring to the figure, satellite 110 is generally cylindrical in shape with antenna 112, such as antenna 12 in satellite 10 shown in Figure 3. Solar panels 114, shown in Figure 14, are on top surface 130 of satellite 110. In this exemplary embodiment, the satellite has twelve antennas 112T1, 112T2, 112T3, 112T4, 112T5, 112T6, 112T7, 112T8, 112T9, 112T10, 112T11, 112T12, 112T13, 112T14, 112T15, 112T16, 112T17, 112T18, 112T19, 112T20, 112T21, 112T22, 112T23, 112T24, 112T25, 112T26, 112T27, 112T28, 112T29, 112T30, 112T31, 112T32, 112T33, 112T34, 112T35, 112T36, 112T37, 112T38, 112T39, 112T40, 112T41, 112T42, 112T43, 112T44, 112T45, 112T46, 112T47, 112T48, 112T49, 112T50, 112T51, 112T52, 112T53, 112T54, 112T55, 10 , 112T 11 , and 112T 12, The antenna array includes a total of 24 antennas, with the top row of antennas 112B1, 112B2, 112B6, 112B7, 112B8, and 112B9. A second row of 12 antennas is disposed below the upper row. For clarity, FIG. 13 shows only antennas 112B1, 112B2, 112B6, 112B7, 112B8, and 112B9, but it can be seen from FIG. 13 that antennas 112B3, 112B4, and 112B5 (not shown) are equally spaced between antennas 112B1 and 112B6, and antenna 112B6 (not shown) is equally spaced between antennas 112B9 and 112B9. 10 , 112B 11 , and 112B 12It is understood that the antennas 112 are equally spaced apart. All of the antennas 112 have parabolic reflectors with radially arranged axes in the horizontal plane, as shown by the centerline 140 of antenna 112T4 in FIG. 12, and have circular cross sections perpendicular to their parabolic axes. The solid dotted lines in FIGS. 12 and 14 also represent antennas, not shown, that completely wrap around the sidewalls, as shown in FIGS. 13 and 15. In this exemplary embodiment, all of the antennas 112 have a beamwidth of 30° and are symmetrical about the centerline 140. It should be further understood that the antenna configurations and operating characteristics discussed herein are meant to be examples only, and that one skilled in the art would be able to design antennas that meet the performance parameters discussed herein.

[0180] The satellite sidewall 134 includes an antenna area AR bounded by a halftone-dash circle, as seen in Figures 12-14. The antenna area has a configuration that enhances the satellite's operational characteristics. In particular, the satellite's dimensions and the antenna arrangement and diameter provide antenna coverage of 65% or more of the antenna area, thus increasing the probability of establishing a radio link with antennas on other satellites. In this embodiment, the satellite diameter D is 500 mm, the antenna area AR width WD is 250 mm, the antenna aperture diameter d is 110 mm, and the spacing s between antennas is 15 mm. Four downward-facing antennas 150a, 150b, 150c, and 150d are positioned at the bottom of the satellite 100, as further described below. Each of the antennas 150 comprises a parabolic reflector with a circular cross-section and is designed to transmit and receive radio beams across a 60° beamwidth. It will be understood that other antenna arrangements are possible, and the dimensions of this embodiment are intended to be an example of one such arrangement and are not intended to limit the scope of the claims that follow.

[0181] The satellite's upper surface 130 is slightly domed outward, as seen in FIG. 14, to increase the spherical angle it exposes to solar radiation. The cylindrical satellite's axis 136 is maintained, within certain limits, in a substantially perpendicular orientation relative to the Earth's surface by means described below. The upper and lower rows of antennas are then symmetrically positioned relative to a plane 138 (see FIG. 13) perpendicular to the satellite axis, so that the antennas are maintained substantially horizontal to facilitate the formation of radio links by pairing with antennas on other satellites. This also keeps the downward-pointing antenna 150 in an orientation that can more easily form radio links with antennas on ground nodes. However, as described immediately below, attitude stabilization techniques applied to the satellite may allow the satellite to wobble a limited amount from horizontal. The domed configuration of the solar panels may keep a portion of them at a more direct angle to the Sun, thus helping to maintain the charge of the satellite's batteries.

[0182] Satellite 110 further includes an upper region TR and a lower region BR that provide sufficient interior volume within the satellite for the operational components and modules described above in connection with FIG. 3 . In this example, the upper region has a width WT of 100 mm, and the lower region has a width of 250 mm. The interior volume of the lower region is also intended to provide sufficient interior space to accommodate downward-pointing antennas 150, and the upper region is intended to have sufficient space to accommodate structures related to solar panels 114. In one preferred configuration, antennas 112 are angled downward to accommodate the curvature of the Earth and point more directly at other satellites. This effect can be understood by considering the satellite of FIG. 9, where radio links between satellites form an angle with the satellites pointing slightly downward relative to the horizontal. It is also possible, in a given system, for some of the antennas 112 to point slightly upward to facilitate the formation of radio links with satellites at higher altitudes.

[0183] As mentioned, the ability to form a link with a satellite that does not have an antenna capable of forming a radio link in any direction (such as satellite 10 of FIGS. 2 and 3) requires that the satellite's attitude be stable within certain limits relative to the horizon. FIG. 16 is a cross-section taken along line 16-16 of FIG. 14 and schematically illustrates an embodiment of a satellite stabilization mechanism for maintaining satellite 110 in an upright position with its solar panels facing away from the Earth's surface. FIG. 16 shows three mutually orthogonal axes, x, y, and z. The x and y axes lie in plane 138 shown in FIG. 13. The z axis coincides with satellite axis 136, and the concentric circles indicate that the z axis points outward from the plane of the drawing. The object is to orient the satellite so that axis 136 points away from the Earth's surface and plane 138 is parallel to the Earth's surface.

[0184] The satellite's stabilization mechanism includes five electromagnets. Two electromagnets, 160 and 162, are aligned in the y-direction, and two electromagnets, 164 and 166, are aligned in the x-direction. Figures 16 and 17 depict the satellite near the equator, with the dotted line MF representing the Earth's magnetic field. In the position shown, activating electromagnets 160 and 162 tends to align the satellite's y-axis with the line of magnetic flux MF, which points north and is parallel to the Earth's surface at the equator. This stabilizes the satellite against rotation about the x-axis. Deactivating electromagnets 160 and 162 and activating electromagnets 164 and 166 rotates the satellite about the z-axis, aligning the satellite's x-axis with the Earth's magnetic field. This stabilizes the satellite against rotation about the y-axis.

[0185] The Earth's magnetic field may not be strong enough to perfectly align the satellite's axis in the described manner. Additionally, plane 138 may deviate slightly from horizontal as the satellite moves away from the equator. However, any misalignment or deviation from horizontal is expected to be small, perhaps 10° or less. This deviation is sometimes referred to herein as satellite "wobble," and in preferred embodiments, the amount of wobble of plane 138 from horizontal is less than 20°, and more preferably 10° or less.

[0186] In another variation, electromagnets 160, 162, 164, and 166 can be sequentially activated and deactivated to impart a rotational moment about satellite axis 136 to achieve the aforementioned benefits provided by a rotating satellite. Applying a rotational torque to the satellite twice per orbit as the satellite passes the equator tends to mitigate the effects of any wobble that may strike the satellite's alignment antenna at different angles relative to the horizontal. For example, to impart a rotation about the z-axis of one revolution per minute (ω ≈ 1 rpm), the satellite is horizontally stabilized as previously described. Then, electromagnets 160, 162, 164, and 168 are each activated whenever the satellite is near the equator and deactivated every 15 hours. Thus, each is then energized to align with the magnetic flux lines MF while activated, thereby exerting a torque on the satellite about the z-axis. Cyclic successive activation of the electromagnets results in the satellite rotating at an angular velocity determined by the period of activation of each magnet. In a preferred embodiment, the satellite includes an accelerometer (not shown) to detect its angular velocity. Control circuitry incorporated into the satellite's computer system can be programmed to activate and deactivate magnets 160-166 in a sequence that maintains the satellite's angular velocity about the z-axis at a desired value.

[0187] Figure 17 shows a fifth electromagnet 168 positioned at an appropriate angle θ relative to the satellite's y-axis; the electromagnet is used to point the satellite to the right when its z-axis is not pointing upward (away from the Earth's surface). This condition can be detected by the satellite in a number of ways. For example, the satellite's operating system can monitor the output of its solar panels and determine if the electrical output is below a certain threshold for more than half an orbit, indicating that the satellite is not pointing directly at the Sun. Another indication would be if the downward-pointing antenna 150 has not received a radio signal for a predetermined period of time.

[0188] If the satellite determines it needs to right itself vertically, a righting sequence is initiated when the satellite is over the equator. If the satellite is rotating about its z-axis, it is stopped by activating electromagnet 160 and deactivating electromagnets 164 and 166 in a preprogrammed sequence. Electromagnet 170 is momentarily activated, thus generating a moment M about the satellite's x-axis as activated magnet 170 attempts to align itself with the lines of Earth's magnetic flux MF. Magnet 170 is deactivated before aligning with the magnetic flux lines MF so that it can continue to rotate due to lack of atmospheric resistance. Using basic principles of physics, the satellite's onboard computer can calculate the magnitude and duration of the force required to generate a moment M that rotates the satellite 180°, depending on the size of magnet 170, its orientation, the satellite's altitude (and therefore the strength of the Earth's magnetic field at the satellite's location), and the satellite's known mass and center of gravity.

[0189] Another satellite embodiment includes a more omnidirectional satellite, such as satellite 210, shown in perspective view in FIG. 18. This satellite has a hemispherical shape in the general form of satellite 10 shown in FIGS. 2 and 3, but is truncated to include only a portion of a sphere. (FIG. 14 uses reference numerals in the "200" series to indicate features referenced in the previously depicted satellite embodiment with the same last two digits.) Satellite 210 has an upper surface 230 on which solar panels 214 are disposed. The upper surface may be dome-shaped, like upper surface 130 of satellite 110 shown in FIG. 14. Antennas 212a, 212b, 212c, 212d, etc., are distributed around the periphery of the satellite's sphere, as in satellite 10, and are represented by solid dashed lines in FIG. 14. Satellite 210 preferably includes a satellite stabilization mechanism, such as that shown in FIG. 13, for use with satellite 110.

[0190] C. Alternative Antenna Configurations

[0191] FIG. 19 illustrates an antenna configuration that can further increase the probability of pairing antennas within different satellites by using high-gain radio beams, resulting in a faster creation of radio links with acceptable quality (Q) for the radio path. FIG. 19 illustrates a portion of the circumferentially extending antenna area AR shown in FIG. 13, including upper-stage antennas 112T3, 112T4, 112T5, 112T6, and 112T7 and lower-stage antennas 112B3, 112B4, 112B5, 112B6, 112B7, and 112B8. The remaining antennas in the upper and lower stages have the same structure. While these antenna configurations are discussed in relation to satellite 110, it will be understood that they can be used with any of the satellite configurations and deployment strategies already discussed (e.g., rotating satellites and counter-rotating satellites).

[0192] In this embodiment, each of the antennas 112 is a parabolic antenna having six feeds F1-F6. The feeds F1-F6 are spaced equidistant from one another and spaced apart from the central axis of the antenna's parabolic reflector. No antenna feed is located on the central axis of the parabolic reflector. The shape and curvature of the antenna reflector can be selected according to known multi-feed antenna designs and operating principles. It should also be understood that the antenna reflector can have a non-parabolic topology, such as spherical, a spherical / parabolic combination, and others, to maximize the operating characteristics of the system embodiments described herein, and that the number of antennas and the number of feeds per antenna depend on the satellite design and the desired operating characteristics of the system. More or fewer antennas and feeds may be used with the satellites discussed in this disclosure.

[0193] FIG. 20 illustrates the functionality of an exemplary computer circuit for processing signals received by and transmitted by an antenna feed. Noh mapAs with all of the foregoing descriptions of computer and processing circuitry, the boxes and connections between them in FIG. 20 are used only as an aid in describing the operation of the present embodiment. Designing and implementing appropriate computer components, including the hardware, firmware, and / or software required to perform the functions described herein, is well within the skill of one of ordinary skill in the art. Furthermore, the circuit diagram of FIG. 20 does not suggest a particular architecture for performing the described functions.

[0194] For the purpose of this description, Figure 20 shows the upper antenna modules 112T1 and 112T 12 19. Only the upper antenna module and the lower antenna module 112B are shown. All remaining upper and lower antenna modules 112B are omitted from the diagram for clarity. Each antenna module has associated with it a microprocessor "μprocess" for processing signals introduced to and received from the antenna feeds. Individual antenna microprocessors are identified in FIG. 20 by the notation μprocessor(112TX), where "X" is the number of the associated antenna module in accordance with the above description in FIG. 19. Thus, in the diagram, "μproc(112T1)" refers to the on-board circuitry for processing signals introduced to and received from feeds F1 through F6 of antenna module T12T1. Similarly, "μproc(112T12)" refers to the on-board circuitry for processing signals introduced to and received from feeds F1 through F6 of antenna module 112T1. 12 The other antenna modules 112T2-112T show on-board circuitry for processing signals introduced into and received from feeds F1-F6. 11Each is associated with its own microprocessor, as represented by the dots between μproc (112T1) and μproc (112T12) in FIG. 20. Each microprocessor μproc includes a radio transceiver, indicated by R1 through R6, with each transceiver associated with a corresponding feed F1 through F6 of its antenna. The transceiver converts RF signals received by the feed into a data stream and converts the data stream into an RF signal to be broadcast by the antenna.

[0195] The antenna module microprocessors are connected to the satellite's CPU 40 by power and data lines 40(112T1) through 40(112T12). The dots between lines 40(112T1) and 40(112T12) in FIG. 20 indicate that similar power and data lines also connect corresponding power and data lines to each antenna module's microprocessor μproc(112T2) through μproc(112T11). As seen in FIG. 19, satellite antenna feeds are numbered, and the circuitry shown in FIG. 20 enables the satellite to identify the antenna feed on which a signal, such as a routing message, is received so that data transmissions can be sent on the same antenna feed, thereby enabling the routing protocols and data transmission methods, as well as the distributed ledger embodiments described above, to be effective.

[0196] Using 24 antennas with six feeds per antenna is the functional equivalent of 144 separate antennas. While the latter configuration is within the scope of this disclosure in its broadest aspects, it eliminates many of its key objectives, one of which is providing a system in which satellites are very small, lightweight, and have minimal launch costs. While satellites with multi-feed antennas will typically be larger and slightly heavier than single-feed embodiments, they will still be orders of magnitude smaller and lighter than satellites with single-feed antennas sufficient to achieve the same functionality. Furthermore, increasing the number of routing messages sent from each satellite by several times increases the likelihood of establishing a radio link with a ground station or another satellite. This reduces the number of satellites required to achieve the same results as using satellites with single-feed antennas.

[0197] Two important aspects of the satellite design depicted in Figure 19 are the elimination of the central antenna feed and the use of brackets 116 to mount peripheral feeds F1 through F6 and suspend them from the antenna limb. Both of these features serve to expose more of the antenna reflector to the peripheral feed. This design makes the antenna less susceptible to sidelobe generation and eliminates interference from the central feed with signals transmitted and received by the antenna peripheral feeds.

[0198] Due to the increased spatial density of antenna feeds, at least some incoming routing messages used in the routing protocol described above may be received by more than one antenna feed F of a particular antenna. Each antenna microprocessor μproc identifies the power feed that would provide the highest quality radio link if that antenna module were used in the radio path. This can be done using any of the criteria already described above. This information is passed to the satellite's CPU 40 via appropriate power and data lines 40 (112T1) through 40 (112T12) associated with the upper antenna row or inappropriate power and data lines 40 (112B1) through 40 (112B123) associated with the lower antenna row of FIG. 19, which then performs a self-evaluation of all selected radio signals by the individual antenna microprocessor. A similar procedure occurs when receiving radio signals (routing messages) received on feeds of adjacent antenna modules. For example, an incoming signal may be received by four feeds on adjacent antenna modules, such as feeds F1 and F2 of antenna 112B4, feed F4 of antenna 112T3, and feed F5 of antenna 112T4. In that case, the microprocessor μproc (112B4) associated with antenna 112B4 determines which of its feeds F1 or F2 provides the better (higher quality) radio link and provides decision parameters to support that decision to satellite CPU 40. Path quality information from feed F4 of antenna 112T3 and feed F5 of antenna 112T4 is also sent to satellite CPU 40, which uses all of the data received from the antenna modules to identify the antenna module and its feed to use for data transmission as described above.

[0199] D. CubeSat Compatibility

[0200] In this context, "CubeSat" refers to two distinct concepts for building and deploying microsatellites: one essentially uses standard-sized packaging as a chassis for the satellite's components; the other essentially provides a container for the satellite to be deployed by releasing it from the container into orbit. "CubeSat" refers to the dimensions of the base unit, 4 inches by 4 inches by 4.5 inches (10 cm by 10 cm by 11.35 cm). CubeSats are available in multiples of that base unit, and examples of the base unit that makes up a particular CubeSat are often referred to (e.g., "3U," "6U," etc.). The underlying principle is that launch and deployment costs can be reduced if different satellite sizes and shapes for different missions nonetheless have the same or similar form factor. Similarly, current technology is only used for small, dedicated satellites.

[0201] FIG. 21 is a schematic diagram of one possible embodiment of a satellite usable in the above-described system, embodied in a cubesat 310 comprising six units U1, U2, U3, U4, U5, and U6. The units are configured such that the satellite has an upper row of eight antennas 312T and a lower row of eight antennas 312B (the opposite side of the unit, not visible in the drawing, has antennas corresponding to those seen in FIG. 21). The attitude of the satellite 310 can be stabilized using the techniques described above (see, e.g., the description of FIG. 17). With the satellite oriented in this manner, the top of each unit U can include an array of solar panels 314 corresponding to the solar panels 114 and 214 of satellites 110 and 210 (see FIGS. 14 and 18). The bottom of each unit U can include one or more downward-pointing antennas (not shown) equivalent to the downward-pointing antenna 150 of satellite 110 (see FIG. 12). Additionally, the antennas 312 can have the multi-feed configuration discussed above in connection with FIGS. 19 and 20.

[0202] FIG. 21 illustrates that satellites according to various embodiments, features, and operating characteristics described herein are particularly suited to CubeSat technology. They are small and lightweight, do not carry rocket fuel, and therefore do not require special handling during launch. They can be built on a CubeSat-type chassis or deployed within a CubeSat package, as shown in FIG. 21. It should also be understood that FIG. 21 is intended as an example of a CubeSat implementation of a satellite that can be used in the systems described herein. Larger CubeSats, i.e., more than six units, are possible. Another configuration variation can use a satellite that fits into a multi-unit CubeSat envelope, but is otherwise integrally constructed with any of the features described herein. For example, a satellite designed for use with any of the systems herein can have a matching envelope, e.g., a 12U CubeSat (3 x 2 x 2), but cannot be constructed as a separate CubeSat unit in the manner suggested by FIG. 21.

[0203] IV. Further Applications of the Disclosed Concepts

[0204] FIG. 22 illustrates the versatility afforded by the concepts disclosed herein in implementing different types of communication systems that can enable communication between system nodes. In the notation used in FIG. 22, general types of ground nodes are identified by the reference numerals GN100, GN200, and GN300. These may be cellular towers, WiFi routers, etc. These are sometimes referred to as "drops" by those skilled in the art of wireless communications, which may refer to devices that serve one or more ground-based users or ground-based networks. Other types of ground-based nodes with which the systems disclosed herein may be used are individual handheld devices HD, IoT building devices that form part of the so-called "Internet of Things," which is generally taken to mean vehicles V, which may incorporate devices such as networked physical devices (also called "connected devices" and "smart devices") that incorporate electronics, software, sensors, actuators, and network connectivity that enable the collection and exchange of data, and interconnected devices that are part of the Internet of Things and devices comparable to handheld devices HD.

[0205] Figure 22 also shows some examples of different types of airborne nodes that the system can incorporate. References SVLO1, SVLO2, and SVLO3 refer to satellites in very low Earth orbit (in this example, at an altitude of 100 miles or less). As previously mentioned, lower altitude satellites would increase the strength of radio signals exchanged with locations on the ground. Reference designator SLO refers to a satellite in low Earth orbit, in this example at an altitude of approximately 500 miles. Additionally, non-orbital airborne nodes can also be used in the systems described herein. For example, nodes similar in structure to the satellites described above can be suspended from balloon BN1, while BN2 can float freely within a stratosphere (or at a lower altitude). Balloons have proven useful for providing communication services (e.g., internet access, email) to relatively small areas on the Earth's surface. Another variation of aircraft-based nodes includes unmanned aerial vehicles ("drones") DR1 and DR2, deployed over a given area at an altitude of 1,000 to 2,000 feet, although other altitudes may be desirable depending on the particular area served by the system. The use of low-flying drones is expected to enable easier communication directly from handheld devices and other personal devices than satellite-based systems, as the drones are closer to such devices than satellite-only systems. The reference GEO refers to satellites in geostationary orbit with which the satellites and other air-based nodes described herein can communicate for data transmission.

[0206] FIG. 22 illustrates some examples of path segments that can be created in a system using one or more types of airborne nodes, such as those shown in the figure. For example, a route between a handheld device HD and a vehicle V can include a link to a drone, such as DR1, a sub-route that may include other drones (not shown), one or more very low earth orbiting satellites, represented by satellite SVLO1, one or more balloons, represented by balloons, such as BN2, and a link to vehicle V, shown as a solid line in the figure. Another example of a wireless path is shown as a dash-dot line in FIG. 22 between terrestrial nodes GN100 and GN200. This path includes a sub-route that includes one or more balloons BN (represented by balloon BN1), one or more very low earth orbiting satellites (represented by satellite SVLO2), and one or more drones (represented by drone D2). A third example is shown as a dash-dot line between a building IoT that houses devices integrated into the Internet of Things. This path includes a sub-route that includes one or more very low Earth orbit satellites (represented by satellite SVLO3), one or more geostationary satellites already deployed in other systems (represented by satellite GEO), and one or more low Earth orbit satellites (represented by satellite SLO). It will be understood from this description that each of the airborne node types DR, BN, SVLO, SLO, and GEO in the figure is intended to represent a possible node in a sub-route that may include multiple links between nodes of different or similar types.

[0207] The use of balloons as nodes has been suggested previously. Google is believed to be testing a system it calls Project Loon to provide internet access to rural and remote areas. According to reports, high-altitude balloons would be placed in the stratosphere at an altitude of approximately 18 km (11 miles) to create an airborne wireless network. The balloons would use publicly available wind data to identify wind layers with desired speeds and directions, then adjust their stratospheric altitudes to navigate within those wind layers. Signals travel from balloon to balloon through the balloon network, then to ground base stations connected to internet service providers (ISPs), and then onto the global internet. See, e.g., "Project Loon," Wikipedia: https: / / en.wikipedia.org / wiki / Project_Loon (last visited September 20, 2017). Those skilled in the art could easily adapt such balloon-based systems to use the various satellite-based nodes described in this disclosure.

[0208] V. Summary and Conclusions

[0209] The preferred communications system and method described above uses probabilistically distributed orbiting satellites to take advantage of the probabilities inherent in such systems to reliably construct radio paths between satellites and between satellites and ground stations that are robust enough to support data communications. Conventional satellite-based communications systems designed to enable data communications with ground stations located across a wide swath of the Earth's surface use satellites maintained in constrained orbits such that every satellite knows with virtual certainty the location of every other satellite with which it can communicate. This requires large, heavy satellites equipped with rocket thrusters or other heavy, complex mechanisms to maintain each satellite in a precise position and at a tightly controlled attitude to ensure that antennas on the satellites can pair and form inter-satellite radio links.

[0210] The systems and methods described and claimed herein break this paradigm by using satellites that are probabilistically distributed and do not need to know the location of any other satellites to pair antennas on each satellite and form a wireless link. In some embodiments, data can be reliably transmitted via satellite to ground stations around the world, even if the satellites do not have any attitude control.

[0211] Various satellite architecture enhancements are available to increase the reliability and speed of data transmission and reduce the cost of placing satellites in orbit. In a basic configuration, the satellite is spherical or nearly spherical, with antennas distributed around all or part of the sphere, enabling the transmission of radio signals in all or almost all spherical directions. In one enhancement, the satellite has antennas within a circular band around the satellite, as illustrated in Figures 12-15. This, combined with partial attitude stabilization illustrated by Figures 16 and 17, further enhances the reliability of the system in creating radio links between satellites and between satellites and ground stations. The passive stabilization means described herein require no moving parts and can control the satellite orientation within a horizontal plane, for example, ±10°, which is sufficient to enhance antenna pairing. Rotating the satellite can further increase the probability of antenna pairing with various disclosed satellite configurations. In another embodiment, the antenna includes a parabolic reflector with multiple feeds attached to the antenna rim, which allows for the transmission and reception of more radio signals per satellite while improving antenna performance by eliminating a central feed. The satellites can also be made compact enough to meet CubeSat standards.

[0212] The unique routing protocol disclosed herein is tailored for transmitting data to a ground station via a system of probabilistically distributed orbiting satellites. The ground station has a unique address that identifies itself and the zone in which it is located. A local area network associated with a ground node includes at least one satellite that stores the identifier of a satellite antenna paired with a ground station antenna to form a wireless link for transmitting satellite-borne data to the ground station. Other satellites in the local area network store the ground node address and the identifier of an antenna paired with an antenna in another satellite that also stores the ground node address. The wide area network includes at least one satellite, each of which stores the identification of an antenna paired with an antenna of another satellite that stores the zone of the initiating satellite to form at least one inter-satellite wireless link. The local area network establishes subroutes known to connect to the destination ground station, while the wide area network concentrates data transmissions toward ground station zones that are likely to encounter satellites in the ground station's local area network. If the data-bearing satellite is not in the local area network or the wide area network, the satellite transmits data toward the ground node's zone.

[0213] The satellite-based distributed ledger system is supported by multiple probabilistically distributed orbiting satellites and can distribute data communications received by at least one of the satellites from a ground station. The satellites provide a common clock to all satellites and use GNSS modules to transmit all of the stored data communications on substantially all antennas of all satellites during unique time slots. While distribution throughout the system is driven by probability as in other applications of the system described herein, a sufficient number of satellites in orbit will ensure rapid dissemination of data to all satellites.

[0214] Those skilled in the art will readily appreciate that only selected preferred embodiments of the present invention have been shown and described, and will understand that various changes and modifications, other than those specifically mentioned above, can be made that depart from the spirit and scope of the present invention, which is defined solely by the following claims.

Claims

1. 1. A wireless communication system for transmitting data from a first terrestrial node to a second terrestrial node over a wireless path, the system including the first terrestrial node, the second terrestrial node, and a plurality of orbiting satellite nodes as system nodes, the wireless path including at least two of the plurality of orbiting satellite nodes, each of the plurality of orbiting satellite nodes: a plurality of antennas for transmitting and receiving radio signals in different directions; a path generation circuit for receiving a routing message transmitted from another system node and transmitting the routing message to the other system node; a memory for storing an identifier of the antenna from which each routing message was received; Including, the route generation circuitry of the primary orbiting satellite node determines a value of a first parameter associated with an origination routing message received from the second terrestrial node, the value of the first parameter indicating suitability of the primary orbiting satellite node for incorporation into a wireless link for transmitting the data to the second terrestrial node; the route generation circuitry of the primary orbiting satellite node transmits on a plurality of the antennas a primary routing message including address information of the second terrestrial node and the value of the first parameter associated with the originating routing message; the route generation circuitry of at least one secondary satellite node determines a value of a second parameter associated with each primary routing message received from a respective primary satellite node, the value of the second parameter being indicative of the suitability of a wireless link including the secondary satellite node in a wireless path for transmitting data originating from the first terrestrial node via the primary satellite node; A system characterized by:

2. the route generation circuit of at least one secondary satellite node identifies a primary routing message having the address information included in the origination routing message, the primary routing message representing a preferred wireless route from the secondary satellite node to the second terrestrial node, the preferred wireless route including a first wireless link having a value corresponding to the value of the first parameter and a second wireless link having a value corresponding to the value of the second parameter, both of the first and second wireless links having a value higher than the value of any first or second wireless link of any other wireless route from a given secondary satellite node to the second terrestrial node; the memory of the primary orbiting satellite node in the preferred wireless path stores the address information and the identifier of the antenna that received the initiation routing message associated with the preferred wireless path; the memory of the secondary orbiting satellite node in the preferred wireless path stores the address information, the identifier of the antenna that received the preferred primary routing message, and a lower link value of the first wireless link value and the second wireless link value in the preferred wireless path; 2. The system of claim 1.

3. a plurality of the secondary orbiting satellite nodes included in the preferred wireless path transmit, via a plurality of antennas, one or more secondary routing messages including the address information and the value of the lower link in the preferred wireless path; The route generation circuit of at least one tertiary satellite node (1) determines a value of a third parameter associated with a corresponding secondary routing message received from each secondary satellite node and matches it with the value of the lower link included in the associated secondary routing message; (2) identifies a secondary routing message representing a preferred wireless route from the tertiary satellite node identified in the origination routing message to the second terrestrial node, the preferred wireless route including a third wireless link between the tertiary satellite node and the secondary satellite node associated with the corresponding secondary routing message, the third wireless link having a value corresponding to the value of the third parameter, whereby all of the wireless links associated with a preferred wireless route have a higher value than any of the first, second, or third wireless links associated with any other wireless route from a given tertiary satellite node to the second terrestrial node; the memory of the tertiary orbiting satellite node stores the identifier and address information of the antenna that received the secondary routing message associated with the preferred wireless path; 3. The system of claim 2.

4. 3. The system of claim 2, wherein the value of the wireless link in the preferred wireless path exceeds a predetermined minimum value.

5. 4. The system of claim 3, wherein the route generation circuitry of the primary orbiting satellite node and the route generation circuitry of the secondary and tertiary orbiting satellite nodes transmit announce routing messages containing the address information identifying the second terrestrial node over multiple antennas.

6. 10. The system of claim 1, wherein at least some of said primary and secondary orbiting satellite nodes rotate.

7. 10. The system of claim 1, wherein at least some of said plurality of orbiting satellite nodes further include selectively energized electromagnets for interacting with the Earth's magnetic field to generate moments on said primary and secondary orbiting satellite nodes.

8. The system of claim 1 , wherein at least some of said primary and secondary orbiting satellite nodes include attitude stabilization.

9. 10. The system of claim 1, wherein a plurality of said primary and secondary orbiting satellite nodes include attitude stabilization means including electromagnets that are selectively energized to align at least some of said primary and secondary orbiting satellite nodes with the Earth's magnetic field.

10. 4. The system of claim 3, wherein the antennas comprise parabolic reflectors, each of the parabolic reflectors including a plurality of feeds attached to a periphery of the parabolic reflector, and the identifiers of the antennas stored in the memories of the primary, secondary, and tertiary orbiting satellite nodes include the identifiers of each of the antenna feeds of the primary, secondary, and tertiary orbiting satellite nodes.

11. The system of claim 1 , wherein the system node further comprises at least one of an unmanned aerial vehicle, a balloon, and a geostationary satellite.

12. 10. The system of claim 1, wherein said multiple orbital satellite nodes include multiple cohorts of satellites in orbits at different altitudes.

13. 1. A wireless communication system including a plurality of wide area orbit satellites for transmitting data to a second terrestrial node via a wireless path from a first terrestrial node to the second terrestrial node, the system including a destination orbit satellite and at least one other wide area orbit satellite, each of the plurality of wide area orbit satellites comprising: a plurality of antennas for transmitting and receiving radio signals in different directions; a route generation circuit for receiving a wide-area routing message transmitted from another system node and transmitting the wide-area routing message to the other system node; a memory for storing an identifier of the antenna from which each wide-area routing message was received; Including, the route generation circuit of the primary wide area orbit satellite determines a value of a first parameter associated with an initiating wide area routing message received from the destination wide area orbit satellite, the value of the first parameter indicating suitability for incorporation into a wide area wireless link including the primary wide area orbit satellite as a system node in a wide area wireless path for transmitting the data to the destination wide area orbit satellite; the route generation circuitry of the primary wide-area orbit satellite transmits, at a plurality of the antennas, a primary wide-area routing message, the primary wide-area routing message including address information identifying the destination wide-area orbit satellite and the value of the first parameter associated with the initiating wide-area routing message; The system is characterized in that the route generation circuit of at least one secondary wide area orbit satellite determines a value of a second parameter associated with each primary wide area routing message received from a respective primary wide area orbit satellite, the value of the second parameter indicating suitability of a wide area wireless link including the secondary wide area orbit satellite as a node in a wide area wireless path for transmitting the data to each of the primary wide area orbit satellites.

14. the route generation circuit of each secondary wide area orbit satellite identifies a preferred primary wide area routing message representing a first wide area wireless route from the secondary wide area orbit satellite to the destination orbit satellite, the first wide area wireless link having a value corresponding to the value of the first parameter and a second wide area wireless link having a value corresponding to the value of the second parameter, whereby both the first and second wide area wireless links have values ​​greater than the values ​​of any other first or second wide area wireless links from a given secondary wide area orbit satellite to the destination orbit satellite; the memory of the secondary wide-area orbit satellite in the preferred wide-area wireless path stores the address information, the identifier of the antenna from which the primary wide-area routing message associated with the preferred wide-area wireless path was received, and a lower link value of the first wide-area wireless link value and the second wide-area wireless link value; 14. The system of claim 13.

15. further comprising at least one tertiary wide area orbit satellite for receiving one or more secondary wide area routing messages transmitted on a plurality of antennas of one or more secondary wide area orbit satellites in the preferred wide area wireless path; The route generation circuit of at least one of the tertiary wide area orbit satellites (1) determines a value of a third parameter associated with a corresponding secondary wide area routing message received from each secondary wide area orbit satellite and matches it to the value of the lower link included in the secondary wide area routing message; (2) identifies a secondary wide area routing message representing a preferred wide area wireless route from the tertiary wide area orbit satellite identified in the origination wide area routing message to the destination wide area orbit satellite, the preferred wide area wireless route including a third wide area wireless link between the tertiary wide area orbit satellite associated with the corresponding secondary wide area routing message and the secondary wide area orbit satellite, the third wide area wireless link having a value corresponding to the value of the third parameter, whereby all of the wide area wireless links associated with the preferred wide area wireless route have a value greater than any of the first, second, or third wide area wireless links associated with any other wide area wireless route from a given tertiary wide area orbit satellite; the memory of the tertiary wide area orbit satellite stores the identifier of the antenna that received the secondary wide area routing message associated with the preferred wide area wireless path.

15. The system of claim 14.

16. 15. The system of claim 14, wherein the values ​​for both of the wide-area wireless links in the preferred wide-area wireless path exceed a predetermined minimum value.

17. 15. The system of claim 14, wherein at least some of the primary and secondary wide area orbit satellites rotate.

18. 18. The system of claim 17, wherein at least some of the plurality of wide area orbit satellites further comprise selectively energized electromagnets for interacting with the Earth's magnetic field to generate moments on at least some of the primary and secondary wide area orbit satellites.

19. The system of claim 14, wherein at least some of the primary and secondary wide area orbit satellites include attitude stabilization.

20. 20. The system of claim 19, wherein a plurality of the primary and secondary wide area orbit satellites include attitude stabilization means including electromagnets that are selectively energized to align the primary and secondary wide area orbit satellites with the Earth's magnetic field.

21. 14. The system of claim 13, wherein the antenna comprises a parabolic reflector, each of the parabolic reflectors including a plurality of feeds mounted about a periphery of the parabolic reflector, and wherein the antenna identifiers stored in the memory of the primary and secondary wide area orbit satellites include the identifiers of the antenna feeds of each of the primary and secondary wide area orbit satellites.

22. The system of claim 13 , wherein the system node further comprises at least one of an unmanned aerial vehicle, a balloon, and a geostationary satellite.

23. 14. The system of claim 13, wherein the plurality of wide area orbit satellites comprises multiple cohorts of satellites in orbits at different altitudes.

24. The system of claim 1 , wherein the plurality of orbiting satellite nodes are in stochastically distributed orbits.

25. The system of claim 13 , wherein the plurality of wide-area orbit satellites are in stochastically distributed orbits.

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