Dynamic power allocations for direct broadcasting satellite (DBS) channels via wavefront multiplexing
10149298 ยท 2018-12-04
Assignee
Inventors
Cpc classification
H04B10/2575
ELECTRICITY
H04W52/34
ELECTRICITY
International classification
H04L25/03
ELECTRICITY
H04W52/34
ELECTRICITY
Abstract
At a ground-based transmitting system, a first processor receives and performs an N-to-N wavefront-multiplexing (WFM) transform on N signals and outputs N WFM signals, N>1. The N WFM signals are orthogonal to one another and each of which is a unique linear combination of the N signals. The N-to-N WFM transform has a unique inverse. A transmit back-end transmits the N WFM signals over a transmission medium via propagation channels. At a user terminal, a receive front-end receives the N transmitted WFM signals and generates N received WFM signals. An equalizer generates N equalized signals from the N received WFM signals. A second processor performs the unique inverse of the N-to-N WFM transform on the N equalized signals and outputs N wavefront demultiplexed signals, each of which is a unique linear combination of the N equalized signals and is a recovered version of a respective one of the N signals.
Claims
1. A communication system comprising: a ground-based transmitting system comprising: a first processor comprising N first input ports and N first output ports, N being a positive integer greater than 1, for receiving concurrently N signals at the N first input ports, performing an N-to-N wavefront multiplexing transform on the N signals and outputting concurrently N wavefront multiplexed signals at the N first output ports such that the N wavefront multiplexed signals are orthogonal to one another and each of the N wavefront multiplexed signals is a unique linear combination of the N signals, the N-to-N wavefront multiplexing transform having a unique inverse; a transmit back-end coupled to the first processor, for frequency up-converting and amplifying the N wavefront multiplexed signals, generating and transmitting N up-converted amplified wavefront multiplexed signals over a transmission medium via propagation channels; and a user terminal comprising: a receive front-end for receiving and processing the N up-converted amplified wavefront multiplexed signals from the propagation channels, and generating N received wavefront multiplexed signals; an equalizer for equalizing the N received wavefront multiplexed signals by compensating for propagation channels effects, and generating N equalized signals; and a second processor comprising N second input ports and N second output ports, for receiving concurrently the N equalized signals at the N second input ports, performing the unique inverse of the N-to-N wavefront multiplexing transform on the N equalized signals and outputting concurrently N wavefront demultiplexed signals at the N second output ports such that each of the N wavefront demultiplexed signals is a unique linear combination of the N equalized signals and is a recovered version of a respective one of the N signals.
2. The communication system of claim 1, wherein the N-to-N wavefront multiplexing transform is a transformation using a Butler matrix, a Fourier transform, or a Hartley transform.
3. The communication system of claim 1, wherein the transmit back-end comprises: a set of frequency up-converters for frequency up-converting the N wavefront multiplexed signals; and a set of amplifiers for amplifying and frequency multiplexing the N frequency up-converted wavefront multiplexed signals and generating the N up-converted amplified wavefront multiplexed signals.
4. The communication system of claim 1, wherein the equalizer performs adaptive equalization to compensate for dynamic differential propagation effects due to the transmission medium and static differential propagation effects including unbalanced amplitudes, unbalanced phases, and unbalanced time-delays between the N received wavefront multiplexed signals and the N wavefront multiplexed signals.
5. The communication system of claim 1, wherein at least one of the N signals at the N first input ports is a known control signal or a known ground signal corresponding to at least one of the N wavefront demultiplexed signals that is outputted from a corresponding one of the N second output ports and that is used as an at least one diagnostic signal.
6. The communication system of claim 5, wherein the user terminal further comprises: an optimization system coupled to the second processor and the equalizer, for receiving the at least one diagnostic signal, performing optimization by computing complex weights to iteratively minimize a cost function that represents a measured difference between the at least one diagnostic signal and a corresponding signal at a corresponding one of the N first input ports, and providing the complex weights to the equalizer, the complex weights including amplitude, phase, and time-delay compensations to be used for adjusting amplitudes, phases and time-delays of the N received wavefront multiplexed signals.
7. The communication system of claim 6, wherein the optimization system comprises: a diagnostic circuit to generate values of the cost function; and an optimization processor to calculate the complex weights.
8. The communication system of claim 6, wherein the at least one diagnostic signal corresponds to the known ground signal at a corresponding one of the N first input ports, and wherein the cost function represents a detected total power level of the at least one diagnostic signal.
9. The communication system of claim 8, wherein the optimization system performs optimization such that the at least one diagnostic signal becomes approximately a ground signal.
10. The communication system of claim 6, wherein the equalizer comprises compensation circuits for using the complex weights to adjust amplitudes, phases and time-delays of the N received wavefront multiplexed signals.
11. A communication system comprising: a ground-based transmit system comprising: a first processor comprising N input ports and N output ports, N being a positive integer greater than 1, for receiving concurrently N signals at the N input ports, performing an N-to-N wavefront multiplexing transform on the N signals and outputting concurrently N wavefront multiplexed signals at the N output ports such that the N wavefront multiplexed signals are orthogonal to one another and each of the N wavefront multiplexed signals is a unique linear combination of the N signals, the N-to-N wavefront multiplexing transform having a unique inverse; and a transmit back-end coupled to the first processor, for frequency up-converting, amplifying and frequency division multiplexing the N wavefront multiplexed signals into at least one frequency multiplexed group signal, and transmitting the at least one frequency multiplexed group signal to satellite transponders of at least one satellite; and a user terminal comprising: a receive front-end for receiving and processing the at least one frequency multiplexed group signal from the satellite transponders, and generating N received wavefront multiplexed signals; an equalizer for equalizing the N received wavefront multiplexed signals by compensating for propagation channels effects, and generating N equalized signals; and a second processor comprising N second input ports and N second output ports, for receiving concurrently the N equalized signals at the N second input ports, performing the unique inverse of the N-to-N wavefront multiplexing transform on the N equalized signals and outputting concurrently N wavefront demultiplexed signals at the N second output ports such that each of the N wavefront demultiplexed signals is a unique linear combination of the N equalized signals and is a recovered version of a respective one of the N signals.
12. The communication system of claim 11, wherein the transmit back-end comprises: a set of N frequency-up-converters coupled to the N output ports, for frequency-up-converting the N wavefront multiplexed signals and generating N up-converted wavefront multiplexed signals; at least one frequency division multiplexer coupled to the set of frequency up-converters, for grouping the N up-converted wavefront multiplexed signals into at least one frequency multiplexed group signal for transmission to the satellite transponders of the at least one satellite; and a multi-beam antenna coupled to the at least one frequency division multiplexer, for radiating the at least one frequency multiplexed group signal toward the at least one satellite.
13. The communication system of claim 12, wherein the at least one satellite comprises more than one satellites, and wherein the at least one frequency division multiplexer comprises more than one frequency division multiplexers, each of the more than one frequency division multiplexers grouping the N up-converted wavefront multiplexed signals into a respective frequency multiplexed group signal for transmission to a respective satellite of the more than one satellites.
14. The communication system of claim 11, wherein the receive front-end comprises: a multi-beam antenna for receiving the at least one frequency multiplexed group signal from the satellite transponders of the at least one satellite; at least one frequency division demultiplexer coupled to the multi-beam antenna for separating the at least one frequency multiplexed group signal into N received signals that correspond to the N up-converted wavefront multiplexed signals; and a set of N frequency-down-converters coupled to the at least one frequency division demultiplexer, for down-converting the N received signals to a common frequency and generating the N received wavefront multiplexed signals.
15. The communication system of claim 14, wherein the at least one satellite comprises more than one satellites, each transmitting a respective frequency multiplexed group signal, and wherein the at least one frequency division demultiplexer comprises more than one frequency division demultiplexers, each of the more than one frequency division demultiplexers receiving and separating a respective frequency multiplexed group signal into respective received signals of the N received signals.
16. The communication system of claim 11, wherein at least one of the N signals at the N first input ports is a known control signal or a known ground signal corresponding to at least one of the N wavefront demultiplexed signals that is outputted from a corresponding one of the N second output ports and that is used as an at least one diagnostic signal.
17. The communication system of claim 16, wherein the user terminal further comprises: an optimization system coupled to the second processor and the equalizer, for receiving the at least one diagnostic signal, performing optimization by computing complex weights to iteratively minimize a cost function that represents a measured difference between the at least one diagnostic signal and a corresponding signal at a corresponding one of the N first input ports, and providing the complex weights to the equalizer, the complex weights including amplitude, phase, and time-delay compensations to be used for adjusting amplitudes, phases and time-delays of the N received wavefront multiplexed signals.
18. The communication system of claim 17, wherein the optimization system comprises: a diagnostic circuit to generate values of the cost function; and an optimization processor to calculate the complex weights.
19. The communication system of claim 17, wherein the at least one diagnostic signal corresponds to the known ground signal at a corresponding one of the N first input ports, and wherein the cost function represents a detected total power level of the at least one diagnostic signal.
20. The communication system of claim 11, wherein the N-to-N wavefront multiplexing transform is a transformation using a Butler matrix, a Fourier transform, or a Hartley transform.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) The objects, features and advantages of the present invention will become better
(2) understood from the following detailed descriptions of the preferred embodiment of the invention in conjunction with reference to the following appended claims, and accompanying drawings where:
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DETAILED DESCRIPTION
(14) The present invention relates to the fields of communications systems and computer networks and, in particular, to satellite networks, Direct-Broadcast-Service (DBS) broadcasting architectures, DBS uplink terminals, and DBS receive only subscriber ground terminals. More specifically, but without limitation thereto, the present invention pertains to a communication system and method that allows a transmitter segment (operator at uplink segment) to dynamically combine power from plurality of propagation channels (transponders) in order to improve power levels of signals being transmitted, without affecting the receiver segment (downlink segment) and the propagation segment (space segment), and without modifying the configuration of the propagation apparatus (satellite).
(15) The following description, taken in conjunction with the referenced drawings, is presented to enable one of ordinary skill in the art to make and use the invention and to incorporate it in the context of particular applications. Various modifications, as well as a variety of uses in different applications, will be readily apparent to those skilled in the art, and the general principles, defined herein, may be applied to a wide range of embodiments. Thus, the present invention is not intended to be limited to the embodiments presented, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. Furthermore, it should be noted that unless explicitly stated otherwise, the figures included herein are illustrated diagrammatically and without any specific scale, as they are provided as qualitative illustrations of the concept of the present invention.
(16) In order to provide a working frame of reference, first a glossary of some of the terms used in the description and claims is given as a central resource for the reader. The glossary is intended to provide the reader with a general understanding of various terms as they are used in this disclosure, and is not intended to limit the scope of these terms. Rather, the scope of the terms is intended to be construed with reference to this disclosure as a whole and with respect to the claims below. Next, an overview is presented to provide a general understanding of the scope and meaning of the terms used herein. Thereafter, the physical embodiments of the present invention are provided to enable the reader to understand the various manifestations of the present invention. Finally, a detailed description of the elements is provided in order to enable the reader to make and use the various embodiments of the invention without involving extensive experimentation.
(1) Glossary
(17) Before describing the specific details of the present invention, it is useful to provide a centralized location for various terms used herein and in the claims. A definition has been included for these various terms. However, the definition provided should not be considered limiting to the extent that the terms are known in the art. These definitions are provided to assist in teaching a general understanding of the present invention.
(18) Computer readable mediaThe term computer readable media, as used herein, denotes any media storage device that can interface with a computer and transfer data back and forth between the computer and the computer readable media. Some non-limiting examples of computer readable media include: an external computer connected to the system, an internet connection, a Compact Disk (CD), a Digital Versatile Disk/Digital Video Disk (DVD), a floppy disk, a magnetic tape, an internet web camera, a direct satellite link, a video cassette recorder (VCR), a removable hard drive, a digital camera, a video camera, a video cassette, an electronic email, a printer, a scanner, a fax, a solid-state recording media, a modem, a read only memory (ROM), and flash-type memories.
(19) De-MultiplexerThe term De-Multiplexer, as used herein, is a standard term used in the fields of electronics, telecommunications, signal processing, digital circuits design, and computer networks to denote a process or device that separates or splits a single input signal, that carries multiple individual signals within (such as multiple channels or telephone calls), into multiple output signals, such that the output signals from the de-multiplexer correspond to the individual signals carried by the single input signal. The aim of a de-multiplexer is to extract the original signals or channels on a receiver side of a transmission system. Generally, a de-multiplexer is often used on a receiver side of a communication system with a complementary multiplexer on the transmitting side of the communication system.
(20) DEMUXAn acronym for De-Multiplexer. The term DEMUX, as used herein, is a standard term used in the fields of electronics, telecommunications, signal processing, digital circuits design, and computer networks to denote a De-multiplexer which separates or splits a single input signal, that carries multiple individual signals within, into multiple output signals, such that the output signals from the De-multiplexer correspond to the individual signals carried by the single input signal.
(21) Direct-Broadcast-Service (DBS)The term Direct-Broadcast-Service, as used herein, is a standard term used in the field of satellite communications to denote a broadcasting service that delivers television programs over coverage areas, via dedicated broadcasting satellites in geostationary orbits, to small DBS satellite dishes (usually 18 to 24 inches or 45 to 60 cm in diameter) operating in the upper portion of the microwave Ku frequency band. DBS technology is typically used for direct-to-home (DTH) oriented satellite TV services, such as Direct TV? and DISH Network? in the United States of America.
(22) DBSAn acronym for Direct-Broadcast-Service. The term DBS, as used herein, is a standard term used in the field of satellite communications to denote a direct-broadcasting-service that delivers television programs over coverage areas, via dedicated broadcasting satellites in geostationary orbits, to small DBS satellite dishes (usually 18 to 24 inches or 45 to 60 cm in diameter) operating in the upper portion of the microwave Ku frequency band. DBS technology is typically used for direct-to-home (DTH) oriented satellite TV services.
(23) Fixed-Satellite-Service (FSS)The term Fixed-Satellite-Service, as used herein, is a standard term used in the field of satellite communications to denote a broadcasting service that uses the C frequency band and the lower portions of the Ku frequency band for transmission of broadcast feeds to and from television networks and local affiliate stations, as well as being for transmissions of distance learning by schools and universities, video-conferencing, and to distribute national cable channels to cable television head-ends. Fixed-satellite-service (FSS) operates at lower frequency and lower power than a direct broadcast service (DBS). The fixed-satellite-service requires a much larger dish for reception than DBS, such as 3 to 8 feet in diameter for Ku frequency band transmission and 12 feet in diameter for C frequency band transmission.
(24) FSSAn acronym for Fixed-Satellite-Service. The term FSS, as used herein, is a standard term used in the field of satellite communications to denote a fixed-satellite-service that uses the C frequency band and the lower portions of the Ku frequency band for satellite transmission of broadcast feeds to and from television networks and local affiliate stations.
(25) Geostationary Satellite OrbitThe term Geostationary Satellite Orbit, as used herein, is a standard term used in the field of satellite communications to denote a satellite orbit around the planet Earth with an altitude of approximately 35786 km (22240 miles), with an orbital period equal to approximately 24 hours (average rotation time of the Earth), and with an approximately zero orbital inclination in reference to the equatorial plane of the Earth. To an observer on the ground, a geostationary satellite will appear as a fixed point in the sky.
(26) Geosynchronous Satellite OrbitThe term Geosynchronous Satellite Orbit, as used herein, is a standard term used in the field of satellite communications to denote a satellite orbit around the planet Earth with an altitude of approximately 35786 km (22240 miles) and with an orbital period equal to approximately 24 hours (average rotation time of the Earth). A geosynchronous satellite has an orbit synchronized with the rotation of the planet Earth and a non-zero orbital inclination in reference to the equatorial plane of the Earth. To an observer on the ground, a geosynchronous satellite will appear to trace an analemma (depicted as a
(27) InputThe term input, as used herein, is used to denote any device used to receive input from a user or a system. Some non-limiting examples of input devices are: a keyboard, a microphone, a computer mouse, a wireless signal communication, a game engine, and an electronic writing device, wherein the electronic writing device permits a user to write notes and to draw doodles on a pad to be transferred to a computer by use of a special electronic ball point pen.
(28) Instruction meansThe term instruction means when used as a noun with respect to this invention generally indicates a set of operations to be performed on a computer, and may represent pieces of a whole program or individual, separable, software (or hardware) modules. Non-limiting examples of means include computer program code (source or object code) and hard-coded electronics. The means may be stored in the memory of a computer or on a computer readable medium. In some cases, however, the term means refers to a class of device used to perform an operation, and thus the applicant intends to encompass within this language any structure presently existing or developed in the future that performs the same operation.
(29) MultiplexerThe term Multiplexer, as used herein, is a standard term used in the fields of electronics, telecommunications, signal processing, digital circuits design, and computer networks to denote a process where multiple input signals, such as analog message signals or digital data streams, are combined into one output signal over a shared medium. The aim of a multiplexer is to share an expensive resource, such as a transponder channel or a wire, among multiple input signals. As an example, in telecommunications, several telephone calls (multiple input signals) may be transferred using one wire (single output signal). In contrast, an electronic multiplexer can be considered as a multiple input, single-output switch. The two most basic forms of multiplexing are time-division multiplexing (TDM) and frequency-division multiplexing (FDM), where FDM requires modulation of each signal. Generally, a multiplexer is often used on a transmitting side of a communication system with a complementary demultiplexer on the receiving side of the communication system.
(30) MUXAn acronym for Multiplexer. The term MUX, as used herein, is a standard term used in the fields of electronics, telecommunications, signal processing, digital circuits design, and computer networks to denote a Multiplexer that allows multiple input signals to be combined into one output signal over a shared medium.
(31) On-lineThe term on-line, as used herein, is a standard term used to denote under the control of a central computer, as in a manufacturing process or an experiment. On-line also means to be connected to a computer or computer network, or to be accessible via a computer or computer network.
(32) Operation of downloading, at the downlink segment, the transformed WFM signals transmitted from the satellite segmentThe term operation of downloading, at the downlink segment, the transformed WFM signals transmitted from the satellite segment, as used herein, is a standard term used to denote the process by which a signal (in this case a transformed WFM signal) is downloaded from the satellite and is received and processed at the downlink segment. The operation of downloading, at the downlink segment, the transformed WFM signals transmitted from the satellite segment comprises the operations of:
(33) receiving, at a user end of downlink segment, the frequency translated WFM signals from the transponders; and
(34) amplifying the received frequency translated WFM signals from the transponders.
(35) Operation of processing, at the downlink segment, the downloaded transformed WFM signals to a base-band frequency resulting in base-band frequency WFM signalsThe term operation of processing, at the downlink segment, the downloaded transformed WFM signals to a base-band frequency resulting in base-band frequency WFM signals, as used herein, is a standard term used to denote the process by which a signal (in this case a downloaded transformed WFM signal) is frequency down-converted from a satellite amplified frequency translated WFM signal to a common IF or base-band frequency, resulting in base-band frequency WFM signal.
(36) Operation of transforming a WFM signal to satellite frequency bandThe term operation of transforming a WFM signal to satellite frequency band, as used herein, is a standard term used to denote the process by which a signal (in this case a WFM signal) is up-converted, at the uplink segment, into a signal in the satellite frequency band. The operation of transforming the WFM signals to a satellite frequency band comprises the operations of:
(37) frequency up-converting the output wavefront multiplexed signals to distinct frequency carriers within frequency bands for satellite communications; amplifying frequency up-converted wavefront signals; and frequency multiplexing amplified wavefront signals by utilizing an output multiplexer at the satellite frequency band.
(38) Operation of transmitting, at the satellite segment, the transformed WFM signals to a downlink segmentThe term operation of transmitting, at the satellite segment, the transformed WFM signals to a downlink segment, as used herein, is a standard term used to denote the process by which a signal (in this case a transformed WFM signal) is transmitted through the satellite segment towards a downlink segment. The operation of transmitting, at the satellite segment, the transformed WFM signals to a downlink segment comprises the operations of:
(39) receiving in a satellite the transformed wavefront multiplexed signals; translating the carrier frequencies of the transformed wavefront multiplexed signals; and
(40) amplifying and transmitting the frequency translated wavefront multiplexed signals through the satellite transponders toward the user end of downlink segments, wherein each frequency translated wavefront multiplexed signal is amplified and transmitted through its own individual and independent transponder, whereby all designated transponders in the satellite are being utilized to transmit frequency translated wavefront multiplexed signals, thereby utilizing all available space assets of the satellite.
(41) Real-timeThe term real-time, as used herein, is a standard term used to relate to computer systems that update information, or perform a task, at the same rate as they receive data.
(42) Recording mediaThe term recording media, as used herein, denotes any media used to store information about an object or a scene. Some non-limiting examples of recording media are: a video film, a video recording tape, an audio recording tape, an audio cassette, a video cassette, a video home system (VHS) tape, an audio track, a Compact Disk (CD), a Digital Versatile Disk/Digital Video Disk (DVD), a floppy disk, a removable hard drive, a digital camera, a solid-state recording media, a printed picture, a scanned document, a magnetic tape, and a faxed document.
(43) UserThe term user, as used herein, denotes a person utilizing the method for automatically extracting geospatial features from multi-spectral imagery.
(44) Wavefront-MultiplexerThe term Wavefront-Multiplexer, as used herein, is not a standard term used in the fields of telecommunications, electronics, signal processing, digital circuits design, or computer networks. Instead, the term Wavefront-Multiplexer is used to denote a specialized signal processing transform based on a variation from the standard multiplexer known by one skilled in the art, whereas a multiplexer combines multiple inputs into a single output, the Wavefront-Multiplexer allows multiple inputs to be combined into multiple outputs, such that each output is comprised of a unique linear combination of all the inputs and such that the outputs from the Wavefront-Multiplexer are orthogonal to one another. The Wavefront-Multiplexer is a multiple-input/multiple-output (MIMO) transform that has at least as many outputs as there exist inputs connected to the wavefront-multiplexer. The Wavefront-Multiplexer performs an orthogonal functional transformation from a spatial-domain representation of the inputs to a wavefront-domain representation of the inputs, wherein a necessary and sufficient condition of the Wavefront-Multiplexer transform is that the Wavefront-Multiplexer transform has a realizable unique inverse.
(45) WFMAn acronym for Wavefront-Multiplexer. The term WFM, as used herein, is a non-standard term used to denote a wavefront-multiplexer, wherein the Wavefront-Multiplexer is a specialized signal processing transform based on a variation from the standard multiplexer, whereas a multiplexer combines multiple inputs into a single output, the Wavefront-Multiplexer allows multiple inputs to be combined into multiple outputs, such that each output is comprised of a unique linear combination of all the inputs and such that the outputs from the Wavefront-Multiplexer are orthogonal to one another.
(46) Wavefront-De-MultiplexerThe term Wavefront-De-Multiplexer, as used herein, is not a standard term used in the fields of telecommunications, electronics, signal processing, digital circuits design, or computer networks. Instead, the term wavefront-de-multiplexer is used to denote a specialized signal processing transform based on a variation from the standard de-multiplexer known by one skilled in the art, whereas a demultiplexer separates or splits a single input signal, that carries multiple individual signals within, into multiple output signals corresponding to the individual signals carried by the single input signal, the wavefront-de-multiplexer separates multiple inputs, that each carry a unique mixture of individual signals, into multiple outputs, such that each output corresponds to one of the individual signals carried by the multiple inputs. The wavefront-de-multiplexer is a multiple-input/multiple-output (MIMO) transform that performs an orthogonal functional transformation from a wavefront-domain representation of signals to a spatial-domain representation of signals. The wavefront-de-multiplexer is a complementary transform to the wavefront-multiplexer, wherein the wavefront-de-multiplexer is often used on a receiver side of a communication system with a complementary Wavefront-Multiplexer on the transmitting side of the communication system. The aim of a wavefront-de-multiplexer is to extract the original transmitted signals on a receiver side of a transmission system.
(47) WFDMAn acronym for Wavefront-De-Multiplexer. The term WFDM, as used herein, is a non-standard term used to denote a Wavefront-De-Multiplexer, wherein the wavefront-de-multiplexer is a specialized signal processing transform based on a variation from the standard de-multiplexer, whereas a de-multiplexer separates or splits a single input signal, that carries multiple individual signals within, into multiple output signals corresponding to the individual signals carried by the single input signal, the wavefront-de-multiplexer separates multiple inputs, that each carry a unique mixture of individual signals, into multiple outputs, such that each output corresponds to one of the individual signals carried by the multiple inputs.
(2) Overview
(48) In the following detailed description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. However, it will be apparent to one skilled in the art that the present invention may be practiced without necessarily being limited to these specific details. In other instances, well-known structures and devices are shown in block diagram form, rather than in detail, in order to avoid obscuring the present invention.
(49) Some portions of the detailed description are presented in terms of a sequence of events and symbolic representations of operations on data bits within an electronic memory. These sequential descriptions and representations are the means used by artisans to most effectively convey the substance of their work to other artisans. The sequential steps and operations are generally those requiring physical manipulations of physical quantities. Usually, though not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated. It has proven convenient at times, principally for reasons of common usage, to refer to these signals by terms such as bits, pixels, values, data, video frames, audio signals, elements, files, digital signal streams, and coefficients.
(50) It is to be understood, that all of these, and similar terms, are to be associated with the appropriate physical quantities, and are merely convenient labels applied to these quantities. Unless specifically stated otherwise as apparent from the following discussions, it is appreciated that throughout the present disclosure, discussions utilizing terms such as acquiring, amplifying, augmenting, calculating, communicating, controlling, converting, determining, displaying downloading, extracting, inputting, interacting, interfacing, mapping, matching, modeling, obtaining, outputting, performing, processing, receiving, recognizing, recovering, separating, tracking, transforming, transmitting, translating, or uploading, refer to the action and processes of a computer system, or similar electronic device that manipulates and transforms data represented as physical (electronic) quantities within the system's registers and memories into other data similarly represented as physical quantities within the computer system memories or registers or other such information storage, transmission, or display devices. Furthermore, the processes presented herein are not inherently related to any particular processor, processor component, computer, software, or other apparatus.
(3) Physical Embodiments of the Present Invention
(51) The present invention has two principal physical embodiments. The first is a system for dynamically combining power from a plurality of propagation channels (transponders) in order to improve power levels of transmitted signals. In doing so, the dynamic power allocation is implemented through the transmitter segment (ground end of uplink segment) without affecting the receiver segment (user end of downlink segment) and the propagation segment (space segment), and without modifying configuration of propagation apparatus and propagation channels (satellite and transponders in the space segment). Such a system is typically but not limited to a computer system operating software in the form of a hard coded instruction set.
(52) This system may also be specially constructed, as an application-specific integrated circuit (ASIC), or as a readily reconfigurable device such as a field-programmable gate array (FPGA).
(53) The second physical embodiment is a method, typically in the form of software, operated using a data processing system (computer).
(54) A block diagram depicting the components of a computer system used in the present invention is provided in
(4) Detailed Description of the Elements
I) Embodiment of the Invention for a Dynamic Communication System
(55) A detailed description of an embodiment of the present invention is presented schematically in a diagram in
(56) Next, the system receives, at the receiver segment 204, the transmitted WFM signals 216 from the propagation channels 214, where the terms WFM.sup.A1, WFM.sup.A2, WFM.sup.A3, and WFM.sup.A4 in
(57) Once the propagation channel effects from the propagation segment have been reversed by the adaptive equalizer 218, the system separates the equalized WFM signals 220 into individual spatial-domain signals 206 by performing a Wavefront-De-Multiplexing transform 222 (WFDM transform), where the terms A1, A2, A3, and A4 in
(58) During the adaptive equalization process 218 performed at the receiver segment 204, this embodiment of the invention connects a control signal 224 to a WFM input port denoted by the term A1. This WFM input port connected to a control signal 224 at the transmitter segment 200 has a corresponding WFDM controlled output port 226 at the receiver segment 204. The WFDM controlled output port 226 is used as a diagnostic port where a cost function is used to measure the difference between the controlled input port 224 and its corresponding diagnostic port 226. Then, the system uses an optimization processor and several compensation processors 228 (such as amplitude, phase, and time-delay compensation processors) to generate compensation signals 230 that compensate for the propagation channel effects from the propagation segment 202 and which are used to adjust the adaptive equalizer 218 in order to minimize the cost function. Adaptive equalization is reached when the cost function is minimal and the cost function can no longer be reduced any further.
(59) An embodiment of the invention utilizes two separated areas of technology to equivalently achieve power combining and providing better throughput and availability of broadcasted signals to DBS ground subscribers. These two technological areas are: wave-front multiplexing and adaptive equalization, and compensation among multiple signal paths.
II) Wavefront Multiplexing
(60) A detailed description of Wavefront-Multiplexing is presented. A Wavefront-Multiplexer or Wavefront Multiplexing is a specialized signal processing transform based on a variation from the standard multiplexer known by one skilled in the art. Whereas a standard multiplexer combines multiple inputs into a single output, the Wavefront-Multiplexer allows multiple inputs to be combined into multiple outputs, such that each output is comprised of a unique linear combination of all the inputs and such that the outputs from the Wavefront-Multiplexer are orthogonal to one another. Therefore, the Wavefront-Multiplexer (WFM) is a multiple-input/multiple-output (MIMO) transform that has at least as many outputs as there exist inputs connected to the wavefront-multiplexer. The Wavefront-Multiplexer performs an orthogonal functional transformation from a spatial-domain representation of the inputs (such as the terms A1, A2, A3, and A4 in
(61) A complementary transform to the Wavefront-Multiplexer is the Wavefront-De-Multiplexer. The Wavefront-De-Multiplexer is often used on a receiver side of a communication system with a complementary Wavefront-Multiplexer on the transmitting side of the communication system. The aim of a Wavefront-De-Multiplexer is to extract the original transmitted signals on a receiver side of a transmission system. Generally, Wavefront-De-Multiplexer is used to denote a specialized signal processing transform based on a variation from the standard De-Multiplexer known by one skilled in the art. Whereas a De-Multiplexer separates or splits a single input signal that carries multiple individual signals within into multiple output signals corresponding to the individual signals carried by the single input signal, the Wavefront-De-Multiplexer separates multiple inputs, that each carry a unique mixture of individual signals, into multiple outputs, such that each output corresponds to one of the individual signals carried by the multiple inputs. The Wavefront-De-Multiplexer is a multiple-input/multiple-output (MIMO) transform that performs an orthogonal functional transformation from a wavefront-domain representation of signals to a spatial-domain representation of signals.
(62) For illustrative purposes, the concepts of Wavefront Multiplexing and Wavefront De-Multiplexing are graphically illustrated in
(63) In order to graphically visualize the functionality of these wavefront transforms, the two lenses representing the Wavefront Multiplexing (WFM)/De-Multiplexing (WFDM) pair are connected by eight identical optical fibers 308 that act as propagation channels. On one end, the eight optical fibers are connected evenly distributed on the circular surface of the right edge 302a of the left lens corresponding to the WFDM lens (elements 300a and 302a). On the other end, the eight optical fibers are connected evenly distributed on the circular surface of the left edge 300b of the right lens corresponding to the WFM lens
(64) (Elements 300b and 302b).
(65) The functionality of the WFDM is illustrated as follows: Two signal sources denoted by 310 (source A) and 312 (source B) are connected to the inputs of the right lens 300a of the WFDM, where the source A 310 is above the center of the circular surface of the opposite edge of the lens 302a and source B 312 is below the center of the circular surface of the opposite edge of the lens 302a. Source B 312, as shown, generates a circular wavefront centered at the B port 314 (the circular wavefront 314 is similar to concentric circles or waves generated by throwing a pebble into a peaceful lake). The circular wavefront 314 originated by the source B 312 is picked up by the eight optical fibers 308, which are connected and evenly distributed on the circular surface of the right edge 302a of the left lens (WFDM). However, the optical fibers do not pick up the circular wavefront at the same time, but each optical fiber receives the wavefront in a sequential manner (after some time delay). As such, the input for optical fiber number 8 senses the wavefront first while the input for the optical fiber number 1 receives the wavefront the last. In a similar manner, the circular wavefronts generated by source A 310 will be sensed by the optical fibers on a reverse sequence order, such that fiber number 1 will sense the wavefront generated from source A 310 first, while fiber number 8 will be the last fiber to sense the wavefront from source A 310. As a result, there are two different and simultaneous wavefronts propagating through the eight fibers at the same time but at different time delays and off phase from each other, one from source A 310 and the other from source B 312. Therefore, the wavefront 314 generated by source B 312 is traveling through each one of the eight fibers at different moments in time along with the wavefront generated by source A 310, such that both wavefronts are intermixed with each other through time delays and phase delays within each optical fiber, and such that there are eight different representations of each wavefront generated by a source traveling through the fibers at any point in time (similar in nature to a standard De-Multiplexer).
(66) The functionality of the WFM, denoted by the lens on the right (300b and 302b) in
(67) When the fibers in the bundle are identical, with equal amplitude attenuations and equal propagation delays through all the eight fibers (i.e., no propagation channel effects), the source A 310 will be transported to sink A 310A while source B 312 will be transported to sink B 312A. However, usually the fibers in the bundle will not be identical in amplitude attenuations and propagation delays through out all eight fibers due to environment changes or aging, thus creating disparate propagation effects. As a result, the source A 310 will not only be transported to sink A 310A but also with leakage into sink B 312A. In a similar manner, source B 312 will not only be delivered to the intended destination of sink B 312.sup.A. but also to the unintended destination of sink A 310A.
(68) Therefore, in order to be able to recuperate the original signals being transmitted over the optical fibers (propagation channels), adaptive channel equalization must be performed prior to separating the intermixed wavefront multiplexed signals in the fibers (propagation channels) in order to eliminate the propagation channel effects from the optical fibers and to avoid leakage from one signal into the sink of the other signal.
(69) Reversing the flow of the signals in
(70) Mathematically, the Wavefront Multiplexing and De-Multiplexer operation is an orthogonal functional manipulation or transformation, and it may be implemented many ways. The transformation is not in between the time and frequency domains, but is an orthogonal transformation between the spatial domain and the wave-front domain.
(71) The Wavefront Multiplexing transformation is expressed by a linear equation as follows:
Y=WFM*X,(1)
(72) where
(73) X denotes the input vectors,
(74) Y denotes the output vector, and
(75) WFM denotes the functional transformation matrix.
(76) In addition, the wavefront transformation features the characteristic that the WFT is orthogonal to itself, such that
WFM*WFM=I(2)
(77) A non-limiting example of an orthogonal transformation matrix used to implement an embodiment of the Wavefront Multiplexing transform is presented below. This non-limiting example of a WFM transform is implemented by an analogue 4-to-4 Butler Matrix (BM) at the Ku band. Two examples of the vector weightings 400a, 400b, by phase rotation only, are illustrated in
(78) [W11, W12, W13, W14]=[exp(jOH), exp(j012), exp(j013), exp(j014)],
(79) [W21, W22, W23, W24]=[exp(j021), exp(j022), exp(j023), exp(j024)],
(80) [W31, W32, W33, W34]=[exp(j031), exp(j032), exp(j033), exp(j034)],
(81) [W41, W42, W43, W44]=[exp(j041), exp(j042), exp(j043), exp(j044)],
(82) Since the WFM operation, WFM, is a linear operation, it may be implemented as 8?2-to-8?2 or 2?2-to-2?2 BMs at baseband. In addition to implementing a WFM transform using a Butler Matrix, a plurality of specific WFM matrices can be generated using Fourier transform pairs or Hartley transform pairs when working in the digital domain.
III) Embodiment of the Invention for Satellite Communications
(83) Another embodiment of the invention (using WFM techniques) can be used for satellite communications, including DBS applications, in order to allow N individual signal streams from a given uplink ground station (transmitter segment) to go through M independent transponders (or propagation channels) on a satellite (propagation apparatus). Then, the receiving downlink ground stations or subscriber terminals (receiver segment) can recover the individual signal streams faithfully by using Wavefront De-Multiplexing (WFDM) and additional signal processing processes, such adaptive equalization to remove propagation channel effects, under the constraint that there exist at least as many number of transponders, M, as there exist individual signal streams, N, being transmitted. One of the many possible applications of this WFM technique is the effective power combining, or Equivalent Isotropic Radiated Power (EIRP) combining, from various transponders in the same satellite or from various transponders in different satellites. The power combining corresponds to a dynamic power allocation implemented through the uplink station (transmitter segment) without affecting the receiving ground stations (receiver segment) and without affecting the satellite configuration (propagation segment).
(84) As a result of WFM as previously illustrated in
(85)
(86)
(87) III-i) Conventional DBS Satellite System
(88) In this particular conventional DBS system 500, there are four satellite transponders 504a available to transmit signals via a satellite. As such, the ground uplink segment 502a is capable of transmitting four input signals 516a (denoted by the terms d1, d2, d3, and d4) simultaneously to the four available satellite transponders. However, in this particular example, there are only two input streams of digital signals, represented by term S7 (denoted by element 512) and by term S8 (denoted by element 514), to be broadcasted via the DBS system 500 to various users 506a. Therefore, two of the inputs 516a of the ground uplink segment (referring to terms d3 and d4) are empty (not connected to input signals) or connected to ground signals 518a or zero value signals (for illustration purposes). Additionally, the other two inputs 516a of the ground uplink segment (referring to terms d1 and d2) are connected to the two input signal streams being broadcasted, where input signal stream 512 (term S7) is connected to uplink segment input d1 and input signal stream 514 (term S8) is connected to uplink segment input d2, respectively.
(89) The two input digital streams, 512 and 514, at the uplink station 502a, are transformed to a satellite frequency band by performing the operations of: frequency up-converting 520a the input digital streams, 512 and 514, to two different carrier frequencies within the Ku satellite frequency band; and amplifying and frequency multiplexing 524a the two frequency up-converted input signals 522a by utilizing an output multiplexer at the Ku satellite frequency band. Next, the two transformed Ku band signals 526a are uploaded to the Ku broadcasting satellite via an uplink ground antenna in an uploading facility.
(90) On the satellite, the received Ku band signals 526a go through two separated satellite transponders 504a, individually and independently, before they are ready for broadcasting to various subscriber terminals 506a. The current conventional DBS satellite systems, such as 500, only need two of the available satellite transponders to broadcast the two input digital streams, 512 and 514, and thus under utilize the rest of the available space assets, as shown. Therefore, the conventional DBS satellite system 500 only occupies 50% of the available space assets and 50% of the space assets are wasted (referring to the two unused satellite transponders that are available for broadcasting but that are not being utilized during the broadcast by the current conventional DBS satellite systems).
(91) At the subscriber terminals 506a, the proper transponder channels are selected, the desired signals are amplified, filtered, synchronized and de-modulated to recover the intended digital data streams 528a and 530a (denoted by terms ST and S8, respectively) for further processing prior to providing the processed signals to TV displays.
(92) III-ii) Embodiment of Invention for a Dynamic DBS Satellite System Using WFM Transformation
(93) In contrast with the current conventional DBS satellite systems, this embodiment of the invention for a dynamic DBS satellite system, in the bottom panel 508 of
(94) Similarly to the conventional DBS satellite system 500, this WFM DBS satellite system 508 has four satellite transponders 504b available to transmit signals via a satellite. As such, the ground uplink segment 502b is capable of transmitting four input signals 516b (denoted by the terms d1A, d2.sup.A d3A, and d4A) simultaneously to the four available satellite transponders. Equally to the conventional DBS satellite system, there are only two input streams of digital signals at the ground uplink segment 502b, represented by term S7 (denoted by element 512) and by term S8 (denoted by element 514), to be broadcasted via the WFM DBS satellite system 508 to various subscriber terminals 506b (users or receiver segments). Therefore, two of the inputs, 518b and 519b, to the WFM transform 510 at the ground uplink segment 502b of the invention, are empty (not connected to input signals) or connected to ground signals or zero value signals (for illustration purposes), and the other two inputs of the WFM transform 510 are connected to the two input signal streams being broadcasted, 512 (term S7) and 514 (term S8), respectively.
(95) In contrast with current DBS satellite systems, this embodiment of the invention transforms the two input digital streams, 512 and 514, at the uplink station 502b, into four simultaneous WFM digital streams 516b (denoted by terms d1.sup.A d2A, d3.sup.A and d4A) by performing wavefront multiplexing, prior to frequency up-converting the input signals to four different carrier frequencies in the Ku frequency band. Next, the four WFM digital streams 516b (denoted by terms d1.sup.A d2.sup.A d3A, and d4A), at the uplink station 502b, are transformed to a satellite frequency band by performing the operations of: frequency up-converting 520b the four WFM digital streams 516b, to four different carrier frequencies within the Ku satellite frequency band; and amplifying and frequency multiplexing 524b the four frequency up-converted WFM signals 522a by utilizing an output multiplexer at the Ku satellite frequency band. Next, the four transformed Ku band WFM signals 526b are uploaded to the Ku broadcasting satellite via an uplink ground antenna in an uploading facility.
(96) In this embodiment, the wavefront multiplexer (WFM) can be implemented at digital base-band in digital format, or by analogue devices such as a Butler matrix. Each of the four outputs 516b from the WFM (denoted by terms d1.sup.A d2A, d3.sup.A and d4A), is a linear combination of both input signals 512 and 514, and each WFM output features a different combination of the input signals than the combinations stored on the other WFM outputs. Furthermore, the four WFM outputs are orthogonal to one another.
(97) On the satellite, the received Ku band WFM signals 526b go through the four separated satellite transponders 504b, individually and independently, before they are ready for broadcasting to various subscriber terminals 506b. The WFM DBS satellite system 508 uses all of the available satellite transponders (uses all four transponders) to broadcast the two input digital streams, 512 and 514 and, therefore, utilize 100% of the available space assets. This is to be contrasted with the conventional DBS satellite system 500 which only occupies 50% of the available space assets (only uses two transponders for transmission).
(98) At the subscriber terminals 506b, the four received wave-front multiplexed signals 532 at the four separated carrier frequencies are amplified before being frequency down converted to a common IF or base-band. Next, the four down converted signals 534 are processed through a 4-to-4 wavefront de-multiplexer (WFDM) 536 to recover the desired signals, which are amplified, filtered, synchronized and de-modulated to restore the intended digital data streams 528b and 530b (denoted by terms ST and S8, respectively) for further processing prior to providing the processed signals to TV displays.
(99) In order to restore the original digital input data streams 512 and 514 (denoted by terms S7 and S8), the amplitude, time-delays, and the phase-delays of the WFM transmitted signals 516b must be kept constant among the four paths connecting the four outputs of the WFM 516b at the upload station 502b and the four inputs 534 of the WFDM 536 of a subscriber's terminal 506b. This constraint must be included in any embodiment of the present invention since this is a necessary and sufficient condition to make the WFM DBS satellite system work.
(100) Furthermore, this embodiment of the invention utilizes the information derived from the WFDM at a user or subscriber's terminal together with a unique optimization processes to adaptively equalize the four paths individually (between WFM signals 516b and WFDM input signals 534), at each of the subscriber's terminals. The adaptive equalization compensates for path length of phase, time, and amplitude differences among various transponders and propagation effects. The channel compensations are two folds: compensation for static difference of unbalanced amplitudes, unbalanced phases, and unbalanced time-delays among the four transponders, and static propagation effects due to the transmission medium; and compensation for dynamic differential propagation effects due to the transmission medium, such as rain precipitation among the four paths (propagation channels).
(101) In a similar manner as the embodiment illustrated in
(102) On the satellite, the received Ku band WFM signals 626 go through the four separated satellite transponders 604, individually and independently, before they are ready for broadcasting to various subscriber terminals 606, thus utilizing 100% of the available space assets. At the subscriber terminals 606, the four received wave-front multiplexed signals 632 at the four separated carrier frequencies are amplified before being frequency down converted to a common IF or base-band. Next, the four down converted signals 634 are processed through an adaptive equalizer 638 that compensates for unbalances on amplitude, phase, and time-delays. Then the equalized signals 640 are feed to a 4-to-4 wavefront de-multiplexer (WFDM) 636 in order to recover the desired digital data streams 628 and 630 (denoted by terms ST and S8, respectively).
(103) At the ground uplink station 602, as a part of the adaptive equalization 638, some of the inputs of the wave-front multiplexer are grounded (specifically the WFM inputs, 618 and 619, which are not connected to a signal to be transmitted). As a result, the outputs, 642 and 644, of the WFDM 640 in the user terminal 606 which correspond to the grounded inputs to the WFM, are connected to the optimization processor 600 to be used for diagnostic in the optimization loop. When adaptive equalization is reached for all the amplitude, phase, and time-delays, at the equalized state, there are no signals detected at any of the diagnostic ports, which for this particular embodiment correspond to the WFDM outputs 642 and 644.
(104) On the other hand, before the four paths are equalized, there are signals leaking into the diagnostic ports corresponding to the WFDM outputs 642 and 644. Therefore, the output powers from the diagnostic ports (referring to the WFDM outputs 642 and 644) are used as an indication of error or as a cost function. In an embodiment of the invention, the sum of the detected power levels from all the diagnostic paths are used as the system cost function in an equalization loop. As an optimization loop gradually and adaptively equalizes the four propagation paths, the error or the cost is continuously reduced.
(105) An embodiment of the optimization scheme using WFM for cost function measurement utilizes the following three parts for the equalization mechanisms: 1. diagnostic circuit, which generates the values of the cost function; 2. optimization processor (algorithm), which will calculate the complex weights iteratively minimizing the values of cost functions; and 3. compensation circuits, which implement the complex weighting used to modify and adjust the amplitudes, phases, and time-shifts of the WFM signals received at the subscriber terminals.
(106) The diagnostic circuit takes advantage of the nature of WFM and WFDM, utilizing the I/O ports to generate the cost function such that the when the paths are fully equalized the cost will become zero. The cost is a positive definite function, and can be defined in an ad hoc fashion (case-by-case), but usually it is defined such that when the M paths (M transponders or channels) are far away from being equalized, the cost is large, and when the M paths (M propagation channels) are nearly equalized, then the cost becomes small.
(107) The optimization processor (algorithm) will dynamically measure the gradient of the cost functions, and it calculates the updated amplitude, phase, and time-shift compensations (i.e., the complex weights) for all the paths accordingly. The optimization processor will iteratively compensate the path differences of the propagation channels, reducing the cost until the cost falls below a desired threshold.
(108) The compensation circuits are the real implementation of the amplitude, phase, and time-shift changes on the M signal paths. The compensation circuits can be implemented as a plurality of sets of phase shifters, time shifters, and amplitude attenuations, or I/Q with attenuations, in RF/IF analogue circuits. The compensation circuits may also be implemented in digital domain as a part of digital beam forming (DBF) process.
(109) In another embodiment of the invention, at least one output from the WFDM is used for observables measuring the error introduced by the differential drifts among the satellite-channels due to different dynamic propagation effects. Then, the received power levels, in the diagnostic port, are used to derive the components of a cost function, which is measurable to calculate the dynamic compensation weight vector (CWV) for propagation effects. In this embodiment, the control input signal does not have to be a ground (zero value) signal.
(110) In addition, when there exist as many input signals to be transmitted as there exits available transponders in a satellite, a control input signal (to be used for the adaptive equalization) can be multiplexed together with one of the input signals into one of the WFM inputs. In yet another embodiment of the invention, for slow varying environments, it is possible to feed back the observable information from the WFDM to the uplink station for pre-compensation of the multi-satellite differential propagation effects.
(111) III-iii) Example of Power Combining Aspect of the Invention
(112) An advantage of this invention is an embodiment that involves a dynamic improvement of radiated power over coverage areas by utilizing additional transponders on a satellite or from different satellites that are not being utilized at their full capacity and that have excessive (unused) radiated power available to be utilized, where the effective dynamic power allocations are utilized and implemented through the ground segment (transmitter segment or uplink segment) only, without affecting the space segment (propagation segment) configuration. For this dynamic power allocation to be successful, the receiving-only terminals must coherently combine the radiated power from the various transponders, which is effectively accomplished by the optimization loop comprised of the adaptive equalizer 638, the WFDM 636, and the optimization processor 600.
(113) In this embodiment, an operator, at a ground end of uplink segment 602 or at a program aggregation facility for a DBS service, dynamically allocates equivalent transponder powers 604 according to continuously changing market demands by dynamically including change of relative input powers into ratios of mixtures of the input digital signal streams, in order to improve radiated power of the input digital signal streams being broadcasted without affecting the user end of downlink segment 606 and the space segment, and without modifying satellite configuration.
(114) In general, the input intensity of the input signals streams (from the uplink station) are used to tap the output power of the various transponders from different satellites. The intensities of the input signal streams can be dynamically varied and they do not have to be equal. The following non-limiting example serves as an illustration of a power combining embodiment of the invention. This example assumes, for simplicity, that the transponders are operated in a linear mode with an equal ERIP (radiated power) of 45 decibel watts (dBw), and with a single carrier per stream in each transponder.
(115) This non-limiting example uses five input signal streams (A, B, C, D, and E), and eight independent transponders. At time T0 all five input streams exhibit equal power 702, as illustrated in
(116) The dynamic allocations of equivalent transponder powers according to the market demand are done usually by an operator or user through the uplink station transmission or program aggregation facility for a DBS service. The power allocation variations may be hourly, or in minutes, or in seconds, depending on the market demand and the number of transponders available. It is the decision of the owners of the DBS service to make the change and allocate the equivalent powers to the transponders. The mechanisms by which the transponder powers are allocated are the ratios of the mixtures of the input signal streams. At an extreme, an operator may turn off some of the input signal streams in favor of allocating more power to the remaining streams and assigning them with higher EIRPs from all the participating satellites.
(117) III-iv) Embodiment of WFM DBS Satellite System Utilizing Multiple Satellites
(118) In another embodiment of the invention, the WFM DBS power combining scheme can be implemented to include transponder assets in multiple satellites at various orbital slots. In this embodiment, the ground uplink stations, or gateway, access multiple satellites via multiple beam antennas or multiple antennas, each pointed to a corresponding satellite. Then, the subscriber terminals cost effectively access the designated multiple satellites via multiple beam antennas. Analog techniques can be used to implement effectively a system to combine transponder powers of say eight individual transponders from two or three satellites and divide the total power into multiple (<8) transponders. Furthermore, implementation using digital baseband approach can be very effective in cases when there are more carriers in a single transponder and the total transponder numbers are greater than 8 (such as 16 or 32).
(119) III-v) Embodiment of Multiple Satellites Backchannel Calibration Using WFM
(120) In still another embodiment of the invention, the WFM and WFDM can be used to perform back channel calibrations on mobile satellite communications with ground-based beam forming features (GBBF). This type of satellite usually employs a large antenna reflector (greater than 10 meters and less than 30 meters) at L- or S-bands, and has hundreds of fully configurable transmit and receive beams, which are essential for delivering services to small mobile and portable devices. With beam forming performed on the ground uplink segment using WFM and WFDM, the cost and time to deliver a highly flexible satellite are significantly reduced, since there are less than 100 feeds on board a satellite associated with the large reflector and there is no beam forming mechanism on board.
(121) This embodiment of the invention combines the equalized amplitudes, equalized phases, and equalized time-delays in the equalized WFM signals with associated optimization techniques in order to perform back channel calibration on mobile satellite communications with ground based beam forming features (GBBF). For receive (Rx) functions the signals captured by the feeds are transported to the ground facility for further processing including beam forming. Similarly for transmit (Tx) function, the ground facility will calculate the signals for various feeds based on the multiple beam information.
(122) III-vi) WFM DBS Satellite System Design Example
(123)
(124) A. 10 Transponders 9 high medium power transponders with 50 dBW EIRP, 1 low power transponder with 47 dBW EIRP; all with 36 MHz Bandwidth A RF front-end has an optional frequency up-converter, a BPF at RF, and an SSPA.
(125) B. 7 Transponders 4 high medium power transponders with 53 dBW EIRP, 1 high medium power transponders with 50 dBW EIRP, 1 low power transponder with 47 dBW EIRP; all with 36 MHz Bandwidth
(126) C. Dynamically Allocating the Resources Equivalent of 7 Transponders to 19 Transponders as Demands Arise
(127) The reader's attention is directed to all papers and documents which are filed concurrently with this specification and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference. All the features disclosed in this specification, (including any accompanying claims, abstract, and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.
(128) Furthermore, any element in a claim that does not explicitly state means for performing a specified function, or step for performing a specific function, is not to be interpreted as a means or step clause as specified in 35 U.S.C. Section 112, Paragraph 6.
(129)
(130) There are three segments in the illustration, a ground segment 930, a satellite segment 920, and a user segment 910. The return links are referred to signal transmissions initiated by the user segment 910, transponded (amplified and frequency translated) by the satellite segment 920, and received by the ground segment 930. The satellite segment 920 must feature space assets capable of covering service areas in which users in the user segment 910 residing, and areas where communications hubs in the ground segment 930 are located. The return link signals transmitted by a ground user from the user segment 910 are low-noise amplified, frequency-translated, and then power-amplified by different transponders in various satellites in the satellite segment 920 and coherently combined by a hub terminal in the ground segment 930. As a result, the received signals-to-noise-ratio (SNR) of the return link signals before a demodulator in the hub terminal of the ground segment 930 is enhanced accordingly.
(131) For a user terminal in the user segment 910, an input signal stream S(t) is decomposed into M substreams, Sx(t), where M is integer and M>1. The inputs of an N-to-N WF muxer 911 consist of M signal ports and N-M probe signal ports, where N>M and N is an integer. The N outputs features the following characteristics 1. Each of the N outputs is a unique linear combinations of all N inputs including M signal streams and N-M probing signals streams; a. The weighting coefficients among various input signals in each of the N outputs are independent 2. Each of the N inputs appears in all N outputs: a. The weighting coefficients on an input over the N-linear combinations feature unique distribution; the unique distribution of the weighting coefficients are the constituting components of a WF vector associated to the input port. b. Various input ports will associate different WF vectors among the N-outputs; c. The N WF vectors associated with the N-to-N WF muxer are mutually orthogonal to one another in an N-dimensional space in which each of the N-output port representing one of the N-dimensions.
(132) The N aggregated outputs from the WF muxer 911 are individually frequency up-converted by an array of frequency up-converters 912, and grouped by frequency-division-multiplex (FDM) muxers 913 for two different satellites 921 and 922 in the satellite segment 920. Group 1 and group 2 of muxed signals, Y1(t) and Y2(t) respectively, feature N1 and N2 aggregated channels, where N1+N2=N and N1, N2 are positive integers. These two groups of muxed signals Y1(t) and Y2(t) are amplified by power amplifiers and then radiated independently by a multi-beam antenna (MBA) 914 aiming for the two designated satellites 921 and 922 separately in the satellite segment 920.
(133) For the satellite segment 920, the two satellites 921 and 922 independently receive, transpond (or equivalent), and re-radiate the N1 and N2 channels of aggregated signals respectively toward a hub terminal. As a result, the two groups of aggregated signals in various channels when arriving at the hub terminal will experience different time delays, drifts in frequencies and phases, and amplitude attenuations/amplifications. It is important to note that: 1. Each of the M Sx(t) is replicated N times and appears in all N1 channels utilized in the first satellite 921, and concurrently in all N2 channels utilized in the second satellite 922. 2. Each of the N-M probing signal streams is replicated N times and appears in the same N1 utilized channels of the first satellite 921, and concurrently in the same N2 utilized channels of the second satellite 922.
(134) For the ground segment 930, a hub terminal features a multi-beam antenna 934, input FDM demuxers (I-Muxers) 933, a bank of frequency down converters 932, an N-to-N WF demuxer 931, and an associated adaptive equalizer circuitry 931a. The adaptive equalizers 931a driven by an optimization processor 935 utilizing recovered probing signals at the outputs of N-to-N WF demuxer 931 to iteratively and dynamically compensate for the differentials of amplitudes, drifts in frequencies and phases, and time delays incurred while these wavefronts (WF's) pass though the N1 and N2 propagation channels.
(135) The hub terminal in the ground segment for the return link traffic features low noise amplifiers (LNAs) and band pass filters (BPFs) to condition (amplify and properly filter) received signals from at least the two satellites. The LNAs and BPFs are not depicted. The two FDM demuxers 933 separate, respectively, the N1 channels of the received signals from the first satellite and N2 channels of the received signals from the second satellite. The frequency converters 932 convert the FDM demuxed N channel signals to a common frequency, and the adaptive equalizer 931a to iteratively equalize N receiving channels by altering its compensation weighting vector (CWV).
(136) The N-to-N WF demuxer 931 will perform WF demuxing transform on the N (N1+N2) channels of the return link signals to recover M channels of signals, and N-M channels of probing signals, which are utilized to equalize the N-propagation channels. At fully equalized conditions, the N WF vectors will become orthogonal again. Since the probing signals are known a priori, the differences of the recovered probing signals and those of anticipated versions will be used for propagation paths. Zero signals can be used as probing signals, and are ones of possible versions for probing signals.
(137) An optimization loop to optimize the CWV of the equalizer 931a iteratively features 1. a cost function generator (not shown) to map outputs from the N-M channels of recovered diagnostic/probing signals of the N-to-N WF demuxer 931 into cost functions as performance indexes by a cost function generator; whereas the performance indexes must be positive. 2. Cost functions can be generated by measuring the leakage signal power among the probing signals. 3. Cost functions may also be generated from measurements of correlations among the N-outputs of the N-to-N WF muxer 931; especially among the output signals from the signals ports to those from the probing signal ports 4. an optimization processor 935 to sum all the positively defined cost functions as a total cost; reflecting the current status of the optimization process; whereas high total cost indicating poor performance status, low total cost good performance status, and zero total cost representing perfect optimization status; 5. an optimization processor 935 measures the gradients of the current total cost with respect to the CWV weighting, derives a new CWV for next update based on a cost minimization algorithm and then sends the new CWV to the equalizer 931a for updating in next iteration.
(138) At steady states, the M recovered outputs of Sx(t) will be reassembled to constitute a higher data rate received signal stream, S(t) (not shown).
(139)
(140) Three segments are illustrated; a ground segment 1030, a satellite segment 1020, and a user segment 1010. The return links are referred to signal transmissions initiated by the user segment 1010, transponded by the satellite segment 1020, and received by the ground segment 1030. The satellite segment 1020 must feature space assets capable of covering service areas in which users in the user segment 1010 reside, and areas where communications hubs in the ground segment 1030 are located. The return link signals transmitted by a ground user from the user segment 1010 are frequency-translated and then amplified by different transponders, or equivalents, in various satellites in the satellite segment 1020 and coherently combined by a hub terminal. As a result, the received signals-to-noise-ratios (SNR) of the return link signals before a demodulator in the hub terminal are enhanced accordingly.
(141) The differences between this figure and
(142) For a user terminal in the user segment 1010, an input signal stream S(t) is decomposed into M substreams, Sx(t), where M is integer and M>1. The inputs of a N-to-N WF muxer 911 consist of M signal ports and N-M probe signal ports, where N>M. The N outputs features the following characteristics 1. Each of the N outputs is a unique linear combinations of all N inputs including M signal streams and N-M probing signals streams; i. The weighting coefficients among various input signals in each of the N outputs are independent 2. Each of the N inputs appears in all N outputs i. The weighting coefficients on an input over the N-linear combinations features unique distribution; the unique distribution of the weighting coefficients are the constituting components of a WF vector. ii. Various inputs will feature different WF vectors among the N-outputs; iii. The N WF vectors associated with the N-to-N WF muxer are mutually orthogonal to one another in an N-dimensional space in which each of the N-output port is associated with one of the N-dimensions.
(143) The N aggregated outputs from the WF muxer 911 are individually frequency up-converted by an array of frequency up-converters 912, and grouped by frequency-division-multiplex (FDM) muxers 913 for two different satellites 1021 and 1022 in the satellite segment 1020. Group 1 and group 2 of muxed signals, Y1(t) and Y2(t) respectively, feature N1 and N2 aggregated channels, where N1+N2=N and N1, N2 are positive integers. These two groups of muxed signals Y1(t) and Y2(t) are amplified by power amplifiers and then radiated independently by a multibeams antenna 1014 aiming for the two designated satellites 1021 and 1022 separately in the satellite segment 1020.
(144) In the satellite segment 1020, the two slow moving satellites 1021 and 1022 independently receive, transpond, and re-radiate toward a hub terminal the N1 and N2 channels of aggregated signals respectively. As a result, the two groups of aggregated signals in various channels when arriving at the hub terminal in the ground segment 1030 will experience different time delays, drifts in frequencies and phases, and amplitude attenuations/amplifications. It is important to note that: 1. Each of the M Sx(t) is replicated N times and appears in all N1 utilized channels of the first satellite 1021, and concurrently in all N2 utilized channels of the second satellite 1022. 2. Each of the N-M probing signal streams is replicated N times and appears in the same N1 utilized channels of the first satellite 1021, and concurrently in the same N2 utilized channels of the second satellite 1022. 3. A third satellite 1023 is just coming into an orbital region where both the user and the hub are visible from the satellite concurrently. 4. Acquisition protocols will enable both the hub and user links operational for the third satellite 1023.
(145) In the ground segment 1030, a hub terminal features a multi-beam tracking antenna 1034, input FDM demuxers (I-Muxers) 933, a bank of frequency down converters 932, a N-to-N WF demuxer 931, and an associated adaptive equalizer circuitry 931a. The adaptive equalizers 931a driven by an optimization processor 935 utilizing recovered probing signals at the outputs of the N-to-N WF demuxer 931 to iteratively and dynamically compensate for the differentials of amplitudes, phases, and time delays incurred while these wavefronts (WF's) passing though the N1 and N2 propagation channels.
(146) The multi-beam tracking antennas or equivalents of the hub terminals must handle soft hand-over operations engaging and making connection to an incoming satellite 1023 first before dropping connectivity from an outgoing satellite 1021.
(147) The hub terminal in the ground segment for the return link traffic features low noise amplifiers (LNAs) and band pass filters (BPFs) to condition (amplify and properly filter) received signals from at least the two satellites. The two FDM demuxers 933 separate the N1 channels of the received signals from the first satellite 1021 and N2 channels of the received signals from the second satellite 1022. The frequency converters 932 convert the FDM demuxed N channel signals to a common frequency, and the adaptive equalizer 931a to iteratively equalize N receiving channels by altering its compensation weighting vector (CWV).
(148) The N-to-N WF demuxer will perform WF demuxing transform on the N channels of the return link signals to recover M channels of signals, and N-M channels of recovered probing signals, which are utilized to equalize the N-propagation channels. At fully equalized conditions, the N WF vectors will become orthogonal again. Since the probing signals are known a priori, the differences of the recovered probing signals and those of anticipated versions will be used for propagation paths. Zero signals can be used as probing signals.
(149) An optimization loop to iteratively optimize the CWV of the equalizer 931a features 1. a cost function generator to map outputs from the N-M channels of recovered diagnostic signals of the N-to-N WF demuxer 931 into cost functions as performance indexes by a cost function generator (not shown); whereas the performance indexes must be positive, 2. Cost functions can be generated by measuring the leakage signal power at the probing signals. 3. Cost functions may also be generated from measurements of correlations among the N-outputs of the N-to-N WF muxer 931; especially among the output signals from the M signals ports to those from the N-M probing signal ports; 4. an optimization processor 935 to sum all the positively defined cost functions as a total cost; reflecting the current status of the optimization process; whereas high total cost indicating poor performance status, low total cost good performance status, and zero total cost representing perfect optimization status; 5. an optimization processor 935 to measure the gradients of the current total cost with respect to the CWV weighting, derives a new CWV for next update based on a cost minimization algorithm and then sends the new CWV to the equalizer 931a for updating in next iteration.
(150) At steady states, the M recovered outputs of Sx(t) will be reassembled to constitute a higher data rate received signal stream, S(t) (not shown).
(151)
(152) Three segments are illustrated; a ground segment 1030, a satellite segment 1020, and a user segment 1010. The forward links are referred to signal transmissions initiated by the ground segment 1030, transponded or equivalent functions performed by the satellite segment 1020, and received by the user segment 1010. The satellite segment 1020 must feature space assets capable of covering service areas in which users in the user segment 1010 residing, and areas where communications hubs in the ground segment 1030 are located. The forward link signals transmitted by a ground hub terminal from the ground segment 1030 for various user terminals are preprocessed by a 4-to-4 wavefront (WF) muxer 911. The diagnostic signals are incorporated at individually input streams A, B, C, and D before the WF muxer via additional muxing devices (not shown). These WF mux transformed signals, or WF muxed signals, are radiated to 4 designated satellites via a multibeams antenna 1034. These signals are frequency-translated and then amplified by different transponders or equivalents in various satellites in the satellite segment 1020 upon arriving a satellite. The transponded signals are captured by a multibeams antenna 1014 of a user terminal and coherently combined via a WF demuxer 931 before demodulators in the user segment 1010. Different users will pick up the desired signals by switching designated output ports of the WF demuxers to demodulators accordingly. As a result, the received signals-to-noise-ratios (SNR) of the forward link signals in various user terminals are enhanced accordingly.
(153) For a hub terminal in the ground segment 1030, 4 input signal stream A(t), B(t), C(t), and D(t), designated for four different users, are pushed through a 4-to-4 WF muxers before radiated into 4 separated satellites, 1021, 1022, 1023, and 1024. As a result, the 4 outputs feature the following characteristics 1. Each of the 4 outputs is a unique linear combinations of all 4 inputs including probing signals streams multiplexed in individual user signals streams; i. The weighting coefficients, (a11, . . . , a44) among various input signals in each of the 4 outputs are independent 2. Each of the 4 inputs appears in all 4 outputs i. The weighting coefficients on an input over the 4-linear combinations features unique distribution; the unique distribution of the weighting coefficients are the constituting components of a WF vector. ii. Various inputs will feature different WF vectors among the 4-outputs; 1. For the signal A(t), the 4-D WF vector is (a11, a21, a31, a41); 2. For the signal B(t), the 4-D WF vector is (a12, a22, a32, a42) 3. For the signal C(t), the 4-D WF vector is (a13, a23, a33, a43) 4. For the signal D(t), the 4-D WF vector is (a14, a24, a34, a44) iii. The 4 WF vectors associated with the 4-to-4 WF muxer are mutually orthogonal to one another in an 4-dimensional space in which each of the 4-output port is associated with one of the 4-dimensions.
(154) The 4 aggregated outputs from the WF muxer 911 are individually frequency up-converted by an array of frequency up-converters (not shown), and grouped by frequency-division-multiplex (FDM) muxers (not shown) for the 4 different satellites 1021, 1022, 1023, 1024 in the satellite segment 1020.
(155) In the satellite segment 1020, the four satellites 1021, 1022, 1023, and 1024 independently receive, transpond, and re-radiate toward a user terminal multiple channels of aggregated signals respectively. As a result, the four groups of aggregated signals in various channels when arriving at the 4 user terminals in the user segment 1010 will experience different time delays, drifts in frequencies and phases, and amplitude attenuations/amplifications. It is important to note that: 1. Each of the 4 input signals, (A, B, C, and D), is replicated 4 times and appears in all utilized channels of the first satellite 1021, and concurrently in all utilized channels of the second, the third and the fourth satellites 1022, 1023, and 1024. 2. The four input signals are completely independent.
(156) In the user segment 1010, each of the four user terminal features a multi-beam tracking antenna 1014, input FDM demuxers (I-Muxers) (not shown), a bank of frequency down converters (not shown), a 4-to-4 WF demuxer 931, and an associated adaptive equalizer circuitry (not shown). The adaptive equalizers driven by an optimization processor utilizing recovered probing signals at the outputs of the 4-to-4 WF demuxer 931 to iteratively and dynamically compensate for the differentials of amplitudes, phases, and time delays incurred while these wavefronts (WF's) passing though the propagation channels.