A system and apparatus for handling communications between a spacecraft operating in an orbital environment and a ground telecommunications device.

Abstract

This provides an improved system for satellite-based communications that handles communications with mobile stations in environments beyond the design assumptions of the mobile stations, without requiring modifications to the mobile stations themselves. [Solution] A multiple access base station transceiver station 106 in Earth orbit assigns each of the multiple ground mobile stations 104 to a channel block within a multiple channel block, and modulates the signal transmitted to the ground mobile station to a frequency obtained by adding a Doppler frequency offset that is the amount of the expected Doppler shift inverted in sign, due to the relative movement of the ground mobile station and the multiple access base station transceiver station. When the ground mobile station receives the signal, it appears to the ground mobile station that the communication between the ground cellular base station and the ground mobile station is compatible, even if the speed of the ground mobile station relative to the multiple access base station transceiver station exceeds the speed limit specified in the multiple access protocol.

Description

[Technical Field]

[0001] The present invention relates to a system and apparatus for handling communications between a spacecraft and a terrestrial telecommunications device, and more specifically, to communications using features and equipment of a terrestrial telecommunications device typically used for terrestrial telecommunications.

[0002] Cross-reference of related applications This application claims priority to, and is a non-provisional application of, U.S. Provisional Patent Application No. 62 / 465,945, filed on March 2, 2017, entitled "Method for Low-Cost and Low-Complexity Inter-Satellite Link Communications within a Satellite Constellation Network for Near Real-Time, Continuous, and Global Connectivity."

[0003] This application claims priority to, and is a non-provisional application of, U.S. Provisional Patent Application No. 62 / 490,298, entitled "Method for Communications Between Base Stations Operating in an Orbital Environment and Ground-Based Telecommunications Devices," filed on 26 April 2017.

[0004] The entire disclosure of the application cited above is incorporated herein by reference for all purposes as if it were fully contained herein. [Background technology]

[0005] Mobile communications involve signals transmitted between a mobile station (MS) and transceivers, which may provide an interface for the MS to communicate with other network resources such as telecommunications networks and the internet, in order to carry voice and data communications, and possibly location discovery features. Transceivers may be components within a base transceiver station (BTS) that handles traffic from multiple transceivers. The BTS may also include antennas and encryption / decryption elements. Antennas may be selective antennas, and different MSs in different locations may communicate with their respective transceivers via different antennas in the BTS. The BTS may have wired, wireless, and / or optical channels to communicate with their other network resources. A BTS may support one or more transceivers, and a given base station for supporting mobile communications may have a base station controller (BSC) that controls one or more BTS of that base station.

[0006] Examples of mobile stations include mobile phones, cellular phones, smart phones, and other devices equipped to communicate with a specific BTS. While referred to by name as a mobile station in this specification, it should be understood that the operation, function, or characteristics of a mobile station may also be those of a station that is effectively or functionally a mobile station but is not currently mobile. In some examples, a mobile station may be considered a replacement for a portable station that is stationary while in operation, such as a laptop computer with cellular connectivity and several connected peripherals, which can move from place to place, or a mobile station may be stationary, such as a cellular device embedded within an implemented home security system. The requirement is that the mobile station can communicate, or is configured to communicate, using the mobile communication infrastructure.

[0007] A BTS may be controlled by a parent BSC via a base station control function (BCF). Each of these elements may be implemented using hardware and / or software and may include network management and maintenance functions, but a base station may be described as having one or more transceivers that communicate with a mobile station according to an agreed protocol. This may be done by configuring, adapting, or programming the BTS to operate according to the agreed protocol of the BTS, and by configuring, adapting, or programming the MS to operate according to the agreed protocol of the MS. The protocol may include details of how to transmit data between the transceivers and the MS, how to handle errors, how to handle encryption, and how to transmit control instructions and status data between the BTS and the MS. For example, part of the protocol may include an interaction in which the MS contacts the BTS and the BTS indicates to the MS the timing, carrier frequency, and other protocol options to be used. This interaction may include carrying voice data, carrying text data, carrying other data, intracell handover, and providing other tasks.

[0008] For the sake of simplicity, in many examples herein, communication is described as being between a BTS and an MS for interaction with one MS, but it should be understood that the interaction could be through transceivers, radio circuits, antennas, MS antennas, MS radio circuits, software / hardware within the MS, and corresponding paths in other directions from the MS to the BTS. Therefore, in some examples where a BTS is communicating with an MS, the communication is via a transceiver, and this example ignores any descriptions of other transceivers that the BTS may control.

[0009] Examples of protocols that BTS may use include the GSM® (Global System for Mobile Communication, a trademark of the GSM Association) 2G+ protocol, which includes Gaussian minimum-shift keying (GMSK), and the EDGE protocol, which includes GMSK and 8-PSK keying. BTS can handle multiple transceivers using multiple sets of carrier frequencies within the spectral bands of the radio spectrum permitted by the protocol. Thus, if the spectral bands are logically divided into carrier frequency spectra, transceivers may use channels to communicate with the MS using one (or more) of those carrier frequencies. The protocol may identify that for a given channel, there are uplink and downlink subchannels, and in some cases, the carrier frequencies are separated from each other. In some cases, the uplink subchannels have carrier frequencies adjacent to the carrier frequencies of the downlink subchannels. In some cases, all uplink subchannels are in one spectral band, and all downlink subchannels are in another spectral band. For the sake of simplicity, a channel may be described as a single channel even if it has an uplink portion and a downlink portion, and these portions are widely separated within the carrier frequency.

[0010] Some BTSs may offer frequency hopping, in which case the transceiver and mobile station can quickly jump from carrier frequency to carrier frequency together, improving the overall performance of the BTS. The protocol may specify the hopping sequence to use.

[0011] In the GSM protocol, communication between transceivers and MSs is frame-based, and each frame has up to eight time slots. With eight time slots, a transceiver transmits a frame directed to up to eight MSs, each MS being assigned a unique time slot within the frame by the transceiver's BTS. MSs can transmit their transmissions within their allocated time slots, and since each MS communicating with that transceiver knows which time slot to use, similarly directed MSs can communicate back to the transceiver within their allocated time slots. A transceiver does not necessarily use all eight time slots.

[0012] Signaling channels such as the Common Control Channel (CCCH) of the GSM protocol can be used to communicate allocations for time slots and carrier frequencies to the MS. For example, some Common Control Channels are used to create access requests (e.g., creating RACH requests, which are from the MS to the BTS) for paging (e.g., creating PCH requests, which are from the BTS to the MS), access granting (e.g., AGCH, which is from the BTS to the MS), and cell broadcasting (e.g., CBCH, which is from the BTS to the MS). The Access Grant Channel (AGCH) is used to authorize time slot allocations / carrier allocations. Another channel, the Broadcast Control Channel (BCCH), may or may not be used to transmit information to the MS such as Location Area Identity (LAI), a list of neighboring cells to be monitored by the MS, a list of frequencies used within a cell, cell identifiers, power control indicators, whether DTX is permitted, and access control (i.e., emergency calls, call restrictions, etc.).

[0013] Examples of BTSs include cellular telephone towers, macrocell transceivers, femtocell transceivers, and picocells (which may have only one transceiver). BTSs communicate wirelessly with MSs. Some BTSs have wired backhaul connections (interfaces between the BTS and other network resources), such as cellular telephone towers, while others may have wireless backhaul, such as microwave point-to-point bidirectional communication channels. Thus, a BTS can be any of several different types of motorized devices that receive data streams from MSs, process them, and / or forward them to other network resources, as well as receive data streams from other network resources, process them, and / or forward them to MSs via BTS-MS links. In this sense, a BTS acts as an access point for MSs, enabling MSs to access network resources such as telecommunications networks, the Internet, and private networks. Access can be used to route voice calls, other communications, texting, data transfer, video, and more.

[0014] The telecommunications network behind the BTS may include network and switching subsystems that determine how to route data to the appropriate BTS and how to route data received from the BTS. The telecommunications network may also have infrastructure for handling circuit connections and packet-based internet connectivity, as well as network maintenance support. In any case, the BTS may be configured to use some protocols in the MS and other protocols in the backhaul.

[0015] Protocols for communication between MS and BTS may be such that they are standardized, and as a result, any standard MS can communicate with any BTS, assuming that range requirements and membership requirements are met (for example, the MS identifies itself to the BTS in such a way that the BTS or the services used by the BTS determine whether the MS is a member of an authorized group or otherwise authorized to use the services provided by the BTS). Examples of some protocols include the GSM protocol, sometimes also called the 2G (i.e., second-generation) network protocol. Other examples include GPRS (General Packet Radio Service), EDGE (Enhanced Data rates for GSM Evolution, or EGPRS), the 3G (third-generation) UMTS standard developed by 3GPP®, or the fourth-generation (4G) LTE extension protocol.

[0016] These protocols have rules for the use of spectral bands, timing, coding, and conflict resolution. Because a BTS may need to communicate with many MSs simultaneously, the available radio communication paths are divided according to the protocol. A given protocol may have available radio communication paths divided by frequency, time, coding, or two or more of these. This allows multiple users to share the same radio communication path.

[0017] For example, in Time Division Multiple Access (TDMA), the BTS and multiple MSs agree to divide a period into time slots (or "burst periods"). If the first MS may interfere with the second MS, the first MS is assigned the first time slot, and the second MS is assigned a different time slot among the available time slots. Since different MSs use different time slots (and all such MSs agree that the timing is appropriate enough), the MSs can share a common carrier frequency, and their respective transmissions do not interfere. An example is that there are eight time slots of 576.92 μs (microsecond) each for each frame. So, the MS assigned to the first time slot may transmit some bits during the first time slot, stop the transmission at or before the end of that time slot, maintain silence, and then continue the transmission as needed during the first time slot of the next period. A similar assignment occurs to determine when an MS listens to something from the BTS (and to determine when the BTS starts transmitting its data).

[0018] Therefore, using a single carrier frequency, each transceiver of the BTS can communicate with up to eight MSs. The communication to these MSs is grouped into TDMA frames and transmitted on the downlink channel using that carrier frequency channel. The timing is such that each of those MSs can communicate with the BTS on the uplink channel using that carrier frequency channel within their respective time slots. This is called a "TDMA frame". The data rate across all eight MSs using that carrier frequency is 270.833 kilobits / second (kbit / s), and the TDMA frame duration is 4.615 milliseconds (ms) in either direction.

[0019] Frequency Division Multiple Access (FDMA) is another way to divide and allocate available radio communication paths. In FDMA, the available or allocated spectral bandwidth in a radio communication path is divided into different channels by carrier frequencies. Since one carrier frequency is assigned to the first MS and another carrier frequency is assigned to the second MS, both can transmit and receive with one BTS simultaneously.

[0020] In the above example, multiple mobile stations may communicate with the BTS simultaneously, and communication between the BTS and a specific MS involves transmitting information with signals from the specific MS or BTS. Therefore, radio signal collisions are avoided by having the BTS and the specific MS agree on which time slot among multiple time slots to use (TDMA) and / or which carrier frequency among multiple carrier frequencies to use (FDMA). These are examples of multiple access communication.

[0021] In another type of multiple access communication called "Orthogonal Frequency Division Multiple Access (OFDMA)", a subset of subcarriers is assigned to a mobile device, and orthogonal narrow frequency subchannels are assigned to the mobile device to use the allocated spectrum more efficiently compared to FDMA.

[0022] In some frequency allocations, the allocation is per channel block, and a channel block is a set or group of bidirectional channels. Each bidirectional channel uses an uplink carrier frequency for the uplink subchannel and a downlink carrier frequency for the downlink subchannel. Channels can be grouped together into sets of two or more channels based on some logic of classification such that each set shares a common identifier or attribute.

[0023] In some protocols, the spectrum is divided into subspectrals of the carrier frequency, and the duration is also divided into time slots. Typically, the BTS includes logic for determining which channel to assign to which MS. When allocating channels for use by an MS, the BTS may also indicate to the MS that a specific transceiver is assigned to use a specific carrier frequency, that the BTS will use that specific carrier frequency, and which time slots to use from the transmitted / received frames using that carrier frequency. A channel may have uplink subchannels and downlink subchannels. Communication between a given transceiver-MS may use two or more channels, e.g., two or more carrier frequencies and / or two or more time slots, but in many examples herein, the protocol is illustrated as relating to an MS using a channel with only one carrier frequency and only one time slot.

[0024] In yet another example of multiple access communication called Code Division Multiple Access (CDMA), mobile devices can use the same time slot and carrier frequency, but each mobile device is assigned a unique pseudo-random code to encode its signal to and from the BTS. This allows multiple transmitters to occupy the same time and frequency, even if the MSs are transmitting simultaneously using the same carrier frequency or approximately the same time and / or the same time slot. Applying a unique CMDA code, if used, allows the receiver to isolate different receptions by decoding each specific signal sufficiently well for demodulation using the pseudo-random code.

[0025] In practice, CDMA does not strictly separate channels by time or frequency. The use of CDMA results in the transmission of spread-spectrum signals that spread over a wider bandwidth than without coding by using a chipping rate faster than the bitrate of the signal. Therefore, coding a signal with a pseudo-random code can replace the timing and frequency elements typically found in TDMA / FDMA protocols, since each code represents some element of the articulation in both the time and frequency domains. In CDMA communication, the signal propagation delay and timing between MS and BTS are understood, and thus the pseudo-random code is applied to the received signal over several bits / chips, which naturally occupy both a discretized span of some parts of the time domain and a discretized span of some parts of the frequency domain.

[0026] Some multiple access protocols use two or more techniques.

[0027] In a GSM protocol digital mobile radiophone system, the MS and BTS utilize communication across both frequency division multiple access (FDMA) and time division multiple access (TDMA) channels. Therefore, the MS can share the same transmission and reception carriers by allocating separate time slots on each carrier frequency, and each carrier frequency can be handled by a separate transceiver, transceiver module, or logic block.

[0028] In GSM, the BTS (Band Time System) is responsible for allocating time slots to mobile stations (MSs) when access is requested. The GSM frame structure has eight time slots within each TDMA frame. The number of carrier frequencies used can vary. In some regions, some carriers license a large number of carrier frequencies, and MSs in those regions are configured to accept instructions to use one of thousands of carrier frequencies (which the BTS will also support). For example, in Europe, the GSM 900MHz spectral band includes 25MHz of spectrum. If this is logically allocated to 200kHz carrier frequencies (e.g., carrier frequencies centered within each 200kHz subspectral band), and transceivers transmit signals on those carrier frequencies, then 125 carrier frequencies are provided. Using guard bands (unused carrier frequencies) within the frequency domain can reduce this number but may result in improved reliability or ease of signal processing. If a TDMA frame allows for eight time slots, a BTS with a sufficient number of available logical or actual transceivers can simultaneously support 8 * 125 = 1000 MS channels. In time-division and frequency-division, guard slots and guard frequencies may exist, so one division is somewhat isolated from adjacent divisions. Some protocols allow two or more time slots and / or two or more carrier frequencies to be allocated to a single MS in order to provide greater bandwidth.

[0029] In some cases, multiple BTSs exist within the range of supported MSs, and therefore MS support may be spread across BTSs, potentially coordinating to avoid using the same carrier frequency as adjacent BTS where possible. BTSs may be programmed to spread these frequencies across their entire tower using a specific reuse scheme. A BTS may also be limited in the number of MSs it can support by the size of its pipes to other network resources. For example, a BTS might use 1 to 15 carrier frequencies (i.e., its transceiver uses 1 to 15 carrier frequencies in its transmit / receive frames, allowing it to support 8 to 120 users simultaneously anywhere).

[0030] Each MS typically includes a processor, memory, radio circuitry, power supply, display, input elements, etc., to perform its function. The processor can read from program memory to perform the desired function. For example, program memory may contain instructions on how to form a data stream, how to pass it to the radio circuitry, how to read the internal clock to determine the value of the system clock and appropriately time listening and transmitting, and how to set appropriate frequencies for transmission and reception.

[0031] Each BTS typically includes a processor, memory, radio circuitry, power supply(s), interface to the telecommunications network, and diagnostic interface to perform its function. The BTS's processor can read from program memory to perform the desired function. For example, program memory may contain instructions on how to form a data stream, how to pass it to the radio circuitry, how to communicate with the telecommunications network, how to read the internal clock to determine the system clock value and appropriately time listening and transmitting, how to set appropriate frequencies for transmission and reception, and how to keep track of various MSs and their states, locations, assignments, etc., and possibly how to store them in locally available memory.

[0032] In the method described above, the MS contacts the BTS to allocate several time slots within a frame of several carrier frequencies, and the BTS notifies the MS of its allocation. Since both the BTS and the MS have the same (or nearly the same) system clock, they communicate within their allocated time slots and carrier frequencies. The allocation and allocation communication to the MS may be carried out using the random access channel used by the MS to request the allocation. In the GSM protocol, this is called RACH processing.

[0033] In the GSM example, communication over a radio communication path is parsed into TDMA frames with a duration of 4.61538 ms, each containing eight time slots. Each time slot is long enough to hold 156.25 bits of data. In one application, MS or BTS transmits 148 bits of data within time slots exceeding 546.46 μs, with a guard time of 8.25 bits (30.46 μs) between time slots. In the GSM900 band, the radio communication path has a bandwidth of 25 MHz each in the uplink and downlink directions, using the 890–915 MHz spectral band for the uplink subchannel and the 935–960 MHz spectral band for the downlink subchannel, providing 125 carrier frequencies (125 carrier frequencies in each direction at 200 kHz intervals). By having 200 kHz guard separation on both sides of each spectral band, 24.6 MHz of spectrum or 123 carrier frequencies remain for moving data. Next, the total capacity of such a wireless communication path (bidirectional) would be 156.25 bits per time slot multiplied by 8 time slots per frame multiplied by 216.667 frames / second * 123 carriers = 33.312 Mbits / second.

[0034] Considering that MS can be mobile, the MS may be at some distance from the BTS, and that distance can vary. For example, if the BTS is fixed to a cell phone tower, but the MS is 10km away and traveling at 100kph, and you want to continue a voice conversation over the telecommunications network using the MS. If the BTS and MS are within a few meters of each other and the MS is not moving, the signal propagation time and Doppler shift due to movement can be ignored. If the MS is traveling at 100kph relative to the BTS, it can sometimes be ignored, but if the MS is at some distance, propagation time must be considered, or instead, a transmission within one time slot may not be received at all within that time slot but may arrive delayed within the time of another time slot, which can cause communication loss.

[0035] To account for propagation delay, transmitters advance or delay their transmissions, sending bursts of radio frequency (RF) signals to account for the delay, and receivers anticipate the transmissions allocated with adjusted time. When there are many MSs and one BTS, it is often useful that the MSs adjust their transmission times so that the BTS is where all time slots are aligned. Similarly, while a BTS can transmit its transmission within a given time slot, to account for propagation delay, the MSs delay or advance the time they expect to hear or receive the transmission. In addition to the BTS assigning time slots or slots and carrier frequencies(s) to the MSs, the BTS may indicate the propagation delay or distance between the BTS and the MSs.

[0036] For a BTS operating using the GSM protocol, the BTS perceives the propagation delay of an MS signal by how the signal reaches the RACH (Random Access Control Channel). The RACH channel is an uplink-only time slot used when the MS needs access to the channel to transmit data. The MS requests channel access by sending an 87-bit signal burst in the RACH. The RACH burst is designed to have a 69.25-bit guard period between it and the next time slot. As a result, the burst can slide up to 69.25 bits within the RACH slot without adverse effects. When the RACH burst reaches the BTS, the BTS can measure the number of these guard bits that the signal burst has slipped to the right (i.e., moved further in time), and thus determine the signal propagation delay. When the BTS responds to the MS with information about its channel allocation, the BTS includes something called a "timing advance" (TA), which can be expressed as the number of bits to which the MS needs to advance its signal so that it reaches the BTS within the correct time slot and does not flow out into an adjacent time slot. In the GSM protocol, the value of the timing advance can range from 0 to 63 bits, where 0 bits corresponds to no round-trip propagation delay, and 63 bits corresponds to the propagation delay that an MS 35 km away from the BTS would experience, assuming the radio signal travels at the speed of light.

[0037] Without careful timing adjustment, transmissions from MS operating at different distances may reach the BTS within the same time slot, causing collisions or superpositions. These collisions create interference from the BTS's perspective, which impairs the quality and reliability of communication. Guard time (measured in bits and called "guard bits") can be used to prevent burst timing errors from creating signal collisions, but this can only account for small time alignment errors within the internal clock and cannot account for the extended, variable propagation distance differences.

[0038] For example, since there can be a guard time of 30.461 μs (8.25 guard bits) between time slots, even if the first MS is 4.569 km (9.138 km round trip) away from the BTS and has been allocated the first time slot, and the second MS is very close to the BTS and has been allocated the next time slot, the relative propagation delay of the signals will not cause interference. This is because the signal from the first MS will be delayed by 30.461 μs, while the BTS will receive the latter half of the transmission during the guard time, and the transmission will be completed before the time slot of the second MS begins. In many cases, the guard time is too short to be applied to MS at all distances that can be found. For example, if an MS is 10 km away (20 km round trip), the propagation delay of the transmission from that MS to the BTS will be 33.333 μs, which exceeds the guard time, so the BTS will receive the transmission simultaneously with a transmission from another MS that has been allocated the next time slot.

[0039] One solution for adapting to a distal MS sharing the same BTS is to use a timing advance mechanism. The GSM protocol provides an example of this. In the initial handshake between the MS and the BTS, such as using the Random Access Channel (RACH) of the GSM protocol, the BTS determines the distance between the MS and the BTS. The BTS may transmit and receive time stamps during the RACH handshake when calculating the distance between the MS and the BTS, assuming each MS is based on uplink propagation delay.

[0040] The determined distance may not be the actual distance between the MS and BTS, but for many purposes, a pseudo-distance is sufficient. Where used herein, “pseudo-distance” is a value that may or may not be the actual value of a certain distance, but is used as a proxy or assumed distance. That is, the MS, BTS, or other location modules assume the value is a distance, and the various components are designed so that the use of that value works well enough when it is close enough to the actual value. As an extreme example, suppose the MS and BTS are 2 meters apart, but there is something directly interfering with the signal between them, and the nearest path is a 3km path with a great many reflections. In such a case, the pseudo-distance would be 3km, and the MS and BTS would operate as if they were 3km apart. Since the signal path their transmissions follow is 3km, it works when used as the value of the distance between them.

[0041] Generally, the pseudo-distance or pseudo-range of distance measured between two objects may differ from the actual distance or range of distance that can be measured by determining the time it takes for a radio frequency signal to propagate from one object to the other. Due to signal reflection and multipath, the line of sight distance (or range of distance) between the source and receiver of a signal may differ slightly from the propagation distance of that signal, in which case the pseudo-distance (or range of pseudo-distance) will differ from the actual distance (or range of distance). However, in consistent use, many operations can function solely on the pseudo-distance value. In other uses, "pseudo" can be used similarly to indicate an estimate, assumption, approximation, etc.

[0042] Once the BTS determines the pseudodistance of the MS, the BTS stores the pseudodistance in a table it maintains for each parameter and variable of the active MS using its transceiver. The BTS communicates this value to the MS in a control message as described elsewhere in this specification. The MS is then programmed to implement “timing advance,” taking into account a copy of its system clock, subtracting the propagation delay corresponding to the pseudodistance, and sending the transmission to the BTS earlier than the start of the scheduled time slot. The RACH process to determine these values ​​may include a variety of steps, as described further below.

[0043] When used herein, the propagation delay is expressed as a conversion coefficient or an approximation thereof as c = 3 * 10 8 The propagation distance can be calculated using m / s, and vice versa. When there is a standardized bit rate for transmission, such as 270.833 kbits / s for GSM, the propagation delay or distance can be expressed in terms of bits. For example, a 12km separation results in a round-trip propagation delay of 80μs, with each bit being transmitted in 3.692μs. The 12km separation and 80μs propagation delay can be equivalently expressed as 22 (more precisely, 21.66) bits of separation or propagation. Thus, the propagation of 1 "bit" is equivalent to a round-trip propagation distance of approximately 555 meters and 3.692μs.

[0044] MSs operating at different distances than BTSs are assigned different timing advances to adapt to their respective communication distances. For convenience, this may be represented as an integer number of bits. To account for the movement of the MS, this timing advance value is used by modules within the MS to determine when a message is being communicated to the MS and when it is being transmitted or received, and can be updated with sufficient periodicity and frequency to adapt to a moving target that may have a time-varying communication distance relative to the BTS. For example, if a user is using an MS on a high-speed train traveling at 200 kph, the distance may need to be updated more frequently than if the user were walking on the street.

[0045] In a specific example of the GSM protocol, timing advance is represented as a 6-bit value, with a minimum value representing a 0-bit timing advance and a maximum value representing a 63-bit timing advance. Since the GSM protocol assumes each bit corresponds to 3.692 μs (and approximately 555 meters in round-trip propagation delay), a 63-bit timing advance would be used if the pseudo-distance is approximately 555 m / bit * 63 bits = 34,965 m, or approximately 35 km. Therefore, this timing advance technique will function correctly for MSs within a range of 0 to 35 km from a BTS. The GSM protocol is programmed so that a BTS will not respond to a request from an MS, or at least not anticipate such a request, if the BTS determines that the MS is more than 35 km away from the BTS. This is not a problem if there are other closer BTSs, or if the distribution of BTSs is such that all points are within 35 km of one or more BTSs.

[0046] In timing advance, the MS transmits the transmission before its time slot begins (from the MS's clock timing), and when the transmission is received by the BTS after the propagation delay, the BTS receives the transmission completely within the time slot corresponding to the propagation delay of the timing advance. The MS can do this correctly because it is provided with a value regarding the amount of timing advance to use. Note that the actual distance, and therefore the actual propagation delay, may differ from the pseudo-distance, but in most cases this is not a problem because there is enough margin in MS-BTS communication to handle differences in internal clocks, transmitter variations, etc.

[0047] This timing mechanism works well when there is always one or more BTSs within 35km of any MS, but this is not always the case. In some geographical areas, having BTSs within 35km of any point in that area may not be practical, viable, or economical. For example, in rural, remote, or island geographical areas, BTS infrastructure with such spacing may not be accessible to the land, and users with MSs may be scattered and spread out, so BTSs may not be used, cannot be installed, or may not be able to receive power. In such situations, an "extended range" mechanism can be used. Such a mechanism is possible with the GSM protocol.

[0048] In the extended range mechanism, each MS is allocated two consecutive time slots instead of one, so the MS can communicate with the BTS without requiring any timing advance if it can delay transmission by the duration of one time slot. This increases the allowable MS-BTS distance (e.g., 35km to 120km), but the throughput is halved because each TDMA frame only has four allocatable time slots available instead of eight. This may not be significant for rural, remote, or island areas at low data rates. By using a combination of the timing advance mechanism and the extended range mechanism, the maximum allowable MS-BTS can be 35km + 85km = 120km.

[0049] In the extended range mechanism, each MS is allocated an entire time slot as an additional guard period that reduces throughput by half. A variation of this is the “sorted extended range mechanism,” similar to that described in U.S. Patent No. 5,642,355, for example. In the sorted extended range mechanism, time slots are “consumed” and used as guard bits, but these time slots are allocated to MS by distance, with the nearest MS receiving the first time slot, and the furthest MS receiving the last time slot before any “consumed” time slots allocated to MS, i.e., not allocated to any MS. The consumed time slots are used as needed for guard bits because the extended range of the MS spreads the transmission. In practice, this “splits” unused time slots between bursts.

[0050] The "ring extended range" mechanism can be used if the distance exceeds 85 km or for other reasons. In the ring extended range mechanism, a fixed minimum distance is assumed, and the timing at the BTS is adjusted by that fixed minimum distance. The BTS assumes that all MSs are at least that distance away, so MSs closer than the minimum communication distance are not supported. This is similar to the technique described in U.S. Patent No. 6,101,177. Without requiring any modification of the MS, the 35 km range obtained using the timing advance mechanism can be used to support MS-BTS distances from the minimum distance to the minimum distance plus 35 km. In one example, the minimum distance is 85 km, but different minimum communication distances can be used. In this example, the BTS can support MSs in the range of 85 km to 120 km from the BTS.

[0051] The ring-extended range mechanism may be used with eight of the eight allocated time slots, allowing it to handle MSs located at distances ranging from 85km to 120km from the BTS. However, this creates a physical coverage gap that extends somewhat radially from the BTS, as any signal burst transmitted from that area will reach the BTS much faster than the way the BTS would see its time slot. Instead, the BTS provides coverage for the area ring. The ring-extended range mechanism can be used in geographical areas where there is a physical separation, such as a lake or valley, between the BTS and the MS designed for service, so having areas inside the ring where the MS is not supported would not be an issue.

[0052] It should be noted that GSM systems utilize a TDMA frame offset between uplink and downlink subchannels. In a typical GSM frame structure, the uplink TDMA frame (or MS Tx and BTS Rx) is offset by three time slots from the downlink TDMA frame (or BTS Tx and MS Rx) to ensure that the MS does not need to transmit and receive simultaneously. It will be obvious to those skilled in TDMA communications that this offset between uplink and downlink subchannels is irrelevant to communications over extended distances and is not the same as the time slot synchronization offset used for uplink TDMA frames only within the ring extended range mechanism.

[0053] When a ring extension range mechanism is combined with an extension range mechanism, it can be used alone or in combination to have BTS coverage exceeding a radius of 120 km. These techniques are often sufficient for ground communications, as such communications are typically limited by the curvature of the Earth. For example, to provide distance D for line-of-sight communication between a ground-based MS and a BTS transceiver, the BTS transceiver should be mounted at a height of at least h = [SQRT(6370^2 + D^2) - 6370] km. In the case of D = 120 km and h = 1130 m, 1,130 m is higher than any structure being built today, so the height of the tower is far greater than the height limiting factor of ground communications than the distance, and therefore, techniques to extend the distance, hypothetically, beyond 120 km, are not very useful for cellular voice, data, text, and similar capacity ground communications, although in some cases, there are exceptions in selected locations where there are large geological structures to mount the transceiver on.

[0054] Satellite communications can be used in areas where it is impractical to distribute base station towers to broaden coverage, such as when it is impractical to place base stations in any location close to several locations, for example, within 35km or 85km of several locations, or within 120km where tall towers can be equipped. Typically, satellite communications are very expensive and therefore are only used to support costs for applications such as resource exploration, search and rescue, and rescue.

[0055] In this specification, “satellite” means an artificial satellite launched from Earth with the goal of operating in orbit, and / or an artificial satellite operating in orbit whether it is assembled whole or partially on the Earth’s surface and / or assembled whole or partially in orbit. A satellite may be assembled and / or operate in one orbit and move to another. A satellite may be propelled or operated without its own means of propulsion, and may or may not depend on other objects in orbit to provide propulsion. As used herein, a satellite operating in orbit and not under propulsion is in a more or less stable orbit. Such an orbit has a minimum distance above the Earth’s surface due to atmospheric drag. There is no strict dividing line between a vacuum sufficient to put a satellite into orbit and excess atmosphere that could cause a satellite to de-orbit, and Low Earth Orbit (LEO), about 400-500 km above Earth, has been shown to be practical, although even lower altitudes are possible, especially for densely packed spacecraft such as nanosatellites.

[0056] The extremely large minimum distance for practical orbits meant that entirely different technologies had traditionally been used for satellite communications. In some cases, ground stations were not mobile, while in others, although they were mobile, they required power-intensive, heavy, large, and specialized equipment. In addition to distance, the movement of satellites within orbit had to be dealt with.

[0057] There are many solutions for communication between satellites and ground-based portable handsets on Earth that use the TDMA protocol for communication. Some satellite providers include Iridium®, Globalstar®, Thuraya®, and Inmarsat®, which are based on custom-developed satellite phones or user terminals (i.e., unique hardware devices that attach to or connect to existing mobile phones via physical or RF connections). The design of the system, satellite, and terminals can be simplified because each user terminal can be specifically designed to function with other user terminals. The drawbacks are that it can be expensive and impractical, and requires specific terminal equipment that would be needed for all end users or small groups of end users. While the custom terminal approach simplifies system design, it ties users to a particular provider because operators are free to configure details such as communication scheme, power levels, and frequency. As a result, end users may need to purchase satellite phones (or user terminals that connect to existing mobile phones) that cost hundreds or thousands of dollars, have large, cumbersome antennas, consume considerable power, and require exorbitant monthly fees to operate, potentially requiring the use of two or more satellite providers. This has limited the market appeal of traditional satellite phones.

[0058] As an example, U.S. Patent No. 8,538,327 describes a modification of user equipment that calculates delay measurements based on satellite position data and user equipment position data. The timing of uplink communications from the user equipment is adjusted for delay when transmitted to the satellite. The user equipment also calculates a frequency offset based on satellite position and velocity data and adjusts its uplink signal frequency accordingly to account for dynamic Doppler shifts within the communication system. Naturally, this requires specific ground-based user equipment designed for satellite communications.

[0059] As another example, U.S. Patent Publication 2006 / 0246913 describes a scheme for managing RF signal propagation delay using a subcoverage ring characterized by reducing the difference in round-trip propagation delay. This uses geosynchronous Earth orbit (GEO) satellites to act as relays, connecting remote mobile stations to base stations in its network. To cope with the much larger delays transmitted by the GEO satellites, separate processing devices serve separate subcoverage rings or zones by configuring themselves to match the range of allowable propagation delays of the rings / zones. The link between the mobile station and the GEO satellite cannot be closed without the assistance of additional user terminal hardware for power, signal directivity, and frequency operation.

[0060] An improved system is needed for satellite-based communications with portable or mobile devices. [Overview of the Initiative]

[0061] Multiple access transceivers for communication with mobile stations within the environment handle conditions beyond the design assumptions of the mobile station without necessarily requiring modifications to the mobile station, as can be seen in Earth orbit. Multiple access transceivers are adapted to close communication with the mobile station while conditions exceeding the design assumptions of the mobile station, such as greater distance, greater relative motion, and / or other conditions commonly seen when the functions of a ground transceiver are performed by an orbital transceiver. An orbital transceiver may include a data analyzer that analyzes the frame data structure, a signal timing module that adjusts the timing based on the propagation delay from orbit to the ground, a frequency shifter, and a programmable radio that can communicate from Earth orbit using a multiple access protocol, so that the communication is compatible with, or appears to be compatible with, communication between a ground cellular base station and a ground mobile station.

[0062] Multiple access transceivers can support terrestrial mobile stations, which are cellular telephone handsets, smart phones, and / or connected devices. Signal timing modules can be adapted to adjust the frequency of transmitted signals to terrestrial Doppler shifts based on orbit. Signal allocation logic can allocate the capacity of a multiple access transceiver, distributed across multiple time slots, multiple carrier frequencies, multiple orthogonal subcarriers, and / or multiple code sequences, to multiple terrestrial mobile stations, including terrestrial mobile stations. A multiple access transceiver may include, for each ground mobile station, a range calculator that determines the distance from the multiple access transceiver to the ground mobile station, and a signal timing module that determines the timing of the transmission signal relative to the frame structure, wherein the frame structure comprises a plurality of slots, each having a zero or non-zero time slot synchronization offset that results in a variable transmission delay due to the distance from the multiple access transceiver to the ground mobile station, and an input signal assigner that assigns a listening time slot within the frame structure to listen for communications from the ground mobile station, wherein the listening time slot is timed based on the distance from the multiple access transceiver to the ground mobile station, and the listening time slot is one of a plurality of time slots, the plurality of time slots are variably delayed within the frame structure to take into account a multiple access transceiver handling communications from a plurality of ground mobile stations at a plurality of distances from the multiple access transceiver.

[0063] A multiple access transceiver may have multiple time slots, which are variably delayed within the frame structure to accommodate a multiple access transceiver handling communications from multiple ground mobile stations at multiple distances from the transceiver, by allocating each of multiple different distance ranges to each of multiple channel blocks. The different distance ranges may collectively cover a slant range from zenith distance to minimum elevation distance, where zenith distance is the distance between the ground mobile station and the zenith position of the satellite carrying the multiple access transceiver, and minimum elevation distance is the distance between the ground mobile station and the satellite's position when it enters the satellite's design footprint. Each of the different distance ranges may be approximately 34–35 kilometers, and the difference between zenith distance and minimum elevation distance is 210–250 kilometers. The satellite's design footprint may be circular, elliptical, rectangular, and / or independent of the antenna's function and / or antenna beam shape, but in many examples it is approximated as circular.

[0064] The multiple access transceiver is adapted for operation in Earth orbit and configured to communicate with ground mobile stations, and comprises: a data analyzer which defines a frame structure in which time slots are assigned to which of a plurality of ground mobile stations; a range calculator which determines the distance from the multiple access transceiver to each ground mobile station; a channel allocation module which allocates the plurality of ground mobile stations to a plurality of channel blocks, the channel blocks having a ground frequency and an orbital frequency offset; a signal timing module which determines the timing of the transmitted signal relative to the frame structure; and a signal modulator which modulates the signal to the ground mobile station at a ground frequency using the orbital frequency offset, the orbital frequency offset which at least substantially corresponds to the expected Doppler shift in the signal transmitted to the ground mobile station due to the relative movement of the multiple access transceiver and the ground mobile station, so that the ground mobile station receives the signal at a ground frequency. Multiple channel blocks may be assigned based on the relative positions of the satellite and ground mobile stations carrying the multi-access transceiver, and the orbital frequency offset may vary in small increments, such as 5 kHz increments.

[0065] In certain embodiments, a multiple access base station having one or more transceivers handles communication with multiple terrestrial mobile stations, and the terrestrial mobile stations are configured to anticipate base station communication with terrestrial cellular base stations that are within a limited distance from the terrestrial mobile stations and / or traveling below a limited speed relative to the terrestrial mobile stations. The multiple access base station comprises: a data analyzer that analyzes data received by the multiple access base station according to a frame structure, wherein the frame structure defines which time slots are assigned to which of a plurality of terrestrial mobile stations, and the frame structure includes a plurality of slots, each having a zero or non-zero time slot synchronization offset resulting in a variable transmission delay due to the distance from the multiple access base station to the plurality of terrestrial mobile stations; a signal timing module that determines signal timing adjustments to the frame structure of a signal to be transmitted to a terrestrial mobile station based on the base-to-mobile distance between the multiple access base station and the terrestrial mobile station, wherein the base-to-mobile distance exceeds a limit distance; and a programmable radio that can communicate from the multiple access base station to a terrestrial mobile station using a multiple access protocol and take signal timing adjustments into consideration, such that the communication is compatible with, or appears to be compatible with, communication between a terrestrial cellular base station and a terrestrial mobile station, even though the base-to-mobile distance exceeds a limit distance.

[0066] A multiple access base station may be adapted to communicate with multiple ground mobile stations, each comprising a cellular phone handset, a smartphone, and / or connected devices. The limited range may be approximately 100 kilometers, 120 kilometers, or some other distance, and the base-to-mobile distance may exceed that limited range. The multiple access protocol may be one of the following: CDMA-based protocol, LTE protocol, GSM protocol, OFDMA-based protocol, FDMA-based protocol, TDMA-based protocol, EGPRS protocol, or EDGE protocol. A multiple access base station may be an orbital base station operating within Earth orbit, with a limited range of 120 kilometers, and the base-to-mobile distance of multiple ground mobile stations being approximately 500 kilometers to approximately 750 kilometers. In another variation, a multiple access base station is a base station capable of operating within the Earth's atmosphere, and includes being mounted on or inside one or more of the following: an airplane, a drone, and / or a balloon, with a limited range of 120 kilometers, and the base-to-mobile distance exceeding 120 kilometers.

[0067] A multiple access base station may include signal allocation logic for allocating the capacity of the multiple access base station, distributed across multiple time slots, multiple carrier frequencies, multiple orthogonal subcarriers, and / or multiple code sequences, to multiple terrestrial mobile stations, including terrestrial mobile stations. A programmable radio can listen to communications from terrestrial mobile stations using a multiple access protocol and includes a range calculator that determines the base-to-mobile distance of each of the multiple terrestrial mobile stations from the multiple access base station to the terrestrial mobile station; a receive timing module that determines the timing of the received signals of the terrestrial mobile stations relative to the frame structure based on the base-to-mobile distance of the terrestrial mobile stations; and an input signal assigner that listens to communications from terrestrial mobile stations by allocating a listen time slot within the frame structure, the listen time slot being one of multiple time slots, the multiple time slots being variably delayed within the frame structure to accommodate a multiple access base station handling communications from multiple terrestrial mobile stations with multiple base-to-mobile distances.

[0068] Multiple time slots can be variably delayed within the frame structure to accommodate multiple ground mobile stations with multiple base-mobile distances by allocating each of multiple different base-mobile distance ranges to each of multiple channel blocks. A multiple access base station may be an orbital base station operating in Earth orbit, where multiple different base-mobile distance ranges collectively cover a slant range from zenith distance to minimum elevation distance, where zenith distance is the distance between a ground mobile station and the zenith position of the satellite carrying the multiple access base station, and minimum elevation distance is the distance between a ground mobile station and the satellite's position when the ground mobile station enters the satellite's design footprint.

[0069] The distance range between different base stations and mobile stations can be approximately 34-35 kilometers each, and the difference between the zenith distance and the minimum elevation distance is 210-250 kilometers.

[0070] The satellite's design footprint can be circular, elliptical, rectangular, etc., and may be independent of the antenna's function and / or the shape of the antenna beam.

[0071] In some variations, a multiple access base station having one or more transceivers handles communications with multiple terrestrial mobile stations that are within a limited distance from a terrestrial mobile station and / or moving below a limited speed relative to the terrestrial mobile station, and is configured to anticipate base station communications with a terrestrial cellular base station. The multiple access base station includes a data analyzer which analyzes data received by the multiple access base station according to a frame structure which defines which time slot is assigned to which of the multiple terrestrial mobile stations, and a multiple access protocol which anticipates that a terrestrial mobile station receives a signal at a specified frequency and transmits a signal at a specified frequency; a Doppler deviation calculator which determines, for each of the multiple terrestrial mobile stations, the Doppler deviation of each terrestrial mobile station due to the speed of each terrestrial mobile station relative to the multiple access base station; and a channel allocation module which allocates each of the multiple terrestrial mobile stations to a channel block in a plurality of channel blocks, each channel block having a terrestrial frequency and a Doppler frequency offset. The present invention provides a signal modulator that modulates a signal to a terrestrial mobile station on a terrestrial frequency using a Doppler frequency offset, wherein the Doppler frequency offset corresponds at least substantially to the expected Doppler shift in the signal transmitted to the terrestrial mobile station due to the relative movement of the multiple access base station and the terrestrial mobile station, so that the terrestrial mobile station receives the signal on a terrestrial frequency, and a programmable radio that can receive communications from the terrestrial mobile station using a multiple access protocol and take into account the Doppler frequency offset of the terrestrial mobile station, so that the communications are compatible with, or appear to be compatible with, communications between a terrestrial cellular base station and a terrestrial mobile station, even though the speed of the terrestrial mobile station relative to the multiple access base station exceeds the speed limit.

[0072] The speed of a ground mobile station relative to a multiple access base station may be a result of the multiple access base station being in Earth orbit, and the Doppler frequency offset can vary in increments of 5 kilohertz.

[0073] A multiple access base station may have signal allocation logic for allocating the capacity of the multiple access base station, which is distributed across multiple time slots, multiple carrier frequencies, multiple orthogonal subcarriers, and / or multiple code sequences, to multiple ground mobile stations, including ground mobile stations.

[0074] A multiple access base station may provide uplink and downlink subchannels for each of several channel blocks, including continuous spectra of uplink and downlink subchannels. Channel blocks may be allocated such that adjacent channel blocks are allocated to adjacent Doppler frequency offsets.

[0075] In a particular embodiment of a multiple access base station having one or more transceivers handling communications with multiple terrestrial mobile stations, the terrestrial mobile stations are configured to anticipate base station communications with terrestrial cellular base stations that are within a limited distance from the terrestrial mobile stations and / or traveling below a limited speed relative to the terrestrial mobile stations, and the multiple access base station is a data analyzer, the data analyzer defines which time slot is assigned to which of the multiple terrestrial mobile stations, and comprises a frame structure comprising a plurality of slots, each having zero or non-zero time slot synchronization offsets resulting in variable transmission delays due to the distance from the multiple access base station to the multiple terrestrial mobile stations, and transmits with the expectation that the terrestrial mobile stations will receive signals at a specified frequency and transmit signals at a terrestrial frequency, received at a Doppler frequency offset, and is received by the multiple access base station according to a multiple access protocol further comprising a multiple access protocol, which identifies channel blocks within a plurality of channel blocks, and each channel block has a specified terrestrial frequency and a specified time slot. A data analyzer that analyzes the data, a signal timing module that determines signal timing adjustments for the frame structure of a signal transmitted to a terrestrial mobile station based on the base-to-mobile distance between a multi-access base station and a terrestrial mobile station, wherein the base-to-mobile distance exceeds a limit distance and a specified signal timing adjustment is assigned to each channel block, a Doppler deviation calculator that determines the Doppler deviation of each terrestrial mobile station due to the speed of each terrestrial mobile station relative to the multi-access base station for each terrestrial mobile station of a plurality of terrestrial mobile stations, and assigns a specified Doppler frequency offset to each channel block, and assigns each of the plurality of terrestrial mobile stations to a specified channel block within a plurality of channel blocks based on the specified signal timing adjustment and specified Doppler frequency offset of the channel block, wherein the number of channels in the specified channel block has or is expected to have the specified signal timing adjustment and specified Doppler frequency offset,The present invention may include a signal modulator that modulates signals to the terrestrial mobile stations on terrestrial frequencies using a dynamic channel assignor that accommodates a number of terrestrial mobile stations, and a Doppler frequency offset, wherein the Doppler frequency offset at least substantially corresponds to the expected Doppler shift in the signals transmitted to the terrestrial mobile stations due to the relative movement of the multiple access base station and the terrestrial mobile stations, and so that the terrestrial mobile stations receive signals on terrestrial frequencies, and a programmable radio that can receive communications from the terrestrial mobile stations using a multiple access protocol and take into account the Doppler frequency offset of the terrestrial mobile stations, so that communications are compatible with, or appear to be compatible with, communications between a terrestrial cellular base station and a terrestrial mobile station, even though the base-to-mobile distance exceeds the limit distance and the speed of the terrestrial mobile station relative to the multiple access base station exceeds the limit speed.

[0076] The following detailed description, along with the attached drawings, will provide a better understanding of the nature and advantages of the present invention. [Brief explanation of the drawing]

[0077] Various embodiments of this disclosure are described with reference to the drawings.

[0078] [Figure 1] This illustrates one possible environment in which the present invention may be used. [Figure 2] Figure 1 illustrates an example of adding an environment. [Figure 3] This illustrates an example of a frame-based protocol used between a base station transceiver and a mobile station. [Figure 4] This illustrates an example of the effectiveness of using propagation delay and timing advance when using time-division protocols. [Figure 5] This shows an example of using the extended range feature of a time-division protocol. [Figure 6]This demonstrates an example of using extended range features and timing advances in a time-division protocol. [Figure 7] This shows examples of various MSs at different distances from BTS, and their distances can be determined to be at least approximately. [Figure 8] Figure 7 illustrates how various MSs at different distances are allocated to time slots based on their determined distances and provided for sorted extended-range communication. [Figure 9] This illustrates a ring-type coverage area using a synchronous offset. [Figure 10] This illustrates how timing is adjusted for the ring mechanism. [Figure 11] This illustrates an example of a satellite footprint and the resulting distance range within that footprint. [Figure 12] This example illustrates how different time slots are allocated to different mobile stations based on their ground locations, in order to implement a ring scheme and sorted extended range for TDMA communications. [Figure 13] This illustrates how different carrier frequencies are allocated to different mobile stations based on their ground location distance, allowing the use of a ring scheme with varying ring diameters for different carrier frequencies. [Figure 14] This shows how a satellite footprint can be subdivided into Doppler shift strips. [Figure 15] This is a flowchart of the measurement process for determining the pseudo-distance and Doppler shift from the MS. [Figure 16] This shows how a satellite footprint can be subdivided into a ranging ring, a Doppler shift strip, and both the ranging ring and the Doppler shift strip. [Figure 17] This illustrates an example of a ranging / Doppler shift cell for satellite footprints. [Figure 18] Figure 17 illustrates an example of the allocation of a ranging / Doppler shift cell to a specific carrier frequency and Doppler offset block. [Figure 19] This illustrates how to allocate the frequency spectrum to various Doppler offset blocks of the channel, taking into account the Doppler shift in communication between BTS and MS. [Figure 20] This illustrates an example of allocating cells in a satellite footprint based on the expected density of MS per cell. [Figure 21] Figure 20 illustrates an example of channel allocation that can be used for the allocation and mapping shown. [Figure 22] This is a swim diagram illustrating the setup and distance determination process. [Figure 23] An example of a transceiver and its related components is shown. [Modes for carrying out the invention]

[0079] Various embodiments are described in the following description. For the purpose of explanation, specific configurations and details are described to provide a complete understanding of the embodiments. However, it will also be apparent to those skilled in the art that embodiments may be carried out without specific details. Furthermore, well-known features may be omitted or simplified so as not to obscure the embodiments described.

[0080] The techniques described and proposed herein include the design of satellite-based base transceiver stations (BTS) that implement transceivers for transmission and reception between ground-based devices such as mobile stations (MS), which are satellites or parts of satellites capable of operating in orbit and are mobile stations designed for use with ground BTSs. Often, an MS can be used without requiring any physical modifications or even any software modifications, in which case the MS is communicating with a transceiver and a BTS and may not be aware that the BTS is not a ground BTS, or more schematically, that the BTS is operating beyond the scope of the MS's design assumptions, such as being at a relative distance greater than the design assumption of the distance, being at a relative velocity much faster than the relative velocity the MS would be designed to be at, and other design assumptions.

[0081] For orbital transceivers and ground-based MSs, the BTS exceeds the design assumptions of the MS design, which assume a maximum distance of approximately 35 km from the BTS to the MS. This exceeds the design assumptions of the MS design, which assume that relative motion, such as the time derivative of the distance between the BTS and MS during communication, can be ignored or is much smaller than the 7.2–7.8 km / s that would be experienced compared to the orbital transceiver. Other design assumptions may also have an impact. For example, the orbital transceiver will have a limited time window for communication because it will ascend above the minimum altitude relative to the MS until the satellite is below the minimum altitude of the opposite horizon.

[0082] Many of the examples and details herein relate to orbital transceivers adapted, configured, and programmed to close off communications with MS operating as if their design assumptions still applied, but these techniques can be used outside of orbital examples. For example, they can be used for BTS located high enough that the slant angle exceeds 120 km. For example, if a BTS can be mounted at an altitude of 1,130 meters, this is sufficient to enable a line of sight (slant range) to MS beyond 120 km. Platforms such as airplanes, UAVs, high-altitude drones, hot air balloons, high-altitude balloons, suborbital vehicles, spaceplanes, mountains, or even some very large towers may be conditions under which some or all of these techniques can be found useful. Also, while the techniques described can be deployed even with ground-based BTS, it is worth noting that the antennas are directed to serve MS operating on platforms that create long communication distances (such as exceeding 120 km) and / or high Doppler shift environments such as exceeding approximately 200 KPH. This may include conditions where the MS is operating on the Earth's surface, in the atmosphere, or in a space environment, and the BTS is on the Earth's surface and is either mobile (e.g., on some vehicle) or possibly stationary.

[0083] These techniques may also prove useful when the MS is in orbit and the design assumptions are true, and the BTS is ground-based and needs to operate even if the design assumptions are not true, and can be adjusted to suit those MSs. For example, the MS could be used on a moving aircraft, or possibly a future space agency. A ground-based base station tower with a sufficiently large antenna could perform actions to shut down communication with the MS while dealing with similar violations of design assumptions, such as long distances and high Doppler shifts.

[0084] BSC and MSC (including Home Location Register or HLR and Subscriber Handling) functions may also be supplied by satellite, or some functions not required in orbit may be implemented on the ground. BTS, BSC, and / or MSC functions may be implemented using conventional off-the-shelf software-defined radio or commercial-grade (or proprietary) hardware / software, insofar as they can be programmed, configured, or adapted to perform the required functions.

[0085] The BTS may still function despite the increased distance between the BTS and MS, which causes distance-induced power reduction and distance-induced flight time delays, as well as the effects of greater relative movement between the BTS and MS, which exceeds the typical ground-based relative movement that the MS may perform relative to the BTS. The latter causes Doppler shift, and conventional MSs such as cell phones may not be designed to handle such large Doppler shifts caused by a satellite moving relative to the MS at a speed of 7.6 km / s, which can be experienced in some cases at LEO. These Doppler shifts will be variable, as they vary depending on the location of the MS within the satellite's footprint. Negative Doppler shifts will be observed at locations behind the satellite, and positive Doppler shifts will be observed at locations in front of the satellite.

[0086] Power levels must be addressed. For example, the GSM specification requires mobile phones to increase their transmission power to 1-2W (depending on the frequency) as needed. Mobile phones do this as a matter of course over RACH, and once a channel is allocated, the BTS can command them to remain quiet when there is no need to transmit at "high volume". With a suitable BTS antenna capacity, 2 watts may be sufficient transmission power to close a link at a reasonable elevation angle at an altitude of 500km using an antenna such as a 50cm form factor, and the speed of data transfer can be adjusted as needed. For example, one implementation might focus on narrowband messaging with 2G speeds and short data bursts rather than attempting to support data rates such as 4G LTE, although the latter may be possible. In such a way, lower power levels and higher data rates can still typically be supported by space-based base stations with sufficient antenna technology. However, lowering the power levels and increasing the data rates of ground-based devices tends to increase the power and mass requirements of the space segment.

[0087] As used herein, “footprint” refers to the area on the Earth’s surface that is within the range of a satellite that closes a communication channel with the BTS. While the examples herein use a circular footprint, it should be understood that footprints may not be circular and may depend on obscured factors, such as the shape of the Earth’s surface and atmospheric conditions. In some examples, the footprint is a “design footprint” that differs from the actual footprint. For example, a satellite may actually be able to communicate with a mobile device that is at a certain distance and therefore within the satellite’s actual footprint, but for selectivity, performance, or other reasons, the system using that satellite is designed for a smaller footprint than the actual footprint, i.e., a different footprint, such as a design footprint. The boundary of the design footprint may be a circle or ellipse projected onto the Earth by the satellite, centered on a point on the surface just below the satellite and having a radius that the satellite is designed to cover, such as a specific slant range.

[0088] Where used herein, “surface” is used to refer to the location of an MS, but it should be understood that “surface” is not limited to the Earth’s surface. Where an MS is described as surface-based or on the surface, the MS could be on the Earth’s surface, on the surface of a body of water, somewhat below the Earth’s surface or somewhat below the surface of a body of water, on the upper floors of a building, in a structure that is not precisely at surface level, inside an airplane or otherwise in the air but in the atmosphere, or in the hands of a person standing in a similar location. However, for clarity of explanation, an MS may be described as on the surface to distinguish it from an element in orbit. This does not mean that the systems described herein are not usable for MS in orbit. Where applicable, unless otherwise stated, an MS in orbit can also support an MS in orbit, provided that the device is electrically, mechanically, and otherwise sufficiently durable for use in orbit, even if it has not been specifically modified to communicate with a BTS in orbit.

[0089] As used herein, “in orbit” means that an object is at a location, traveling at a certain velocity relative to an inertial frame that is (more or less) stationary with respect to the Earth’s gravitational center, and experiencing little to no atmospheric resistance at that location, allowing it to easily maintain its orbit. In some examples herein, an orbital distance is given, which, conventionally, refers to an approximate typical distance from an average or typical point on the Earth’s surface to describe the orbit. “LEO” is used in some examples, and it should be understood that these examples can apply to orbits that may be somewhat outside the range conventionally defined as LEO but still considered to be orbits. Unless otherwise indicated, “in orbit” can also describe orbits around other celestial bodies, such as Mars, the Moon, the moons of other planets, or even points of interest such as L1 or L2. In many of the examples herein, BTS is in orbit around the Earth, and MS is terrestrial. The teachings herein can be used for other situations, such as when the BTS and MS exchange locations, or when the BTS is in an airplane, an unpiloted autonomous vehicle, a balloon, etc., instead of Earth orbit, or when similar difficulties are encountered, or more schematically, when there are conditions where difficulties such as distance, propagation delay, and / or Doppler shift exceed those that the MS is typically designed to support or experience, for example, when the design assumes that the MS will be built and / or programmed.

[0090] In traditional TDMA communication systems, there are timing and signal power aspects that close the communication link, i.e., the received signal power is sufficiently high above the noise / interference environment, so that data can flow on the channel at the desired data rate and bit error rate, creating conditions for following the expected protocol so that the communicating devices do not abandon at either end. As described herein, satellite-based BTS can communicate with ground-based MS designed for use with ground-based BTS. Satellite-based BTS modifies TDMA communication with MS in a way that allows communication over distances of some difference, while being transparent to MS and taking into account variable propagation delay. Having satellite constellations within LEO can provide continuous connectivity from orbits 400-500 km above the Earth to MS using conventional ground communication technologies and protocols, at an acceptable economic deployment cost and a reasonable service life. BTS provides suitable timing for TDMA frame structures, enabling orbital range communications and channel assignment or allocation schemes that support the mitigation of pseudodistance and Doppler shifts in the required range, addressing signal interference problems and mismatches associated with Doppler shifts due to orbital interference. As a result, the BTS described herein can provide communications between spacecraft and ground telecommunications devices, as well as communications using the features and equipment of ground telecommunications devices typically used for ground telecommunications. This can extend the radio coverage range of the communications system, enabling communications between spacecraft in orbit and mobile phones or other communications / radio devices. BTS can be used in communications systems that leverage multiple access techniques in the frequency and / or time domains used by conventional mobile phones (i.e., TDMA, FDMA, OFDMA, etc.) to communicate with spacecraft in orbit using GSM cellular communications protocols or similar ground protocols.

[0091] Because BTS handles RF signals that are sliding in both the time domain and the frequency domain, it can be implemented using communication modes that employ multiple access schemes in the time domain and / or frequency domain, such as TDMA, FDMA, CDMA, OFDMA, etc., which need to handle a given associated distance and associated velocity. Generally, unless otherwise indicated, the teachings herein can be applied to one or more of these examples of multiple access schemes and systems, where multiple mobile stations are communicating with or attempting to communicate with a BTS, and to avoid interference, the protocol used provides multiple access by having each MS use a different time slot, carrier frequency, and / or code sequence. Thus, many examples are described with reference to the TDMA / FDMA protocol, but can be extended to other protocols.

[0092] In this specification, distances may be expressed in units other than kilometers, in which case certain conversions are assumed. For example, the speed of light in a vacuum may be a conversion factor in which distance is expressed in seconds, such as microseconds and milliseconds. The propagation delay in certain circumstances may be the speed of light in a vacuum or longer, but from the context, the method for determining the distance given by the propagation delay expressed in seconds will be obvious to those skilled in the art.

[0093] Similarly, distance and / or time may be expressed in bits, in which case a certain bitrate is assumed. For example, if the bitrate is 270.833 kbit / s, a period expressed as "156.25 bits" refers to a period of 576.92 μs, and a distance expressed as 10 bits corresponds to a distance of 5.538 km, since transmitting 10 bits occupies 36.92 μs. In a period of 36.92 μs, the signal can travel a distance of 5.538 km (round trip) at the speed of light in a vacuum. The difference between the speed of light in a vacuum and the actual propagation speed may vary and may be taken into consideration, but these details may be omitted for illustrative purposes to avoid complicating the explanation.

[0094] Exemplary BTS and description of its operation The present invention will be described in detail with reference to certain, but not necessarily preferred, embodiments of the invention. These particular embodiments are illustrative, and those skilled in the art of multiple access communication systems and orbital mechanisms will, upon reading this disclosure, recognize that other modifications are possible and that this disclosure relates to many types of multiple access communication systems between a MS on the surface of a planetary body and a BTS (Body-to-Ship) spacecraft operating in various orbits around that planetary body.

[0095] In many examples herein, the orbit of the satellite, including the BTS, is given as a circular orbit with an altitude of 500 km; however, it should be understood that the teachings herein apply to other orbits adjusted accordingly. In some examples, the BTS operates as a GSM BTS, simulates the operation of a GSM BTS, or fully performs functions for communicating with ground mobile stations (MS) near the Earth's surface, i.e., outside of orbit.

[0096] In some of the examples herein, the satellite footprint is given as a set of points on or near the Earth's surface where the satellite is above a minimum elevation angle when viewed from the MS. As used herein, when the satellite is directly above the MS, the MS "sees" the satellite at an elevation angle of 90 degrees (and therefore the MS is in the direction of the nadir relative to the satellite). In the examples herein, the slant range is 90 degrees to 40 degrees, but other slant ranges greater or smaller may be used. Those skilled in the art will understand how to appropriately modify the calculations herein after reading this disclosure.

[0097] Using a radius of 6370 km relative to Earth and assuming a 500 km circular orbit, at an elevation of 90 degrees, the MS within the footprint is 500 km from the BTS. Using basic geometry, it can be determined that from a certain point on the Earth's surface, a satellite in a 500 km circular orbit will appear at an elevation of approximately 40 degrees relative to the horizon of that point, if the distance from the satellite to that point is approximately 741 km. The signal propagation delay between the MS and the satellite BTS is a function of distance, and the distance to the satellite in orbit is a function of the orbital radius and the elevation, which is the angle between the satellite's position vector and the MS's position vector. When the elevation is 90 degrees, i.e., the satellite is overhead and the MS is at a surface point in the direction of the satellite's nadir, the distance can be taken as, or approximately as, the difference between the orbital radius and the Earth's radius. When the elevation is less than 90 degrees, the distance can be calculated. For some minimum elevations where a connection is expected to be made, it is generally considered that this will correspond to the longest distance supported for a connection over the angle. At a minimum elevation angle of 40 degrees, the interaction time between the MS and the satellite BTS can be calculated in the BTS and / or MS as follows: For a 40-degree elevation angle and a 500km circular orbit, the central angle of the Earth is given by ACOS(R_earth*COS(min_elev) / (R_earth+h))-min_elev=4.74 degrees, where R_earth=6370km (Earth's radius), min_elev is the minimum elevation angle (40 degrees in this example), and h is the satellite altitude (500km in this example). The time it takes for the MS to move from a minimum elevation angle of 40 degrees relative to a satellite on one horizon to a minimum elevation angle of 40 degrees relative to a satellite on the other horizon can be calculated as the time it takes for the satellite to travel 2*4.74=9.47 degrees relative to the Earth's surface. As described herein, a satellite in a 500km circular orbit is moving at 7.11km / s relative to the Earth's surface. Therefore, the time it takes to travel 9.47 degrees across the Earth's surface at this speed is approximately 9.47 degrees * pi / 180 * (R_earth + h) / 7.11 km / s = 159.86 seconds. Naturally, other minimum elevation angles can be used, and the calculation can be adjusted accordingly.This assumes that the MS travels directly through the center of the satellite footprint as it passes overhead. Under various conditions, the BTS and / or MS may take this value of 159.86 seconds into account when planning and coordinating communications and scheduling.

[0098] The actual distance may vary depending on atmospheric effects and other physical interactions. In this example, the BTS is then configured to support communication with devices located in the range of approximately 500 km to 741 km between the BTS and the MS, and those MSs must support the BTS if they view the BTS at an elevation lower than 40 degrees from the local horizon. In some implementations, the lower limit is lowered from the orbital distance to allow communication with MS well above the ground. For example, if an MS is located inside an airplane flying at 15,000 meters, but the satellite assumes a minimum distance of 485 km, it cannot support that MS. In another example, a satellite in geostationary Earth orbit (GEO) may provide a BTS, in which case the minimum distance is approximately 35,786 km.

[0099] Figure 1 illustrates an environment in which the present invention may be used. As shown therein, on the surface 102 of the Earth (or a planet or celestial body related thereto), there are several mobile stations (MS) 104 that may be mobile, or in some cases portable or stationary, but can function as MSs. These MS 104 communicate with orbital BTS 106 via BTS-MS links 108. As illustrated, each of the BTS 106 has an orbital velocity relative to the surface 102 and a certain separation distance.

[0100] Figure 2 illustrates an additional example of the environment in Figure 1, in which Person 202 has various devices 204, including elements constituting a mobile station such as a smart phone 204(1), a laptop computer 204(2), and a tablet device 204(N), each of which is configured and / or adapted to communicate with a ground BTS, and if Person 202 wishes to communicate with or access the internet 208 and / or internet-connected resources 210, they can do so via the BTS 206. Other examples of devices may be devices without a user interface, such as industrial or home appliances that interact over a network (e.g., “Internet of Things” devices).

[0101] Figure 3 illustrates an example of a frame-based protocol used between a base transceiver station (BTS) 306 and a mobile station (MS) 304 over a ground-orbit link 308 using protocols such as TDMA or other protocols that can also be used for terrestrial communications.

[0102] As illustrated in the examples herein, BTS employs various techniques that enable it to transparently support MS configured solely for terrestrial cellular communications. While several examples are described, we will first describe some methods for range extension of TDMA systems.

[0103] Figure 4 illustrates how a timing advance mechanism can be used. It should be understood that where a timing diagram is shown, it implicitly means that there is a corresponding module with logic that follows that timing diagram. Figure 4 also shows the effects of using propagation delay and timing advance when using a time-division protocol.

[0104] Figure 4 shows the eight time slots of a TDMA frame. These may be part of a larger data structure, which is omitted for clarity in the explanation. If an MS or BTS has time slots allocated for MS-BTS communication, each device is programmed to use a local copy of the system clock for each device to determine when to start transmission, when to stop transmission, when to start listening, and when listening can be stopped, which would correspond to their allocated time slots.

[0105] In Figure 4, the top line illustrates transmission 402 from the MS. In this specification, “Tx” is an abbreviation for transmission, transmitter, or transmitting, as the context may require. Similarly, “Rx” is an abbreviation for reception, receiver, or receiving, as the context may require. As used herein, “transmission” is what is sent from a transmitter as part of a communication or signal, and “reception” is what is received. If the transmitter and receiver have the same system time and there is a measurable propagation delay, the transmission and its corresponding reception do not occur in the same system time. From the MS's perspective, the process of transmitting transmission 402 occurs entirely within time slot 1, where it is assumed that time slot 1 is allocated to the MS. If transmission 402 occupies most of the allocated time slot, it is received as reception 404, which is partially received during time slot 2, and received as BTS Rx at the BTS after the propagation delay. This is undesirable. In timing advance, MS sends transmission 412 (from MS's clock timing) before time slot 1 begins, and when it is received by BTS as receive 414 after propagation delay, it is fully completed in BTS within time slot 1.

[0106] Figure 5 shows an example of using the extended range feature of the time-division protocol. In this example, the duration of the time slot is approximately 0.28 milliseconds, representing a distance of 85 km. Therefore, the MS can communicate with the BTS without requiring any timing advance if it can delay the transmission by the duration of one time slot. The extra time slot serves as an additional guard period.

[0107] As illustrated in Figure 5, the MS has eight time slots, but only the first (slot 0), third (slot 2), fifth (slot 4), and seventh (slot 6) time slots are used. As illustrated, MS1 performs transmission 502(0) during time slot 0, MS2 performs transmission 502(2) during time slot 2, MS3 performs transmission 502(4) during time slot 4, and MS4 performs transmission 502(6) during time slot 6. The BTS receives the reception of such transmissions and receives receive 504(0) (referred to as "(0)" in the figure) which starts at any time after the start of time slot 0 and ends at any time before the end of time slot 1. Similarly, the BTS receives receive 504(2) ("(2)") which starts after the start of time slot 2 and ends at any time before the end of time slot 3, and so on for receive 504(4) and 504(6).

[0108] Figure 6 illustrates an example of the use of extended range features and timing advance in a time-division protocol. As shown there, MS transmissions 602 are between their respective time slots, and the BTS receives such transmissions and receives reception 604 at the appropriate time. As illustrated in Figure 6, with the combination of the timing advance and extended range mechanisms, the maximum allowable MS-BTS can be 35km + 85km = 120km. Whether the timing advance mechanism is used alone, the extended range mechanism is used alone, or both are used, the BTS can control which one is used. The MS may not even be aware that the extended range mechanism is being used, as the BTS would simply not allocate time slots every other one. For example, if the BTS determines that the MS is 60km away, the BTS may tell the MS to use a 0-bit timing advance (i.e., not use timing advance) and not allocate the next time slot to any MS. If the BTS determines that the MS is 95km away, the BTS may instruct the MS to use an 18-bit timing advance and may not allocate the next time slot to any MS.

[0109] Figure 7 shows examples of various MSs at different distances from the BTS, and their distances can be determined to be at least approximate. In this example, d A ~d G There are seven MS labeled A-G, each with a pseudo-distance between them. This illustrates how MS can be sorted by distance.

[0110] Figure 8 illustrates how different MSs at different distances in Figure 7 are allocated time slots based on their determined distances and provided for sorted extended range communication. As shown in Figure 8, time slot 0 is allocated to user G, who is closest to the BTS in Figure 7, and time slot 6 is allocated to user E, who is furthest from the BTS in Figure 7. Only seven time slots are allocated. Considering the range of propagation delay, transmissions 802 from the different MSs are received as receive 804, and as a result, transmission 802 does not overlap with another transmission 802, and all receive 804 are received within the TDMA frame duration. As illustrated in Figure 8, signal bursts are progressively delayed across time slots that can eliminate collisions and interference.

[0111] The sorted extended range scheme offers higher throughput than the extended range mechanism, but still allows for MS-BTS distances of up to 120 km and 7 / 8 of the maximum frame capacity (as long as the distance gap between the two sorted MSs does not exceed 85 km in total). In some cases, two or more time slots will be allocated to divide the distance gap, so if N time slots are allocated in this way, N is between 1 and 7, and the throughput will be 1-(N / 8) of the maximum frame capacity. If the time slots are 156.25 bits, the gap can be allocated as the number of bits distributed between the time slots. If this logic is implemented by the BTS, the sorted extended range mechanism implementation does not require any modification to the MS logic or operation because the BTS organizes the calculated time slot allocation.

[0112] Figure 9 illustrates the distance range of a BTS using a ring extension range mechanism and the coverage area of ​​a ring-type system using a synchronous offset. The cross-hatched areas are the areas supported by the BTS. All MSs are at least d * If BTS assumes that the distance is d, then the minimum communication distance d *MSs closer than this are not supported. Without any MS modification, the 35 km range obtained using the timing advance mechanism can be used to support MS-BTS intervals from d * ~d * + 35 km. In one example, d * = 85 km, although other minimum communication distances can be used. In that case, in this example, the BTS can support MSs in the range 85 km to 120 km from the BTS.

[0113] Figure 10 illustrates the transmission and reception timings and how the timings are adjusted for the ring system. The minimum communication distance d * is directly scaled by the time slot synchronization offset selected for use by the BTS on the uplink subchannel. In the MS, transmission 1002 seen by the MS as time slot 0 is transmitted by the MS. In the BTS, reception 404 is received after a propagation delay that is at least d * times the speed of light. Since the value of d * times the speed of light is known, the BTS can simply offset the timing of that time slot by an offset (T_offset = 2×d * / (speed of light)) minutes, where 2 takes into account the round-trip distance between the MS and the BTS, and the BTS receives reception 1004 within the BTS's time slot 0.

[0114] Figure 11 illustrates a satellite footprint, an example of a ring, and the resulting distance ranges of that satellite footprint ring. Satellite 1102 would have a coverage footprint, exemplified in Figure 11 as a lateral footprint 1104 and exemplified as a top-down footprint 1106. Different cross-hatched areas within footprint 1106 indicate different distance ranges between the surface and the BTS, forming a ring. In this example, there are seven rings, but more or fewer rings may exist as needed. In this example, the rings are labeled r0 to r6 and correspond to BTS-MS distances {500-534.4, 534.4-568.9, 568.9-603.3, 603.3-637.7, 637.7-672.1, 672.1-706.6, 706.6-741} (all in km) (which may be pseudo-distance ranges) between the BTS and the MS. Each of these ranges happens to be just under 35 km, which is a useful design choice, as described below. Different design choices may be used for other applications. In the initial handshake, such as the RACH process, the distance between the BTS and MS can be determined, from which the MS can be assigned to one of the rings within the satellite footprint.

[0115] As described below, all MSs assigned to a particular ring may be assigned to a single carrier frequency, or a block of carrier frequencies transmitted on a TDMA / FDMA frame, or by other means. In some embodiments, the rings may overlap so that an MS may be located within two or more rings. For example, the first two rings may be 490–540 and 530–580, and therefore an MS located 535 km from the BTS may be located within one of these rings.

[0116] Depending on the desired application, the orbital BTS can use the following protocols and operations: (1) Timing advance scheme, (2) Extended range scheme (using fewer time slots than all available time slots, instead using unused time slots as guard bits), (3) Sorted extended range scheme (using fewer time slots than all available time slots, instead using unused time slots as guard bits allocated between time slots based on expected variable delay), (4) Ring extended range scheme (coverage is in a ring with an unsupported inner circle) The timing can be shifted accordingly), (5) a multi-ring extended range scheme (similar to scheme (4), using multiple rings to simultaneously cover ranges of different distances and MSs assigned to the rings based on the distance between BTS and MSs), and (6) a sorted channel-ring assignment scheme (similar to scheme (5), but using different rings associated with different carrier frequencies, and for carrier frequencies, using scheme (3) to assign time slots to MSs within the distance range of that ring), or adjustments can be made according to one or more combinations of (1), (2), (3), (4), (5), and (6).

[0117] Timing advance, ring, and sorted extended range scheme Figure 12 illustrates a first example of a BTS using a timing advance scheme, a ring extended range scheme, and a sorted extended range scheme. In this example, a sorted extended range scheme for TDMA communication can be implemented by allocating different time slots to different mobile stations based on their ground locations, and a ring scheme is used to make the range ground-based.

[0118] In this example, satellite 1202 is d * It is in orbit at an altitude of d * There is no need to support closer MS, and there is a certain maximum distance d from BTS. maxIt is assumed that there is no need to support MS which are far away. In this example, d * ~d max There are five MSs, MS1 to MS5, labeled by their distance from the BTS, which is within a certain range. MS1 to MS5 are assigned to time slots 4 to 0 respectively, while time slots 5, 6, and 7 are not assigned, so a sorted extended range scheme can be used in the three time slots corresponding to the guard time. This corresponds to approximately 486 bits and is illustrated in MS frame 1204. As a result of the distance between the MS and the BTS, signal bursts of MS1 to MS5 are received, as shown in the BTS frame 1206.

[0119] In this example, the timing advance is 22 bits (required for a range of 12 km), and the ring synchronization offset is 875 bits, which corresponds to a distance of approximately 488 km, and therefore, d * The distance is approximately 488 + 12 = 500 km. The extended range guard time uses up all three time slots, but the distance between MS and BTS is approximately 295 km (i.e., d max -d * This provides the full range of ). Assuming a maximum range of 35km, which can be 0-63 bits for timing advance, the range of the sorted extended range scheme can be approximately 35km to approximately 640km, depending on the number of time slots allocated to guard time, as shown in Table 1. In Table 1, the range assumes that the full range of 0-63 bits for timing advance is available. [Table 1]

[0120] This TDMA frame structure enables broad satellite-based cellular coverage over a wide geographical area. Even with this solution, operational problems and challenges still need to be addressed. First, each frame has just over half the potential throughput of a typical GSM frame. Second, in this configuration, each frame is subjected to a variable Doppler shift of approximately plus or minus 35 kHz (which varies depending on the solution, including orbit selection, slant range, and frequency usage). However, the Doppler shift problem can be mitigated using the on-orbit BTS schemes and equipment described herein. Timing challenges can be addressed using the following schemes:

[0121] Timing advance and sorted channel-ring assignment scheme Figure 13 illustrates how different channels are allocated to different mobile stations based on their ground location relative to their BTS, allowing the ring scheme to be used with varying ring diameters for different channels. As shown there, the scheme using timing advance (for a range of approximately 0-35 km) and the sorted channel-ring allocation scheme can provide another range of approximately 241 km without exhausting the time slots. In the sorted channel-ring allocation scheme, as illustrated in Figure 11, the satellite footprint is divided into rings, with each ring paired with a separate carrier frequency. Each ring operates with a different synchronization offset.

[0122] As used herein, a channel may include one or more specific frequency divisions within the protocol, such as a group of carrier frequencies. In Figure 13, the supported pseudo-distance range between the nearest and farthest potential targets is 241 km, distributed across seven pseudo-distance range rings. This results in a coverage range of approximately 34 km per ring, and the synchronization offset may differ for each different ring assigned to a channel block or set of channels. By keeping the offset between channel blocks below approximately 35 km, full throughput is made possible within each channel by eliminating the need for extra slot guard periods, and then sufficient timing advance by itself.

[0123] The RACH request burst can be used to determine the propagation distance from the signal to each MS. The BTS can use a broadcast channel (BCCH) to continuously or periodically notify MS on the RACH of which carrier frequency and time slot the BTS will allocate to that MS for uplink use. The BTS will know exactly when the MS will transmit its RACH burst and can count the number of bits between that time and the time the actual burst arrives. By dividing that number of bits by the channel bitrate (270.83 kbps for GSM), the BTS can calculate the round-trip propagation delay time. The BTS then calculates the propagation distance or pseudodistance by dividing the speed of light by the round-trip propagation delay time. Depending on the calculated pseudodistance, each MS qualifies its allocation to a channel within a particular channel block. For example, in the configuration shown in Figure 13, the channels within channel block b0 are assigned to MSs that have calculated pseudo-distances of 500 km to approximately 534 km, and the channels within channel block b1 are assigned to MSs with pseudo-distances measured from the BTS in orbit at approximately 534 km to approximately 568 km, and the same applies to the other ranges shown in Figures 11 and 13.

[0124] The first channel block b0 has an uplink TDMA frame offset from the transmission uplink frame by the same amount as shown in Figure 12. The next channel block b1 has a frame offset by an additional 62 bits from the frame of channel block b0. Thereafter, the frame of each channel block has an additional offset of approximately 62 bits compared to the previous channel block (i.e., channel block b i+1 The frame is channel block b i (Offset by approximately 62 bits extra from the frame). Each bit of the frame offset corresponds to approximately 555m, and each ring / channel block is extended by approximately 34km further than the previous one, so this configuration, utilizing 62 bits, creates different coverage rings, each approximately 34km. By allocating different synchronous offsets, each channel block represents coverage of a different ring in space (and the Earth's surface). If the channel blocks are given synchronous offsets in increments of 62 bits and the traditional embodiment of GSM is used, full throughput can be achieved on all channels, and very scalable coverage can be achieved. This can be done without requiring modifications to the MS of GSM. A top-down view of the range rings is shown in Figure 11. The channel blocks of each range ring are defined by a characteristic "range of distance" specified for this particular embodiment, indicated by the key on the left of Figure 11.

[0125] Handling of Doppler shift While the above methods and their variations may provide maximum throughput across all channel spectra, the transmission frequency may differ between transmission and reception due to the relative movement of the BTS and MS. Using a Doppler solution, we can consider scenarios where multiple MSs exist within a similar pseudo-distance range from the BTS in orbit, but may experience a wide range of variation in the perceived carrier frequency deviation. For example, consider two MSs calculated to exist within the same ring / channel block b6 in Figure 11. In this case, one MS is positioned at the leading edge of the top of the satellite coverage footprint, and the other at the leading edge of the bottom of the satellite coverage footprint.

[0126] In Figure 11, the satellite is directly above the center of the coverage area shown for channel block b0 (the origin of the arrow) and moving in the direction of the arrow labeled "velocity". The first MS in front of the satellite's velocity vector experiences a positive Doppler shift within the received frequency, and the second MS behind the satellite's velocity vector experiences a negative Doppler shift within the received frequency. If the same frequency is assigned to these MSs, the satellite may receive signal burst frequencies from the MS that are several kilohertz away (up to 70 kHz away in the 1800 / 1900 GSM band). Furthermore, assigning adjacent channels to MS experiencing significantly different Doppler shift environments can lead to signal interference on the satellite.

[0127] Figure 14 illustrates a method for mitigating this problem, showing how a satellite footprint can be subdivided into Doppler shift strips. As illustrated therein, consider a satellite 1402 traveling at a certain velocity relative to the Earth's surface 1404. The satellite footprint 1406 is the view from the satellite at the indicated velocity. MS within area 1410 of the satellite footprint 1406 vectors experience a positive Doppler shift within the receiving frequency of signals from satellite 1402, while MS within area 1412 of the satellite footprint 1406 vectors experience a negative Doppler shift within the receiving frequency of signals from satellite 1402. A specific Doppler shift within a receiving frequency can be determined using a simple geometry, and for a range of Doppler shifts, the satellite footprint 1406 can be subdivided into strips separated by contour lines, each contour line assigned a value 1420 corresponding to its respective Doppler shift.

[0128] In three-dimensional space, given sufficient information, the Doppler shift at any point within the satellite footprint can be calculated by BTS or MS. One way to do this is to assume that all vectors are represented in an Earth-Centered, Earth-Fixed (ECEF) coordinate frame. This is also known as the Earth's rotation frame, as it is the coordinate system that rotates the Earth around its axis of rotation in space. In this process, each vector is treated as a vector quantity with three constituent values, and consequently, each constituent value in the vector represents a value along each dimension of the coordinate frame represented by the vector. Such numerical values ​​can be stored in memory for processing by the processor.

[0129]

number

number

number

number

number

number

number

number

number

number

number

[0130] In Equation 1, D is the calculated Doppler shift, and λ is the wavelength of the carrier frequency that can be calculated by dividing the carrier frequency by the speed of light.

[0131] As an example, consider a spacecraft operating in equatorial orbit at an altitude of 500 km, which happens to be directly above the meridian at a particular moment (for example, the direct nadir relative to the satellite is at the intersection of the equator and the meridian). At the same particular moment, the stationary MS1430 is positioned almost below sea level relative to the spacecraft, but is resting on the equator at 1 degree east longitude (for example, its latitude and longitude position may be described as [0, 1]).

[0132] In this scenario, the satellite's ECEF position coordinates are approximately [6870 km, 0 km, 0 km]. The velocity vector of a spacecraft in a circular orbit at 500 km is nearly perpendicular to the position vector and (in the case of an equatorial orbit) parallel to the equator. The magnitude of the velocity vector relative to the Earth's surface can be calculated as SQRT(mu_earth / (R_e+h))-w_earth*(R_e+h)=7.11 km / s, where mu_earth is the Earth's gravitational constant (mu_earth=398658.366 km). 3 / s 2 ) where R_e is the radius of the Earth at the equator (R_e approximately 6370 km), and w_earth is the angular velocity of the Earth's rotation (w_earth = 7.27 * 10 -5 The velocity is given by radians per second, where h is the satellite's altitude (in this example, h = 500 km). Therefore, the ECEF velocity vector of the spacecraft is approximately [0 km / s, 7.11 km / s, 0 km / s]. The ECEF position of a stationary MS at 0 degrees latitude and 1 degree east longitude is approximately [R_earth*cos(1 degree), R_earth*sin(1 degree), 0] = [6369 km, 111 km, 0]. Therefore, the ECEF position of this stationary MS relative to the spacecraft is [6369 km, 111 km, 0] - [6870 km, 0 km, 0 km] = [-501 km, 111 km, 0]. Thus, the Doppler shift of the 1900 MHz signal received from the spacecraft by this MS is as shown in equations 2, 3, and 4.

number

[0133] As explained above, the pseudodistance can be calculated using the signal received by the BTS from the MS on RACH. This signal can also be used to approximate the Doppler shift from the MS. The BTS knows the on-carrier frequencies, just as it knows the time slots when RACH is on. Therefore, when the BTS receives a RACH burst, it can measure the center of the burst frequency and calculate the offset (difference) from the expected center frequency on RACH. Depending on the magnitude of the Doppler shift the system experiences, the satellite BTS may or may not need to listen over a wider frequency range on RACH.

[0134] Figure 15 is a flowchart of a measurement process in which RACH can be used for a BTS to determine the pseudodistance and Doppler shift from the MS. RACH may be indicated when the MS wants to start a session (e.g., sending an SMS text, making a phone call, sending data). It is not necessary to frequently measure / update the Doppler shift value. The Doppler shift value changes with the time it takes to request access to the channel and transmit data, and the payload is typically not large enough to impair the system's ability to send and receive signals. In cases where this could be a problem, the BTS may make predictive changes and assume that the MS is not moving at high speed. This process can be used for satellite BTSs when managing pseudodistance and Doppler shift measurements to adjust channel allocation / distribution.

[0135] As illustrated in the flowchart of Figure 15, at the start of the process, the satellite BTS broadcasts RACH timing information on the BCCH channel (step 1501), and the MS then learns the time slots in which RACH is on (step 1502). Knowing this, the MS transmits bursts during the RACH time slots that the BTS has instructed the MS to use (step 1503). The bursts arrive at the BTS with their frequencies delayed and offset (step 1504). The BTS flow then has two threads: one for delay and one for Doppler shift. In the first flow, the BTS counts the number of bits delayed by the burst (step 1505), calculates the round-trip delay by dividing the counted number of bits by the channel bit rate (step 1506), and then calculates the pseudo-distance by dividing the round-trip delay by twice the speed of light (step 1507). In the second flow, the BTS measures the center frequency of the burst (step 1508) and calculates the Doppler shift by subtracting that center frequency from the center frequency of RACH (step 1509). The two threads are then joined, and the BTS checks the channel configuration matrix to assign the MS a channel configured for its pseudodistance and Doppler shift (step 1510). The BTS then checks if the channel is already configured (step 1511). If yes, the BTS assigns the configured channel to the MS (step 1513); if no, the BTS configures the channel for the detected pseudodistance and Doppler shift environment of the MS (step 1512), and the process ends.

[0136] Since the BTS can acquire knowledge of Doppler shift from each MS, it can assign a specific Doppler shift range to a specific channel. In doing so, each individual channel may have its own specific locally reduced range of potential Doppler shift values. For example, some channels may experience only a 0–5 kHz shift within the carrier frequency because the channels are assigned to MS in a particular strip shown in Figure 14, while other channels may experience only a 25–30 kHz shift within the carrier frequency. Because the Doppler ranges are clearly defined and more localized for each channel, they can be used as modifiers for channel assignment and allocation. This approach greatly simplifies handling the wide range of Doppler shift variability across the entire set of serviceable MS within the satellite footprint.

[0137] Returning to Figure 14, the figure illustrates the perceived Doppler shift at various locations across the satellite coverage footprint. Intuitively, half of the satellite footprint in the direction of the velocity vector experiences a positive Doppler shift, while the other half experiences a negative Doppler shift. More counterintuitive is how the geometry of the Earth's curvature creates a Doppler shift map on the satellite footprint, which is drawn by increasingly curving contour lines.

[0138] One technique described herein is to assign channel blocks to pre-determined Doppler shift blocks, just as channel blocks are assigned to pre-determined pseudodistance range rings, as described above. Given that carrier frequencies are assigned to specific pseudodistance ranges and Doppler shifts, the actual Doppler shift experienced by each channel is unique with respect to that channel's frequency. An example implementation of this technique would take this into account. In one design, the contour map of the Doppler shifts uses the center frequencies of the spectrum in question, and the figure assumes a 1900 MHS GSM with a satellite at an altitude of 500 km and an elevation angle of 40 degrees.

[0139] In Figure 14, each dashed line defines the boundary of a Doppler shift strip used to localize the potential Doppler shift of each channel and, consequently, minimize interference. The curvature of the contour lines on the map is a result of the geometry of the communication link and the communication frequency.

[0140] Figure 16 illustrates how the satellite footprint can be subdivided into range rings, Doppler shift strips, and both range rings and Doppler shift strips. As illustrated, the pseudo-distance range forms the ring, and the Doppler shift contour forms the strip. When these are superimposed on a grid (which does not necessarily have to be an orthogonal or linear grid), the satellite footprint 1602 is divided into grid cells bounded by the first distance value, the second distance value, the first Doppler shift value, and the second Doppler shift value. Thus, each of these grid cells corresponds to a combination of the pseudo-distance range and the Doppler shift range relative to the BTS on orbit, and is a modifier of the MS assigned to a particular channel (or one of a particular set of channels).

[0141] It should be noted that while the satellite footprints described herein are inherently circular, this is not mandatory. Depending on the antennas used on the satellite and how they are configured, the footprint may be more square or elliptical in shape. Non-circular footprints may offer the advantage of potentially increasing or decreasing the diffusion of propagation delay and / or Doppler shift environments within the footprint.

[0142] This grid represents a combination of pseudo-distance ranges and Doppler shift ranges corresponding to modifications of pseudo-distance and Doppler shift channel blocks. The grid cells described above are assumed to be symmetric with respect to the satellite's velocity vector. This means that each grid cell off-center from the satellite's coverage area has a “twin” grid cell on the opposite side of the satellite footprint. The term “twin” grid cell is used because both MSs in these grid cells operate with similar pseudo-distance and Doppler shifts, so these two grid cells share a “bucket” logically associated with the pseudo-distance range and Doppler shift range (i.e., an MS is logically allocated to a bucket based on whether its pseudo-distance falls within the pseudo-distance range allocated to that bucket, and whether its Doppler shift falls within the Doppler shift range allocated to that bucket).

[0143] Handling Doppler shift in a specific MS device Some protocols may be more resilient to Doppler deviation when demodulating downlink signals, while others may not. For some devices or protocols, a 2.5 kHz deviation can be the Doppler deviation threshold. However, even some lower-end cellular phones may be able to demodulate BCCH signals with offsets of up to 20 kHz from what would typically be the center carrier frequency of that channel. This may be related to the interaction between the BTS and the MS on the FCCH (Frequency Correction Channel), which is another broadcast channel used to synchronize the local clock with the BTS. This synchronization is ultimately the information the phone needs to subsequently demodulate the BCCH and other downlink channels. Therefore, larger Doppler deviation strips than the exemplary 5 kHz strip used in the example above can be used. For example, the bucket can be adjusted and stretched to accommodate a wider range of Doppler deviations, up to at least 20 kHz in either direction. In practice, this can prevent the need for Doppler shift bucketing altogether if the satellite footprint is small enough that the highest Doppler shift case is less than 20 kHz. This may not be true for other protocols such as NB-IoT, which use much smaller signal bandwidths. NB-IoT also has other differences, such as the multiple access protocol being the LTE NB-IoT protocol and the limiting distance being 40 km, which exceeds the base-to-mobile distance.

[0144] Channel allocation As described herein, a BTS can support multiple transceivers, each using its own carrier frequency, and each of these multiple transceivers can support up to eight MSs. Since transceivers can be configured to use one of many possible carrier frequencies, channels can be associated with transceivers. In the example above, there are 123 available carrier frequencies. While some of these many carrier frequencies can be allocated to MSs as needed, there are some advantages to having them allocated by grid cells, so that buckets of similarly located MSs with similar distances from the BTS and similar Doppler shifts using the same carrier frequency(s) can be strategically allocated. A channel (which may logically have uplink and downlink subchannels, as described above) can be allocated one of several time slots and one of several carrier frequencies. A channel can be identified only by its allocated characteristics, such as the channel's carrier frequency and the channel's time slot, although in some situations each channel may be given a channel label. Channel labels may encode the channel's carrier frequency, channel's time slot, and possibly the channel's timing advance, as well as its Doppler shift, but the labels may be simple, such as sequential numbers, and the BTS and / or MS may include a stored mapping of channel number labels to assigned characteristics (e.g., channel 1 uses carrier frequency f1 and time slot 0, channel 2 uses carrier frequency f7 and time slot 3, etc.).

[0145] Figure 17 illustrates an example of a satellite footprint range ring / Doppler shift cell. The intersections of the pseudodistance ring and the Doppler shift strip form a footprint grid. Channels can be assigned to the grid cells and range ring / Doppler shift cells.

[0146] Figure 18 illustrates an example of the allocation of the ranging / Doppler offset cells in Figure 17 to specific carrier frequencies and Doppler offset blocks. Logical channel blocks can be associated with one or more carrier frequencies and / or time slots on a TDMA frame that use those carrier frequencies. In Figure 17, the channels are shown with arbitrary channel labels, in this case 1 to 70. They happen to be labeled from bottom to top, i.e., from the most negative Doppler offset to the most positive Doppler offset. Channels 1 to 70 could correspond to channels allocated to each of the eight time slots in a frame using eight carrier frequencies, and six time slots in a frame for another carrier frequency.

[0147] Figure 17 shows how channel numbers are assigned to the grid cells of the satellite footprint. Only the left side of the footprint is shown numbered, but please understand that the twin cells on the right side are also assigned to these channel numbers. The channel assignment table in Figure 18 shows that each channel number corresponds to the Doppler shift strip (D0~D 13 This illustrates a channel assignment scheme in which channels are associated with, assigned to, or allocated to Doppler offset blocks corresponding to channel blocks (b0-b6). Note that in other embodiments, the number of channels may vary depending on how the pseudodistance and Doppler shift of the MS are "bucketed". Multiple channels can be allocated to a grid cell. In the examples in Figures 17 and 18, for simplification, one channel number is allocated to each grid cell. Since the grid cells are symmetric with respect to the satellite's velocity vector, only half of the grid cells are filled with channel allocations. In actual implementations, unfilled grid cells are allocated the same channel number from the grid cell on the opposite side of the contour map. This is because symmetric grid cells exist in different physical locations on the contour map (and in the real world), but they represent the same modification parameters in terms of pseudodistance and Doppler shift from the BTS in orbit.

[0148] Pinching and fraying The "pinch and abrasion" feature of BTS design is useful when the uplink subchannels and downlink subchannels are in the continuous spectrum and the Doppler shift can exceed the signal bandwidth, but these conditions are not necessary to implement the following techniques.

[0149] The table in Figure 18 is a channel allocation matrix, which is used to determine how a BTS in orbit will allocate channels to MSs, assigning them in a manner where adjacent carrier frequencies are assigned to adjacent numbers. When a signal burst is received on RACH, the BTS determines which channel should be assigned to that MS by finding the appropriate grid cell using the calculated Doppler shift and calculated pseudodistance estimates and looking up the MS's channel number in the table. In this example, not all channel blocks (columns in Figure 18) have the same number of actual channels in use or available, as not all channel blocks correspond to pseudodistances that can experience the full range of Doppler shifts. The BTS may have different versions of this table, storing copies of it and using them when allocating channel numbers based on grid cells.

[0150] Figure 19 illustrates the advantages of channel allocation, where channels are assigned in order of grid cells having specific Doppler shifts. Because the spacecraft actively allocates channels based on expected Doppler shifts, it no longer needs to consider a wide range of shifts within the receiving frequency. Instead, the BTS in orbit can instruct the existing MS infrastructure to communicate on a specific carrier frequency, but listen on a slightly shifted carrier frequency depending on how much Doppler shift is expected on that channel. This reduces interference from adjacent carrier frequencies in the spacecraft segment.

[0151] In this particular embodiment, the Doppler shift contours are spaced at 5 kHz intervals, but other intervals can be used. Thus, for each channel assigned to MS, the satellite BTS listens at the carrier frequency which is the average of the maximum and minimum Doppler shifts of the carrier frequency of that channel and checks for data bursts within the time slot assigned to that channel. For example, channel 70 is assigned MS, and the frequency F 70 and time slot TS 70 It should be assumed that they are logically related. The BTS on the spacecraft is TS 70 The uplink signal will be heard from the MS at a carrier frequency of +27.5kHz. With this method, there are no signals with an offset of more than 2.5kHz from the frequency heard by the BTS. On the return link, the BTS in orbit is the TS. 70 By transmitting a burst of the signal at -27.5 kHz, the signal on channel 70 can be transmitted, and therefore the signal is received in MS within reasonable limits of the carrier frequency being heard.

[0152] Figure 19 shows a map of the uplink and downlink carrier frequencies used by the MS and BTS for communication. Specifically, Figure 19 shows the Doppler blocks referenced in Figures 17 and 18, where each Doppler block has a width that scales based on the number of channels they hold. If the channels are allocated in order of increasing carrier frequency, as a function of some known Doppler effects, the uplink signals "wear down" each other, defining the channels that the BTS chooses to listen to. This reduces interference at the BTS in orbit. Instead of "wearing down" the downlink transmission frequencies, they are "pinched" to ensure that the signal has the appropriate carrier frequency when it reaches the MS. Note that the Doppler blocks are referenced in both uplink and downlink frequencies, which implicitly means that each channel has uplink and downlink components. Other modifications are possible.

[0153] Figure 19 shows that the BTS in orbit listens at a frequency slightly worn off compared to the frequency transmitted by the MS. This is a result of the new channel allocation scheme, which reduces the interference and complexity of Doppler shift when communicating with the MS. In downlink operation, the spacecraft transmits on more “pinch” channels, so that the signal reaching the target MS is at the correct frequency. Channel blocks are represented as Doppler blocks, referenced in Figures 17 and 18, and have a width scaled by the number of channels they hold.

[0154] Similarly, it should be noted that channels can be allocated to Doppler blocks in descending order of signal frequency. This scheme reverses the effects of the received and transmitted signals from the perspective of the BTS. It is reasonable to assume that this technique could actually be useful in enhancing the ability to close off uplink signals from the MS. This is because the uplink signals are "pinched" instead of "worn down," as shown in Figure 19. The amount of "pinching" is fairly well understood, so an orbiting BTS will take advantage of this fact to cleverly narrow the bandwidth over which the BTS "listens" to each uplink channel. This means that the received uplink signals are separated below 200 kHz (similar to GSM). In this case, the orbiting BTS can theoretically listen on a narrower channel to reduce noise.

[0155] Some embodiments of the present invention may prefer "worn" or "pinched" channels in both the uplink and downlink subchannels of the BTS. To accommodate this, implementers will allocate channels where the uplink signal frequency increases and the downlink signal frequency decreases. This results in "worn" channels for the uplink receiving and downlink transmitting functions of the BTS. Conversely, channels where the uplink signal frequency decreases and the downlink signal frequency increases result in "pinched" channels for the uplink receiving and downlink transmitting functions of the BTS.

[0156] Figure 19 illustrates channels as boxes, with one example for each Doppler block; however, it should be understood that worn or pinched boxes in Figure 19 may correspond to one or more carrier frequencies and one or more time slots. For example, in the case of Doppler block D9, Figure 18 shows that channels 50–56 are assigned to cells in the strip covered by that Doppler block. Channels 50–56 may represent seven time slots in a frame of one carrier frequency, one time slot in a frame of seven different carrier frequencies, or several other configurations.

[0157] Location discovery In addition to data communication between the BTS and the MS, the BTS can be used to discover locations, i.e., to determine the geographical location of the MS with at least approximate, or sufficient resolution for various applications (e.g., to support remote investigation and relief operations). When a satellite passes through an MS, its BTS determines the grid cells (actually a pair of twin grid cells) of the MS (as described above). When another satellite passes through the same MS, the BTS of that second satellite determines the pair of grid cells within the footprint of that second satellite. If the second satellite is in a different orbit than the first satellite, the symmetry lines of its pseudo-distance ranging ring and Doppler shift contour strips will be somewhat different from those of the first satellite. The BTS assumes that the MS has not moved, or has moved only slightly, on a satellite footprint scale, and that the two pairs of grid cells overlap such that one grid cell of one satellite overlaps with one grid cell of the other satellite, while the other two grid cells do not overlap. From this, the BTS can determine the likely location of the MS.

[0158] This can be used on its own or in combination with other location discovery systems.

[0159] Software-defined radio, dynamic assignment by density. The BTS performs various functions described herein. The BTS may be implemented with commercial software-defined radios or programmed or configured with specific functions provided herein. The software-defined radios may be reprogrammed in orbit to shift around the channel configuration of the BTS channel allocation scheme. This would be valuable if the MSs on the surface are not evenly distributed. For example, if the BTS has a mapping of connected MSs or an expected MS mapping, as illustrated in Figure 20, or if the BTS exhibits a particular Doppler shift range and obtains most of its requests from MSs operating within similar pseudo-ranges, the BTS may prefer more crowded grid cells with more channels. Thus, channel allocation can be proportionally distributed using Doppler shift and pseudo-range data. The right side of Figure 20 shows how many channels can be allocated to each grid cell. Only semicircles are shown, assuming that the satellite footprint is symmetric with respect to the satellite's velocity vector.

[0160] Figure 21 illustrates an example of a channel allocation table that may be used for the allocation and mapping illustrated in Figure 20, where channel allocation is mapped to channels ordered using the channel allocation scheme. To reconfigure a channel to serve a grid cell, the transceiver for that channel is reconfigured with a different time slot synchronization offset than the transmitted TDMA frame, and the transceiver receives an update to the transceiver's configured frequency offset for receiving and transmitting on the uplink carrier and downlink carrier, respectively. Once the channels are reconfigured and remapped to the channel allocation scheme, they may remain in count order (ascending or descending) from the bottom right corner to the top left corner of the channel allocation table, as shown. The channel allocation table may be stored in accessible computer-readable memory so that a processor controlling a software-defined radio can set frequencies and timings according to the channel allocation table.

[0161] In addition to remapping channels to blocks, software-defined radios in orbit can also reconfigure their block mapping. For example, if MSs are densely packed, a BTS can reconfigure its channel allocation scheme with finer intervals of pseudodistance and Doppler shift to improve service, particularly throughput, in specific geographical areas. Furthermore, an orbital BTS can set minimum and maximum time slot synchronization offsets and Doppler compensations for its channels based on minimum and maximum measurements of pseudodistance and Doppler shift, respectively. This allows the BTS to define its satellite footprint grid cells more precisely and allocate channels more efficiently to serve dense pockets of MSs. Finer spacing of Doppler blocks further reduces the impact of Doppler shift on each channel, while finer spacing of pseudodistance range rings increases potential throughput at more specific ring locations to serve denser MSs.

[0162] In orbital processing, known satellite velocities can be leveraged to predict the motion of the satellite footprint, and consequently, the pseudodistance and Doppler shift contours relative to the MS that the satellite will serve. This allows the satellite BTS to predict which pseudodistance and Doppler shift buckets will require channel allocation in the near future and which will not, and this predictability will enable a more accurate execution of the channel allocation scheme reconfiguration. Because there is a certain lead time associated with channel reconfiguration, predictability can be fully utilized to ensure that the downtime of that channel is limited. For example, to account for this channel reconfiguration lead time, the orbital BTS may "juggle" or reserve one or more channels so that the carrier frequencies serving the MS do not have to suddenly drop service due to reconfiguration. Because channels must be configured in ascending or descending frequency order, reconfiguration may occasionally create a domino effect, requiring the reconfiguration of many channels to maintain this critical frequency order in the channel allocation scheme. For example, consider an orbital GSM BTS with access to 80 channels in the GSM spectrum. Assuming the channels are labeled 1 through 124, all odd channels (i.e., 1, 3, 5, 7, etc.) can be configured to serve the MS, while all even channels (i.e., 2, 4, 6, 8, etc.) can be "juggled" or reserved. When the need for reconfiguration arises, the BTS on orbit can reconfigure the "juggled" channels without having to interrupt service on one of the other 62 already configured channels. If a configured channel is no longer serving the MS, that channel can be reserved or recirculated into the "juggled" channel set, and the process itself repeats, maintaining consistent service and limiting channel downtime.

[0163] On-orbit BTSs can be programmed to further enhance the quality of service of such networks using real-time measurements of MS pseudodistance, Doppler shift, and other data (i.e., GPS). Examples include channel reassignment or shifting based on large datasets collected over time and many satellite paths (based on the relatively static location of MS), as well as more dynamic real-time shifting based on changes in MS distribution detected by spacecraft that passed this location immediately before the current spacecraft, or even by the current spacecraft.

[0164] The dynamic channel assignment described above can also be done in a way that allows certain channels to be reserved for specific MS or geographical locations through which the satellite passes. In other words, the Doppler shift and pseudodistance configuration of a particular channel, when plotted over time, is described by a somewhat smooth function that matches the Doppler shift and pseudodistance environment experienced by a particular MS or geographical location over its trajectory. This embodiment can be strategic under conditions where a particular MS on the Earth's surface needs to maintain a locked link with the satellite for a longer period (e.g., minutes rather than seconds) or benefits from such a link.

[0165] Consider the example illustrated in Figure 20, where the connected MS is a "clamp" and may be operating in a remote area. Note that the map only shows half of the satellite footprint because the pseudodistance bucket and Doppler shift bucket are symmetric with respect to the satellite's velocity vector. When a spacecraft collects pseudodistance and Doppler shift data from these users, it can strategically proportionally allocate channel distribution in its channel allocation scheme and, based on this proportional allocation, reprogram its channels to shift their service configurations. Such techniques can also leverage predictive data analytics software. An on-orbit BTS can closely combine historical MS data with GPS navigation data to predict where and when it will cross densely populated customer pockets within its footprint. GPS data from MS actually being served can also be used to further enhance predictive analytics and allocation of channels, as well as tracking applications. This can drive improvements in the quality of service of such networks.

[0166] Figure 22 illustrates the process for determining MS parameters in the RACH process. By measuring the propagation delay from the MS uplink burst, the BTS can calculate the timing advance required for each MS to transmit the burst at the correct time. The RACH process may involve (1) the MS listening to the BCCH when it is stationed on the BTS, (2) the MS user typing a text message and pressing "Send", (3) the MS requesting access to the channel by sending a burst onto the RACH using the information provided on the BCCH, (4) the BTS looking up the channel allocation and responding with the channel allocation and timing advance (bit by bit), and (5) the MS using the timing advance to advance the burst into the allocated time slot and use the allocated frequency carrier.

[0167] In a more schematic example illustrated in Figure 22, the MS requests the allocation of a dedicated signaling channel to perform the call setup, and after the signaling channel is allocated, the call setup request for the MOC, including the TMSI (IMSI) and the last LAI, is forwarded to the VLR. The VLR requests AC via the triple HLR (if necessary). The VLR then begins authentication, encryption initiation, IMEI verification (optional), and TMSI reassignment (optional). If all of this does not result in an error requiring the process to be canceled, the MS sends the setup information (the requested subscriber number and a detailed service description) to the MSC, which requests the VLR to verify (from the subscriber data) whether it can handle the requested services and numbers (or whether there are any limitations that would prevent it from processing the call setup further).

[0168] If the VLR indicates that the call should be handled, the MSC instructs the BSC to allocate a traffic channel to the MS, and the BSC allocates the traffic channel TCH to the MS. The MSC then sets up a connection to the requested number (the incoming number).

[0169] According to one embodiment, the technique described herein is implemented by one or a generalized computing system programmed to perform the technique according to programmed instructions of firmware, memory, other storage, or a combination thereof. A dedicated computing device such as a desktop computer system, portable computer system, handheld device, network device, or any other device incorporating hardwired logic and / or programmed logic can be used to implement the technique.

[0170] For example, Figure 23 is a block diagram illustrating a computer system 2300 in which one embodiment of the present invention may be implemented. The computer system 2300 includes a bus 2302 or other communication mechanism for communicating information, and a processor 2304 coupled to the bus 2302 for processing information. The processor 2304 may be, for example, a general-purpose microprocessor.

[0171] The computer system 2300 also includes main memory 2306, such as random access memory (RAM) or other dynamic storage device, which is connected to bus 2302 for storing information and instructions executed by processor 2304. Main memory 2306 may also be used to store temporary variables or other intermediates while instructions are being executed by processor 2304. Once such instructions are stored in a non-temporary storage medium accessible to processor 2304, it renders the computer system 2300 into a dedicated machine customized to perform the actions specified in the instructions.

[0172] The computer system 2300 further includes a read-only memory (ROM) 2308 or other static storage device coupled to the bus 2302 for storing static information and instructions of the processor 2304. A storage device 2310, such as a magnetic disk or optical disk, is provided and coupled to the bus 2302 for storing information and instructions.

[0173] The computer system 2300 may be connected via bus 2302 to a display 2312, such as a computer monitor, for displaying information to the computer's user. An input device 2314, including alphanumeric and other keys, is connected to bus 2302 to communicate information and instruction selections to the processor 2304. Another type of user input device is a cursor control 2316, such as a mouse, trackball, or cursor directional keys, for communicating directional information and instruction selections to the processor 2304, and for controlling cursor movement on the display 2312. This input device typically has two degrees of freedom on two axes, a first axis (e.g., x) and a second axis (e.g., y), so that the device can pinpoint its position in a plane.

[0174] Computer system 2300 can implement the techniques described herein by using customized hardwired logic, one or more ASICs or FPGAs, firmware, and / or a combination of computer systems to make computer system 2300 a dedicated machine, or by using program logic to program it as such. According to one embodiment, the techniques described herein are performed by computer system 2300 in response to processor 2304 executing one or more sequences of one or more instructions contained in main memory 2306. Such instructions may be read into main memory 2306 from another storage medium, such as storage device 2310. Execution of the sequence of instructions contained in main memory 2306 causes processor 2304 to perform the process steps described herein. In alternative embodiments, hardwired circuits may be used instead of, or in combination with, software instructions.

[0175] As used herein, the term “storage medium” refers to any non-temporary medium that stores data and / or instructions that cause a machine to operate in a particular manner. Such storage medium may include non-volatile and / or volatile media. For example, non-volatile media include optical or magnetic disks such as storage device 2310. Volatile media include dynamic memory such as main memory 2306. For example, common forms of storage media include floppy disks, flexible disks, hard disks, solid-state drives, magnetic tapes, or any other magnetic data storage media, CD-ROMs, any other optical data storage media, any physical media having a pattern of holes, RAM, PROMs, EPROMs, FLASH®-EPROMs, NVRAMs, any other memory chips, or cartridges.

[0176] Storage media are distinct from transmission media, but can be used in conjunction with them. Transmission media are involved in transferring information between storage media. Examples of transmission media include coaxial cables, copper wires, and optical fibers, including wires with bus 2302. Transmission media may also take the form of sound waves or light waves, such as those generated during radio wave and infrared data communications.

[0177] Various forms of media may involve transporting one or more sequences of one or more instructions to the processor 2304 for execution. For example, the instructions may initially be on a magnetic disk or solid-state drive of a remote computer. The remote computer may load the instructions into its dynamic memory and transmit those instructions over a network connection. A local modem or network interface of computer system 2300 can receive the data. Bus 2302 transports the data to main memory 2306, from which the processor 2304 searches for and executes the instructions. Instructions received by main memory 2306 may optionally be stored in storage device 2310 either before or after execution by processor 2304.

[0178] The computer system 2300 also includes a communication interface 2318 connected to bus 2302. The communication interface 2318 provides bidirectional data communication connected to a network link 2320 connected to a local network 2322. For example, the communication interface 2318 may be an integrated services digital network (ISDN®) card, cable modem, satellite modem, or modem for providing data communication connectivity to a corresponding type of telephone line. A wireless link may also be implemented. In any such implementation, the communication interface 2318 transmits and receives electrical, electromagnetic, or optical signals carrying digital data streams representing various types of information.

[0179] Network link 2320 typically provides data communication to other data devices over one or more networks. For example, network link 2320 may provide a connection to a host computer 2324 via a local network 2322, or to data equipment operated by an Internet Service Provider (ISP) 2326. The ISP 2326 then provides data communication services over a worldwide packet data communication network, commonly referred to here as the “Internet” 2328. Both the local network 2322 and the Internet 2328 use electrical, electromagnetic, or optical signals to carry digital data streams. Signals over various networks, as well as signals over network link 2320 and communication interface 2318, that carry digital data to and from the computer system 2300 are examples of forms of transmission media.

[0180] The computer system 2300 can send messages and receive data, including program code, via a network(s), network link 2320, and communication interface 2318. In the internet example, server 2330 can transmit requested code for an application program via the internet 2328, ISP 2326, local network 2322, and communication interface 2318. The received code may be executed by processor 2304 upon receipt and / or stored in storage device 2310 or other non-volatile storage device for later execution.

[0181] The operation of the processes described herein may be carried out in any preferred order unless otherwise indicated herein or expressly denied otherwise by the context. The processes described herein (or variations and / or combinations thereof) may be carried out under the control of one or more computer systems consisting of executable instructions and may be implemented as code (e.g., executable instructions, one or more computer programs, or one or more applications) that is executed collectively by hardware or a combination thereof on one or more processors. The code may be stored on a computer-readable storage medium in the form of a computer program containing multiple instructions that can be executed by one or more processors. The computer-readable storage medium may be non-temporary.

[0182] Unless otherwise specifically stated or explicitly denied by context, conjunctions such as expressions of the form “at least one of A, B, and C” or “at least one of A, B, and C” are generally understood differently by context as being used to indicate that an item, term, etc., may be either A, B, or C, or any non-empty subset of the set A, B, and C. For example, in the example of an exemplary set having three members, the conjunctions “at least one of A, B, and C” and “at least one of A, B, and C” refer to any of the following sets: {A}, {B}, {C}, {A, B}, {A, C}, {B, C}, {A, B, C}. Thus, such conjunctions are generally not intended to implicitly mean that a particular embodiment requires the presence of at least one A, at least one B, and at least one C, respectively.

[0183] Any and all examples provided herein, or any use of exemplary language (e.g., "such as"), is intended solely to further illustrate embodiments of the invention and, unless otherwise asserted, does not constitute a limitation of the scope of the invention. No language herein should be construed as indicating that any unasserted element is essential to the practice of the invention.

[0184] In the aforementioned specification, embodiments of the invention are described with reference to a great many specific details that may vary among implementations. Therefore, this specification and the drawings are to be considered illustrative, not restrictive. The sole and exclusive indicator of the scope of the invention, and what the applicant intends to encompass, is the literal scope and equivalent scope of the set of claims issued from this application, in any specific form including any subsequent amendments, as issued by such claims.

[0185] Those skilled in the art may envision further embodiments after reading this disclosure. In other embodiments, combinations or subcombinations of the inventions disclosed above may be advantageously carried out. For illustrative purposes, examples of component arrangements are shown, and it should be understood that combinations, additions, rearrangements, etc., are intended in alternative embodiments of the invention. Thus, although the invention has been described in terms of exemplary embodiments, those skilled in the art will recognize that a great many modifications are possible.

[0186] For example, the processes described herein can be implemented using hardware components, software components, and / or any combination thereof. Therefore, this specification and the drawings are to be considered illustrative, not restrictive. However, it is clear that various modifications and changes can be made to them without departing from the broader spirit and scope of the invention as described in the claims, and that the invention is intended to encompass all modifications and equivalents within the scope of the following claims.

[0187] All references cited herein, including publications, patent applications, and patents, are incorporated herein by reference to the same extent as they are incorporated herein by reference, with each reference being shown to be incorporated individually and specifically. [Item 1] A multiple access base station having one or more transceivers that handle communications with multiple terrestrial mobile stations, wherein one of the multiple terrestrial mobile stations is configured to anticipate base station communication with a terrestrial cellular base station that (1) is within a limited distance from the terrestrial mobile station and / or (2) is moving at a speed below the limit relative to the terrestrial mobile station, and the multiple access base station is configured to anticipate base station communication with a terrestrial cellular base station that (1) is within a limited distance from the terrestrial mobile station and / or (2) is moving at a speed below the limit relative to the terrestrial mobile station, A data analyzer for analyzing data received by a multiple access base station according to a frame structure, wherein the frame structure defines which time slot is assigned to which of the multiple ground mobile stations, and the frame structure comprises a plurality of slots, each having a zero or non-zero time slot synchronization offset that results in a variable transmission delay due to the distance from the multiple access base station to the multiple ground mobile stations, A signal timing module that determines signal timing adjustments to the frame structure of a transmission signal to a ground mobile station based on the base-to-mobile distance between the multiple access base station and the ground mobile station, wherein the base-to-mobile distance exceeds the limit distance, A multiple access base station comprising: a programmable radio capable of transmitting communications from the multiple access base station to the ground mobile station using a multiple access protocol, and taking into account the signal timing adjustment, such that the communications are compatible with, or appear to, communications between a ground cellular base station and the ground mobile station, even though the base-to-mobile distance exceeds the limit distance; and a multiple access base station comprising a programmable radio. [Item 2] A multiple access base station as described in item 1, further adapted to communicate with the aforementioned multiple terrestrial mobile stations, wherein the aforementioned multiple terrestrial mobile stations include cellular telephone handsets, smartphones, and connected devices. [Item 3] A multiple access base station according to item 1 or 2, wherein the aforementioned limited distance is 120 kilometers, and the base-to-mobile distance exceeds 120 kilometers. [Item 4] A multiaccess base station according to item 1 or 2, wherein the multiaccess protocol is the LTE protocol, the limited distance is 100 kilometers, and the base-to-mobile distance exceeds 100 kilometers. [Item 5] A multiaccess base station according to item 1 or 2, wherein the multiaccess protocol is the LTE-IoT protocol, the limited distance is 40 kilometers, and the base-to-mobile distance exceeds 40 kilometers. [Item 6] A multiple access base station according to any one of items 1 to 3, wherein the multiple access protocol is one of the following: a CDMA-based protocol, an LTE protocol, a GSM® protocol, an OFDMA-based protocol, an FDMA-based protocol, a TDMA-based protocol, an EGPRS protocol, or an EDGE protocol. [Item 7] The multiple access base station described in any one of items 1 to 6, wherein the multiple access base station is an orbital base station operating within the Earth's orbit. [Item 8] A multiple access base station as described in item 7, wherein the aforementioned limited distance is 120 kilometers, and the base-to-mobile distance of the multiple ground mobile stations is approximately 500 kilometers to approximately 750 kilometers. [Item 9] The multiple access base station described in any one of items 1 to 6 is a base station capable of operating in the Earth's atmosphere and includes being mounted on or inside one or more of an airplane, a drone, and / or a balloon. [Item 10] A multiple access base station as described in item 9, wherein the aforementioned limited distance is 120 kilometers and the base-to-mobile distance exceeds 120 kilometers. [Item 11] A multiple access base station according to any one of items 1 to 10, further comprising signal allocation logic for allocating the capacity of the multiple access base station, distributed across multiple time slots, multiple carrier frequencies, multiple orthogonal subcarriers, and / or multiple code sequences, to the multiple ground mobile stations, including the ground mobile stations. [Item 12] The programmable radio can further listen to communications from the terrestrial mobile station using a multiple access protocol, and the multiple access base station, A range calculator that determines the base-to-mobile distance of each of the multiple ground mobile stations, which is the distance from the multi-access base station to the ground mobile station. A receiving timing module that determines the timing of the received signal of the ground mobile station relative to the frame structure based on the distance between the base station and the mobile station of the ground mobile station, The multiple access base station according to item 1, further comprising: an input signal assigner that assigns listening time slots within the frame structure to listen to communications from the ground mobile station, wherein the listening time slots are timed based on the base-to-mobile distance of the ground mobile station, and the listening time slots are one of a plurality of time slots, and the plurality of time slots are variably delayed within the frame structure to take into account the multiple access base station handling communications from a plurality of ground mobile stations having a plurality of base-to-mobile distances. [Item 13] Multiple access base stations according to item 12, wherein the multiple time slots are variably delayed within the frame structure to take into account the multiple ground mobile stations having multiple base-mobile distances by assigning each of the multiple different base-mobile distance ranges to each of the multiple channel blocks. [Item 14] The multiple access base station according to item 13, wherein the multiple access base station is an orbital base station operating in Earth's orbit, and the distance range between the multiple different base stations and mobile stations collectively covers a slant range from the zenith distance to the minimum elevation distance, the zenith distance being the distance between a ground mobile station and the zenith position of the satellite hosting the multiple access base station, and the minimum elevation distance being the distance between the ground mobile station and the position of the satellite when the ground mobile station enters the satellite's design footprint. [Item 15] Multiple access base stations as described in item 14, wherein the distance range between each of the multiple different base stations and mobile stations is approximately 34 to 35 kilometers, and the difference between the zenith distance and the minimum elevation distance is 210 to 250 kilometers. [Item 16] Multiple access base stations as described in item 14 or 15, wherein the design footprint of the satellite is circular, elliptical, or rectangular and is independent of the antenna function and / or the shape of the antenna beam, or is the antenna function and / or the shape of the antenna beam. [Item 17] A multiple access base station having one or more transceivers that handle communications with multiple terrestrial mobile stations, wherein the configuration anticipates base station communication with a terrestrial cellular base station that (1) is within a limited distance from the terrestrial mobile station and / or (2) is moving at a speed below the limit relative to the terrestrial mobile station, and the multiple access base station is A data analyzer that analyzes data received by a multiple access base station according to a frame structure that defines which time slot is assigned to which of the multiple ground mobile stations, and according to a multiple access protocol that predicts the ground mobile station will receive signals at specified frequencies and transmit signals at specified frequencies, For each of the aforementioned multiple ground mobile stations, a Doppler deviation calculator determines the Doppler deviation of each ground mobile station caused by the speed of each ground mobile station relative to the multi-access base station. A channel allocation module that assigns each of the plurality of terrestrial mobile stations to a channel block within a plurality of channel blocks, wherein each channel block has a terrestrial frequency and a Doppler frequency offset, A signal modulator that modulates a signal to a ground mobile station at the ground frequency using the Doppler frequency offset, wherein the Doppler frequency offset at least substantially corresponds to the expected Doppler shift in the signal transmitted to the ground mobile station due to the relative movement of the multiple access base station and the ground mobile station, and so that the ground mobile station receives the signal at the ground frequency. A multiple access base station comprising: a programmable radio capable of receiving communications from the terrestrial mobile station using the multiple access protocol and taking into account the Doppler frequency offset of the terrestrial mobile station, such that the communications are compatible with, or appear to be compatible with, communications between a terrestrial cellular base station and the terrestrial mobile station, even though the speed of the terrestrial mobile station to the multiple access base station exceeds the speed limit; [Item 18] The speed of the ground mobile station relative to the multi-access base station is a result of the multi-access base station being in Earth's orbit, and the Doppler frequency offset changes in increments of 5 kilohertz, as described in item 17. [Item 19] A multiple access base station as described in item 17 or 18, further adapted to communicate with the aforementioned multiple terrestrial mobile stations, wherein the aforementioned multiple terrestrial mobile stations include cellular telephone handsets, smartphones, and connected devices. [Item 20] The multiple access base station described in any one of items 17 to 19, wherein the multiple access base station is an orbital base station operating within Earth's orbit. [Item 21] The multiple access base station described in any one of paragraphs 17 to 19 is a base station capable of operating in the Earth's atmosphere and includes being mounted on or inside one or more of an airplane, a drone, and / or a balloon. [Item 22] A multiple access base station according to any one of items 17 to 21, further comprising signal allocation logic for allocating the capacity of the multiple access base station, distributed across multiple time slots, multiple carrier frequencies, multiple orthogonal subcarriers, and / or multiple code sequences, to the multiple ground mobile stations, including the ground mobile stations. [Item 23] A multiple access base station according to any one of items 17 to 22, wherein each of the plurality of channel blocks has an uplink subchannel and a downlink subchannel, each having an uplink subchannel and a downlink subchannel, and the channel blocks are allocated such that adjacent channel blocks are allocated to adjacent Doppler frequency offsets. [Item 24] A multiple access base station having one or more transceivers that handle communications with multiple terrestrial mobile stations, wherein the configuration anticipates base station communication with a terrestrial cellular base station that (1) is within a limited distance from the terrestrial mobile station and / or (2) is moving at a speed below the limit relative to the terrestrial mobile station, and the multiple access base station is A data analyzer for analyzing data received by a multiple access base station according to a frame structure and further according to a multiple access protocol, wherein the frame structure defines which time slot is assigned to which of the multiple ground mobile stations, and comprises a plurality of slots, each having a zero or non-zero time slot synchronization offset resulting in a variable transmission delay due to the distance from the multiple access base station to the multiple ground mobile stations, and the multiple access protocol predicts that the ground mobile stations will receive signals at a specified frequency and transmit signals at a ground frequency, and receive signals at a Doppler frequency offset, and the multiple access protocol identifies channel blocks within a plurality of channel blocks, each channel block having a specified ground frequency and a specified time slot, A signal timing module that determines signal timing adjustments to the frame structure of a transmission signal to a ground mobile station based on the base-to-mobile distance between the multiple access base station and the ground mobile station, wherein the base-to-mobile distance exceeds the limit distance and a specified signal timing adjustment is assigned to each channel block. For each of the aforementioned multiple ground mobile stations, the Doppler deviation of the ground mobile station caused by the speed of the ground mobile station relative to the multi-access base station is determined, and a specified Doppler frequency offset is assigned to each channel block, and a Doppler deviation calculator is used. A dynamic channel assigner that assigns each of the plurality of ground mobile stations to a designated channel block within the plurality of channel blocks based on a designated signal timing adjustment and a designated Doppler frequency offset of the channel block, wherein the number of channels in the designated channel block corresponds to the number of the plurality of ground mobile stations that have or are expected to have the designated signal timing adjustment and the designated Doppler frequency offset. A signal modulator that modulates a signal to a ground mobile station at the ground frequency using the Doppler frequency offset, wherein the Doppler frequency offset corresponds at least substantially to the expected Doppler shift in the signal transmitted to the ground mobile station due to the relative movement of the multiple access base station and the ground mobile station, and so that the ground mobile station receives the signal at the ground frequency. A multiple access base station comprising: a programmable radio capable of receiving communications from the terrestrial mobile station using the multiple access protocol and taking into account the Doppler frequency offset of the terrestrial mobile station, such that the communications are compatible with, or appear to, communications between a terrestrial cellular base station and the terrestrial mobile station, even though the base-to-mobile distance exceeds the limit distance and the speed of the terrestrial mobile station relative to the multiple access base station exceeds the limit speed; and a multiple access base station comprising a programmable radio capable of taking into account the Doppler frequency offset of the terrestrial mobile station, so as to be compatible with, communications between a terrestrial cellular base station and the terrestrial mobile station, even though the base-to-mobile distance exceeds the limit distance and the speed of the terrestrial mobile station relative to the multiple access base station exceeds the limit speed. [Item 25] The speed of the ground mobile station relative to the multi-access base station is a result of the multi-access base station being in Earth's orbit, and the Doppler frequency offset changes in increments of 5 kilohertz, as described in item 24. [Item 26] A multiple access base station as described in item 24 or 25, further adapted to communicate with the aforementioned multiple terrestrial mobile stations, wherein the aforementioned multiple terrestrial mobile stations include cellular telephone handsets, smartphones, and connected devices. [Item 27] The multiple access base station described in any one of items 24 to 26, wherein the multiple access base station is an orbital base station operating within Earth's orbit. [Item 28] The multiple access base station described in any one of paragraphs 24 to 26 is a base station capable of operating in the Earth's atmosphere and includes being mounted on or inside one or more of an airplane, a drone, and / or a balloon. [Item 29] A multiple access base station according to any one of items 24 to 28, further comprising signal allocation logic for allocating the capacity of the multiple access base station, distributed across multiple time slots, multiple carrier frequencies, multiple orthogonal subcarriers, and / or multiple code sequences, to the multiple ground mobile stations, including the ground mobile stations.

Claims

[Claim 1] A multiple access transceiver configured to communicate along a communication path that passes through at least an orbit around the Earth between the multiple access transceiver and a plurality of ground mobile stations, including at least a first ground mobile station. A data analyzer that analyzes the data received by the aforementioned multi-access transceiver into a structure suitable for a frame structure predetermined in the multi-access protocol, A Doppler deviation calculator for each of the aforementioned multiple terrestrial mobile stations, which determines the respective Doppler deviations caused by the speed of each terrestrial mobile station in the communication path relative to the multiple access transceiver in the communication path, A channel allocation module that assigns each of the aforementioned plurality of ground mobile stations to a channel block within a plurality of channel blocks, wherein each channel block is configured according to the Doppler frequency offset, A signal modulator that modulates the frequency of the signal to the first ground mobile station to a frequency obtained by adding the Doppler frequency offset to the ground frequency at which the first ground mobile station receives the signal, wherein the Doppler frequency offset is an amount obtained by inverting the sign of the expected Doppler deviation in the signal transmitted to the first ground mobile station due to the relative movement of the first ground mobile station and the multiple access transceiver, and therefore the first ground mobile station receives the signal at the ground frequency, Equipped with, Even if the speed of the first terrestrial mobile station to the multiple access transceiver exceeds the speed limit specified in the multiple access protocol, the communication appears to the first terrestrial mobile station as being compatible with the communication between the terrestrial cellular base station and the first terrestrial mobile station. Multiple access transceiver.

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