Systems and methods for adaptive communication

Abstract

The adaptive satellite communications system uses an interference-aware scheduler to select slot transmission parameters for transmitting messages. When scheduling transmission of a message by a particular terminal, the scheduler determines interference parameters of any external communications systems relative to the transmitter location and intended transmission time period. The scheduler can then use this to estimate whether a particular combination of slot transmission parameters is likely to cause interference and then adjust the slot transmission parameters to reduce the potential interference. The scheduler may use an optimization method configured to select slots subject to constraints regarding latency, probability of transmission failure / success, and interference.

Description

[Technical Field]

[0001] Prior literature This application claims priority to Australian Provisional Patent Application No. 2020901049, filed on 3 April 2020, entitled "SYSTEM AND METHOD FOR ADAPTIVE COMMUNICATIONS," the entire contents of which are incorporated herein by reference.

[0002] Embedding by reference This application refers to the following patent applications. PCT / AU2013 / 000895, filed on August 14, 2013, entitled "Channel Allocation in a Communication System," claims priority to Australian Provisional Patent Application No. 2012903489, filed on August 14, 2012. PCT / AU2013 / 001078, filed on September 20, 2013, entitled "Communication System and Method," claims priority to Australian Provisional Patent Application No. 2012904130, filed on September 21, 2012. PCT / AU2013 / 001079, filed on September 20, 2013, is titled "MULTI-ACCESS COMMUNICATION SYSTEM" and claims priority from Australian Provisional Patent Application No. 2012904145, filed on September 21, 2012. PCT / AU2014 / 000826, filed on August 21, 2014, entitled "A MULTIUSER COMMUNICATIONS SYSTEM," claims priority to Australian Provisional Patent Application No. 2013903163, filed on August 21, 2013. PCT / AU2015 / 000743, filed on December 9, 2015, is titled "Multicarrier Communications System" and claims priority from Australian Provisional Patent Application No. 2014904976, filed on December 9, 2014. PCT / AU2017 / 000058, filed on February 24, 2017, entitled "Terminal Scheduling Method in Satellite Communication System," claims priority to Australian Provisional Patent Application No. 2016900685, filed on February 25, 2016. PCT / AU2017 / 000108, filed on May 16, 2017, entitled "Position Estimation in a Low Earth Orbit Satellite Communications System," claims priority to Australian Provisional Patent Application No. 2016901913, filed on May 20, 2016. PCT / AU2017 / 000286, filed on December 21, 2017, entitled "SYSTEM AND METHOD FOR GENERATING EXTENDED SATELLITE EPHEMERIS DATA," claims priority to Australian Provisional Patent Application No. 2016905314, filed on December 22, 2016. PCT / AU2018 / 000151, filed on August 28, 2018, entitled "SYSTEM AND METHOD FOR PREDICTION OF COMMUNICATIONS LINK QUALITY," claims priority to Australian Provisional Patent Application No. 2017903470, filed on August 28, 2017.

[0003] The contents of each of these applications are incorporated herein by reference in their entirety.

[0004] This disclosure relates to wireless communication systems. In certain forms, this disclosure relates to reducing interference between multiple wireless communication systems using a shared physical communication medium. [Background technology]

[0005] Multiplex communication systems 10 operating using a shared physical communication medium (channel) 13 may interfere with each other, degrading system performance. System operators may coordinate the use of the medium at a high level, such as by permanently retaining segments of the radio frequency spectrum. However, this can lead to inefficient use, especially if the use of the medium is intermittent or transient. For example, in a low Earth orbit (LEO) satellite system 1, communication between the satellite access node 10 and the terminal 20 occurs only when the terminal is within its field of view 12 as the satellite 10 passes overhead.

[0006] Figure 1A shows a schematic diagram of two satellite communication systems A and B having non-overlapping fields of view 12 according to one embodiment. In this embodiment, terminals 20 are distributed on Earth (e.g., on land, underwater, or in the air), and access nodes 10 are LEO satellites. Terminals 20 of group A (denoted as TA.n) communicate with satellite 20 denoted as SA.1 from system A. Terminals 24 of group B (denoted as TB.n) communicate with satellite 20 denoted as SB.1 from system B. Systems A and B may be operated independently by different service providers using different communication protocols. Thus, here we say that system B is outside of system A, and vice versa. They may use a common communication medium (channel) 13 having overlapping slots. In this example only one satellite 20 is shown for each communication system 1, but generally each system may have multiple access nodes 20, including satellites distributed around the Earth, and may also include high-altitude platforms and ground access nodes. For clarity, gateway terminals and ground stations have been omitted, and only one satellite 20 is shown for each system.

[0007] Communication between terminal 20 and satellite 10 has an uplink component 16 and a downlink component 18, as shown in Figure 1A. The uplink is defined as the transmission from terminal to satellite, and the downlink is defined as the transmission from satellite to terminal. Signals from system A (transmissions from terminal or satellite) are considered interference to system B, and vice versa. As shown in Figure 1A, the respective satellite fields of view 12 do not overlap, and the systems can operate simultaneously without causing interference to each other.

[0008] Figure 1B shows a schematic diagram of two satellite communication systems 10 having overlapping portions 30 of their fields of view 12 according to one embodiment. In this example, terminal TA.1 is within the field of view of both satellites SA.1 and SA.2. When systems A and B use (partially) overlapping slots, a receiver on SB.1 may be a victim of interference 32 caused by transmissions from TA.1, and a receiver on TA.1 may be a victim of interference 32 caused by transmissions from SB.1.

[0009] One high-level approach to coordinating these two satellite systems is to permanently allocate radio spectrum to each satellite system. However, this is often very wasteful, especially in the case of LEO satellite systems, as the satellites within the allocated system are only transiently located on fixed points on the Earth's surface and do not provide continuous 24 / 7 coverage. Furthermore, different countries may operate different spectrum allocation / licensing procedures, and therefore, permanent allocation (or licensing) may not be available in all countries where the terminals are located (i.e., where the satellites serve). In addition, as more satellite systems are launched, permanent allocation can lead to equity issues.

[0010] Therefore, there is a need for methods for communication systems that adapt their operation to efficiently utilize shared communication media, or at least provide a useful alternative to existing methods. [Overview of the project] [Means for solving the problem]

[0011] According to a first aspect, a method is provided for scheduling transmissions in a wireless communication system comprising one or more access nodes and a plurality of terminals, wherein the one or more access nodes comprises at least one access node having a moving field of view toward the plurality of terminals, and the method is as follows: Receiving one or more messages in order to send, Regarding the transmission location, the following is determined: one or more interference parameters of one or more external communication systems during the transmission period. The process includes selecting one or more slot transmission parameters for transmitting one or more messages during a transmission time period, determining the likelihood that the selected one or more slot transmission parameters are likely to cause interference to one or more external communication systems using one or more interference parameters, and, if the likelihood of interference is determined to be high, scheduling the transmission of one or more messages in one or more slots of a plurality of slots by adjusting one or more of the slot transmission parameters to determine whether the changes result in an acceptable reduction of interference.

[0012] In one embodiment, determining one or more interference parameters includes storing a slot reservation map that stores one or more reserved slots for one or more external communication systems, and determining the likelihood that a selected one or more slot transmission parameters are likely to cause interference using one or more interference parameters includes examining any reserved slot associated with any of the detected or estimated one or more external communication systems and preventing the selection of a reserved slot.

[0013] In one embodiment, determining one or more interference parameters includes storing one or more reserved slots for one or more external communication systems and storing a slot reservation map in which one or more of the one or more reserved slots are reserved per satellite, and determining the likelihood that the selected one or more slot transmission parameters are likely to cause interference using one or more interference parameters includes detecting or estimating whether a satellite associated with a reserved slot is detected or estimated to be present during the transmission time period, and if a satellite is detected or estimated to be present, preventing the selection of the reserved slot.

[0014] In one embodiment, determining one or more interference parameters includes storing one or more reserved slots for one or more external communication systems and storing a slot reservation map in which one or more of the one or more reserved slots are reserved for each geographical area, and determining the likelihood that a selected one or more slot transmission parameters are likely to cause interference using one or more interference parameters includes estimating the location of a transmitter during the transmission period, determining whether the transmitter is located within the geographical area associated with one or more reserved slots, and preventing the allocation of each of the reserved one or more slots.

[0015] In one form, determining one or more interference parameters is related to one or more receivers in one or more external communication systems. threshold Determining the likelihood that one or more selected slot transmission parameters are likely to cause interference, including determining the value of one or more interference parameters, estimating the elevation angle of the receiver in one or more external communication systems during the transmission time period, and the elevation angle relative to the receiver threshold This includes determining whether the value exceeds a certain threshold.

[0016] In one embodiment, determining one or more interference parameters of one or more external communication systems includes detecting beacon signals from transmitters in one or more external communication systems and determining one or more beacon signal characteristics used to determine whether they are likely to cause interference.

[0017] In one form, determining one or more interference parameters of one or more external communication systems involves receiving one or more transmissions from transmitters in one or more external communication systems on a media adjustment channel, and providing information that helps share the medium, including one or more of the following: elevation angle, signal-to-noise ratio, interference level, output level, link quality estimate, channel state estimate, or acceptable interference level. In a further form, the information is used to update the slot reservation map.

[0018] In one form, with respect to the transmission location, determining one or more interference parameters of one or more external communication systems during the transmission time period is: To acquire ephemeris data for one or more satellite receivers in one or more external communication systems, This includes obtaining an estimated value of the transmitter's position during the transmission period. Determining the likelihood that one or more selected slot transmission parameters are likely to cause interference using one or more interference parameters is equivalent to estimating the likelihood of interference with one or more receivers in one or more external communication systems using terminal location, ephemeris data, and transmission time period.

[0019] In one form, determining the likelihood that one or more selected slot transmit parameters are likely to cause interference using one or more interference parameters involves estimating a time-varying estimate of interference over a transmit time period and selecting one or more slot transmit parameters, and adjusting one or more of the slot transmit parameters is done by using an optimization method to determine one or more slot transmit parameters that minimize or constrain the total interference.

[0020] In a further form, determining the likelihood that one or more selected slot transmit parameters are likely to cause interference using one or more interference parameters further includes estimating the probability of an error in which the transmission is not received at the target receiver, and latency, and determining one or more slot transmit parameters by minimizing one of the following: a time-varying estimate of interference over the transmission time period, the probability of an error in which the transmission is not received at the target receiver, and latency under the influence of one or more constraints on the time-varying estimate of interference over the transmission time period, and the probability of an error in which the transmission is not received at the target receiver and latency, and the optimization is performed jointly for all slot transmit parameters.

[0021] In a further form, the optimization is performed under the influence of throughput constraints. In a further form, the throughput constraints include restricting the transmission time to a discrete grid of width W during the transmission time period.

[0022] In one form, latency is the total expected latency. In another form, latency constraints are based on percentile probabilities.

[0023] In one form, the method involves using one or more interference parameters to determine the likelihood that one or more selected slot transmit parameters are likely to cause interference, further including estimating the probability of an error where the transmit is not received at the target receiver, and latency. The optimization method uses a greedy scheduling algorithm that sequentially selects transmit times so that the transmit is scheduled at a time that reduces the probability of latency and error while minimizing the increase in interference.

[0024] In a further form, greedy scheduling algorithms minimize average latency and total external interference.

[0025] In one configuration, one or more slot parameters include any degree of transmission freedom.

[0026] In one form, the degrees of freedom of transmission include one or more of the following: time, frequency, antenna polarization, spreading sequence, transmit power, or spatial partitioning.

[0027] In one form, the method further includes obtaining an estimate of the transmitter's position during the transmission time period, determining the likelihood that one or more selected slot transmission parameters are likely to cause interference using one or more interference parameters, and determining whether a transmission in a slot is likely to cause interference using the estimate of the transmitter's position.

[0028] In one embodiment, the method is implemented at a terminal device. In another embodiment, the method is implemented at a satellite access node. In another embodiment, the communication system further comprises one or more gateways, and the method is implemented at at least one gateway.

[0029] In one configuration, at least one of the access nodes is a satellite access node or a high-altitude platform.

[0030] According to a second embodiment, a terminal device is provided comprising an uplink baseband transmitter and an RF front end, and a scheduler configured to carry out the method of the first embodiment.

[0031] According to a third aspect, an access node device is provided, comprising a downlink baseband transmitter and an RF front end, and a scheduler configured to implement the method of the first aspect.

[0032] According to a fourth aspect, a gateway device is provided comprising an uplink baseband transmitter and an RF front end, and a scheduler configured to implement the method of the first aspect.

[0033] According to a fifth aspect, a communication system is provided which comprises a core network component having one or more terminal devices, one or more satellite access nodes, and one or more gateways, and is configured to implement the method of the first aspect, wherein the implementation is distributed across the system.

[0034] Embodiments of this disclosure will be discussed with reference to the attached drawings. [Brief explanation of the drawing]

[0035] [Figure 1A] This is a schematic diagram of two satellite communication systems having non-overlapping fields of view, according to one embodiment.

[0036] [Figure 1B] This is a schematic diagram of two satellite communication systems having overlapping fields of view, according to one embodiment.

[0037] [Figure 2A] This is a flowchart of a method for selecting slot parameters according to one embodiment.

[0038] [Figure 2B]This is a block diagram of a scheduler according to one embodiment.

[0039] [Figure 2C] This is a block diagram of a terminal and access node according to one embodiment.

[0040] [Figure 3] This is a schematic diagram of a slot scheduler according to one embodiment.

[0041] [Figure 4] This is a schematic diagram of a satellite communication system 1 according to one embodiment. [Modes for carrying out the invention]

[0042] In the following description, the same reference numerals throughout the drawings refer to the same or corresponding parts.

[0043] Referring next to Figure 2A, a flowchart of a method for selecting a slot transmission parameter 100 according to one embodiment is shown. The method may be implemented in the scheduler module of a terminal 20, an access node 10, or distributed across a communication system 1, which includes a scheduler 440 in the core network 400, and associated scheduler modules in the access node 10 and terminal 20 that can communicate with a central scheduler 440 (for example, as shown in Figure 4). The system may comprise a plurality of access nodes 10, at least one of which has a moving field of view to a plurality of terminals (for example, an access node located on a satellite or high-altitude platform). The access nodes 10 and terminal 20 communicate through a shared communication medium 13 according to one embodiment. Similarly, an access node may also communicate with a gateway (i.e., a ground station), and the method described herein may be used to schedule transmissions between the access node and the gateway. Similarly, if a terminal and / or gateway is in motion and the terminal comes within range of the gateway, the terminal and gateway may also schedule transmissions using the methods described herein while minimizing interference with other communication systems. Similarly, if a gateway is in motion and provides connectivity to an access node, for example, if a satellite or high-altitude platform-based gateway provides backhaul connectivity to a ground access node, the gateway and access node may also schedule transmissions using the methods described herein while minimizing interference with other communication systems.

[0044] A shared physical communication medium 13 may be divided into a number of channels (or slots). These channels may be time slots in a time-division multiplex access system, frequency slots in a frequency-division multiplex access system, subcarriers in an orthogonal frequency-division multiplex access system, or more general slots such as spreading sequences in a code-division multiplex access system. Transmit power and antenna polarization provide further degrees of freedom for defining slots. Another degree of freedom may be supplied through spatial multiplexing in a spatial-division multiplex access system. More generally, slots may be a mixture of any of these. A slot corresponds to some subset of the system's total degrees of freedom (including degrees of freedom provided by using multiple transmit and / or receive antennas). Regardless of the underlying method for dividing the medium into channels, these channels will be referred to as “slots.” Selecting slot transmit parameters involves selecting one or more slot parameters (e.g., time or frequency slots) or transmit degrees of freedom (e.g., transmit power, polarization, time, etc.). It is a combination of parameters that defines a unique transmit slot. Furthermore, the slots do not necessarily have to be orthogonal, but in many examples, they are not required to be orthogonal or to have regular boundaries, and may be unevenly distributed, for example, in terms of time or frequency. In one embodiment, the communication system may be a communication system such as that described in international patent application PCT / AU2013 / 001078, filed on September 20, 2013, entitled "Communication System and Method." (However, it should be understood that the Method is not limited to this communication system.)

[0045] In this embodiment, one or more messages are provided to the scheduler for transmission (101). Next, interference parameters of one or more external communication systems are determined for a specific location and during a transmission time period (102). Determining interference parameters may include detecting, estimating, and / or acquiring interference parameters. The presence of one or more receivers in one or more external communication systems may be detected or estimated, for example, based on local or received data or signals. As described later, detection may be based on the detection of beacon signals or medium adjustment channels by the transmitter, or the location of satellites in the external communication systems (which may be under the influence of interference 32 from transmissions by the transmitter) may be estimated using ephemeris data. The scheduler is configured to schedule the transmission of one or more messages in one or more slots of a plurality of slots by selecting one or more slot transmission parameters for transmitting one or more messages during a transmission time period. Scheduling includes using one or more interference parameters to determine the likelihood that one or more selected slot transmit parameters are likely to cause interference to one or more external communication systems, and if it is determined that interference is likely, adjusting one or more of the slot transmit parameters to determine whether the change will result in an acceptable reduction of interference (103). Selecting slot transmit parameters may include adjusting slot degrees of freedom, such as selecting different slot degrees of freedom, or reducing the transmit power or selecting different polarizations to reduce interference. In other words, if the scheduler estimates that a particular slot containing a particular combination of slot parameters is likely to cause interference, the scheduler may change one or more of the slot parameters to determine whether the change will result in an acceptable reduction of interference.In some embodiments, selection and adjustment may be carried out using an optimization method that jointly selects all slot transmission parameters to minimize interference or mitigate performance degradation of other systems. As outlined below, the method may be implemented according to various embodiments and may be implemented by a terminal transmitting to an access node on the uplink, or by an access node transmitting to one or more terminals on the downlink.

[0046] Figure 2B is a block diagram of a scheduler according to one embodiment. The scheduler may be implemented as software code or instructions that run on a real-time processor module, FPGA, and / or ASIC device at a terminal or access node. The scheduler 210 receives one or more messages 201 to be sent during the transmission time period.

[0047] The scheduler may also receive or acquire transmitter data 220, such as available slot transmit parameters 222 (i.e., transmit degrees of freedom), transmitter position (or location) 224 and / or time 226. In some embodiments, the transmitter position, or approximate transmitter position relative to at least one or more satellite receivers, may be estimated or determined during the transmit time period (transmit window). The terminal may use a stored location, for example, if the terminal is a stationary terminal pre-programmed at the installation location, or if the terminal has not moved or has not moved more than a threshold amount since the last acquisition of a position estimate. Alternatively, the terminal may include a GNSS receiver or some position determination module that enables it to estimate its own location. In another alternative, the location of the terminal or satellite may be estimated as described in international patent application PCT / AU2017 / 000108, filed on 16 May 2017, entitled "Position Estimation in a Low Earth Orbit Satellite Communications System." In the case of a satellite-based receiver, the terminal may estimate the satellite's location using ephemeris data. This ephemeris data (i.e., orbital elements) may be provided as two-row orbital elements (TLEs) that model the satellite's orbit and may be transmitted by the satellite or another transmitter and stored by the terminal. In some embodiments, the terminal may calculate or store extended ephemeris data relating to the satellite using the method described in International Patent Application PCT / AU2017 / 000286, filed on 21 December 2017, entitled "SYSTEM AND METHOD FOR GENERATING EXTENDED SATELLITE EPHEMERIS DATA". This extended ephemeris data may be valid for a period of time of more than one year.

[0048] The scheduler is configured to adapt its operation when it determines the presence of an external system (for example, by direct detection, estimation, or acquisition), for example, in the example shown in Figure 1B, TA.1 of system A is also in the field of view of satellite SB.1 of external system B. The terminal may use ephemeris data in combination with knowledge of the transmitter's location and time to estimate the presence of the satellite, or the satellite may transmit a beacon 34 signaling its presence in its field of view to the terminal using a method such as that described in international patent application PCT / AU2013 / 001079 filed on September 20, 2013, entitled "Multi-Access Communications System". Such a beacon 34 may be transmitted using known techniques on a channel cooperatively shared by systems A and B, and possibly other systems, which is referred to here as the medium coordination channel 232. The media adjustment channel 232 may also be used to transmit information that helps share the medium, such as link quality, channel status, signal-to-noise ratio, interference level, output level, etc. Beacon signal characteristics may also be used as input by the terminal to estimate the likelihood of interference. For example, the terminal may use the received signal strength metric derived from the beacon to estimate the channel loss between the terminal and the satellite and to estimate the likelihood of interference from an external satellite. Some systems may transmit beacon signals without a dedicated media adjustment channel, while other systems may use the media adjustment channel without a beacon.

[0049] When the presence of one or more external systems is detected, the terminal scheduler applies the use of a slot on the shared medium. In one embodiment, the terminal ceases to use a slot reserved for use by an external system. This information may be obtained from a slot reservation map 212 stored locally in terminal memory, which may be updated from time to time (e.g., via update 236). The slot reservation map includes slot reservation information for uplinks, downlinks, or both. A slot is considered by the scheduler to be likely to cause interference to one or more external communication systems, and therefore the scheduler prevents the allocation of the reserved slot or, in other ways, selects one or more slot parameters (i.e., slot degrees of freedom) to mitigate the interference. A slot may be reserved on a per-satellite basis, in which case allocation is prevented only if the associated satellite is detected or presumed to exist. A slot may also be reserved on a per-geographical area basis, in which case allocation is prevented if it is determined that the transmitter is presumed to be located within the respective geographical area (e.g., presumed via GPS). In some embodiments, this can be mitigated, and the slot reservation map may store information regarding the probability or likelihood of interference. Therefore, the scheduler may adjust the transmitter behavior (i.e., slot transmit parameters) to avoid interference, for example, by reducing the transmit power. The scheduler may attempt to minimize the transmit power while maintaining a value considered high enough to achieve a certain probability of successful reception, and / or attempt to select a transmit power considered low enough that interference into one or more external communication systems is unlikely, or at least below a threshold. The scheduler may select the slot transmit parameters using various optimization methods.

[0050] The slot reservation map 212 may be updated by one or more satellites via a media coordination channel, or, for example, via another communication link to the terminal if the terminal also has ground or secondary satellite communication capabilities. The slot reservation map 212 may depend on the geographical location of the terminal (or transmitter), i.e., reservations are per geographical region, and what applies in one geographical region differs from what applies in another. The slot reservation map 212 may reserve slots at the system level or at the subsystem level, such as per satellite. In one embodiment, the slot reservation map may divide a shared spectrum resource among multiple systems and, if an external system detects the presence or potential presence of a satellite during a transmission period, notify the terminal to free up the spectrum reserved for that system.

[0051] In another embodiment, the slot reservation map may encompass reservation information for multiple satellites, allowing the system to adapt on a satellite-by-satellite basis, or for example, for groups of satellites grouped by having common operational capabilities. In yet another embodiment, the slot reservation map may divide the shared medium using any degree of freedom of the system, or any combination thereof. For example, reservations may be defined with respect to geographical areas, for example, via geofence polygons, in combination with potentially frequency and / or time-based divisions. Slots may be geographically allocated using methods such as those described in International Patent Application PCT / AU2013 / 000895, filed on 14 August 2013, entitled "Channel Allocation in a Communication System." Slot allocation and communication of slot allocation information may be carried out using methods such as those described in International Patent Application PCT / AU2015 / 000743, filed on 9 December 2015, entitled "Multicarrier Communications System."

[0052] Referring again to the example shown in Figure 1B, in one embodiment, when terminal TA.1 detects the presence of satellite SB.1, it (optionally based on knowledge of its location) looks at its slot reservation map, and the scheduler 210 reduces the operational bandwidth for communicating with satellite SA.1 in order to reserve bandwidth for the operation of system B. In another embodiment, after looking at the slot reservation map 212, the scheduler 201 of terminal TA.1 schedules a transmission to allow time for system B to operate.

[0053] In another embodiment, the terminal may select slot transmit parameters to operate in coexistence with the external system while the satellite is within the field of view of both systems. In the example shown in Figure 1B, satellite SA.1 is at a high altitude relative to terminal TA.1, resulting in a shorter link distance. In contrast, TA.1 is at the edge of the field of view of satellite SB.1, resulting in a much longer link distance. Therefore, transmissions from TA.1 are expected to result in significantly higher received signal strength at SA.1 compared to SB.1, and interference from TA.1 present at SB.1 may be (or is presumed to be) acceptable. Thus, in one embodiment, the altitude of the satellite relative to the external system is such that the terminal considers itself a threat of interference to the external system. threshold It continues to operate without adapting its behavior to account for the presence of an external satellite until it intersects with a value. This value may be 5 degrees, 10 degrees, 15 degrees, or more. . thresholdThe value may be determined offline, for example, through simulation and / or analysis of acceptable inter-system interference, or it may be derived from system performance data acquired during operation. The threshold may be stored in memory and updated periodically, for example, via the system downlink or via a media tuning channel. In another embodiment, a message is scheduled to be transmitted between one or more altitude ranges. The ranges may be stored or calculated during operation. The scheduler may determine one or more altitude ranges using terminal and / or satellite (internal and / or external) antenna gain pattern and orientation information. Altitude range information may be determined offline, for example, through simulation and / or analysis of acceptable inter-system interference, or it may be derived from system performance data acquired during operation. The altitude ranges and antenna gain pattern and orientation information may be stored in memory, for example, in a slot reservation map, and updated periodically via the system downlink or via a media tuning channel.

[0054] In another embodiment, the terminal estimates the probability of successful reception at the target receiver and the level of interference that may be presented to one (or more) external receivers. The scheduler may adjust the transmit power level to achieve the desired reception probability while operating within the limits of acceptable interference to external systems. This is to mitigate performance degradation if the likelihood exceeds a threshold. The limits of acceptable interference may be stored by the terminal in a slot reservation map or provided via a medium adjustment channel. The estimate of the probability of successful reception may account for potential interference from other terminals within the field of view of the target receiver. The target receiver may provide the terminal with information on expected interference levels and other link quality characteristics using techniques such as those described in international patent application PCT / AU2018 / 000151, filed on 28 August 2018, entitled "SYSTEM AND METHOD FOR PREDICTION OF COMMUNICATIONS LINK QUALITY".

[0055] In another embodiment, determining whether a transmission is likely to cause interference involves jointly estimating the probability of an error in which the transmission is not received at the target receiver (or equivalently, a successful reception), and the level of interference from one or more external communication systems to one or more receivers during the transmission time period. In some embodiments, determining whether a transmission within a slot is likely to cause interference involves estimating a time-varying estimate of interference over the transmission time period.

[0056] In some embodiments, this estimation may be performed using an optimization method. The optimization method is generally configured to optimize one or more objective functions targeting, for example, the maximum probability of reception (or minimum error rate), the minimum (or some acceptable level) of interference to one or more external satellites (potentially from different systems), minimum power consumption, and / or maximum data rate. The variables to be optimized represent degrees of freedom presented by the slots. Examples include schedules (transmit time and / or frequency), transmit power, and spatial parameters (e.g., satellite azimuth and altitude relative to the terminal), either for a single transmit or across multiple transmits. In other embodiments, the optimization may be performed using a greedy scheduling algorithm or a similar method that is computationally simple.

[0057] Next, we will consider embodiments of the above-described method in more detail. First, we consider a packetized communication system that attempts to carry a set of messages M. The communication channel is assumed to change over time such that there is a probability p(t) that a packet sent at time t will not be received. This can also be called the probability of error or failure and is related to the probability of success = (1-p(t)). More generally, K packets are sent at times t1, ..., t K When transmitted in this manner, the probability that none of the K packets are received is p(t1, ..., t K) is assumed. This probability function p can explain various time-varying phenomena that affect the communication system. For example, in a satellite communication system, it may explain the changing visibility of a satellite orbiting in its orbit. It may also explain physical obstacles such as walls between the satellite and the transmitter. It may also explain the current system load, that is, when the communication system is under heavy load at time t, the error probability p(t) may be larger, and when the load is light, it may be smaller. Hereinafter, it is assumed that the transmitter knows the function p. A method for modeling and estimating p is described in International Patent Application PCT / AU2018 / 000151 filed on August 28, 2018, named "SYSTEM AND METHOD FOR PREDICTION OF COMMUNICATIONS LINK QUALITY". The function p is generally specific to a terminal (transmitter). That is, each transmission device estimates its own p or is provided with it. This adapts, for example, to transmitters in different locations.

[0058] Each message in M may be transmitted multiple times so as to increase the probability of being properly received at least once. t m,1 ,t m,2 ,… be a sequence of times at which the message m ∈ M is transmitted. For each message M, the transmitter may try to choose the number of repetitions K(m) and times t m,1 ,…,t m,K(m) such that the probability that m is not received satisfies the following equation. For all messages m ∈ M, p(t m,1 ,…,t m,K(m) ) ≤ ρ m (1)

[0059] The target probability of error ρ m ∈ [0, 1] is freely chosen and may be determined according to the message m. Hereinafter, (1) is called a probability constraint. Although p is presented as a probability, generally, p is a function of times t1,…,t KThe "badness" of transmission in this context may be any arbitrary criterion. Thus, constraint (1) can be used to achieve any desired quality of service metric. Another metric considered herein is latency, defined as the time between when a message is created and when it is received by the satellite. Since the terminal may not receive a direct acknowledgment from the satellite, we consider a probabilistic measure of latency.

[0060] More generally, the variable t m,1 ,t m,2 ... does not have to be strictly time, but can be any combination of degrees of freedom of the communication channel. For example, there may be cases where we want to optimize for both time and frequency, in which case t m,n is a formal pair (t m,n ,f m,n ) can be replaced with this.

[0061] In code division multiplex access systems, numerous degrees of freedom (i.e., slot transmission parameters) exist in the communication channel, such as antenna polarization, spatial / location, transmit power, or spreading sequence. For simplicity of explanation, t m,1 ,t m,2 ,…we call this time, but the resulting optimization problem and algorithm can be applied in a clear manner to more general settings. We consider this form of generalization below. The variable to be optimized is not necessarily time alone; it is common for at least one of the variables to be time. In some embodiments considered below, the objective is to satisfy the probability constraint (1) and reduce latency, while at the same time trying to reduce a more general time-varying criterion for interference generated by transmission.

[0062] First, we develop an interference model. We model time-varying interference using a function h(t) that measures the level of interference caused to an external communication system by the transmission of packets at time t. The interference h(t) is generally terminal (transmitter) specific; that is, each transmitting device estimates or is provided with its own h(t). This adapts, for example, to transmitters that are positioned differently. The interference h(t) may be determined in various ways. For example, in a satellite communication setting, it may vary in relation to the altitude φ(s,t) or range r(s,t) of satellite s in the external satellite communication system. For example, interference may be modeled as follows:

number

number

[0063] We seek the transmission time that minimizes or constrains the overall interference. Various optimization metrics can be used to achieve this. For example, we can choose to minimize the sum of the following equations:

number

number

[0064] The selected interference metric is denoted by H below. The algorithm described later can be applied to any metric used to define the overall interference.

[0065] Next, we consider a mechanism for measuring latency, that is, the time it takes for a message m∈M to be received. τ m Let t be the time when message m∈M is created. m,1 ,... are assumed to be in ascending order. The first send t m,1 If received, the latency is value t m,1 -τ m This is the smallest possible latency for message m. This smallest latency is given by probability 1-p(t). m,1 ) occurs. In general, latency is a value t with the following probability. m,n -τ m Take it. p(t m ,…,t m,n-1 )-p(t m,1 ,…,t m,n ) (6) In the formula, the probability of failure when message m is not sent at all can be interpreted as being 1, and the convention p(t m,1 ,…,t m,0 We adopt )=1. The difference of the following expression p(t m,1 ,…,t m,n-1 )-p(t m,1 ,…,t m,n ), n>0 (7) The transmission is sometimes successful, but over time... m,1 ,…,t m,n-1 It is observed that this represents the probability of failure.

[0066] The cumulative distribution of the latency for message m is as follows.

Equation

Equation

[0067] Any statistic derived from this latency distribution can be used for the purpose of choosing the transmission time. For example, it may be desired that 100a% of the messages be received within time b, and thus the following constraint may be imposed on the percentile. F(b) ≤ a (10)

[0068] Another possible metric is the expected value of the latency under the assumption that the message is received. The expected latency of message m is D(t m,1 , …, t m,K(m) , τ m ), and this is as follows.

Equation

[0069] The average of these expected values for all messages is taken to obtain the overall expected latency.

Equation

[0070] Below, L indicates the purpose of the chosen latency. For example, if you want to minimize or constrain the expected latency, set L to equal to (12). If you want to minimize or constrain the latency percentile, set L = F(b) for some target latency b, such as (10). The algorithm devised below is applicable to both these examples and others.

[0071] Before deriving specific optimization problems to minimize or constrain interference, let's introduce the actual constraints on transmission. We assume there is a minimum time W between consecutive transmissions. That is, for all m, n ∈ M, |t m,i -t n,j |≧W (13) And i,j>0, where in the equation, either m≠n or i≠j. The minimum time W is related to throughput, i.e., the rate at which transmission can occur, and therefore, hereafter referred to as (13) the throughput constraint. Smaller W corresponds to larger throughput. In practice, W is generally at least as large as the packet duration and is often made larger to accommodate, for example, heat dissipation in wireless hardware. The value of W may also be set to satisfy duty cycle constraints, for example, to meet regulatory requirements.

[0072] To simplify the notation, Pm = p(t m,1 ,…,t m,K(m) ) and probability constraint (1) P for m∈M m ≤ρ m This can be written as follows: For each message m∈M, find the number of repetitions K(m), and the time t which corresponds to the probability of a small error Pm, the small latency L, and the small interference H. m,1 ,…,t m,K(m) This is sent. This can be done in various ways. For example, one can choose to minimize interference under constraints on the probability of error and latency, that is, to find a solution of the form:

number

[0073] Alternatively, we might seek to minimize latency under constraints on the probabilities of interference and error, that is, to find a solution of the form:

number

[0074] More generally, we sometimes simply seek any solution that satisfies the constraints, i.e., any time that satisfies the following equation.

number

[0075] The algorithm described later applies to all of these examples and others.

[0076] Next, before describing the algorithm, we consider a more general scenario in which there are multiple external communication systems, for example, N systems, and we are required to minimize or constrain the interference occurring with each of them separately. n (t) indicates the interference that occurs in the nth system due to the transmission of a packet at time t. For example, in satellite communication settings, the following equation may be defined:

number

number

number

[0077] A wide range of algorithms can be used to find, or approximate, a solution to the optimization problem formulated above. Here, we consider a solution that fits under the simplifying assumption that the transmission time takes the form iW for an integer i, i.e., we constrain the transmission time to a discrete grid of width W. Under this assumption, the throughput constraint (13) is automatically solved. We also assume that all messages should be transmitted within a time interval T. In this case, we then find the transmitted packets at time from a finite set given by the following equation.

number

[0078] The interval T defines a block of time to be considered for optimization, and therefore also defines the interval at which constraints against external interference are evaluated. In practice, the interval T can be chosen to be large for the desired latency L. The interval may also be shifted forward with the current time to ensure continuous scheduling while always satisfying the interference constraints, and the preferred transmission time can be recalculated.

[0079] Since the set of time J is finite, the optimization problem is combinatorial. The solution can be found using well-known methods such as brute-force attacks or stepwise approaches that collaboratively optimize all transmission times. Optimization algorithms include simulated annealing or genetic algorithms (however, other algorithms may be used). Both approaches randomly perturb the current choice of transmission time and evaluate the cost of the current choice. Some perturbations may include: a. Increase or decrease the transmission time, i.e.

number

[0080] We observe that these approaches can be applied to more general settings where it is desirable to optimize parameters other than time. For example, suppose we want to choose a time t and a propagation sequence s for each transmitted packet. In this case, we optimize for multiple pairs of the form: (t m,n ,s m,n ) (twenty one) In the formula, t m,n is the time at which the nth iteration of message m∈M is sent, and s m,n This is the diffusion sequence used for this transmission. Let S be the set of diffusion sequences. Next, we consider the finite set J given by the following equation.

number

[0081] All the optimization problems discussed above regarding interference models can be trivially extended to this setting, and solutions can be found using the same standard algorithms, such as brute-force attacks and simulated annealing. Thus, the solutions of the present invention can be optimized over any set of degrees of freedom in a communication channel. Examples include, but are not limited to, frequency, antenna polarization, spatial / location, transmit power, or spreading sequence.

[0082] As a further example, we describe the structure of an optimization problem as a linear program that allows us to find / optimize a solution using a linear program algorithm such as the simplex method to obtain / select terminal slot transmission parameters during the transmission time period at a specific transmission location. Therefore, there are dependencies on geographical location and time, which are omitted below for clarity. Scheduling problems can also be viewed as resource allocation problems and can be performed jointly for multiple messages.

[0083] Assume there are K "slots" to consider in the optimization problem. For each of these slots k=1,2,...,K, the slot transmission parameter x k I want to select (i.e., resource allocation). The slot transmission parameter is slot selection (x k ∈{0,1}, binary variables), output (output constraint P for each slot) k For x k x = (x1, x2, ..., x) may represent any other degree of transmission freedom as described above. k Let ) represent the vector of slot transmission parameters (resource allocation), and a = (a1, a2, ..., a k ) for each slot, the utility of that slot x i ·a iLet a be a “utility vector” representing the criteria. Note that a is specific to a particular terminal and varies with geographical location and time. Vector a can also incorporate system performance factors that vary with time and location, such as system load, which affect the probability of error / success. i Factors that may influence this include satellite range and altitude, regional interference and noise, system load within the region, and local environmental features (e.g., obstacles). As mentioned above, these can be provided to the terminal via the downlink communication channel, estimated by the terminal itself (based on previous success metrics such as those obtained from its onboard orbit model, sky view model, and acknowledgment), or a mixture of downlinked and local information. For example, p k Let be the probability of failure / error for slot k. The probability is the probability of success (=1-p) as described above, provided by the terminal or to the terminal (or scheduler). k It can be measured or estimated, including by estimation of ). In either case, it is provided to the terminal in some form. Next, (binary) slot assignment x k For a terminal having , the total probability of failure assuming independent events across slots is Π k x k p k a k =-log(p k ) and then,

number

[0084] Alternatively, a i Let x be the channel gain, and ican be modeled as an output assignment, where (x,a) is the total received output and is another useful objective function for the optimization problem. The "slots" k = 1,2,…,K are time slots, and when [K]=(1,2,…,K), (x,[K]) is proportional to the average delay. Further, if 1=(1,1,…,1) is the all - one vector, it counts the number of slots used (for binary x), or measures the total output when x i represents the output assignment.

[0085] Assume there are S external systems. h j =(h j1 ,h j2 ,…,h js ) represents a "penalty vector", and h js measures the amount of disadvantage (e.g., interference) that external systems j = 1,2,…,S experience at slots j = 1,2,…,K. For each external system, define a penalty tolerance parameter β j to represent the amount of interference that the system can tolerate. β j may be measured or estimated by the terminal or system, or provided by the external system. One technique for estimating these is, in the case of the primary system, to actually decode the external system signal and measure the probability of success. These estimates may then be provided to the terminal via the communication channel. The terminal may also estimate β j through observation of the signals transmitted by the external system. A mixture of these approaches is also possible. j can also be determined according to the orbital parameters of the external system, and as part of the approach of the present invention, these orbital parameters can be provided to the terminal so that the terminal can contribute to the estimation of β j by calculating predictions for the range and altitude of the external system satellites. The reminder is β jIt is determined according to both time and geographical location and is specific to a particular terminal at a particular time (e.g., it can be determined according to a sky view map, a particular terminal antenna, and an output level, etc.). Therefore, a number of different optimization problems can be considered.

[0086] The first example is maximum utility. As an example, let a be the vector of the logarithmic probabilities described above, and under the influence of the interference limit β j , the maximum number K' of slots used, and the limit L' on the average latency (or average delay), construct an optimization problem to minimize the probability of failure.

Number

[0087] This is an integer linear program, for which there is a vast literature on methods for finding or approximating solutions to such problems. One approach can be to relax the binary constraint on x k , resulting in the following linear program.

Number

[0088] Another similar optimization approach involves minimizing the average latency (or average delay) while adding a constraint on the failure probability α.

number

[0089] Another similar optimization approach is to minimize the total penalty / interference.

number

[0090] Alternatively, penalty (x,b j ) can be optimized for one of the constraints and have other penalties as part of the constraint. Another approach is the weighted sum of the penalties Σ j c j (x,h j This optimizes ), and in the formula, c j These represent the sensitivity of each external system. j Also, simply each h j It can be absorbed into. Other variations are possible by mixing different constraints versus objectives. Similar optimization problems can be formulated, in which case x k is the output allocation (or some other terminal-specific cost parameter), where the total output (total cost) (x,1) ≤ P and the output (cost) per slot x k ≤P iEither impose constraints on the function, or optimize the output under the influence of similar constraints, i.e., min(x,1). The objective function in any of the optimization problems described above can be replaced with a nonlinear function, and well-known methods for nonlinear optimization, including the KKT method and / or the use of convex functions, can be applied.

[0091] Another example that allows inter-slot dependencies to succeed in probabilistic models is considering a quadratic objective function such as x'Ax, where A is the covariance matrix (e.g., from a joint Gaussian distribution) and x' is its transpose. For a positive definite sign A, these also allow computationally simple solutions. Another approach is to take a linear approximation of the nonlinear objective function (e.g., via a Taylor expansion). Note that in all of these optimization problems, there is no concept to prevent assignments to specific slots. Such assignments occur naturally, and x can be used if necessary. k It is under the constraint that the solution must be 0. If there are strict constraints from an external system prohibiting allocation to slots (e.g., reserved slots in a slot database), these slots can be removed beforehand from the set of slots being considered by the optimization problem.

[0092] An alternative to collaboratively optimizing all transmission times is a greedy algorithm that sequentially selects transmission times. A greedy scheduler utilizes a specific ordering of times. It is preferable to schedule transmissions at times that reduce latency and error probabilities while minimizing the increase in interference. The list of times l = (t1, ..., t K Given ), let p(l) be the probability evaluated at the time in the list. p(l) = p(t1, ..., t K ) (27)

[0093] Similarly, p(l,t) = p(t1,…,t K ,t) (28) This indicates the probability after adding time t to list l.

[0094] The greedy approximation can be applied to any of the cost functions described above. Here, we describe an algorithm that minimizes mean latency (12) and total external interference (4). We define a function that captures the optimization tradeoff given by the following equation.

number

number

[0095] The heuristic q(l,t,τ) is used by the greedy algorithm to make local decisions regarding the next message and the time to send it. The time is selected until the interference constraint is violated or the probability constraint (1) is satisfied. Then, constants a and b, or equivalently, function f L ,f p , and f H This gives some intuition about the choice of h(t). Since a large b penalizes interference, the scheduler prefers times when there is little interference, i.e., when h(t) is small. This allows for more repetitions of each message before the interference constraint is reached. The number of repetitions can implicitly be included in the interference term that chooses h(t)>0 even when no external interference occurs, in terms of the energy consumption of what is transmitted. This is seen, for example, in the satellite model of interference h from (2). s (t) is performed, and even when satellite s is not visible, h s (t)=1. A large a attempts to schedule in a way that satisfies the probability constraint, thereby reducing the number of iterations and thus reducing energy consumption. Reducing the number of iterations may also reduce the total interference H. Finally, the expected latency term L(m) prefers earlier times with a sufficiently high probability. We propose that by approximately setting the constants a and b, a wide variety of scheduling procedures can be derived. [Table 1]

[0096] Algorithm 1 begins with a list of messages M and candidate transmission times J, and returns a list of preferred transmission times for each message. Lines 2 and 3 of the procedure select the transmission time and message that minimize q. If two messages yield the same value of q(n, t(n), τn) in the minimization that occurs in line 3, then the ratio p(t m ) / ρ m The message that maximizes the probability ρ of the target is used. mThe message furthest from the (measured as a ratio) is preferred, and all others are equal. Before adding the selected time to the list, line 4 calculates the interference metric H and terminates if the interference exceeds an acceptable level. In this case, no further transmissions can be scheduled in the time interval T. Line 6 uses the updated list of transmission times to check if the probability of the current message not being received is small enough. When the target probability is reached, the message is removed from the set of messages M and is no longer considered by the algorithm. After each transmission time has been selected, it is removed from the list of candidate times J in line 8. The algorithm continues until there are no more messages to process (line 7) or until there are no more candidate times (line 9).

[0097] Referring to Figure 2B, the scheduler 210 may be configured to implement the method described above and may include a slot reservation map 212, an interference estimator 214, a latency estimator 216, and a throughput constraint 218 used to schedule the message 201. Output 240 may be a slot schedule for a message that provides message bits to the physical layer, or the scheduler may send the message bits to the physical layer for transmission according to the estimated schedule. The scheduler 210 may be configured to receive external data 230, such as updates 236, including updates to data stored in the slot reservation map 212 obtained from a medium adjustment channel 232, a link quality estimate 234, or a central or core network controller 400 (e.g., a central scheduler 440). Transmission scheduling may also be carried out using methods such as those described in international patent application PCT / AU2017 / 000058, filed on 24 February 2017, entitled “Terminal Scheduling Method in Satellite Communication System,” or those described in international patent application PCT / AU2018 / 000151, filed on 28 August 2018, entitled “System and Method for Prediction of Communications Link Quality.”

[0098] Figure 2C shows a block diagram of an access node 10 and a terminal 20 communicating through a shared communication medium 13 according to one embodiment. The access node 10 and terminal node 20 shown in Figure 2C each comprise a node-specific physical layer (PHY) 116, 126, a medium access control (MAC) layer 112, and an upper layer 111, respectively. The upper layer 111 may include a message networking layer and an application layer that provide messages to be transmitted by the lower layers and receive messages received (and processed) by the lower layers. The medium access control (MAC) layer determines how access to the radio channel is organized and controlled through the respective physical layers 113, 123, and in some embodiments implements a scheduler 210 as described herein. However, in other embodiments, the scheduler 210 (or a step of a scheduling method) may be spread across multiple layers (e.g., PHY and MAC), spread across all layers, or distributed throughout the entire system. The MAC interfaces with the physical layers 113, 123, which handle the transmission and reception of signals. The MAC provides the source bits for transmission and receives the data bits to send to higher layers (e.g., the Message Networking Layer).

[0099] The physical layers 113, 123 comprise the RF front-ends 116, 126 and additional hardware and / or software components, such as baseband receivers and baseband transmitters. Received signals are converted to baseband by the RF front-ends and delivered to the baseband receivers for processing, including demodulation and decoding to extract message data. Similarly, the baseband transmitters receive source bits and use them to generate baseband signals to be transmitted over the RF front-ends, including applying modulation and coding schemes, as well as transmit subcarriers and outputs (as commanded by the MAC). In the case of access node equipment, the baseband transmitter 114 is for downlink transmission, and the baseband receiver 115 is for uplink transmission of received signals (e.g., transmission from the terminal). In the case of terminal equipment, the baseband transmitter 125 is for uplink transmission, and the baseband receiver 124 is for downlink transmission of received signals (e.g., transmission from the access node). The physical layers may be standalone modules or boards, or they may be integrated with other components within the equipment. A software-defined wireless implementation may be used in which the RF front-end provides the received signal to an analog-to-digital (ADC) converter that provides spectral samples to a signal processor (for further processing), and receives the analog signal to be transmitted from a digital-to-analog (DAC) converter.

[0100] The terminal baseband receiver 124 processes the signal received from the access node and outputs decoded data. The receiver may also provide estimates of downlink channel effects, such as time offset, frequency offset (and its rate of change), received signal strength indicator (e.g., complex channel gain), and signal-to-noise ratio (SNR). These estimates may optionally be timestamped and may be passed to a channel state tracker, which tracks them over time and uses these parameter estimates along with any other known or estimated information about the access node (e.g., its motion relative to the terminal, or orbital parameters in the case of an access node in low Earth orbit) to predict uplink channel effects. The channel state tracker may also pass these predictions to the MAC layer, where they are used to help schedule transmissions. The predictions may also be passed to the baseband transmitter, where they are used to pre-compensate for uplink channel effects. In some embodiments, the terminal determines which slot to transmit in, and in other embodiments, the terminal may send a channel access request to the access node. The access node decodes the data received from the terminal, then allocates an uplink slot to the terminal for future use, and notifies the terminal of the allocation via a downlink message. Similar processing may be performed at the access node, and the baseband receiver 115 may process the signal received from the terminal and output the decoded data along with estimates of uplink channel effects, such as time offset, frequency offset (and its rate of change), complex channel gain, and signal-to-noise ratio (SNR). In some examples, the access node may capture spectral samples and forward them to a central processor in the core network 400 via a gateway node that estimates these quantities.

[0101] Figure 3 is a schematic diagram of a slot schedule 240 according to one embodiment. In this embodiment, slots are divided by time (x axis) and frequency (y axis). In this embodiment, the time dimension of the uplink is divided into time slots 310, and the frequency dimension of the uplink is divided into subcarrier slots 320. In this embodiment, a frame 330 consists of integer time slot periods.

[0102] In this embodiment, a permanently reserved slot 340 is shown in a shaded area. In this embodiment, this includes a set 342 of all subcarriers at a particular time and a block 344 spanning multiple times and subcarriers. In addition, several individual transient slots 352 and transient blocks 354 of slots are shown, representing slots to be avoided in order to minimize interference with other systems. Thus, the remaining slots can be freely allocated by the system, and the slot map further indicates, for example, which slot each message is sent in to maximize system performance while minimizing interference (not shown).

[0103] Figure 4 is a schematic diagram of a satellite communication system 1 according to one embodiment. The communication system 1 shown in Figure 4 may also be called a communication network and comprises a plurality of satellite access nodes 10 and a plurality of terminals 20. The core network 400 comprises access nodes 410 (satellite and ground), an access gateway 430, a network scheduler device 440, and an authentication broker 450. The broker 450 can directly exchange data 462 with an application 460 (via an application gateway) and control information 464 with an application 460. The components of the core network 400 may be distributed and communicate across communication links. Some components may be cloud-based. A terminal 20 or satellite 10 may provide information to the network scheduler device 440 in the core network 400 in order to perform optimization calculations for scheduling transmissions and provide scheduling information to the terminals and satellites. The network scheduler 440 may also collect and process information about other satellite communication systems and provide the relevant data to the terminal 20 or the local scheduling module of the satellite 10, for example, to update the slot reservation map 212 or to provide parameters for local interference calculations. The terminal 20 may monitor reference links such as the media adjustment channel 24 using additional transmitters 10 of other communication systems, including satellite transmitters such as GNSS satellites and ground transmitters.

[0104] In one embodiment, System 1 uses a publisher-subscriber model and comprises the following system entities (also called nodes or devices): Terminal 20: The communication module within the terminal provides core network connectivity to the access node. Terminal 20 may have both mounted devices 402 and sensors 404. These may be physically mounted or integrated, or operationally connected to the terminal via a local wired or local wireless link. Device 402: These entities receive data that is subscribed to via the authentication broker. Sensor 404: These entities emit data without recognizing other network nodes. Sensors may also receive ephemeral control data, emit ACK messages, etc. Access Node 410: Multiple access nodes provide wireless communication with multiple terminals. Most access nodes are satellite access nodes, but the system may also include ground base stations and high-altitude platforms. The access nodes provide access to the core network 400. Access Gateways 430: These act as gateways between access nodes and authentication brokers. The gateways may be combined with access nodes 410 (for example, on a satellite). Authentication Broker 450: A broker between the publisher and the subscriber. The broker authenticates that incoming messages originate from registered terminals. The authentication broker may include an application gateway that acts as a data gateway to application 460 and may implement a number of interfaces. These may be cloud-based interfaces. The interfaces include a Message Queue Telemetry Transport (MQTT) interface that forwards to customer-controlled endpoints or customer-accessible endpoints. Application 460: Customer applications. These communicate with application gateways, such as cloud-based application gateways, via wired and wireless links.

[0105] Embodiments of the method have been described in relation to terminal and access node communications. However, the method may also be used to schedule communications between an access node and a gateway (e.g., a ground station) while minimizing interference with other communication systems. Similarly, if a terminal and / or gateway is in motion and the terminal comes within range of the gateway, the terminal and gateway may also use the method described herein to schedule transmissions while minimizing interference with other communication systems.

[0106] Methods have been described for enabling network entities such as terminals and access nodes to perform interference-aware scheduling. The methods described herein may be used in communication systems in which at least some of the access points have satellites (including LEO and medium-earth orbit (MEO) satellites), or high-altitude platforms such as airborne access points (pseudosatellites), or high-altitude unmanned aerial vehicles (UAVs) such as solar and / or battery-powered drones or airships that can remain in the air for extended periods (e.g., several days), or fixed or mobile ground access points. The system may also be used in conjunction with entirely terrestrial communication systems located on land or at sea (i.e., purely ground access points and / or terminals), or communication systems corresponding to ground access points and / or terminals and airborne access points and / or terminals that share a spectrum and have potential interference with satellite (or airborne / high-altitude) communication systems.

[0107] The scheduler 440 may also be configured to perform transmission scheduling, such as that described in international patent application PCT / AU2017 / 000058, titled "Terminal Scheduling Method in Satellite Communication System," filed on 24 February 2017, or using a probabilistic scheduling method based on link quality estimation, such as that described in PCT / AU2018 / 000151, filed on 28 August 2018, titled "System and Method for Prediction of Communications Link Quality."

[0108] In another embodiment, media utilization is further improved by enabling multiple users to coexist on the same spectrum using the technology described in international patent application PCT / AU2014 / 000826, filed on 21 August 2014, entitled "A MULTIUSER COMMUNICATIONS SYSTEM." By carefully managing inter-system interference, it is possible to enable multiple systems to coexist, which offers further benefits to resource utilization and system performance. Multiuser receiver technology can also leverage transmit power as a degree of freedom for media sharing. For example, strong and weak signals may coexist, with the strong signal appropriately canceling out before the weaker signal is decoded.

[0109] We have described various embodiments of adaptive communication systems that perform interference-aware scheduling to efficiently enable spectrum sharing by multiple separate communication systems using a shared communication medium. The scheduler may be implemented in terminals, access nodes (including satellite access nodes), gateways, or distributed throughout the communication system. The scheduler 210 is configured to schedule transmissions by selecting slot transmission parameters with arbitrary transmission degrees of freedom (e.g., time, frequency, antenna polarization, spread sequence, transmit power, etc.). In some embodiments, one or more receivers in one or more external communication systems may be determined to be present during the transmission time period, for example, by direct detection, estimation based on ephemeris or other data, or by transmission or beacon acquisition. The scheduler is configured to schedule the transmission of one or more messages in one or more slots of multiple slots by selecting one or more slot transmission parameters for transmitting one or more messages during the transmission time period. Scheduling involves using one or more interference parameters to determine the likelihood that one or more selected slot transmit parameters are likely to cause interference to one or more external communication systems, and, if interference is determined to be likely, adjusting one or more of the slot transmit parameters to determine whether the changes result in an acceptable reduction of interference. In some embodiments, a slot reservation map may be used to determine whether a transmit in a slot is likely to cause interference to one or more external communication systems. In some embodiments, a probabilistic approach may be used in which the probability of successful reception or the probability of error (i.e., not being received) is estimated. In some embodiments, the scheduler is configured to minimize a time-varying criterion for interference to external communication systems while simultaneously minimizing a time-varying criterion for communication quality (e.g., the probability of errors and latency). These methods leverage the time-varying nature of interference.The probability of error P for each message m∈M, while minimizing latency, that is, minimizing the time required to receive each message. m We have described how to choose the transmission time for a list of M messages that attempts to constrain interference H. Alternatively, the scheduler can choose the probability of error P for each m∈M message while minimizing interference. m And we choose the transmission time for a list of M messages that we want to constrain the latency L, or the probability of error P for each m∈M message. m You may choose a transmission time for a list of M messages that seeks to constrain latency L and interference H. Latency L may be measured as the expected latency (12), or latency may be the percentile P as in (10). m (b) may be measured as

[0110] Those skilled in the art will understand that information and signals may be represented using any of the various techniques and methods. For example, data, instructions, commands, information, signals, bits, codes, and chips, which may be referenced throughout the above description, may be represented by voltage, electric current, electromagnetic waves, magnetic fields or magnetic particles, light fields or optical particles, or any combination thereof.

[0111] Those skilled in the art will further recognize that various exemplary logic blocks, modules, circuits, and algorithmic steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, instructions, or a combination of both. To clearly illustrate this hardware-software compatibility, various exemplary components, blocks, modules, circuits, and steps have been described above in terms of their functionality as a whole. Whether such functionality is implemented as hardware or software depends on the specific application and design constraints imposed on the overall system. Those skilled in the art will recognize that the described functionality can be implemented in various ways for each specific application, but such implementation decisions should not be construed as causing a departure from the scope of the invention.

[0112] Steps of methods or algorithms described in connection with embodiments disclosed herein may be embodied directly in hardware, in software modules executed by a processor, or in a combination of the two. In the case of hardware implementations, the processing may be implemented within one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, or other electronic units designed to perform the functions described herein, or in combination thereof.

[0113] In some embodiments, the processor module comprises one or more central processing units (CPUs) configured to perform some of the steps of the method. Similarly, a computing device may be used to generate a trajectory model to be supplied to a terminal device, and the computing device may comprise one or more CPUs. The CPU may comprise an input / output interface, an arithmetic logic unit (ALU), and control and program counter elements that communicate with input and output devices through the input / output interface. The input / output interface may comprise a network interface and / or a communication module for communicating with an equivalent communication module in another device using a given communication protocol (e.g., Bluetooth, Zigbee, IEEE 802.15, IEEE 802.11, TCP / IP, UDP, etc.). The computing or terminal device may comprise a single CPU (core), multiple CPUs (multi-core), or multiple processors. The computing or terminal device may use parallel processors, vector processors, or distributed computing devices. Memory may be operably coupled to the processor and comprise RAM and ROM components, and may be provided within or outside the device or processor module. Memory may be used to store the operating system and additional software modules or instructions. The processor may be configured to load and execute the software modules or instructions stored in memory.

[0114] A software module, also known as a computer program, computer code, or instruction, may comprise numerous source code or object code segments or instructions and may reside on any computer-readable medium, such as RAM memory, flash memory, ROM memory, EPROM memory, registers, hard disks, removable disks, CD-ROMs, DVD-ROMs, Blu-ray® discs, or any other form of computer-readable medium. In some embodiments, the computer-readable medium may include non-temporary computer-readable medium (e.g., tangible media). In addition, in other embodiments, the computer-readable medium may include temporary computer-readable medium (e.g., signals). Combinations of the above also fall within the scope of computer-readable medium. In another embodiment, the computer-readable medium may be integrated with a processor. The processor and computer-readable medium may reside on an ASIC or associated device. The software code may be stored in memory units, and the processor may be configured to execute them. The memory unit may be implemented inside or outside the processor, in which case it can be coupled to the processor in a communicative manner via various means known in the art.

[0115] Furthermore, it should be recognized that modules and / or other suitable means for carrying out the methods and techniques described herein can be downloaded and / or otherwise obtained by a computing device. For example, such a device can be coupled to a server to facilitate the transfer of means for carrying out the methods described herein. Alternatively, the various methods described herein can be provided via storage means (e.g., physical storage media such as RAM, ROM, flash drives, optical discs (DVDs, CDs), etc.) so that the computing device can acquire the various methods when coupling or providing the storage means to the device. Furthermore, any other suitable techniques for providing the methods and techniques described herein to a device can be utilized.

[0116] The methods disclosed herein include one or more steps or actions to achieve the described methods. The steps and / or actions of the methods may be interchangeable with one another without departing from the claims. In other words, unless a specific order of steps or actions is specified, the order and / or use of any particular steps and / or actions may be modified without departing from the claims.

[0117] As used herein, the terms “estimate” or “determine” encompass a wide range of actions. For example, “estimate” or “determine” may include calculating, computing, processing, deriving, investigating, searching (e.g., searching a table, database, or other data structure), confirming, etc. Also, “estimate” or “determine” may include receiving (e.g., receiving information), accessing (e.g., accessing data in memory), etc. Also, “determine” may include resolving, selecting, choosing, establishing, etc.

[0118] Throughout the specification and the claims below, unless otherwise required by context, the words “equip” and “include,” as well as variations such as “equip” and “include,” are understood to mean that they include the integer or set of integers presented, but do not exclude any other integer or set of integers.

[0119] Any reference to prior art in this specification does not constitute, and should not be construed as, an endorsement of any suggestion that such prior art forms part of common sense.

[0120] Those skilled in the art will recognize that the use of this disclosure is not limited to one or more specific uses described herein. Furthermore, this disclosure is not limited to preferred embodiments of this disclosure with respect to certain elements and / or features described or illustrated herein. It will be recognized that this disclosure is not limited to one or more embodiments disclosed and that numerous reconfigurations, modifications, and substitutions are possible without departing from the scope described and defined by the following claims.

Claims

1. A method for scheduling transmissions in a wireless communication system comprising one or more access nodes and multiple terminals, The one or more access nodes include at least one access node having a field of view that moves toward the plurality of terminals, and the method is Receiving one or more messages in order to send, Regarding the transmission location, the following is determined: one or more interference parameters of one or more external communication systems during the transmission period. A method comprising: selecting one or more slot transmission parameters for transmitting one or more messages during the transmission time period; determining the likelihood that the selected one or more slot transmission parameters are likely to cause interference to one or more external communication systems using one or more interference parameters; and, if it is determined that interference is likely, scheduling the transmission of one or more messages in multiple slots by adjusting one or more of the slot transmission parameters with respect to latency, throughput, and error rate while ensuring an acceptable level of interference.

2. The method according to claim 1, wherein determining the one or more interference parameters includes storing a slot reservation map that stores one or more reserved slots for the one or more external communication systems, and determining the likelihood that the selected one or more slot transmission parameters are likely to cause interference using the one or more interference parameters includes examining any reserved slot associated with any of the detected or estimated one or more external communication systems and preventing the selection of such reserved slot.

3. The method according to claim 1 or 2, wherein determining the one or more interference parameters includes storing one or more reserved slots for the one or more external communication systems and storing a slot reservation map in which one or more of the one or more reserved slots are reserved for each satellite, and determining the likelihood that the selected one or more slot transmission parameters are likely to cause interference using the one or more interference parameters includes detecting or estimating that a satellite associated with a reserved slot is present during the transmission time period, and, if such satellite is detected or estimating, preventing the selection of the reserved slot.

4. The method according to any one of claims 1 to 3, wherein determining the one or more interference parameters includes storing one or more reserved slots for the one or more external communication systems and storing a slot reservation map in which one or more of the one or more reserved slots are reserved for each geographical area, and determining the likelihood that the selected one or more slot transmission parameters are likely to cause interference using the one or more interference parameters includes estimating the location of a transmitter during the transmission time period, determining whether the transmitter is located within the geographical area associated with the one or more reserved slots, and preventing the allocation of each of the reserved one or more slots.

5. The method according to any one of claims 1 to 4, wherein determining one or more interference parameters includes determining a threshold for one or more receivers in the one or more external communication systems, and determining the likelihood that the selected one or more slot transmission parameters are likely to cause interference includes estimating the elevation angle of a receiver in the one or more external communication systems during the transmission time period and determining whether the elevation angle exceeds the threshold for the receiver.

6. The method according to any one of claims 1 to 5, wherein determining one or more interference parameters of one or more external communication systems includes detecting beacon signals from transmitters in the one or more external communication systems and determining one or more beacon signal characteristics used to determine whether they are likely to cause interference.

7. The method according to any one of claims 1 to 6, wherein determining one or more interference parameters of one or more external communication systems includes receiving information contained in one or more transmissions from transmitters in the one or more external communication systems on a media adjustment channel, and providing the scheduler with information to assist in sharing a medium, including one or more of the following: elevation angle, signal-to-noise ratio, interference level, output level, link quality estimate, channel state estimate, or acceptable interference level.

8. The method according to claim 7, wherein the information is used to update the slot reservation map, as dependent on claims 2 to 4.

9. During the transmission time period with respect to the transmission location, one or more interference parameters of one or more external communication systems are determined. To acquire ephemeris data for one or more satellite receivers in the one or more external communication systems, This includes obtaining an estimated value of the position of the transmitter during the transmission time period, The method according to any one of claims 1 to 8, wherein the likelihood of the selected one or more slot transmission parameters causing interference is determined using the one or more interference parameters, and the likelihood of interference with the one or more receivers in the one or more external communication systems is estimated using terminal location, ephemeris data, and transmission time period.

10. The method according to any one of claims 1 to 9, wherein determining the likelihood that the selected one or more slot transmit parameters are likely to cause interference using the one or more interference parameters comprises estimating a time-varying estimate of the interference over the transmission time period and selecting one or more slot transmit parameters, and adjusting one or more of the slot transmit parameters is done by determining the one or more slot transmit parameters that minimize or constrain the total interference using an optimization method.

11. The method according to claim 10, wherein determining the likelihood that the selected slot transmit parameters are likely to cause interference using the one or more interference parameters further includes estimating the probability of an error in which a transmission is not received by a target receiver and latency, the optimization method determines the one or more slot transmit parameters by minimizing one of the time-varying estimate of interference over the transmission time period, the probability of an error in which a transmission is not received by a target receiver and latency under the influence of one or more constraints on the time-varying estimate of interference over the transmission time period, the probability of an error in which a transmission is not received by a target receiver and latency, and the optimization is performed jointly for all slot transmit parameters.

12. The method according to claim 11, wherein the optimization is performed under the influence of throughput constraints.

13. The method according to claim 12, wherein the throughput constraint includes restricting the transmission time to a discrete grid of width W during the transmission time period.

14. The method according to any one of claims 11 to 13, wherein the latency is the total expected latency obtained by calculating the latency distribution for each message, using the latency distribution to determine the expected latency for each message, and taking the average of the expected latencies for the set of messages.

15. The method according to any one of claims 11 to 13, wherein the latency constraint is based on percentile probabilities.

16. The method according to claim 10, wherein determining the likelihood that the selected one or more slot transmit parameters are likely to cause interference using the one or more interference parameters further includes estimating the probability of an error in which a transmit is not received by a target receiver and latency, and the optimization method uses a greedy scheduling algorithm that successively selects transmit times such that the transmit is scheduled at a time that reduces the probability of latency and error while minimizing the increase in interference.

17. The method according to claim 16, wherein the greedy scheduling algorithm minimizes average latency and total external interference.

18. The method according to any one of claims 1 to 17, wherein the one or more slot parameters include an arbitrary degree of transmission freedom.

19. The method according to claim 18, wherein the transmission degrees of freedom include one or more of time, frequency, antenna polarization, spread sequence, transmission power, or spatial partitioning.

20. The method according to any one of claims 1 to 19, further comprising obtaining an estimate of the position of the transmitter during the transmission time period, determining the likelihood that the selected one or more slot transmission parameters are likely to cause interference using the one or more interference parameters, and determining whether the transmission in a slot is likely to cause interference using the estimate of the position of the transmitter.

21. The method according to any one of claims 1 to 20, wherein the method is carried out on a terminal device.

22. The method according to any one of claims 1 to 20, wherein the method is carried out at a satellite access node.

23. The method according to any one of claims 1 to 20, wherein the communication system further comprises one or more gateways, and the method is carried out at at least one gateway.

24. The method according to any one of claims 1 to 23, wherein at least one of the access nodes is a satellite access node or a high-altitude platform.

25. A terminal device comprising an uplink baseband transmitter and an RF front end, and a scheduler configured to carry out the method according to any one of claims 1 to 20.

26. An access node device comprising a downlink baseband transmitter and an RF front end, and a scheduler configured to carry out the method according to any one of claims 1 to 20.

27. A gateway device comprising an uplink baseband transmitter and an RF front end, and a scheduler configured to carry out the method according to any one of claims 1 to 20.

28. A communication system comprising a core network component having one or more terminal devices, one or more satellite access nodes, and one or more gateways, configured to carry out the method according to any one of claims 1 to 20, wherein the implementation is distributed across the system.

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