Method and system for providing a data connection via satellite

Abstract

The invention relates to a method (100) for providing a data connection via satellites (21, 23) on board vehicles, in particular aircraft (1), and a correspondingly designed system (10). In the method (100) for providing a data connection via satellite (21, 23) on board vehicles, in particular aircraft (1), with an antenna (11) and at least one modem (12, 13) connected thereto for alternative connection with a separate satellite (21) or satellite network (22), characteristic parameters for the quality of the respective data connection are determined, on the basis of which a preferred data connection is determined, which is then established. The system (10) for providing a data connection via satellites (21, 23) on board vehicles, in particular aircraft (1), comprises an antenna (11) and at least one modem (12, 13) connected thereto for alternative connection with each separate satellite (21) or satellite network (22) and a control unit (14) connected to the at least one modem (12, 13) for data transmission, which is configured to carry out a method (100) according to the invention.

Description

[0001] The invention relates to a method for providing a data connection via satellite on board vehicles, in particular aircraft, and to a correspondingly designed system.

[0002] Especially for vehicles that are regularly outside the reception range of terrestrial wireless data transmission networks (e.g., mobile networks), such as ships or aircraft, it is common practice to provide a data connection via satellite. If this data connection is not only used by the crew for operational purposes, such as retrieving navigation and / or weather data and / or transmitting data on the vehicle's operational status to a higher authority, but is also intended to be made available to passengers on board for use with the internet, a reliable data connection with a consistently high bandwidth is desirable.

[0003] Various systems are known from the prior art in which a modem designed to connect to a specific, predetermined satellite or satellite network is installed on board the vehicle. The modem connects to the fixed satellite (network) via a typically steerable antenna to establish a data connection. The modem usually has either a positioning module to determine its geographic position or a suitable input through which the vehicle provides it with the corresponding position information. The modem can then align the antenna, or—in the case of electronically steerable antennas (ESAs)—the direction of the antenna's transmission, appropriately with the predetermined satellite or a satellite within the predetermined satellite network.

[0004] A disadvantage of this state of the art is the modem's reliance on a specific satellite or satellite network: Due to frequent software-based binding of modems to a particular satellite or satellite network, or to the respective operator, well-known modems typically only allow a data connection via a specific satellite or satellite network. If a data connection via the specified satellite or satellite network cannot be established—for example, because the vehicle is outside the satellite's (network's) geographical coverage, technical problems with the satellite (network) prevent a connection, or the satellite (network) is congested—the passengers in the vehicle will not have internet access until all obstacles to a functioning data connection have been removed.

[0005] The object of the present invention is to create a method and a system in which the disadvantages of the prior art no longer occur or only occur to a reduced extent.

[0006] This problem is solved by a method according to claim 1 and a system according to claim 12. Advantageous further developments are the subject of the dependent claims.

[0007] Accordingly, the invention relates to a method for providing a data connection via satellite on board vehicles, in particular aircraft, with an antenna and at least one, preferably at least two modems connected thereto for alternative connection with a separate satellite or satellite network, comprising the steps: a) If a data connection to a separate satellite or a satellite of a satellite network exists via a modem, disconnect this existing data connection; b) Establishing a data connection with a separate satellite or a satellite of a satellite network; c) Determination of at least one parameter characteristic of the quality of the data connection; d) Evaluation of the characteristic parameters determined for data connections according to predefined criteria to identify a preferred data connection; e) If the preferred data connection is not the existing data connection, disconnect the existing data connection and establish a data connection with a separate satellite or a satellite of a satellite network.

[0008] Furthermore, the invention relates to a system for providing a data connection via satellite on board vehicles, in particular aircraft, with an antenna and at least two modems connected thereto for alternative connection with each a separate satellite or satellite network and a control unit connected to the modems, wherein the control unit is configured to carry out the method according to the invention.

[0009] First, individual terms used in connection with the invention will be explained.

[0010] Within the scope of the present invention, a "satellite" is defined as a spacecraft orbiting the Earth in a predetermined path. This satellite is designed for radio communication with modems on board vehicles and with one or more ground stations, enabling the provision of a data connection. If a single satellite is used for this purpose, it is typically a satellite in a geostationary orbit (orbital inclination 0°, radius 42,164 km, direction of rotation eastward) that consistently covers the same area of ​​the Earth and can, for example, provide internet access. The coverage area of ​​such a satellite is limited to approximately ±70° in the north-south and east-west directions, measured from the satellite's base on the equator; outside this area, no contact with the satellite and therefore no data connection is possible.

[0011] A "satellite network" comprises multiple satellites to which a suitable modem can selectively connect to establish a data connection. For a data connection to work, it is sufficient if a modem can establish a radio link to one of the satellites in the network and if a handover of the connection from one satellite to another within the network is possible. The satellites in such a network do not have to be geostationary; they can be located in lower orbits, particularly low or medium Earth orbits. Networks equipped with a sufficient number of satellites can also provide internet access to areas of the Earth's surface not covered by geostationary satellites.

[0012] The term "received signal strength" refers to the signal strength that a modem can detect from the satellite with which it currently has a radio connection. Received signal strength indicates whether the existing connection is suitable for actual communication. If the modem is connected to a satellite network, a low received signal strength can trigger a switch in the connection from one satellite to another within the network.

[0013] "Latency" refers to the travel time of a signal from the modem to a specific instance, such as a central server on the ground. The round-trip time (RTT) of a data packet traveling from the modem to a specific instance and back can also be used as a measure of latency.

[0014] "Data throughput" indicates the net amount of data per unit of time that can be transmitted via a modem and the data connection established with it.

[0015] Various methods are known from the state of the art for determining, at least approximately, received signal strength, latency, and data throughput. While received signal strength can usually be determined directly by the modem itself, latency and data throughput can also be determined by components connected to the modem, such as a control unit.

[0016] The invention recognizes that by selectively connecting to different satellites (networks) on board vehicles, a more reliable data connection can be achieved, thus enabling, for example, passengers to have a stable and, ideally, high-bandwidth data connection for the entire duration of their journey. Depending on the satellites or satellite networks accessible by the modem(s) provided on board the vehicle, the geographical area in which a data connection is fundamentally possible can also be extended.

[0017] The invention takes into account that even in the case of two or more modems, the number of antennas cannot or should not be adjusted accordingly, but rather several modems must share a single antenna. For example, on aircraft, the installation of antennas is generally only possible outside the shielding fuselage structure, within radomes located on the outside of the fuselage. These radomes must be structurally designed and connected in a way that is suitable to withstand weather conditions and the aerodynamic stresses during flight. Therefore, every effort is made to keep the number and size of radomes as small as possible. Consequently, the number of possible antennas is also limited. This applies particularly to existing aircraft, where the addition of further radomes and / or antennas is, if at all possible, only feasible with considerable effort.

[0018] The invention recognizes that an antenna technically suitable for data communication with a first separate satellite or a satellite of a first satellite network is also fundamentally suitable for establishing a data connection to a second separate satellite or a satellite of a second satellite network; the different signal processing regularly required for connections with different satellites or satellites of different satellite networks can be ensured by a modem designed for this purpose or by modems tailored to individual satellites or satellite networks, without requiring any adaptation of the antenna.

[0019] Against this background, the invention provides that even when a data connection exists via a modem and its associated antenna to a separate satellite and a satellite of a satellite network, this connection is interrupted in order to use the antenna, together with the same or a different modem, to connect to another separate satellite or a satellite of a different satellite network, in order to determine at least one characteristic parameter for the connection then established to the other satellite, which provides information about, for example, its stability and / or bandwidth. This at least one characteristic parameter can then be checked according to predefined criteria and used to identify the connection to a separate satellite or a satellite network that promises the "better" or preferred data connection.

[0020] If the preferred data connection corresponds to the existing data connection at that time, the latter can remain active. If it turns out that a different, previously existing data connection is preferred, the currently existing data connection is disconnected and a data connection is established via the modem belonging to the preferred data connection. This may also be the modem through which a data connection existed at the beginning of the process.

[0021] Even though an existing data connection is generally interrupted during the execution of the inventive method in order to determine characteristic properties of other data connections, the disadvantage of the usually very short-term interruption of an existing data connection until a preferred data connection is identified and finally established is more than compensated for by the fact that, at the end of the method, a data connection identified as the preferred one exists based on predefined criteria. Depending on the predefined criteria, the data connection ultimately considered preferred may, for example, exhibit higher stability, higher received signal strength, lower latency, and / or higher data throughput.

[0022] It is preferred if at least two modems are connected to the antenna, with each data connection to a separate satellite or a satellite of a satellite network only being possible via one of the at least two modems. In other words, one of the generally available data connections should only be possible via one of the modems, and another generally available data connection only via a different modem. Even when using multiple modems, only one shared antenna should be provided for them.

[0023] To directly consider any existing data connection at the start of the process when identifying the preferred data connection, it is preferable to determine at least one characteristic parameter for the quality of any existing data connection before step a) of the process. The determination of this characteristic parameter(s) is generally performed while maintaining the data connection, so that no interruption of the connection occurs during this determination. If at least one characteristic parameter for the quality of the data connection exists at the start of the process, this parameter can be compared with the characteristic parameter(s) subsequently determined for one or more alternative data connections, based on the specified criteria, in order to identify the preferred data connection.In particular, such a procedure also makes it easy to identify the initially existing data connection as the preferred data connection, which can then be restored accordingly.

[0024] Particularly when more than two data connections are possible, but also in the case of two available data connections, unless at least one parameter characteristic of the data connection quality is determined for the data connection existing at the beginning of the process before step (a), as described above, it is preferably provided that steps (a) to (c) of the method according to the invention are repeated so frequently that at least one parameter characteristic of the data connection quality has been determined for each of the data connections that are fundamentally available. This ensures that all data connections can be considered and compared with each other based on the relevant characteristic parameters when determining the preferred data connection.

[0025] It is preferred that, before establishing a data connection via another modem, the vehicle's geographic position is determined – for example, using a satellite navigation system such as GPS, GALILEO, and / or GLONASS – and that, based on the determined position, the basic availability of the dedicated satellite or satellite of a satellite network assigned to the data connection is ascertained. Establishing a data connection for the subsequent determination of at least one parameter characteristic of the data connection quality only occurs if the availability of at least one satellite has been determined. This ensures that an attempt is made to establish a connection with a satellite or satellite network only if a data connection appears fundamentally possible.In particular, no connection attempt is made if the vehicle is located outside the coverage area of ​​the satellite or satellite network due to its geographical position. This avoids interrupting an existing data connection to determine quality parameters of a connection that is already known to be unavailable. If a specific data connection is unavailable, the characteristic parameters for its connection quality can be set to the lowest possible value. Alternatively, the affected modem can be marked as "not connected" and ignored when determining the preferred data connection.

[0026] The characteristic parameter for the quality of a data connection can be the received signal strength, the latency, or the data throughput. If more than one characteristic parameter is to be determined, any selection of the aforementioned or additional parameters can be measured. The method according to the invention does not require any specially designed modems, but rather relies solely on functionalities generally available in modems for satellite communication, such as the determination of the received signal strength. The latency and data throughput can be determined independently of the modem through which the data connection exists, for example, by a control unit connected to it. For this purpose, the control unit only needs to be able to send and / or receive suitable data packets via the respective modems.As a result, the method according to the invention can be carried out with any satellite modems, which do not need to be specially adapted for this purpose.

[0027] To enable better comparability of the at least one characteristic parameter determined for different data connections for identifying the preferred data connection, it is preferred if the at least one characteristic parameter, in particular the received signal strength, the latency, and / or the data throughput, is normalized using reference values ​​specified for the respective modem. The respective reference values ​​for the individual modems can be location-dependent—i.e., dependent on the geographical position of the vehicle—and / or time-dependent.

[0028] To minimize the interruption of an existing data connection during the inventive method, it can be provided that, in the case of determining more than one parameter characteristic of the data connection quality, the determination of a second parameter only takes place if a first parameter, previously determined and, if necessary, normalized, lies above or below a predetermined threshold. For example, the latency can only be determined if the received signal strength is above a predetermined threshold and / or the data throughput only if the latency is below a predetermined threshold, since if the respective thresholds are exceeded or fallen below, it can be assumed that the parameters to be determined subsequently will not reach a value that would make the tested data connection the preferred data connection. The time required for step (c) of the method can thus be reduced.

[0029] It is preferred that the described procedure for establishing the data connection via satellite on board vehicles be repeated regularly to ensure that the best available connection is always used. For this purpose, the procedure can be repeated at regular, predetermined intervals. Alternatively or additionally, it is possible to perform the procedure after a change in the vehicle's geographic position. For this, position information that is recorded on board the vehicle for other reasons, e.g., for navigation purposes, can preferably be used. If a change in position of a predetermined magnitude is detected, the connections via the individual modems can be re-evaluated.

[0030] It is preferred if the provided data connection allows access to the internet.

[0031] It is further preferred if the antenna is steerable and / or multi-frequency capable. Steerability, which can be achieved in particular through electronic beam steering (ESA), enables rapid switching of data connections to different satellites or satellite networks. If the antenna is multi-frequency capable, the method can also be used with satellites and satellite networks that communicate on different frequencies.

[0032] The vehicle for which the method according to the invention is carried out is preferably an aircraft, in particular a passenger aircraft.

[0033] To explain the system according to the invention, reference is first made to the preceding statements.

[0034] At least one of the modems and / or the control unit can include a position determination module. It is advantageous if those components without a position determination module can, if necessary, receive position information from the component with a position determination module and are appropriately data-connected for this purpose. Alternatively, it is possible for at least some of the modems and / or the control unit to receive position information from a separate position determination module, which is not part of the system, via suitable inputs. For example, the system can thus use position information from the vehicle's navigation system.

[0035] The invention will now be described by way of example using an advantageous embodiment with reference to the accompanying drawings. These show: Fig. 1: a schematic representation of a system according to the invention on board an aircraft; and Fig. 2: a schematic representation of a method according to the invention, as implemented by the system according to Fig. 1 is carried out.

[0036] In Fig. Figure 1 schematically illustrates a system 10 according to the invention in a state installed on board an aircraft 1. Fig. Section 1 further outlines the integration of system 10 with regard to its basic functionality.

[0037] System 10 comprises an adjustable antenna 11 to which two modems 12 and 13 are connected. One modem 12, when the antenna 11 is appropriately oriented, is configured for radio communication with a geostationary satellite 21, while the other modem 13—also when the antenna 11 is appropriately oriented—is configured for radio communication with a satellite 23 of a satellite network 22, whose satellites 23 are located in low Earth orbit. A data connection can be established via satellite 21 or the satellite network 22 and associated ground stations 31 and 32, enabling access to the internet 40 and, through that, access to a predefined server 41.

[0038] The modems 12, 13 are designed according to the prior art. In particular, the modems 12, 13 can be modems 12, 13 provided by the respective operator of the satellite 21 or the satellite network 22, which regularly have sufficient functionality for the system 10 according to the invention – in addition to the actual data transmission, for example, also the determination of the received field strength – so that no adaptation of the modems 12, 13 is required.

[0039] Modems 12 and 13 are data-connected to a control unit 14. In addition to exchanging the data to be transmitted, the control unit 14 also receives information about the respective received signal strength from modems 12 and 13 via this connection. The control unit 14 is also connected to antenna 11 to align it or to direct it to a modem 12 or 13, which then uses appropriate control signals to align antenna 11.

[0040] In the illustrated embodiment, modems 12 and 13 each include a positioning module for determining the geographic position via satellite navigation systems such as GPS, GALILEO, and / or GLONASS, among other things to enable appropriate orientation of the antenna 11. This geographic position information is also transmitted to the control unit 14. Alternatively, the control unit 14, and possibly also the modems 12 and 13, can be supplied with geographic position data via the aircraft's control system 1, which typically also has a satellite navigation system. In this case, the positioning module of modems 12 and 13 can be omitted.

[0041] Also connected to the control unit 14 is a local wireless access point 15 (“Wireless Access Point”), e.g., a wireless access point according to the IEEE 802.11 standard. Passengers' mobile devices can connect to this wireless access point 15 in order to then access an existing data connection to the Internet 40 via the access point 15 and the control unit 14.

[0042] The control unit 14 is configured to implement a method 100 according to the invention, as described below with reference to the Fig. 2 is explained, to be carried out.

[0043] The following assumes that at the beginning of the Fig.In the method shown, a data connection exists via modem 12 and satellite 21, through which end devices connected to access point 15 can communicate with server 41 via the internet, for example. However, it is of course also possible that a data connection exists via the other modem 13.

[0044] In step 110, parameters characteristic of the existing data connection's quality are determined, namely – in this order – the received signal strength, the latency, and the data throughput. The latency is only determined if the measured received signal strength exceeds a predefined threshold, while the data throughput is only determined if the measured latency falls below a predefined threshold. If one of the parameters cannot be determined, the worst possible value is assumed, i.e., a received signal strength or data throughput of zero, or a very high latency. Since, in the example presented, a connection to Internet 40 is indeed supposed to exist via the existing data connection, it can be assumed that all of the aforementioned parameters can actually be determined.

[0045] To determine the received field strength, the control unit 13 can refer to corresponding values ​​from the modem 12, which regularly determines the received field strength.

[0046] To determine the latency, the control unit 14 sends a request via modem 12 over the data connection and the internet 40 to server 41, which immediately responds. The times of sending the request and receiving the response at the control unit 14 yield a packet round-trip time, which is a measure of the latency. To mitigate various effects that may affect the packet round-trip time—such as different packet transport paths between the control unit 14 and server 41—the packet round-trip time can be measured multiple times, and an average value can then be calculated. It is important to ensure that the packets used for measuring the packet round-trip time are as small as possible to avoid congestion of satellite 21. Preferably, the maximum size of a packet for determining the packet round-trip time is 64 bytes.

[0047] To determine the data throughput via modem 12, suitable data packets are sent from the control unit 14 to and received from the server 41 in order to test the data rate for both sending and receiving data packets.

[0048] In the next step, 120, the geographic position of aircraft 1 is determined. This can be done using position data obtained either from one of the modems 12 or 13, or from another aircraft system (not shown), for example, based on satellite navigation systems. Based on the position of aircraft 1, it is then determined whether a data connection via the other modem 13 is even possible, in particular whether the satellite network 22 accessible via this modem 13 is available at the geographic position of aircraft 1 (step 130). If this is not the case, the process is aborted; otherwise, it continues with step 140.

[0049] In the next step 140, the existing data connection is disconnected. Although this inevitably interrupts the connection to the Internet 40, the time until a data connection is restored (see steps 170 or 240) is usually so short that this brief interruption is hardly noticeable and is more than compensated for by the advantages achievable with the help of the invention.

[0050] Immediately after disconnecting the existing data connection (step 140), in step 150 a data connection is established via the other modem 13 to one of the satellites 23 of the satellite network 22, namely satellite 23'.

[0051] If, despite the basic availability of the satellite network 22 being established in step 130 (which is checked in step 160), no connection can be established, the data connection previously existing via modem 12 is restored via satellite 21 in step 170 and procedure 100 is terminated.

[0052] In step 180, the received signal strength is determined via the Model 13 – as described previously – and compared with a predefined threshold in step 190. If the received signal strength is below the threshold, the data connection previously established via modem 12 is re-established via satellite 21 in step 170, and procedure 100 is terminated.

[0053] If the received signal strength exceeds the specified threshold, the latency of the data connection via modem 13 is then determined according to the procedure described above (step 200). If the latency thus determined is above a specified threshold (step 210), the data connection previously established via modem 12 is restored via satellite 21 in step 170, and procedure 100 is terminated.

[0054] Otherwise, in step 220, the data throughput via modem 13 is determined (step 220). The procedure for this has also been described above.

[0055] The logic described in steps 180 to 220 can also be applied as early as step 140 to determine the characteristic values ​​of an existing data connection. Furthermore, steps 140 to 220 can also be performed for a third or subsequent modems (not shown), whereby instead of restoring the previously existing data connection (step 170), steps 140 and above are repeated until an attempt has been made to determine the characteristic values ​​for each modem. If, at the end of this loop, characteristic values ​​are only available for the data connection that existed at the beginning of the procedure (step 100), this connection is restored (step 170). Otherwise, the process continues with step 230.

[0056] Upon completion of step 220, three parameters characteristic of the quality of each data connection are available for both or all modems 12, 13 and the data connections that can be established via them: the received signal strength, the latency, and the data throughput. These parameters can be normalized at any time during the process, using specific reference values ​​for each modem 12, 13, which may also vary depending on location and / or time. If normalization is performed early, the same threshold values ​​can be applied to all modems 12, 13 in steps 190 and 210. Otherwise, individual threshold values ​​must be specified for each modem 12, 13, if necessary.

[0057] In step 230, the data connections via modems 12 and 13 are evaluated according to predefined criteria based on the previously determined characteristic values. Using this evaluation, the preferred data connection, or rather the modem 12 or 13 with which this preferred data connection was established, can then be identified.

[0058] In step 240, the preferred data connection is established. This may also be the data connection that already existed at the beginning of the process. If the preferred data connection is the one for which the characteristic values ​​were last determined, it usually still exists at this point and can simply be maintained. Otherwise, the currently existing, but non-preferred, data connection is disconnected and the preferred data connection is established.

[0059] Procedure 100 is now concluded.

[0060] Procedure 100 is preferably executed whenever the position of aircraft 1 has changed by a predetermined amount compared to the position at which procedure 100 was last executed, or a predetermined time has elapsed since the last execution of the procedure. If this is the case, procedure 100 restarts with step 110.

[0061] By regularly checking the data connections via modems 12, 13 according to procedure 100, it can be ensured that the best available data connection is always used for access from aircraft 1 to the Internet 40.

[0062] It is also possible that instead of two separate modems 12, 13, only one modem 12 is provided. In this case, the modem 12 must be suitable for connecting to different satellites 21 or satellite networks 22.

Claims

[1] Method (100) for providing a data connection via satellite (21, 23) on board vehicles, in particular aircraft (1), with an antenna (11) and at least one modem (12, 13) connected thereto for alternative connection to a separate satellite (21) or satellite network (22), comprising the steps: a) If a data connection to a separate satellite (21) or a satellite of a satellite network (22) exists via a modem (12), disconnect this existing data connection; b) Establishing a data connection with a separate satellite (21) or a satellite (23') of a satellite network (22); c) Determination of at least one parameter characteristic of the quality of the data connection; d) Evaluation of the characteristic parameters determined for data connections according to predefined criteria to identify a preferred data connection; e) If the preferred data connection is not the existing data connection, disconnect the existing data connection and establish a data connection with a separate satellite (21) or a satellite (23') of a satellite network (22). [2] Method according to claim 1, characterized by , that at least two modems (12, 13) are connected to the antenna (11), wherein a data connection to a separate satellite (21) or a satellite of a satellite network (22) can only be established via one of the at least two modems (12, 13). [3] Method according to claim 1 or 2, characterized by , that before step a) at least one characteristic of the quality of the data connection is determined for an existing data connection. [4] Method according to any one of the preceding claims, characterized bythat steps a) to c) are repeated until at least one characteristic parameter for the quality of the data connection has been determined for all fundamentally available data connections. [5] Method according to any one of the preceding claims, characterized by , that: - before a data connection is established, the geographical position of the vehicle (1) is recorded, - based on the determined position of the vehicle (1), the basic availability of the separate satellite (21) or a satellite (23) of a satellite network (22) assigned to the data connection is determined, whereby the establishment of a data connection for the subsequent determination of at least one quantity characteristic of the quality of the data connection only takes place if the availability of at least one satellite (21, 23') is determined. [6] Method according to any one of the preceding claims, characterized by, that at least one parameter characteristic of the quality of the data connection includes the received signal strength, the latency and / or the data throughput. [7] Method according to claim 6, characterized by , that the received signal strength, latency and / or data throughput are normalized using reference values ​​specified for each modem, whereby the reference values ​​may be location- and / or time-dependent. [8] Method according to claim 6 or 7, characterized by , that when determining several characteristic parameters for a data connection, the latency is only determined if the received field strength is above a predefined threshold and / or the data throughput is only determined if the latency is below a predefined threshold. [9] Method according to any one of the preceding claims, characterized by , that the procedure (100) is repeated at regular intervals and / or when a change in the geographical position of the vehicle (1) is detected. [10] Method according to any one of the preceding claims, characterized by , that the provided data connection enables access to the Internet (40). [11] Method according to any one of the preceding claims, characterized by that the antenna (11) is directional and / or multi-frequency capable. [12] System (10) for providing a data connection via satellites (21, 23) on board vehicles, in particular aircraft (1), comprising an antenna and at least one modem (11, 12) connected thereto for alternative connection with a separate satellite (21) or satellite network (22) and a control unit (13) connected to the at least one modem (11, 12), characterized by , that the control unit (13) is configured to carry out a method (100) according to one of the preceding claims. [13] System according to claim 12, characterized by, that the control unit (13) and / or at least one of the modems (11, 12) has a position determination module and / or an input for position information from a separate position determination module.

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