TITLE
Airborne Network Extension Cluster
Technical Field
5 The present invention relates to an over-the-horizon communication system comprising at
least two end nodes and at least two airborne network extension nodes, the end nodes and
the network extension nodes being configured to receive and transmit communication, and
providing communication between the end nodes, and methods for using, managing,
deploying and providing said over-the-horizon communication system.
10
Technical Background
The invention discloses a method to manage over-the-horizon communication by use of
network extension nodes. The network extension nodes form a network extension cluster,
with the network extension cluster meaning a network consisting of more than one unit.
15 Over-the-horizon communication systems, also known as beyond-the-horizon
communicating systems, began to be an interesting area of research during the cold war,
starting in the 1950s, and has been considered to be an important area on and off ever
since. This applies both to ground based and airborne systems. Propagation of e.g. radio
waves, radio frequency signals or optical signals is facilitated by unobstructed line of sight,
20 consequently will be limited by the curvature of the earth. Hence, this is limiting for the
possible distance for maintained communication, and in order to solve this problem an overthe-
horizon system can be used. Inexpensive over-the-horizon capable communication
systems have in the last decades returned as an important area of research, and has
become even more important due to the increased use of UAVs, Unmanned Aerial Vehicles.
2 5
A well known approach for providing over-the-horizon communication is by using satellites.
This however, is a solution that often is associated with extensive administrative work and
the availability is often limited. The not absolutely highest prioritized assignments might have
to stand back, making it an unreliable or in some cases even a non existing way of
30 communication. Also, the signals sent to and from satellites often become very weak due to
the long distances, making them easy to block by jamming. This is also a very expensive
way of managing over-the-horizon communication. Cost efficiency and robustness are two of
the most important aspects for feasible over-the-horizon communication systems.
35 Another approach is to use UAVs or other, for this single purpose, advanced platforms able
to receive and transmit e.g. radio frequency signals between nodes in a network. This
approach is not only very expensive but it also requires, for this single purpose only,
operational resources and personnel. This can also lead to operational constraints and
infrastructural dependencies.
Yet another important aspect in order to obtain fast and reliable over-the-horizon
5 communication is the distance between the nodes. The closer the nodes are to each other,
the faster the communication, and the more reliable the communication, becomes. However,
nodes located close to each other include another drawback; it makes it easier for enemies
to locate the sending end node by detecting the radio signal. This is especially critical if the
receiving end node is a missile, a UAV or such, which operates in hostile territory whereby
10 the locating of the transmitting end node enables the enemy to take various precautions.
There are several signal modification techniques available to prevent signal detection and
interception but they often have limiting effects on the data rate that can be transmitted and
they increase the complexity of the system, hence, the cost.
15 One way of addressing a few of the problematic areas related to over-the-horizon
communication is by using the method disclosed in the US patent US5183414. The patent
publication discloses a method for providing high rate over-the-horizon communication using
radio frequency signals for communication between the launch platform and the interface unit
(relay station), and optical fibre communication between the interface unit and an
20 autonomous vehicle platform. The autonomous vehicle platform, supposedly being a missile
or a UAV, is preferably equipped with a real time viewing system for gathering optical data
that can be used for responsive control, real time decision making, damage assessment etc.
The drawback with using an optical fibre for communication is e.g. the limitation of effective
25 range and the difficulties to connect the end optical fibre connected unit to a multidirectional
network. The using of optical fibre is by default limiting for multidirectional communication.
The interface unit and/or the units, connected to each other with optical fibre, also need to be
equipped with spools and/or bobbins, making them heavier and adding extra cost to the
system, not to mention the constraints imposed with respect to manoeuvring. The
30 considerable weight of the interface units also has a negative impact on the ability to keep
the unit airborne, thus making it problematic to maintain the network connectivity over time.
It should also be mentioned that for some applications ionospheric wave propagation or
ground wave propagation can be used as an alternative way for long distance
35 communication. However, none of these approaches are sufficient for time critical systems or
systems where the reliability is essential due to unpredictability and low reliability.
Thus, there is a need for improved systems for over-the-horizon communication.
Summary of Invention
The present invention relates to a system for over-the-horizon communication by use of
5 network extension nodes forming a network extension cluster, and methods for using,
managing, deploying and providing said system. Communication is in this context either
continuously maintained communication or single pieces of information sent, is either
unidirectional or bidirectional and is in the form of data, any type on signal or like.
10 The inventive over-the-horizon communication system is intended to be used above the
operating range for ground based antennas and below the operating range for satellites,
between approximately tens of meters to tens of kilometres above sea level. Hence, the
operating range exceeds the altitude range for high altitude clouds enabling communication
over the clouds where the atmospheric impact is limited.
15
The end nodes can be any type of vehicle, any type of structure, a person, an apparatus or
like which either is the initial transmitter or final receiver of a e.g. radio based transmission.
The end nodes of the over-the-horizon communication system can be located on land, at sea
and/or in the air and are in motion or at rest. The radio network extension nodes are any type
20 of apparatus with the capability to forward or redirect radio based transmission, but also
other means for communication such as e.g. laser can be used. The flexibility of the overthe-
horizon communication system, comprising multiple end nodes and multiple network
extension nodes, is possible due to the simplicity of the system.
25 According to one example of the inventive over-the-horizon communication system the
invention discloses an over-the-horizon communication system comprising at least two end
nodes, the end nodes being configured to receive and transmit communication signals. It
further comprises at least two, in the troposphere and/or stratosphere airborne, network
extension nodes that are communicatively connected to the end nodes and wherein the end
30 nodes are arranged for communication with the network extension nodes and where the
network extension nodes are arranged for bidirectional or unidirectional communication
between the individual network extension nodes and communication with the end nodes,
being either one end node or a plurality of end nodes. Troposphere and/or stratosphere are
in this context equal to the altitude range below the altitude range where satellites
35 communicate with each other. The troposphere and stratosphere reaches up to
approximately 50 km above sea level. Using at least two network extension nodes enables
the over-the-horizon communication system to be flexible and the redundancy, due to the
use of multiple network extension nodes, makes the system reliable. The use of multiple
network extension nodes is essential for the over-the-horizon communication system to work
as intended.
5 According to one example of the over-the-horizon communication system the network
extension nodes are radio network extension nodes, being configured to receive and transmit
radio frequency signals. In this example, also the end nodes are configured to receive andlor
transmit radio frequency signals, wherein the radio network extension nodes are connected
by means of radio frequency based communication to the end nodes for bidirectional or
10 unidirectional communication between the end nodes and the network extension nodes, and
between the different network extension nodes. Using radio signals as means for
communication is a robust and well tested concept, comprising proven technology, thus
enabling an inexpensive concept. The used frequency for communication can be anywhere
in the frequency range between 30 MHz and 100 GHz.
15
According to the inventive over-the-horizon communication system, depending on the
purpose of the communication, or the type of message, data, signal etc. sentlreceived, the
communication can be either unidirectional, meaning that the sending end node, with
sending end node meaning the end node where the communication is initiated, is configured
20 to only transmit communication but never receive communication, or bidirectional, meaning
that the sending end node is configured to both receive and transmit communication.
Generally, the extension nodes have to be configured both to receive communication from an
end node or another extension node and to transmit communication to another extension
node, or to one or several receiving end nodes. However, there are also applications of the
25 inventive system where it is preferable that the network extension nodes are configured for
unidirectional communication. The receiving end node, with receiving end node meaning the
end node intended for receiving the communication sent from the sending end node, or
where there are more than one end node - the receiving end nodes, can either be arranged
for unidirectional communication, only being configured to receive communication, or
30 bidirectional communication, being configured to both receive and transmit communication.
Consequently, if the at least two end nodes both are arranged for bidirectional
communication, the receiving end node is capable to respond to the communication sent
from the sending end node, and the sending end node is capable of receiving the response
sent in reply from the receiving end node. The inventive over-the-horizon communication
35 system is not limited to comprise just two end nodes. It is possible to use both multiple
sending end nodes and multiple receiving end nodes. Also, a sending and/or receiving end
node do not have to communicate with the same network extension nodelnodes
continuously, this may vary over time.
In an example of the inventive over-the-horizon communication system where the network
extension cluster comprises more than two network extension nodes, all extension nodes
5 may not be connected to all other network extension nodes of the network extension cluster.
According to another example of the inventive over-the-horizon communication system the
network extension nodes are unpropelled network extension nodes. In this context,
unpropelled is used as a denomination assigning the unpropelled entity the attribute to not be
10 driven by a motor, the opposite being propelled, or motor driven. Using unpropelled radio
network extension nodes enables the over-the-horizon communication system to be
relatively inexpensive. Rockets and like, using rocket motors, engines driven on pressurized
gas or steam and like, are in this context considered to be unpropelled.
15 According to yet another example of the inventive over-the-horizon communication system
the network extension nodes are arranged to become airborne by means of at least one of
the means in a group of means comprising; deploying a balloon, by being launched in a
trajectory, for example by being fired from a vehicle, and/or by being launched from another
propelled or unpropelled object. In the embodiment where the network extension nodes are
20 arranged to become airborne by means of deploying at least one balloon, for example by
using a mechanism where the end node might deploy a balloon, filled with a gas lighter than
surrounding air, making it ascend from the ground up into the sky. Depending on what type
of balloon that is used and/or what type of gas that is used in order to make the balloon
ascend, the balloon will burst at a certain altitude above sea level. Different balloons have
25 different lifting capacity, thus giving the ascending radio network extension nodes,
comprising balloons, different ascending velocity. The network extension nodes can also
become airborne by being fired by means of some kind of artillery, cannon or such or one or
more than one network extension nodes can become airborne by being released and/or
partitioned from a propelled or unpropelled airborne object such as a UAV, a missile, a
30 rocket, glider, balloon or such. Consequently, the network extension nodes of the over-thehorizon
communication system can be launched from the ground and/or from a ground
based, sea based and/or a flying launch platform and the launch platform can be in motion or
at rest. The launch platforms are defined as all units with the possibility to either execute the
launch or from which the launch can be executed, such as personnel, vehicles, facilities etc.
35
According to another aspect of the inventive over-the-horizon communication system the
network extension nodes are arranged to become airborne by means of using energy stored
in at least one spring or in at least one resilient means, or by means of energy stored as
pressurized gas or steam. For certain embodiments this means of making the network
extension node airborne may be the most advantageous.
5 According to another example of the inventive over-the-horizon communication system the
network extension nodes are arranged to be airborne by means of at least one of the means
in a group of means comprising; a balloon, a parachute and/or a glider or such that enables
the network extension node to stay airborne, during descending or ascending, for a period of
time. By using airborne extension nodes the over-the-horizon communication can be
10 maintained during a longer period of time.
According to another example of the inventive over-the-horizon communication system at
least one of the at least two network extension nodes comprises a GPS receiver and/or
transmitter, and/or at least one of the at least two network extension nodes comprises a
15 temperature and/or a pressure sensor andlor rangefinder and/or altimeter. Equipping the
extension nodes with GPS receivers and/or transmitters and/or pressure and/or temperature
sensors can give important information regarding the positioning etc. of the extension nodes.
According to yet another aspect of the inventive over-the-horizon communication system one
20 of the end nodes can be a satellite.
Network extension nodes can also advantageously be used in order to facilitate
communication with satellites. When communicating with satellites, the most significant
signal losses and the altitudes where the signal is exposed to most interference, is the height
25 range where clouds are present. Clouds are found almost exclusively in the troposphere,
extending up to approximately 20 km above the ground. Some clouds may also be present in
the stratosphere, if so particularly so called Nacreous clouds. The stratosphere is very dry
due to that the vertical transfer is limited by the tropopause. However, not only clouds,
consisting primarily of small water droplets and ice, have limiting effects on different kind of
30 signals and influence the signals in a negative way, e.g. in regards of signal strength. Also
the oxygen and water in the air, having the highest influence at ground level and thereafter
decreasingly, influence the signals. Consequently, in regards of signal strength and
minimized attenuation, the distance a signal has to travel through clouds/water/oxygen
between the transmitter and the satellite is crucial. However, this is most significant at lower
35 altitudes up to and including the altitudes where clouds are present, due to the higher
concentration of oxygen in the air at lower altitudes, and the influence of moist, ice crystals
etc. in the clouds. Approximately 99% of all water present in the atmosphere exists below an
altitude of 20 km. The interference of the signal at altitudes above the clouds is less
significant.
Consequently, one or preferably more than one radio network extension node can be
5 deployed in order to minimize the distance a signal has to travel at altitudes of interference,
meaning lower altitudes and altitudes where clouds are present. This is done according to;
instead of letting the signal travel diagonally from the end node located at land,
through the interfering atmosphere and to the satellite;
letting the signal travel from the end node to the radio network extension nodes,
10 which forms the cluster, through the interfering atmosphere, the radio network extension
nodes being arranged to be located substantially vertically above the end node, and then
letting the signal travel from the cluster to the satellite at an altitude with reduced
atmospheric attenuation.
15 This will not only, according to the previously described advantages with using networks or
clusters of nodes, make the communication more reliable due to redundancy etc., but also
minimize the signal losses and interference due to that the signal will travel a shorter
distance through altitudes of interference.
20 The distinctive characteristics for the examples of the over-the-horizon communication
systems described above can be combined freely.
According to another example of the inventive over-the-horizon communication system the
means for communication is optical, such as by means of laser. By using optical
25 communication between the end node and the extension nodes, or between the extension
nodes, the communication may be conducted in a more efficient way and other components,
if desirable, can be used.
According to one aspect of the invention the invention comprises a method of communicating
30 between at least a first end node and a second end node by using said over-the-horizon
communication system. According to the inventive method, the first end node is
communicating with at least a first network extension node by sending andlor receiving
signals andlor data totfrom at least the first network extension node. The first network
extension node is communicating with at least a second network extension node by sending
35 andlor receiving signals andlor data tolfrom at least the second network extension node and
the first network extension node is communicating with the first end node by sending andlor
receiving signals andlor data tolfrom the first end node. The second network extension node
is communicating with at least the first network extension node by sending and/or receiving
signals and/or data to/from the first network extension node and is communicating with at
least the second end node by sending and/or receiving signals and/or data tolfrom the
second end node. Finally, the second end node is communicating with at least the second
5 network extension node by sending and/or receiving signals and/or data tolfrom the second
network extension node. Both the first and the second end nodes and the network extension
nodes can be connected, for bidirectional or unidirectional communication, with more than
one network extension node. The network extension nodes can also be connected for
bidirectional or unidirectional communication to more than one end node. Consequently, in
10 the aspect of the invention described above may the first end node also be connected for
bidirectional or unidirectional communication to the second network extension node and the
second end node may also be connected for bidirectional or unidirectional communication to
the first network extension node. Both the first and second end nodes, and the first and
second network extension nodes, may also be connected to at least a third network
15 extension node. Additionally, the first, second and third network extension nodes may also
be connected for bidirectional or unidirectional communication to at least a third end node.
The communication previously described may comprise sending and/or receiving any type of
signals andlor data information. A method using the inventive over-the-horizon
communication system enables communicating by using an inexpensive and redundant
20 system.
In an example of a method of managing the over-the-horizon communication system the
method comprises automatic activation and deactivation of the network extension nodes
based on altitude, speed, elapsed time, distance, round trip timing and/or location for each of
25 the network extension nodes comprised in the over-the-horizon communication system.
Using predetermined criteria enables control of which radio network extension nodes of the
over-the-horizon communication system that are active and inactive. For example, this
feature can be used in order to facilitate that all transmitting radio network extension nodes
are located within a predetermined area. Using certain prerequisites for activating and/or
30 deactivating the network extension nodes is referred to as boundary control.
The distance between one end node and one network extension node can be controlled by
using visual sensors and methods for image processing over time, according to well known
principles for a person skilled in the art. Hence, this approach can be used in order to
35 determine the distance between the end node and the network extension node, which in its
turn can be used as decision basis for activation or deactivation.
In another example of a method of managing the over-the-horizon communication system
the method comprises automatic deactivation of the radio network extension nodes, based
on that the means for arranging the radio network extension nodes to be airborne cease to
be active. For example, this feature can be used in order to facilitate that all transmitting
5 radio network extension nodes are located within a predetermined height range. An example
of this is deactivation when an extension node, being airborne by means of a balloon, is
deactivated as the balloon bursts when reaching a certain height.
In an example of a method of providing over-the-horizon communication the method
10 comprises selecting a communication path by using the activated and available network
extension nodes, based on at least one predetermined criteria, wherein the criteria may be
e.g. high signal strength, transfer capacity or low risk of jamming. This feature enables that
best possible communication path, based on current conditions, is chosen. According to
another example of a method of providing over-the-horizon communication, a randomly self-
15 organizing-network is used, wherein the selected and used communication paths are varied
according to a predetermined schedule. This approach is advantageously used in order to
vary selected communication path in order to hamper interception.
The self-organizing-network is a network of multiple network extension nodes wherein the
20 network extension nodes themselves can organize which communication path that is used
based on for example any predetermined criteria, algorithms with adjustable variables or just
randomness. The self-organizing-network can also, based on for example any predetermined
criteria, algorithms with adjustable variables or just randomness, vary which end nodes that
are part of the network, hence are available for the self-organizing-network, at any given
25 time. According to one example of the inventive over-the-horizon communication system, the
communication between the network extension nodes is managed by coordinated
transmission, meaning that there is a predetermined or continuously adjusted plan regarding
how the network extension nodes transmits and receives signals.
30 According to one aspect of the invention, an example of a method of deploying the over-thehorizon
communication system comprises deploying the network extension nodes according
to a predetermined schedule or randomly generated schedule. The method may further
comprise that according to present or predicted availability of network extension nodes
deploy network extension nodes in order to establish a network andlor continuously replacing
35 the network extension nodes of said network and/or launching the network extension nodes
according to a predetermined sequence.
According to yet another example of a method of deploying an over-the-horizon
communication system the method comprises random or continuous deploying of network
extension nodes according to a predetermined schedule or randomly generated schedule.
This can for example be used in order to either establish a network or continuously replacing
5 the network extension nodes in a network. One method may further comprise that the
network extension nodes are deployed according to a randomly generated schedule in order
to obstruct hostile jamming.
According to one example of the invention a method of deploying the over-the-horizon
10 communication system comprises consecutively deploying the network extension nodes in
sequence according to a predetermined prerequisite such as; the sequentially previously
deployed network extension node reaching a predetermined height, reaching a
predetermined distance from a predetermined spot, a combination of reaching a
predetermined height and distance or that a predetermined period of time has elapsed since
15 the sequentially previously deployed network extension node was deployed. In the aspects of
the invention where radio signals are used as means for communication, a method of
deploying the network extension nodes comprising that they are deployed when the radio
frequency signal of the most recently deployed radio network extension node connects to the
sequentially subsequent radio network extension node, can be used. This approach can also
20 be used using optical communication. There are also other prerequisites, depending on
current situation and circumstances, which might be relevant to apply. Preferred prerequisite
for deploying network extension nodes is dependent on prevailing conditions and current
mission.
25 According to another example a method of deploying the over-the-horizon communication
system comprises launching the network extension nodes from at least one location, the
location being the same as for any one of the end nodes or being anywhere in the vicinity of
the route connecting the end nodes.
30 According to yet another example of the invention a method of deploying the over-thehorizon
communication system comprises launching the network extension nodes according
to a predetermined sequence or that the network extension nodes are launched in a
trajectory in at least one direction such that the network extension nodes are launched in a
predetermined or randomly generated pattern.
3 5
According to the invention, the preferred means of communication is by using radio based
communication, using radio frequency signals, for bidirectional or unidirectional
communication between the end nodes and extension nodes and for bidirectional
communication between the extension nodes, but also other means for communication is
possible, e.g. optical communication.
5 The above described examples and aspects of the inventive over-the-horizon communication
system, and methods using said system, is generally just highlighting one specific feature of
the invention. Hence, one embodiment of the invention may comprise the features from more
than one example or aspect of the invention. Also, the invention is not to be seen as limited
by the examples.
10
Brief Description of Drawings
Figure 1 shows a schematic example of an inventive over-the-horizon communication
system;
15 Figure 2 shows a schematic example of an inventive over-the-horizon communication
system, wherein the network extension cluster is being deployed by means of two
unpropelled objects being launched in a trajectory;
Figure 3 shows another schematic example, of an inventive over-the-horizon
20 communication system;
Figure 4 shows a graph indicating the activation and deactivation of extension nodes
being airborne by means of a balloon or like, when being launched over a period of time;
25 Figure 5 shows a graph indicating the activation and deactivation of extension nodes
being airborne by means of a balloon or like, wherein the different balloons or like, for the
different network extension nodes launched, have different ascending speeds, and are being
launched over a period of time:
30 Figure 6 shows a graph indicating the activation and deactivation of extension nodes
being airborne by means of a balloon or like, and thereafter slowly descending by means of a
parachute or like.
It should be added that the following description of the examples is for illustrative purposes
35 only and should not be considered as limiting.
Reference signs
A-G: End nodes A-G
1 : Over-the-horizon communication system
2: Network extension node
5 3: Network extension cluster
4: Cannon or like
5: Network extension nodes, arranged to be airborne by means of parachutes
6: Timelrange curve representing network extension node a according to figure 4
7: Timelrange curve representing network extension node b according to figure 4
10 8: Timelrange curve representing network extension node c according to figure 4
9: Timelrange curve representing network extension node d according to figure 4
10: Timelrange curve representing network extension node e according to figure 4
11: Tirnelrange curve representing network extension node f according to figure 5
12: Timelrange curve representing network extension node g according to figure 5
15 13: Timelrange curve representing network extension node h according to figure 5
14: Timelrange curve representing network extension node i according to figure 6
15: Timelrange curve representing network extension node j according to figure 6
16: Timelrange curve representing network extension node k according to figure 6
20 Detailed Description of the Invention
In the following figures one embodiment per figure of the invention is shown and described,
simply for illustration of one mode of carrying out the invention.
Figure 1 shows a schematic example of the inventive over-the-horizon communication
25 system 1, comprising end nodes A and B and a network extension cluster 3, consisting of
four network extension nodes 2. The network extension nodes 2 are communicatively
connected to end node A and end node B, facilitating over-the-horizon communication
between end node A and B. End node A and B can be either receiving or transmitting end
nodes, and can be arranged for unidirectional or bidirectional communication.
3 0
Figure 2 shows an example of an inventive over-the-horizon communication system 1,
wherein the network extension cluster 3 is being deployed by means of two unpropelled
objects. Further, figure 2 shows a schematic illustration of the inventive over-the-horizon
communication system 3 comprising three end nodes, end node C, end node D and end
35 node E, and network extension nodes 2, wherein the network extension nodes 2, deployed
by means of two unpropelled objects (not shown in picture), are being launched in a
trajectory, wherein each of the unpropelled objects is being split into three network extension
nodes 2. End nodes C, D and E may be different or identical to end nodes A and B. This is
an example of how one unpropelled object, being fired as an artillery piece, grenade or like,
can be split into two or more network extension nodes or one or several network extension
nodes can be released from an unpropelled object. Corresponding arrangements, where one
5 or more than one node is being released from, divided from or like, an unpropelled object,
the unpropelled object being e.g. a rocket, IS also possible.
The sending and/or receiving end nodes C, D and E are communicatively connected to each
other via the network extension nodes 2, forming the inventive over-the-horizon
10 communication system 1. According to figure 2 the unpropelled objects (not shown in
picture), preferably being an artillery piece, is launched by means of artillery, a cannon or
such, in the figure depicted by a schematic cannon 4.
Figure 3 shows another example of the inventive over-the-horizon communication system 1
15 wherein end node F is represented by a ship and end node G is represented by another,
smaller ship. End nodes F and G may be different or identical to end nodes A - E, and are
not limited to being ships. The inventive network extension cluster 3 is according to the
embodiment of the invention established by means of network extension nodes 5 arranged to
be airborne by means of parachutes after being fired from end node F, wherein end node F
20 in figure 3 is depicted as a ship.
Figure 4 shows how the implementation of one example of the over-the-horizon
communication system can be depicted in a graph.
25 Figure 4 shows a graph indicating the activation and deactivation of network extension
nodes, being airborne by means of a balloon or like, when being launched over a period of
time. The extension nodes a, b, c, d, e each represented by a range curve 6, 7, 8, 9, 10 in
figure 4, are launched according to a predetermined and regular time interval. The y-axis
represents the communication range for the extension nodes.
30
The over-the-horizon communication system is operational when at least two network
extension nodes are active; in the graph in figure 4 indicated by the cluster coverage range
CC, and the coverage margin CM. The Coverage margin CM is used in order to compensate
for uncertainties in range.
3 5
For further clarification, the following schematic example, according to figure 4, can be
assessed. For an extension node b being launched as number two in an order of launched
network extension nodes, being represented by a range curve 7 in figure 4, the following
applies:
fb,o indicates the time the network extension node b is launched,
5 tb,act indicates the time the network extension node b is activated,
tb,acl - tb.0 = Atb.ac1 indicates the time passed from tb.0 until the network extension
node b is activated,
tb.deact indicates the time the network extension node b is deactivated,
tb.deact - tb,act = Atb.aclive indicates the period of time were the extension node b is active.
10
If Atb indicates a time passed since tbmo.
If tb,ac>t Atbt he extension node b is not yet activated,
If tz,act < At2 < tzadeactth e extension node b is activated,
15 If Atb > tb,deacthe extension node b is deactivated.
According to figure 4, at t~ the extension nodes a, b, c are active. Extension node d has just
been launched and has not yet reached the Activation range, thus not yet been activated.
20 When the network extension nodes, according to the example in figure 4 being airborne by
means of at least one balloon, reaches the deactivation range they are either automatically
deactivated or have lost connection to the other network extension nodes andlor end nodes,
and the balloon either bursts or continue to ascend further, depending on what type of
balloon that is used. Also other means than balloons for making and keeping the network
25 extension nodes airborne is possible.
Activation and deactivation linked to range is but one example of means possible for
controlling the activation and deactivation of the network extension nodes.
30 Figure 5 shows how the implementation of another example of the over-the-horizon
communication system can be depicted in a graph.
Figure 5 shows a graph indicating the activation and deactivation of extension nodes being
airborne by means of a balloon or like, wherein the different balloons or like, for the different
35 network extension nodes launched, have different ascending speeds, and are being
launched over a period of time. According to figure 5 the network extension nodes f, g, h,
each represented by a range curve 11, 12, 13 in figure 5, are launched with different
ascending speed, as can be understood from the different slope of each network extension
node's range curve 11, 12, 13. In figure 5 the ascending speed of each network extension
node is adapted so that each network extension node is active within the same period of
time, in figure 5 being indicated by Atactiv,, the time between Activation and Deactivation.
5 Activation and Deactivation do not necessarily have to be linked to a certain time or time
passed. Also parameters as altitude, distance etc. can be used.
This is but one example of how the different properties of the network extension nodes,
where the properties are depending on e.g. used means for making the network extension
10 node airborne, used means for keeping the network extension node airborne, the design of
the network extension node as such etc. can be tailored in order to fulfil any specific
requirements of the inventive over-the-horizon communication system. In this example the
requirement possibly is to have an active over-the-horizon communication system,
comprising three network extension nodes, active at a certain time indicated by Atadive.
15 Before the network extension nodes reaches the time for activation they are not yet activated
and when they have passed the time for deactivation they are deactivated.
Figure 6 shows how the implementation of a further example of the over-the-horizon
communication system can be depicted in a graph.
20
Figure 6 shows a graph indicating the activation and deactivation of extension nodes being
airborne by means of a balloon or like, and thereafter slowly descending by means of a
parachute or like. According to the graph, assumingly depicting a scenario where the network
extension nodes are arranged to be airborne by means of a balloon, the network extension
25 nodes ascend until they reach a height where either the balloon or like bursts or the network
extension node is released from the balloon arrangement. When reaching maximum
coverage range, indicated by the upper limit of the upper coverage margin, CM, the network
extension nodes start to slowly descend, preferably by means of a parachute or like. The
network extension nodes are being activated as they reach the activation level on their way
30 up, and deactivated as the reach the deactivation level on their way down. The deactivation
level can be predetermined, based on various parameters such as time passed since
activation, height etc., and can be either within the lower coverage margin CM or as in the
example in figure 6, below the coverage margin. The deactivation can also be individually
adapted for the network extension nodes according to prevailing circumstances. The
35 deactivation may e.g. be affected by that the wind is carrying the network extension node in
undesirable direction.
The slow descending by means of a parachute or like may be initiated by the balloon
bursting, or loosing lifting capacity in some other way, in a controlled or spontaneous way.
The deployment of the parachute may be initiated for example; by the balloon bursting, by
the network extension node being released at a certain height, by the ascending network
5 extension node reaching a predetermined height, automatically as the network extension
nodes starts to descend, by acceleration or according to other method.
As will be realised, the invention is capable of modification in various obvious respects, all
without departing from the scope of the appended claims. The figures 1-6 are only intended
10 to demonstrate a few selected examples of how the inventive over-the-horizon
communication system can be used and how it can be controlled, and are not to be
considered as limiting the scope of the invention. Accordingly, the drawings and the
description thereto are to be regarded as illustrative in nature, and not restrictive.
15 All figures are schematically illustrated
The Swedish Patent Office PCTISE~O~~0 50867
PCT International Application 05-06-2014
17
CLAIMS
1. An over-the-horizon communication system (I)co mprising at least two end nodes (AG),
the end nodes (A-G) being configured to receive and transmit communication
signals, and providing communication between the at least two end nodes (A-G),
wherein said over-the-horizon communication system (I)
further comprises at least two, in the troposphere andlor stratosphere airborne,
network extension nodes (2;5) that are communicatively connected to the end nodes
(A-G) and wherein the end nodes (A-G) are arranged for communication with the
network extension nodes (25) and the network extension nodes (2;5) are arranged
for communication between the individual network extension nodes and
communication with the end nodes (A-G),
characterized in that
at least one of the at least two network extension nodes (2;5) comprises at least one
of:
- GPS transmitterlreceiver,
- temperature sensor,
- pressure sensor,
- rangefinder andlor
- altimeter.
20
2. An over-the-horizon communication system (I) according to claim 1, wherein
the network extension nodes (2;5) are configured to receive and transmit radio
frequency signals, and the end nodes (A-G) are configured to receive and transmit
radio frequency signals, wherein the radio network extension nodes are connected by
means of radio frequency based communication to the end nodes (A-G) for
communication.
3. An over-the-horizon communication system (1) according to claim 1, comprising
means for communication between at least one of the end nodes (A-G) and at least
one the network extension nodes (2;5), andlor for communication between at least
two of the network extension nodes (2;5),a nd wherein the means for 'communication
are optical, such as by means of laser.
4. An over the-horizon-communication system (1) according to any of the proceeding
3 5 claims, wherein
AMENDED SHEET
the communication between the end nodes (A-G) and the network extension nodes
(2;5) are either bidirectional or unidirectional and the communication between the
network extension nodes (2;5)a re bidirectional or unidirectional.
5 5. An over-the-horizon communication system (1) according to any of the proceeding
claims, wherein
the network extension nodes (2;5) are unpropelled network extension nodes (2;5).
6. An over-the-horizon communication system (1) according to any of the proceeding
10 claims, wherein
the network extension nodes (2;5) are arranged to be airborne by at least one of the
means in a group of means comprising;
a balloon, a parachute, a glider.
15 7. An over-the-horizon communication system (1) according to any of the proceeding
claims, wherein
the network extension nodes (2;5) are arranged to become airborne by at least one of
the means in a group of means comprising;
deploying a balloon, being launched in a trajectory, being launched from a propelled
or unpropelled object.
8. A method of communicating between at least a first end node (A-G) and a second
end node (A-G) by using said over-the-horizon communication system (I)co,m prising
the first and second end nodes (A-G) wherein,
the first end node (A-G) is communicating with at least a first network extension node
(25) by sending andlor receiving signals andlor data tolfrom at least the first network
extension node (2;5),
the first network extension node (2;5) is communicating with at least a second
network extension node (2;5) by sending andlor receiving signals andlor data tolfrom
at least the second network extension node (2;5) and the first network extension node
(2;5) is communicating with the first end node (A-G) by sending andlor receiving
signals andlor data tolfrom the first end node (A-G),
the second network extension node (2;5) is communicating with at least the first
network extension node (2;5) by sending andlor receiving signals andlor data tolfrom
the first network extension node (2;5) and is communicating with a second end node
(A-G) by sending andlor receiving signals andlor data tolfrom the second end node
(A-GI,
AMENDED SHEET
and the second end node (A-G) is communicating with at least the second network
extension node (2;5) by sending andlor receiving signals andlor data tolfrom the
second network extension node (2;5),w herein
the method comprises automatic activation and deactivation of the network extension
nodes (25) based on at least one of:
- altitude,
- speed,
- elapsed time,
- distance, andlor
- location,
for each of the network extension nodes (2;5) comprised in the over-the-horizon
communication system (1 ).
9. A method of providing over-the-horizon communication according to claim 8 wherein
the method comprises
selecting a communication path by using the activated and available network
extension nodes (2;5), based on at least one predetermined criteria, wherein the
criteria is at least one of the following:
high signal strength; and/or
transfer capacity; and/or
low risk of hostile jamming.
10. A method of providing over-the-horizon communication according to any of claim 8 to
9 wherein the method comprises
25 that used communication paths are varied according to a predetermined schedule.
11. A method of deploying the over-the-horizon communication system (1) according to
any of claim 8 to 10 wherein
the method comprises deploying the network extension nodes (23) according to a
predetermined schedule or randomly generated schedule.
12. A method of deploying the over-the-horizon communication system (1) according to
any of claim 8 to 1 I wherein
the method comprises consecutively deploying the network extension nodes (2;5) in
sequence according to a predetermined prerequisite such as;
the sequentially previously deployed network extension node (2;s) reaching a
predetermined height andlor distance; and/or
a predetermined period of time has elapsed since the sequentially previously
deployed network extension node (2;5) was deployed.