A method for detecting the location of a source of interference signal

Abstract

The present invention provides a method for locating a source of a jamming signal received by a first satellite which communicates with a second satellite over ISL. The method comprises detecting the jamming signal presence (1) on a transponder channel of the first satellite; determining the coverage area (2) from where the jamming signal is transmitted; prioritizing the jamming signals (4) with respect to the service types; sending to the second satellite a scanning command (5) in relation with the carrier frequency of the jamming signal; configuring the receiver settings of the second satellite and starting the scanning task (6) to scan signals to lock its signal filter on the carrier frequency of the jamming signal; when the carrier frequency and bandwidth of the jamming signal are found, sending a found information to the first satellite (7); after receipt of found information, sending a locating command (8) including data of the jamming signal to the second satellite; collecting sample data from the coverage area (10) with the locked filter of the second satellite and transmitting the collected data to the first satellite; finding the location of the source of the jamming signal (11) by using positioning algorithms according to the collected data.

Description

[0001] DESCRIPTION

[0002] A METHOD FOR DETECTING THE LOCATION OF A SOURCE OF INTERFERENCE SIGNAL

[0003] FIELD OF THE INVENTION

[0004] The present invention relates to a method for detecting the location of a source of interference / jamming signal.

[0005] BACKGROUND OF THE INVENTION

[0006] In the communication area, the interference can be defined as receipt of data including further information additional to the information intended to be conveyed. Accordingly, transmission of the desired communication signal including unwanted product can occur with two different ways, either the desired signal itself is corrupted or another signal is interfered to the desired signal. The signal which is interfering into the desired communication signal is defined as jamming / interfering signal.

[0007] By the development of the technology rapidly, too many devices transmitting different signal waves are in the use. Accordingly, the presence of jamming signals (intentionally or deliberately) in satellite communication networks has increased considerably. Since satellite coverage areas are very large, many terminals in this coverage area can be disturbed by a jamming signal or they may completely lose their communication capabilities.

[0008] Since the jamming signal corrupts the desired communication signal and prevents transmission of the information without unwanted products, to end the interference, the location of the source of the jamming signal should be determined. In the prior art, this determination is done with some terrestrial systems. However, the large coverage area of the satellites makes it very difficult to determine the location of the source of the jamming signal. For this reason, it is almost impossible to detect the interference to the services on the GEO satellites with terrestrial systems. In addition, it is not possible to find the source of interference from the territory of a third country with terrestrial systems. All the problems mentioned above have made it necessary to make an innovation in the relevant technical field as a result.

[0009] BRIEF DESCRIPTION OF THE INVENTION

[0010] The present invention relates to a method for determining the location of a source of a jamming signal to eliminate the above-mentioned disadvantages and bring new advantages to the relevant technical field.

[0011] An object of the invention is to develop a method for determining the location of a source of a jamming signal.

[0012] Another object of the invention is to develop a method for determining the location of a source of a jamming signal interfering to the communication signals of a GEO (Geosynchronous Equatorial Orbit) satellite.

[0013] Yet another object of the invention is to develop a method for determining the location of a source of a jamming signal which does not cause third country border violation problems.

[0014] The other object of the invention is to develop a method that automatically detect interferences against GEO satellites without the need for any satellite operator intervention.

[0015] Another object of the invention is to develop a method that will enable the locations of interference sources to be found quickly and efficiently.

[0016] To achieve all the objects mentioned above and that will emerge from the following detailed description, the present invention relates to a method which is suitable for being used with a communication network comprising

[0017] §at least one first satellite comprising at least one antenna, at least one receiver chain, at least one IMUX, at least one HPA chain, at least one OMUX and at least one control unit and,

[0018] §at least one second satellite with at least one frequency filter, wherein the first satellite has certain computing capability to generate commands for the second satellite to perform certain tasks and wherein the first satellite is able to send / receive messages to / from second satellite over inter satellite links and wherein the method provides determination of the location of a source of a jamming signal coming to the first satellite. The method comprises the steps of:

[0019] • detecting a jamming signal presence on a transponder channel of the first satellite by the first satellite, from the power measurements of the signals received from the coverage areas of the first satellite and divided into channels by the IMUX of the first satellite;

[0020] • determining, by the first satellite, the coverage area from where the jamming signal is transmitted;

[0021] • checking whether more than one transponder channel is affected by the jamming signal and if there are more than one transponder channel that is affected by the detected jamming signal, prioritizing the jamming signals with respect to the service types of the transponder channels;

[0022] • sending to the second satellite, which is passing over and / or about to pass over the determined coverage area, a scanning command in relation with the carrier frequency of the detected jamming signal from the first satellite;

[0023] • after receipt of the scanning command, by the second satellite, configuring the receiver settings of the second satellite and starting the scanning task to scan signals to lock its signal filter on the carrier frequency of the jamming signal;

[0024] • when the carrier frequency and bandwidth of the jamming signal are found by the second satellite during performing scanning task, sending a found information from the second satellite to the first satellite over ISL;

[0025] • after receipt of found information, sending a locating command including data of the jamming signal from first satellite to the second satellite;

[0026] • after receipt of the locating command, configuring the receiver settings of the second satellite (9)

[0027] • after configuration, by the second satellite, collecting sample data from the coverage area with the locked filter of the second satellite and transmitting the collected data to the first satellite over ISL;

[0028] • finding the location of the source of the jamming signal by using positioning algorithms according to the collected data via control unit of the first satellite.

[0029] Thanks to the method of the present invention, the location of a source of a jamming signal is able to be determined by aerially. Therefore, scanning of much more large terrestrial area is able to be performed by eliminating third country border problems. Accordingly, effectively and efficiently determination of the location is able to be provided in a quick manner by optimizing the use of the second satellites.

[0030] DESCRIPTION OF THE DRAWINGS

[0031] Exemplary embodiment of the method developed according to the present invention is illustrated in the attached drawings, wherein:

[0032] Figure 1 is an exemplary flowchart of the method of the present invention up to end of scanning command task.

[0033] Figure 2 is an exemplary flowchart of the method of the present invention following the end of the scanning command task.

[0034] All the parts illustrated in the drawings are individually assigned a reference numeral and the corresponding terms of these numbers are listed as follows:

[0035] 1 detecting a jamming signal presence

[0036] 2 determining the coverage area

[0037] 3 more than one transponder channel is affected

[0038] 4 prioritizing the jamming signals

[0039] 5 sending to the second satellite a scanning command

[0040] 6 configuring the receiver settings of the second satellite and starting scanning

[0041] 7 sending a found information from the second satellite to the first satellite

[0042] 8 after receipt of found information, sending a locating command

[0043] 9 after receipt of the locating command, configuring the receiver settings of the second satellite

[0044] 10 collecting sample data from the coverage area

[0045] 1 1 finding the location of the source of the jamming signal

[0046] 12 generating a first message with respect to the scanning command

[0047] 13 sending the first message from the first satellite to the second satellites

[0048] 14 generating a second message in response to the first message

[0049] 15 generating a second message in response to the first message

[0050] 16 selecting the second satellites that are able to perform scanning command

[0051] 17 generating a first message with respect to the locating command

[0052] 18 selecting the second satellites that are able to perform locating command

[0053] 19 send ending command to the other second satellites 20 recording all parameters related to the interference signal in a catalogue

[0054] 21 need to terminate scanning

[0055] DESCRIPTION OF THE INVENTION

[0056] In the communication area, the communication signal transmitted from a device (for instance from a satellite) can be exposed to jamming signals intentionally or unintentionally. This jamming signal causes the transmitted communication signal being corrupted and accordingly the receipt communication signal can have additional unwanted products and / or missing information. To eliminate this situation, the location the source of the jamming signal should be determined. In the prior art, some terrestrial systems are used for locating the jamming signal. However, these systems do not effectively locate the jamming signal and can cause third country border problems. Additionally, these systems are insufficient to locate jamming signals interfering with the communication signals transmitted from the satellites, especially GEO satellites. For that reason, the present invention provides a method for determining the location of a source of a jamming signal.

[0057] The method developed by the invention is suitable for use with a communication network comprising at least one first satellite (preferably a GEO satellite) comprising at least one antenna, at least one receiver chain, at least one IMUX (Input Multiplexer), at least one HPA (High Power Amplifier) chain, at least one OMUX (Output Multiplexer) and at least one control unit (for example OBC [OnBoard Computer]) and, at least one second satellite (preferably a LEO satellite) with at least one frequency filter, wherein the first satellite has certain computing capability to generate commands for the second satellite to perform certain tasks and wherein first satellite can send / receive messages to / from second satellite over inter satellite links (ISL). The task assignments may be individual, where one second satellite is assigned to perform a task, or group-based, where a group of second satellites are assigned to perform a task collaboratively. Preferably, second satellite is able to move with respect to earth in its orbit. The method of the present invention, exemplary flowcharts of which are given in figures 1 and 2 and which provides determination of the location of a source of a jamming signal comprises the steps of:

[0058] • detecting a jamming signal presence (1 ) on a transponder channel of the first satellite by the first satellite from the power measurements of the signals received from the coverage areas of the first satellite and divided into channels by an IMUX (Input Multiplexer) of the first satellite;

[0059] • determining, by the first satellite, the coverage area (2) from where the jamming signal is transmitted; • checking whether more than one transponder channel is affected (3) by the jamming signal and if there are more than one transponder channel that is affected by the detected jamming signal, prioritizing the jamming signals (4) with respect to the service types;

[0060] • sending to the second satellite, which is passing over and / or about to pass over the determined coverage area, a scanning command (5) in relation with the carrier frequency of the detected jamming signal from the first satellite;

[0061] • after receipt of the scanning command, configuring the receiver settings of the second satellite and starting scanning (6) signals to lock its signal filter on the carrier frequency of the jamming signal by the second satellite;

[0062] • when the carrier frequency and bandwidth of the jamming signal are found by the second satellite, then sending a found information from the second satellite to the first satellite (7) over ISL;

[0063] • after receipt of found information, sending a locating command (8) including data of the jamming signal from first satellite to the second satellite;

[0064] • after receipt of the locating command, configuring the receiver settings of the second satellite (9);

[0065] • after configuration, collecting sample data from the coverage area (10) with the locked filter of the second satellite and transmitting the collected data to the first satellite over ISL;

[0066] • finding the location of the source of the jamming signal (11 ) by using positioning algorithms (TDoA [Time Difference of Arrival], FDoA [Frequency Difference of Arrival], AoA [Angle of Arrival], etc.) according to the collected data via control unit of the first satellite.

[0067] In the first satellite, signals received from a coverage (service) area are received with an antenna serving this coverage area. Received signals pass through the receiver chain and divided into channels with much narrower bandwidth (i.e., 36 MHz, 40 Mhz, 72 MHz, 96 Mhz etc.) in the IMUX. These channels can be referred as transponder channels. Transponder channels are amplified in HPA chain and transmitted to the OMUX after the necessary frequency change (up-conversion or down-conversion) operations are performed by HPA chain. Channels collected in OMUX are directed to the relevant antenna depending on their coverage area for re-transmission. In the received signals there can be jamming signals that disturb the received signals. The presence of the jamming signal in a transponder channel should be detected and this is done by handling the power measurements performed in the first satellite. Accordingly, eliminate these jamming signals, the location of the source of the jamming signals should be determined. To determine the location, the coverage area where the jamming signal is transmitted should be determined. Whichever transponder channel has a jamming signal, the antenna it is connected to and the coverage area it is connected to can be known. The coordinates of the coverage area that the antennas serve are certain and do not change. In this way, it is known which transponder channel received this signal from which coverage area. Accordingly, first satellite set communication with the second satellite which is passing over and / or about to pass over the determined coverage area, send commands to search and get data related to the location of the source of the jamming signal by giving data of the jamming signal, receive and process data related to the location of the source of the jamming signal and found by the second satellite by determining the intersection area between the coverage area and the area where the second satellite detected the jamming signal, and finally determine the location of the source of the jamming signal by performing positioning algorithms (during search, the receiver of the second satellite performs frequency scanning and finds the carrier frequency of the jamming signal, locks the signal filter to the found carrier frequency and collect samples for locating process). With respect to the method provided by the present invention, location detection is done by two different satellites that are communicating with each other over ISL. Therefore, locating is able to be performed aerially by scanning much more large terrestrial area. This provides effectiveness and also eliminates third country border problems.

[0068] In a preferred embodiment of the invention, detecting a jamming signal presence (1 ) on a transponder channel step further comprises

[0069] • separating signals received from the coverage area of the first satellite into narrowband transponder channels,

[0070] • measuring power of each transponder channel and sending these measurements to the control unit,

[0071] • comparing these measurements with a threshold level for each transponder channel by control unit,

[0072] • detecting the presence of a jamming signal on this transponder channel if the threshold level of that transponder channel is exceeded.

[0073] The threshold level is obtained by converting the permissible IFD (Input Flux Density) limit (this value is known and entered before) in the control unit to the permissible power measured at the antenna interface, and then finding the limit value of the measured power in the transponder channel. With respect to the Equations 1 and 2 given below: Prx= PIFD+ 10 log @ + Gant+ 30 (dBm) (1 ) wherein Prxis Satellite Input Power at antenna input interface(dBm), wherein PIFDis Input Power Flux Density (cLBW! m2) , wherein A is the Wavelenght(m) of the received signal with the related antenna, wherein Gantis Antenna Gain(dBi). TCN = rx + Aten (2) wherein PTCis Nth Transponder Channel TC) power at measurement point, wherein Aten is total gain between antenna input interface and TC power measurement point n

[0074] As mentioned above, the presence of a jamming signal may occur on more than one transponder channel from the same coverage area or from different coverage areas. The transponder channel with the interfering signal can carry different services. These can be critical services such as safety critical (SC), mission critical (MC) or commerce critical (CC), or they can be non-critic services (NC). However, when we consider factors such as the number of terminals receiving service from that transponder channel and QoS values, it gives the result that not all transponder channels have the same degree of importance. Since satellites cannot perform all assignments at the same time, they put them in an order and work accordingly. Therefore, it is more important to find the location of the interference source in a transponder channel with a high priority level. Accordingly, in another preferred embodiment of the present invention, the prioritizing the jamming signals (4) step further comprises,

[0075] • listing all interfering transponder channels with respect to service types and the number of served terminals,

[0076] • ordering the list with respect to service types (for instance SC>MC>CC>NC) and maximum number of served terminals (for instance from maximum to minimum for each service type)

[0077] • handling the jamming signals with respect to the ordered list.

[0078] An example of an interfering transponder channels list and an ordered list is given below table 1 a and 1 b respectively. The service types and diversity can be in a dynamic structure and can be changed if desired.

[0079] Table 1a - An exemplary interfering transponder channels list

[0080] Table 1 b - An exemplary ordered list

[0081] Thanks to the embodiment, in the case of more than one transponder channel that is affected (3) by the detected jamming signal, the handling of these is able to be performed much more effectively. Since there are more than one second satellite that the first satellite can communicate and since not all of these second satellites may be suitable for location determination, in a preferred embodiment, before sending to the second satellite a scanning command (5), second satellites which will perform scanning command are selected. As shown in figure 1 , this selection is done by • generating a first message with respect to the scanning command (12) and containing information related to the transponder channel that the jamming signal is detected, related to the priority of the detected jamming signal and related to the first satellite, for each coverage area and transponder channel where jamming signal is detected, by first satellite,

[0082] • sending the first message from the first satellite to the second satellites (13) via ISL,

[0083] • by receipt of the first message, generating a second message in response to the first message (14) by the second satellites containing information related to the second satellite,

[0084] • sending the second message from the second satellites to the first satellite (15),

[0085] • by receipt of the second message, decoding and recording the content of the second message for evaluation in control unit,

[0086] • by evaluating the second message content with respect to the predefined conditions via control unit, selecting the second satellites that are able to perform scanning command (16),

[0087] • sending selecting information to the second satellites with scanning command.

[0088] The first satellite detects and measures how many interfering / jamming signals it receives in which coverage area, on which transponder channel or channels. In addition, the detected interfering signals trigger a task and the first messages regarding the interfering signals are produced for each coverage area and transponder channel related with the detected interfering signals. Thanks to the above-mentioned steps, available second satellites that the first messages desired to be sent are able to be determined easily and securely. Therefore, location detection can be performed much more quickly by eliminating or minimizing the problems such as overload of a satellite, unwanted waiting time, etc. that can occur due to non-selection. After receiving scanning command, second satellites configure their “receiver” settings based on the prioritized transponder channel bandwidth and coverage area. Then the second satellite receiver starts scanning to lock on the carrier frequency of the interfering signal by setting the Search Filter Bandwidth Size according to the first message content. All selected second satellites can scan the entire transponder channel bandwidth starting from the same starting and ending point, or it can be requested that each second satellite search a certain part by dividing the transponder channel bandwidth by the total number of assigned second satellites. Every second satellite sends the area where it detected the jamming signal to the first satellite for the determination of the intersection of these areas together with the determined coverage area. Preferably, first message comprises at least one entity of the entity set comprising transponder channel and related coverage area information on which the interfering has become, the bandwidth of that transponder channel (MHz), the center frequency of that transponder channel (MHz), input power of the repeater of the first satellite, input flux density of the first satellite, boundary of that coverage area (x, y, z) and the priority value that is assigned to that transponder channel. Preferably, the second message comprises at least one of the below mentioned information:

[0089] • available frequency scan bandwidth (starting and finish frequency points of the scan bandwidth) of the second satellite (this information shows whether the bandwidth of the jamming signal fits the available frequency scan bandwidth of the second satellite or not)

[0090] • Two Lines Elements (TLE) of the second satellite (orbital position and velocity information)

[0091] • available resource (such as computing capability, storage amount, spectrum etc.) (this information shows whether there is enough resource in the second satellite to perform the scanning command or not)

[0092] • available power (this information shows whether there is enough power in the second satellite to perform the scanning command or not)

[0093] • properties of the antenna of the second satellite such as gain, beamwidth (for example larger beamwidth provided by the second satellite ensures scanning of larger geographic area)

[0094] • slew rate of the second satellite (this information shows ability of the second satellite to steer in roll and pitch directions which ensures effectiveness of the scanning)

[0095] • previously assigned task (for instance performing of previously assigned scanning command) information (this information shows whether there is a previously assigned scanning activity in the second satellite or not)

[0096] • average time that is required to spent in the targeted coverage area.

[0097] These information gathered from different second satellites by reception of the second message are compared to each other via control unit of the first satellite by scoring these information highest value to lowest value from the best condition ensuring the best scanning to the worst condition (by decoding, recording and evaluating the content of the second message as mentioned above). An exemplary scoring table is given below in table 2. Table 2 - Scoring table related to the information comparison of the second message

[0098] After scoring of the information received by the second message, the control unit clusters the second satellites with respect to the scores. Preferably the clustering is performed with the information received by the second message, uncompleted scanning task status data and estimated completion time of the scanning task (this scanning task is directly related with the travel of a second satellite within the coverage area of the first satellite and accordingly the scanning time is related to the travel duration of the second satellite within the coverage area of the first satellite) of the second satellites. During clustering, the second satellites having minimum jamming signal carrier frequency detection time (in other words the time required for the second satellite to perform the scanning command and to find directly the carrier frequency of the jamming signal, this time is calculated by the related second satellite according to the position and coverage area information provided from the first satellite together with its own coverage area information and send to the first satellite within the second message) and jamming signal source locating time (in other words the time required for the second satellite to perform the locating command and to find directly the location of the jamming signal, this time is calculated by the related second satellite according to the position and coverage area information provided from the first satellite together with its own coverage area information and send to the first satellite within the second message) are determined and clustered with respect to the scoring values. Accordingly, clustered second satellites that can complete the scanning as soon as possible can be selected to perform scanning command. Thanks to clustering the second satellites and selecting the sets of second satellites which are estimated as performing the scanning command within the shortest time while meeting all other necessary parameters, scanning of the carrier frequency of the detected jamming signal is able to be performed effectively, efficiently and quickly by optimising use of the second satellites.

[0099] Furthermore, since there are more than one second satellite that first satellite can communicate and since not all of these satellites may be suitable for location determination, in a preferred embodiment, before sending a locating command (8) to the second satellite, second satellites which will perform locating command are selected. As shown in figure 2, this selection is done by

[0100] • generating a first message with respect to the locating command (17) and containing information related to the transponder channel that the jamming signal is detected, related to the priority of the detected jamming signal and related to the first satellite, for each coverage area and transponder channel where jamming signal is detected, by first satellite,

[0101] • sending the first message from the first satellite to the second satellites (13) via ISL,

[0102] • by receipt of the first message, generating a second message in response to the first message (14) by second satellites and containing information related to the second satellites, • sending the second message from the second satellites to the first satellite (15),

[0103] • by receipt of the second message, decoding and recording the content of the second message for evaluation in control unit,

[0104] • by evaluating the second message content with respect to the predefined conditions via control unit, selecting the second satellites that are able to perform locating command (18),

[0105] • sending selecting information to the second satellites with locating command.

[0106] The first satellite detects and measures how many interfering / jamming signals it receives in which coverage area, on which transponder channel or channels. In addition, the detected interfering signals trigger a task and the first messages regarding the interfering signals are produced for each coverage area and transponder channel related with the detected interfering signals. Thanks to the above-mentioned steps, available second satellites that the first messages desired to be sent are able to be determined easily and securely. Therefore, location detection can be performed much more quickly by eliminating or minimizing the problems such as overload of a satellite, unwanted waiting time, etc. that can occur due to non-selection. After receiving locating command, second satellites configure their “receiver” settings accordingly to the first message for performing locating command. Then the second satellites’ receivers collect sample data (area data where the jamming signal is detected by the second satellite within the coverage area of the second satellite intersecting with the determined coverage area of the first satellite) from the coverage area with their filters locked to the interference carrier in the scanning mode and transmit it to the first satellite over ISL. The first satellite finds the location of the interference source using positioning algorithms (TDoA, FDoA, AoA etc.) running on the control unit by determining the intersection of all sample data received from all second satellites.

[0107] Preferably, first message comprises at least one entity of the entity set comprising transponder channel and related coverage area information on which the interfering has become, the bandwidth of that transponder channel (MHz), the center frequency of that transponder channel (MHz), input power of the repeater of the first satellite, input flux density of the first satellite, boundary of that coverage area (x, y, z) and the priority value that is assigned to that transponder channel. Preferably, the second message comprises at least one of the below mentioned information:

[0108] • available frequency scan bandwidth (starting and finish frequency points of the scan bandwidth) of the second satellite (this information shows whether the bandwidth of the jamming signal fits the available frequency scan bandwidth of the second satellite or not; because if the bandwidth of the jamming signal is out of the range of the working frequency of the second satellite, second satellite cannot find the location of that jamming signal)

[0109] • Two Lines Elements (TLE) of the second satellite (orbital position and velocity information)

[0110] • available resource (such as computing capability, storage amount, spectrum etc.) (this information shows whether there is enough resource in the second satellite to perform the locating command or not)

[0111] • available power (this information shows whether there is enough power in the second satellite to perform the locating command or not)

[0112] • properties of the antenna of the second satellite such as gain, beamwidth (for example larger beamwidth provided by the second satellite ensures scanning of larger geographic area, since larger beamwidth provides larger footprint; and accordingly location detection is able to be performed much more faster)

[0113] • slew rate of the second satellite (this information shows ability of the second satellite to steer in roll and pitch directions which ensures effectiveness of the locating)

[0114] • previously assigned task (for instance performing of previously assigned locating command) information (this information shows whether there is a previously assigned locating activity in the second satellite or not)

[0115] • average time that is required to spent in the targeted coverage area.

[0116] These information gathered from different second satellites by reception of the second message are compared to each other via control unit of the first satellite by scoring these information from highest value to lowest value and from the best condition ensuring the best locating to the worst condition (by decoding, recording and evaluating the content of the second message as mentioned above). An exemplary scoring table is given above in table 2.

[0117] After scoring of the information received by the second message, the control unit clusters the second satellites with respect to the scores. Preferably the clustering is performed with the information received by the second message, uncompleted scanning task status data and estimated completion time of the locating task (this locating task is directly related with the travel of a second satellite within the coverage area of the first satellite and accordingly the locating time is related to the travel duration of the second satellite within the coverage area of the first satellite) of the second satellites. During clustering, the second satellites having minimum jamming signal carrier frequency detection time (in other words the time required for the second satellite to perform the scanning command and to find directly the carrier frequency of the jamming signal, this time is calculated by the related second satellite according to the position and coverage area information provided from the first satellite together with its own coverage area information and send to the first satellite within the second message) and jamming signal source locating time (in other words the time required for the second satellite to perform the scanning command and to find directly the carrier frequency of the jamming signal, this time is calculated by the related second satellite according to the position and coverage area information provided from the first satellite together with its own coverage area information and send to the first satellite within the second message) are determined and clustered with respect to the scoring values. Accordingly, clustered second satellites that can complete the locating as soon as possible are selected to perform locating command. Thanks to clustering the second satellites and selecting the sets of second satellites which are estimated as performing the locating command within the shortest time while meeting all other necessary parameters, location determination of the source of the detected jamming signal is able to be performed effectively, efficiently and quickly by optimising use of the second satellites.

[0118] In addition, since scanning command is sent to multiple second satellites, after receipt of found information following the scanning from a second satellite, before sending the locating command, the first satellite sends ending command to the other second satellites (19), which did not send the found information, to end the scanning task performing on those second satellites.

[0119] In another embodiment of the present invention, after finding the location of the interference source using positioning algorithms the method further comprises the step of transmitting a mission accomplished command from the first satellite to the second satellites to terminate the performing of the location command. Furthermore, the method further comprises recording all parameters related to the interference signal (carrier frequency, bandwidth, coverage, input power, and input flux density values, etc.) in a catalogue (20) of the first satellite for future use such that later, when a jamming signal with similar parameters is detected from the same coverage area, the parameters used in the selection of second satellites for sending scanning command and locating command can be quickly implemented. Furthermore, during scanning, at least one second satellite may need to terminate scanning (21 ) for any reason (for instance, the related second satellite may leave the coverage area, receive an urgent telecommand from an operator or a system failure may occur, etc.). For such a case, the method of the present invention comprises sending the remainder of the scanning mission from related second satellite to the first satellite with the mission parameters, assigning a new second satellite to perform the remaining of the scanning mission by the first satellite, following the assigning, transmitting, not the whole transponder channel bandwidth, but the incomplete task part of the scanning mission to the assigned second satellite in a first message. For example, if the second satellite has a 100 MHz bandwidth scanning task and it has to terminate its task after performing a 50 MHz scan, only the remaining 50 MHz bandwidth scanning is sent to the candidate second satellite. In this way, both the resources are used efficiently, and the continuity of the task is ensured.

[0120] Thanks to the method of the present invention, the location of a source of a jamming signal is able to be determined by aerially. Therefore, scanning of much more large terrestrial area is able to be performed by eliminating third country border problems. Accordingly, effectively and efficiently determination of the location is able to be provided in a quick manner by optimizing the use of the second satellites.

Claims

CLAIMS1. A method which is suitable for being used with a communication network comprising §at least one first satellite comprising at least one antenna, at least one receiver chain, at least one IMUX, at least one HPA chain, at least one OMUX and at least one control unit and,§at least one second satellite with at least one frequency filter, wherein the first satellite has certain computing capability to generate commands for the second satellite to perform certain tasks and wherein the first satellite is able to send / receive messages to / from second satellite over inter satellite links and wherein the method provides determination of the location of a source of a jamming signal coming to the first satellite characterized in that the method comprises the steps of:• detecting a jamming signal presence (1 ) on a transponder channel of the first satellite by the first satellite, from the power measurements of the signals received from the coverage areas of the first satellite and divided into channels by the IMUX of the first satellite;• determining, by the first satellite, the coverage area (2) from where the jamming signal is transmitted;• checking whether more than one transponder channel is affected (3) by the jamming signal and if there are more than one transponder channel that is affected by the detected jamming signal, prioritizing the jamming signals (4) with respect to the service types of the transponder channels;• sending to the second satellite, which is passing over and / or about to pass over the determined coverage area, a scanning command (5) in relation with the carrier frequency of the detected jamming signal from the first satellite;• after receipt of the scanning command, by the second satellite, configuring the receiver settings of the second satellite and starting the scanning task (6) to scan signals to lock its signal filter on the carrier frequency of the jamming signal;• when the carrier frequency and bandwidth of the jamming signal are found by the second satellite during performing scanning task, sending a found information from the second satellite to the first satellite (7) over ISL;• after receipt of found information, sending a locating command (8) including data of the jamming signal from first satellite to the second satellite;• after receipt of the locating command, configuring the receiver settings of the second satellite (9);• after configuration, by the second satellite, collecting sample data from the coverage area (10) with the locked filter of the second satellite and transmitting the collected data to the first satellite over ISL;• finding the location of the source of the jamming signal (11 ) by using positioning algorithms according to the collected data via control unit of the first satellite.

2. The method according to claim 1 wherein; first satellite is a GEO satellite.

3. The method according to claim 1 or claim 2 wherein; second satellite is a LEO satellite.

4. The method according to anyone of the preceding claims wherein; detecting a jamming signal presence (1 ) on a transponder channel step further comprises• separating signals received from the coverage area of the first satellite into narrowband transponder channels,• measuring power of each transponder channel and sending these measurements to the control unit,• comparing these measurements with a threshold level for each transponder channel by control unit,• detecting the presence of a jamming signal on the transponder channel if the threshold level of that transponder channel is exceeded.

5. The method according to claim 4 wherein; the threshold level is obtained by converting the permissible IFD limit in the control unit to the permissible power measured at the antenna interface, and then finding the limit value of the measured power in the transponder channel, with respect to the Equations 1 and 2 given below:Prx= PIFD + 10 log @ + Gant+ 30 (dBm) (1 ) wherein Prxis Satellite Input Power at antenna input inter face(dBm) , wherein PIFDis Input Power Flux Density (cLBW! m2) , wherein A is the Wavelenght(m) of the received signal with the related antenna, wherein Gantis Antenna Gain(dBi)P-TCN = Prx + Aten (2)wherein PTCis Nth Transponder Channel (TC) power at measurement point, wherein Aten is total gain between antenna input interface and TC power measurement point n.

6. The method according to any one of the preceding claims wherein; the prioritizing the jamming signals (4) step further comprises,• listing all interfering transponder channels with respect to service types and the number of served terminals,• ordering the list with respect to service types and maximum number of served terminals,• handling the jamming signals with respect to the ordered list.

7. The method according to anyone of the preceding claims wherein; before sending to the second satellite a scanning command (5), the method further comprises the step of selecting second satellites which will perform scanning command.

8. The method according to claim 7 wherein; the selecting second satellites comprises• generating a first message with respect to the scanning command (12) and containing information related to the transponder channel that the jamming signal is detected, related to the priority of the detected jamming signal and related to the first satellite, for each coverage area and transponder channel, by first satellite,• sending the first message from the first satellite to the second satellites (13) via ISL,• by receipt of the first message, generating a second message in response to the first message (14) by the second satellites and containing information related to the second satellites,• sending the second message from the second satellites to the first satellite (15),• by receipt of the second message, decoding and recording the content of the second message for evaluation in control unit,• by evaluating the second message content with respect to the predefined conditions via control unit, selecting the second satellites that are able to perform scanning command (16),• sending selecting information to the second satellites with scanning command.

9. The method according to claim 8 wherein; the first message comprises at least one entity of the entity set comprising transponder channel and related coverage areainformation on which the interfering has become, the bandwidth of that transponder channel (MHz), the center frequency of that transponder channel (MHz), input power of the repeater of the first satellite, input flux density of the first satellite, boundary of that coverage area (x, y, z) and the priority value that is assigned to that transponder channel.

10. The method according to claim 8 or claim 9 wherein; the second message comprises at least one of the below mentioned information:• available frequency scan bandwidth of the second satellite,• Two Lines Elements of the second satellite,• available resource,• available power,• properties of the antenna of the second satellite,• slew rate of the second satellite,• previously assigned scanning task information,• average time that is required to spent in the targeted coverage area.

11. The method according to claim 8 or claim 9 or claim 10 wherein; before selecting the second satellites, comparing information gathered from different second satellites by reception of the second message to each other via control unit of the first satellite by scoring these information highest value to lowest value from the best condition ensuring the best scanning to the worst condition and after scoring, clustering the second satellites, by the control unit, with respect to the scores and selecting the second satellites with respect to the scored clusters.

12. The method according to anyone of the preceding claims wherein; before sending to the second satellite a locating command, the method further comprises the step of selecting second satellites which will perform scanning command.

13. The method according to claim 12 wherein; the selecting second satellites comprises• generating a first message with respect to the locating command (17) and containing information related to the transponder channel that the jamming signal is detected, related to the priority of the detected jamming signal and related to the first satellite, for each coverage area and transponder channel, by first satellite,• sending the first message from the first satellite to the second satellites (13) via ISL,• by receipt of the first message, generating a second message in response to the first message by second satellites (14) and containing information related to the second satellites,• sending the second message from the second satellites to the first satellite (15),• by receipt of the second message, decoding and recording the content of the second message for evaluation in control unit,• by evaluating the second message content with respect to the predefined conditions via control unit, selecting the second satellites that are able to perform locating command (18),• sending selecting information to the second satellites with locating command.

14. The method according to claim 13 wherein; the first message comprises at least one entity of the entity set comprising transponder channel and related coverage area information on which the interfering has become, the bandwidth of that transponder channel (MHz), the center frequency of that transponder channel (MHz), input power of the repeater of the first satellite, input flux density of the first satellite, boundary of that coverage area (x, y, z) and the priority value that is assigned to that transponder channel.

15. The method according to claim 13 or claim 14 wherein; the second message comprises at least one of the below mentioned information:• available frequency scan bandwidth of the second satellite,• Two Lines Elements of the second satellite,• available resource,• available power,• properties of the antenna of the second satellite,• slew rate of the second satellite,• previously assigned locating task information,• average time that is required to spent in the targeted coverage area.

16. The method according to claim 13 or claim 14 or claim 15 wherein; before selecting the second satellites, comparing information gathered from different second satellites by reception of the second message to each other via control unit of the first satellite byscoring these information highest value to lowest value from the best condition ensuring the best scanning to the worst condition and after scoring, clustering the second satellites, by the control unit, with respect to the scores and selecting the second satellites with respect to the scored clusters.

17. The method according to anyone of the preceding claims wherein; after receipt of found information from a second satellite following the scanning, before sending the locating command, the first satellite sends ending command to the other second satellites (19), which did not send the found information, to end the scanning task performing on those second satellites.

18. The method according to anyone of the preceding claims wherein; after finding the location of the interference source using positioning algorithms the method further comprises the step of transmitting a mission accomplished command from the first satellite to the second satellites to terminate the performing of the location command.

19. The method according to anyone of the preceding claims wherein; the method further comprises recording all parameters related to the interference signal in a catalogue (20) of the first satellite for future use when a jamming signal with similar parameters is detected from the same coverage area.

20. The method according to anyone of the preceding claims wherein; during scanning, if at least one second satellite may need to terminate scanning (21 ), the method further comprises sending the remainder of the scanning mission from related second satellite to the first satellite with the mission parameters, assigning a new second satellite to perform the remaining of the scanning mission by the first satellite, following the assigning, transmitting the incomplete task part of the scanning mission to the assigned second satellite in a first message.

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