RU2395908C2 - Device of jamming countermeasures for mobile communication - Google Patents

Abstract

FIELD: information technologies.

SUBSTANCE: device for jamming countermeasures for system of cellular communication comprises user equipment (UE), at least one basic transceiving station in cellular network and is arranged with the possibility to generate pulse first signal (S1) with such period of pulses repetition and interval of repetition, so that the first pulse signal (S1) distorts the second pulse signal (S2), for the period of time, when control channel (S, F, B) in the second signal (S2) is sent in cellular network, besides the second signal (S2) is the signal of broadcasting channel sent from basic transceiving station for establishment of communication line between basic transceiving station and user equipment (UE).

EFFECT: increased efficiency of communication control.

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Description

ABBREVIATIONS

1G First Generation Wireless Mobile Network 2.5G GPRS and EDGE 2G Second Generation Wireless Mobile Network 3G Third Generation Wireless Mobile Network 4G Fourth Generation Wireless Mobile Network
(CDMA + IS-95) Amps Advanced Mobile Radiotelephone Service
(cellular) communications (1G) AMPS / D Digital Advanced Mobile Service
radiotelephone (cellular) communication (2G) BCCH Broadcast / Broadcast / Transmission Control Channel Bch GSM broadcast channels, i.e. FCCH, SCH and BCCH Bts Base Transceiver Station CCCH Common control channels CDMA Code Division Multiple Access (3G) CDMA2000, also known as multi-carrier IMT-CDMA or 1CH RTT (3G) DCCH Dedicated Control Channel EDGE (technology) data rate increase to promote
GSM evolution (2.5G) Facch Fast integrated control channel

FCCH Frequency (carrier) tuning channel Gprs General Packet Radio Service (for GSM and other cellular systems) (2.5G) GSM Global System for Mobile Communications (2G) IS-95 International Standard 95 (IS-95) is the first
CDMA-based digital cellular standard NMT Scandinavian mobile telephony (1G) Rbs Base station, network access point in radio communications
with the UE served by this network Sacch Low speed federated control channel SCH Sync channel SDCCH Standalone dedicated control channel Tch Traffic control channel TDMA Time Division Multiple Access UE User equipment, such as a cell phone UMTS Universal Mobile Telecommunications System (3G)

FIELD OF THE INVENTION

The invention relates to a method for a shielding device and a shielding device for a cellular communication system comprising user equipment of a UE in a cellular network.

BACKGROUND

In the field of mobile communication systems, it is known to use mobile phones (cell phones) and other devices using wireless means, hereinafter abbreviated UE for user equipment. The UE has an omnidirectional antenna sending signals in a spherical shape to a ground system. The ground system is built from a number of cells controlled by a number of base stations connected to grounded antennas covering each cell. Grounded antennas are usually not omnidirectional, but are limited by the azimuthal angle giving the horizontal sector and the elevation angle giving the vertical sector.

UEs communicate with that base station that has the best communication parameters at the moment. When the communication parameters change in the direction of deterioration, for example, when the UE moves away from the base station and moves to another cell, the UE moves from a weaker base station to an adjacent base station with better communication parameters.

Cellular networks are supported by the configuration of adjacent radio coverage cells. First-generation (1G) systems, such as NMT, AMPS, etc., and second-generation (2G) systems, such as GSM, use different frequencies to separate neighboring cells, while UMTS using CDMA uses logic coding to achieve cell separation 2G systems use TDMA to separate different users in a cell. The reason for using different frequencies and codes, respectively, is to minimize interference problems for UEs in neighboring cells.

However, the number of frequencies is limited, which is why the cellular configuration must be repeated in a larger area to use the same frequency a number of times.

There is currently no way to prevent a mobile phone from initiating access to any network to which it has been granted access, at the national / carrier level. If the home operator has a roaming agreement with an operator in another country, then the UE may then be able to interconnect anywhere within that operator’s radio coverage.

Even without this approval, all GSM UEs will be allowed to make emergency calls on any network within the scope, which is why some interaction will take place if measures are not taken.

There are some situations where a government, network operator, or others would like to prevent the UE from interacting with its own network or other networks, for example, in order to balance traffic loads; or “perforate” the cell and cause the UE to move to another cell, thereby moving the borders of the cell; or obstruct traffic for reasons of secrecy, for example, in prison or on an airplane, or in a library, etc. The signal may also be blocked in order to prevent interference in other competing networks, for example, for a client using another operator.

Therefore, there is a need for an improved control system that can control communication / traffic between the UE and the base station more efficiently.

SUMMARY OF THE INVENTION

The invention relates to a shielding device for a cellular communication system comprising UE user equipment in a cellular network. The invention is characterized in that the shielding device is configured to generate a pulsed first signal, adapted to shield the control channel in the second signal in the cellular network.

Here, the “screen” refers to the first signal transmitted in the same region where the second signal is transmitted, so that the first signal is superimposed on at least a portion of the second signal containing the control channel, which distorts the information in the control channel. If the information is distorted, then the UE cannot read this information and, therefore, cannot establish a connection.

Here, “fitting” refers to a shielding device to which information about the second signal in the form of duration, action, repetition interval and position of the control channel in the second signal is supplied, and from this information it calculates and generates a pulsed first signal with a corresponding pulse interval and repetition interval and acts in such a way that the pulsed first signal distorts the second signal for a period of time when the control channel is transmitted on the network.

One advantage of the invention is that it is only necessary to block part of the second signal in order to prevent the UE from establishing a connection to the network. Therefore, the shielding device should not be used continuously. On the contrary, the shielding device generates a first signal in the form of a single pulse with a given pulse interval and in a given repetition interval. The preset pulse interval and the preset repetition interval will be set so that the control channel is blocked. The shielding device, therefore, uses only part of the duration of the second signal. An advantage of the invention is thus found in a shielding device that consumes less energy and can, for the same use of energy, thus be used to a higher degree than a continuous shielding device by generating a number of different pulses to shield additional signals from the network .

Another advantage of the invention is that the pulsed first signal makes as little contribution to the total background noise as possible. It is desirable to keep this noise at the lowest possible level in order to obtain the greatest possible signal-to-noise ratio. This means that the network can transmit signals with less effect to overcome this noise so that the UE is able to distinguish this signal.

The second signal is generated by a base station, for example, a base transceiver station (hereinafter referred to as BTS). BTS manages a geographic area, often called a cell. In one type of system, both BTS and UE are transceivers, i.e. each of them is a device for two-way communication, operating both the sender and the receiver. However, the shielding device can also be used in a one-way communication system when the BTS is the sender and the UE is the receiver.

In a GSM-based communication system, the pulsed first signal has a first action in a first frequency used by the UE and the network. The first action in the first signal is adjusted to shield the control channel in the second signal.

In GSM, the frequency band is divided using the FDMA scheme into a number of carrier frequencies (also called frequency channels) with a frequency band of 25-30 kHz, separated from each other by a frequency band of 200 kHz, measured from the peak of the frequency band of 25-30 kHz. Each carrier frequency is then time sliced using a TDMA scheme. This circuit breaks the radio channel into 8 time slots. A time slot is a unit of time in a TDMA system and lasts approximately 0.577 ms. A TDMA frame is formed in 8 time slots and therefore lasts 4.616 ms. Each of the eight time slots that form the TDMA frame is then assigned to a single user for traffic. However, in GPRS, a user may receive a number of time slots in order to access an increased data rate. Each TDMA defines one time slot for a control channel in the form of a BCH and determines the remaining time slots for TCH traffic channels and control channels in the form of CCCH and / or DCCH. In order to interfere with traffic, only BCH needs to be distorted. The length of the BCH packet is also called the BCH packet. Three different types of BCH can be distinguished.

BCHs are used by the BTS (here, the transceiver) to provide the mobile station with the sufficient information it needs to synchronize with the network. The length of the BCH packet extends above 5 and 1/8 TDMA frames and is therefore 23.657 ms. The length of the BCH packet is also called the BCH packet. Three different types of BCH can be distinguished:

Broadcast Control Channel (BCCH), which gives the UE the parameters necessary for identification and access to the network.

A synchronization channel (SCH), which gives the UE the training sequence (s) needed to demodulate the information transmitted by the base station.

Frequency (Carrier) Adjustment Channel (FCCH), which supplies the UE with a system frequency reference to synchronize with the network.

In order to prevent GSM traffic, it is necessary to shield only the frequency channels transmitting any of the BCH.

In addition, it is theoretically necessary to shield only the frequency channels transmitting the BCH packet in order to prevent the receiving UE from initiating a network connection, due to the poor quality of the received signal. Theoretically, this can be achieved by a time-shielded device with a network, and where the first signal has a pulse interval of one time interval and a repetition interval identical to the length of the BCH packet.

Since the shielding device is not necessarily time synchronized with the network, the first signal must have a theoretically minimum pulse interval of 4.616 ms (eight time intervals) to provide shielding for one full or part of two BCH time intervals. With a BCH packet length of 23.657 ms, the shielding device must transmit periodically with a period of time not exceeding 23.5 ms to ensure that there is no risk that any BCH packet will go undamaged.

However, testing showed an optimal shielding effect when the pulse interval in the first signal is at least 7 ms with a maximum repetition interval of 23.5 ms.

Compared to continuously shielding the second signal by sending the first signal as a continuous signal interfering with the second signal in its entirety, this invention uses a 30% duty cycle compared to continuous shielding to shield GSM transmission.

The shielding device can use the pause of the duty cycle to shield additional frequency channels and thereby increase the shielding ability of the shielding device by approximately three times compared with continuous shielding. Another advantage is that the shielding device can use 70% of the additional action compared to continuous shielding or for the same action as the continuous signal is consuming 70% less energy and, thus, giving 70% of the additional service life battery operation. One additional advantage is that 70% energy savings make it possible to increase the output signal by a factor of three with the same service life as for a continuously operating shielding device.

Another advantage of the invention is that the source of the shielding device will also be more difficult to track and determine its location due to non-stationary signal transmission.

One effect of the invention is that the first signal shields the second signal so that the UE cannot establish a communication line and, therefore, cannot enter a specific frequency within the frequency band of the second signal.

Currently, 2G GSM frequencies are evenly distributed on the GSM-1800 and GSM-1900 bands. A honeycomb usually uses from two to 12 different frequencies.

The invention is not limited to a GSM-based system, but can be used in various systems using a second signal with a BCH packet (BCH packet length), a different number of time slots with different durations and a different number of control channels. The invention should then be adapted by changing the pulse interval and the pulse repetition interval in the first signal, respectively.

For example, a shielding device may be used in a CDMA (Code Division Multiple Access) system using codes to identify connections. The shielding device must be fitted here to form the first signal with a pulse length and repetition interval consistent with the corresponding control channel.

In a CDMA-based communication system, the first signal is adjusted to distort the pilot signal and may comprise a code. The pilot in a CDMA based system corresponds to a BCH packet in a TDMA based GSM system. However, in a CDMA-based system, the BCH packet may have a shape other than the above, and the control channel in such a signal is distorted by the pulse signal.

In one embodiment of the invention, the shielding device is configured to generate a pulsed first signal with the same pulse length or at least the same pulse length as the pulse length of the control channel, and with a repetition interval shorter than the BCH packet for the considered communication systems.

In another embodiment of the invention, the shielding device is configured to generate a pulsed first signal with the same pulse length or at least the same pulse length as the pulse length of the control channel, and with a repetition interval identical to the repetition interval of at least one control channel within the packet length of the broadcast channel.

In the latter two embodiments, the aforementioned advantages are supported.

The shielding device may be contained in the BTS transmitting the second signal. An advantage of this solution is that the communication between the UE and the BTS can be controlled by the shielding device without any changes being made to the second signal.

The shielding device may also be contained in a second BTS located at some distance from the BTS transmitting the second signal. An advantage of this solution is that the second signal may be distorted in a particular geographical area smaller than the working area of the BTS and the second signal without any changes to the UE, BTS or the second signal. This distortion controls the communication between the UE and the BTS as described above.

The shielding device may include a signal detection device that detects a second signal from the network. This information is used by the shielding device in determining the level and frequency of the first signal. However, the shielding device may not have a detection device, but may instead be programmed for certain events, i.e. the first signal has a signal level and frequency already set for various events. The shielding device may then be controlled to use various modes depending on the event in question. The shielding device can be controlled either manually or automatically.

The shielding device may be contained in a BTS also comprising a signal generator generating a third signal that is stronger than the first and second signals. The third signal is intended for use by the UE to establish a dedicated communication line.

The third signal has a predetermined effect in a predetermined frequency band upon leaving the BTS, so that the relationship between the third signal and the second signal corresponds to at least the minimum signal-to-noise ratio requirement received by the UE to establish a communication link.

The third signal may comprise information for controlling the UE. Examples of such information are the maximum transmission unit, which limits the output action of the UE, and the maximum time advance, giving the UE information about how large a given cell is.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described below in conjunction with a number of drawings, where:

FIG. 1 schematically shows a traffic pattern in a network comprising a shielding device according to the invention and a UE;

FIG. 2 schematically shows a transmission configuration of a BCH packet in a GSM based system, and where;

FIG. 3 schematically shows a second embodiment of the invention, where a first signal from an inventive shielding device is superimposed on a second signal, which is a GSM transmission according to FIG. 2.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 1 schematically shows a traffic pattern in a network comprising a shielding device 1 according to the invention and a UE. The shielding device 1 is contained in a second base transceiver station BTS2 together with a signal generator 2. The network also contains a second base transceiver station BTS2, designed to communicate with the UE within the cell.

The shielding device 1 generates and transmits a first signal S1 from BTS1. BTS2 generates and transmits a second signal S2, intended for receiving the UE, to establish a communication line. The signal generator 2 generates a third signal S3. The UE transmits the fourth signal S4 in non-directional form, intended for use to establish a communication link between the UE and the BTS2 through the third and fourth signals.

The first signal S1 is designed to shield the second signal S2 to such an extent that the UE cannot establish a communication line with BTS2. The third signal is identical to the second signal or different, but the third signal is stronger than the first and second signals. Since the third signal is stronger, the UE can establish a communication line with BTS1 through the third and fourth signals.

However, the invention relates mainly to a shielding device, and therefore, the shielding device could be used without a signal generator 2, i.e. without transmitting a third signal. In this embodiment, the UEs are prevented from establishing any communication at all.

Both BTS1 and BTS2 transmit signals by using a transmitting unit (not shown) and receive signals by using a receiving unit (not shown).

FIG. 2 schematically shows a transmission configuration 4 of a BCH packet in a second signal S2 in a GSM-based system. This transmission configuration should be read left to right and top to bottom line by line. In FIG. The 2 BCH packet is also shown as a sequence of time slots below the transmission configuration.

GSM is a TDMA method with multiple frequency channels. Each frequency channel is divided into a TDMA frame containing eight time slots assigned to control channels or traffic channels (TCH half or full speed). The control channels contain BCH and CCCH. Each time slot is 0.577 ms in length, and the length of the BCH packet is 5 and 1/8 TDMA frames and, therefore, 23.657 ms in length.

Each TDMA assigns one time slot to a control channel in the form of a BCH, CCCH (not shown) or DCCH (not shown) and defines seven time slots as TCH traffic channels. BCH channels are used by the BTS to provide the mobile station with enough information that it needs to synchronize with the network. The length of the BCH packet extends above 5 and 1/8 TDMA frames and is therefore 23.657 ms. The length of the BCH packet is also called the BCH packet. Three different types of BCH can be distinguished: BCCH, depicted by the letter B; SCH depicted by the letter S; and FCCH depicted by the letter F.

In order to interfere with GSM traffic, it is only necessary to shield the frequency channels transmitting any of the BCH.

FIG. 3 schematically shows a first signal from an inventive shielding device superimposed on a second signal, which is a GSM transmission according to FIG. 2. In FIG. 3, the synchronization channel S is shielded by the pulse first signal S1. With a BCH packet length of 23.657 ms, the shielding device periodically transmits a pulse with a pulse length of at least 7 ms and with a repetition interval not exceeding 23.5 ms. The first signal also has an effect that matches that of the second signal so that the signal-to-noise ratio becomes low enough so that the UE ignores information in the control channel. The features of the pulsed first signal impede the passage of the BCH packet intact.

Claims (4)

1. A jamming device (1) for a cellular communication system, comprising user equipment (UE) and at least one base transceiver station in a cellular network, characterized in that the jamming device (1) is configured to generate a pulsed first signal (S1) with a pulse repetition period and a repetition interval such that the pulse first signal (S1) distorts the second pulse signal (S2) during the time period when the control channel (S, F, B) in the second signal (S2) is transmitted to the cellular networks, reason m the second signal (S2) is a broadcast channel signal transmitted from the base transceiver station to establish a communication line between the base transceiver station and user equipment (UE), and the pulse repetition period of the pulse first signal (S1) has the same the length as the pulse repetition period of the control channel (S, F, B) in the second signal (S2), and the pulse repetition interval of the first signal (S1) is less than the packet length of the broadcast channel (3). 2. The jamming device according to claim 1, characterized in that the jamming device (1) is configured to generate a pulsed first signal (S1) with a pulse length of at least 7 ms and with a repetition interval of not more than 23 5 ms. 3. A method of jamming for a signal transmitted from a base transceiver station in a cellular communication system comprising user equipment (UE) and at least one base transceiver station in a cellular network, characterized in that the jamming device (1) generates a pulse a first signal (S1) with such a pulse repetition period and a repetition interval such that the pulse first signal (S1) distorts the second pulse signal (S2) during the time period when the control channel (S, F, B) in the second signal (S2) is transmitted network, and the second signal (S2) is a broadcast channel signal transmitted from the base transceiver station to establish a communication line between the base transceiver station and user equipment (UE), while the pulse repetition period of the pulse first signal (S1) has the same the length as the pulse repetition period of the control channel (S, F, B) in the second signal (S2), and the pulse repetition interval of the first signal (S1) is less than the packet length of the broadcast channel (3). 4. The method according to claim 3, characterized in that the jamming device (1) generates a pulsed first signal (S1) with a pulse length of at least 7 ms and with a repetition interval of not more than 23.5 ms.

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