RU2384974C1 - Base transceiver station on-board aircraft for mobile communication - Google Patents

Abstract

FIELD: physics, communications.

SUBSTANCE: invention relates to a base station (BTS) for a cellular communication system which has user equipment on board an aircraft at a predefined altitude, and a ground-based network. The BTS is made as an on-board BTS which has a screening device which generates a first signal (S1) matched for screening a second signal (S2) from the ground-based network at a predefined altitude. The on-board BTS also has a signal generator which generates a third signal (S3) which is more powerful than the first signal (S1) and the second signal (S2), and can set up a communication line with user equipment through the third signal (S3).

EFFECT: no problems arise or minimal problems of cross-talk in the ground-based network arise when controlling connection/traffic towards user equipment and from the user equipment to the aircraft.

16 cl, 6 dwg

Description

Abbreviations

1G First Generation Wireless Mobile Network

2.5G GPRS and EDGE Systems

2G Second Generation Wireless Mobile Network

3G Third Generation Wireless Mobile Network

4G Fourth Generation Wireless Mobile Network

AMPS Advanced Mobile Telephony Service (1G)

AMPS / D Digital Advanced Mobile Telephony Service (2G)

BCCH Broadcast control channel, one of three BCH channels

BCH Broadcast channels of the GSM system, i.e. FCCH, SCH and BCCH

BSC Base Station Controller

BTS Base Transceiver Station

CCCH Common Control Channels

CDMA Code Division Multiple Access

CDMA2000, or IMT-CDMA with multiple carriers or 1xRTT (3G)

DCCH Dedicated Control Channel

EDGE The development of the GSM standard with increased data rate (2.5 G)

FACCH Quick Link Control Channel

FCCH Frequency Correction Channel

GPRS General Packet Radio Service / GSM (2.5G)

GSM Global System for Mobile Communications (2G)

IS-95 Intermediate Standard 95 (IS-95), the first CDMA-based digital cellular standard

NMT Scandinavian Mobile Telephony (1G)

RBS Base station, network access point in radio communication with user equipment (UE) served by the network

SACCH Slow Link 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 Communications System (3G)

FIELD OF THE INVENTION

The invention relates to a base station (BTS) and a method for a BTS for a cellular communication system comprising user equipment (UE) on board an aircraft at a predetermined height and a ground network.

State of the art

In the field of mobile communication systems, as you know, they use mobile phones (cell phones) and other devices that use wireless communications, hereinafter referred to as user equipment (UE). The user equipment (UE) has an omnidirectional antenna sending signals to the terrestrial network with a spherical radiation pattern. A terrestrial network is constructed of several cells controlled by several base stations connected to terrestrial antennas spanning each cell. Terrestrial antennas are usually not omnidirectional, but are limited by the azimuth angle giving the horizontal sector and the elevation angle giving the vertical sector.

The user equipment (UE) interacts with the base station that currently has the best communication parameters. When communication parameters deteriorate, for example, when a user equipment (UE) moves away from the base station and moves to another cell, the user equipment (UE) moves from a weaker base station to an adjacent base station with better communication parameters.

Cellular networks are supported by adjacent cell layouts for radio coverage. 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 the UMTS system uses logical coding to achieve cell separation. The reason for using different frequencies and codes, respectively, is to minimize interference problems for a user equipment (UE) in neighboring cells.

However, the number of frequencies is limited, therefore, the arrangement of cells must be repeated in a larger area for using the same frequency several times.

When using a user equipment (UE) on board an aircraft, a problem arises when the aircraft is at a distance from the ground, because the line of sight from above is so wide that the signal from the user equipment (UE) comes into contact / interacts with several cells using one and same frequency. For example, if a person on board an aircraft at an altitude of more than 3,000 m turns on his cell phone, then the omnidirectional antenna will send at least in the direction of view and, thus, finally make contact / interact with several different cells using the same same frequency or code. This causes the aforementioned interference problem for multiple instances of a user equipment (UE) in a terrestrial network, and therefore may affect the frequency / time slot combinations used for voice transmission over a large area of the network, also over long distances outside the normal cell radius of a GSM system. In addition, using or blocking the same frequency in several different cells to perform the same task is an unnecessary waste of resources. Additional problems arise if busy cells belong to different network administrators. Similar problems arise if the passenger forgot to turn off the cell phone. Then the cell phone interacts with many cells to announce its position and enter roaming with new network operators.

Today, there is no way to prevent a mobile phone from initiating access to any network in which it was previously granted access (at the national / operator level). If your own operator has a roaming agreement with an operator in another country, the user equipment (UE) can communicate anywhere within the radio coverage of that operator’s network.

Even without such an agreement, all instances of the user equipment (UE) of the GSM system will be allowed to make emergency calls on any network within the scope, therefore, if measures are not taken, some interactions will take place.

There are also situations where the government, network operator, etc. wants to prevent user equipment (UE) from interacting with networks other than a dedicated access point or access points.

Therefore, a better communication system is desirable that can control communication / traffic towards and from the user equipment (UE) in the aircraft without causing problems or creating minimal interference problems in the terrestrial network.

Disclosure of invention

The invention relates to a base station (hereinafter referred to as a base transceiver station (BTS)) for a cellular communication system comprising user equipment (hereinafter referred to as user equipment (UE)) on board an aircraft at a predetermined height and a ground network. The invention is characterized in that the base transceiver station (BTS) is designed as a BTS on board an aircraft, comprising a shielding device forming a first signal matched to shield the second signal from the ground network at a predetermined height. The on-board BTS also contains a signal generator that generates a third signal that is stronger than the first signal and / or second signal. The on-board BTS is configured to establish a communication link with a user equipment (UE) through a third signal.

In the first embodiment, “consistent” is a first signal having a first level in a first frequency range, matched to shield a second signal having a second level in a second frequency range. The first frequency range is equal to or greater than the second frequency range.

In one embodiment, the third signal has a third level, and the third frequency range is at least partially or completely within the first frequency range of the first signal.

A communication link is established because the third level of the third signal is larger than the first level, and / or since the third level is larger than the second level.

The invention also relates to a method for a communication system.

One effect of the invention is that the first signal shields the second signal so that the user equipment (UE) cannot establish a communication line directly with the terrestrial network. Therefore, the user equipment (UE) cannot tune to a certain frequency within the frequency range of the second signal. This is an advantage because the use of user equipment (UE) on board the aircraft will not interfere with the ground network by coming into contact with several cells operating on the basis of the same frequency or the same coding. However, if the user equipment (UE) can track a suitable cell, the user equipment (UE) will tune to the frequency used in the cell. Therefore, the initial match is not a prerequisite for mutual interference.

Therefore, without the communication system in accordance with the invention, all traffic would be transmitted to terrestrial networks and, as a result, with great mutual interference for all terrestrial user equipment (UE). Thus, the on-board BTS in accordance with the invention provides a good tool for local control of traffic channels without interacting with all networks in a potentially affected terrestrial area.

Another advantage is that neither the terrestrial network nor the on-board user equipment (UE) need to be changed to avoid the problem mentioned above. Therefore, the fourth signal is a conventional signal generated in a user equipment (UE).

The invention in accordance with the first embodiment can be used in all existing terrestrial networks, such as AMPS / D-AMPS, GSM, cdma / CDMA2000 and UMTS, that is, in all existing systems of generations 1G, 2G, 3G, 3,5, and possibly , also in future 4G generation systems. All frequency channels in these ranges are shielded to force the user equipment (UE) to move to a dedicated range with allowed access channels supported by the onboard BTS. The highlighted range may be a narrow range within the shielded range or another range.

The airborne BTS may include a signal detection device that detects a second signal from a terrestrial network. The information is used by the on-board device to determine the signal strength and frequency of the first signal. However, the onboard BTS may not have a detection device, but instead it can be programmed for some events, that is, the first signal has a signal strength and frequency already set for different events. Then the on-board BTS can be controlled to use various modes depending on the available case. The onboard BTS can be controlled either manually or automatically.

The third signal has a predetermined level in a predetermined frequency range at the output of the on-board BTS so that the ratio between the third signal and the second signal and / or the third signal and the first signal meets at least the minimum requirement for the signal to noise ratio (s / n), used by user equipment (UE) to establish a communication line.

In one embodiment, the first signal spans the entire frequency spectrum used by the terrestrial network. This can be implemented in such a way that the onboard BTS sends the first signal in the form of a pulse signal with a repetition interval that is short enough to generate several pulses for all frequency channels within the same time interval. The accumulated pulses within one time interval have sufficient energy to shield the second signal so that the signal-to-noise ratio becomes too low to establish a communication line. However, the shielding device may send a continuous signal spanning all frequency channels used by the terrestrial system.

The invention is intended to be used during the following scenario. When the aircraft is on the ground and ready to take off, all passengers are asked to turn off their communication devices, that is, user equipment, such as mobile phones and computers containing communication equipment. When the aircraft is at a certain height, the shielding device turns on, and passengers on board are allowed to turn on their user equipment (UE). When the user equipment (UE) is turned on, the shielding device has already generated a first signal that shields all signals (the second signal) from the terrestrial network, thereby preventing the user equipment (UE) from receiving the terrestrial second signal necessary for realizing / initializing direct communication with the terrestrial network. The signal generator generates a third signal, which is stronger than the first signal (and / or second signal), and is located at a certain frequency or frequencies. The user equipment (UE) searches for a signal with an acceptable signal-to-noise ratio and tunes to a third signal. The airborne base transceiver station (BTS) thus creates an airborne cell in which user equipment (UE) can be used. The system is preferably installed so that the crew of the aircraft can start the shielding device without an active onboard signal generator of the base transceiver station (BTS). This makes it possible to block the interaction of all user equipment (UE). The signal generator can then be independently turned on and off when traffic should be allowed or denied accordingly.

The on-board BTS is preferably connected to the on-board antenna in the form of a radiating cable extending in the longitudinal direction of the aircraft and close to a passenger using user equipment (UE). This short distance between the user equipment (UE) and the antenna makes it possible to keep the power of the first and third signals to a minimum.

The on-board BTS is connected to a satellite communications line that processes traffic between the aircraft and dedicated base stations in the ground network. The on-board BTS thus serves as the transmission link for traffic between the terrestrial network and the user equipment (UE) through the satellite link. The satellite communication line contains an onboard satellite antenna that sends signals to a satellite located at a higher level than the aircraft. The satellite interacts with a dedicated base station. A satellite link may contain a modem between the onboard BTS and the satellite. The relationship between the onboard BTS

and the modem can be based on the A-bis interface (the interface between the base station controller (BSC) and the base transceiver station (BTS) in the GSM system) or on the IP protocol (Internet protocol). The satellite communication line can be replaced by a communication line between the onboard antenna directed towards the ground and interacting with a dedicated base station or base stations.

The following are two examples of how the invention can be used in a terrestrial network based on a GSM system. The examples should not be construed as limiting the invention, but are intended only to further clarify the invention.

First example

GSM frequencies are evenly distributed across the ranges of GSM 900, GSM 1800 and GSM 1900. A cell typically uses from 2 to 12 different frequencies.

When the aircraft is at an altitude of 3000 m, the second signal loses approximately 107 dB due to propagation in air and 10 dB due to the penetration of the signal through the wall of the aircraft. Additional losses are caused by the vertical antenna gain of the ground base transceiver station (BTS). In an aircraft, the power of the received second signal from the ground network decreases by approximately 95 dB after the losses mentioned above. The power of the first signal is set 15 dB more than the power of the received ground second signal, and another 15 dB is added to the power of the third signal, that is, with an interval of approximately 30 dB from the second signal.

The shielding device generates a first signal containing all the necessary frequencies and having a level of approximately 3 dBm for every 200 kHz when entering the antenna system. The third signal can have an initial level of up to 35 W / 45 dBm when entering the antenna system connected to the onboard BTS. For the case with an interval of 15 dB from the first signal, an initial level of 18 dBm at the entrance to the antenna system is sufficient.

The user equipment (UE) has a threshold for a signal to noise ratio (s / n) of at least 7 dB in order to establish a communication line with an onboard BTS. In the case where the first signal has a level of approximately 3 dBm, and at a selected power with an additional 15 dB compared to the first signal, the third signal has a level of at least 18 dBm. The level depends on the frequency and bandwidth.

However, if the power level of the second signal is precisely known, and since the signal-to-noise ratio (s / n) must be 7 dB for the user equipment (UE) for receiving the signal, the first signal may have a power that is less than the power of the second signal, namely not more than 7 dB below the power of the second signal, for example, 6.5 dB below the power of the second signal. Then the third signal should add at least 7 dB to the second signal in the aircraft.

Therefore, the levels from 0 to 12 dBm at the entrance to the antenna turned out to be suitable levels of the first signal, depending on the type of aircraft design because the larger the aircraft, the longer the antenna and the greater the loss.

The user equipment (UE) cannot transmit a signal below 0 dBm, since this level is the starting point for a received signal in the terrestrial network from the user equipment (UE).

Second example

The example considers the worst case estimate of the level of interference in an airborne base transceiver station (BTS) and a terrestrial system using the GSM 1800 system and isotropic antennas.

Terrestrial BTS typically transmits at a level of 30 dBm (1 W) to 60 dBm in the horizontal plane. The resulting energy level at a distance of 3 km was measured and amounted to -85 dBm. The aircraft body adds another 10 dB of shielding, resulting in a -95 dBm signal from the ground-based BTS in the cabin.

The shielding device will be able to exceed this level by approximately 15 dB, that is, the user equipment (UE) on board will receive a level of -80 dBm of the first signal. The required level of the first signal supplied to the emitting cable from the onboard BTS to each frequency channel is calculated by compensating for losses in matching with the antenna (73 dB for one antenna) and alternating antenna cable (4 dB), resulting in -3 dBm. This worst case level is reduced by 10 dB due to shielding of the enclosure and losses during propagation in free space to the surface of the earth (107 dB) and as a result gives an effect of -120 dBm on the terrestrial network from the shielding device.

The on-board BTS will transmit a third signal at a level that is received by a user equipment (UE) with a level that is 15 dB above the first signal, i.e., -65 dBm. By analogy with the calculation of the effect on the earth’s surface from the shielding device given above, the effect on the earth’s surface from the third signal is -105 dBm.

In order to prevent user equipment (UE) from initiating calls with a maximum user equipment (UE) signal level, i.e., +30 dBm, the on-board BTS will be able to limit the user equipment (UE) to its minimum signal level, i.e., 0 dBm. This configuration is performed in a base station controller (BSC) in a ground system and is supplied to a user equipment (UE) in a third signal. The base station controller (BSC) communicates with the airborne BTS via a dedicated route, for example, via a satellite link. A base station controller (BSC) can be placed at any location suitable for controlling one or more airborne BTSs. Reception on the surface of the earth will be approximately 0 dBm (at the output of user equipment (UE)) - 10 dB (aircraft body) -107 dB (transmission loss at a distance of more than 3000 m) = -117 dBm. The negative antenna gain of the terrestrial BTS should be subtracted from this. The impact from the third signal is usually so weak that it sinks in the background noise at the ground level.

The conclusion from this calculation is that the interference between the ground and airborne networks is negligible, while the shielding device prevents the user equipment (UE) from directly accessing the ground network.

From the above, the overall level required by the shielding device and the signal generator can also be inferred. First, the loss in components near the antenna (6 dB) should be taken into account. The resulting output powers of the shielding device (first signal) and signal generator (third signal) are 3 dBm and 18 dBm per frequency channel, respectively. The shielding device will transmit on all (124 + 375) 499 frequency channels of the GSM 900 and GSM 1800 GSM ranges, adding (10 × Log499) 27.0 dB, which leads to 30 dBm for the total output power of the shielding device for the first signal. In one example, the on-board BTS signal generator will only transmit on three or less frequency channels (4.8 dB), resulting in an output power of 22.8 dBm on-board BTS for the third signal. However, the signal generator can generate a third signal containing more than three frequency channels, and then the output power of the BTS should be increased accordingly.

The parameters mentioned above are different for different aircraft, different ground systems, different heights, etc., therefore, the on-board BTS of the invention must be adapted accordingly.

In one embodiment of the invention, the first signal does not cover the entire frequency range corresponding to the second signal, but only part of the frequency range.

In a second embodiment of the invention, the shielding device is configured to generate a pulsed first signal matched for shielding the control channel in the second signal in the cellular network.

Here, “shielding” refers to the first signal transmitted in the same region where the second signal is transmitted, so that the first signal overlaps at least that part of the second signal that contains the control channel, thereby violating information in the control channel. If the information is violated, the user equipment (UE) cannot read the information and therefore cannot establish communication.

Here, “matching” refers to a shielding device to which information is provided regarding the second signal in the form of the duration, level, repetition interval and position of the control channel in the second signal, and which, based on this information, calculates and generates a pulsed first signal with a suitable pulse interval and repetition interval and level so that the pulsed first signal interferes with the second signal during the period of time when the control channel is transmitted in the network.

One effect of the embodiment is that only part of the second signal should be blocked to prevent the user equipment (UE) from communicating with the network. Therefore, the shielding device should not be used continuously. On the contrary, the shielding device generates the first signal in the form of a single pulse with a predetermined pulse interval and in a predetermined repetition interval. The predetermined pulse interval and the predetermined repetition interval must be set so that the control channel is blocked. Thus, the shielding device uses only a fraction of the duration of the second signal. Thus, the effect of this embodiment is that the shielding device consumes less power and can be used more efficiently with the same power use than the continuous shielding device by generating several different pulses to shield additional signals from the network.

In a communication system based on a GSM system, the pulsed first signal has a first level in a first frequency band used by a user equipment (UE) and a network. The first level in the first signal is matched to shield the control channel in the second signal.

In the GSM system, the frequency range is divided using the FDMA scheme into several carrier frequencies with a bandwidth of 25-30 kHz, separated from each other by a band of 200 kHz, measured from the top of the 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. The time interval is a unit of time in the TDMA scheme and lasts approximately 0.577 ms. A TDMA frame is constituted by 8 time slots and therefore lasts 4.616 ms. Each of the eight time slots that form the TDMA frame is then assigned to one user. However, in a GPRS system, a user may receive several time slots for access with an increased data rate. Each TDMA system assigns one time slot to a control channel as a BCH and assigns the remaining time slots to traffic TCHs and control channels as CCCH and / or DCCH. To prevent traffic, only the BCH channel must be violated. The pulse length of the BCH channel is also called the BCH channel packet. Three different types of BCH channels can be distinguished.

BCHs are used by the BTS (here, the transceiver) to provide the user equipment (UE) with enough information that is needed to synchronize with the network. The BCH pulse length is 5 and 1/8 of the TDMA frame and, therefore, is 23.657 ms. The pulse length of the BCH channel is also called the BCH channel packet. Three different types of BCH channels can be distinguished:

- Broadcast control channel (BCCH), which gives the user equipment (UE) the parameters necessary to identify the network and gain access to it;

- A synchronization channel (SCH), which gives the user equipment (UE) the training sequence necessary to demodulate the information transmitted by the base station;

- Channel frequency correction (FCCH), which provides the user equipment (UE) the reference frequency of the system for its synchronization with the network.

To prevent GSM system traffic, you only need to shield the frequency channels that transmit any of the BCH channels.

In addition, theoretically, only frequency channels transmitting a BCH packet should be shielded to prevent the receiving user equipment (UE) from initiating a network connection due to poor received signal quality. Theoretically, this can be achieved by a time-synchronized shielding device in which the first signal has a pulse interval equal to one time interval and a repetition interval that is identical to the pulse length of the BCH channel.

However, since the shielding device is not necessarily time synchronized with the network, the first signal needs a theoretical minimum impulse interval of 4.616 ms (eight time intervals) to provide shielding for one full or part of two time intervals of the BCH channel. With a BCH channel pulse length of 23.657 ms, the shielding device should periodically transmit with a period time not exceeding 23.5 ms to ensure there is no risk that any packet of the BCH channel will be unaffected.

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

The shielding device can use the dwell time of the duty cycle to shield additional frequency channels and, thereby, increase the shielding capabilities of the shielding device with a factor of approximately three compared to continuous shielding. An additional advantage is that the shielding device can provide 70% of the additional effect compared to continuous shielding or, with the same effect as the continuous signal, use 70% less power, and thus provide 70% of the additional useful life when working on battery power. One additional advantage is that 70% power saving makes it possible to increase the output signal by a factor of three with the same useful life compared to a continuously operating shielding device.

Another advantage of the embodiment is that the source of the shielding device will also be more difficult to track and locate due to intermittent signal transmission.

As a result, in accordance with the first embodiment, it is possible to continuously shield the second signal by sending the first signal as a continuous signal, interfering with the second signal completely, or in accordance with the second embodiment, using a pulsed first signal with all the above advantages.

One effect of the invention is that the first signal shields the second signal so that the user equipment (UE) cannot establish a communication line and therefore cannot tune to a certain frequency within the frequency range of the second signal.

Currently, the frequencies of the 2G generation GSM system are evenly distributed over the GSM-1800 and GSM-1900 ranges. A honeycomb usually uses from 2 to 12 different frequencies.

The invention is not limited to systems based on the GSM system, but can be used in various systems using a second signal with a BCH channel packet (BCH channel pulse length) for a different number of time intervals with different durations and different numbers of control channels. Then the invention must be adapted by correspondingly changing the pulse interval and the pulse repetition interval in the first signal.

For example, a shielding device may be used in a code division multiple access (CDMA) system using codes to identify connections. In this case, the shielding device must be matched to form the first signal with the pulse duration and repetition interval according to the corresponding control channel.

In a CDMA-based communication system, the first signal is negotiated for pilot violation and may contain a code. A pilot in a CDMA based system corresponds to a BCH channel packet in a TDMA based GSM system. However, in a CDMA-based system, the BCH packet may look different from that described above, and the control channel in such a signal is violated by a pulse signal.

In one embodiment of the invention, the shielding device is configured to generate a pulsed first signal with the same or at least the same pulse width as the pulse width of the control channel, and with a repetition interval less than that of the BCH channel packet for the communication system in question.

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

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

In a further embodiment of the invention, the shielding device may be contained in a base transceiver station (BTS) transmitting a second signal, that is, in a terrestrial network. The advantage of this solution is that the shielding device can control the communication between the user equipment (UE) and the BTS without any changes in the second signal.

In yet another embodiment, the shielding device comprises a detection device that detects and analyzes a second signal. The on-board BTS uses the information to match the first signal to screen the second signal and configure the third signal so that the user equipment (UE) can distinguish the third signal from the first and second signals.

The third signal may comprise information for managing user equipment (UE). Examples of such information are the maximum exchange unit, which limits the output level of the user equipment (UE), and the maximum lead (TA), which gives the user equipment (UE) information regarding how large the cell is logically.

Brief Description of the Drawings

The invention will now be described in conjunction with the drawings, in which:

FIG. 1 schematically shows an airborne BTS according to the invention on board an aircraft at an altitude from which a portion of the ground network is viewed;

FIG. 2 schematically shows a traffic pattern in a network comprising an airborne BTS and user equipment (UE) in accordance with FIG. one;

FIG. 3 schematically shows a signal to noise ratio between two cells;

FIG. 4 schematically shows a power versus frequency diagram in accordance with a first embodiment of the invention;

FIG. 5 schematically shows a BCH channel transmission pattern in a GSM-based system; and

FIG. 6 schematically shows a second embodiment of the invention, in which the first signal from the shielding device in accordance with the invention is superimposed on the second signal, which is the transmission of the GSM system in accordance with FIG. 5.

The implementation of the invention

FIG. 1 schematically illustrates a base station (BTS) in accordance with the invention, located aboard aircraft 1 at an altitude from which a portion of a ground network comprising cells C1, C2, C3, C4, C5, C6 and C7 with a repeating arrangement is viewed. The distribution of frequencies among cells is such that adjacent cells do not use the same frequencies to minimize interference from other cells using the same frequency. The onboard BTS includes a shielding device 2 and a signal generator 3. The on-board BTS is connected to a satellite link containing a satellite dish 4, satellite 5 and a dedicated base station 6 in the terrestrial network. On board the aircraft 1 is a user equipment (UE) comprising an omnidirectional antenna. In FIG. 1, a survey line for a user equipment (UE) is shown as a cone 7. A user equipment (UE) can potentially communicate with all cells C1-C7 within the cone 7.

FIG. 2 schematically shows a traffic pattern in a network comprising an airborne BTS and user equipment (UE) in accordance with FIG. one.

The on-board BTS includes a shielding device 2 that generates a first signal S1, and a signal generator 3 that generates a third signal S3. The ground network transmits a second signal S2, which the user equipment (UE) can receive. The user equipment (UE) also transmits the fourth signal S4 with an omnidirectional radiation pattern. However, the fourth signal is not strong enough to communicate with the terrestrial network, but communication is established between the airborne BTS and the user equipment (UE) through the third signal S3 and the fourth signal S4. The on-board BTS also transmits the fifth S5 signal, designed to communicate with the terrestrial network. The onboard BTS also receives the sixth S6 signal from the terrestrial network. The fifth and sixth signals form the communication line between the airborne BTS and the dedicated terrestrial BTS and, ultimately, the communication line between the user equipment (UE) and the terrestrial communication system.

The BTS transmits signals using a transmitting element (not shown) and receives signals using a receiving element (not shown).

FIG. 3 schematically shows a signal to noise ratio (s / n) diagram between two cells controlled by two terrestrially coupled BTSs.

The ground network is configured to process some signal to noise ratio (s / n). If two adjacent cells of the GSM system used the same frequency, there would be a deadband region in which both cells would have a signal to noise ratio (s / n) that was too low for operation.

In addition, FIG. 3 shows that the signal power decreases in space since the signal-to-noise ratio (s / n) decreases with distance. This is used in the invention because in order to establish a connection, a user equipment (UE) must receive a signal with a signal to noise ratio (s / n) that is above a predetermined threshold. The shielding device in the on-board BTS generates a first signal that increases the noise so that the signal-to-noise ratio (s / n) falls below a threshold. Since the second signal from the terrestrial network was attenuated on the way to the aircraft, the shielding device should only generate a correspondingly weak first signal to reduce the signal-to-noise ratio (s / n) below the threshold. A weak first signal S1 does not interfere with the terrestrial network, since its power decreases along the path from the aircraft 1 to the surface of the earth so that when it reaches the base stations in the terrestrial network, the first signal S1 does not add much noise or does not add any noise to signals near the surface of the earth.

FIG. 4 schematically shows a diagram of power versus frequency in accordance with the present invention for signals in an aircraft. FIG. 4 shows that the second signal S2 coming from the terrestrial network contains three frequency ranges S2F1-S2F3. The shielding device 2 in the onboard BTS generates a first signal S1 containing three frequency bands S1F1-S1F3 corresponding to the three frequency bands S2F1-S2F3 in the second signal S2, and thus shields the second signal S2.

FIG. 4 also shows that the signal generator 3 generates a third signal S3 comprising three frequencies S3F1-S3F3 within one of the three frequency ranges S1F1-S1F3. The third signal S3 is stronger than the first and second signals S1, S2, and thereby forms a signal to noise ratio (s / n) above a threshold. The second signal S2 has weakened on its way from the surface of the earth to the aircraft. The third signal S3 should only be strong enough to give a signal-to-noise ratio (s / n) above the threshold in the aircraft, and should not be as strong as the second signal S2 at the surface of the earth. Therefore, the third signal S3 does not interfere with the terrestrial network, since its power decreases along the path from the aircraft to the surface of the earth so that when it reaches the base stations in the terrestrial network, the third signal does not add a lot of noise or does not add any noise to the signals near from the surface of the earth.

Thus, the signal traffic becomes directed to a dedicated access point in the aircraft so that interaction with any other network is prevented.

FIG. 5 schematically shows a transmission pattern of packets 8 of a BCH in a GSM-based system. The transfer pattern should read from left to right and from top to bottom in rows. In FIG. 5, a BCH packet 8 is also shown as a sequence of time slots below a transmission pattern.

The GSM system is a TDMA technique 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 channel with half transmission rate or full transmission rate). The control channels contain BCH, CCCH, and DCCH, but interference should only be created for the BCH. Each time slot lasts 0.577 ms, and the packet length of the 8 BCH channel is 5 and 1/8 of the TDMA frame and, therefore, is 23.657 ms.

Each cell of the TDMA system assigns one time slot to a control channel as a BCH and assigns seven time slots as TCH traffic channels. BCHs are used by the BTS to provide the user equipment (UE) with sufficient information that it needs to synchronize with the network. The pulse length of the BCH channel extends to 5 and 1/8 TDMA frames and, therefore, is 23.657 ms. The pulse length of the BCH channel is also called the BCH channel packet. Three different types of BCH channels can be distinguished: BCCH, denoted by the letter B; the SCH channel indicated by the letter S and the FCCH channel indicated by the letter F.

To prevent GSM system traffic, you only need to shield the frequency channels that transmit any of the BCH channels.

FIG. 6 schematically shows a first signal S1 from a shielding device in accordance with the invention superimposed on a second signal S2, which is a GSM system transmission in accordance with FIG. 5. In FIG. 6, the synchronization channel S is shielded by the pulse first signal S1. When the pulse length of the packet 8 of the BCH channel is 23.657 ms, the shielding device 2 periodically transmit a pulse with a pulse duration of at least 7 ms and with a repetition interval not exceeding 23.5 ms. The first signal S1 also has a level corresponding to the level of the second signal, so the signal-to-noise ratio becomes low enough for the user equipment (UE) to ignore the information in the control channel. Signs of a pulsed first signal S1 prevent any packet 8 of the BCH from being touched.

In this embodiment, the third signal S3 is generated in accordance with the embodiment described in connection with FIG. 4. The third signal is stronger than the first signal S1 and the second signal S2, and thus is selected by the user equipment (UE) when trying to establish a communication line.

Claims (16)

1. Base transceiver station (BTS) for a cellular communication system containing user equipment (UE) on board an aircraft (1) at a predetermined height and a terrestrial network, characterized in that the base transceiver station (BTS) is designed as a base transceiver a station (BTS) on board the aircraft, comprising a shielding device (2) configured to generate a first signal (S1) matched to shield the second signal (S2) from the ground network at a predetermined height, b the onboard transceiver station (BTS) also comprises a signal generator (3) configured to generate a third signal (S3) that is stronger than the first signal (S1) and / or than the second signal (S2), the onboard base transceiver station ( BTS) is configured to establish a communication link with a user equipment (UE) by a third signal (S3). 2. The base transceiver station (BTS) according to claim 1, characterized in that the third signal (S3) has a third frequency range that is at least partially or completely within the first frequency range (S1F2) of the first signal (S1). 3. The base transceiver station (BTS) according to claim 2, characterized in that the first frequency range (S1F1) is equal to or greater than the second frequency range (S2F2) of the second signal (S2). 4. The base transceiver station (BTS) according to claim 1, characterized in that the first signal (S1) has a first level agreed to screen a second signal (S2) having a second level, the third signal (S3) having a third level, which is more than the first level and / or second level. 5. The base transceiver station (BTS) according to claim 1, characterized in that the shielding device (2) is configured to generate a first signal (S1) in the form of a pulsed first signal (S1), matched for shielding the control channel (F; S; B) in the second signal (S2). 6. The base transceiver station (BTS) according to claim 5, characterized in that the shielding device (2) is configured to generate a pulsed first signal (S1) with the same or at least the same pulse width as the pulse width of the control channel ( F; S; B), and with a repetition interval that is less than the pulse length (8) of the broadcast channel. 7. A base transceiver station (BTS) according to any one of claims 5 or 6 for a GSM cellular communication system, characterized in that the shielding device (2) is configured to generate a pulsed first signal (S1) with a pulse duration of at least 7 ms and with a repetition interval not exceeding 23.5 ms. 8. The base transceiver station (BTS) according to claim 1, characterized in that the airborne transceiver station (BTS) is connected to the airborne antenna. 9. The base transceiver station (BTS) according to claim 8, characterized in that the on-board antenna is made in the form of a radiating cable extending in the longitudinal direction of the aircraft and located close to the passenger using user equipment (UE). 10. The base transceiver station (BTS) according to claim 1, characterized in that the airborne base transceiver station (BTS) is connected to a satellite communication line (4, 5, 6) that processes traffic between the airborne base transceiver station (BTS) and a dedicated base station (6) in the terrestrial network. 11. The base transceiver station (BTS) according to claim 10, characterized in that the satellite communication line (4, 5, 6) contains an on-board satellite antenna (4), configured to send signals to a satellite (5) located at a higher level than the aircraft (6). 12. A method for a transceiver station (BTS) for a cellular communication system comprising user equipment (UE) on board an aircraft (1) at a predetermined height and a terrestrial network, characterized in that it comprises the following steps:
a base transceiver station (BTS) is configured as an airborne base transceiver station (BTS) comprising a shielding device (2) generating a first signal (S1) matched to shield a second signal (S2) from a terrestrial network at a predetermined height,
the airborne base transceiver station (BTS) also comprises a signal generator (3) generating a third signal (S3), which is stronger than both the first signal (S1) and the second signal (S2),
an airborne base transceiver station (BTS) establishes a communication link with a user equipment (UE) through a third signal (S3). 13. The method according to item 12, wherein the third signal (S3) has a third frequency range that is at least partially or completely within the first frequency range (S1F2) of the first signal (S1). 14. The method according to item 13, wherein the first frequency range (S1F1) is equal to or greater than the second frequency range (S2F2) of the second signal (S2). 15. The method according to p. 12, characterized in that the first signal (S1) has a first level, agreed to screen a second signal (S2) having a second level, and the third signal (S3) has a third level, which is larger than the first level and / or second level. 16. The method according to p. 12, characterized in that the shielding device (2) generates a first signal (S1) in the form of a pulsed first signal (S1), matched for shielding the control channel (F; S; B) in the second signal (S2) .

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