Mobile communication system and a mobile station, a base transceiver station and a method for use therein

A mobile communication system, a mobile station, a base transceiver station, and a method for using the same

BACKGROUND OF THE INVENTION Field of the Invention [0001] The present invention relates to mobile communication systems and mobile stations, base transceiver stations, and methods of use in the systems, and more particularly, to the detection of interference by jamming and resulting motion in mobile communication systems.

A mobile communication system is a mobile or portable user terminal, such as a mobile phone, portable radiotelephone or in-vehicle radiotelephone, collectively referred to herein as 'mobile station' or 'MS' (in the singular, 'MS') is a 'base' in the related art. Communication over a network infrastructure that generally includes a fixed facility comprising at least one fixed base station, known as a transceiver station' or 'BTS', and several subsystems for management and control of the system comprising at least one BTS. can do. The system may be, for example, cellular comprising a plurality of BTSs, where each BTS serves MSs in any area or area known as a 'cell' or 'site' by wireless communication. In such systems, cells of adjacent BTSs often overlap.

In a mobile communication system, the signal sent from the MS to the BTS that serves them is known as the 'uplink' signal. The signal sent from the BTS to the MS is called a 'downlink' signal. The uplink and downlink signals can usually be sent on different channels, for example on different carrier frequencies.

A mobile communication system, particularly a cellular system, may be a frequency trunked system in which a radio channel of the system is shared between MSs for different communications, and each channel is assigned for a specific communication only during a temporary period.

Different types of communication in a mobile communication system originating from a BTS or MS may be transmitted on different channels dedicated to different types of communication. For example, the channel used may include a control channel and a traffic channel in which the transmitted communication includes a control signal and a traffic signal, respectively. There may be different channels for different traffic types, for example voice communication, short data and packet data information. In a system operating according to the TDMA (Time Division Multiple Access) protocol, different channels are provided by different specific time slots or slot frames of a single RF carrier, and these different time slots or frames of slots are used by all terminals in the system. is provided in a timing structure.

Users of MSs generally require a high degree of service and reliable connections while using the system for several services such as telephone calls, dispatch calls and data transfer, particularly more advanced data transfer such as the transfer of pictures or video images. .

In general, in cellular systems, it is desirable for the MS to be served by a selected BTS that can provide a good radio signal to and from the MS. As MSs move from one area to another, determine whether they need to switch from their current serving BTS to another in order to receive better service and take steps to determine if it is appropriate to perform such a transition. For this purpose, it is known for MSs to monitor signals from different BTSs. In the present technology, the process for monitoring and making decisions regarding these possible transitions is known as a "cell reselection" process. This usually works in two steps: (i) the mobile station transfers a list of candidate non-serving BTSs that are likely to switch to that serving BTS, including the preferred non-serving BTS selected as being at the top of the list. A first step of creating, (ii) comparing the signal from the preferred non-serving BTS with that from the current serving BTS, a second step of performing measurements to determine if certain criteria are met that require a transition to the preferred BTS to be made works with When this standard is met, a process known as 'handover' or 'handoff' is executed to effect this transition so that the MS is served by the desired BTS.

Any radio link may be a potential target for interference caused accidentally or intentionally (eg, by malicious action). The risk of accidental interference may be increased by the coexistence of different systems or devices in the same area sharing the same (or close to) frequency. Moreover, in cellular communication systems, accidental interference can be caused by improper frequency reuse strategies or by unusual propagation conditions. However, accidental interference can be eliminated by careful planning and design of the system.

Interference due to jamming is a bigger problem because when it occurs, all communication on the jammed channel or channels can be esoteric noise rather than a useful signal. It is the downlink channel, particularly the downlink control channel, that provides a more sensitive communication link, i.e., more preferred by malicious parties to jam. All services to MSs provided by the infrastructure are established using information exchange on the downlink channel from the serving BTS. If the downlink control channel is blocked by interference due to jamming, no service is provided. The risk of jamming of a downlink channel is increased because transmission by the BTS on that downlink channel, usually on any carrier frequency, is actually continuous and can be easily detected and analyzed by receiving a device that is being used for malicious jamming operation. . Conversely, on the uplink channel, there is generally no continuous transmission, and transmission is performed by MSs only when a service is being used or requested to be used by the MS.

EP-A-1304895 describes a known method for detecting interference by jamming of a signal sent by a downlink channel. A polling signal is sent by the BTS to the MSs. MSs automatically send a response message to the BTS when they receive a polling signal. The condition of interference by jamming is considered to exist when no response message is received by the BTS, indicating that the MSs are not satisfactorily receiving the polling signal.

According to a first aspect of the present invention, there is provided a mobile communication system as defined in claim 1 of the appended claims.

According to a second aspect of the present invention, there is provided a mobile station as defined in claim 17 of the appended claims.

According to a third aspect of the present invention, there is provided a base transceiver station as defined in claim 19 of the appended claims.

According to a fourth aspect of the present invention, there is provided a method as defined in claim 21 of the appended claims.

Other features of the invention are defined in the appended dependent claims or are set forth in the embodiments of the invention later described herein.

1 is a schematic block diagram of an illustrative mobile communication system embodying the present invention;

FIG. 2 is a schematic block diagram illustrating the configuration of functional components of a mobile station in the system of FIG. 1 .

Fig. 3 is a flowchart illustrating a method of operation embodying the present invention in the system of Fig. 1;

Fig. 4 is a flowchart illustrating another method of operation embodying the present invention in the system of Fig. 1;

BRIEF DESCRIPTION OF THE DRAWINGS Embodiments of the present invention are described below by way of illustration with reference to the accompanying drawings.

1 is a schematic block diagram illustrating a mobile communication system 100 embodying the present invention. System 100 includes a plurality of MSs, six of which are shown, MS 101 , 103 , 105 , 107 , 109 , and 111 , and a fixed infrastructure 121 . Infrastructure 121 includes a plurality of BTSs, two of which are shown, BTS 123 and adjacent BTS 129 . BTSs 123 and 129 are operatively connected together by a link 135 . BTSs 123 and 129 are also operatively coupled to controller 137 by links 139 and 141, respectively. Links 135 , 139 , and 141 may be known wired or wireless links depending on the particular implementation of system 100 .

Controller 137 provides administrative control of BTSs of system 100 including BTS 123 and BTS 129 and other infrastructure functional units of system 100 (not shown). The controller 137 may take one of a number of possible forms. It may be a separate unit or may be integrated with other functional units such as MS mobile databases. For example, controller 137 may include or be coupled to a zone controller, which controls operation in geographic zones of system 100 .

The BTS 123 is a basic operation constituent unit (along with other constituent units not shown), including a processor 125 that executes signal processing and control functions within the BTS 123, and a timer that controls the timing of operations in the BTS 123. 128) and a transceiver 127 for transmitting and receiving wireless communication signals to the MSs served by the BTS 123. MSs 101 , 103 , and 105 are currently served by BTS 123 because they are closer to BTS 123 than to BTS 129 (and other BTSs not shown).

BTS 125 is similarly a basic operating component unit (along with other components not shown) that controls the timing of operations in BTS 129, and processor 131 that executes signal processing and control functions within BTS 125. a timer 134 and a transceiver 133 for transmitting and receiving wireless communication signals to and from MSs served by the BTS 129 . MSs 107, 109, and 111 are closer to BTS 129 than to BTS 123 (and other BTSs not shown) and therefore are currently served by BTS 129.

2 is a block schematic diagram illustrating details of the illustrative form 200 of the MS 10 . MSs 103-111 are configured and operated in a similar manner. In this form 200, the operating function of MS 101 is a timer 209 that synchronizes with the operation in form 200 of MS 10 and data and programs used within form 200 of MS 10. It is controlled by the controller 201 operating in relation to the memory 210 to store. The signal processor 202 processes information included in the RF signal transmitted and received by the transceiver 203 . The signal processor 202 extracts information from the received RF signal detected by the transceiver 203 and passes this information to an appropriate output transducer. Similarly, signal processor 202 receives input information for transmission from an appropriate input transducer and passes this information to transceiver 203 for transmission by transducer 203 in the form of an RF signal. Form 200 of MS 101 includes an audio output 204 which is an output transducer, for example a speaker, which converts a received signal representing speech information into an output audible form for delivery to a user. Form 200 of MS 101 comprises an audio input 205 which is an input transducer, for example a microphone, which converts an input audio signal, for example in the form of speech, into electrical form in a well-known way. . The electrical signal is passed to the signal processor 202 described above.

The data connector 213 provides an output to data received as an RF signal from the transceiver 203 and extracted by the signal processor 202 . The data connector 213 also provides an input for data transfer to the signal processor 202 for transmission in an RF transmission by the transceiver 203 . Data connector 213 includes a connection to one or more peripheral devices (not shown), eg, a computing device running a data processing application, eg, a USB data connection. The keypad 212 acts as a user interface to allow the user to input control signals for transmission to the controller 201 to operate the functions of the form 200 of the MS 101 . Keypad 212 also acts as another input transducer that allows input of Receiver data for transmission to signal processor 202 for processing to send wireless communications as short data by transceiver 203 . The display 207 operated by the display driver 206 under the control of the controller 201 provides the displayed information to the user of the MS 101 in the manner shown.

The received signal strength and quality processor 214 measures the RSSI (received signal strength indication) of the signal received by the transducer 203 in a known manner and also the BER (bit error rate) or frame error rate of the received signal. (FER) is measured by a known method to measure quality. The processor 214 may process data using the measured RSSI and quality in a manner described below with respect to FIG. 3 .

Battery 211 provides electrical power to all operating components of form 200 of MS 101 . The transceiver 203 provides RF communication to and from the transceiver (one of the transistors 127) of another terminal operating within the system 100, in particular the transceiver of the BTS 123 serving the MS 101. do. The transceiver 203 may also receive signals from other BTSs for use in known cell reselection procedures as already referenced. The transceiver 203 may also provide RF communication directly to and from one or more of the MSs 103-111 if the MSs 101-111 can communicate in direct mode without infrastructure 121 . .

3 is a flowchart of a method 300 of operation embodying the present invention in system 100 . As indicated by step 301, the BTS 123 operates on a downlink channel, which is one of a pair of channels assigned by the controller 137 for operational use by one of the transceivers 127 of the BTS 123. Usually, a signal is sent to the MS 101. The other of the pair usually signals a particular one of the transceivers 127 as the uplink channel for use by the MS 101 . In step 303, the MS 101 receives the signal sent by the BTS 123 and stores training data relating to the received signal in its memory 210 (of type 200) to characterize the normal operation. do. In step 305, intentional interference by jamming (from a jamming source not shown) begins to be applied to the signal sent on the downlink channel from the BTS 123 to the MS 101. In step 307, MS 101 detects interference due to jamming of the signal from BTS 123. The method used by MS 101 to detect jamming may be a known method. Several such methods are known in the art. For example, the MS 101 of form 200 may display, at the processor 214 , data regarding RSSI (received signal strength indication) and quality measured by, for example, BER (bit error rate) of the received signal. can be correlated. If the RSSI is greater than the predetermined threshold and the quality is also lower than the predetermined threshold (ie, the BER is high), the processor 214 determines that interference by jamming has been detected. The threshold used for this correlation is set using stored training data in step 303 . At step 309, the MS 101 prepares to send a notification message to the infrastructure 121 that the MS 101 has detected interference due to jamming of a signal sent on the downlink channel from the BTS 123. Notify the infrastructure 121 . Identification information of the BTS 123 and/or the associated downlink channel(s) is specified in detail in the notification message. The notification message may be prepared by the signal processor 202 under instructions from the controller 201 in the form 200 of the MS 101 .

At decision step 311, the MS 101 determines whether it can send a signal on the uplink channel to its serving BTS, i.e., BTS 123, including a notification message to be received by the BTS 123. do. If the MS 101 determines in step 311 that this signal on the uplink channel is possible, i.e. the result of the determination in step 311 is 'YES', then the MS 101 determines in step 313 that this signal on the uplink channel is possible. A signal including a notification message is sent to the BTS 123 on the BTS 123 . If the MS 101 determines in step 311 that the signal on the uplink channel arriving at the BTS 123 is not possible due to jamming, i.e. the result of the determination in step 311 is NO, the MS sends a message find another way to send In another decision step 315, the MS 101 determines whether it can signal its serving BTS, BTS 123, on the unidirectional communication channel. This channel may be used in system 100 to provide random access to a particular channel, such as, for example, the BTS 123's packet data channel. If the MS 101 determines in decision step 315 that signaling on the channel in a simple manner is possible, i.e. a 'yes' decision, then the MS 101 determines in step 317 this message on the unidirectional channel including a notification message. send a signal If the MS 101 determines at decision step 315 that the signal on the unidirectional channel is not possible, i.e., a 'no' decision, step 319 follows. Step 319 (and subsequent steps) follows although steps 313 and/or 317 have already occurred to act as a backup notification process.

In step 319, the MS 101 undergoes cell reselection and handover procedures in a manner known in the related art. The process is automatically triggered by MS 101 to determine that BTS 123 is no longer a serving BTS. Assuming that the result of the cell reselection and handover process is that BTS 129 becomes the new serving BTS of MS 101, MS 101 sends a signal on its uplink channel to BTS 129 in step 321. send. Finally, in step 323, the new serving BTS 129 relays a notification message to the BTS 123 that has detected that its downlink channel signal is being interfered with by jamming. Notification messages are sent via link 135 .

Thus, the result of method 300 is that MS 101 receives a notification message sent to MS 101 by BTS 123 in one or more of steps 313, 317, and 323 for MS 101 to send a notification message to MS 101 on the downlink channel. 123) indicates that interference due to jamming of the signal sent to the MS 101 is detected. The received notification message includes a message in a standard format used within the system 101 and can be understood by the processor 125 of the BTS 123 . For example, the notification message includes a standard PDU (protocol data unit) message in which the identification information of the MS 101 and the identification information of a channel detected to be subject to interference by jamming are variable data fields.

Steps similar to steps 307 - 321 apply to other MSs served by BTS 123, such as MSs 103 and 105 . Thus, BTS 123 receives, by method 300, a notification message regarding interference detection by jamming from a plurality of MSs served by BTS 123.

4 is a flowchart of another method 400 embodying the present invention. The method 400 operates by the BTS 123 upon receiving (by the method 300) one or more notification messages notifying them of interference by jamming to a signal sent by the BTS 123 on a downlink channel. do. Another method 400 begins at step 401 with receiving a notification message that a signal transmitted by the BTS 123 on the downlink channel is being interfered with by jamming. In a subsequent step 403 in response to step 401, the BTS 123 determines that a jamming condition exists with respect to the signal sent by the BTS 123 on the downlink channel, i. Initiate the process (algorithm) to confirm that it is received. This process is operated by the processor 125 of the BTS 123 . In step 405, the BTS 123 determines whether a number of notification messages received from different MSs have reached a predetermined threshold or minimum number. In step 407, the BTS determines whether the time interval between the different notification messages has reached a minimum time interval. Step 407 is to prevent a pseudo-interference blip not due to jamming, for example using the timer 128, from being incorrectly identified as jamming. If an affirmative judgment is made in step 405 or step 407, preferably a combination of the two steps, step 409 follows. In step 409, the BTS 123 tunes the receiver of its transceiver 127 to the downlink channel that has been notified of being interfered with by jamming. The BTS 123, e.g., the processor 125, then proceeds to the BTS 123 by its own receiver to determine whether there is interference by jamming the signal on the downlink channel. (411) applies. This may be a detection procedure similar to the detection procedure operated by MSs including MS 101 in this method 300 and/or a different detection procedure. Step 413 following step 411 presents an indication by the detection process that interference due to jamming on the downlink channel has been identified. In response to step 413 , step 415 is followed by the BTS 123 sending a jamming notification message to the controller 137 via link 139 . The jamming notification message notifies the controller 137 of a jamming condition. In response to receiving the jamming notification message sent in step 415, the controller 137 tells the BTS 123 in step 417 the transmission frequency (carrier frequency) of the downlink channel subject to interference by jamming of other frequencies. command to change. Controller 137 knows the distribution of transmit frequencies used in system 100 and can determine and specify other frequencies suitable for use in the downlink channel for BTS 123 .

In step 419, the BTS 123 changes its working downlink channel to the new transmit frequency notified by the controller 137 in step 417 and the BTS 123 provides the new frequency to the MS and other BTSs. Send a broadcast signal to notify. This allows MSs that have applied the cell reselection and handover procedure to service the BTS 123 again when interference due to jamming is detected to apply another cell reselection and handover procedure if appropriate.

The BTS 123 periodically applies a jamming condition, i.e., a process of determining whether interference due to jamming of the signal sent by the BTS 123 on the original downlink channel frequency persists. This is represented by step 421 . This process may be commanded by the controller 137 or operated periodically by the BTS 123 at predetermined intervals indicated by the timer 128 of the BTS 123 . The BTS 123 detects in step 423 whether the interference previously detected by jamming has ceased. Responsive to step 423, in a selection step 425, the BTS 123 changes the transmit frequency of its downlink channel back to the previous frequency subject to interference by jamming. The changes in step 425 may be made automatically by the BTS 123 or may be commanded by the controller 137 . Finally, following step 425, step 427 is applied in which the BTS 123 sends a broadcast signal to notify the MSs and other BTSs that it has changed back to the previous transmit frequency for its downlink channel. .

The operation of method 300 causes interference by jamming of a signal sent on a downlink channel of BTS 123 to be detected by MSs, such as MSs 101-105, and reported to BTS 123. The operation of method 400, preferably after being notified and commanded by controller 137, causes BTS 123 to check for interference reported by the jamming condition and change its downlink channel to a different frequency. The BTS 123 does not need to send a polling test signal to the MSs as often as in the process described in EP-A-1304895 to know if a response has been sent from the test signal. Preferably, this conserves valuable processing resources on the BTS 123. Moreover, unlike the method of EP-A-1304895, the BTS 123 does not need to know which MSs are active at all times, but this method 300 does not require the serviced BTS, i.e., the MSs served by the BTS 123. It is assumed that at least some will activate satisfactorily to detect a condition with interference by jamming. Further, the method 300 includes determining one or more suitable methods for the MSs to send notification messages to the infrastructure, particularly the BTS 123, for detected interference by jamming conditions. This ensures that these messages reach their target destination in the infrastructure 121 . Conversely, in the method of EP-A-1304895 MSs do not make an information processing decision on how to send a response message.

The methods 300 and 400 can be applied in various mobile communication systems capable of interference by jamming of a downlink signal sent by a base transceiver station. For example, the methods 300 and 400 are defined by the GSM standard or TETRA standard as defined by the European Telecommunications Standards Institute (ETSI) or the Association of Public-Safety Communications Officials (APCO) 25 as defined by the International Official Public Safety Communications Authority. It can be used in cellular systems such as those operating according to standards.