A small cell base station, and a method of controlling communications between a user terminal and a small cell base station

<u>Field of the Invention</u>

The present invention relates to telecommunications, in particular to wireless telecommunications.

<u>Description of the Related Art</u>

Nowadays cellular wireless telecommunications to or from mobile user terminals are the most used form of telecommunications. The success of this technology is mainly due to its ubiquity, in that a connection can be made to or from almost anywhere.

However, there are scenarios where, in a certain area, wireless telecommunications are not allowed and so have to be blocked. This may be the case in, for example, examination rooms, conference rooms, classrooms, courtrooms and other areas, rooms or places. Blocking may be in order to suppress the exchange of information within the area or between inside the area and outside, or may be where the presence of cellular wireless terminals or equipment generate radio interference or other undesirable situations.

Use of radio jammers is a known way to seek to solve this problem. However, jammers block all kinds of wireless communication in the frequency range in which the jamming occurs, including emergency calls. This is contrary to legal regulations and is potentially dangerous.

Furthermore, a jamming signal interferes not only with the communication within the desired area but other areas nearby. Therefore jammers interfere with communications with users that it is not intended to block, such as people walking outside the dedicated area, for example outside a hospital treatment room or school examination hall.

<u>Summary</u>

The reader is referred to the appended independent claims. Some preferred features are laid out in the dependent claims.

An example of the present invention is a method of controlling communications between a user terminal and a small cell base station. The method comprises sensing that the user terminal has entered the radio coverage area of the small cell base station; receiving from the user terminal an identifier of the user terminal; adding the identifier to a record of identifiers of user terminals to be denied connections; and denying requests for connection with the user terminals identified in the record.

In some embodiments, communications are controlled within a certain area, room or building by placing the small cell base station within the area, room or building so that the small cell base station provides coverage to this area.

In some embodiments, mobile communications with user terminals in selected areas are controlled in an efficient manner.

In some embodiments, denying a request for connection may be blocking a connection, for example of any type of call except for emergency calls.

A connection may be a call connection, for example a voice- and/or data-connection, for example a voice calls, data session, SMS message, or video stream.

In some embodiments, one or more small cell base stations are deployed in a restricted area within which mobile communications must be controlled. Accordingly, a list is created of SIM cards that are not allowed to start or receive a mobile communication, for example a call or data session.

In some embodiments, the list is created using sensors placed in the entrance(s) of a room, where the sensors are able to detect and register SIM details (for example International Mobile Subscriber Identity, IMSI). In some embodiments, the list is added to by the application of specific procedures when a user terminal attempts to connect to the small cell base station.

In some embodiments, the small cell base station is part of a network that includes macrocells, and all user terminals within the small cell are forced to connect to, or attempt to connect to, the small cell base station and so be controlled by the small cell base station.

In some embodiments, the list is an access control list for which specific policies are applied. In some embodiments the list may be subdivided dependent upon, for example, whether an access authorisation code is received from a user terminal, so that different policies are applied to each sub-list. For example, teachers in an examination hall who provide the correct key code may initiate data sessions even during an examination.

In some embodiments, both near-entrance sensors and the small cell base station itself are used to detect a new user terminal in the restricted area. This means users in an area where there is spill-out of signals beyond the intended restricted area, for example near windows outside a room, are not restricted in call access.

Another example of the present invention is a small cell base station comprising means to sense that a user terminal has entered the radio coverage area of the small cell base station; means to receive from the user terminal an identifier of the user terminal; means to add the identifier to a record of identifiers of user terminals to be denied connections; and means to deny connection requests with user terminals identified in the record.

Some embodiments comprise means upon receiving the identifier to request an access control code within a given time to avoid the identifier being added to the record of identifiers of user terminals to be denied connections. Some embodiments comprise means configured to, upon the user terminal being detected as leaving or having left the coverage area of the small cell base station, remove the identifier of the user terminal from the record of user terminals to be denied connections.

<u>Brief Description of the Drawings</u>

An embodiment of the present invention will now be described by way of example and with reference to the drawings, in which: <ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">Figure 1</figref> is a diagram illustrating a scenario in which a femtocell base station is used according to a first embodiment of the present invention.</li><li><figref idref="f0001">Figure 2</figref> is a diagram illustrating in more detail the femtocell base station and sensor gate shown in <figref idref="f0001">Figure 1</figref>,</li><li><figref idref="f0002">Figure 3</figref> is a flow diagram illustrating operation of the femtocell base station and sensor gate shown in <figref idref="f0001">Figure 2</figref> in adding an identifier of a user terminal to a list of blocked users,</li><li><figref idref="f0003">Figure 4</figref> is a flow diagram illustrating operation of the femtocell base station and sensor gate shown in <figref idref="f0001">Figure 2</figref> in removing an identifier of a user terminal from the list of blocked users,</li><li><figref idref="f0004">Figure 5</figref> is a diagram illustrating a femtocell base station according to a second embodiment of the invention in which the femtocell base station identifies a user terminal to be blocked,</li><li><figref idref="f0005">Figure 6</figref> is a flow diagram illustrating operation of the femtocell base station shown in <figref idref="f0004">Figure 5</figref> when there is no active call,</li><li><figref idref="f0006">Figure 7</figref> is a flow diagram illustrating operation of the femtocell base station shown in <figref idref="f0004">Figure 5</figref> when there is an active call, and</li><li><figref idref="f0007">Figure 8</figref> is a diagram illustrating a femtocell base station according to a third embodiment of the invention.</li></ul>

<u>Detailed Description</u>

The inventors realised that conventionally students keep using cellular mobile phones during class periods, usually in silent mode. Mobile phones are used at school to send SMS text messages, send answers to a classmate, receive answers from another classmate, use the Internet to retrieve information (in other words looking up answers), chat using Instant Messaging (IM) applications, take pictures or shoot video using the integrated camera. The inventors realised that in classroom or examination conditions, these acts may lie on a spectrum of undesirable behaviour between moderate class disruption and serious examination fraud.

The inventors found a useful counter-measure to prevent the use of mobile phones in classrooms, particularly during an examination, or in other places, for example, to prevent the exchange of information within a room, or between the room and outside. They developed an approach that is applicable to larger environments, such as a school or court building or a campus. The inventors provide an approach that enables teachers and administrators to enforce the ban on cellular mobile phones at school.

As will be described in detail below, the inventors realised that an identifier of a subscriber, specifically from the Subscriber Interface Module, SIM, for example the International Mobile Subscriber Identity, IMSI, may be detected and used to generate a list of user terminals to which access is restricted. The IMSIs may be determined using sensors or by a femtocell base station, as described below. The list may be stored on the femtocell base station together with an associated policy or policies to be applied. For example, a default policy may be: no outgoing calls, no incoming calls, allow emergency calls.

As shown in <figref idref="f0001">Figure 1</figref>, a femtocell base station 2 for wireless telecommunications is provided including a Digital Subscriber Line, DSL, backhaul link 4 for connection over the Internet 6 to a mobile operator's core network 8 of known type via a Home Location Register, HLR, 10 of known type. The inventors realised that a user terminal 14 will seek to connect to the base station providing the strongest signal, for example the femtocell base station 2 in a classroom 12 in which the user terminal 14 is. The inventors realised that the base station 2 will "hook up", in other words connect to, the user terminal 14, and using the IMSI as a key to a Home Location Register, HLR 10, of known type, the user terminal may be authenticated and authorised to connect to a mobile operator's core network 8.

As shown in <figref idref="f0001">Figure 1</figref>, the classroom 12 includes an entrance 16 and two windows 18. There is a signal spillout area 20 outside of the room 12 through each window 18. There is a sensor gate 22 across the entrance 16. The sensor gate 22 is connected to the femtocell base station 2.

As shown in <figref idref="f0001">Figure 2</figref>, the sensor gate 22 includes two sensors 24 connected to an International Mobile Subscriber Identity (IMSI) decoder 26. In use a person entering or leaving the classroom 12 via the entrance 16 passes between the two sensors 24. The sensors 24 are of known type, having ranges of tens of centimetres to metres. Each sensor 24 can detect a mobile user terminal that is brought near and cause the user terminal to provide its IMSI to the sensor, from where the IMSI is forwarded to the IMSI decoder 26.

In this example, the femtocell base station 2 is connected to the sensor gate 22 via a wired connection cable 28 according to a standard protocol. In some otherwise similar alternative embodiments (not shown) the connection between sensor gate and femtocell base station is a wireless connection, for example in accordance with the Zigbee or Bluetooth interface or using a wireless Universal Signal Bus (USB) connection.

As shown in <figref idref="f0001">Figure 2</figref>, the IMSI decoder 26 of the sensor gate 22 is connected via cable 28 to a sensor-gate-interface 30 in the femtocell base station 2. The interface 30 is connected to memory 32 containing an access control list. The memory 32 is connected to a control policy applicator 34 which is also connected to a control policy record 36.

IMSI

collection and access control list creation

In this example, the IMSI of each user terminal entering the classroom 12 is detected by the sensor gate 22. Use of the sensor gate means that only user terminals detected by the sensor are put on the access control list. In alternative examples that will be described later, IMSIs are detected by the femtocell base station instead, or by a combination of the sensor gate and the femtocell base station.

Returning to the example shown in <figref idref="f0001">Figures 1 and 2</figref>, as shown in <figref idref="f0002">Figure 3</figref>, a user terminal 14 entering the classroom 12 is detected (step a) by at least one of the sensors 24 causing decoding (step b) of the IMSI in a signal received from the user terminal by the IMSI decoder 26. The decoded IMSI is passed via the cable 28 and interface 30 to the memory 32 where that IMSI is added (step c) to a list of user terminals (an "access control list").

Applying the access control list to block calls

The control policy record 36 provides the access control policies to be applied to the user terminals identified on the list. These policies are applied by a control policy applicator 34 to user terminals listed on the access control list.

In use, upon receiving a call setup request, the control policy applicator 34 in the femtocell base station 2 accesses the access control list in the memory 32 to check whether a user terminal in the femtocell is one to which the access control polices should be applied.

In this example, the control policies are to deny requests to setup calls, except for emergency calls, from or to user terminals whose IMSIs are currently on the access control list in the memory 32. User terminals in the classroom 12 are blocked from making or receiving non-emergency calls, including data sessions.

Removing an IMSI from the access control list

As shown in <figref idref="f0003">Figure 4</figref>, upon a user terminal's IMSI being added to the access control list, an associated timer T is started (step d). When the given timeout period Tmax is reached (step e) by the timer, the femtocell base station 2 checks (step f) whether or not that user terminal is still connected. If yes, the timer is restarted (step g). If No, that user terminal's IMSI is removed from the access control list.

Agreements between mobile network operators

Traditionally, any particular user terminal may only connect to base stations of mobile network operator to which the user terminal subscribes, and a user terminal associated with a first operator is not allowed to connect to a base station of a different mobile operator.

However, in this embodiment a so-called roaming agreement is set up so that user terminals of any operator that is party to the agreement are also able to connect to a base station of another operator who is party to the agreement. Specifically the femtocell base station 2 is in a restricted area where the roaming agreement applies such that user terminals of any operator, upon entry to the classroom, are placed on the access control list for call blocking purposes.

Allowing some users

In some otherwise similar examples, rather than blocking calls in respect of all users in the classroom, a certain group of user terminals within the classroom retain access so can make calls freely. The group may be user terminals of security staff and teachers, for example. In one example upon a user terminal being detected, for example by the sensor gate (or femtocell base station), a security code known only to a user who is a member of staff can be requested. The member of staff who responds with the keycode avoid the IMSI of his user terminal being added to the access control list.

In another example, the femtocell base station is programmed with a list of user terminals whose IMSIs are not to be included on the access control list of users who can only make/receive emergency calls, but are noted in a list of IMSIs of user terminals who are allowed full access to make and receive calls when in the classroom.

An alternative: IMSI detection by the femtocell base station

In a further example, the IMSI of a user terminal is detected by a femtocell base station 2' instead of by a sensor gate. Use of the femtocell base station to detect user terminals to put on the access control list is more secure than relying on a sensor gate only. This is because bypassing a sensor, for example by smuggling the user terminal in via a window, would not avoid access control.

As shown in <figref idref="f0004">Figure 5</figref>, in this example, the femtocell base station 2' includes a radio receiver 38 connected to an IMSI decoder 40 in the femtocell base station 2'. The IMSI decoder 40 is connected to a memory 32' storing an access control listvia a list controller 42. The memory 32' is connected to a control policy applicator 34' which is also connected to a control policy record 36'. The list controller 42 is also connected to an SMS/voice message generator 44 that is connected to a transmitter 46.

Operation in this example is illustrated in <figref idref="f0005">Figures 6</figref> and <figref idref="f0006">7</figref>.

<u>No active call:</u> As shown in <figref idref="f0005">Figure 6</figref>, in the case where the detected user terminal is not in an active call, the IMSI decoder 40 of femtocell base station 2' detects (step a') an IMSI, causing that decoded IMSI to be registered (step b')by a list controller 42. The IMSI may be provided to the femtocell base station 2' for example upon entering the classroom or upon the user terminal being rebooted inside the classroom. In the list controller 42 a query is made (step c') of the memory 32 to determine whether that IMSI is already included in the access control list.

If Yes, the list controller 42 instructs the control policy applicator 34' to restrict access (step d') in accordance with the control policy in the record 36'.

If No, the list controller 42 triggers the SMS generator to automatically generate (step e') a Short Message Service, SMS, text message that reads: "Limited Service Restricted Area. Please move away from your current location or enter a security code." The SMS message is transmitted (step f) to the user terminal by the transmitter 46. The IMSI is then added (step g') to the access control list in the memory 32' in the femtocell base station 2'. This enables, a user terminal outside the classroom 2 in a spillout area 20 to move a few metres and so avoid being unable to make or receive calls.

Although not shown in detail in <figref idref="f0005">Figure 6</figref>, should the correct security code be entered, the user terminal is not placed on the access control list, but on a list (not shown) in the femtocell base station of user terminals that are allowed access.

<u>Active call:</u> As shown in <figref idref="f0006">Figure 7</figref>, in the case where the detected user terminal is in an active call, the IMSI decoder 40 of femtocell base station 2' detects (step a") an IMSI, causing that decoded IMSI to be registered (step b") by a list controller 42. The IMSI may be provided to the femtocell base station 2' for example upon the user terminal in a call entering the classroom.

The list controller 42 determines (step c") whether or not the active call is a voice call (rather than a data session).

If No, the list controller instructs the SMS/voice message generator 44 to send, via transmitter 46, an SMS text message which reads "Restricted area- Please move away from your current location or enter the security code, else your session will be disconnected in TDmax." Of course, TDmax is specified in the message as a number of seconds, say 15 seconds for example. This message is sent (step d") and in the list controller 42 a timer is started(step e", step f"). Upon the timeout period TDmax being reached (step g") without the user terminal being detected as moving out of the femtocell nor without the security code being successfully received and processed, then the IMSI is added (step h") to the access control list in the memory 32' in the femtocell base station 2'.

If at step c", the answer is Yes, namely the call is determined as being a voice call, then the list controller 42 sends (step i") via SMS/voice message generator 44 and the transmitter 46, a voice message. The voice message is an automatically generated voice message which states "Restricted area- Please move away from your current location or enter the security code, else your session will be disconnected in TVmax." TDmax is specified in the message as a number of seconds, say 15 seconds, for example. Upon the voice message being sent a timer is started(step j", k")in the list controller 42. Upon the timeout period TDmax being reached (step <i>I</i>") without the user terminal being detected as moving out of the femtocell nor without the security code being successfully received and processed, then the IMSI is added (step h") to the access control list in the memory 32' in the femtocell base station 2'. The voice message is a short pre-recorded message which temporarily interrupts the call conversation.

In a similar embodiment a web-based pop-up message may be provided to the user terminal in place of the SMS text message.

Use of the femtocell base station to detect user terminals to put on the access control list is more secure than relying on the sensor gate only as bypassing a sensor, for example by smuggling the user terminal in via a window, would not avoid access control. However, the femtocell base station may put onto the access control list, a user terminal within the femocell but outside the classroom, namely in the spillout area near a window. This may be undesirable in some circumstances.

Another alternative: IMSI detection by the femtocell base station and sensor gate in combination

As shown in <figref idref="f0007">Figure 8</figref>, depending on the level of security required and how desirable it is to avoid users outside of the classroom, or other intended area, from being blocked, both the small cell base station and a sensor gate may be used to determine IMSIs of user terminals to be added to an access control list. This ensures that only user terminals that have passed through the sensor gate and are connected to the femtocell base station are blocked. User terminals that are connected to the femtocell base station but have not passed the sensor gate, so are outside the room, are not blocked.

As shown in <figref idref="f0007">Figure 8</figref>, the sensors 24' of the sensor gate 22' are connected via an IMSI decoder 23 located in the sensor gate. The femtocell base station 2" includes a receiver 25 connected to an IMSI decoder 27 in the femtocell base station 2". A list controller 29 receives input from both IMSI decoders 23,27 to determine whether an IMSI detected by both sensor gate 22' and femtocell base station 2' should be added to the access control list. Only if the IMSI in question is detected in both ways at a similar time, is the IMSI added to the access control list.

In this example, in summary, an IMSI is only added to the access control list, and hence calls of the corresponding user terminal blocked where both (a) the user terminal is connected to the femtocell base station and (b) the IMSI of the user terminal has been detected by the sensors.

The present invention may be embodied in other specific forms without departing from its essential characteristics. For example, in an otherwise similar embodiment to that described above involving roaming agreements for a femtocell base station, a multi-operator femtocell base station of known type is used instead, having an access control list in which user terminals of any operator may be listed (for application of access control polices).

In some embodiments various types of access control policies may be applied; for example emergency calls only, or data sessions and emergency calls only.

In some embodiments multiple access control policies may be applied, for example no calls except emergency calls from students, but data calls being allowed for teachers at examination time who have replied with the correct key-code.

The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes that come within the meaning and range of equivalency of the claims arc to be embraced within their scope.

A person skilled in the art would readily recognize that steps of various above-described methods can be performed by programmed computers. Some embodiments relate to program storage devices, e.g., digital data storage media, which are machine or computer readable and encode machine-executable or computer-executable programs of instructions, wherein said instructions perform some or all of the steps of said above-described methods. The program storage devices may be, e.g., digital memories, magnetic storage media such as a magnetic disks and magnetic tapes, hard drives, or optically readable digital data storage media. Some embodiments involve computers programmed to perform said steps of the above-described methods.