Field of the Invention This invention relates to routing of calls in a wireless communication system. The invention is applicable to, but not limited to, call screening based on subscriber location in a cellular communication system.

Background of the Invention Wireless communication systems, for example cellular telephony or private mobile radio communication systems, typically provide for radio telecommunication links to be arranged between a plurality of base transceiver stations (BTSs) and a plurality of subscriber units, often termed mobile stations (MSs). The term mobile station generally includes both hand-portable and vehicular mounted radio units.

Wireless communication systems are distinguished over fixed communication systems, such as the public switched telephone network (PSTN), principally in that mobile stations move between service providers (and/or different BTS) and in doing so encounter varying radio propagation environments.

In a wireless communication system, each BTS has associated with it a particular geographical coverage area (or cell). The coverage area is defined by a particular range where the BTS can maintain acceptable communications with MSs operating within its serving cell. Often these cells combine to produce an extensive coverage area.

The communication link from the BTS to a MS is referred as to the down-link. Conversely, the communications link from a MS to the BTS is referred to as the up-link.

In the field of this invention it is known that information about a subscriber's location can be used to decide how to route an incoming telephone call to a subscriber user. For example, if a subscriber is in his/her normal place of work, it may be more appropriate or efficient to route an incoming call to a fixed line, whereas if (s) he is in a car it would be necessary to route the call to his/her mobile phone.

Additionally, it is also known that location information can be used, for a given subscriber terminal type, to choose which communication link (s) should be used to reduce call cost or delay in delivering the call to the intended recipient.

Furthermore, it is known that telephone calls, including cellular calls, can be screened by the user. The incoming call request may include the number of the caller. This information is propagated through the

infrastructure to the mobile as part of the call setup unless the caller has barred the transfer of this information.

However, this approach has the disadvantage (s) that call screening is performed by either : (i) the caller not wanting to let the called person know who is calling, by barring the identification of the calling person, or (ii) the called person receiving the call, and thereby being interrupted from whatever activity they were involved in. The called person effectively screens the call, usually by reviewing an indication on a display, to determine whether they wish to answer the call.

Clearly, there will be numerous times when the called person does not wish to be disturbed for any reason, or only for emergency calls. The current state of the art means that they are disturbed each and every time, and occasionally, when the caller ID is available, can selectively screen calls, once disturbed.

In summary, there exists a need in the field of this invention to provide a communication system, a communication unit and a method for routing a call in a communication system wherein at least some of the aforementioned disadvantages may be alleviated.

Statement of Invention In accordance with the present invention, there is provided a communication system, as claimed in claim 1.

In accordance with the present invention, there is provided a communication unit, as claimed in claim 13.

In accordance with the present invention, there is provided a method of routing calls to a communication unit, as claimed in claim 17.

Brief Description of the Drawings Exemplary embodiments of the present invention will now be described, with reference to the accompanying drawings, in which : FIG. 1 shows a block diagram of a cellular radio communications system adapted to support the various inventive concepts of a preferred embodiment of the present invention; FIG. 2 shows a cell-based communications system adapted to support the various inventive concepts of a preferred embodiment of the present invention; FIG. 3 shows a block diagram of a subscriber unit adapted to support the inventive concepts of the preferred embodiments of the present invention; and

FIG. 4 shows a flowchart of a call-delivery mechanism in accordance with a preferred embodiment of the present invention.

Description of Preferred Embodiments The preferred embodiment of the invention is described with reference to a TDMA, cell-based communications system such as a GSM cellular or PMR communications system, although the inventive concepts contained herein can readily be extended to other access protocols.

The inventive concepts of the present invention address call screening in a contrasting manner to that taught by the prior art. The present invention addresses call screening by operating at the call admission level (i. e. effectively the acceptance or not of the call by the communication system serving the subscriber).

The decision on whether to admit the call for delivery is based on at least one delivery rule, preferably defined by the user. One example on how the rule (s) can be applied is in the case where a call may or may not be routed to the intended recipient depending on subscriber location. Hence, instead of the subscriber deciding whether or not to answer a call when his/her phone rings, for example via caller line identification (CLI), the system can automatically decide not to accept the call

for subsequent routing to the intended subscriber on the basis of, say, the subscriber's location.

One scenario where the inventive concepts of the present invention can be applied is where the subscriber is found to be at home, and the system, in following the user's delivery rule, may not admit a call originating from the subscriber's place of work or a work colleague. Clearly, the subscriber would have complete control of this operation in the sense that (s) he sets up the rule (s) governing which calls are routed to him/her, and at what times depending on, say, his/her location.

In the preferred embodiment of the invention, this would require the system to know the location of the subscriber to a reasonable level of resolution. It may also require knowledge of the identity of the caller (or the caller's phone) or his/her location or both. Time of day, day of week, a diversion number etc. may also be an input parameter to the decision process, as may a number of other parameters, as described later. With regard to the diversion number option, the recipient may wish to reject calls on time of day, week etc instead of, or in addition to location-based screening. In such a manner, diversion to a different number, for example to a voice mail number or to a colleague, means the call doesn't have to be lost.

The subscriber would be able to set up and edit these rules whenever required, probably via his/her terminal device, for example over-the-air transmission of the

call-delivery rule (s) to the communication system by the subscriber's cellular telephone.

Additionally, it may be appropriate to add further sophistication to the system. For example, a call rejected on the basis of a rule could be diverted to a voice mail system or a work colleague. Furthermore, the caller may be in a position to provide additional information to the system that could override the rejection in certain circumstances, for example by defining the subject of the call or the urgency or importance of the call. However, again, it would be the recipient subscriber who defines the rule (s) associated with such additional information.

To ease the burden on the subscriber in setting up the rules, a number of simplifying approaches can be envisaged. For example, for geographical area based rules, the user could simply say that certain calls should be barred depending on whether the location is residential, business, recreational (e. g. sports centre), or public, for example on a road between areas,'general' rural areas, etc). A system database could then be used to correlate against current location to enforce the rule. Known location determination technology, such as the global positioning system (GPS) could be used to provide such detailed location information.

Finally, it should be noted that this concept is particularly powerful in communication systems where telephone numbers are no longer associated with

particular devices but with individuals, irrespective of the device carried or used at any particular time or in any particular place.

FIG. 1 shows, in outline, a cellular telephone communication system 10 supporting a Global System for Mobile communication (GSM) air-interface in accordance with a preferred embodiment of the invention. The GSM air interface has been defined by the European Telecommunications Standards Institute (ETSI).

Generally, the air-interface protocol is administered from base transceiver sites that are geographically spaced apart-one base site supporting a cell (or, for example, sectors of a cell) as shown in FIG. 2.

Similarly, co-located base transceiver sites supporting, say, both pico-and micro-cellular communications may also benefit from the inventive concepts described herein.

A plurality of subscriber units (12-16) communicate over the selected air-interface 18-20 with a plurality of base transceiver stations (BTS) 22-32. A limited number of MSs 12-16 and BTSs 22-32 are shown for clarity purposes only. The BTSs 22-32 may be connected to a conventional public-switched telephone network (PSTN) 34 through base station controllers (BSCs) 36-40 and mobile switching centres (MSCs) 42-44.

Each BTS 22-32 is principally designed to serve its primary cell, with each BTS 22-32 containing one or more

transceiver units and communicating 56-66 with the rest of the cellular system infrastructure Each Base Station Controller (BSC) 36-40 may control one or more BTSs 22-32, with BSCs 36-40 generally interconnected through MSCs 42-44. Processes within the MSCs are provided to account for the situation where an MS (12-16) passes between two BTS serving areas, for example MS 12 moving from the area covered by BTS 22 to the area covered by BTS 24, where the two BTSs are controlled by different BSCs (BSCs 36 and 38 in this example).

Similar processes are supported in MSCs to account for the situation where an MS moves between serving BTSs where these BTSs are connected to different MSCs. These mechanisms therefore allow the cellular telephone communication system to support handover of the MSs 12-16 between cells for most if not all cases encountered.

Each MSC 42-44 provides a gateway to the PSTN 34, with MSCs 42-44 interconnected through an operations and management centre (OMC) 46 that administers general control of the cellular telephone communication system 10, as will be understood by those skilled in the art.

The various system elements, such as BSCs 36-38 and OMC 46, will include control logic 48,50,52, with the various system elements usually having an associated memory function 54 (shown only in relation to BSC 38 for the sake of clarity). The memory function 54 typically

stores historically compiled operational data as well as in-call data, system information and control algorithms.

A home location register (HLR) 80 is positioned within the infrastructure and is connected with the network of MSCs, generally referred to the Network Sub System (NSS).

Each MSC 42,44 typically has a visitor location register 47,49 associated with it, using information downloaded to it from the HLR 80, generally when MSs first attach to a BTS connected via a BSC to the respective MSC, to identify and route calls to MSs situated within its service area.

In accordance with a preferred embodiment of the present invention, the HLR 80, and VLRs 47,49 have been adapted to include more information in their respective databases (per subscriber) to identify and track MS-related call barring/call routing rules. The respective MSC's VLR 47, 49 copies the full record of the MSs 12-16 call barring/ call routing rule (s), from the HLR 80, when the subscriber is camped on one of its cells.

Consequently, the respective MSCs 42,44 have also been adapted, to use the subscriber's rule (s) and any appropriate call-related information in the incoming call message.

It is within the contemplation of the invention that the delivery rules may use any aspect of a call, to enable the system/MSC to determine whether to route the call to the intended MS 12-16. Such call-related information preferably includes at least one of the following : date

and/or time of the call, caller line identification, caller location, subscriber location, diversion numbers, subject matter of the call (business, personal, general information etc.), urgency or importance of the call.

A more permanent set of subscriber records is held on the HLR 80. The HLR 80 is updated only when subscriber data changes, for example the subscriber's telephone number is changed.

It is within the contemplation of the invention that such call routing decisions may be performed at levels or positions within the infrastructure other than at the MSCs 42,44. Such decisions, for example, could be made at the OMC 46, with an approval for continuing routing the call requested from the OMC 46 before the MSC 42,44 routes the call. Although this is not generally within the scope of the OMC's function, it highlights the fact that the inventive concepts of the present invention can be implemented in any number of ways. Alternatively, the BSS may make the decision, if it is provided with at least one of the call barring/call routing rules.

It is also within the contemplation of the invention that the call barring/call routing rules may be distributed throughout the infrastructure, for example date and time related rules could be organized at the BSS level, whereas location or caller identification rules may be performed at say, the MSC 42,44 level.

In the context of the present invention, a location area management scheme locates MSs within the system. The location management scheme may incorporate such technologies as the global positioning system (GPS), to pin-point the location of any particular MS 12-16.

It is within the contemplation of the invention that alternative radio communication architectures could benefit from the inventive concepts described herein.

Turning now to FIG. 2, a conventional cell plan 162 containing interconnected cell areas 164-173 is shown.

Each cell area has a base station sub-system (BSS) 174- 187 with MSs 192-197 respectively affiliated therewith, shown via communication links 188,190.

Generally, as will be understood by persons skilled in the art, a MS is in communication with its nearest BTS (which together with the BSC forms the BSS) ; one example of this relationship is shown in relation to BSS 174 and mobile station 196 of cell 165.

MS 197 is shown having chosen cell 164 as the cell it currently wants to be associated with, namely the cell that the MS has'camped on'. This cell selection is usually based on signal strength and/or signal quality indications determined by monitoring broadcast channel transmissions sent from the BSS of each cell, in this case BSS 178.

Once camped on cell 164, MS 197 will transmit a location update message to the BSS 178 of that particular cell 164. The BSS 178 of the cell 164 reports this location information back into the network to its attached MSC.

The MSC is usually associated with a VLR database, as shown in FIG. 1. This VLR database is a set of temporary records holding information on the MSs camped onto cells under its jurisdiction. When MS 197 camps onto cell 164, the associated MSC/VLR copies the data record for MS 197 into its respective VLR, to enable call to be routed successfully to MS 197. The VLR also holds the paging group (group of cells) which cells are typically paged to determine the current cell location of the MS 12-16. It is within the contemplation of the invention that the call delivery rule (s) for a particular MS may also be transferred during this process.

In operation, MS 197 has initiated a delivery rule set up with the MSC (not shown) supporting the cell coverage area 162. MS 196 has initiated a call to MS 197. The call-delivery rule (s) may cause the call to be rejected, based on, for example: (i) a caller identification (ID) of the MS 196 (for example if it is a work colleague), or (ii) MS 197's location, shown here as being in a church 199, or (iii) with regard to the time/day, for example if it is a Sunday.

It is clearly within the contemplation of the invention that the call request could emanate from a fixed phone line. The MSC associated with cell 164 interrogates the VLR to determine the paging group, and any associated delivery rule.

An alternative example of a rule would be when the subscriber is with a client/customer calls from the office are routed through, whereas calls from friends or other (perhaps competing) client/customers are not.

Alternatively, if there is no rule that is relevant to the present call request, the MSC may send a paging message to each cell in the paging group. The MS 197 would receive the page message from the cell it is camped on, to which it may reply in the standard manner and completion of the call set up then carried out.

Turning now to FIG. 3, there is shown a block diagram of a MS 200 adapted to support the inventive concepts of the preferred embodiments of the present invention. The MS 200 contains an antenna 202 preferably coupled to a duplex filter or circulator 204 that provides isolation between receive and transmit chains within the MS 200.

The receiver chain, as known in the art, includes scanning receiver front-end circuitry 206 (effectively providing reception, filtering and intermediate or base- band frequency conversion). The scanning front-end circuit is serially coupled to a signal processing function 208.

An output from the signal processing function is provided to a suitable output device 210, such as a screen or flat panel display.

The receiver chain also includes received signal strength indicator (RSSI) circuitry 212, which in turn is coupled to a controller 214 for maintaining overall subscriber unit control. The controller 214 is also coupled to the scanning receiver front-end circuitry 206 and the signal processing function 208 (generally realised by a DSP).

The controller 214 may therefore receive bit error rate (BER) or frame error rate (FER) data from recovered information. The controller is also coupled to a memory device 216 that stores operating regimes, such as decoding/encoding functions and the like, and data relating to a monitored list of suitable neighbouring cell sites. A timer 218 is typically coupled to the controller 214 to control the timing of operations (transmission or reception of time-dependent signals) within the MS 200, particularly in TDMA units.

As regards the transmit chain, this essentially includes an input device 220, such as a keypad, coupled in series through transmitter/modulation circuitry 222 and a power amplifier 224 to the antenna 202. The transmitter/modulation circuitry 222 and the power amplifier 224 are operationally responsive to the controller.

Of course, the various components within the MS 200 can be realised in discrete or integrated component form, with an ultimate structure therefore being merely an arbitrary selection.

In accordance with the preferred embodiment of the invention, the signal processing function 208, memory device 216, input device 220 and display unit have been adapted to receive, store and transmit to the infrastructure, call-delivery rule (s) associated with the MS 200.

It is within the contemplation of the invention that the MS user is able to select pre-defined topics such as location, time, day, caller identification, etc. and incorporate their particular rule requirements based on these pre-defined topics. Furthermore, the user may decide to incorporate a subject matter category for classifying incoming calls, such as business calls, personal calls and/or general information calls.

All call-delivery rule (s) entered on the MS 200 via input device 220 are preferably stored in memory device 216, and are therefore available for modification at a later date by displaying on the display screen. The user of MS 200 can select when to transmit the rules to its serving BTS.

Turning now to FIG. 4, a flowchart of a call-delivery mechanism in accordance with a preferred embodiment of the present invention is shown. The flowchart includes

the steps of a communication unit 197,200 initiating at least one call-delivery rule, as shown in step 400. The rule (s) is/are then transferred via a MSC 42,44 from the communication unit 197,200 to the HLR 80 within the communication system, as shown in step 402.

When the MSC 42,44 receives a call request to set up a communication with the communication unit 197,200, as in step 404, the MSC 42,44 interrogates a parameter associated with the call request, such as caller ID, dat/time of call, etc. as shown in step 408. The MSC also interrogates each of the communication unit's 197, 200 call-delivery rule (s), as in step 406, to determine whether to deliver a call to said communication unit 197, 200, based on said delivery rule (s), as shown in step 410.

If there is no rule affected by the call, or the rule permits the call to proceed, the call is delivered, as shown in step 412. If the rule dictates that the call should not be delivered to the communication unit, an alternative mechanism is applied, such as re-directing the call to an answer phone, or providing an"out-of- range"or"unable to connect"return voice message, etc.

It is within the contemplation of the invention that processing of the delivery rules can be implemented in software, firmware or hardware, with the function being implemented in a software processor (or indeed a digital signal processor (DSP)) merely a preferred option.

It is also within the contemplation of the invention that said rules may incorporate alternative delivery mechanism, for particular calls. One example would be for the communication system to recognise, from at least one call-delivery rule, that a call originated from the user's work place. In response to such a determination, the system would route the call to say, a home-based answer phone.

It is within the contemplation of the invention that the MS could have some or all of its rules built in. This would help reduce air interface activity, and may simplify and localise the procedure. Alternatively, it may be deemed that in any particular instance that there is more advantage to having fixed network, for example a PSTN, or an IP nodes, performing some or all of the rules. The advantage of performing some or all of the rules in further up in the infrastructure, by catching the rule based barring nearer to a fixed terminal, reduces the network resource involved in the to-be-barred call.

It will be understood that the aforementioned communication system, communication unit and method for routing a call in a communication system, in particular call screening based on subscriber location, provide at least the following advantages: (i) significantly improved customer satisfaction with the s double glazing sales people and calls from work when, say, on the golf-course;

(ii) the subscriber no longer needs to interact personally with the system to screen calls at the point of ringing as many unwanted calls are barred before ringing occurs; and (iii) better use of the radio frequency, or network, resource and the communication link between the MSCs, BSCs and BTSs, such that only calls that the MS user wants to receive, are ultimately transmitted over the air.

Thus a communication system, a communication unit and method of call routing has been provided, particularly with respect to call screening based on subscriber location, wherein at least some of the aforementioned disadvantages of the prior art have been alleviated.